Published online Feb 15, 2000. doi: 10.3748/wjg.v6.i1.57
Revised: September 2, 1999
Accepted: September 20, 1999
Published online: February 15, 2000
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 accordin g to the whole cDNA sequence of MXR7 gene. The cDNA of human HCC was taken a s the template while the cDNA of MXR7 gene was synthesized by polymerase cha in reaction (PCR). Recombinant DNA conforming to reading frame was constructed b y connecting purified PCR product of the cDNA of MXR7 gene with expression v ector pGEX-5X-1 of fusion protein. The plasmid MXR7/pGEX-5X-1 was identi fied by sequencing. Using 32P labeled MXR7 cDNA as probe, MXR7 mRNA expression was detected by Northern blot analysis in 12 different human no rmal tissues, 7 preoperatively untreated non-liver tumor tissues, 30 preoperati vely untreated HCC, the paracancerous liver tissues and 12 normal liver tissues samples.
RESULTS: Restriction enzyme and sequence analysis confirmed tha t 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 si tes 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 < 5 cm 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.