Tumor Specific Recruitment and Reprogramming of Mesenchymal Stem Cells in Tumorigenesis.

Non-neoplastic stromal cells harvested from patient tumors were identified as tumor-derived mesenchymal stem cells (MSCs) by their multipotential capacity to differentiate into adipocytes, osteoblasts, and chondrocytes and by the expression of MSC specific cell surface markers. These procedures yielded also epithelial cancer cells and their counterpart MSC from gastric carcinoma (GSC1) and lung carcinoma (LC2). While the LC2 cancer cell growth is independent of their LC-MSC, the GSC1 cancer cell growth is critically dependent on the presence of their counterpart GSC-MSC or their conditioned medium (CM). The fact that none of the various other tumor-derived MSCs was able to restore the specific effect of GSC-MSC on GSC1 cancer cell growth suggests specificity of tumor-derived MSC, which are specifically recruited and "educated"/reprogrammed by the cancer cells to support tumor growth. Using cytokine array analysis, we were able to demonstrate that GSC1 cell growth is mediated through hepatocyte growth factor (HGF)/c-MET signaling pathway which is activated exclusively by HGF secreted from GSC-MSC. An innovative approach demonstrates GSC1-mediated specific tropism of "naïve" MSC from the adjacent tissue in a tumor specific manner to support tumor progression. The results suggest that specific tumor tropic "naïve" MSC are reprogrammed in a tumor-specific manner to support gastric tumor progression. Understanding the mechanisms involved in the interactions of the tumor cancer cells and tumor-derived MSC will constitute the basis for developing multimodal anticancer therapeutic strategies that will also take into account the specific tumor tropism properties of MSC and their reprogramming.