CXCR4 and head and neck cancer: Furthermore, CXCL12-CXCR4 signaling is involved in stromal-immune crosstalk [164] giving a rationale for the clinical investigation of CXCR4 inhibitors in combination with anti-PD1 in metastatic pancreatic (NCT04177810, NCT02826486) and head and neck cancers (NCT04058145).