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PP2A Inactivation Mediated by PPP2R4 Haploinsufficiency Promotes Cancer Development
Tekijät: Ward Sents, Bob Meeusen, Petar Kalev, Enrico Radaelli, Xavier Sagaert, Eline Miermans, Dorien Haesen, Caroline Lambrecht, Mieke Dewerchin, Peter Carmeliet, Jukka Westermarck, Anna Sablina, Veerle Janssens
Kustantaja: AMER ASSOC CANCER RESEARCH
Julkaisuvuosi: 2017
Journal: Cancer Research
Tietokannassa oleva lehden nimi: CANCER RESEARCH
Lehden akronyymi: CANCER RES
Vuosikerta: 77
Numero: 24
Aloitussivu: 6825
Lopetussivu: 6837
Sivujen määrä: 13
ISSN: 0008-5472
DOI: https://doi.org/10.1158/0008-5472.CAN-16-2911
Tiivistelmä
Protein phosphatase 2A (PP2A) complexes counteract many oncogenic kinase pathways. In cancer cells, PP2A function can be compromised by several mechanisms, including sporadic mutations in its scaffolding A and regulatory B subunits or more frequently through overexpression of cellular PP2A inhibitors. Here, we identify a novel genetic mechanism by which PP2A function is recurrently affected in human cancer, involving haploinsufficiency of PPP2R4, a gene encoding the cellular PP2A activator PTPA. Notably, up to 70% of cancer patients showed a heterozygous deletion or missense mutations in PPP2R4 Cancer-associated PTPA mutants exhibited decreased abilities to bind the PP2A-C subunit or activate PP2A and failed to reverse the tumorigenic phenotype induced by PTPA suppression, indicating they function as null alleles. In Ppp2r4 gene-trapped (gt) mice showing residual PTPA expression, total PP2A activity and methylation were reduced, selectively affecting specific PP2A holoenzymes. Both PTPA(gt/gt) and PTPA(+/gt) mice showed higher rates of spontaneous tumors, mainly hematologic malignancies and hepatocellular adenomas and carcinomas. These tumors exhibited increased c-Myc phosphorylation and increased Wnt or Hedgehog signaling. We observed a significant reduction in lifespan in PTPA(+/g)t mice compared with wild-type mice. In addition, chemical-induced skin carcinogenesis was accelerated in PTPA(+/gt) compared with wild-type mice. Our results provide evidence for PPP2R4 as a haploinsufficient tumor suppressor gene, defining a high-penetrance genetic mechanism for PP2A inhibition in human cancer. (C) 2017 AACR.
Protein phosphatase 2A (PP2A) complexes counteract many oncogenic kinase pathways. In cancer cells, PP2A function can be compromised by several mechanisms, including sporadic mutations in its scaffolding A and regulatory B subunits or more frequently through overexpression of cellular PP2A inhibitors. Here, we identify a novel genetic mechanism by which PP2A function is recurrently affected in human cancer, involving haploinsufficiency of PPP2R4, a gene encoding the cellular PP2A activator PTPA. Notably, up to 70% of cancer patients showed a heterozygous deletion or missense mutations in PPP2R4 Cancer-associated PTPA mutants exhibited decreased abilities to bind the PP2A-C subunit or activate PP2A and failed to reverse the tumorigenic phenotype induced by PTPA suppression, indicating they function as null alleles. In Ppp2r4 gene-trapped (gt) mice showing residual PTPA expression, total PP2A activity and methylation were reduced, selectively affecting specific PP2A holoenzymes. Both PTPA(gt/gt) and PTPA(+/gt) mice showed higher rates of spontaneous tumors, mainly hematologic malignancies and hepatocellular adenomas and carcinomas. These tumors exhibited increased c-Myc phosphorylation and increased Wnt or Hedgehog signaling. We observed a significant reduction in lifespan in PTPA(+/g)t mice compared with wild-type mice. In addition, chemical-induced skin carcinogenesis was accelerated in PTPA(+/gt) compared with wild-type mice. Our results provide evidence for PPP2R4 as a haploinsufficient tumor suppressor gene, defining a high-penetrance genetic mechanism for PP2A inhibition in human cancer. (C) 2017 AACR.
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