Colon cancer is the second common cause of mortality and morbidity in the United States. Despite recent advances in the treatment of colon cancer, there are no effective chemopreventive treatments available at this time and the outcome tends to be poor in these available strategies for a high number of patients. The work described in this proposal explores a novel chemopreventive approach which targets pro-oncogenic CD44v6 protein expressions that block the development of colon cancer. We have developed a novel nanoparticle delivery system that selectively directs CD44v6shRNA to intestine/colon cells and blocks adenoma formation. This approach is supported by the following observations: (1) CD44v6 is overexpressed in adenoma cells compared to normal cells. (2) CD44v6 is a specific cancer stem cell marker than total CD44, and can be used in conjunction with CD166 or CD133 to isolate cancer stem cells. (3) Knocking down CD44v6 expression in vivo reduces the size and number of adenomas in the Apc Min/+ mouse model, in which adenomas grow spontaneously. 4) Knocking down CD44v6 in sorted cancer stem cells reverses their drug resistance and the growth in soft agar. 5) Knocking down CD44v6 in pre-adenoma Apc10.1 cells inhibits signaling downstream from the binding of HA to CD44v6, and the binding of HGF to CD44v6 and c-Met. These observations suggest the hypothesis that CD44v6 is a key transmembrane protein in the regulation of intestine/colon tumor cell growth initiation and progression: we postulate that blocking CD44v6 expression by CD44v6shRNA delivered "early" (before adenomas develop) via nanoparticles into weanling Apc Min/+ mice will effectively prevent adenoma formation. We also postulate that tissue-specific delivery of CD44v6shRNA/nanoparticles provide a novel tissue targeted chemopreventive approach. We have two aims:
Aim 1) To determine the efficacy and pharmacokinetics of CD44v6shRNA in intestinal adenomas using a weanling Apc Min/+ mouse model. Efficacy will be defined as effects of CD44v6shRNA on adenoma size/number. Pharmacokinetics of CD44v6shRNA will be determined by studying the distribution of CD44v6shRNA as well as Cre plasmid in the targeted intestine adenomas in comparison with that of normal intestine/colon tissues.
Aim 2) To determine the effect of CD44v6shRNA on: pharmacodynamic markers (components of the CD44v6- induced c-Met signaling cascade) in adenoma tissue;biomarkers of adenoma formation and progression (HGF, HA, PGE2 and soluble CD44v6) in serum;and cancer stem cell markers (CD44v6, CD166, CD133 and p- PTEN) in early intestinal adenomas in the Apc Min/+ mouse model. The proposed studies will advance the potential of CD44v6shRNA as a chemopreventive agent to alter the behavior of cancer precursor lesions.
The proposed work highlights the health impact in finding alternative chemo-preventive agent, such as CD44v6shRNA. CD44v6 which is highly expressed in colon cancer (CRC) signals tumor specific properties. Silencing CD44v6 expression before colon tumor develops is a novel chemoprevention approach for CRC.
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