PPP2R1B gene alterations inhibit interaction of PP2A-Aβ and PP2A-C proteins in colorectal cancers
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- Published online on: March 1, 2004 https://doi.org/10.3892/or.11.3.655
- Pages: 655-659
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Abstract
The chromosome region 11q is frequently deleted in colorectal cancers. The PPP2R1B tumor suppressor gene, encoding the β isoform of the A subunit of serine/threonine-specific protein phosphatase 2A (PP2A-Aβ), located at 11q22-23, is inactivated in patients with cancer. The present study investigated whether or not PP2A-Aβ is altered in colorectal cancers. We searched for alterations of the PPP2R1B gene and interactions between PP2A-Aβ and PP2A-C proteins in 50 surgically resected colorectal cancer tissues. Missense mutations and homozygous deletions of the PPP2R1B gene were found in 4 of 50 patients (8%) and in 1 of 50 patients, respectively, with colorectal cancers. Deletions and/or point mutations within 412-601 amino acid sequences (binding regions of PP2A-C protein) of the PPP2R1B gene derived from colorectal cancer tissues inhibited co-immunoprecipitation of PP2A-Aβ and PP2A-C proteins. These finding suggested that the PPP2R1B gene functions as a tumor suppressor gene and acts as a molecular switch that becomes active in response to specific up-stream signals. Upon activation, the gene alters the activities of specific downstream target proteins for the cell cycle regulations and/or metabolism in some colorectal cancers.