Possible Link between Cancer Multidrug Resistance and EpigeneticsErin Wildeman, Marcos Pires, PhD

Lehigh University Department of Chemistry, Bethlehem, PA 18015

Rationale• Cancer is a widespread disease, affecting over 1.5 million patients each year• Treatment of most cancers is heavily reliant on chemotherapeutic drugs• Most chemotherapeutic treatments often fail to eliminate 100% of the cancerous

cells from a patient’s body

- Some cancer patients experience a relapse

- The relapse tumor is usually more aggressive than the original tumor• Understanding why relapse tumors emerge more aggressively would allow cancer

therapies to be created that are more effective, increasing survival rates among

cancer patients

Background ContinuedHistones•Histones are a four protein complex (Two of each, H2A, H2B, H3, and H4) •DNA wraps around histone complex when condensing into its condensed chromosome structure

H3 Tail

Journal of Biological Chemistry, 9 April 2010, Volume 285, pages 11045-11050

Epigenetic Factors•“Heritable phenotypes resulting from changes in chromosomes without alterations in the primary

DNA sequence”•Types of Epigenetic Factors:

- Histone side-chain modifications (Methylation, phosphorylation, acetylation)

- Nucleosome placement

- DNA Methylation (cytosine)

•Epigenetic Modifications have been linked to several types of diseases including many types of

cancer•Normal cells have a fully methylated Lys on histone three (H3K4me3)

- In cancerous cells, H3K4 exists in the demethylated state (H3K4me2 or H3K4me1)

BBA-Reviews on Cancer, January 2011, Volume 1815, pages 75-89

PHD3 Domain•The RBP2 protein has a catalytic domain as well as three PHD domains •The PDH domain (Plant Homeodomain) is believed to be the “sensing domain”

•Research has proven that the PHD3 domain is critical for the function of RBP2•RBP2 protein lacking the PHD3 domain was unable to interact with Histone 3•RBP2 containing the PHD3 domain, when exposed to different H3 Lysine side chains, interacts most

strongly with H3K4

Nature, 11 June 2009, Volume 459, pages 847-851

Current ResearchOutline of Project:1.Express the PHD3 domain of RBP22.Synthesize peptides to mimic histone tail3.Measure binding affinity of PHD3 to different peptides

Current Status of Project:•PHD3 domain is expressing and has been successfully purified - Amplified PHD3 from plasmid containing the RBP2 gene using PCR - Cloned into pGEX-4T-1 vector, in frame with a GST tag - Transformed into BL-21 cells - Grew cells on ampicillin plates - Overnight Growth at 37 °C, induced with IPTG - Centrifuged, re-suspended cells in 1X PBS - Lysed cells via sonication - Purified protein on a glutathione column•SDS-PAGE from protein purification:

1.Synthesis of Polypeptide:2.Use solid state peptide synthesis to create a peptide that mimics the Histone 3 tail3.“Recent research suggests that the coexistence of modifications at nearby sites modulates the binding affinity of PHD fingers”4.Multiple different histone 3 tails will be synthesized, with a combination of different epigenetic modifications - Will be researching what modifications occur most commonly with Lysine 4

•Measure Binding Affinity of PHD3 Domain for Polypeptide

Future of Project:1.Little is currently known about how RBP2 functions2.We hope to better understand the combination of epigenetic modifications on histone 3 that code for effective binding of RBP2 3.Ultimate goal of project: Development an inhibitor for RBP2 - No pharmacological inhibitors have been developed yet for RBP2 - Inhibitor could improve outcome of cancer patients

Background InformationCancer Stem Cells•Small populations of cells from the original tumor can be converted to “Drug Tolerant

Persisters (DTPs)” or cancer stem cells•Characteristics of Cancer Stem Cells:

- Aggressive

- Resilient

- Self-renewal ability (tumor metastasis)

- Resistant to the chemotherapeutic drug originally used

Cell, 2 April 2010, Volume 141, Issue 1, Pages 69–80

RBP2•The protein RBP2 was found to be over expressed in cancer stem cells•RBP2 is a histone demethylase

- Specifically Lysine 4 on Histone 3 (H3K4)•Believed to be the protein responsible for the conversion of normal cancer cells to

cancer stem cells•In a knock-down experiment, the cells were unable to convert to the drug-tolerant

state

Cell, 2 April 2010, Volume 141, Issue 1, Pages 69–80

Plate 1= untreated Plate 2= treated for 9 days Plate 3= treated every 3 days for 33 days

DTPs (cancer stem cells) constitute ~0.3% of the original cell line population Histone Modification: Expression Compared to

Normal Tissue: Associated Cancer

H3K4me1 Decreased, increased upon progression Prostate

H3K4me2 Decreased, increased upon progressionLung, Prostate, Kidney, Non Small Cell Lung

Carcinoma, Hepatocellular Carcinoma, Breast, Pancreatic, Adenocarcinoma

H3K4me3 Decreased, increased upon progression Prostate

1 2 3 4 5 6 7 8 9 10 11 12 13

References• BBA-Reviews on Cancer, January 2011, Volume 1815, pages 75-89• Cell, 2 April 2010, Volume 141, Issue 1, pages 69–80• Journal of Biological Chemistry, 9 April 2010, Volume 285, pages 11045-11050• Nature, 11 June 2009, Volume 459, pages 847-851• Nature Biotechnology, 13 October 2010Volume 28,, pages 1057–1068• Nature Chemical Biology, 28 February 2010, Volume 6, pages 283-290