sorafenib and quinacrine target anti-apoptotic protein mcl ... · 15/06/2016 · 1 title:...

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Title: Sorafenib and quinacrine target anti-apoptotic protein Mcl-1: a poor prognostic marker in anaplastic thyroid cancer (ATC)

Authors: Junaid Abdulghani1, 2, Prashanth Gokare1, 2, Jean-Nicolas Gallant1, David Dicker1,2, Tiffany Whitcomb3, Timothy Cooper3, Jiangang Liao4, Jonathan Derr5, Jing Liu6, David Goldenberg5, Niklas K. Finnberg1, 2* and Wafik S. El-Deiry1, 2* Affiliations: 1Penn State Hershey Cancer Institute, Penn State Hershey Medical Center, 500 University Dr, Hershey, PA 17033 2Laboratory of Translational Oncology and Experimental Cancer Therapeutics, Department of Medical Oncology and Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111 3Department of Comparative Medicine, Penn State Hershey Medical Center, 500 University Dr. Hershey, PA 17033. 4Department of Public Health Sciences, Penn State Hershey Medical Center, 500 University Dr. Hershey, PA 17033 5Department of Surgery; Division of Otolaryngology-Head and Neck Surgery, Penn State Hershey Medical Center, 500 University Dr. Hershey, PA 17033. 6Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at Houston Medical School, Houston, Texas, USA *Corresponding authors: [email protected]; [email protected] Running Title: Quinacrine + Sorafenib in Anaplastic Thyroid Cancer Disclosure of Potential Conflicts of Interest: No potential conflicts of interest are disclosed by the authors. One Sentence Summary: The drug combination of sorafenib and quinacrine targets Mcl-1 and triggers synergistic responses in difficult to treat anaplastic thyroid cancer cells thereby potentially offering a novel therapy combination for further testing in the clinic. Abbreviations: ATC, Anaplastic Thyroid Cancer; ATCC, American Type Culture Collection; CI, combination index; FDA, United States Food and Drug Administration; FFPE, Formalin Fixed Paraffin Embedded; GI, gastrointestinal; IC50, concentration that causes 50% cell growth inhibition; ip, intraperitoneal; GSEA, Gene set enrichment analysis; Mcl-1, myeloid cell leukemia sequence 1; NFκB, nuclear factor kappa B; NIR, near-infrared; NT, non-neoplastic thyroid; OS, overall survival; Q, quinacrine; S, sorafenib; S/Q, sorafenib/quinacrine; TI, therapeutic index; STAT, Signal Transducer and Activator of Transcription; VEGF, vascular endothelial growth factor.

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Translational Relevance

Anaplastic thyroid carcinoma (ATC) is a fatal cancer with a median survival of 3-5 months after

diagnosis. The FDA approval of multi-kinase inhibitor sorafenib for late stage metastatic

differentiated thyroid cancer has opened newer avenues for targeting ATC BRAF mutations

occur in a quarter of ATCs. Quinacrine, an inexpensive drug with a well-known safety profile,

inhibits NFκB signaling and shows anti-cancer activity in preclinical studies. We demonstrate

that quinacrine acts additively/synergistically on ATC cells in combination with sorafenib in

vitro and confers improved survival in an orthotopic mouse model. The drug combination

inhibits NFκB and the expression of the anti-apoptotic molecule Mcl-1, both of which we show

are overexpressed in clinical ATC specimens. The drug combination show minimal toxicity

compared to current standard of care treatment. Our data indicates sorafenib and quinacrine

combination may have potential clinical implication in ATC management and should be further

tested in clinical trials.




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Abstract

Purpose & Experimental Design: Anaplastic thyroid cancer (ATC) comprises ~2% of all

thyroid cancers and its median survival rate remains poor. It is responsible for more than one-

third of thyroid cancer-related deaths. ATC is frequently resistant to conventional therapy and

NFκB-signaling has been proposed to be a feature of the disease. We aimed to assess the activity

of the anti-malaria drug quinacrine known to target NFκB-signaling in combination with the

clinically relevant kinase inhibitor sorafenib in ATC cells. The presence of NFκB-p65/RelA and

its target Mcl-1 was demonstrated in ATC by meta-data gene set enrichment analysis and

immunohistochemistry (IHC). We assessed the responses of a panel of human ATC cell lines to

quinacrine and sorafenib in vitro and in vivo. Results: We detected increased expression of

NFκB-p65/RelA and Mcl-1 in the nucleus of a subset of ATC compared to non-neoplastic

thyroid. ATC-cells were found to respond with additive/synergistic tumor cell-killing to the

combination of sorafenib plus quinacrine in vitro and the drug combination improves survival of

immunodeficient mice injected orthotopically with ATC-cells as compared to mice administered

either compound alone or doxorubicin. We also demonstrate that the combination of sorafenib

and quinacrine is well tolerated in mice. At the molecular level, quinacrine and sorafenib

inhibited expression of the pro-survival gene Mcl-1, pStat3 and dampened NFκB signaling.

Conclusion: The combination of quinacrine and sorafenib targets emerging molecular hallmarks

of ATC and shows promising results in clinically relevant models for the disease. Further testing

of sorafenib plus quinacrine can be conducted in ATC patients.

Key Words: Thyroid Cancer; Sorafenib; Quinacrine; Mcl-1




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Introduction Anaplastic thyroid cancer (ATC) is a rare but highly aggressive form of thyroid cancer with a

median survival of 3-5 months that remains unchanged despite increased understanding of the

etiology of the disease (1). Unfortunately, refractoriness to chemo- and radio-therapy is a

common feature and development of novel therapeutics is essential to improve the prognosis of

ATC patients. Recent insight into genetic lesions that drive the progression of ATC may help

shape concepts of novel strategies of targeted therapeutic approaches. Currently, the proto-

oncogenes RET, RAS and BRAF are some of the best described targets in thyroid cancer (2, 3)

and specifically activating BRAF V600E mutations have been reported to occur in approximately

25% of ATCs (4, 5).

Given the frequency of activating mutations of the BRAF oncogene in ATC it is perhaps

not surprising that the multi-kinase inhibitor Sorafenib (Nexavar®), an approved drug for the

treatment of advanced renal carcinoma (6), unresectable hepatocellular carcinoma (7) and

progressive radioactive iodine-refractory differentiated thyroid carcinoma (8), has sparked

clinical interest in ATC. Sorafenib targets BRAF and CRAF, in addition to several other tyrosine

kinases, suggesting that at least a subpopulation of ATC patients might respond to sorafenib.

