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Background and Purpose Experimental Approach Key Results Conclusion and implication Triple‐negative breast cancer (TNBC) has poorer outcomes than other breast cancers (BC), including HER2+ BC. Cathepsin D (CathD) is a poor prognosis marker overproduced by BC cells, hypersecreted in the tumour microenvironment with tumour‐promoting activity. Here, we characterized the immunomodulatory activity of the anti‐CathD antibody F1 and its improved Fab‐aglycosylated version (F1M1) in immunocompetent mouse models of TNBC (C57BL/6 mice harbouring E0771 cell grafts) and HER2‐amplified BC (BALB/c mice harbouring TUBO cell grafts).CathD expression was evaluated by western blotting and immunofluorescence, and antibody binding to CathD by ELISA. Antibody anti‐tumour efficacy was investigated in mouse models. Immune cell recruitment and activation were assessed by immunohistochemistry, immunophenotyping, and RT‐qPCR.F1 and F1M1 antibodies remodelled the tumour immune landscape. Both antibodies promoted innate antitumour immunity by preventing the recruitment of immunosuppressive M2‐polarized tumour‐associated macrophages (TAMs) and by activating natural killer cells in the tumour microenvironment of both models. This translated into a reduction of T‐cell exhaustion markers in the tumour microenvironment that could be locally supported by enhanced activation of anti‐tumour antigen‐presenting cell (M1‐polarized TAMs and cDC1 cells) functions. Both antibodies inhibited tumour growth in the highly‐immunogenic E0771 model, but only marginally in the immune‐excluded TUBO model, indicating that anti‐CathD immunotherapy is more relevant for BC with a high immune cell infiltrate, as often observed in TNBC.Anti‐CathD antibody‐based therapy triggers the anti‐tumour innate and adaptive immunity in preclinical models of BC and is a promising immunotherapy for immunogenic TNBC. [ABSTRACT FROM AUTHOR]

Melanoma is a highly aggressive cancer endowed with a unique capacity of rapidly metastasizing, which is fundamentally driven by aberrant cell motility behaviors. Discovering "migrastatics" targets, specifically controlling invasion and dissemination of melanoma cells during metastasis, is therefore of primary importance. Here, we uncover the prominent expression of the plasma membrane TRPV2 calcium channel as a distinctive feature of melanoma tumors, directly related to melanoma metastatic dissemination. In vitro as well as in vivo, TRPV2 activity is sufficient to confer both migratory and invasive potentials, while conversely TRPV2 silencing in highly metastatic melanoma cells prevents aggressive behavior. In invasive melanoma cells, TRPV2 channel localizes at the leading edge, in dynamic nascent adhesions, and regulates calcium‐mediated activation of calpain and the ensuing cleavage of the adhesive protein talin, along with F‐actin organization. In human melanoma tissues, TRPV2 overexpression correlates with advanced malignancy and poor prognosis, evoking a biomarker potential. Hence, by regulating adhesion and motility, the mechanosensitive TRPV2 channel controls melanoma cell invasiveness, highlighting a new therapeutic option for migrastatics in the treatment of metastatic melanoma. Synopsis: The mechanosensitive TRPV2 channel positively regulates the invasive potential and metastatic dissemination of melanoma cells, providing a new biomarker and potential migrastatic target for cutaneous metastatic melanoma. TRPV2 is predominantly expressed in metastatic melanoma cells and tissues where it stands out as the most expressed calcium channel.Malignant melanoma tumor cells harbor active TRPV2 channels at their surface that drive their invasive behavior and metastatic potential.Mechanistically, TRPV2 controls melanoma cell dissemination by activating the Ca2+‐sensitive protease calpain and acting on nascent adhesion structures dynamics.In human melanoma, TRPV2 expression is exacerbated compared to benign nevi and associated with poor survival. [ABSTRACT FROM AUTHOR]

Triple‐negative breast cancer (TNBC) is the most aggressive breast cancer subtype and lacks specific targeted therapeutic agents. The current mechanistic evidence from cell‐based studies suggests that the matricellular protein SPARC has a tumor‐promoting role in TNBC; however, data on the clinical relevance of SPARC expression/secretion by tumor and stromal cells in TNBC are limited. Here, we analyzed by immunohistochemistry the prognostic value of tumor and stromal cell SPARC expression in 148 patients with non‐metastatic TNBC and long follow‐up (median: 5.4 years). We also quantified PD‐L1 and PD‐1 expression. We detected SPARC expression in tumor cells (42.4%), cancer‐associated fibroblasts (CAFs; 88.1%), tumor‐associated macrophages (77.1%), endothelial cells (75.2%) and tumor‐infiltrating lymphocytes (9.8%). Recurrence‐free survival was significantly lower in patients with SPARC‐expressing CAFs. Multivariate analysis showed that SPARC expression in CAFs was an independent prognostic factor. We also detected tumor and stromal cell SPARC expression in TNBC cytosols, and in patient‐derived xenografts and cell lines. Furthermore, we analyzed publicly available single‐cell mRNA sequencing data and found that in TNBC, SPARC is expressed by different CAF subpopulations, including myofibroblasts and inflammatory fibroblasts that are involved in tumor‐related processes. We then showed that fibroblast‐secreted SPARC had a tumor‐promoting role by inhibiting TNBC cell adhesion and stimulating their motility and invasiveness. Overall, our study demonstrates that SPARC expression in CAFs is an independent prognostic marker of poor outcome in TNBC. Patients with SPARC‐expressing CAFs could be eligible for anti‐SPARC targeted therapy. [ABSTRACT FROM AUTHOR]

