PIK3R1 and cancer: In summary, our comprehensive pan-cancer analysis of PIK3R1 and PIK3R2 demonstrated that PIK3R1 was frequently underexpressed while PIK3R2 was frequently overexpressed in most tumors, and they were both closely associated with clinical prognosis, DNA methylation and immune infiltration level for multiple human tumors, which greatly contribute to understanding the roles of PIK3R1 and PIK3R2 in tumorigenesis.