Topical administration of 5-aminolevulinic acid in association with photodynamic therapy (PDT) in a murine cSCC model and patients allows the increase of CCL8/MCP-2 expression, the recruitment of macrophages with an M1 phenotype, and the regression of tumor growth in mice, especially when co-administered with exogenous CCL8/MCP-2 [85]. The gene discussed is CCL8; the disease is skin squamous cell carcinoma.