| Bladder cancer is one of the common cancers worldwide, and more than 90% of bladder cancers are transitional cell carcinomas. In China, the incidence and mortality of bladder cancer have been the first in the urinary cancers. Bladder cancer is a disease with a complex, multifactor etiology, including interactions between genetic makeup and environmental factors. Epidemiologic studies have shown that the development of bladder cancer is associated with tobacco smoking and occupational exposure. Although many people have been exposed to the same risk factors, only a fraction of exposed individuals develop bladder cancer in their lifetime, suggesting that there is inter-individual variation in genetic susceptibility to bladder cancer.It is now known that genetic variants play an important role in gene structure and function, which could change the biological functions of genes. Single nucleotide polymorphism (SNP) is the most common types of genetic variations. About one thousand nucleotides each have a single base change. In the study of molecular epidemiology and genetics, SNPs have been widely used for gene mapping of molecular markers, by comparing the normal and patients of SNPs to locate and identify specific disease-related genes.Cell cycle is mainly regulated through Cyclins and cyclin-dependent protein kinase inhibiting protein. Inbalance of cell cycle plays a key role in tumor incidence and development. Cancer molecular biology studies have shown that almost all of the oncogene and tumor suppressor gene functional effects are involved in cell cycle mechanisms. CCND1 is a cell cycle-related oncogene. The CCND1 gene is highly polymorphic, however, the most extensively studied SNP is the G870A (rs603965) polymorphism in the exon 4. CCND1 is a key cell cycle regulatory protein, playing a critical role in the G1-to-S transition phase of the cell cycle peogression and is related closely with the tumor incidence, metastasis and prognosis.We investigated the association between CCND1 polymorphism and Chinese Han bladder cancer risk to further reveal the biological mechanism of bladder cancer incidence and development, and look for the biomarkers for genetic susceptibility to bladder cancer for individualized treatment and prevention.Part?CCND1 G870A polymorphism and baldder cancer risk in a case-control studyInbalance of cell cycle plays a key role in tumor incidence and developmen. The CCND1 G870A variant occurs in exon4 and when substitution of G to A will generate three genotypes wild AA, variant GG and Heterozygous AG, respectively. It is known that CCND1 polymorphism is associated with cancer susceptibility. However, no study to date reported the association between CCND1 G870A and Chinese baldder cancer susceptibility.We conducted a case-control study to investigate the association between CCND1 G870A and Chinese bladder cancer risk, including 408 newly diagnosed and histologically confirmed transitional cell carcinoma of bladder and 402 cancer-free control subjects. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The cancer-free control subjects were genetically unrelated to the cases, had no individual history of cancer and were recruited from those who accompanied the patients to the hospital and who were seeking health care. Controls were frequency-matched to the cases by age (±5 years) and sex.Our results showed that the AA genotypes had a significantly increased risk of bladder cancer, comparing with GG genotypes (OR= 1.71,95% CI= 1.14-2.57). Similarly, a significantly increased risk of bladder cancer was found in the combined variant GA/AA genotypes compared with the GG genotype (OR= 1.54,95% CI= 1.08-2.20). Further stratification analysis showed that this increased risk was more pronounced among subgroups of age?65 (OR= 1.74,95% CI= 1.06-2.88), men (OR = 1.67,95% CI= 1.15-2.44) and ever smokers (OR= 1.82,95% CI= 1.12-2.93). In the present study, we observed that A allele is a risk factor in the baldder cancer with gradel but no with grade2 or grade3.In conclusion, CCND1 G870A variation is association with baldder cancer susceptibility and AA genotype may predict bladder cancer.Part?A meta-analysis of CCND1 G870A polymorphism and bladdder cancer riskMeta analysis is a statistical method for system evaluation, it is through scientific and systematic approach to comprehensive assessment of the independent research analysis with the same purpose. In the association study of the polymorphism and disease, it often exists discrepance in larger and smaller samples. Meta analysis is widely used in researching the association between genetic disease and gene sites, through combining the useful association analysis data, to elevate the stastical power and solve