Maia Nestor-Martin

The immune landscape of healthy prostate and its alterations during prostate cancer (PCa) progression remain poorly characterized. Using scRNA-sequencing and multiparametric flow-cytometry analysis, we comprehensively characterized immune cells in wild-type and PTEN^(i)pe-/- mouse prostates, a model that closely recapitulates human PCa. PCa in PTEN^(i)pe-/- is marked by the recruitment of tumor-associated neutrophils (TANs), which represent the dominant immune cell population and resolved into eight distinct states, Trem2⁺ tumor-associated-macrophages (TAMs), and exhausted CD8⁺ T cells. Trem2⁺ TAMs differ from the three main resident macrophage populations in the healthy prostate, exhibiting a strong metabolic and immunosuppressive signature, likely driven by the MIF/HIF1A-signaling axis. This study provides the first detailed characterization of immune cells in the healthy mouse prostate and reveals changes in the immune landscape associated with prostate cancer progression.

Innate B-1 cells constitute a self-maintained layer of defense for early detection of bacteria, clearance of apoptotic cell debris, and removal of autoantigens driving autoimmunity. B-1 cells are originated from fetal tissues, but, as opposed to B-2 cells, the molecular mechanisms behind their development and homeostatic maintenance remain largely unknown. Here, we demonstrate that posttranscriptional regulation by the RNA binding protein HuR is essential for the homeostatic self-replenishment of innate B-1a cells, the expansion of B-1 cell clones targeting self-antigens, and the production of natural autoantibodies. HuR KO B-1 cells fail to express the high levels of surface B-cell receptor (BCR), TACI, and BAFFR required for tonic signaling and cell survival. At the molecular level, HuR promotes the translation of messenger RNAs encoding the IgM heavy chain and modules, in a direct or indirect manner, the expression of TACI and BAFFR. In summary, we reveal the need for posttranscriptional regulation in BCR expression, tonic signaling, and homeostatic maintenance of functional innate B-1 cells.