PDX1 and cancer: Furthermore, studies assessing protein and messenger RNA levels of PDX1 (a key transcriptional regulator in early-stage development of the pancreas and an embryonic progenitor cell marker) in human PDAC showed that PDX1 was most strongly expressed at the “leading edge” of a tumor where there is a high density of cancer stem/tumor-initiating cells (CSC/TIC) [7,8].