Cloning and expression of MXR7 gene in human HCC tissue

AIM:To clone and identify the whole cDNA of MXR7 gene and to find out its expression in human HCC, and normal tissues.METHODS:The DNA primers were designed and synthesized according to the whole cDNA sequence of MXR7 gene. The cDNA of human HCC was taken as the template while the cDNA of MXR7 gene was synthesized by polymerase chain reaction (PCR). Recombinant DNA conforming to reading frame was constructed by connecting purified PCR product of the cDNA of MXR7 gene with expression vector pGEX-5X-1 of fusion protein. The plasmid MXR7/pGEX-5X-1 was identified by sequencing. Using (32)P labeled MXR7 cDNA as probe, MXR7 mRNA expression was detected by Northern blot analysis in 12 different human normal tissues, 7 preoperatively untreated non-liver tumor tissues, 30 preoperatively untreated HCC, the paracancerous liver tissues and 12 normal liver tissues samples.RESULTS:Restriction enzyme and sequence analysis confirmed that the insertion sequence in vector pGEX-5X-1 was the same as the cDNA sequence of MXR7 gene. Northern blot analysis showed no expression of MXR7 mRNA in 12 kinds of normal human tissues including liver, 7 tumor tissues in other sites and 12 normal liver tissues, the frequencies of MXR7 mRNA expression in HCC and paracancerous liver tissues were 76.6% and 13.3%, respectively. The frequency of MXR7 mRNA expression in HCC without elevation of serum AFP and in HCC <5cm was 90% (9/10) and 83.3% (5/6), respectively.CONCLUSION:MXR7 mRNA is highly expressed in human HCC, which is specific and occurs at an early stage of HCC, suggesting MXR7 mRNA can be a tumor biomarker for HCC. The detection of MXR7 mRNA expression in the biopsied liver tissue is helpful in discovering early subclinical liver cancer in those with negative serum AFP.