Our experiments using CXCR1- and CXCR2-deficient mice support that pleural tumor cell-secreted CXCL1/PPBP is cardinal for MPE and are in line with a previous study demonstrating increased production of CXCL1 by tumor cells during human MPE development that mobilizes regulatory T cells59. Here, CXCL1 is linked to pleural neoplasm.