Biology subjects

Birocchi, F.

Publications and source records attributed to Birocchi, F..

3 recordsLinked to original sources

bioRxiv2025

Sialylated CD43 is a glyco-immune checkpoint for macrophage phagocytosis

Macrophages in the tumor microenvironment exert potent anti-tumorigenic activity through phagocytosis. Yet therapeutics that enhance macrophage phagocytosis have not improved outcomes in clinical trials for patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). To systematically identify regulators of phagocytosis, we performed genome-scale CRISPR knockout screens in human leukemia cells co-cultured with human monocyte-derived macrophages. Surprisingly, we found that whereas the classic "dont eat me" signal CD47 inhibited mouse macrophages, it did not inhibit phagocytosis by human macrophages. In contrast, the O-linked glycosylation and sialylation pathways were strong negative regulators of phagocytosis. In AML, the cell surface O-linked glycoprotein CD43 was the major effector of the O-linked glycosylation and sialylation pathways. Genetic deletion or antibody blockade of CD43 enhanced macrophage phagocytosis. This work highlights the importance of using human platforms to identify immune checkpoints, and nominates CD43 as a glyco-immune regulator of human macrophage phagocytosis.

cancer biology↗

bioRxiv2025

Drug tolerant persisters and immunotherapy persister cells exhibit cross-resistance and share common survival mechanisms

Persisters are a rare sub-population of tumor cells that survive anti-cancer therapy and are thought to be a major cause of recurrence. These cells have been identified following both drug- and immune-therapy but are generally considered to be distinct entities. Since both pharmacological agents and immune cells often kill via apoptosis, we tested a hypothesis that both types of cells survive based on reduced mitochondrial apoptotic sensitivity, which in turn would yield a similar and reciprocal multi-agent resistant phenotype. Supporting this hypothesis, we indeed observed that IPCs acquired a reduced sensitivity to multiple drug classes and radiotherapy, suggesting non-immune mechanisms are important in the survival of cancer cells after immunotherapy. Likewise, DTPs developed not only a reduced sensitivity to multiple drug classes and radiotherapy, but also acquired a reduced sensitivity to T cell killing. Both IPCs and DTPs developed a decreased sensitivity to mitochondrial apoptosis. A sub-population of IPCs downregulated antigen and upregulated PD-L1. Intriguingly, in the IPCs that didnt employ these mechanisms of resistance, a greater decrease in sensitivity to mitochondrial apoptosis was observed, suggesting that the presence or absence of a resistance mechanism can exert selective pressures over the emergence of others. Targeting anti-apoptotic dependencies in persisters increased sensitivity to chemotherapy or CAR T therapy. These results suggest that common biological mechanisms underly survival of persisters, whether derived from immune or drug therapy, and offer an explanation for the acquired cross-resistance to these two types of therapies often observed in the clinic. HighlightsO_LIImmunotherapy persister cells (IPCs) are less sensitive to drugs and radiation. C_LIO_LIDrug tolerant persisters (DTPs) are less sensitive to radiation and CAR T cell attack. C_LIO_LIIPCs and DTPs are less sensitive to mitochondrial apoptosis. C_LIO_LITargeting anti-apoptotic dependencies helps eliminate IPCs/DTPs. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/641492v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@fe98b4org.highwire.dtl.DTLVardef@db7bfdorg.highwire.dtl.DTLVardef@1a94469org.highwire.dtl.DTLVardef@1ca6b2c_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

In vivo CRISPR screens identify key modifiers of CAR T cell function in myeloma

Chimeric antigen receptor (CAR) T cells are highly effective in hematologic malignancies. However, loss of CAR T cells can contribute to relapse in a significant number of patients. These limitations could potentially be overcome by targeted gene editing to increase CAR T cell persistence. Here, we performed in vivo loss-of-function CRISPR screens in BCMA-targeting CAR T cells to investigate genes that influence CAR T cell persistence, function and efficacy in a human multiple myeloma model. We tracked the expansion and persistence of CRISPR-library edited T cells in vitro and then at early and late timepoints in vivo to track the performance of gene modified CAR T cells from manufacturing to survival in tumors. The screens revealed several context-specific regulators of CAR T cell expansion and persistence. Ablation of RASA2 and SOCS1 enhanced T cell expansion in vitro, while loss of PTPN2, ZC3H12A, and RC3H1 conferred early selective growth advantages to CAR T cells in vivo. Strikingly, we identified cyclin-dependent kinase inhibitor 1B (CDKN1B), a cell cycle regulator, as the most important factor limiting CAR T cell fitness at late timepoints in vivo. CDKN1B ablation increased BCMA CAR T cell proliferation and effector function in response to antigen, significantly enhancing tumor clearance and overall survival. Thus, our findings reveal differing effects of gene-perturbation on CAR T cells over time and in different selective environments, highlight CDKN1B as a promising target to generate highly effective CAR T cells for multiple myeloma, and underscore the importance of in vivo screening as a tool for identifying genes to enhance CAR T cell function and efficacy.

immunology↗