Chemotherapy sorting can be used to identify cancer stem cell populations.

Cancer stem cells (CSCs) of bladder transitional cell cancers (BTCC) had not been identified by the reported common methods. According to the phenomenon that CSCs were resistant to chemotherapy, BTCC cell lines T24 and 5637 were cultured with mitomycin C respectively. Cell inhibition assay revealed an increased population of drug resistant cancer cells with a concentration gradient of mitomycin C. The maximal and minimal cell inhibition rate in cell line T24 was 92.5 % ± 1.0 versus 64.1 % ± 1.4 (P < 0.001), and in cell line 5637 was 90.2 % ± 2.5 versus 55.1 % ± 1.8 (P < 0.001), respectively. There is no significant difference between these two groups. Drug resistant cells just comprised approximately 7.5 % (T24) versus 9.8 % (5637) of the total cells. Compared with control cells, cell cycle analysis demonstrated that more drug resistant cells were at G0G1 phase and fewer were at S phase with the concentration gradient of mitomycin C in both cell lines, which is in accord with the stem cell theory that most stem cells maintain in a quiescent condition. Importantly, we found that embryonic stem cell markers (OCT-4 and NANOG) were highly expressed in both gene and protein level in BTCC cell line T24 and 5637 after 24-h chemotherapy exposure. Interestingly, the drug concentration gradient was in accord with OCT-4 and NANOG expression, suggesting that chemotherapy sorting might be a feasible method for BTCC CSCs identification.