title: Hemizygous disruption of Cdc25A inhibits cellular transformation and mammary tumorigenesis in mice.
abstract: CDC25A phosphatase activates multiple cyclin-dependent kinases (CDK) during cell cycle progression. Inactivation of CDC25A by ubiquitin-mediated degradation is a major mechanism of DNA damage-induced S-G(2) checkpoint. Although increased CDC25A expression has been reported in various human cancer tissues, it remains unclear whether CDC25A activation is a critical rate-limiting step of carcinogenesis. To assess the role for CDC25A in cell cycle control and carcinogenesis, we used a Cdc25A-null mouse strain we recently generated. Whereas Cdc25A(-/-) mice exhibit early embryonic lethality, Cdc25A(+/-) mice show no appreciable developmental defect. Cdc25A(+/-) mouse embryonic fibroblasts (MEF) exhibit normal kinetics of cell cycle progression at early passages, modestly enhanced G(2) checkpoint response to DNA damage, and shortened proliferative life span, compared with wild-type MEFs. Importantly, Cdc25A(+/-) MEFs are significantly resistant to malignant transformation induced by coexpression of H-ras(V12) and a dominant negative p53 mutant. The rate-limiting role for CDC25A in transformation is further supported by decreased transformation efficiency in MCF-10A human mammary epithelial cells stably expressing CDC25A small interfering RNA. Consistently, Cdc25A(+/-) mice show substantially prolonged latency in mammary tumorigenesis induced by MMTV-H-ras or MMTV-neu transgene, whereas MMTV-myc-induced tumorigenesis is not significantly affected by Cdc25A heterozygosity. Mammary tissues of Cdc25A(+/-);MMTV-neu mice before tumor development display less proliferative response to the oncogene with increased tyrosine phosphorylation of CDK1/2, but show no significant change in apoptosis. These results suggest that Cdc25A plays a rate-limiting role in transformation and tumor initiation mediated by ras activation.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry, and Robert H. Lurie Comprehensive Cancer Center, Northwestern University, 303 E. Superior Street, Chicago, IL 60611, USA.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Ray
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Terao
authors.forename: Dipali
authors.initials: D
authors.lastname: Nimbalkar
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hirai
authors.forename: Evan C
authors.initials: EC
authors.lastname: Osmundson
authors.forename: Xianghong
authors.initials: X
authors.lastname: Zou
authors.forename: Roberta
authors.initials: R
authors.lastname: Franks
authors.forename: Konstantin
authors.initials: K
authors.lastname: Christov
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kiyokawa
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D016195:G2 Phase; D015972:Gene Expression Regulation, Neoplastic; D015674:Mammary Neoplasms, Animal / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016196:S Phase; D013997:Time Factors; D020687:cdc25 Phosphatases / Q000235:genetics* / Q000502:physiology*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: C517004:CDC25A protein, human; C517005:Cdc25a protein, mouse; D020687:cdc25 Phosphatases; D018631:ras Proteins