Normoxic or hypoxic CD44/CD41 a₂ B₁ integrin-positive prostate PC3 cell side fractions and cancer stem cells.

A CD44/a 2 B 1- (CD41 integrin) and B-catenin-labeled fraction of PC3 prostate cancer cells is able to reconstitute cells representative of the original tumor in immuno-deficient mice (Li et al. in Cancer Res 68:1820-1825, 2008). After 48 h of culture under nitrogen with a resulting medium pH of 7.8, sorted hypoxic PC3 cells yielded a higher percentage and concentration/10(5) of cells in a doubly labeled (DL) CD44(+)/CD41(+) side fraction compared with control cells cultured under normoxia (5 % CO2 in the ambient atmosphere at 37 °C). When the rise in pH was prevented (95 % N2, 5 % CO2), the difference in sorted hypoxic cell numbers remained. Sorted N and H DL cells and CD44(+)/CD41(-) cells were cultured under standard conditions. After 1-2 weeks, the number of attached colonies from formerly hypoxic cells, whether previously cultured with N2 or 95 % N2 + 5 % CO2, exceeded the number of doubly labeled normoxic cells, consistent with their greater initial concentration. Cultured sorted N or H CD44(+)/CD41(-) cells resulted in monolayers containing a small percentage of DL cells. Recovery of greater percentage and numbers of putative cancer stem cells, confirmed by quantitative cell sorting after culture under hypoxic conditions, is consistent with their greater relative numbers present in hypoxic niches. In addition, the report that neither CD44(+) nor CD41(+) epitopes were preferentially associated with FAM65B(high)/MF12(low)/LEF1(low) PC3 cells able to reconstitute tumors in immuno-deficient mice (Zhang and Waxman in Mol Cancer 9:319-330, 2010) suggests an in vitro mimic of tumor cell heterogeneity observed in epithelial cancers.