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A Feed-Forward Mechanosignaling Loop Confers Resistance to Therapies Targeting the MAPK Pathway in BRAF-Mutant Melanoma

Abstract : Aberrant extracellular matrix (ECM) deposition and stiffening is a physical hallmark of several solid cancers and is associated with therapy failure. BRAF-mutant melanomas treated with BRAF and MEK inhibitors almost invariably develop resistance that is frequently associated with transcriptional reprogramming and a de-differentiated cell state. Melanoma cells secrete their own ECM proteins, an event that is promoted by oncogenic BRAF inhibition. Yet, the contribution of cancer cell-derived ECM and tumor mechanics to drug adaptation and therapy resistance remains poorly understood. Here, we show that melanoma cells can adapt to targeted therapies through a mechanosignaling loop involving the autocrine remodeling of a drug-protective ECM. Analyses revealed that therapy-resistant cells associated with a mesenchymal dedifferentiated state displayed elevated responsiveness to collagen stiffening and force-mediated ECM remodeling through activation of actin-dependent mechanosensors Yes-associated protein (YAP) and myocardin-related transcription factor (MRTF). Short-term inhibition of MAPK pathway also induced mechanosignaling associated with deposition and remodeling of an aligned fibrillar matrix. This provided a favored ECM reorganization that promoted tolerance to BRAF inhibition in a YAP- and MRTF-dependent manner. Matrix remodeling and tumor stiffening were also observed in vivo upon exposure of BRAF-mutant melanoma cell lines or patient-derived xenograft models to MAPK pathway inhibition. Importantly, pharmacologic targeting of YAP reversed treatment-induced excessive collagen deposition, leading to enhancement of BRAF inhibitor efficacy. We conclude that MAPK pathway targeting therapies mechanically reprogram melanoma cells to confer a drug-protective matrix environment. Preventing melanoma cell mechanical reprogramming might be a promising therapeutic strategy for patients on targeted therapies. SIGNIFICANCE: These findings reveal a biomechanical adaptation of melanoma cells to oncogenic BRAF pathway inhibition, which fuels a YAP/MRTF-dependent feed-forward loop associated with tumor stiffening, mechanosensing, and therapy resistance. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/10/1927/F1.large.jpg.
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Submitted on : Friday, November 20, 2020 - 11:27:12 AM
Last modification on : Friday, November 20, 2020 - 1:58:02 PM

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Christophe Girard, Margaux Lecacheur, Rania Ben Jouira, Ilona Berestjuk, Serena Diazzi, et al.. A Feed-Forward Mechanosignaling Loop Confers Resistance to Therapies Targeting the MAPK Pathway in BRAF-Mutant Melanoma. Cancer Research, American Association for Cancer Research, 2020, 80 (10), pp.1927-1941. ⟨10.1158/0008-5472.CAN-19-2914⟩. ⟨inserm-02889519⟩

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