Expression and functional role of ALDH1 in cervical carcinoma cells.

Tumor formation and growth is dictated by a very small number of tumor cells, called cancer stem cells, which are capable of self-renewal. The genesis of cancer stem cells and their resistance to conventional chemotherapy and radiotherapy via mechanisms such as multidrug resistance, quiescence, enhanced DNA repair abilities and anti-apoptotic mechanisms, make it imperative to develop methods to identify and use these cells as diagnostic or 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 to isolate ALDH1-positive cells. We showed that higher ALDH1 expression correlated with significantly higher rates 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, SiHa cells overexpressing ALDH1 were significantly more tumorigenic and showed higher rates of cell proliferation and 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 its functional role.