Soluble Expression of Recombinant Human Smp30 for Detecting Serum Smp30 Antibody Levels in Hepatocellular Carcinoma Patients

Senescence marker protein 30 (SMP30), a hepatocellular carcinoma (HCC) associated antigen, was earliershown by our research group to be highly expressed in HCC paracancerous tissues, but have low levels in HCCtissues. In order to detect anti-SMP30 antibody in serum of HCC patients, we established pET30a-SMP30 andpColdIII-SMP30 expression systems in Escherichia coli. However, the expression product was mainly in the formof inclusion bodies. In this research, we used several combinations of chaperones, four molecular chaperoneplasmids with pET30a-SMP30 and five molecular chaperone plasmids with pColdIII-SMP30 to increase theamount of soluble protein. Results showed that co-expression of HIS-SMP30 with pTf16, combined with theaddition of osmosis-regulator, and a two-step expression resulted in the highest enhancement of solubility. A totalof 175 cases of HCC serum were studied by ELISA to detect anti- SMP30 antibody with recombinant SMP30protein. Some 22 were positive and x2 two-sided tests all showed P>0.05, although it remained unclear whetherthere was a relationship between positive cases and clinical diagnostic data.