PRF1 and melanoma: Group 2 were genes implicated in T cell stimulation and recruitment, etc. Group 3 included cytokine and exhausted-related genes, such as GZMB, PRF1, HAVCR2, etc. Group 4 also contained several T cells-related chemokines and activated genes, including CCL4, CXCL9, SLAMF1, etc. The PPI network in cold tumor comprises a cluster of small proline-rich proteins (SPRR) family, while its role in melanoma is unclear (Figures 5H).