Gower, M. | bioRxiv Science

bioRxiv2025

Activated Notch1 Redirects CD4-Fated CD4+ CD8+ Precursors to the CD8 Lineage During Thymocyte Selection Without Causing T Cell Leukemia

Positive selection of CD4/CD8 double-positive (DP) thymocytes generates helper and cytotoxic T lineages whose CD4 or CD8 co-receptor expression matches their {beta} T cell receptor (TCR{beta}) specificity MHCII or MHCI, respectively. Notch1 signaling is critical for early T cell development and was suggested to regulate CD4/CD8 lineage determination during DP thymocyte selection. However, early studies expressing activated Notch1 in pre-DP progenitors did not resolve this question. Here we showed that CD4-Cre-mediated activation of canonical Rbpj-dependent Notch1 signalling potently skews DP selection to the CD8 lineage. We used a tamoxifen-inducible "time-stamp" model coupled with phenotypic staging to show that that activated Notch1 decreases generation of Gata3+ CD4+CD8lo selection intermediates during the earliest stages of DP selection, thereby preventing ThPOK induction and emergence of CD4 lineage cells. Finally, activated Notch1 efficiently re-directed DP thymocytes expressing MHCII-specific TCR{beta} into the CD8 lineage. These studies show that activated Notch1 acts early during DP selection to skew selection of CD4-fated, MHCII-specific DP precursors to the CD8 lineage.

immunology↗

bioRxiv2024

Host-derived Interleukin 1α induces an immunosuppressive tumor microenvironment via regulating monocyte-to-macrophage differentiation

Tumor-associated macrophages exhibit high heterogeneity and contribute to the establishment of an immunosuppressive tumor microenvironment (TME). Although numerous studies have demonstrated that extracellular factors promote macrophage proliferation and polarization, the regulatory mechanisms governing the differentiation process to generate phenotypically, and functionally diverse macrophage subpopulations remain largely unexplored. In this study, we examined the influence of interleukin 1 (IL-1) on the development of an immunosuppressive TME using orthotopic transplantation murine models of breast cancer. Deletion of host Il1 led to the rejection of inoculated congenic tumors. Single-cell sequencing analysis revealed that CX3CR1+ macrophage cells were the primary sources of IL-1 in the TME. The absence of IL-1 reprogrammed the monocyte-to-macrophage differentiation process within the TME, characterized by a notable decrease in the subset of CX3CR+ ductal-like macrophages and an increase in iNOS-expressing inflammatory cells. Comparative analysis of gene signatures in both human and mouse macrophage subsets suggested that IL-1 deficiency shifted the macrophage polarization from M2 to M1 phenotypes, leading to enhanced cytotoxic T lymphocyte activity in the TME. Importantly, elevated levels of IL-1 in human cancers were associated with worse prognosis following immunotherapy. These findings underscore the pivotal role of IL-1 in shaping an immune-suppressive TME through the regulation of macrophage differentiation and activity, highlighting IL-1 as a potential target for breast cancer treatment. TeaserInterleukin 1 dictates macrophage behavior, influencing an immunosuppressive microenvironment in breast cancer, suggesting it as a treatment target.

cancer biology↗