Cancer is a nondiscriminatory disease afflicting millions of Americans annually. Cancer accounts for approximately 23% of all deaths, ranking second only to heart disease. A hallmark trait of cancer, irrespective of tissue type, is the ability of malignant cells to grow faster than normal cells. RNA polymerase III (RNA pol III) catalyzes the transcription of many of the small structural RNA molecules required for processing (U6 snRNA) and translation (tRNA). Thus, RNA pol III plays a key role in regulating the growth of a cell. RNA pol III products have been demonstrated to be specifically elevated in a variety of cancers. Accurate initiation by RNA pol III requires TFIIIB, implicating TFIIIB‐mediated transcription as an important determinant of the biosynthetic capacity of a cell. TFIIIB is a target for repression by tumor suppressors and activation by oncogenes. The green tea component EGCG has been demonstrated to inhibit the growth of a variety of cancer cells in vivo and in vitro. Hence, both EGCG and RNA pol III have the capacity to modulate cell proliferation. We hypothesized that EGCG could modulate RNA pol III transcription. Our preliminary data demonstrates that EGCG can (1) repress both gene internal and gene external RNA pol III transcription in cervical, prostate and breast carcinoma cells, (2) suppress protein expression levels of the TFIIIB subunits Brf1 and Brf2, and (3) inhibit both Brf1 and Brf2 promoter activity in vivo. The long term goal of this project is to elucidate the molecular mechanisms governing the regulation of RNA pol III transcription by the green tea component EGCG to identify novel pharmacological targets for cancer therapy. To address our long term goal, in specific aims 1 and 2 of this research proposal we will identify cis‐regulatory elements in the Brf2 and Brf1 promoters regulated by EGCG, using deletion and mutation analysis in cervical, breast, and prostate cancer cells treated with EGCG.
In specific aim 3, we will determine if EGCG regulates expression of the TFIIIB subunits Bdp1 and TBP by western blotting and RT‐PCR in response to EGCG treatment in cancer cells.
In the United States, women have approximately a 1 in 3 and men a 1 in 2 lifetime risk of being diagnosed with cancer. Hence, identification of the mechanism(s) by which EGCG inhibits RNA polymerase III transcription is a key event in understanding how nutriceuticals play a role specifically inhibiting cancer growth and will ultimately identify novel pharmacological targets for cancer drug development.
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