[Characteristics of the tumor microenvironment and therapeutic progress in malignant pleural effusion]

Malignant pleural effusion (MPE) can be secondary to various advanced malignant tumors. Although systemic anti tumor therapy may be effective in primary tumors, it cannot reduce the accumulation of MPE in proportion of the patients. The interaction of tumor cells, immune cells, and mesenchymal cells, as well as the abnormal proliferation of tumor-associated blood vessels, together create an immunosuppressive microenvironment for MPE, which promotes the abnormal proliferation of tumor cells and the accumulation of MPE. With the in-depth study of the tumor microenvironment, the application of local systemic anti-tumor therapy with local intrathoracic application of immune checkpoint inhibitors, immune cells, cytokines, and gene-mediated cytotoxic immunotherapy are able to alleviate the immunosuppressive tumor microenvironment and inhibit the accumulation of MPE. This article aimed to describe the tumor microenvironment in MPE and provide clues for identifying novel therapeutic targets.