Alterations of the PPP1R3 gene in human cancer.

Recently, the PTEN/MMAC1 gene encoding a protein phosphatase (PP) and the PPP2R1B gene encoding a regulatory subunit of PP2A have been identified as being genetically altered in several types of human cancers, indicating that aberrations of intracellular signaling pathways via PPs are involved in human carcinogenesis. Here we report genetic alterations of the PPP1R3 gene located at chromosome 7q31, which encodes regulatory subunit 3 of PP1, in various types of human cancers. Mutations of the PPP1R3 gene were detected in 5 of 33 (15%) non-small cell lung cancer cell lines and 2 of 38 (5%) primary non-small cell lung cancers and were also observed in cell lines derived from a small cell lung cancer, an ovarian cancer, a colorectal cancer, and a gastric cancer. Mutations were widely dispersed in the coding region of the PPP1R3 gene. Three of the 11 detected mutations were nonsense mutations, whereas the remaining ones were missense mutations, most of which caused substitutions of evolutionarily conserved amino acids. These findings suggest that PPP1R3 alteration plays a role in the development of human cancers and that PPP1R3 could act as a tumor suppressor gene.