Compensatory Angiogenesis and Tumor Refractoriness

Prof. Rajesh N GaccheTumor Biology Laboratory, School of Life Sciences

SRTM Univeristy, Nanded, India (MS)

Angiogenesis is the formation of new blood vessels from

preexisting one

Structure of vessels and capillaries

Monocellular layer of endothelial cellsSmall artery:

Capillary: endothelial cell, basal lamina, pericytes

Angiogenesis is regulated by endogenous activators and Inhibitors

Anti-Angiogenic factors

Normal angiogenesis

Pro-Angiogenic factors

Anti-Angiogenic factors

Excessive angiogenesis

Pro-Angiogenic factors

Anti-Angiogenic factors

Normal angiogenesis

Pro-Angiogenic factors

Anti-Angiogenic factors

Insufficient angiogenesis

MMPs(Matrix

Metallo-Proteinases)

VEGF, FGF, PGF, IGF,

Angp, EGF, HGF, HIF, TGF, IL-3, IL-8, Ang

VEGF, FGF, PGDF, PGF, IGF, Angp,

EGF, HGF, HIF, TGF, TNF, IL-3, IL-8, Ang

VEGF, PGF, HIF-1

1. Activation2. Basement membrane

degradation

3. Migration

4. Differentiation

/ Proliferation /

Tube formation

5. Stabilization / Maturation

VEGF,PGDF,IGF, Angp

Tumor

Cytokines, FGF

Induce Expression of

VEGF

IL-1, IL-6Regulate

Process of Tumor Angiogenesis

VEGFR-FamilyFGFR PDGFR

PLCγ

IP3

NOSIII

NO

Vasodilation/ Permeability

DAG

PKC

Cell Proliferation

SHC

FAK

Paxillin

Cell Migration

PI3K

Cell Survival

PI3K

RhoAVav2

Vav1

Actin, Stress fibres &

Adhesion

Rac1

Por1 Por2

Lamellipodia/ Filopoda Formation

CDC42

N-WASP

A n g i o g e n e s i s

PI3K

PIP2

PIP3

PIP2 BADCaspase 9

Tie2/Tek

PLCγPIP3

RAS

cRAF

MEK 1/2

ERK 1/2

IP3

CamK II

PI3K

AKT

Path

way

RAS

CDC42RAC1

Regulation ofCytoskeleton

c-MET

VEGF-Family

CDC4

2 Pa

thw

ay

RAC

1 Pa

thw

ay

AKT

Path

way

FGF Ang-1,2,3

PDGFHGF

XL880,TAK-701,

RelotumumabBrivanib,

Nintedanib,Pentosan- polysulfate

Avastin , Aflibercept, Pegaptanib, Pazopanib,

Ranibizumab, Sunitinib

Sorafenib

Regorafenib, Ponatinib

• 3D structural information of angiogenic proteins has profoundly influenced the philosophy of drug design and development.

• There have been major and striking advances in protein crystallography.

• Structures solved by protein crystallography are exceptionally valuable and forms foundation for effective ligand design.

• Structural knowledge can be effectively utilized in developing better therapeutic agents for modulation of angiogenesis in cancer therapy.

Targeting Tumor Angiogenesis for designing novel drugs

VEGF-B

VEGFR-1

VEGF-C

VEGFR-2

These interactions have opened novel therapeutic avenues to study the role of VEGFR-1-specific ligand in angiogenesis-mediated pathologies.

These interactions have opened novel therapeutic avenues to study the role of VEGFR-1-specific ligand in angiogenesis-mediated pathologies.

Thesecontacts can be utilized in generating peptide mimetic inhibitormolecules that can modulate VEGF-C interaction with VEGFR-2

Thesecontacts can be utilized in generating peptide mimetic inhibitormolecules that can modulate VEGF-C interaction with VEGFR-2

Hydrogen bonds

Hydrophobic contacts

Interactions at interface of FGF-1::FGFR opens new avenues for rational drug design targeting FGF1-induced angiogenesisand cell proliferation.

Interactions at interface of FGF-1::FGFR opens new avenues for rational drug design targeting FGF1-induced angiogenesisand cell proliferation.

FGFR

FGF-2

FGFR

FGF-1

These interactions provide astructural insight to design therapeutic agents that can target FGF-2::FGFR interactions.

These interactions provide astructural insight to design therapeutic agents that can target FGF-2::FGFR interactions.

These interactions hold a key to design strategy for modulation of PGF-VEGFR-1 interaction.

These interactions hold a key to design strategy for modulation of PGF-VEGFR-1 interaction.

Such biochemical communications can be efficiently utilized to modulatePGDF β-receptor interaction in therapeutic context.

Such biochemical communications can be efficiently utilized to modulatePGDF β-receptor interaction in therapeutic context.

PGDFR

PGDF- β

VEGFR-1

PGF

These contacts at ATP binding site can be utilized to develop therapeutically relevant agents targeting Tie2K activity.

These contacts at ATP binding site can be utilized to develop therapeutically relevant agents targeting Tie2K activity.

Interactions at IGFBP and IGF can guide development of interaction based inhibitors.

Interactions at IGFBP and IGF can guide development of interaction based inhibitors.

IGF

IGFBP

Tie2K

These interactions at HGF::c-Met thus provide an opportunity to selectivelymodulate HGF activity as antagonist for cancer therapy.

These interactions at HGF::c-Met thus provide an opportunity to selectivelymodulate HGF activity as antagonist for cancer therapy.

Biochemical interactions at EGF::EGFR interface possess enormous potential to develop contact based therapeutic agents.

