Expression, Purification And Serological Analysis Of Cancer Testis Antigen SSX4

AIM:To investigate the utilizing value of SSX4 antibody for neoplasms in clinic diagnosis,the SSX4 antibody in sera of HCC,gastrointestinal Cancer, Lung Cancer,gynecological cancers,and health adult were detected by ELISA.METHOD:The recombinant vector of a SSX4 gene cDNA segment was introduced into E. coli TB1.The fusion protein,MBP-SSX4,was obtained by means of the expression of genetic engineering and the separation of affinity column.The non-fusion protein,SSX4 was procured after MBP-SSX4 was cut off by enzyme.The immunocompetence difference of SSX4 protein and SSX4 fused with MBP was analyzed using Western-Blot technique.SSX4 antibodies of the patient's serum of HCC, gastrointestinal Cancer and other cancer, and some health adult were detected by ELISA, and the results were analyzed statistically.RESULTS:(1) Here, 12 of 50 HCC sera samples (24%) and 5 of 21 samples (23.8%) of HCC with AFP(-) were shown to have SSX4 antibodies. (2) 5 of 50 (10%) sera samples of gastric carcinoma, 5 of 50 (10%) colon carcinoma samples, 3 of 50 (6%) Lung Cancer samples, and 1 of 50 (2%) gynecological cancers samples were detected to have the SSX4 antibodies. As control, no antibodies against SSX4 were detected in 50 samples from healthy individuals. (3) The sensitivity, the specificity, the positive predictive value, the negative predictive value, the positive likelihood ratio, and the negative likelihood ratio of diagnosing HCC with SSX4 were 24%, 94.4%, 46%, 86.1%, 4.2, and 0.8, respectively. In our experiment, the sensitivity of diagnosing HCC with AFP lonely was 58% (29/50), and when using AFP and SSX4, it increased to 68%, which suggested that SSX4 antibody could complement for the diagnosis of HCC in patients with AFP negative. (4) The HCC patients'ratio with the SSX4 antibodies was independent of their age. However, there are distinct differences in the positive ratios between the HCC patients whose tumor size larger than 5 centimeter and the other.CONCLUSION:The detection of the antibodies against SSX4 had the specificity for the diagnosis of HCC. The early diagnosis of HCC with AFP negative plays assisting role. The presence of SSX4 antibody in HCC patients is independent of their age, but there is dependability between the antibodies against SSX4 of HCC and the size of HCC.