Resistance of stem-like cells from neuroblastoma cell lines to commonly used chemotherapeutic agents.

Background. Cancer stem cell theory suggests that the presence of tumor initiating stem-like cells in cancers may be responsible for cancer progression and relapse. CD133 cell surface maker expression has been used to identify stem-like cells in cancer cell lines. Our goal was to identify such cells in neuroblastoma cell lines and to study the cytotoxicity of common anticancer drugs for those cells. Materials and Methods. CD133þ cells from SK-N-SH and SK-N-BE cell lines were isolated using magnetic microbeads. Cytotoxicity of four anticancer drugs was studied on CD133þ and CD133� populations. The percentage of live, apoptotic, and dead cells in each population after drug treatment was estimated by MTT and PI/ Annexin-binding assays. Western blot analyses were used to identify differences in the expression of kinases. Results. Eight to 10% of SKN-SH and 3–5% of SK-N-BE cells were CD133þ. These cells were more resistant than CD133� cells to all four chemotherapeutic agents tested in the MTT assay. Decreased apoptosis was observed in CD133þ cells compared to CD133� cells by PI/Annexin V-binding assay. Western blot analysis showed that CD133þ cells expressed less MKP-1. Phosphorylated forms of both ERK and P-38 kinases were expressed at higher levels in CD133þ cells than in CD133� cells. Conclusions. This study suggests that CD133þ cells are more resistant to anticancer drugs than CD133� cells. Differences in the expression and phosphorylation of kinases could be partially responsible for this difference. Targeting CD133-expressing cells could be a strategy to develop more effective treatments for neuroblastoma. Pediatr Blood Cancer 2010;54:361–368. 2009 Wiley-Liss, Inc.