Study On The Loss Of Heterozygosity And Protein Expression Of NRG1in Hepatocellular Carcinoma

[Background]Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. The occurrence of it is a multi-gene change and multi-step accumulation process, genetic factors play an important role in its occurrence and development. Neuregulin1(NRG1) mapped onto chromosome8p12, is a new tumor suppressor gene which is found recently in a wide variety of tumors with loss of heterozygosity(LOH). The relationship between NRG1and HCC has not been reported.[Objective]To analyze the LOH of the two microsatellites D8S278and D8S499of NRG1in HCC and the relationship between LOH and NRG1expression level in HCC tissues; to investigate the role of NRG1in the occurrence and development of HCC and the possible mechanism that how NRG1play a role in HCC.[Methods](1)74HCC tissues and adjacent normal tissues were collected, DNAs were extracted from these specimens using phenol-chloroform, and were qualified by agarose gel electrophoresis and ultraviolet photometry.(2) The primers of two microsatellite loci D8S278and D8S499of NRG1were designed by GenBank database, then synthesized and amplified by PCR.(3) The products of PCR were electrophoresed in denaturing polyacrylamide gel and stained using silver nitrate. The states of LOH at these two loci in HCC were analyzed comparing with the normal tissues.(4) The expressions of NRG1in74HCC tissues and their adjacent tissues were detected using immunohistochemical method.(5) The data were analyzed by SPSS17.0statistical software.[Results](1) There are74informative individuals of the D8S278,24cases have LOH, the rate of LOH is32.43%; in the69informative individuals of the D8S499, there are26cases have LOH, the frequency is37.86%. The total frequency of LOH was48.65%(36/74) at least one locus, and in7cases, they have LOH at both loci.(2) The positive rate of NRG1protein in normal tissues was97.30%(72/74), but in HCC tissues, it was about67.57%(50/74), which was significantly lower than in normal tissues (P<0.05).(3) In the LOH-positive group, the cases in which NRG1expression were reduction or absentation were more than LOH-negative group, there is a significant difference between the two groups(P<0.05). The down-regulation of NRG1was associated with tumor size and Edmondson grade(P=0.02, P=0.01), but there was no association with age, gender, HBsAg, AFP, hepatic cirrhosis and intra-and extrahepatic metastasis.[Conclusions](1) The microsatellites of NRG1have high frequency of LOH in HCC, which indicated that NRG1may be a candidate tumor suppressor gene in HCC.(2) The expression of NRGl in HCC was reduced or deleted, playing an important role in tumorigenesis and development.(3) The mechanism of inactivation of the NRG1gene may due to the loss of heterozygosity.(4) NRG1was closely related with tumorigenesis and development, so, detection of NRG1may provides molecular basis for diagnosis and prognosis of HCC, besides, it may also provides new candidate target gene for targeted therapies.