Deregulation of the p16-cyclin D1/cyclin-dependent kinase 4-retinoblastoma pathway involved in the rat bladder carcinogenesis induced by terephthalic acid-calculi.
Prolonged cell proliferation in response to irritation by calculi may itself evoke malignant transformation of the urothelium. However, the molecular mechanisms underlying this process are still unknown. The aim of the present study was to investigate cell cycle regulatory mechanisms in bladder carcinogenesis induced by bladder calculi. Six-week-old Wistar rats were consecutively fed a diet containing 5% terephthalic acid (TPA), 5% TPA plus 4% sodium bicarbonate (NaHCO(3)), 4% NaHCO(3), or basal diet for 48 weeks. Animals were killed at weeks 12, 24, and 48. Treatment with 5% TPA caused high incidences of bladder calculi, preneoplastic lesions, and neoplastic lesions. Immunohistochemical examination revealed overexpression of cyclin D1, cyclin-dependent kinase 4 (Cdk4), retinoblastoma (Rb), and proliferating cell nuclear antigen (PCNA) in bladder preneoplastic and neoplastic lesions. In contrast, p16 expression was reduced or absent. These results were confirmed by immunoblotting analysis. Quantitation of mRNA by real-time reverse transcription-polymerase chain reaction (RT-PCR) showed a significant increase in cyclin D1 and PCNA mRNA in tumor cells. None of the 16 transitional cell carcinomas (TCCs) had ras mutations as examined by PCR-single strand conformational polymorphism (PCR-SSCP) analysis. These results suggested that deregulation of p16-cyclin D1/Cdk4-Rb pathway, but not oncogenic activation of ras, plays a crucial role in bladder tumorigenesis induced by bladder calculi.
Cui
Lunbiao
L
Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China.
Shi
Yuan
Y
Qian
Jie
J
Dai
Guidong
G
Wang
Yubang
Y
Xia
Yankai
Y
Chen
Jianfeng
J
Song
Ling
L
Wang
Shouling
S
Wang
Xinru
X
D000818:Animals; D002455:Cell Division; D056741:Cyclin D; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D016213:Cyclins / Q000235:genetics*; D016166:Free Radical Scavengers; D015972:Gene Expression Regulation, Neoplastic; D007150:Immunohistochemistry; D008297:Male; D010795:Phthalic Acids; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016160:Retinoblastoma Protein / Q000235:genetics*; D001749:Urinary Bladder Neoplasms / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D014545:Urinary Calculi / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D019459:Urothelium / Q000378:metabolism / Q000473:pathology
D056741:Cyclin D; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016213:Cyclins; D016166:Free Radical Scavengers; D010795:Phthalic Acids; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; C011363:terephthalic acid