Resistance to BRAF/MEK inhibitor therapy in BRAFV600‐mutated advanced melanoma remains a major obstacle that limits patient benefit. Microenvironment components including the extracellular matrix (ECM) can support tumor cell adaptation and tolerance to targeted therapy; however, the underlying mechanisms remain poorly understood. Here, we investigated the process of matrix‐mediated drug resistance (MMDR) in response to BRAFV600 pathway inhibition in melanoma. We demonstrate that physical and structural cues from fibroblast‐derived ECM abrogate anti‐proliferative responses to BRAF/MEK inhibition. MMDR is mediated by drug‐induced linear clustering of phosphorylated DDR1 and DDR2, two tyrosine kinase collagen receptors. Depletion and pharmacological targeting of DDR1 and DDR2 overcome ECM‐mediated resistance to BRAF‐targeted therapy. In xenografts, targeting DDR with imatinib enhances BRAF inhibitor efficacy, counteracts drug‐induced collagen remodeling, and delays tumor relapse. Mechanistically, DDR‐dependent MMDR fosters a targetable pro‐survival NIK/IKKα/NF‐κB2 pathway. These findings reveal a novel role for a collagen‐rich matrix and DDR in tumor cell adaptation and resistance. They also provide important insights into environment‐mediated drug resistance and a preclinical rationale for targeting DDR signaling in combination with targeted therapy in melanoma. Synopsis: Resistance to MAPK targeted therapy remains a major challenge in melanoma management. This study shows that BRAF/MEK inhibitor combination induces collagen remodeling that fosters activation of Discoidin Domain Receptors (DDR) and turns on a drug tolerant pathway. Targeting DDR overcomes this pathway. Adhesion of BRAF‐mutated melanoma cells to extracellular matrix generated from melanoma associated fibroblasts (MAF) confers tolerance to BRAF and MEK inhibition.Collagen receptors DDR promote tumor cell survival and matrix‐mediated drug resistance (MMDR) to combined MAPK targeted agents through NIK and non‐canonical NFκB2 signaling.DDR inhibition increases response to oncogenic BRAF inhibition, suppresses therapy‐induced collagen remodeling and induces tumor cell death in melanoma xenografts.Triple‐drug combination using BRAF/MEK inhibitors and DDR inhibitor such as imatinib, a clinically approved drug for leukemia, is proposed as a novel therapeutic strategy against disease relapse. [ABSTRACT FROM AUTHOR]

CD1a expression is considered one of the major characteristics qualifying in vitro human dendritic cells (DCs) during their generation process. Here, we report that CD1A transcription is regulated by a mechanism involving the long and short isoforms of CD99. Using a lentiviral construct encoding for a CD99 short hairpin RNA, we were able to inhibit CD99 expression in human primary DCs. In such cells, CD1a membrane expression increased and CD1A transcripts were much higher in abundance compared to cells expressing CD99 long form (CD99LF). We also show that CD1A transcription is accompanied by a switch in expression from CD99LF to expression at comparable levels of both CD99 isoforms during immature DCs generation in vitro. We demonstrate that CD99LF maintains a lower level of CD1A transcription by up-regulating the phosphorylated form of the ATF-2 transcription factor and that CD99 short form (SF) is required to counteract this regulatory mechanism. Elucidation of the molecular mechanisms related to CD99 alternative splicing will be very helpful to better understand the transcriptional regulatory mechanism of CD1a molecules during DCs differentiation and its involvement in the immune response. [ABSTRACT FROM AUTHOR]

Enhanced apoptosis of BCG-infected macrophages has been shown to induce stronger dendritic cell-mediated cross-priming of T cells, leading to higher protection against tuberculosis ( TB). Uncovering host effectors underlying BCG-induced apoptosis may then prove useful to improve BCG efficacy through priming macrophage apoptosis. Her we report that BCG-mediated apoptosis of human macrophages relies on FOXO3 transcription factor activation. BCG induced a significant apoptosis of THP1 ( TDMs) and human monocytes ( MDMs)-derived macrophages when a high moi was used, as shown by annexin V/7- AAD staining. BCG-induced apoptosis was associated with dephosphorylation of the prosurvival activated threonine kinase ( Akt) and its target FOXO3. Cell fractionation and immunofluorescence microscopy showed translocation of FOXO3 to the nucleus in BCG-infected cells, concomitantly with an increase of FOXO3 transcriptional activity. Moreover, FOXO3 expression knock-down by small interfering RNA ( siRNA) partially inhibited the BCG-induced apoptosis. Finally, real-time quantitative PCR ( qRT- PCR) analysis of the expression profile of BCG-infected macrophages showed an upregulation of two pro-apoptotic targets of FOXO3, NOXA and p53 upregulated modulator of apoptosis ( PUMA). Our results thus indicate that FOXO3 plays an important role in BCG-induced apoptosis of human macrophages and may represent a potential target to improve vaccine efficacy through enhanced apoptosis-mediated cross-priming of T cells. [ABSTRACT FROM AUTHOR]