Abstract 3353: The CD44 hi cell population from malignant pleural effusion derived lung tumors displays increased tumorigenic potential

Abstract

Abstract We have developed a new model system (http://dx.plos.org/10.1371/journal.pone.0005884) to test whether we can isolate candidate Cancer Stem Cell (CSC) populations from clinical specimens and validate that they possess increased tumorigenic and/or metastogenic potential. The model utilizes primary tumor cell populations derived from human malignant pleural effusions (MPE), which are cultured in an autologous tumor microenvironment (TME). This model system maintains intratumoral heterogeneity, and contains molecular signatures, surface phenotypes, and metabolic biomarkers that are associated with candidate CSC. The current study compares isogenic primary tumor subpopulations, separated on the basis of a surface biomarker expression, in terms of differences in molecular marker expression, and bioassays that measure clonogenic efficiency and tumorigenic potential. CD44, a surface CSC-biomarker, is expressed on most of the primary tumor cells (75-95%) derived from MPE. The CD44 expressing tumor cells can be divided into two groups (CD44hi) and (CD44lo) on the basis of CD44 surface labeling intensity. The CD44hi and CD44lo tumor cells were sorted (10% of each) from total tumor cell populations by FACS and evaluated for their clonogenicity on plastic (colony forming efficiency) and for colony forming units in soft agar (anchorage independent growth). Studies show that the CD44hi tumor cells are 40-60% more efficient in forming colonies, and give rise to larger colonies than CD44lo tumor cells. Expression of other candidate CSC biomarkers was also compared in the two cell subsets to determine the molecular correlates of CD44hi versus CD44lo cells. CD44hi cells coexpress higher levels of BMI-1, hTERT, EZH2, and OCT-4 by RT-PCR than CD44lo tumor cells, but there is no apparent difference in the expression of SUZ12 between these two populations. CD44hi cells also have increased ALDH expression based on the Aldefluor assay. To determine whether these subpopulations differed in terms of tumorigenic potential, limiting dilutions of cells were heterotopically (subcutaneous flank region) injected in NOD/SCID (IL-2gRnull) mice in comparison to CD44lo tumor cells. Low numbers of CD44hi cells (down to 300 cells) efficiently formed tumors, whereas isogenic CD44lo tumor cells failed to form tumors at the same cell doses. Thus, CD44hi cells have higher tumorigenic potential than CD44lo cells, and these studies suggest that these primary tumor populations are preferentially enriched for the candidate CSC phenotype. 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 3353.