Abstract 264: Mesenchymal stem cells mediate epithelial-to-mesenchymal transition (EMT) and stemness regulation in pancreatic cancer via Notch signal.

Abstract

Abstract Cancer associate fibroblasts (CAFs), one of the major components of the cancer stroma, are prominently involved in tumor progression including epithelial to mesenchymal transition (EMT). Recently, bone marrow derived mesenchymal stem cells (MSCs) have been suggested as candidate for the source of tumor-promoting CAFs. We previously demonstrated that side population (SP) cells, which are enriched with so-called tumor initiating stem cell like cells (TISCs), play a pivotal role of local invasion and liver metastasis in pancreatic cancer (Int-J-Cancer 124:2771, 2009). Therefore, we formulated the hypothesis that MSCs regulate SP cells EMT and TISC-like properties such as tumor formation/progression. The AIM of the present study was to examine whether bone marrow-derived MSCs have ability to mediate EMT and/or tumor progression in pancreatic cancer SP cells. METHODS: MSCs were pre-treated with TGF-beta for 3 days. SP or non-SP cells were co-cultured in the presence or absence of TGF-beta-pretreated MSCs (Tb-MSCs) for 3 days. Real-time PCR experiments were performed to quantitate mRNA levels of EMT associated genes as well as so-called stemness related genes. PANC-1 derived SP or non-SP cells were co-injected with Tb-MSCs into NOD/SCID mice, and their tumorigenesity was evaluated. RESULTS: Co-culturing with Tb-MSCs dramatically induced EMT-associated mRNA alterations including suppression of E-cadherin and induction of slug in PANC-1 SP cells. In SP cells but not in non-SP cells, levels of stemness genes including CD133, Oct4, LGR5, were enhanced by co-culturing with Tb-MSCs. Tb-MSCs enhanced in vitro sphere forming activity as well as in vivo tumor formation in SP cells. These alterations including EMT-associated gene modifications and enhanced sphere formation were suppressed by Notch signal inhibition, suggested MSCs-associated regulation of EMT and TISC-like properties are mediated by Notch-signaling. In CONCLUSION, MSCs regulate EMT and they maintain TISC-like properties in pancreatic cancer SP cells via Notch signal-dependent mechanisms. Targeting Notch signaling would appear to be attractive to prevent MSCs and/or stromal cell-associated cancer progression. Citation Format: Ayano Kabashima-Niibe, Hajime Higuchi, Yumi Matsuzaki, Yo Mabuchi, Shinsuke Funakoshi, Masayuki Adachi, Yasuo Hamamoto, Hiromasa Takaishi, Toshifumi Hibi. Mesenchymal stem cells mediate epithelial-to-mesenchymal transition (EMT) and stemness regulation in pancreatic cancer via Notch signal. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 264. doi:10.1158/1538-7445.AM2013-264