Semester

Summer

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Microbiology, Immunology, and Cell Biology

Committee Chair

Bing-Hua Jiang.

Abstract

PI3K/AKT pathway plays an important role in tumor progression and angiogenesis. To determine the specific role of PI3K isoform p110alpha in ovarian cancer, we designed small interfering RNA (siRNA) against p110alpha. The expression of p110alpha siRNA significantly decreased cell migration, invasion, and proliferation. AKT has three different isoforms: AKT1, AKT2 and AKT3. We found that downregulation of AKT1 is sufficient to inhibit cell migration, invasion, and proliferation in ovarian cancer cells. The activation of p70S6K1 was decreased in both p110alpha and AKT1 siRNA-expressing cells. Inhibition of p70S6K1 activity also decreased cell migration, invasion, and proliferation.;The tuberous sclerosis complex-2 (TSC2) lies upstream of mTOR/p70S61 and downstream of AKT. Loss of TSC2 expression is observed in human cancer. To study the function of TSC2 in ovarian tumor angiogenesis, we established stable cell lines that express siRNA specific to TSC1 and TSC2. In this study, we show that inhibition of TSC1 and TSC2 increased the expression of HIF-1alpha in ovarian cancer cells. Inhibition of TSC1 and TSC2 upregulated VEGF expression at both mRNA and protein levels. Downregulation of TSC2 induced ovarian tumor angiogenesis and tumor growth through mTOR/p70S6K1. The expression of p70S6K1 siRNA decreased VEGF protein expression and VEGF transcriptional activation through the HIF-1alpha binding site. The expression of p70S6K1 siRNA specifically inhibited HIF-1alpha expression in ovarian cancer cells. We also found that p70S6K1 down-regulation decreased ovarian tumor growth and tumor angiogenesis. This study provides a novel molecular mechanism of human ovarian cancer induced by the activation of p70S6K1.;Survivin gene is highly expressed in ovarian cancer cell lines and is a potential target of gene therapy for ovarian cancer. Our study showed that expression of survivin siRNA induced cell apoptosis when combined with LY294002 or taxol treatment. We determined that suvivin mRNA is regulated by PI3K/AKT/p70S6K1 pathway. Survivin is an important downstream molecule of PI3K/AKT/p70S6K1 pathway that plays a role in antiapoptosis in ovarian cancer cells.

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