The Polymorphism NER Gene XPA And The Expressions Of NER Gene XPF Play A Important Role In Human Bladder Cancer Carcinogenesis And Progression And Drug Resistance To Hydroxycamptothecin

Urinary bladder caner is the fourth most common neoplasm found in men from westerncountries, with urothelial cell carcinoma being the most common subtype(about90percent).The neoplasm is the main disease which threated the lives of the human being.So far,a surgerywith chemotherapy afteroperation is the main thied to deal with this disese. Of the bladdercancer patients, approximately50%will experience a recurrence within2years after aninitial diagnosis,and16-25%will have recurrence after endoscopic resection and need asecond surgery,this distroyed the patients' quality of life.Therefore,to make clear thepathogenesis and the mechanism of recurrence and drug resistant can decrease the incidenceand impove the quality of life of bladder cancer.Many studies have shown that the expressions of NER related genes are related to theirDNA repair capabilities. High expressions of NER related genes correlate with lowchemosensitivity of cancers. Fautrel et al. found that the expression of xerodermapigmentosum group C in the liver cancer tissue was significantly higher than in normal livertissue and high expression of XPC correlates with the decreased chemosensitivity of cancers.Reduced expression of xeroderma pigmentosum group A (XPA) in testis carcinoma wasassociated with high sensitivity to cisplatin. Chen et al. found a direct relationship betweenlow XPC expression and the development of human bladder cancer.The reseatch of XPA and NER is stimulated by the finding that a genetic defect in theNER response causes the human hereditary disease xeroderma pigmentosum(XP),which isfist found by professor Kaposi and characterized by extreme photosensitivity and a2000-fold increased incidence of sunlight-induced skin cancer.XP individuals also have ahigher incidence of internal tumors and tumors and, in some cases, neurological abnormalities,probably reflecting the importance of NER in the repair of endogenous DNA damage. Patientsaffected by this recessive disorder are classified into seven repair-deficient complementation groups designated XP-A through XP-G.XPA, a273amino acid protein, is involved in the early stage of the NERprocess.D.Mu.M.and E.evans find that in the xpa-/-mice, no NER occurs. XPA gene include6exons, and each exon have different function. The E1encode the structure of XPA proteinwhich interact with RPA34(another NER protein which protect the sing stand of DNA),andthe E2encode the structure of XPA protein which associates with ERCC1and essential for theNER activity. And the E3． E4． E5encode the structure of XPA protein for DNAbinding,which is the basic function of XPA. The C-Terminal Domain (E6) encode theTFIIH(transcription factor II).If the mutation occurs in every exon, the mutant XPA proteinwill attenuate the coefficient of the NER.XPA is an important confirmed DNA damage recognition protein and limiting speedprotein of NER.Its functional change or abnormal expression is highly associated to thedevelopment and chemotherapeutic sensitivity of tumor. In the absence of XPA, no stablepreincision complex can form, and no NER occurs. Gerdine J find that in the xpa-/-mice, theincidence of internal cancer including bladder cancer is more higher than normal mice. So, wecan suppose that the status of XPA expression is related to the bladder cancer tumorigenesis.XPF,also known as the excision repair crosscomplementing group4(ERCC4), iscritically involved in the NERpathway.XPF has an importantimportant role in recombinationrepair, mismatch repair and possibly immunoglobulin class switching. XPF contains thecatalytic domain of the nuclease, and ERCC1is required for DNA binding and stabilization ofXPF. The ERCC1-XPF complex can remove3' single-standed flaps from DNA ends andcleaves the5'side of a bubble in NER to excise toward the lesion.Because the XPA,XPF gene play an important role in the NER, in the first part,wedetect the polymorphism of XPA both in the bladder cancer and normal bladder patients.Thenwe analyze the relation between XPA polymorphism and the expression of XPA,Connectedwith the clinical data, we analyzed the clinical value of XPA genes and smoking by theKaplan-Meier method.In the end,we studied the relationship between the expression of XPAand the genomic instability.In the second part we investigate the expression and clinical significance of DNA repairgene xeroderma pigmentosum group F (XPF) in bladder cancer. Method1． In this study,we use the RELF detect the polymorphism of XPA(A23G andG709A),then we compaired the distribution of XPA polymorphism in in bladder cancerpopulation and the normal population,in the end we studied the relationship between XPApolymorphism and bladder cancer risk.2．