Studies have shown that the IL-17 signaling pathway can increase the immunosuppressive activity of regulatory T cells, leading to tumor growth and development (28).High concentrations of baseline serum IL-17 were identified in ipilimumab-treated metastatic melanoma patients developing severe grade 3 gastrointestinal irAEs and may thus serve as a putative biomarker for defining both at-risk patients and the severity of ipilimumab-induced colitis (29). This evidence concerns the gene IL17A and metastatic melanoma.