B7-H3 Suppresses Antitumor Immunity via the CCL2–CCR2–M2 Macrophage Axis and Contributes to Ovarian Cancer Progression

New approaches beyond PD-1/PD-L1 inhibition are required to target the immunologically diverse tumor microenvironment (TME) in high-grade serous ovarian cancer (HGSOC). In this study, we explored the immunosuppressive effect of B7-H3 (CD276) via the CCL2–CCR2–M2 macrophage axis and its potential as a therapeutic target. Transcriptome analysis revealed that B7-H3 is highly expressed in PD-L1–low, nonimmunoreactive HGSOC tumors, and its expression negatively correlated with an IFNγ signature, which reflects the tumor immune reactivity. In syngeneic mouse models, B7-H3 (Cd276) knockout (KO) in tumor cells, but not in stromal cells, suppressed tumor progression, with a reduced number of M2 macrophages and an increased number of IFNγ⁺CD8⁺ T cells. CCL2 expression was downregulated in the B7-H3 KO tumor cell lines. Inhibition of the CCL2–CCR2 axis partly negated the effects of B7-H3 suppression on M2 macrophage migration and differentiation, and tumor progression. In patients with HGSOC, B7-H3 expression positively correlated with CCL2 expression and M2 macrophage abundance, and patients with B7-H3–high tumors had fewer tumoral IFNγ⁺CD8⁺ T cells and poorer prognosis than patients with B7-H3–low tumors. Thus, B7-H3 expression in tumor cells contributes to CCL2–CCR2–M2 macrophage axis–mediated immunosuppression and tumor progression. These findings provide new insights into the immunologic TME and could aid the development of new therapeutic approaches against the unfavorable HGSOC phenotype

Optimizing Nervous System-Specific Gene Targeting with Cre Driver Lines: Prevalence of Germline Recombination and Influencing Factors.

The Cre-loxP system is invaluable for spatial and temporal control of gene knockout, knockin, and reporter expression in the mouse nervous system. However, we report varying probabilities of unexpected germline recombination in distinct Cre driver lines designed for nervous system-specific recombination. Selective maternal or paternal germline recombination is showcased with sample Cre lines. Collated data reveal germline recombination in over half of 64 commonly used Cre driver lines, in most cases with a parental sex bias related to Cre expression in sperm or oocytes. Slight differences among Cre driver lines utilizing common transcriptional control elements affect germline recombination rates. Specific target loci demonstrated differential recombination; thus, reporters are not reliable proxies for another locus of interest. Similar principles apply to other recombinase systems and other genetically targeted organisms. We hereby draw attention to the prevalence of germline recombination and provide guidelines to inform future research for the neuroscience and broader molecular genetics communities

Linx Mediates Interaxonal Interactions and Formation of the Internal Capsule

SummaryDuring the development of forebrain connectivity, ascending thalamocortical and descending corticofugal axons first intermingle at the pallial-subpallial boundary to form the internal capsule (IC). However, the identity of molecular cues that guide these axons remains largely unknown. Here, we show that the transmembrane protein Linx is robustly expressed in the prethalamus and lateral ganglionic eminence-derived corridor and on corticofugal axons, but not on thalamocortical axons, and that mice with a null mutation of Linx exhibit a complete absence of the IC. Moreover, regional inactivation of Linx either in the prethalamus and LGE or in the neocortex leads to a failure of IC formation. Furthermore, Linx binds to thalamocortical projections, and it promotes outgrowth of thalamic axons. Thus, Linx guides the extension of thalamocortical axons in the ventral forebrain, and subsequently, it mediates reciprocal interactions between thalamocortical and corticofugal axons to form the IC