However, sorafenib has shown limited activity in the reported clinical trials of ATC to date (9,

10). One phase-II study of sorafenib in patients with advanced ATC indicated activity but at low

frequency in a similar manner as fosbretabulin, a vascular disrupting agent (10). It is becoming

increasingly clear that sorafenib may trigger toxicities in thyroid cancer patients that frequently

result in dose reduction (11). Thus, treatment with sorafenib alone may be insufficient to evoke a

strong anti-tumor response in ATC patients and incorporation of additional targeted therapeutics

that exhibit low-toxicity into sorafenib-protocols may be required to improve outcome.




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Additional molecular changes occur in ATC cells that may contribute to disease aggressiveness

include aberrant activation of NFκB signaling. Imbalanced activation of NFκB may possibly

contribute to the treatment refractory pro-inflammatory and metastatic phenotype of ATC.

Indeed, the expression of RelA/p65 was found to be increased in ATC tissues compared to that

of normal thyroid (12). Several inhibitors of NFκB-signaling such as

dehydroxymethylepoxyquinomicin (DHMEQ), triptolide, imatinib and bortezomib have shown

promising results in pre-clinical experiments with ATC cells (13-16).

The acridine derivative Quinacrine, used historically for malaria treatment, is a potent

inhibitor of NFκB-signaling (17), and is currently being evaluated in phase-II cancer clinical

trials (18). Its extensive use during the Second World War by over three (3) million soldiers

makes it a well-studied drug with a safety profile based on extensive epidemiological data.

Moreover since quinacrine is currently used for the treatment of giardiasis or lupus and is very

affordable (~$30 USD/month of therapy), it is a good candidate compound for repositioning to

target malignancies with oncogenic activation of NFκB-signaling. We recently reported the

effectiveness of quinacrine with other standard-of-care therapies in liver and colon cancer (19,

20). Quinacrine was found to effectively target NFκB and inhibit Mcl-1 expression in colorectal

cancer cells. In addition, we have previously shown that sorafenib inhibits both JAK/STAT3-

and NFκB-signaling that also results in the downregulation of Mcl-1 (21, 22).

Herein, we show that quinacrine combines favorably with sorafenib in an additive to

synergistic manner and generates a strong anti-tumor response in an orthotopic mice model of

ATC without significant toxicity. Treating ATC cells with the sorafenib/quinacrine drug

combination dramatically reduced the levels of anti-apoptotic Mcl-1 and triggered Mcl-1-

dependent cell death. Mcl-1 protein is overexpressed in a subset of ATC patient specimens




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compared to non-neoplastic thyroid. Furthermore gene set enrichment analysis of meta-data

indicates hyperactivation of NFκB-signaling in ATCs. These findings provide a rationale for

future clinical trials of the drug combination quinacrine/sorafenib in aggressive thyroid cancers.




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Material and Methods Detailed Materials and Methods are provided as Supplementary Information

Cell lines and reagents

These were as described previously (21).

Immunohistochemistry of clinical normal and anaplastic thyroid cancer (ATC) Twelve ATC’s and ten ‘normal’ (non-neoplastic) thyroid patient formalin-fixed paraffin

embedded (FFPE) tissue specimens were obtained from the Department of Pathology’s tissue

bank/Penn State Hershey Cancer Institute. The following antibodies were used for

immunohistochemical detection anti-phosphotyrosine-Stat3 (Y705), anti-NFκB-p65 and anti-

Mcl-1. Slides were scored and the expression parameters were correlated with clinical outcome.

Meta-analysis of NFκB-dependent gene expression in clinical ATC’s

Gene expression data were collected through Oncomine™/Gene Expression Omnibus (GEO)

and previously published reports containing complete curated expression profiles of resected

clinical specimens of indicated tissues. The gene expression profiles were computationally

analyzed for statistically significant differences with respect to the expression of four (4) gene

sets of putative NFκB-target genes using the Gene Set Enrichment Analysis (GSEA)

(http://www.broadinstitute.org/gsea/index.jsp) (23) .

Quantitative RT-PCR Total RNA was extracted using the RNeasy Mini Kit and converted to cDNA using the First

Strand Synthesis kit. For qPCR analysis the SYBR select master mix was used together with the

primers for Mcl-1, Stat 3, NFkappaB-p65/RelA.




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siRNA knockdown experiments and dose response for sorafenib and quinacrine

The siGENOME Non-Targeting siRNA #1 and Mcl-1 were transfected and cells were collected

for dose response CellTiter-Glo™ assay. The same batch of cells was plated for measuring

knockdown efficiency of Mcl-1.

Immunoblotting These are as described previously (21).

Sub-G1 and cell survival analysis These are as described previously (21)

Mouse orthotopic xenograft model of ATC A midline cervical incision was made and the underlying submandibular glands were retracted

laterally. Gentle retraction of the midline strap muscles was performed to reveal the thyroid

glands adjacent to the trachea and visible underneath a deep layer of semitransparent strap

muscles. Direct injection of the thyroid was done, the submandibular glands were returned to the

original location and the skin closed in a single layer (24). Mice were treated with sorafenib,

Doxorubicin and Quinacrine as previously described (21); and followed for tumor burden.

Immunohistochemistry of mouse tissues

Mouse FFPE sections were analyzed by IHC as described for clinical specimens above.

Antibodies were used for the detection of VEGF, CD34 and Ki67 are listed in supplementary

information. The detection of apoptotic cells were done by using the TUNEL-kit.




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Mouse dose-escalation toxicity study

C57BL6/J mice were injected with doses of quinacine (2 times) x 1 dose oral gavage, sorafenib

(5 times), whereas doxorubicin (2.5 times) of that used in the orthotopic model. At day seven (7)

mice were sacrificed, whole blood was isolated by cardiac puncture for hematology and serum

chemistry, and tissues were isolated for histological assessment.

Statistical analysis All comparisons were made relative to untreated controls, and statistically significant differences

are indicated as *p<0.05 and **p<0.005. We used Calcusyn software to determine synergy.

Overall survival was determined using Kaplan-Meier method. Cox multi-regression analysis was

performed on patient parameters relating to the ATC specimens stained by IHC for pStat3,

NFκB-p65 and Mcl-1.




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Results

A subset of ATC patients overexpress Mcl-1 mRNA and protein

Targeted therapy acts against specific molecules that are preferentially present in malignant cells

and required for cancer cell survival and growth. We have previously shown that both sorafenib

and quinacrine can target cell death signaling through modulation of NFκB- and JAK-STAT-

signaling in cancer cells (19-22). Although these pathways are frequently activated in cancer (25,

26), it has until recently been largely unknown to what extent these pathways are also aberrantly

activated in ATC. To address target availability in ATC we compared the expression of NFκB-

p65 (RelA), STAT3 and Mcl-1 mRNA in a panel of human cancer cell lines and resected ATC

specimens to that in ‘normal’ (non-neoplastic) thyroid by qRT-PCR (Supplemental Figure 1).

