Bone marrow-derived mesenchymal stem cells (MSCs) are reported to contribute to the formation of tumor stroma. We reported recently that in an orthotopic nude mouse model of human colon cancer, MSCs migrated to tumor stroma, where they differentiated into carcinoma-associated fibroblast (CAF)-like cells and promoted tumor growth and metastasis. Furthermore, the migratory and invasive abilities of KM12SM colon cancer cells were shown by Transwell invasion assay to be enhanced by indirect co-culture with MSCs. However, the molecular mechanisms of this phenomenon have not been elucidated. We performed microarray analysis of gene expression in KM12SM cells and found that expression of metallothionein (MT) mRNA increased markedly by indirect co-culture of KM12SM cells with MSCs. Additionally, in an orthotopic nude mouse model of colon cancer, MT mRNA expression levels were shown to be higher in the tumors produced by KM12SM cells mixed with MSCs than in the tumors produced by KM12SM cells alone. MTs comprise a family of low-molecular-weight, cysteine-rich intracellular proteins that are associated with protection against DNA damage, oxidative stress, and apoptosis. The potential role of MTs in carcinogenesis remains unknown. We examined MT expression in surgical specimens of human colon cancer and colon adenoma by immunohistochemistry. A total of 101 tumors were analyzed. MT immunoreactivity was detected in tumor cells and in atypical stromal cells. Atypical stromal cells with strong MT expression were found in invasive cancers, at the invasive edge, but not in mucosal cancers or adenomas. Levels of MT expression in tumor cells correlated inversely with disease stage. These findings suggest that the interaction between MSCs recruited into tumor stroma and the tumor cells of invasive colon cancers induces and depends on MT expression. Further studies are needed to clarify the specific effects of MTs on tumor cells and stromal cells.

Citation Format: Kei Shinagawa, Yasuhiko Kitadai, Ryo Yuge, Mieko Onoyama, Mayu Ohnishi, Shinji Tanaka, Wataru Yasui, Kazuaki Chayama. Interaction between bone marrow-derived mesenchymal stem cells and tumor cells induces metallothionein gene expression in human colon cancer. [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 4004. doi:10.1158/1538-7445.AM2013-4004