Cyclin D1, with a common G/A polymorphism in rs9344, is an essential regulator of the G1 phase in cell cycles and plays an important role in several tumor types, and the homology of cyclin D1 with human papillomavirus (HPV)-16 E7 brought our attention to CCND1 gene in cervical cancer. A total of 738 native Chinese subjects consist of 327 cases and 411 controls were enrolled in this study. CCND1 genotyping was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and partially verified by sequencing of genomic DNA and cDNA. The transcription of cyclin D1 mRNA isoforms was analyzed by quantitative PCR; expression of protein isoforms by immunohistochemistry and Western blotting. We observed that the AA genotype had decreased risk of developing cervical cancer (odds ratio [OR] = 0.332; 95% confidence interval [CI] = 0.113-0.978; P = 0.045). The two mRNA isoforms were both transcripted from A and G allele. Transcript b decreased in squamous cell carcinoma of the uterine cervix (SCCUC) group (P = 0.004), especially poorly differentiated group (P = 0.004), and in G allele group of normal subjects (P = 0.001). In immunohistochemistry analysis, cyclins D1, D1a, and D1b failed to correlate with cervical cancer (P = 0.808, 0.445, and 0.095). However, cyclin D1b was downregulated in SCCUC group analyzed by Western blotting (P = 0.039). This study indicates that CCND1 rs9344 polymorphisms confer host susceptibility to cervical cancer. A allele possesses a relative protective effect probably through the cyclin D1b's inhibition on HPV carcinogenesis.
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