The genomic profile of the ATC cell lines used in our study have been established and verified

previously (27-29).

Detectable expression of Mcl-1, RelA and STAT3 mRNA was found in all five human

ATC cell lines tested (Supplemental Figure 1A) tested by qRT-PCR. Expression of Mcl-1 and

RelA varied from average to average-high in comparison to the prostate cancer cell lines and the

hepatoma cell line HepG2. Expression of STAT3 was variable among the ATC cells, and,

interestingly STAT3 mRNA was found underexpressed in the 16T and 21T cell lines. In general,

the mRNA expression levels of these oncogenes was lower in ATC cells than the expression

found in the untransformed fibroblast cell lines MRC5 and HFF (Supplemental Figure 1A),

only the prostate cancer cell line DU145 expressed more Mcl-1, RelA and STAT3 mRNA than

the fibroblasts. Thus, a certain level of variability with respect to expression of these genes is

present in ATC cells.




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In order to better address if expression of these genes may be upregulated by

carcinogenesis; we hypothesized that a better comparison would be between resected ATC and

non-neoplastic thyroid (Supplemental Figure 1B-D). We observed that the mRNA of Mcl-1 and

RelA were expressed in both normal thyroid and ATC tissues, although the sample size was

limited due to specimen availability. Interestingly, RelA was underexpressed at the mRNA level

in our samples whereas expression data from one ATC sample indicated that potentially a

subpopulation of ATC’s may express high levels of Mcl-1 mRNA (Supplemental Figure 1B).

However, STAT3 mRNA expression was low or unquantifiable in ATC in comparison to that in

normal thyroid tissue (Supplemental Figure 1D).

However, since both NFκB and JAK-STAT signaling can be significantly regulated at

the post-transcriptional level; we aimed to address this by assessing the protein expression in the

normal and ATC tissues. We performed IHC for NFκB-p65, Mcl-1 and phosphorylated (active)

STAT3 (STAT3pY) on resected formalin fixed paraffin embedded (FFPE) patient tissues. Our

initial analysis of the stained tissues did not reveal significantly different overall expression

(number of positive cells) of NFκB-p65 or STAT3pY between normal thyroid and ATC

(Supplemental Figure 2A and B). In fact, some normal thyroid tissues showed higher levels of

STAT3pY (Supplemental Figure 2B) consistent with our qPCR data showing lower expression

of STAT3 mRNA (Supplemental Figure 1D). STAT3pY staining was found predominantly in

vascular endothelial cells and occasionally in thyroid follicular cells (Supplemental Figure 2C).

Similar findings with respect to STAT3 have been reported and STAT3 has been proposed to

function as a tumor suppressor in thyroid tumorigenesis by suppressing HIF-1alpha-signaling,

aerobic glycolysis and tumor growth (30).




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We assessed if NFκB-p65 staining (in cytoplasm and nucleus) correlated with overall

survival (OS) in ATC patients. Neither ‘low’ (below median) nor ‘high’ (above median) overall

expression of NFκB-p65 correlated with OS (P=0.4936) (Supplemental Figure 3A). However,

in the case of NFκB-p65 we found that ATC cells would predominantly express NFκB-p65 in

the cytoplasm or nucleus and strong nuclear staining was only observed in ATC tissues (Fig.

1A). This finding is consistent with NFκB-p65/RelA being latent in the cytoplasm but

translocated into the nucleus to modulate transcription of target genes once activated. Thus, we

hypothesized that ATCs with aberrantly activated NFκB-signaling may show primarily nuclear

staining of NFκB-p65 as a consequence of activation (12). Four (4) out of eleven (11) ATC

patients were classified as having predominately nuclear staining for NFκB-p65 and showed an

overall poorer prognosis with median survival of 1.4 months compared to 7.9 months (hazard

ratio 7.8; 95% CI: 1.24 - 48.67) for patients with predominantly cytoplasmic staining (Fig. 1B).

Nuclear staining for NFκB-p65 was not the only predictor (nor independent) of survival. ATC

patients with ‘small’ tumors (greatest dimension <10 cm) and/or who were subjected to surgery

as part of their treatment had better OS as compared to patients who had ‘large’ tumors (greatest

dimension >10 cm) and who did not receive surgery (Supplemental Figure 3B and C).

Although tumor stage (IV-B vs. IV-C) showed a trend towards influencing OS it was not

statistically significant (P=0.0690) in the analyzed cohort (Supplemental Figure 3D). A

potential explanation for the latter finding may be that our cohort was of modest size even by

ATC standards and increased sample size would likely confirm tumor stage to prognosticate

survival.

ATCs appeared to stain more frequently for the NFκB target Mcl-1 compared to normal

thyroid tissue (Fig. 1C and D). Three (3) of four (4) ATCs with nuclear NFκB-p65 also had an




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expression (% Mcl-1+ cells) above group median (Fig. 1D). Furthermore, by Kaplan-Meier

estimates, we observed a trend where patients with ‘high’ (above median) Mcl-1 appeared to

have decreased OS compared to patients with ‘low’ (below median) Mcl-1 (Fig. 1E) although

this trend was not statistically significant when subjected to multivariate survival analysis using

Cox’s regression model (p=0.120).

In order to validate our findings with respect to increased NFκB-p65 activation in ATC

compared to normal thyroid tissue we performed meta-analysis of previously published gene

expression data on ATC. Three studies allowed us access to expression profiles for data mining

of a sufficiently large set of genes (31-33). Indeed, GSEA analysis of the expression profiles

previously published (33) revealed that normal thyroid and ATC separated in distinct phenotypic

expression profiles (Supplemental Figure 4A). We investigated if gene sets with activation of

NFκB-signaling were enriched in clinical ATC’s. Subsequently, we matched two gene sets

(HALLMARK_INFLAMMATORY_RESPONSES and TNF_SIGNALING_VIA_NFKB)

present in the molecular signatures database (MSigDB) with the expression profiles of normal

thyroid and ATC. Increased overlap between genes expressed in the ATC expression profile was

observed with both of the gene sets (FDR q<0.00001 and nominal P<0.01) (Fig. 2A and B). In

addition, we assessed if sets of genes containing the RelA annotation motif GGGAMTTYCC

within 2kb of their transcription start site were increasingly expressed in ATC. Such genes were

increasingly expressed in clinical ATC specimens compared to normal thyroid (FDR q<0.0001

and nominal P<0.01) (Fig. 2C). We performed GSEA-analysis for gene sets relating to NFκB-

activity for ATC-curated gene expression profiles published by Salvatore et al (32) and Hebrant

et al (31) (Supplemental Figure 4B and D). Although no enriched expression of NFκB-

dependent genes was found with statistical certainty (i.e., FDR q<0.25 and P<0.05) on the




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curated expression profiles, the ATC expression profiles from both studies contained a larger

number of genes linked to NFκB-activity than either normal thyroid tissues or papillary thyroid

cancers. We did not find Mcl-1 overexpression in ATC compared to neither normal thyroid

tissues nor papillary thyroid cancer (data not shown). By contrast, data from the established

expression profile from Hebrant et al (31) indicated reduced mRNA expression of Mcl-1

compared to normal tissues and papillary thyroid cancer (data not shown). Mcl-1 protein

expression has been shown to be regulated both at the transcriptional and post translational level

(34) and thus they may not always correlate in cancer.

