CXCR4 and squamous cell carcinoma: Using a mouse squamous cell carcinoma cell line (SCC VII), we showed a noteworthy positive association between the RNA expression levels of formyl peptide receptor 1 (FPR1), an established marker gene of neutrophils, and of C-X-C motif chemokine receptor 4 (CXCR4), whose gene product increases during neutrophil aging on the surface of these immune cells, with higher tumor stages (83, 84).