We use the case-control study to analyze the link between the XPA promoterpolymorphism and XPA expression(real-time PCR detect the expression of XPA in bladdercancer tissue),the link between XPA promoter polymorphism and the occurrence andevolution of the bladder cancer, and ultimately defined the role of low expression and thepromoter polymorphism of XPA in the progression of bladder cancer.3．Through a clinical case-control study,to clear the link between the low expression ofthe XPA and the bladder cancer genomic instability,then siRNA targeting XPA was used toknock down the XPA expression in T24cells and5637cells to observethe cellular response toDNA damage agents after XPA down-regulated.4．In this part we investigate the expression and clinical significance of DNA repair genexeroderma pigmentosum group F (XPF) in bladder cancer.Results1．The relationship between A genetype of the XPA polymorphism and susceptibility tobladder cancer(1)In patients with bladder cancer and control populations, the A genetype of theXPA polymorphism has a lower distribution in bladder cancer patients,and has a higherdistribution in control populations.There was significant difference (P <0.05);(2)TheA23G genotype in the promoter of XPAis related to the risk of bladder cancer.The genotype A has a significant protective effect of the occurrence of bladder cancer, it canreduce the risk of bladder cancer by28%.(3)Smoking is an important factor in the development of bladder cancer.Furthermore,smoking can reduce the protective effect of the A genotype of XPA promoter polymorphismon bladder cancer.2．The relationship between XPA A23G polymorphism and the low expression of XPA inbladder cancer and its impact on the process of bladder cancer (1)The genotype of the XPApromoter polymorphism can affect the expression of XPA,the expression of XPA in genotype A corresponding cancer tissue was significantly higherthan genotype C corresponding tumor tissue;(2)The recurrence rate of bladder cancer inAgenotype corresponds to patients is lowerthan the C genotype corresponding to patients with bladder cancer;(3)The high expression of XPAcan inhibit the recurrence of bladder cancer.(4)Smoking as an independent factor that can increase the recurrence of bladdercancer.(5)Smoking can reduce the protective effect of the A genotype of XPA promoterpolymorphism.3．The low expression of XPA can exacerbated genomic instability of bladder cancer(1)The loss of heterozygosity occurrence rate of D9S283, D9S303, D9S1751wassignificantly higher in bladder cancer than in the normal bladder mucosa；(2)The low expression of the XPA related to the occurrence of D9S283, D9S303,D9S1751in bladder cancer tissues；(3)After the XPA interference,the rate of apoptosis of bladder cancer cell linesdecreased after cisplatin-treated.4． Increased expression of DNA repair gene XPF enhances resistance tohydroxycamptothecin in bladder cancerThe XPF expressions in the HCPT-treated cancer tissues was significantly higher thanthose in the untreated cancer tissues at both mRNA and protein levels. Importantly, theenhanced XPF expression decreased the sensitivity of T24cells and5637cells to HCPT.Furthermore, the HCPT treatment significantly increased the apoptosis of T24cells and5637cells. Alternatively, after the XPF gene silencing, the chemotherapeutic resistance of bladdercancer cells was significantly decreased.Conclution1．The genotypes of XPA promoter A23G can affect bladder cancer risk and progress.2．The genotypes of XPA promoter A23G can affect the expression of XPA in somedegree, but the reseason of the low experession of XPA is unknown,the mechanisms needfurther study. 3．The low expression of XPA is related to the recurrence of bladder cancer.4．The low expression of XPA can exacerbated genomic instability of bladder cancer.5．The increased expression of XPF involves in the chemotherapeutic resistance ofbladder cancer, and to decrease the XPF expression may become a promising therapeuticstrategy for bladder cancer.