Cancer stem cell gene signature of ovarian tumor side populations

Abstract

5546 Background: Recent studies support the concept that cancer as a disease is driven by a small subset of cells, cancer stem cells. These cells can initiate tumor growth and re-initiate tumor expansion after therapy. The aim of this study is to generate a cancer stem cell gene expression signature from isolated Side Populations (SP) of fresh ascites obtained from women with high-grade advanced stage papillary serous ovarian adenocarcinoma. Methods: All patient specimens were collected/studied under protocols approved by the institutional review board of the parent institution. Gene expression profiling using Affymetrix U133 2.0 Plus microarray was performed on SP and Main Populations (MP) isolated by Hoechst staining/FACS method. Paired T-test analyses (p<0.01) identified differentially expressed genes between SP and MP. The microarray data was validated using qRT-PCR. Results: 446 differentially expressed genes (138 up- and 302 down-regulated) were found between all 10 SP/MP pairs. Microarray validation on 19 randomly selected differentially regulated genes, showed 17/19 (89.5%) genes has robust correlations between microarray and qRT-PCR expression data. The gene signature was enriched for genes in GO biological processes of cell cycle, transport, apoptosis, regulation of translation/transcription, signal transduction, and cell proliferation. Further data mining for biologically relevant processes using Pathway Studio 5.0 identified overexpressed genes in SP related to functional cancer stem cell-like phenotypes of cell survival (PAWR), proliferation (EPHB), and apoptosis (AKT). WNT signaling pathway genes (FZD) were downregulated in SP, and genes implicated in normal stem cell function (NUP, ST3GAL, LTBP) were upregulated in SP. These results highlight the ‘stemness function‘ of the ovarian cancer SP gene signature. Conclusions: We generated an expression profile from SP enriched for cancer stem cells from ascites from ovarian cancer patients. The ‘stemness‘ nature of the SP gene signature was revealed by the identification of several stem cell-related genes and genes involved in the WNT -signaling pathway. These genes may be key players involved in the mechanisms controlling ovarian cancer stem cell functions, and may represent potential therapeutic targets. No significant financial relationships to disclose.