Production of Superoxide Anions by Keratinocytes Initiates P. acnes-Induced Inflammation of the Skin

Acne vulgaris is a chronic inflammatory disorder of the sebaceous follicles. Propionibacterium acnes (P. acnes), a gram-positive anareobic bacterium, plays a critical role in the development of these inflammatory lesions. This study aimed at determining whether reactive oxygen species (ROS) are produced by keratinocytes upon P. acnes infection, dissecting the mechanism of this production, and investigating how this phenomenon integrates in the general inflammatory response induced by P. acnes. In our hands, ROS, and especially superoxide anions (O2•−), were rapidly produced by keratinocytes upon stimulation by P. acnes surface proteins. In P. acnes-stimulated keratinocytes, O2•− was produced by NAD(P)H oxidase through activation of the scavenger receptor CD36. O2•− was dismuted by superoxide dismutase to form hydrogen peroxide which was further detoxified into water by the GSH/GPx system. In addition, P. acnes-induced O2•− abrogated P. acnes growth and was involved in keratinocyte lysis through the combination of O2•− with nitric oxide to form peroxynitrites. Finally, retinoic acid derivates, the most efficient anti-acneic drugs, prevent O2•− production, IL-8 release and keratinocyte apoptosis, suggesting the relevance of this pathway in humans

ROCK 2 inhibition triggers the collective invasion of colorectal adenocarcinomas

International audienceThe metastatic progression of cancer is a multi-step process initiated by the local invasion of the peritumoral stroma. To identify the mechanisms underlying colorectal carcinoma (CRC) invasion, we collected live human primary cancer specimens at the time of surgery and monitored them ex vivo. This revealed that conventional adenocarcinomas undergo collective invasion while retaining their epithelial glandular architecture with an inward apical pole delineating a luminal cavity. To identify the underlying mechanisms , we used microscopy-based assays on 3D organotypic cultures of Caco-2 cysts as a model system. We performed two siRNA screens targeting Rho-GTPases effectors and guanine nucleotide exchange factors. These screens revealed that ROCK2 inhibition triggers the initial leader/follower polarization of the CRC cell cohorts and induces collective invasion. We further identified FARP2 as the Rac1 GEF necessary for CRC collective invasion. However, FARP2 activation is not sufficient to trigger leader cell formation and the concomitant inhibition of Myosin-II is required to induce invasion downstream of ROCK2 inhibition. Our results contrast with ROCK pro-invasive function in other cancers, stressing that the molecular mechanism of metastatic spread likely depends on tumour types and invasion mode

Nucleoside diphosphate kinase D (NME4) is the first mitochondrial metastasis suppressor

International audienceNDP-kinase D (NME4) is a mitochondrial protein with multiple functions in bioenergetics and signaling. NME4 mainly localizes to the mitochondrial intermembrane space, interacting with cardiolipin and the pro-fusion GTPase OPA1 at the inner membrane. Here, NME4 forms a metabolite channeling complex, generating GTP for maximal OPA1 efficiency and ADP to stimulate respiration. NME4 simultaneously interacts with outer membrane to favor intermembrane transfer of cardiolipin to the mitochondrial surface as a signal for mitophagy or apoptosis. Here, we deleted either its NDP kinase activity (H151N) or cardiolipin interaction (R90D) and expressed these mutants or wtNME4 in HeLa cells almost devoid of NME4 [1]. Both loss-of-function mutants independently led to similar, dominant-negative effects on mitochondrial structure and function: a metabolic shift with reduced complex-I-linked respiration and Krebs cycle activity together with increased aerobic glycolysis, downregulation of some mitochondrial proteins, altered sensitivity of mitochondrial permeability transition, increased oxidative stress, and mild energy stress (upregulated mitochondrial creatine and adenylate kinases and AMPK-signaling). Consistent with disturbed GTP-fueling of OPA1, mitochondrial network and mass were reduced. Importantly, mitochondrial alterations triggered a pro-invasive reprogramming that favors metastasis: overexpression of metastasis-related proteins, loss of cell-cell contacts, promoted epithelial-mesenchymal transition, and increased migratory/invasive potential. More metastases developed in immune-compromised mice when injected with mutant cells. In human cancer, NME4 expression is negatively associated with markers of epithelial-mesenchymal transition or tumor aggressiveness, and represents a good prognosis factor for beneficial clinical outcome. Our study emphasizes a new role of mitochondria and mitochondria-nuclear retrograde signaling in metastasis.[1] M.L. Lacombe et al., The mitochondrially-localized nucleoside diphosphate kinase D (NME4) is a novel metastasis suppressor, BMC Biology, 19 (2022) 228-257

Cell clusters adopt a collective amoeboid mode of migration in confined nonadhesive environments

International audienceCell migration is essential to living organisms and deregulated in cancer. Single cell’s migration ranges from traction-dependent mesenchymal motility to contractility-driven propulsive amoeboid locomotion, but collective cell migration has only been described as a focal adhesion–dependent and traction-dependent process. Here, we show that cancer cell clusters, from patients and cell lines, migrate without focal adhesions when confined into nonadhesive microfabricated channels. Clusters coordinate and behave like giant super cells, mobilizing their actomyosin contractility at the rear to power their migration. This polarized cortex does not sustain persistent retrograde flows, of cells or actin, like in the other modes of migration but rather harnesses fluctuating cell deformations, or jiggling. Theoretical physical modeling shows this is sufficient to create a gradient of friction forces and trigger directed cluster motion. This collective amoeboid mode of migration could foster metastatic spread by enabling cells to cross a wide spectrum of environments

The mitochondrially-localized nucleoside diphosphate kinase D (NME4) is a novel metastasis suppressor

International audienceAbstract Background Mitochondrial nucleoside diphosphate kinase (NDPK-D, NME4, NM23-H4) is a multifunctional enzyme mainly localized in the intermembrane space, bound to the inner membrane. Results We constructed loss-of-function mutants of NDPK-D, lacking either NDP kinase activity or membrane interaction and expressed mutants or wild-type protein in cancer cells. In a complementary approach, we performed depletion of NDPK-D by RNA interference. Both loss-of-function mutations and NDPK-D depletion promoted epithelial-mesenchymal transition and increased migratory and invasive potential. Immunocompromised mice developed more metastases when injected with cells expressing mutant NDPK-D as compared to wild-type. This metastatic reprogramming is a consequence of mitochondrial alterations, including fragmentation and loss of mitochondria, a metabolic switch from respiration to glycolysis, increased ROS generation, and further metabolic changes in mitochondria, all of which can trigger pro-metastatic protein expression and signaling cascades. In human cancer, NME4 expression is negatively associated with markers of epithelial-mesenchymal transition and tumor aggressiveness and a good prognosis factor for beneficial clinical outcome. Conclusions These data demonstrate NME4 as a novel metastasis suppressor gene, the first localizing to mitochondria, pointing to a role of mitochondria in metastatic dissemination