The glycine 90 to aspartate alteration in the Aβ subunit of PP2A (PPP2R1B) associates with breast cancer and causes a deficit in protein function

Mutations of the PPP2R1B gene, which encodes the A beta scaffolding subunit of serine/threonine protein phosphatase 2A (PP2A), have been identified in several types of cancer including lung and breast carcinoma. One of these mutations results in an alteration of glycine 90 to aspartic acid (G90D), which has been found in both tumor and genomic DNA, raising the possibility that it is associated with an increased risk for cancer. A novel microarray-based technology was used to screen for this single-nucleoticle polymorphism in 387 cancer patients and 329 control individuals. These data were used for case-control and family-based comparisons in order to study the association of this polymorphism with susceptibility to lung carcinoma, breast carcinoma, and acute lymphoblastic leukemia. The frequency of the G90D polymorphism in breast cancer patients was significantly higher in cases (3%) than in controls (0.3%). The wild-type A beta subunit interacted with the B56 gamma (PPKRK), PR72 (PPP2R3A), and PR48 subunits of PP2A but did not interact with the B55 alpha (PPP2R2A), B56 alpha (PPKMA), or B56 beta (PPP2R5B) regulatory subunits in an in vitro binding assay. The G90D alteration inhibited the interaction of A beta with the B56 gamma subunit but had no effect on binding to the PR72 subunit. These results provide evidence that the G90D alteration of the AP subunit of PP2A is associated with a low frequency of breast carcinoma and that the role of this alteration in transformation is likely to involve decreased interaction with the B56 gamma regulatory subunit. (c) 2005 Wiley-Liss, Inc.