Biochemical interactions at EGF::EGFR interface possess enormous potential to develop contact based therapeutic agents.

EGF

EGFR

HGF

C-Met

All these interactions at TGF::EGFR possess lot of potential to betherapeutically targeted.

All these interactions at TGF::EGFR possess lot of potential to betherapeutically targeted.

Interactions at HIF-CBP complex can be extensively used to developsmall molecule transcriptional modulators.

Interactions at HIF-CBP complex can be extensively used to developsmall molecule transcriptional modulators.

HIF

CBP

More about structural opportunities for developing anti-angiogenic agents

Drugs FDA Approval Improvementin PFS (Months)

Improvementin OS (Months)

Bevacizumab metastatic colorectal cancer (withchemotherapy)

4.4 4.7

metastatic nonsquamous NSCLC(with chemotherapy)

1.7 2.0

advanced cervical cancer (withchemotherapy)

2.3 3.7

Sunitinib metastatic RCC (Renal cell carcinoma) 6 4.6Sorafenib metastatic RCC 2.7 NSPazopanib metastatic RCC 5 NAVandetanib advanced medullary thyroid cancer 6.2 NAAxitinib advanced RCC 2 NARegorafenib chemorefractory metastatic colorectal

cancer0.2 1.4

Aflibercept chemorefractory metastatic colorectalcancer

2.2 1.4

Cabozantinib advanced medullary thyroid cancer 7.2 NSRamucirumab metastatic gastric and GEJ cancers 0.8 1.4Source: Rakesh Jain, Cancer Cell 26, November 10, 2014

Clinical Research in Angiogenesis Inhibitors

as on 1st Nov 2015

• 3512 Clinical trials are registered• 1445 Trials have been completed (41 %) • 356 Trials have been Terminated (10 %)• 89 Trials have been withdrawn (2.5 %)• 14 Trials have been suspended (0.4 %)

Source: Clinical Trials.gov

Arguments ?• Targeting Tumor Angiogenesis: a Right target or

a Wrong Choice ?• Why the tumors growth is more aggressive after

drug holidays ?• Why there is evolving drugs resistance towards

anti-angiogenic agents ?

• Does the compensatory angiogenic mechanisms is the major factors in limiting the efficacy of anti-angiogenic therapy ?

Targeting tumor angiogenesis: an attractive target with emerging

challenges

Pathophysiological point of view

• Without neovascularisation

No tumor growth beyond a size of 2 mm No metastasis

pharmacological point of view

How will you supply an anti-cancer drugs

to the tumor without an

appropriate blood supply?

Targeting Angiogenesis: Right target or a Wrong Choice ?

‘Normalization of tumor vasculature’: a new paradigm by Prof. Rakesh Jain

• Blood vessels of tumor are more complex, dilated, tortuous, hyperpermeable and disorganized

• This makes the access of drug molecules difficult to reach every cell of tumor body.

• Instead of killing the entire tumor vessels, it is imperative to normalize (organized vessel complex) it initially?

• Appropriate doses of anti-antiangiogenic drugs has been shown to normalize the vessels.

Appropriate doses of anti-antiangiogenic drugs has been shown to normalize the vessels.

Goel S et al. Physiol Rev 2011;91:1071-1121

Inbuilt threats of targeting tumor angiogenesis

• At present anti-angiogenic agents can not discriminate between physiological and pathological angiogenesis.

• Hence, hampers normal angiogenesis.• Anti-angiogenic agents lack efficacy due to

prevalence of compensatory angiogenesis pathways.

• Off-target toxicities unrelated to blockade of physiological angiogenesis………another big issue!!

Conspiracy of Compensatory Angiogenesis in acquired drug resistance

• A. VEGF dependent • B. VEGF independent:

– FGF, PDGF, Angiopetins, Ephrins etc– DLL4-Notch Signalling C. Myeoloid & Stromal/Tumor Cell

mediated angiogenic reprogramming.D. Angiogenesis independent remodeling

mechanisms like vascular mimicry, vessel cooption and in intussusceptive angiogenesis

Source: Gacche RN, 2015,Oncogenesis (Nature)

VEGF-axis dependent and non-VEGF mediated mechanisms of resistance to anti-angiogenic therapies

Source: Gacche RN, 2015,Oncogenesis (Nature)

VEGFR-2

A n g i o g e n e s i s

VEG

F – A

Sig

nalin

g

VEGFR-3

Avastin

VEG

F-A

VEG

F-D

VEGF-A By pass

Proteolytic cleavage

VEGFR-3 Sustained

Angiogenesis in VEGFR-2 Inhibition

State

VEG

F -C

PlG

F

FGFR

FG

FR

Sig

nalin

g

FGF

Synergistic activity

Synergistic Inhibition

DLL-4

NOTCH

NO

TC

H S

ign

alin

g

Up regulate

anti-angiogenic resistance in VEGFA targeted therapies

Endothelial cell

VEGF bypass pathways

Source: Gacche RN, 2015,Oncogenesis (Nature)

Source: Gacche RN, 2015,Oncogenesis (Nature)

Source: Gacche RN, 2015,Oncogenesis (Nature)

Conclusions• Based on the present clinical and

epidemiological literature it is clear that the future settings of targeting tumor angiogenesis should customize more on inhibiting the compensatory angiogenic pathways/factors so as to improve the efficacy of anti-angiogenic agents.

• Developing anti-tumor agents hitting multiple targets are more appreciated in the midst of evolving resistance of cancer cells towards present day anticancer drugs

In silico work of di-, tri-, tetra-, and penta-hydroxy substituted flavones

Quantum chemical descriptors

NandedThank you