Combined treatment with sorafenib and quinacrine triggers synergistic anti-tumor responses in

ATC cells

We have previously assessed sorafenib (S) and quinacrine (Q)-dependent targeting of the anti-

apoptotic protein Mcl-1 to sensitize tumor cells to programmed cell death (apoptosis). Targeting

of Mcl-1 by S and Q was previously shown by us to overcome TRAIL- and chemo-resistance in

cancer cells (19-22). We hypothesized that Mcl-1 may be a bonafide drug target in ATC.

Q and S displayed single agent anti-tumor activity in human ATC cells. Dose-response

relationships for S (Fig. 3A) and Q (Fig. 3B) were established in the ATC cell lines THJ-16T,

THJ-21T and THJ-29T (Table I). The THJ-16T cell line appeared to be significantly more

resistant to S compared to the THJ-21T and THJ-29T cell lines. By contrast, the same cell lines

showed smaller differences with respect to sensitivity to Q (Fig. 3B and Table I). The anti-

tumor response appeared to be at least partially explained by apoptosis in the ATC cell

population. Increased sub-G1 DNA was observed following short-term treatment with both S

(S10) and Q (Q20) alone (Fig. 3C). An additive effect was observed by the combination of S and




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Q (S10Q20). We further characterized the dose-response characteristics of the combination of S

and Q in THJ-29T and THJ-16T cells using the bioluminescent CellTiter-Glo™ cell survival

assay (Fig. 3D). A combinatorial effect (reduced fluorescence indicating reduced survival) was

observed with S and Q.. We assessed the nature of the S and Q combinatorial drug response in

the sorafenib-refractory ATC cell line THJ-16T. We used the theorem of Chou-Talalay (35) to

generate combination indices (CI) for the drug combination of S/Q in ATC (Fig. 3E). The best

outcome as judged by CI’s generated in our cell survival assay was ‘strong synergism’ indicating

that Q may sensitize sorafenib-refractory ATC cells to cell death. Taken together, our data

indicate that the drug combination S/Q triggers apoptosis and anti-tumor responses that are

synergistic in ATC cells.

Quinacrine potentiates sorafenib-dependent eradication of anti-apoptotic Mcl-1 in ATC-cells

We previously showed that treatment of 8505C with increasing concentrations of sorafenib (S)

that the drug ameliorates the expression of several pro-survival proteins (21). Among others,

phosphorylation of STAT3, MEK and ERK was inhibited. In addition, expression of pro-survival

protein Mcl-1, but not Bcl-XL, was inhibited by drug S. Western blot showed that low dose

treatment of 8505C cells with Q (1 µM) and S (0.3–3.2 µM) inhibits phosphorylation of STAT3

at the pro-survival phosphorylation site of Y705 (Fig. 4A). At higher doses the drug combination

triggers a robust pro-apoptotic response in 8505C cells associated with an essentially complete

eradication of Mcl-1 and full-length PARP (Fig. 4B). Expression of mutated p53 was not

affected by the drug combination in 8505C cells. Indeed, previous data showed that Q kills

cancer cells independent of p53 (20). Q and S/Q inhibited the expression of NFκB-p65 (RelA) in

8505C and THJ-16T cells (Fig. 4C) supporting the notion that the NFκB-pathway is a target in




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ATC cells. To functionally validate our findings with regards to p65/RelA and Stat3 expressions

we used siRNA to target p65/RelA and total Stat3 in 8505C cells prior to treatment with

sorafenib and quinacrine. Neither scrambled (Scr) siRNA nor siRNA targeting Stat3 had a

significant impact on the cell viability dose-response relationship of sorafenib or quinacrine in

8505C cells (Fig. 4F and G). However, targeting of p65/RelA caused an approximately 2-fold

increased sensitization of 8505C cells to sorafenib compared to cells subjected to treatment with

Scr siRNA (IC50: 5.15 µM; 95%CI: 4.14-6.41 µM and IC50: 10.49 µM, 95%CI: 7.56-14.5 µM

respectively) (Fig. 4F). SiRNA-dependent targeting of p65/RelA did not have any significant

impact on the survival dose-response relationship following treatment with quinacrine (Fig. 4G).

Thus, our western blot protein dataindicates that the drug combination of S/Q targets several pro-

survival pathways and the anti-apoptotic protein Mcl-1 in ATC cells in vitro. However, targeting

of NFκB signaling may in particular sensitize ATC cells to sorafenib perhaps indicating that

quinacrine may trigger synergism as a result of its capacity to target NFκB-dependent

transcription.

Targeting of Mcl-1 impacts the anti-tumor response to sorafenib but not quinacrine in ATC cells

To assess the extent to which Mcl-1 may be required for the therapeutic efficacy of the drug

combination S/Q we targeted the expression of Mcl-1 by siRNA gene silencing and assessed

how this impacted the dose-response characteristic of S and Q in 8505C cells (Fig. 5A-D).

Knockdown of Mcl-1 sensitized 8505C cells to S by 1.4-fold but did not affect the IC50 to Q

(Fig. 5C-E). Analyzing the combinatorial effect of S and Q in 8505C cells with and without

targeted Mcl-1 expression showed that intact Mcl-1 expression is required to produce a potent

combinatorial drug response. Synergism was observed at an ICS80/Q60 combinatorial dose whereas

ICS80/Q50 and ICS80/Q30 produced near additive effects in the 8505C cell line (Fig. 5F). By contrast,




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Mcl-1 knock-down produced an antagonistic relationship between S and Q at the corresponding

effective dose levels (Fig. 5G). We also found that Q synergistically sensitized 8505C cells to S

at a concentration as low as 125 nM (CI=0.88) and this drug synergism was ameliorated

completely by Mcl-1 depletion (CI=1.03) (data not shown). We propose a model where

quinacrine-dependent inhibition of Mcl-1 expression contributes to the combinatorial efficacy of

S/Q (Supplemental Figure 5). This may favor targeting ATC with high NFκB and Mcl-1.

