Verteporfin inhibits the persistent fibrotic phenotype of lesional scleroderma dermal fibroblasts.

Fibrosis is perpetuated by an autocrine, pro-adhesive signaling loop maintained by the synthetic and contractile abilities of myofibroblasts and the stiff, highly-crosslinked extracellular matrix. Transcriptional complexes that are exquisitely responsive to mechanotransduction include the co-activator YAP1, which regulates the expression of members of the CCN family of matricellular proteins such as CCN2 and CCN1. Although selective YAP1 inhibitors exist, the effect of these inhibitors on profibrotic gene expression in fibroblasts is largely unknown, and is the subject of our current study. Herein, we use genome-wide expression profiling, real-time polymerase chain reaction and Western blot analyses, cell migration and collagen gel contraction assays to assess the ability of a selective YAP inhibitor verteporfin (VP) to block fibrogenic activities in dermal fibroblasts from healthy individual human controls and those from isolated from fibrotic lesions of patients with diffuse cutaneous systemic sclerosis (dcSSc). In control fibroblasts, VP selectively reduced expression of fibrogenic genes and also blocked the ability of TGFbeta to induce actin stress fibers in dermal fibroblasts. VP also reduced the persistent profibrotic phenotype of dermal fibroblasts cultured from fibrotic lesions of patients with dcSSc. Our results are consistent with the notion that, in the future, YAP1 inhibitors may represent a novel, valuable method of treating fibrosis as seen in dcSSc.

Activation of cancer-associated fibroblasts is required for tumor neovascularization in a murine model of melanoma.

Metastatic melanoma is highly fatal. Within the tumor microenvironment, the role of cancer-associated fibroblasts (CAFs) in melanoma metastasis and progression is relatively understudied. The matricellular protein CCN2 (formerly termed connective tissue growth factor, CTGF) is overexpressed, in a fashion independent of BRAF mutational status, by CAFs in melanoma. Herein, we find, in human melanoma patients, that CCN2 expression negatively correlates with survival and positively correlates with expression of neovascularization markers. To assess the role of CAFs in melanoma progression, we used C57BL/6 mice expressing a tamoxifen-dependent cre recombinase expressed under the control of a fibroblast-specific promoter/enhancer (COL1A2) to delete CCN2 postnatally in fibroblasts. Mice deleted or not for CCN2 in fibroblasts were injected subcutaneously with B16-F10 melanoma cells. Loss of CCN2 in CAFs resulted in reduced CAF activation, as detected by staining with anti-α-smooth muscle actin antibodies, and reduced tumor-induced neovascularization, as detected by micro-computed tomography (micro-CT) and staining with anti-CD31 antibodies. CCN2-deficient B16(F10) cells were defective in a tubule formation/vasculogenic mimicry assay in vitro. Mice deleted for CCN2 in CAFs also showed impaired vasculogenic mimicry of subcutaneously-injected B16-F10 cells in vivo. Our results provide new insights into the cross-talk among different cell types in the tumor microenvironment and suggest CAFs play a heretofore unappreciated role by being essential for tumor neovascularization via the production of CCN2. Our data are consistent with the hypothesis that activated CAFs are essential for melanoma metastasis and that, due to its role in this process, CCN2 is a therapeutic target for melanoma.