Abstract 3372: Analysis of putative tumor stem cell markers in the NCI-60 tumor cell line panel

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Tumor stem cells or cancer initiating cells are tumor cells that can regenerate a recurring tumor or a metastasis. A variety of cell surface and other markers have been associated with identification and characterization of tumor stem cells. We investigated the expression of a number of these putative stem cell markers (CD15, CD24, CD44, CD133, CD166, CD326, PgP, and aldehyde dehydrogenase) in the NCI60 tumor panel. A spectrally compatible set of labeled antibodies was designed to enable simultaneous evaluation of six markers (CD44, CD24, CD133, CD166, CD326 (EpCAM), and PgP, and forward (FSC) and side scatter (SSC). Marker expression patterns were analyzed by multiple component analysis and correlated with clonogeneic potential of cell lines (2D colony formation assay, anchorage independent colony formation in soft agar assay). Additionally sphere formation in suspension culture and the capacity of cell lines to form tumors in vivo upon injection with matrigel was assessed for colon cancer cell lines. Analysis of expression of single markers and co-expression of up to 6 markers demonstrated that all stem cell markers investigated are expressed in cell lines of the NCI-60 panel. Patterns of co-expression of these markers as defined by multiple component analysis tracked primarily with tumor type, but individual patterns were also observed to occur in multiple tumor types. In the breast cancer panel the patterns of co-expression segregated with the known molecular sub-types (basal, luminal, normal-like) of the tumor cell lines. Cells from colonosphere cultures generated from the colon tumor panel using serum-free, growth factor supplemented medium showed subtly different co-expression patterns. Both sphere-derived and bulk cultured colon tumor cells were highly tumorigenic in NOD/SCID mice and tumor formation was observed following inoculation of 10-100 cells. Only two out of seven of the colonosphere derived cell populations had enhanced tumor initiating ability, but did not share differences in stem cell marker display with respect to the unselected bulk cultures. Furthermore, marker expression patterns did not significantly correlate with in vitro colony formation (2D culture, soft agar). Our results demonstrate a high degree of complexity and heterogeneity in tumor stem cell marker display that can be influenced by culture conditions and relates to the histological classification of tumors rather than to the clonogenic potential of cells in cell lines of the NCI60 panel. 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 3372.