Drug combination S/Q improves survival in a mouse orthotopic ATC model

To test the efficacy of drug combination S/Q in vivo we assessed to what extent ATC cells grew

as tumors in immunodeficient (Nu/Nu) mice. ATC cells were labeled with fluorescent cell

permeable dye CellVue® Maroon and injected orthotopically into recipient mice (Supplemental

Figure 6A). At one week following injection mice were subjected to NIR-imaging to visualize

fluorescently labeled ATC cells and document the extent of tumor growth. Nu/Nu mice are

significantly less sensitive to DNA damage compared to immunodeficient SCID mice that lack

the Ku70 subunit of DNA-PK, and thus were the preferred mouse model. Orthotopic models are

considered clinically more relevant compared to sub-cutaneous models and therefore we used an

orthotopic in vivo model (Supplemental Figure 6B). Injected mice developed tumors in their

thyroid gland within seven days and started to show lethargy at day 12 (Fig. 6A). Efforts to

assess tumor burden over time in these mice by non-invasive NIR-imaging proved to be difficult

as the thyroid is localized behind the salivary gland and so NIR-imaging was used as a post-

mortem imaging methodology to verify ATC tumor growth from labeled implanted cells (Fig.

6B, C and Supplemental Figure 6C). IHC data indicated the 8505C tumor xenograft had high

expression of Mcl-1 (Supplemental Figure 6D).




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Median survival for untreated mice was twenty-two (22) days (Table II). Although S, Q

and doxorubicin did increase median survival (26, 32 and 31 days respectively) these trends did

not reach statistical significance when compared to the median survival of untreated (control)

mice (Fig. 6D-F and Table II). These data are consistent with the clinical experience where

sorafenib and doxorubicin provide a limited impact on OS for ATC patients. By contrast, we

found the sorafenib and quinacrine (S/Q) combination significantly increases the survival of

mice carrying 8505C xenografts in their thyroid gland compared to untreated mice (median

survival 75.5 days, p=0.0138, Gehan-Breslow-Wilcoxon Test) (Fig. 6G and Table II). Analysis

of FFPE thyroid tumors indicated increased TUNEL-positivity and reduced expression of the

proliferation marker Ki-67 following treatment with the different modalities (Fig. 6H) (19). In

summary, although sorafenib, quinacrine and doxorubicin fail to produce a significant survival

advantage in this ATC orthotopic mouse model the combination of sorafenib and quinacrine

increases the median survival three (3)-fold compared to that of untreated (control) mice without

any apparent toxicity.

The combination of quinacrine and sorafenib shows limited toxicity in a mouse dose-escalation

study as compared to doxorubicin

Although the safety profiles for sorafenib and quinacrine are known in human subjects, the

potential for the drug combination to trigger toxicity in an additive/synergistic manner in vivo is

largely unknown. We addressed this through a short-term (7 days) dose-escalation study in mice

followed by a histopathological assessment and blood correlatives following treatment. No

lethality or lethargy was observed in the mice following exposure the super-therapeutic doses of

S, Q, doxorubicin and S/Q. However animals subjected to S/Q displayed a transient 15% weight




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loss nadir at day two (2) following initiation of treatment (data not shown). All of the S/Q-

treated animals recovered from this by day five (5). Analysis of serum chemistry and hematology

indicated no toxicity of S/Q compared to untreated (control) mice (Supplemental Figure 7 and

8). By contrast, mice subjected to treatment with the first-line chemotherapeutic doxorubicin

displayed a reduction in the number of RBC’s and hemoglobin (Hgb) compared to mice treated

with S/Q (Supplemental Figure 8B and C). Furthermore, doxorubicin-treated mice had an

increased level of platelets in their blood compared to control and S/Q-treated mice

(Supplemental Figure 8E). Histopathological evaluation of the bone marrow, gastrointestinal

(GI) tract, heart, pancreas, liver and kidney suggested that doxorubicin-treated mice more

frequently displayed signs of bone marrow and GI-toxicity than the other treatment groups

(Table III). Such signs included prominent congested sinusoids in the bone marrow and villous

blunting, crypt dilation, crypt hyperplasia and inflammation of lamina propria in the duodenum.

Although doxorubicin is known to cause cumulative-dose cardiotoxicity, we did not find any

histopathological evidence of this in our short-term study. Histopathological signs of toxicity

from the combination of S/Q were consistent with what was observed with treatment with either

compound alone and did not increase in severity following the combination (Table III and data

not shown). The only unique histopathological manifestation that we were able to link to S/Q

exposure was the appearance of a single small focal chronic cortical infarct with a volume of

<0.01% in the kidneys of two out of five (2/5) mice subjected to S/Q (Table III) which was not

frequent enough to be statistically significant. Thus, the S/Q combination is well-tolerated even

at doses that greatly exceed those used to evoke potent anti-tumor responses in vivo.




20

The drug combination of sorafenib and quinacrine inhibits the expression of angiogenesis

markers in mouse 8505C xenografts

Preclinical data indicates that targeting of tumor angiogenesis and VEGF-signaling can trigger

anti-tumor responses in models for ATC (36). Preclinical data and two (2) clinical case studies

also indicate that receptor tyrosine kinase (RTK) inhibitors that target VEGF-signaling may hold

promise for the treatment of ATC (37, 38). In order to address if the combination of sorafenib

and quinacrine have potential to modulate tumor angiogenesis we performed IHC for CD34 (a

marker for the presence of small vessel endothelium) and VEGF (a pro-angiogenic marker and

effector molecule) on FFPE sections from 8505C xenografts from Nu/Nu mice subjected to

treatment with S/Q (Fig. S9). The number of CD34-positive vessels was dramatically reduced by

S and the combination of S/Q (Fig. S9A and B). Moreover, S alone and in combination with Q

exhibited a potent inhibition of VEGF-expression in the tumor xenografts. These data are

consistent with sorafenib’s anti-angiogenic properties in addition to BRAF-targeting. Taken

together our data indicate that the combination of sorafenib and quinacrine inhibits angiogenesis

in addition to the targeting of anti-apoptotic molecules in ATC cells.

