Abstract 4254: The Wnt/ B-catenin pathway regulates colon cancer stem cells proliferation

Abstract

Abstract It is becoming increasingly evident that a small sub-population of self-renewing, multipotent cells termed cancer stem cells (CSCs) is responsible for driving majority of the epithelial cancers including colon cancer. The observation that CSCs display resistance to conventional chemotherapeutics suggests that they may be responsible for the recurrence of cancers. One of the properties of CSCs is that they form floating spheroids (colonosphere) in a defined media. Different signaling pathways such as Wnt, Hedgehog, Notch and Bmi have been implicated in the regulation of colonosphere formation and stem cell self renewal. The current investigation was undertaken to examine the role of Wnt/B-catenin pathway in regulating the growth and maintenance of colonosphere. Human colon cancer cells HCT-116 (p53 wild type; K-ras mutant), HCT 116 (p53 null; K-ras mutant) and HT 29 (p53 mutant) were used. We have observed that colonospheres formed in vitro exhibited higher expression of colon CSCs markers ALDH1, LGR5, CD133, CD44 and Musashi, compared to the corresponding parental cancer cells, indicating the predominance of CSCs in colonosphere. Further support for this inference comes from the FACS analysis that show 95-97% of CD44 positive cells in colonospheres. Additionally, colonosphere showed increased levels of B-catenin, cyclin D1 and C-Myc and down-regulation of Axin-1 and phosphorylated B-catenin. Increased expression of B-catenin was associated with a marked transcriptional activation of TCF-LEF. To determine whether B-catenin plays a role in the maintenance and formation of colonosphere, we transfected the colon cancer cells with B-catenin siRNA and subsequently analyzed colonosphere formation. The results revealed a marked reduction in the colonosphere formation following down-regulation of B-catenin indicating its role in colonosphere formation. Further support for this interpretation comes from the observation that the upregulation of cMYC /cyclin D1 (the target genes of LEF/TCF) results in enhancement of the colonosphere formation. In conclusion, our data suggest that Wnt/B-catenin pathway plays a critical role in the growth of CSCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4254.