Abstract 5010: Activation of the notch signaling pathway confers a tumor-suppressive phenotype on melanoma-associated fibroblasts

Objectives. The tumor microenvironment (TME) is an emerging therapeutic target for cancer treatment. Cancer-associated fibroblasts (CAF) play a crucial role in cancer progression. We aim to target TME by altering intracellular signaling which determines the biological function of CAF. We have recently showed that the Notch signaling pathway likely functions as a molecular switch in controlling the tumor regulatory role of CAF in animal models and experimentally created “CAF”. Here, we investigated the status of Notch signaling in human melanoma-associated fibroblasts (MAF) versus their normal counterparts and tested whether manipulation of the Notch pathway activity in MAF alter their tumor-regulating function. Methods. We examined levels of Hes1, a canonical Notch target, in MAF of human malignant melanoma at different stages (I-IV) and fibroblasts in either adjacent or non-adjacent normal skin tissues using tissue microarray. MAF were isolated from human metastatic melanoma tissues. Notch pathway RT 2 -PCRArray and immunoblot were used to assess Notch pathway activity in MAF versus normal human dermal fibroblasts. Activation of Notch signaling pathway in MAF was achieved by lentiviral vector encoding active form of Notch1 (N IC ). The effect of Notch1-engineered MAF on melanoma growth was tested by in vitro co-cultures and in a mouse co-xenograft model (n=6/group). Tumor angiogenesis was analyzed by immunochemistry. Results. MAF expressed decreased levels of Hes1 compared with adjacent skin fibroblasts. Isolated MAF also exhibited lower Notch activity than normal human dermal fibroblasts. Notch1-engineered MAF significantly inhibited melanoma cell growth in vitro (p Conclusions. Notch pathway activity is down-regulated in MAF. Increase of Notch pathway activity confers MAF with inhibition to melanoma growth and tumor angiogenesis. Our study demonstrates that Notch signaling is a critical molecular switch in determining the tumor regulatory role of MAF and provides potential targets for cancer therapeutic interventions on the TME. Citation Format: Hongwei Shao, Mecker G. Moller, Long Cai, Leiming Zhang, Zhao-Jun Liu. Activation of the notch signaling pathway confers a tumor-suppressive phenotype on melanoma-associated fibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5010. doi:10.1158/1538-7445.AM2017-5010