Discussion

Despite advances in understanding the molecular pathogenesis of ATC the disease remains

associated with a poor prognosis. Increased efforts are being undertaken to define “actionable”

genetic changes and develop improved treatment protocols. The multi-kinase inhibitor sorafenib

has shown promising results in some solid malignancies but data from recent ATC clinical trials

indicate that sorafenib has limited impact on overall survival in ATC (9, 10). Our studies show

that sorafenib combines favorably with quinacrine to trigger a combinatorial response in ATC to

significantly improve survival of mice implanted orthotopically with ATC cells relative to




21

untreated (control), single agent or doxorubicin-treated mice (Fig. 6). This S/Q drug combination

targets NFκB-p65 and Mcl-1 in vitro (Fig. 4 and 5). Both NFκB-p65 and Mcl-1 are

overexpressed in a subset of ATC’s (Fig. 1). Furthermore, mouse dose-escalation toxicology

data suggests that the S/Q drug combination is safe at the doses tested (Table III and

Supplemental Figure 7 and 8). Further assessment of the drug combination in animal models

for loco regional toxicities following radiation delivery to the head and neck may be necessary.

ATC patients frequently undergo radiotherapy and it is currently unknown if the drug

combination of S/Q would have a negative therapeutic index in this context. However, our

findings provide a foundation for evaluation of the S/Q drug combination in clinical trials.

Multiple aberrantly activated signal transduction pathways drive ATC pathogenesis

It is somewhat surprising that benefit from sorafenib is limited despite 25% of ATC’s showing

BRAF V600E mutations as sorafenib targets multiple pathways with activated tyrosine kinases

such as VEGFR and PDGFR-signaling (39, 40). This observation could be due to the fact ATCs

also show mutations in beta-catenin that generates hyperactivated Wnt-signaling (41) and that

ATC cells undergo EMT and show evidence of increased stemness compared to more

differentiated forms of thyroid cancer (42). EMT is associated with refractoriness to therapy and

more aggressive behavior in several other malignancies. Moreover, tumor suppressor p53 is

frequently lost and mutated in ATC and there is increased inflammatory NFκB-signaling and

enhanced activation of matrix metallo-proteinases (MMP-9) which may promote the

invasiveness of ATC (43, 44), features supported by our gene set enrichment analysis of meta-

data (Fig. 2 and Supplemental figure 4). It is therefore unlikely that targeting a single molecular

facet in ATC would yield a significant improvement of patient outcomes.




22

Interestingly, quinacrine is able to trigger anti-tumor responses independent of mutated

p53 through inhibition of NFκB and Mcl-1 (19, 20). Quinacrine can also synergize with the anti-

angiogenic drugs such as cediranib that targets VEGF-signaling (45) by blocking autophagy

triggered by receptor tyrosine kinase inhibitors suggesting that quinacrine can modulate the

activity of anti-angiogenic agents. Sorafenib displays anti-angiogenic activity in our in vivo

model and represses VEGF expression including when combined with quinacrine

(Supplemental Figure 9), unlike single agent quinacrine (Supplemental figure 9A-C). Thus

the combinatorial efficacy, multiple pathway targeting, safety and low expense of quinacrine

make the combination of sorafenib plus quinacrine an attractive option to further test in the clinic

as ATC treatment.

S/Q targets Mcl-1 an anti-apoptotic protein overexpressed in ATC

We have previously shown that quinacrine targets NFκB/RelA and anti-apoptotic Mcl-1 in

cancer cells (19, 20). Mcl-1 is an anti-apoptotic Bcl-2 family member and overexpression of

Mcl-1 negatively impacts the responses to some therapeutics in patients with malignancies such

as CLL (46). We show Mcl-1 is overexpressed in some ATC’s and expression is inhibited

through treatment with the drug combination of sorafenib and quinacrine in vitro (Fig. 1B, 1D,

1E and 4B). Quinacrine has previously been shown to inhibit the transcriptional activity of

NFκB/RelA and in addition to reactivate wild-type p53 in renal carcinoma cells (17). Quinacrine

can inhibit expression of NFκB-p65 (Fig. 4C). This may be of relevance since our IHC data

indicate that nuclear expression of NFκB-p65 is linked to poor prognosis in ATC patients (Fig.

1A and 1C). Three (3) out of four (4) ATC with ‘high’ Mcl-1 expression also showed nuclear

expression of NFκB-p65 (Fig. 1D). Mcl-1 is a downstream target gene of NFκB/RelA (47) but




23

we failed to substantiate significantly increased expression of Mcl-1 mRNA in clinical ATC’s

through data mining of expression profiles from previously published studies (31). However,

several studies indicate that expression of Mcl-1 protein is also regulated post-transcriptionally

and its mRNA/protein has a short half-life (34). It is possible that NFκB-p65 contributes to the

Mcl-1 mRNA pool and subsequent protein synthesis in ATC’s. Subsequently lesions with

nuclear NFκB-p65 may be selectively sensitive to quinacrine treatment. We hypothesize

quinacrine disrupts the expression of Mcl-1 through inhibition of NFκB/RelA.

We observed a trend suggesting a link between Mcl-1 overexpression, tumor size and OS

(Fig. 1E). Evidence suggests that apoptosis signaling indeed may be impaired in ATC. The

inhibitor of apoptosis protein (IAP) Survivin is overexpressed in ATC’s compared to papillary

thyroid cancers (31, 33) and Survivin expression has been proposed as a marker for

dedifferentiation in thyroid carcinogenesis (48). Interestingly, expression of anti-apoptotic Bcl-2

appears to be lost in ATC compared to well-differentiated papillary and poorly differentiated

thyroid cancers (49). . Mcl-1 overexpression has been documented in a number of solid tumors

and small molecule compounds targeting Mcl-1 directly are being developed for therapy, but the

role of Mcl-1 in ATC remains largely unclear. Mcl-1 shows limited background expression in

the follicular epithelium of normal thyroid (50) and Mcl-1 expression is frequently observed in

undifferentiated follicular and papillary tumors with low expression of Bax (51). Perhaps not

surprisingly indirect targeting of Mcl-1 with sorafenib, may sensitize ATC cells to stimuli that

trigger programmed cell death (21). In the absence of additional data it is tempting to speculate

that Mcl-1 may be linked to the pathogenesis of ATC and may represent a novel “actionable”

scaffold for targeted therapeutic intervention in a subset of ATC patients. Thus Mcl-1 may be a

bonafide target in ATC beyond the application of S/Q-treatment.




24

Expression of STAT3pY is downregulated in ATC In contrast to immunohistochemical data on prostate cancer (25), overexpression of STAT3pY

was not apparent in ATC-tissue (Supplemental figure 2B and C). At lease in some cases more

frequent staining for STAT3pY was seen in the non-neoplastic thyroid compared to ATC. ATC’s

may potentially also express lower levels of STAT3 mRNA compared to non-neoplastic thyroid

as evident from our qRT-PCR analysis (Supplemental figure 1D). As we had limited specimens

future studies should repeat this analysis with a bigger sample size.

