A Study On The Expression Of FAT10 In Human Gastric Cancer And The Correlation Between FAT10 And Mutant P53

BackgroundFAT10 is an 18KD protein comprising 165 amino-acid residues. It wasoriginally discovered through the identification of expressed genes covering theHLA-F genomic locus. A potential role of FAT10 in antigen presentation wassuggested by its expression in mature B cells and dendritic cells, and by its ability tobe generally and synergistically inducible with cytokines IFN_γand TNFα. FAT10belongs to the UBL family of proteins and contains two ubiquitin-like moietiesfused in tandem. It is 29% identical to ubiquitin at its N-terminus and 36% identicalat the C-terminus. It has the C-terminal Gly-Gly residues and there is a comservedLys residue in each moiety of FAT10 analogous to Lys 48 of ubiquitin, which mayserve as a potential site for polyubiquitination of FAT10. FAT10 has been reported tohave potential involvement in cell-cycle regulation and shown to bind noncovalently to the human spindle assembly checkpoint protein, MAD2, a protein responsible formaintaining spindle integrity suring mitosis. The inhibition of MAD2 function hasbeen associated with chromosomal instability, a characteristic of many tumoursoccurrence. It was reported that FAT10 expression in the nucleus of HCChepatocytes rather than the surrounding immune or non-HCC cells. FAT10overexpression was also found in other cancers of the gastrointestinal tract andgynecology. FAT10 may modulate tumorigenesis through its reported interactionwith the MAD2 spindle-assembly checkpoint protein.Recently, It is reported that p53 is likely an upstream regulator of FAT10 andmay link FAT10 in the tumorigenesis process. As FAT10 was found to interact withMAD2, an hypothesis would be that the repression of FAT10 expression by p53may facilitate the interaction of MAD2 with cell division cycle 20 (CDC20)to induce mitotic arrest. P53 gene mutation may lead to the enhancement of FAT10gene expression during tumorigenesis. These results were observed in severaldifferent cancers. FAT10 overexpression may result in the deregulation of mitosis,cause genome instability and tumorigenesis.Gastric cancer is one of the most common malignant tumor and a leading causeof mortality world-wide. With the development and appliance of molecule biologicaltechnology, research in the mechanism of gastric cancer has probed into the level ofgene. But, it hadn't been identified the specific marker of molecule pathology ingastric cancer yet. For a tumor to become established, compromises in the control oftumor related gene are necessary. The Ubiquitin-like modifier (UBL) which has generated much interest in the scientific community is implicated to play importantrole in gastric cancer. Previous study was concerned mainly about the struction ofthe FAT10, the character of its expression, its inducible factor and the function.There are no reports about the relationship between the expression of FAT10 proteinand mRNA and the characters of clinical pathology and correlation betweenFAT10 and mutant p53 in gastric cancer.ObjectiveTo investigate the expression of FAT10 and mutant p53 gene in the gastriccancerous tissue, latero-GC tissue and the normal gastric mucosa tissue from thelevel of cellular and molecular biology. To analyse the relationship of expression inFAT10 protein and gene and clinical pathological features of gastric cancer and thecorrelation between the FAT10 and mutant p53 expression in gastric cancer tissue.To explore the effects of FAT10 in the production , invasion and metastasis processof gastric cancer.Materials and MethodsSixty-two samples which excisional specimen by operation confirmed asgastric cancer through pathological section in our hospital from March, 2003 to May,2004 were selected to study. The expression levels of FAT10 , FAT10-mRNA,mutant p53 and mutant p53-mRNA in the 62 specimens of gastric cancerous tissue,corresponding latero-GC tissue and normal mucosa tissue were determinedrespectively with the method of immunohistochemistry and RT-PCR. The featuresof expression of FAT10, FAT10-mRNA, mutant p53 and p53-mRNA in the sampleof gastric cancerous tissue, corresponding latero-GC tissue and normal mucosa tissue were analysed and the relationships between FAT10 overexpression with theinformation of