PIK3CA and neoplasm: Among other genetic alterations involving AKT pathway genes, in acral melanoma, the oncogenic p85β regulatory subunit 2 of PI3K (PIK3R2) is amplified along with PDPK1 (PDK-1), while the tumor suppressor genes PIK3R1 (encoding p85α) and PTEN are lost or mutated [181, 182].