STAT3 has been suggested to be a tumor suppressor in the thyroid since papillary thyroid

tumors that emerge in mice as a result of BRAFV600E mutation are significantly smaller when

they retained the STAT3 gene (30). The same study demonstrated an inverse correlation between

STAT3pY-expression, tumor size and metastasis. STAT3pY was frequently detected in

endothelial cells of papillary thyroid cancer which is consistent with what we observe in non-

neoplastic thyroid and ATC (Supplemental figure 2C and data not shown). It seems unlikely

that STAT3pY is a rate limiting therapeutic target in ATC. However, it may be plausible that the

S/Q drug combination targeting STAT3-signaling in the tumor vasculature of ATC’s may

contribute to the overall improved response observed in our orthotopic ATC model (Fig. 6).

Additional studies will have to address this therapeutic possibility more directly.

In summary, we show that the combination of sorafenib and quinacrine can trigger synergistic

Mcl-1-dependent drug responses in ATC cells in vitro. This combination appears to have limited

toxicity in mice and triggers potent anti-tumor responses in an orthotopic model for ATC. Based

on our data we propose that sorafenib and quinacrine should be explored as a therapeutic

modality for aggressive thyroid cancers in future clinical trials.




25

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Acknowledgments: The authors would like to thank Dr. Henry Crist, Trey Bruggeman and Dr. Nicole C. Williams in identifying suitable patient FFPE specimens for analysis and critiquing IHC staining of said specimens. This work was supported by grants to W.S.E-D; a grant from Thyroid Cancer Survivors Inc. (ThyCa) and the American Thyroid Association (ATA) to N.K.F. (Grant# 143317). W.S.E-D. is an American Cancer Society Research Professor.




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Tables Table I: Sorafenib and Quinacrine dose-response parameters for three (3) ATC cell lines

Sorafenib Quinacrine Cell line IC50 (µM) 95%CI R2 IC50 (µM) 95%CI R2 THJ-16T 31.00 19.32 to 49.75

0.9683

18.43

14.69 to 23.13

0.9732

THJ-21T 12.38 11.79 to 13.00

0.9939

15.39

13.84 to 17.11

0.9734

THJ-29T 4.497 3.812 to 5.304

0.9636

12.74

11.65 to 13.93

0.9808

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Table II: Survival parameters from the mouse ATC (8505C) orthotopic tumor model. Drug Median Survival (days) Hazard ratio1 95% CI P value1 Control 22 - - - Sorafenib (S) 26 0.846 0.317-2.25 0.202 (NS) Quinacrine (Q) 32 0.687 0.258-1.83 0.186 (NS) S/Q 75.5 0.2914 0.109-0.776 0.0138 (*) Doxorubicin 31 0.709 0.257-1.95 0.0791 (NS)

1Relative Control (untreated) mice

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Table III: Histological evidence of toxicity in mice following dose-escalation of sorafenib (S), quinacrine (Q), S/Q and doxorubicin.

aCharacterized by the appearance of prominent congested sinusoids bCharacterized by the appearance of villous blunting, crypt dilation, crypt hyperplasia, crypt abscesses and inflammation of lamina propria. cCharacterized in (V) by one case of focal segmental medial mineralization in a small mural coronary artery and one case of mineralized necrotic cardiomyocytes affecting <0.1% of the myocardium. In (Q), one case characterized by a nodule of large macrophages and few mast cells between the left ventricle and atrium. In (Q/S), one case displayed several mineralized necrotic cardiomyocytes affecting <0.1% of the myocardium. dCharacterized by the appearance of serositis of the pancreatic capsule; subacute or chronic, mild to moderate; necrotizing pancreatitis, subacute, minimal to moderate. This finding may be a result of the intra-peritoneal injection route of drug administration. eDiffuse, centrilobular, midzonal or peri-portal. fCharacterized by the appearance of one (1) small focal chronic cortical infarct with a volume of <0.01%. *P<0.05 (Chi-square test). **P<0.01 (Chi-square test).

Organ/tissue Vehicle (V) Quinacrine (Q) Sorafenib (S) Q/S Doxorubicin Bone marrowa, ** 0/5 (0) 0/4 (0) 0/5 (0) 0/5 (0) 3/5 (0.60) GIb, ** 0/5 (0) 0/4 (0) 0/5 (0) 0/5 (0) 4/5 (0.80) Heartc 2/5 (0.40) 1/5 (0.20) 0/5 (0) 1/5 (0.20) 0/5 (0) Pancreas d, ** 0/5 (0) 0/4 (0) 5/5 (1.00) 4/5 (0.80) 4/5 (0.80) Liver Vaculation 2/5 (0.40) 3/4 (0.75) 4/5 (0.80) 4/5 (0.80) 4/5 (0.80)

Glycogene 2/5 (0.40) 3/4 (0.75) 4/5 (0.80) 2/5 (0.40) 3/5 (0.60) Hydropic degeneration with basophilic stippling, centrilobular

0/5 (0) 2/4 (0.50) 0/5 (0) 2/5 (0.40) 0/5 (0)

Lipid, centrilobular 0/5 (0) 0/5 (0) 0/5 (0) 0/5 (0) 1/5 (0.20)Kupffer cell hyperplasia, centrilobular

0/5 (0) 0/5 (0) 0/5 (0) 0/5 (0) 1/5 (0.20)

Hepatocyte apoptosis, centrilobular

0/5 (0) 0/5 (0) 0/5 (0) 0/5 (0) 1/5 (0.20)

Kidneyf 0/5 (0) 0/5 (0) 0/5 (0) 2/5 (0.40) 0/4 (0)

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Figure legends

Figure 1: Nuclear NFκB-p65/RelA and Mcl-1 is overexpressed in anaplastic thyroid cancer

and may be associated with markers of poor prognosis. (A) IHC for NFκB-p65/RelA on

clinical FFPE non-neoplastic thyroid (NT) and anaplastic thyroid cancer (ATC) specimens. Each

panel shows a representative image of a unique individual patient sample with cytoplasmic

(Cyto.) and nuclear (Nuc.) expression of NFκB-p65/RelA in ATC or the expression of NFκB-

p65/RelA in non-neoplastic thyroid (NT) as detected by IHC. A 400x magnification is shown.

(B) Mcl-1 expression in clinical FFPE specimens of NT and ATC. Representative images are

shown. (C) Overall survival (OS) of ATC patients with nuclear (Nuc.) and cytoplasmic (Cyto.)

expression of NFκB-p65/RelA. The P-value was determined using the Log-rank test. (D)

Quantitation of FFPE immunohistochemistry for Mcl-1 in NT (N=11) and ATC tissues (N=11).

