Abstract A05: Phosphoinositide-3-kinase pathway promotes colon cancer stem cell proliferation

Abstract

Abstract Introduction. The cancer stem cell (CSC) model posits that a select cell-subpopulation exists in solid tumors that sustain tumorigenesis. Previously, we have shown that aldehyde-dehydrogenase (ALDH) enriches colon CSCs (CCSC) from sporadic colon cancer. In this study, Affymetrix microarray was used to screen for differences between ALDHhi and ALDHlo cells isolated from sporadic human colon adenocarcinoma. As a result, the phosphoinositide-3-kinase (PI3K) pathway was identified as a potential regulator of CCSC growth and differentiation. Functional assays demonstrate that inhibition of PI3K results in significant reduction in proliferation and colony formation of by CCSCs. Experimental Procedures. Unbiased Expression-Profile Analysis: We implanted human CCSCs into flanks of NOD-SCID mice. Flow assisted cell sorting discriminated resulting tumor epithelia into ALDHhi and ALDHlo groups from 6 individual sporadic human adenocarcinomas, which were analyzed using Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. Proliferation Assay: Bromodeoxyuridine (BrdU) incorporation measured the effect of LY294002 (Calbiochem) (1-100 μM) on proliferation. Colony Assay: Methylcellulose colony assays were used to assess the effect of LY294002 on colony formation. Summary of Data. Expression Profile Analysis revealed 136 genes that were significantly up or down-regulated in the ALDHhi cell groups (>3-fold; p<0.001). The beta regulatory subunit of phosphoinositide-3 kinase demonstrated a 5.2 fold up-regulation in the ALDHhi vs. ALDHlo CCSCs. Cell Proliferation Assay: LY294002 significantly inhibits CCSC proliferation with IC50 ~ 50 μM and near complete inhibition at the dose of 100 μM (p<0.001). Colony Assay: LY294002 significantly reduces total colony area formed by CCSCs, with a similar trend as shown in BrdU proliferation assays (p<0.001). Conclusions. We have previously shown that ALDH enriches colon cancer epithelia. Here we show that the PI3K signaling pathway is differentially expressed between ALDHhi and ALDHlo CCSCs derived from primary tumor xenografts. We demonstrate in vitro functional differences in CCSCs with drug-inhibition assays. Citation Format: Sugong Chen, Robert C. Fisher, Anitha K. Shenoy, Maria Cecilia Lopez, Lyle L. Moldawer, Henry V. Baker, Emina H. Huang. Phosphoinositide-3-kinase pathway promotes colon cancer stem cell proliferation. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A05.