Cumulative evidence strongly suggests that precursor peptides such as progastrins (PG) exert mitogenic/co-carcinogenic effects on target cells and increase the risk of tumorigenesis. Many tumors express PG, and down-regulation of gastrin gene/PG expression attenuates growth of PG-dependent cancer cells. We recently discovered that extra-cellular membrane-associated annexin A2 (ANXA2) represents a novel receptor for PG. At the same time, ANXA2 expression has been reported to be critical for maintaining the growth of epithelial cancer cells. More recently, we discovered that over-expression of PG in HEK-293 cells significantly increased stem cell populations, positive for DCAMKL+1/Lgr5/CD44, and surprisingly resulted in tumorigenic transformation of the cells. In an important related study we reported potent inhibition of PG stimulated growth on cancer cells via the inhibition of critical signaling pathways. Our preliminary studies suggest that curcumin significantly reduces expression of ANXA2 and stem cell markers;intriguingly opposite effects of curcumin were measured on DCAMKL+1 expression in transformed versus non-transformed epithelial cells, Based on these novel findings we will test the hypothesis that 'chemo/dietary preventive agents differentially modulate growth factor-mediated expression of ANXA2 and stem cell markers in non-tumorigenic versus tumorigenic epithelial cells'. Towards this goal, we will focus on examining the effects of curcumin.
In Aim 1, relative inhibitory efficacy of curcumin on growth of non-transformed/transformed epithelial cells, enriched for ANXA2/stem cell markers will be examined using in vitro and in vivo models of investigation. Regulatory effects of curcumin on expression of ANXA2/stem cell markers in non-tumorigenic/tumorigenic cells will be examined in relation to growth inhibitory effects of curcumin. Target-specific siRNA/shRNA against stem cell markers will be used to augment inhibitory effects of curcumin. Results of these studies will likely have therapeutic implications.
In Aim 2 mechanisms by which curcumin reduces stimulatory effects of PG on the expression of ANXA2/stem cell markers will be examined in transformed/non-transformed cell lines at protein and RNA levels;inhibitory effects at the transcriptional level will be examined in promoter-reporter assays. These experiments will expand our understanding of the interplay between growth factors, curcumin and stem cell markers.
In Aim 3, dose-dependent effects of dietary curcumin against initiation, promotion, and progression phases of colon carcinogenesis in transgenic mice over-expressing PG, in relation to efects on ANXA2/stem cell markers will be examined. Pre-neoplastic and neoplastic growths and surrounding normal mucosa wil be analyzed for relative expression of ANXA2/stem cell markers in relation to activation of 2- catenin/NF:Bp65 and other transcriptional factors. Results of these studies are expected to help us develop mechanism-based strategies for prevention and/or treatment of cancers in patients, positive for circulating PG (growth factors) and/or ANXA2 expressing tumors.
In this grant application it is proposed to examine if a combination of dietary supplements and non- toxic small inhibitory molecules can prevent or treat the growth of solid tumors and eradicate the seed cancer cells so that the threat of recurrence is significantly reduced. We will also examine the mechanisms by which specific molecules, discovered in the past few years by our laboratory, increase the risk of developing cancerous growths, and the mechanisms by which dietary agents reduce this risk. The results of these studies are expected to help us develop more effective strategies for preventing and treating solid tumors in organs such as the colon, using less toxic methods.
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