age, sex, diameter of tumour, the location of tumor occurrence,invasion, differentiation, lymph nodes metastasis, distant metastasis and TNM stagesof the gastric cancer were observed. Kaplan-Meier survivial plot for patients withgastric cancer according to tumor expression of FAT10 and multivariate Coxproportional hazards model analysis of prognosis factors were studied.Results1,Immunohistochemistry1) The rate of the FAT10's overexpression in the tissue of GC(51.61%) issiginificantly higher than that in latero-GC tissue and normal mucosa tissue(12.90%, 6.45%), the comparison between them:P<0.01.2) The rate of the p53's positive expression in the tissue of GC(45.16%) issiginificantly higher than that in latero-GC tissue and normal mucosa tissue(14.51%,9.68%), the comparision between them:P<0.01. There are nosiginificant differences of the rate of the FAT10's and p53's positiveexpression between tissue in latero-GC and normal mucosa samples.3) The rate of FAT10's overexpression in the tissue of GC with the lymphnodes metastasis (64.10%) is siginificantly higher than that without nodesmetastasis (30.43%), the comparision between them :P<0.05. And the rateof FAT10's overexpression in the TNM stageⅢ+Ⅳ(60.98%) issiginificantly higher than the TNM stageⅠ+Ⅱof GC (33.30%), thecomparision between them :P<0.05. Comparision the age,sex,diameter of tumour, the location of tumor occurrence,invasion,differentiation and distantmetastasis of the GC is no significant differences in the rate of FAT10'soverexpression.2,RT-PCR analysis4) The level of FAT10-mRNA expression in GC tissue is significantly higherthan that of latero-GC tissue and normal mucosa tissue (0.689±0.023,0.463±0.019 and 0.451±0.028), the comparision between them:P<0.01.5) The level of mutant p53-mRNA expression in GC tissue is significantlyhigher than that latero-GC tissue and normal mucosa tissue (0.471±0.021, 0.398±0.017 and 0.421±0.019), the comparision betweenthem:P<0.01.6) The level of FAT10-mRNA overexpression in the tissue of GC with thelymph nodes metastasis (0.656±0.016) is siginificantly higher than thatwithout nodes metastasis (0.531±0.026), the comparision betweenthem :P<0.01. And the level of FAT10's overexpression in the TNM stageⅢ+Ⅳ(0.667±0.023) is siginificantly higher than the TNM stageⅠ+ⅡGC(0.558±0.015), the comparision between them :P<0.05. Comparisionthe age, sex,diameter of tumour, the location of tumor occurrence,invasion,differentiation and distant metastasis of the GC is no significant differencesin the level of FAT10-mRNA overexpression. 3,Correlation Analysis1) Immunohistochemistry shows: The rate of the positive expression of FAT10in the p53 positive samples is 82.14%(23/28). And 26.47%(9/34) of FAT10is overexpression in p53 negative expression group. Spearman orderprobabilities shows significant positive correlation with FAT10 and mutantp53(r=0.865, P<0.05).2) RT-PCR shows: Pearson correlation shows significant positive correlationwith mutant p53 and FAT10(r=0.761, P<0.01).4,Surviving rate Analysis shows: both overexpression of FAT10 protein and mRNAhave significant correlation with the life span of gastric cancer patients (P<0.05).Multivariate Cox proportional hazards model analysis of prognosis factorsshows:FAT10 protein and mRNA overexpression,lymph node and distantmetastases, TNM stage and p53 protein and mRNA overexpression are allsignificant in the multivariate analysis.Conclusions1. FAT10 overexpression plays important role in the process of the production,growth of gastric cancer. The level of FAT10's expression is related with thelymph nodes metastasis and TNM stages of the gastric cancer and isn't obviouslyrelated with the age,sex,diameter of tumour, the location of tumoroccurrence,invasion,differentiation and distant metastasis of the gastric cancer.2. Mutant p53 overexpression plays important role in the process of the production,growth of gastric cancer. 3. FAT10 and mutant p53 are tightly related in the expression of gastric cancer.Mutant p53 intervenes the expression of FAT10. We suppose it's one pathwaysthat mutant p53 gene arouses FAT10 gene overexpression and accelerates thetumor's growth.4. Both overexpression of FAT10 protein and mRNA have significant correlationwith the life span of gastric cancer patients and may be one of the most reliableindependent prognostic predictors.