PIK3R1 and neoplasm: Subsequently, correlations with PIK3R1 expression among 47 ICP genes were found in many tumor types, especially in ESCA, PAAD, PRAD, STAD, HNSC, THCA, DLBC and UVM, and PIK3R1 expression was positively associated with more than 25 ICP genes (Fig. 5C, P < 0.05).