ALDH1A2 and cancer: Analysis of primary pancreatic tumors for Aldh1a2 using RNA in situ hybridization (RNA-ISH) identified rare epithelial tumor cells expressing this stem cell marker, but the majority of expression was present within the cancer associated stromal cells (Figure 4B), consistent with immunohistochemistry for ALDH protein in human PDAC (Rasheed et al., 2010).