title: Androgen suppresses the proliferation of androgen receptor-positive castration-resistant prostate cancer cells via inhibition of Cdk2, CyclinA, and Skp2.
abstract: The majority of prostate cancer (PCa) patient receiving androgen ablation therapy eventually develop castration-resistant prostate cancer (CRPC). We previously reported that androgen treatment suppresses Skp2 and c-Myc through androgen receptor (AR) and induced G1 cell cycle arrest in androgen-independent LNCaP 104-R2 cells, a late stage CRPC cell line model. However, the mechanism of androgenic regulation of Skp2 in CRPC cells was not fully understood. In this study, we investigated the androgenic regulation of Skp2 in two AR-positive CRPC cell line models, the LNCaP 104-R1 and PC-3AR Cells. The former one is an early stage androgen-independent LNCaP cells, while the later one is PC-3 cells re-expressing either wild type AR or mutant LNCaP AR. Proliferation of LNCaP 104-R1 and PC-3AR cells is not dependent on but is suppressed by androgen. We observed in this study that androgen treatment reduced protein expression of Cdk2, Cdk7, Cyclin A, cyclin H, Skp2, c-Myc, and E2F-1; lessened phosphorylation of Thr14, Tyr15, and Thr160 on Cdk2; decreased activity of Cdk2; induced protein level of p27(Kip1); and caused G1 cell cycle arrest in LNCaP 104-R1 cells and PC-3AR cells. Overexpression of Skp2 protein in LNCaP 104-R1 or PC-3AR cells partially blocked accumulation of p27(Kip1) and increased Cdk2 activity under androgen treatment, which partially blocked the androgenic suppressive effects on proliferation and cell cycle. Analyzing on-line gene array data of 214 normal and PCa samples indicated that gene expression of Skp2, Cdk2, and cyclin A positively correlates to each other, while Cdk7 negatively correlates to these genes. These observations suggested that androgen suppresses the proliferation of CRPC cells partially through inhibition of Cyclin A, Cdk2, and Skp2.
authors.affiliation: The Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America.
authors.forename: John M
authors.initials: JM
authors.lastname: Kokontis
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan.
authors.forename: Hui-Ping
authors.initials: HP
authors.lastname: Lin
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan.
authors.forename: Shih Sheng
authors.initials: SS
authors.lastname: Jiang
authors.affiliation: Institute of Cellular and System Medicine, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Lin
authors.affiliation: The Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America; Pharmaceuticals and Medical Devises Agency, Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Fukuchi
authors.affiliation: The Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Hiipakka
authors.affiliation: Department of Health Risk Management, China Medical University, Taichung City, Taiwan.
authors.forename: Chi-Jung
authors.initials: CJ
authors.lastname: Chung
authors.affiliation: Department of Medical Education and Research, China Medical University Beigang Hospital, Yunlin, Taiwan; Department of Medical Education and Research, Tainan Municipal An-Nan Hospital-China Medical University, Tainan, Taiwan.
authors.forename: Tzu-Min
authors.initials: TM
authors.lastname: Chan
authors.affiliation: The Ben May Department for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America.
authors.forename: Shutsung
authors.initials: S
authors.lastname: Liao
authors.affiliation: Pharmaceuticals and Medical Devises Agency, Tokyo, Japan.
authors.forename: Chung-Ho
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Pharmaceuticals and Medical Devises Agency, Tokyo, Japan; Graduate Institute of Basic Medical Science, China Medical University, Taichung City, Taiwan; Biotechnology Center, National Chung Hsing University, Taichung, Taiwan, Taichung City, Taiwan; Ph.D. program in Environmental and Occupational Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan.
authors.forename: Chih-Pin
authors.initials: CP
authors.lastname: Chuu
mesh_terms: D000728:Androgens / Q000502:physiology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000502:physiology*; D019925:Cyclin A / Q000037:antagonists & inhibitors*; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors*; D006801:Humans; D008297:Male; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000473:pathology*; D044786:S-Phase Kinase-Associated Proteins / Q000037:antagonists & inhibitors*
chemical_list: D000728:Androgens; D019925:Cyclin A; D044786:S-Phase Kinase-Associated Proteins; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2