The main challenges in the use of immune checkpoint inhibitors(ICIs)are ascribed to the immunosuppressive tumor microenvironment and the lack of sufficient infiltration of activated CD8+T cells.Transforming the tumor microenvironment(TME)from“cold”to“hot”and thus more likely to potentiate the effects of ICIs is a promising strategy for cancer treatment.We found that the selective BCL-2 inhibitor APG-2575 can enhance the antitumor efficacy of anti-PD-1 therapy in syngeneic and humanized CD34+mouse models.Using single-cell RNA sequencing,we found that APG-2575 polarized M2-like immunosuppressive macrophages toward the M1-like immunostimulatory phenotype with increased CCL5 and CXCL10 secretion,restoring T-cell function and promoting a favorable immunotherapy response.Mechanistically,we demonstrated that APG-2575 directly binds to NF-κB p65 to activate NLRP3 signaling,thereby mediating macrophage repolarization and the activation of proinflammatory caspases and subsequently increasing CCL5 and CXCL10 chemokine production.As a result,APG-2575-induced macrophage repolarization could remodel the tumor immune microenvironment,thus improving tumor immunosuppression and further enhancing antitumor T-cell immunity.Multiplex immunohistochemistry confirmed that patients with better immunotherapeutic efficacy had higher CD86,p-NF-κB p65 and NLRP3 levels,accompanied by lower CD206 expression on macrophages.Collectively,these data provide evidence that further study on APG-2575 in combination with immunotherapy for tumor treatment is required.