title: LMW-E/CDK2 deregulates acinar morphogenesis, induces tumorigenesis, and associates with the activated b-Raf-ERK1/2-mTOR pathway in breast cancer patients.
abstract: Elastase-mediated cleavage of cyclin E generates low molecular weight cyclin E (LMW-E) isoforms exhibiting enhanced CDK2-associated kinase activity and resistance to inhibition by CDK inhibitors p21 and p27. Approximately 27% of breast cancers express high LMW-E protein levels, which significantly correlates with poor survival. The objective of this study was to identify the signaling pathway(s) deregulated by LMW-E expression in breast cancer patients and to identify pharmaceutical agents to effectively target this pathway. Ectopic LMW-E expression in nontumorigenic human mammary epithelial cells (hMECs) was sufficient to generate xenografts with greater tumorigenic potential than full-length cyclin E, and the tumorigenicity was augmented by in vivo passaging. However, cyclin E mutants unable to interact with CDK2 protected hMECs from tumor development. When hMECs were cultured on Matrigel, LMW-E mediated aberrant acinar morphogenesis, including enlargement of acinar structures and formation of multi-acinar complexes, as denoted by reduced BIM and elevated Ki67 expression. Similarly, inducible expression of LMW-E in transgenic mice generated hyper-proliferative terminal end buds resulting in enhanced mammary tumor development. Reverse-phase protein array assay of 276 breast tumor patient samples and cells cultured on monolayer and in three-dimensional Matrigel demonstrated that, in terms of protein expression profile, hMECs cultured in Matrigel more closely resembled patient tissues than did cells cultured on monolayer. Additionally, the b-Raf-ERK1/2-mTOR pathway was activated in LMW-E-expressing patient samples, and activation of this pathway was associated with poor disease-specific survival. Combination treatment using roscovitine (CDK inhibitor) plus either rapamycin (mTOR inhibitor) or sorafenib (a pan kinase inhibitor targeting b-Raf) effectively prevented aberrant acinar formation in LMW-E-expressing cells by inducing G1/S cell cycle arrest. LMW-E requires CDK2-associated kinase activity to induce mammary tumor formation by disrupting acinar development. The b-Raf-ERK1/2-mTOR signaling pathway is aberrantly activated in breast cancer and can be suppressed by combination treatment with roscovitine plus either rapamycin or sorafenib.
authors.affiliation: Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America.
authors.forename: MyLinh T
authors.initials: MT
authors.lastname: Duong
authors.forename: Said
authors.initials: S
authors.lastname: Akli
authors.forename: Caimiao
authors.initials: C
authors.lastname: Wei
authors.forename: Hannah F
authors.initials: HF
authors.lastname: Wingate
authors.forename: Wenbin
authors.initials: W
authors.lastname: Liu
authors.forename: Yiling
authors.initials: Y
authors.lastname: Lu
authors.forename: Min
authors.initials: M
authors.lastname: Yi
authors.forename: Gordon B
authors.initials: GB
authors.lastname: Mills
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Hunt
authors.forename: Khandan
authors.initials: K
authors.lastname: Keyomarsi
mesh_terms: D061354:Acinar Cells / Q000166:cytology / Q000378:metabolism; D000818:Animals; D001557:Benzenesulfonates / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000378:metabolism; D019927:Cyclin E / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053208:Kaplan-Meier Estimate; D020935:MAP Kinase Signaling System / Q000235:genetics; D008321:Mammary Glands, Animal / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness / Q000235:genetics; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D011379:Prognosis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012189:Retrospective Studies; D000077546:Roscovitine; D020123:Sirolimus / Q000494:pharmacology; D000077157:Sorafenib; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D001557:Benzenesulfonates; D019927:Cyclin E; D010671:Phenylurea Compounds; D020033:Protein Isoforms; D011687:Purines; D011725:Pyridines; D000077546:Roscovitine; D009536:Niacinamide; D000077157:Sorafenib; C546842:MTOR protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D058570:TOR Serine-Threonine Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D020123:Sirolimus