Converting melanoma-associated fibroblasts into a tumor-suppressive phenotype by increasing intracellular Notch1 pathway activity.

Hongwei Shao,Kerstin Yu,Zhao-Jun Liu,Rochelle Prokupets,Long Cai,Connor Costa,Cuixia Yang,Nga Le,Mecker Moller,Salvatore V Pizzo

doi:10.1371/journal.pone.0248260

Abstract

Cancer-associated fibroblasts (CAFs) play a crucial role in cancer progression, drug resistance and tumor recurrence. We have recently shown that the Notch pathway determines the tumor-regulatory role of experimentally created ‘CAFs’. Here, we examined the status of Notch signaling in human melanoma-associated fibroblasts (MAFs) versus their normal counterparts and tested whether manipulation of the Notch pathway activity in MAFs alters their tumor-regulatory function. Using tissue microarrays, we found that MAFs exhibit decreased Notch pathway activity compared with normal fibroblasts in adjacent and non-adjacent skin. Consistently, MAFs isolated from human metastatic melanoma exhibited lower Notch activity than did normal human fibroblasts, demonstrating that Notch pathway activity is low in MAFs. We then investigated the effect of increasing Notch pathway activity in MAF on melanoma growth in co-cultures and in a mouse co-graft model. We found that activation of the Notch pathway in MAFs significantly restricted melanoma cell growth in vitro and suppressed melanoma skin growth and tumor angiogenesis in vivo. Our study demonstrates that the Notch signaling is inhibited in MAFs. Increase of Notch pathway activity can confer tumor-suppressive function on MAFs. Thus, targeting melanoma by activating Notch signaling in MAF may represent a novel therapeutic approach.

Highlights

Tumor stromal fibroblasts, known as cancer-associated fibroblasts (CAFs), are the major cellular components of the reactive tumor stroma
Human melanoma-associated fibroblasts (MAFs) were isolated from three human skin melanoma specimens, which were collected from three adult patients who were above 18 years old, according to the principles expressed in the Declaration of Helsinki and using the protocol approved by the committee of institutional review board (IRB) of the University of Miami (IRB # 20100200)
Differential status of Notch signaling in MAFs and normal skin fibroblasts To study the status of Notch signaling in natural MAFs and their normal counterparts, a tissue microarray approach with immunofluorescence (IF) was undertaken to examine levels of Hes1, a canonical Notch target, in MAFs of human melanoma at different stages (I-III) and fibroblasts located at adjacent and non-adjacent normal skin tissues

Summary

Introduction

Known as cancer-associated fibroblasts (CAFs), are the major cellular components of the reactive tumor stroma. CAFs and tumor cells co-evolve as critical components in the regulation of tumor progression, by eliciting a variety of ECM remodeling enzymes and exosomes, structural components of the extracellular matrix (ECM), and soluble factors [1, 2]. CAFs influence cancer organ-specific metastasis [3]. Targeting melanoma by activating Notch in fibroblasts

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Conclusion