GPR68 and melanoma: For example, the collection of melanoma tissue from wild-type mice and GPR68-knockout mice and analysis of tissue infiltration by immune cells, such as lymphocytes, monocytes, neutrophils, and natural killer (NK) cells, revealed a low accumulation of CD8+ T cells and NK cells in wild-type mouse melanoma tissues, while a high accumulation of CD8+ T cells and NK cells was observed in GPR68-knockout mouse melanoma tissues.