SPORE: Research Projects
Project 1 (Renewal)
Carcinogenic Metals, Colorectal Neoplasia Risk and Progression in Appalachia
Project Leaders: Mark Dignan, Li Li (Case Western Reserve University), Xianglin Shi
Project 2 (P20 Funding)
Hepatitis C and Tumor Suppressors in Hepatocellular Carcinoma
Project Leader: Stanley Lemon (University of North Carolina at Chapel Hill)
This project seeks to determine the clinical relevance and potential role in hepatic carcinogenesis of interactions between host cell and hepatitis C virus (HCV) proteins that have been identified in previous cell culture-based experiments. The retinoblastoma susceptibility protein (pRb) and the cellular DEAD-box RNA helicase DDX3 play critical roles in regulating the cell cycle. Our previous work indicates that the HCV RNA polymerase, NS5B, forms a complex with pRb, targeting it for ubiquitination and proteasome-dependentdegradation, activating E2F-responsive promoters, and stimulating cell proliferation. Similarly, HCV core protein expression alters the cellular abundance and localization of DDX3. Our hypothesis is that these and other interactions with host proteins (p53 and DDX5) promote proliferation of hepatocytes and impair DNA damage responses, thereby contributing to HCV carcinogenesis. In Aim 1, we will develop and validate fluorescent quantum dot probes capable of sensitive detection of HCV proteins expressed in virus-infected cells. We will also determine whether HCV protein expression correlates with altered tumor suppressor expression in transgenic mice. Aim 2 will utilize these novel probes in laser scanning confocal and multi-photon microscopy studies of liver tissue from patients with chronic hepatitis C, and ask whether the abundance and cellular localization of pRb, p53, DDX3, or DDX5 is altered in infected hepatocytes. In Aim 3, we will determine whether HCV infection is associated on a single-cell basis with increased expression of the proliferation markers Ki-67 and PCNA. We will also determine whether the proportion of cells displaying proliferation markers is reduced after standard-of-care peg-IFN/ribavirin therapy. These results will be correlated with oligonucleotide microarray and quantitative RT-PCR assays to determine whether liver specimens with a high proportion of HCV-infected cells display transcriptional patterns indicative of hepatocellular proliferation and/or E2F transcription factor activation. RELEVANCE TO PUBLIC HEATH: Liver cancer is one of the most rapidly increasing types of cancers in the United States, reflecting an increased prevalence and risk of liver cancer in persons with chronic hepatitis C. This project seeks a better understanding of the interaction of HCV proteins with important regulators of cell proliferation (pRb, p53, DDX3, and DDX5) and the role of such interactions in liver cancer caused by HCV infection.
Project 3 (Renewal)
Targeting WNT Signaling in Colorectal Cancers with Novel Derivatives of Natural Products
Project Leaders: B. Mark Evers, Chunming Liu, David Watt
Project 4 (P20 Funding)
Targeted Inhibition of PI3K Pathway Components as Novel Treatment of Colorectal Cancers
Project Leader: B. Mark Evers
Colorectal cancer is the second leading cause of cancer deaths in the United States. When localized to the mucosa and submucosa of the bowel wall (Stage I), the five year survival approaches 100%; however, metastasis to lymph nodes (Stage III) results in a precipitous decrease in five year survival and systemic metastasis to the liver (ie, Stage IV) is associated with a five year survival that is less than 5%. Activation of phosphatidylinositol 3-kinase (PI3K), a ubiquitous lipid kinase composed of an 85 kDa regulatory subunit (p85) and a 110 kDa catalytic subunit (p110), and its downstream effector protein, Akt, is associated with the growth and progression of a number of cancers, including colorectal cancer. We have shown that inhibition of PI3K/Akt decreases viability and growth, increases differentiation and apoptosis of human colorectal cancer cells. Furthermore, PI3K/Akt inhibition decreases colon cancer xenograft growth in athymic nude mice and sensitizes these cancers to the apoptotic effects of chemotherapeutic agents (eg, 5-FU). Moreover, we have shown altered PI3K/Akt expression in colorectal cancers and surrounding stroma with increased expression of the p85a subunit and Akt2 in colorectal cancers of increasing stage. Targeted inhibition of either p85a or p110a by RNA interference (RNAi) increased sensitivity of resistant colorectal cancers to the effects of chemotherapy and significantly suppressed colorectal cancer metastasis to the liver in preclinical animal models. The central hypothesis of this project is that colorectal cancer growth and progression are augmented by increased p85a and Akt2 expression; the selective inhibition of PI3K/Akt components can suppress colorectal cancer growth and metastasis and can sensitize resistant colorectal cancers to chemotherapeutic agents. The long-term goal is to develop more selected therapies for colorectal cancer progression and metastasis based on a systematic analysis of colorectal cancers, tumor stroma and surrounding mucosa for expression of PI3K/Akt pathway components. To examine our hypothesis and address the long-term goal, we have designed experiments with the following Specific Aims:
1. To provide clinical validation of the pattern and significance of PI3K/Akt/PTEN pathway component expression in polyps and colorectal cancers of different stages.
2. To assess novel strategies of selective PI3K component inhibition on in vivo tumor growth and liver metastasis using preclinical animal models.
3. To evaluate the therapeutic efficacy of RNAi to the PI3K pathway in combination with conventional chemotherapy. The cumulative information derived from these studies will lead to better targeted therapeutics and treatment paradigms for colorectal cancer.