ALDH1A1 and neoplasm: To determine the importance of ALDH1 to CoCSC tumorigenicity and resistance to CPA, we transduced UM-C6 tumor cells with shRNA targeting ALDH1A1. UM-C6 tumors were chosen because of their high ALDH1A1 expression and relatively low expression of other ALDH family members (e.g. ALDH3A1 & ALDH5A1; see Figure 4C).