many single gene problem.In the present study, we searched the electronic literature from PubMed and Medline for all relevant reports (the last search update was Mar 1,2009), using key words'Cyclin D1','G870A','polymorphism'and'bladder cancer'. The search was limited to English language papers. In our meta-analysis, the studies had to meet the following criteria:(i) was a study of CCND1 G870A polymorphism and bladder cancer risk, (ii) a case-control design and (iii) contained available genotype frequency.The results suggested that the variant 870GA/AA genotypes were associated with an increased risk of bladder cancer in Asian, but not in Caucasion. which was consistent with the results of our study. The CCND1 G870A polymorphism may be a marker for the development of bladder cancer in Chinese populations. Larger studides are required to validate these findings in diverse populations. Part?CCND1 G870A polymorphism predicts recurrence of bladder cancerThe grade and stage of bladder cancer are closely related with tumor prognosis. Currently, pathological grade and clinic stage provide important information to evaluate the tumor prognosis, however, it is difficult to exactly predict the biological behavior of bladder cancer and prognosis. With the development of molecular biological study and immunologicl study, many tumor marker have been used in predicting baldder cancer prognosis. No markers to date have been applied in clinic routinly. In our study, we investigated the association between CCND1 G870A polymorphism and superficial bladder cancer prognosis.In the present study, we followed up 230 bladder cancer patients, which were histologically proven transitional cell carcinoma, patients were followed up for additional clinical information (that is, recurrences and their pathological grades and clinical stages) every 3 months by telephone calls and histological confirmation after the first visit to the hospitals (the last follow-up data was Dec,2010). Genotyping was conducted by using Taqman method. The associations between polymorphic genotypes and tumor recurrence were estimated using the Kaplan-Meier method and assessed by the log-rank test. HR for risk of recurrence was estimated from a multivariate cox proportion hazards model, with adjustment for age, sex, pack-years smoked and tumor grade.We observed that comparing A allele may increase the risk of baldder cancer recurrence. A significantly increased recurrence risk was observed among men (GA versus GG HR=2.10,95% CI= 1.02-4.32, P= 0.044),?65 (GA versus GG, HR= 2.46,95% CI= 1.06-5.75, P= 0.037) and grade?(GA versus GG, HR= 6.87, 95% CI= 1.67-28.30, P= 0.008).Our results suggested that CCND1 G870A polymorphism may contribute to bladder cancer prognosis. CCND1 G870A polymorphism could affect the recurrence of bladder cancer, which may add to the valuable molecular markers for detecting bladder cancer recurrence. We can carry out individual treatment on patients who carry CCNDI risky genotypes, so that we will detect disease early and improve the prognosis of bladder cancer patients.Part IV Effects of the CCNDI G870A polymorphism on CCNDI mRNA and protein expressionCCND1 is a key protein in regulating G1 stage cell proliferation signal. Many studies researched this protein and it is related closely with the development of tumor. It is known that CCNDI express highly in tumor tissues and is related with the tumor proliferation and invasive activity. In order to validate our results, we investigated the mRNA and protein level of CCNDI gene in bladder tissues.In the present study, we then evaluated the effect of the CCNDI G870A polymorphism on CCNDI mRNA expression in 16 bladder normal tissues detected by the real-time quantitative RT-PCR. In addition, we analyzed the CCNDI protein expression in 48 bladder tumor tissues by immunohistochenistry. We genotyped CCND1 G870A in bladder tissues by Taqman.The CCNDI mRNA expression levels were significantly higher in individuals with the AA genotype than in those with the AG/GG genotypes (0.017±0.004 versus 0.007±0.002, P= 0.254). We found that the expression level of protein was obviously higher for the AA genotype (71.4%) than for the GA/GG genotypes (35.3%) in the nucleus (P= 0.024).We investigated the mRNA and protein level of the CCND1 gene. Results suggested that AA genotyped may predict the risk and prognosis of bladder cancer. CCND1 G870A may be a biological marker for bladder cancer susceptibility. Our study revealed possiblely etiology and mechanism of bladder cancer. It is better to provide important theoretical and practical significance for further individualized cancer prevention, intervention and treatment. |
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