Loss of TP53 mediates suppression of Macrophage Effector Function via Extracellular Vesicles and PDL1 towards Resistance against Chemoimmunotherapy in B-cell malignancies

Abstract

Highlights• Loss of TP53 in B-cell lymphoma induces resistance towards chemoimmunotherapy (CIT) by inhibition of macrophage effector function through PDL1 upregulation • Loss of TP53 increases formation of extracellular vesicles (EVs) carrying PDL1 • EVs inhibit antibody-mediated cellular phagocytosis (ADCP), a key macrophage effector function in CIT • Targeting PDL1 on EVs with immune checkpoint inhibitors overcomes TP53-mediated resistance to CIT Summary Chemoimmunotherapy (CIT) is the standard of care in B-cell malignancies. It is relying on synergistic effects of alkylating chemotherapy and monoclonal antibodies via secretory crosstalk with effector macrophages. Here, we observed that loss of p53 function mediates resistance to CIT by suppressing macrophage phagocytic function. Loss of p53 leads to an upregulation of PDL1 and an increased formation of extracellular vesicles (EVs). EVs directly inhibit macrophage phagocytosis by PDL1 surface expression. Suppression of phagocytic function by lymphoma cell-derived EVs could be abrogated by pre-incubation of EVs with anti-PDL1 antibodies, CRISPR-KO of PDL1 and abrogation of EV formation by RAB27A-KO in lymphoma cells. Immune checkpoint inhibition represents a viable 3 strategy to overcome EV-mediated resistance to chemoimmunotherapy in lymphoma. SignificanceLoss of TP53 mediates cell autonomous resistance to genotoxic chemotherapy, moreover non-cell autonomous effects may cause therapy resistance mediated by the tumor microenvironment. We identify a TP53dependent mechanism that mediates resistance to synergistic chemoimmunotherapy by increasing formation of EVs and expression of the PDL1 immune checkpoint. PDL1 on EVs is directly responsible for macrophage suppression, preventing the exertion of the essential effector function of antibody-dependent cellular phagocytosis. This novel mechanism of resistance is in turn targetable by PDL1 checkpoint inhibition. Enhanced EV-release and immune checkpoint expression in lymphoma are novel mechanisms of macrophage modulation in the lymphoma microenvironment.We provide a novel principle of resistance to chemoimmunotherapy (CIT) representing of immediate relevance to treatment of refractory B-cell lymphoma.

Extracellular Vesicles: Messengers of p53 in Tumor–Stroma Communication and Cancer Metastasis

“…Intriguingly, the recruitment of neutrophils or tumor-promoting macrophages at distant organ sites is considered to be a defining moment for the EV-dependent promotion of metastasis [ 78 , 98 ]. Mechanistically, the BAG6-dependent release of anti-tumor EVs was found to require direct BAG6 association with the CBP/p300 acetylase, and subsequent translocation into the cytoplasm to acetylate p53 [ 82 , 84 ]. Of note, the nuclear import of BAG6 and CBP/p300 in response to starvation triggers the acetylation of nuclear p53 and autophagy [ 104 ].…”

“…Cancer progression and metastasis is associated with the development of therapy resistance, which is often dictated by complex interactions between malignant cells and the immune compartment. In a recent study on the chemoimmunotherapy of B cell malignancies, wild-type p53 was found to play a crucial role in the successful phagocytic elimination of cancer cells by macrophages [ 84 ]. As shown in primary patient samples with wild-type p53 status, the combination treatment with chemotherapy and anti-CD20 antibodies results in highly antibody-dependent cellular phagocytosis, [ 84 ].…”

“…In a recent study on the chemoimmunotherapy of B cell malignancies, wild-type p53 was found to play a crucial role in the successful phagocytic elimination of cancer cells by macrophages [ 84 ]. As shown in primary patient samples with wild-type p53 status, the combination treatment with chemotherapy and anti-CD20 antibodies results in highly antibody-dependent cellular phagocytosis, [ 84 ]. This effect is lost as a result of p53 mutations, indicating that wild-type p53 modulates the communication between cancer cells and the tumor microenvironment by driving the phagocytic capacity of tumor-fighting macrophages [ 84 ].…”

“…As shown in primary patient samples with wild-type p53 status, the combination treatment with chemotherapy and anti-CD20 antibodies results in highly antibody-dependent cellular phagocytosis, [ 84 ]. This effect is lost as a result of p53 mutations, indicating that wild-type p53 modulates the communication between cancer cells and the tumor microenvironment by driving the phagocytic capacity of tumor-fighting macrophages [ 84 ]. In this scenario, p53 operates as a functional switch that suppresses the release of EVs, which transfer immune checkpoint molecules, in particular programmed-death ligand 1 (PD-L1) [ 84 ].…”

“…This effect is lost as a result of p53 mutations, indicating that wild-type p53 modulates the communication between cancer cells and the tumor microenvironment by driving the phagocytic capacity of tumor-fighting macrophages [ 84 ]. In this scenario, p53 operates as a functional switch that suppresses the release of EVs, which transfer immune checkpoint molecules, in particular programmed-death ligand 1 (PD-L1) [ 84 ]. Inactivation of p53 not only results in the secretion of increased numbers of EVs, but also in EV cargo alterations, and particularly, the elevated expression of vesicular PD-L1, which drives resistance to therapeutic targeting and can be overcome with an anti-PD-L1 immune checkpoint inhibitor [ 84 ].…”