P. P. Parikh1, H. Shao1, L. Cai1, M. Moller1, B. Issac2, R. Vazquez-Padron1, M. Owyong1, Z. Liu1,2 1University Of Miami,Surgery,Miami, FL, USA 2University Of Miami,Sylvester Comprehensive Cancer Center,Miami, FL, USA
Introduction: Mesenchymal stem cells-derived fibroblasts (MSC-DF) constitute a significant portion of stromal fibroblasts in the tumor microenvironment (TME) and are key modulators of tumor progression. However, the molecular mechanisms that determine their tumor regulatory function are poorly understood. Here, we uncover the Notch1 pathway as a molecular determinant that selectively controls the regulatory role of MSC-DF in melanoma metastasis.
Methods: MSC-DF were generated from bone marrow (BM)-derived MSC obtained from Notch1Flox/Flox and ROSAN1IC mice and transduced with Cre-GFP/Lentivirus or GFP/Lentivirus (control). Various MSC-DF were co-cultured or co-grafted with human melanoma cells (labeled with Luc2) in vitro or in vivo. Melanoma growth and metastasis in vivo were examined by measuring tumor size and IVIS scanning. cDNA microarray was employed to identify downstream targets of Notch1 signaling.
Results: We demonstrated that the Notch1 pathway’s activity is inversely correlated with the metastasis-regulating function of fibroblasts and can determine the metastasis-promoting or -suppressing phenotype of MSC-DF. When co-grafted with melanoma cells, MSC-DFNotch1-/- selectively promoted, while MSC-DFN1IC+/+ preferentially suppressed melanoma metastasis, but not growth, in mouse models. When co-cultured with metastatic melanoma cells in vitro, MSC-DFNotch1-/- supported, but MSC-DFN1IC+/+ inhibited melanoma cells to form spheroids. We also identified Wnt-induced secreted protein-1 (WISP-1) from MSC-DF as a key downstream secretory mediator of Notch1 signaling on melanoma metastasis.
Conclusion: These findings expand the repertoire of Notch1 signaling as a molecular switch in determining the tumor metastasis-regulating function of MSC-DF. We demonstrate that the Notch1—WISP-1 axis functions as a crucial molecular determinant in governing stromal regulation of melanoma metastasis; thus, establishing this axis as a potential therapeutic target for melanoma metastasis.