Intracellular osteopontin promotes the release of TNF by mast cells to restrain neuroendocrine prostate cancer.

Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer that emerges as tumors become resistant to hormone therapies or, rarely, arises de novo in treatment-naïve patients. The urgent need for effective therapies against NEPC is hampered by the limited knowledge of the biology governing this lethal disease. Based on our prior observations in the TRAMP spontaneous prostate cancer model, in which the genetic depletion of either mast cells (MCs) or the matricellular protein osteopontin (OPN) increases NEPC frequency, we tested the hypothesis that MCs can restrain NEPC through OPN production, using in vitro co-cultures between murine or human tumor cell lines and MCs, and in vivo experiments. We unveiled a role for the intracellular isoform of OPN (iOPN), so far neglected compared to the secreted isoform. Mechanistically, we unraveled that iOPN promotes TNF production in MCs via the TLR2/TLR4-MyD88 axis, specifically triggered by the encounter with NEPC cells. We found that MC-derived TNFin turn, hampered the growth of NEPC. We then identified the protein syndecan-1 (SDC1) as the NEPC-specific TLR2/TLR4 ligand that triggered this pathway. Interrogating published single-cell RNA-sequencing data we validated this mechanism in a different mouse model. Translational relevance of the results was provdied by in silco analyses of available human NEPC datasets, and by immunofluorescence on patient-derived adenocarcinoma and NEPC lesions. Overall, our results show that MCs actively inhibit NEPC, paving the way for innovative MC-based therapies for this fatal tumor. We also highlight SDC1 as a potential biomarker for incipient NEPC.

JMJD6 Shapes a Pro-tumor Microenvironment via ANXA1-Dependent Macrophage Polarization in Breast Cancer.

Breast cancer is the most common type of cancer in women worldwide, with the luminal subtype being the most widespread. Although characterized by better prognosis compared with other subtypes, luminal breast cancer is still considered a threatening disease due to therapy resistance, which occurs via both cell- and non-cell-autonomous mechanisms. Jumonji domain-containing 6, arginine demethylase and lysine hydroxylase (JMJD6) is endowed with a negative prognostic value in luminal breast cancer and, via its epigenetic activity, it is known to regulate many intrinsic cancer cell pathways. So far, the effect of JMJD6 in molding the surrounding microenvironment has not been explored.Here, we describe a novel function of JMJD6 showing that its genetic inhibition in breast cancer cells suppresses lipid droplet formation and ANXA1 expression, via estrogen receptor alpha and PPARα modulation. Reduction of intracellular ANXA1 results in decreased release in the tumor microenvironment (TME), ultimately preventing M2-type macrophage polarization and tumor aggressiveness. IMPLICATIONS: Our findings identify JMJD6 as a determinant of breast cancer aggressiveness and provide the rationale for the development of inhibitory molecules to reduce disease progression also through the remodeling of TME composition.