Matrix metalloproteinases (MMPs) are members of the metzincin group of proteases which share the conserved zinc-binding motif in their catalytic active site. It was originally thought that their main function is to degrade the various components of the extracellular matrix (ECM), yet recent studies have led us to appreciate their significance as regulators of extracellular tissue signalling networks. Due to the broad spectrum of their substrate specificity, MMPs contribute to the homeostasis of many tissues and participate in several physiological processes, such as bone remodelling, angiogenesis, immunity and wound healing. MMP activity is tightly controlled at the level of transcription, pro-peptide activation and inhibition by tissue inhibitors of MMPs. Dysregulated MMP activity leads to pathological conditions such as arthritis, inflammation and cancer, thus highlighting MMPs as promising therapeutic targets. Analysis of MMP mutant mice has proved to be an essential tool for the identification of novel functions and interactions of single MMP members. Advancing our understanding of the MMP contribution to tissue homeostasis will lead us to identify causal relationships between their dysregulation and the development of disease pathologies, thus guiding us to successful MMP-directed therapies.

Aims Cardiac immune-related adverse events (irAEs) from immune checkpoint inhibition (ICI) targeting programmed death 1 (PD1) are of growing concern. Once cardiac irAEs become clinically manifest, fatality rates are high. Cardio-oncology aims to prevent detrimental effects before manifestation of severe complications by targeting early pathological changes. We therefore aimed to investigate early consequences of PD1 inhibition for cardiac integrity to prevent the development of overt cardiac disease. Methods and results We investigated cardiac-specific consequences from anti-PD1 therapy in a combined biochemical and in vivo phenotyping approach. Mouse hearts showed broad expression of the ligand PDL1 on cardiac endothelial cells as a main mediator of immune-crosstalk. Using a novel melanoma mouse model, we assessed that anti-PD1 therapy promoted myocardial infiltration with CD4+ and CD8+ T cells, the latter being markedly activated. Left ventricular (LV) function was impaired during pharmacological stress, as shown by pressure–volume catheterization. This was associated with a dysregulated myocardial metabolism, including the proteome and the lipidome. Analogous to the experimental approach, in patients with metastatic melanoma (n = 7) receiving anti-PD1 therapy, LV function in response to stress was impaired under therapy. Finally, we identified that blockade of tumour necrosis factor alpha (TNFα) preserved LV function without attenuating the anti-cancer efficacy of anti-PD1 therapy. Conclusions Anti-PD1 therapy induces a disruption of cardiac immune homeostasis leading to early impairment of myocardial functional integrity, with potential prognostic effects on the growing number of treated patients. Blockade of TNFα may serve as an approach to prevent the manifestation of ICI-related cardiotoxicity.

EGFR requires ADAM17 activity to preserve skin barrier homeostasis.

Recessive dystrophic epidermolysis bullosa (RDEB) is a genetic skin fragility disorder characterized by injury-driven blister formation, progressive soft-tissue fibrosis, and a highly elevated risk of early-onset aggressive cutaneous squamous cell carcinoma (cSCC). However, the mechanisms underlying the unusually rapid progression of RDEB to cSCC are unknown. In this study, we investigated the contribution of injury-induced skin alterations to cSCC development by using a genetic model of RDEB and organotypic skin cultures. Analysis of RDEB patient samples suggested that premalignant changes to the dermal microenvironment drive tumor progression, which led us to subject a collagen VII hypomorphic mouse model of RDEB to chemical carcinogenesis. Carcinogen-treated RDEB mice developed invasive tumors phenocopying human RDEB-cSCC, whereas wild-type mice formed papillomas, indicating that the aggressiveness of RDEB-cSCC is mutation-independent. The inherent structural instability of the RDEB dermis, combined with repeated injury, increased the bioavailability of TGFb, which promoted extracellular matrix production, cross-linking, thickening of dermal fibrils, and tissue stiffening. The biophysically altered dermis increased myofibroblast activity and integrin b1/pFAK/pAKT mechanosignaling in tumor cells, further demonstrating that cSCC progression is governed by pre-existing injury-driven changes in the RDEB tissue microenvironment. Treatment of three-dimensional organotypic RDEB skin cultures with inhibitors of TGFb signaling, lysyl oxidase, or integrin b1-mediated mechanosignaling reduced or bypassed tissue stiffness and limited tumor cell invasion. Collectively, these findings provide a new mechanism by which RDEB tissue becomes malignant and offer new druggable therapeutic targets to prevent cSCC onset. Cancer Res; 76(4); 940-51. Ó2015 AACR.