Abstract 1515: The role of the Notch/WISP-1 axis in determining the regulatory effect of mesenchymal stem cells on melanoma cell motility

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Purpose. Bone marrow (BM)-derived mesenchymal stem cells (MSC) are known to be recruited to the tumor tissues where they integrate into the reactive tumor stroma and play a critical role in regulating tumor cell behavior. However, the molecular mechanisms underlying the influential role of MSC for melanoma cell behavior remain poorly understood. We sought to identify the “molecular switch” controlling the regulatory effect of MSC on melanoma cell growth and migration. Methods. MSC from BM of Notch1Flox/Flox mice were cultured in MesenCult® media. Deletion of the Notch1 gene was achieved by transduction of MSC with Cre/Lentivirus. The role of Notch1-/– vs. Notch1+/+-MSC in modulating human melanoma cell behavior in vitro was examined by testing the effect of conditioned medium (CM) of MSC on melanoma cell growth and migration using MTT and Transwell® cell migration assays, respectively, and by counting the number of DsRed-melanoma cells in melanoma-MSC co-culture assay using flow cytometry. The downstream targets of the Notch1 signaling in MSC were screened by genome-wide gene microarray analysis. Expression of selected target gene was confirmed by immunoblotting assay. The biological function of the selected target in mediating the regulatory effect of the Notch1-/–MSC on melanoma cell growth and migration was examined through the reconstitution of target gene expression in Notch1-/–MSC and evaluated by testing the direct effect of supplemented recombinant protein encoding the target gene on melanoma cells. The mechanism underlying the regulatory effect of the Notch1 target on melanoma cell mobility was analyzed by PCR-Array specifically focused on exploring cell migration. Results. Notch1-/–MSC, either by CM or in co-culture, had little effect on melanoma cell proliferation, while the CM significantly promoted melanoma cell migration. Global gene expression profiling of Notch1-/– vs. Notch1+/+-MSC by microarray identified Wnt-induced secreted protein-1 (WISP-1) as a Notch1 downstream target gene. The Notch1 signaling-commanded regulatory effect of MSC on melanoma cell migration is partially mediated by modulating WISP-1 expression, since the CM of Notch1-/–MSC promoted melanoma cell motility, while the enhanced motility of melanoma cell was reversed by reconstituted overexpression of WISP-1 in Notch1-/–MSC. Consistently, supplement of γhWISP-1 inhibited melanoma cell migration, presumably via modulating Cdc42/PAK cascade. Conclusions. Our data reveal Notch1 signaling as a molecular switch controlling the regulatory role of MSC in modulating melanoma cell motility, and demonstrate that melanoma cell behavior can be determined by external signals emanating from the MSC. WISP-1 is a molecular relay in the transmission of Notch1 signaling, and may serve as a molecular target for melanoma therapeutic intervention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1515. doi:1538-7445.AM2012-1515