CLIC4 regulates TGF-β-dependent myofibroblast differentiation to produce a cancer stroma

Abstract

Cancer stroma has a profound influence on tumor development and progression. The conversion of fibroblasts to activated myofibroblasts is a hallmark of reactive tumor stroma. Among a number of factors involved in this conversion, TGF-β has emerged as a major regulator. CLIC4, an integral protein in TGF-β signaling, is highly upregulated in stroma of multiple human cancers, and overexpression of CLIC4 in stromal cells enhances the growth of cancer xenografts. In this study we show that conditioned media from tumor cell lines induces expression of both CLIC4 and the myofibroblast marker alpha smooth muscle actin (α-SMA) in stromal fibroblasts via TGF-β signaling. Genetic ablation of CLIC4 in primary fibroblasts prevents or reduces constitutive or TGF-β induced expression of α-SMA and extracellular matrix components that are markers of myofibroblasts. CLIC4 is required for the activation of p38 Map Kinase by TGF-β, a pathway that signals myofibroblast conversion in stromal cells. This requirement involves the interaction of CLIC4 with PPM1a, the selective phosphatase of activated p-38. Conditioned media from fibroblasts overexpressing CLIC4 increases tumor cell migration and invasion in a TGF-β dependent manner and promotes epithelial to mesenchymal transition indicating that high stromal CLIC4 serves to enhance tumor invasiveness and progression. Thus, CLIC4 is significantly involved in the development of a nurturing tumor microenvironment by enhancing TGF-β signaling in a positive feedback loop. Targeting CLIC4 in tumor stroma should be considered as a strategy to mitigate some of the tumor enhancing effects of the cancer stroma.

Chloride intracellular channel 4 is required for maturation of the cerebral collateral circulation

“…Although little is known about how CLIC4 and VEGF-A interact, evidence suggests TGF␤ signaling may be involved. CLIC4 is both regulated by and is an enhancer for TGF␤ signaling (36,37). After TGF␤ receptor/ALK5 activation, CLIC4 complexes with transcription factor Schnurri-2 and translocates to the nucleus, where the complex protects against deactivation of TGF␤-induced phosphorylated Smad2/3, thereby enhancing TGF␤ signaling (37).…”

Tumor-Derived Osteopontin Reprograms Normal Mammary Fibroblasts to Promote Inflammation and Tumor Growth in Breast Cancer

“…1B and C). CAFs, characterized also by their expression of aSMA, are known to be similar to myofibroblasts that are active in wound repair, where their coordinated motility and contraction is crucial in the process of wound closure (23)(24)(25). We therefore performed an in vitro wound closure assay to test the activation of NMFs by tumor cell-secreted factors.…”

Patient-derived Interstitial Fluids and Predisposition to Aggressive Sporadic Breast Cancer through Collagen Remodeling and Inactivation of p53

“…CLIC4 is one the top up-regulated genes in MDA-MB-231 by high score PSF. CLIC4 has been identified as the gene most up-regulated in fibroblasts upon exposure to TGF-β1 and was found to be required for the differentiation of fibroblasts to myofibroblasts (17). Considering that myofibroblasts are responsible for the deposition of collagen, CLIC4 is a prime candidate to contribute to the increased deposition of collagen observed upon exposure to high score PSF.…”