AIM To clone and identify the whole cDNA ofMXR7 gene and to find out its expression inhuman HCC,and normal tissues.METHODS The DNA primers were designed andsynthesized according to the whole cDNAsequence of MXR? gene.The cDNA of humanHCC was taken as the template while the cDNA ofMXR7 gene was synthesized by polymerasechain reaction(PCR).Recombinant DNAconforming to reading frame was constructed byconnecting purified PCR product of the cDNA ofMXR? gene with expression vector pGEX-5X-1 offusion protein.The plasmid MXRT/pGEX-5X-1was identified by sequencing.Using32p labeledMXR? cDNA as probe,MXR7 mRNA expressionwas detected by Northern blot analysis in 12different human normal tissues,7 preoperativelyuntreated non-liver tumor tissues,30preoperatively untreated HCC,theparacancerous liver tissues and 12 normal livertissues samples.RESULTS Restriction enzyme and sequenceanalysis confirmed that the insertion sequence invector pGEX-5X-1 was the same as the cDNAsequence of MXR7 gene.Northern blot analysisshowed no expression of MXR? mRNA in 12 kindsof normal human tissues including liver,7 tumortissues in other sites and 12 normal livertissues,the frequencies of MXR7 mRNA expression in HCC and paracancerous livertissues were 76.6% and 13.3%,respectively.The frequency of MXR7 mRNA expression in HCCwithout elevation of serum AFP and in HCC<5cm was 90%(9/10)and 83.3%(5/6),respectively.CONCLUSION MXR7 mRNA is highly expressedin human HCC,which is specific and occurs at anearly stage of HCC,suggesting MXR7 mRNA canbe a tumor biomarker for HCC.The detection ofMXR7 mRNA expression in the biopsied livertissue is helpful in discovering early subclinicalliver cancer in those with negative serum AFP.
