Abstract 3863: The stemness of gastric cancer stem cells is sustained by TGFβ produced from cancer-associated fibroblasts

Abstract

Abstract Purpose: Cancer-associated fibroblasts (CAFs) have recently been implicated in tumor growth and metastasis in gastric cancer. Cancer stem cells. (CSCs) have been proposed to have an important role in cancer progression. CSCs are known to display stem cell properties, “stemness”, the ability to sustain self-renewal. Because CAFs are abundant in the stroma of gastric cancer, CAFs are supposed to affect CSC characteristics of gastric cancer. However, the effects of CAFs on the characteristics of gastric cancer CSCs have not been clarified. The aim of this study was to clarify the effect of CAFs on CSCs characteristics in gastric tumor microenvironment. Experimental Design: Four gastric cancer cell lines, OCUM-12, OCUM-2MD3, MKN-45, and MKN-74, were used. Side population (SP) cells were sorted by flow cytometry as CSC-rich cells from each parent cell line. CaF-37 was established from the tumoral gastric specimens as CAFs. Flow cytometric analysis of SP fraction, spheroid colony assay, and RT-PCR analysis of CSC markers, ABCG2, ALDH1, CD44, CD133, NANOG, and OCT3/4, were performed to identify CSCs properties. Effect of CAFs on the tumorigenicity by OCUM-12/SP cells was examined using nude mice. Results: CaF-37 significantly increased the percentages of the SP fraction of scirrhous-type of gastric cancer cells, OCUM-12/SP and OCUM-2MD3/SP cells, but not that of non-scirrhous-type of gastric cancer cells, MKN-45/SP and MKN-74/SP cells. Taken together, CaF-37 significantly increased the number of spheroid colonies and the expression level of CSC markers of scirrhous-type of gastric cancer cells. These stimulating-activities by CaF-37 were significantly decreased by TGFβ inhibitors, but not FGFR and cMet inhibitor. Also, SP fractions of scirrhous-type of gastric cancer cells were significantly increased by TGFβ, but not by FGF2 and HGF. Tumorigenicity by subcutaneous co-inoculation of OCUM-12/SP cells with CaF-37 was significantly high in comparison with that by OCUM-12/SP cells alone. Phospho-Smad2 expression level was significantly increased by co-inoculation with CaF-37. Conclusions: TGFβ from CAFs in the tumor microenvironment might sustain the stemness of CSCs of gastric cancer cells, especially in scirrhous-type of gastric cancer. Citation Format: Masakazu Yashiro, Tsuyoshi Hasegawa, Tatsunari Fukuoka, Haruhito Kinoshita, Tamami Morisaki, Hiroaki Kasashima, Go Masuda, Naoshi Kubo, Kosei Hirakawa. The stemness of gastric cancer stem cells is sustained by TGFβ produced from cancer-associated fibroblasts. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3863. doi:10.1158/1538-7445.AM2014-3863