Transforming Growth Factor β1 Contributes to the Invasiveness of Pancreatic Ductal Adenocarcinoma Cells Through the Regulation of CD24 Expression

Objectives: The aim of this study was to investigate the role of CD24 in the invasiveness of pancreatic ductal adenocarcinoma (PDAC). Methods: We used 2 human PDAC cell lines containing large numbers of CD24-positive (CD24(+)) cells (> 65%; AsPC-1 cells) or few CD24(+) cells (< 20%; CFPAC-1 cells). Invasiveness was estimated using the Matrigel invasion assay. The role of CD24 in invasiveness was evaluated using small interference RNA against CD24 mRNA. Results: The invasive ability of CD24(+) cells collected by cell sorter was higher than that of CD24-negative (CD24(-)) cells. On the other hand, silencing of CD24 decreased the invasive ability of CD24(+) cells. Importantly, considerable amount of CD24(+) cells was converted to CD24(-) cells within 24 hours under in vitro culture condition. Transforming growth factor beta 1 significantly inhibited this conversion and consequently maintained the high invasiveness of CD24(+) cells. Conclusions: Our data show that CD24 contributes to the invasive ability of PDAC and also suggest that transforming growth factor beta 1 may contribute to the invasiveness of PDAC by suppressing the conversion from CD24(+) cells to CD24(-) cells at the tumor site.