CXCL8 and neoplasm: Additional studies also showed that inhibition of programmed cell death protein 1 (PD1) by pembrolizumab enhanced regulation of cytotoxic T-cell tumoricidal activities, which ultimately leads to increased expression levels of tumor-enhanced CXCL8, which subsequently induces infiltration of tumor-associated macrophages (M2) in the immune system [74,75].