Medians are shown by black horizontal lines and each data point represents a stained specimen

from one patient. Tumors expressing Mcl-1 that had nuclear NFκB-p65/RelA are indicated. The

P-value was determined using the Mann-Whitney test. (E) OS of ATC patients in relation to the

expression levels of Mcl-1 in their tumors. A “low” and “high” expression level indicates

expression (% positive cells in the specimen) below or above the median respectively (as shown

in ‘B’). The P-value was determined using the Log-rank test.

Figure 2: Meta analysis of expression profiles from normal thyroid (NT) tissue and ATC. (A) Gene set enrichment analysis of clinical meta-data from Giordano et al (Giordano et al

2005). The GSEA analysis was performed for ATC (N=3) and NT (N=3). Gene set enrichment

was assessed for the MSigDB gene sets HALLMARK_INFLAMMATORY_RESPONSES (A),

HALLMARK_TNF_SIGNALING_VIA_NFKB (B) and N$YKAPPA (genes with RelA binding

sites within 2kb of their core promoter) (C).

Figure 3: Quinacrine and sorafenib synergize in the killing of ATC cells. Dose-response

curves for the 72-hr survival of ATC cell lines THJ-16T, THJ-21T and THJ-29T following

sorafenib (A) and quinacrine (B). The X-axis are shown as log scale. (C) Flow cytometric sub-

G1 programmed cell death (apoptosis) assay of the ATC cell line 8505C subjected to treatment

with sorafenib (S) and quinacrine (Q) and the combination (S/Q). Averages (N=3) +/- SEM are

shown. Statistical analysis was performed using Students t-test where P<0.05 was considered




statistically significant. Dose-response modulation of the combinatorial response of Q and S. (D)

Cell survival assay (CellTiter-Glo®) of ATC cells treated with different combinatorial

concentrations of Q and S. A representative figure of the result of a 72-hr Cell Titer-Glo® assay

for the ATC cell line THJ-29T is shown. (C) Combinatorial indices generated using the

CalcuSyn 2.0 software employing the method by Chou Talalay for S and Q in the sorafenib-

refractory ATC cell line THJ-16T. Red indicates ‘strong drug synergism’, blue – ‘drug

synergism’, green – ‘moderate drug synergism’.

Figure 4: Sorafenib (S) and quinacrine (Q) target the anti-apoptotic protein Mcl-1 in ATC cells. (A) Combination treatment with S and Q triggers inhibition of Stat3 phosphorylation

(Stat3PY) in 8505C cells. (B) The effect of S and Q on PARP cleavage, Mcl-1 and Stat3PY

expression in 8505C cells. (C) Western blot to analyze impact of S/Q on expression of NFκB-

p65/RelA in 8505C and THJ-16T cells. The doses of S and Q used were 10 and 20 µM

respectively. (D) Western blot analysis show efficient targeting of p65/RelA in 8505C ATC cells

by specific siRNA (p65) (left panel). No effect on p65/RelA is observed by siRNA-mediated

targeting of Stat3 (S3 [1+2]) (right panel). Scrambled (Scr) siRNA was used as a control for

specific targeting of p65/RelA and Actin was used as a loading control. (E) Western blot analysis

show efficient targeting of total Stat3 by two different siRNA (S3[1] and S3[2]) in 8505C cells.

A combination of both siRNA (S3[1+2]) was used to achieve efficient knock down of total Stat3.

Actin was used as a loading control. Sorafenib (F) and quinacrine (G) dose-response curves

following depletion of Stat3 and p65/RelA in 8505C cells using the CellTiter-Glo® assay. The

8505C cells were treated for 72 hrs with the drugs.Figure 5: Mcl-1 expression is required in ATC cells for combinatorial efficacy of the sorafenib (S) and quinacrine (Q). (A) Western

blot assessment of the efficacy of small interfering RNA (siRNA)-dependent targeting of Mcl-1

expression in 8505C cells. (B) CellTiter-Glo® cell survival assay. Sorafenib (C) and quinacrine

(D) dose-response curves in 8505C cells following siRNA mediated targeting of Mcl-1. The X-

axis are shown as log scale. (E) The observed IC50-values following S and Q treatment with and

without Mcl-1-targeting. Isobolograms for 8505C cells treated with various effective S and Q

concentrations (ICS80/Q30, ICS80/Q50 and ICS80/Q60) in the presence (F) and absence (G) of Mcl-1

knock-down.




Figure 6: The sorafenib (S) and quinacrine (Q) combination improves the survival of mice subjected to a thyroid orthotopic injection of ATC cells. (A) Live whole-body near-infrared

imaging (NIR) of whole mice (left panel) and tumor engraftment of 8505C cells in the thyroid of

a Nu/Nu mouse (right panel). (B) NIR-imaging of a Nu/Nu mouse subjected to thyroid

orthotopic injection of CellVue® NIR815-labeled 8505C cells after the removal of the salivary

gland. (C) NIR-imaging of a dissected and isolated tumor ATC-xeno-engrafted mouse (Nu/Nu)

thyroid. The injected 8505C cells were labeled with CellVue® NIR815-labeled Survival curves

of mice subjected to thyroid orthotopic injection of 8505C cells and subjected to no treatment

(Control) and sorafenib (D), quinacrine (E), doxorubicin (F) and the combination of S and Q

(G). (H) Immunohistochemistry for TUNEL (apoptosis) and Ki-67 (proliferating cells) on mouse

thyroid xenograft tumors of the ATC cell line 8505C. (I) Growth signals trigger constitutively

active NFκB signaling and Mcl-1 expression in ATC cells. Mcl-1 inhibits the activity of the pro-

apoptotic proteins Bak, Bid, Noxa and Bim. In addition, Mcl-1 may also influence cell cycle

progression and proliferation (not depicted). (J) Both S and Q inhibit NFκB activity and

ameliorate Mcl-1 expression. Selectivity of the compounds is achieved through increased activity

of NFκB in ATC’s. Reduced expression of Mcl-1 allows the pro-apoptotic proteins Bak, Bid,

Noxa and Bim to trigger cell death (apoptosis) and a therapeutically relevant anti-tumor response

in ATC.




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Published OnlineFirst June 15, 2016.Clin Cancer Res Junaid Abdulghani, Prashanth Gokare, Jean-Nicolas Gallant, et al. poor prognostic marker in anaplastic thyroid cancer (ATC)Sorafenib and quinacrine target anti-apoptotic protein Mcl-1: a

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