Cancer Stem Cell Gene Signature Identified From Advanced Stage Papillary Serous Ovarian Adenocarcinoma Side Populations

AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA 5005 Recent studies support the concept that cancer as a disease is driven by cancer stem cells and these are the cells that can both initiate tumor growth and then re-initiate tumor expansion after therapy. Hence an understanding of gene expression profiles of cancer stem cells may lead to improved therapies as well as novel insights into the cellular mechanisms of carcinogenesis in ovary. The aim of this study is to generate a cancer stem cell gene expression signature from isolated Side Populations of fresh ascites obtained from women with high-grade advanced stage papillary serous ovarian adenocarcinoma at the time of cytoreductive surgery at Brigham and Women's Hospital, Boston, MA. All patients had been diagnosed with ovarian cancer for the first time. All patient specimens were collected and studied under protocols approved by the institutional review board of the parent institution. Gene expression profiling using Affymetrix Human Genome U133 2.0 Plus microarray platform was performed on Side Populations (SP) and Main Populations (MP) isolated by Hoechst staining/FACS method. Array data was analyzed using BRB-ArrayTools. Paired T-test analyses (p<0.01) was utilized to identify differentially expressed genes between SP and MP. We identified 446 genes (138 up-regulated and 302 down-regulated) that were differentially expressed between all 10 SP and MP pairs. The microarray data was validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR) on 19 randomly selected differentially regulated genes. 17/19 (89.5%) genes showed robust correlations between microarray and qRT-PCR expression data. The gene signature was enriched for genes in Gene Ontology 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 genes overexpressed in SP that were 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 (NUP, ST3GAL, LTBP) were upregulated in SP. Taken together these results highlight the function of the ovarian cancer SP gene signature. In conclusion, we generated an expression profile from SP enriched for cancer stem cells from ascites from ovarian cancer patients. The nature of the stemness 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.