Tumor formation and growth is dictated by a very small number of tumor cells, called cancer stem cells, whichare capable of self-renewal. The genesis of cancer stem cells and their resistance to conventional chemotherapyand radiotherapy via mechanisms such as multidrug resistance, quiescence, enhanced DNA repair abilities andanti-apoptotic mechanisms, make it imperative to develop methods to identify and use these cells as diagnosticor therapeutic targets. Aldehyde dehydrogenase 1 (ALDH1) is used as a cancer stem cell marker. In this study,we evaluated ALDH1 expression in CaSki, HeLa and SiHa cervical cancer cells using the Aldefluor method toisolate ALDH1-positive cells. We showed that higher ALDH1 expression correlated with significantly higherrates of cell proliferation, microsphere formation and migration. We also could demonstrate that SiHa-ALDH1-positive cells were significantly more tumorigenic compared to SiHa-ALDH1-negative cells. Similarly, SiHacells overexpressing ALDH1 were significantly more tumorigenic and showed higher rates of cell proliferationand migration compared to SiHa cells where ALDH1 expression was knocked down using a lentivirus vector.Our data suggested that ALDH1 is a marker of cervical cancer stem cells and expand our understanding of itsfunctional role.
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