Impact of epidermal growth factor receptor protein and gene alteration on Taiwanese hepatocellular carcinomas.

BACKGROUND AND AIM: Epidermal growth factor receptor (EGFR) overexpression is associated with disease progression and poor survival in a variety of solid tumors. The role of EGFR in hepatocellular carcinoma (HCC) remains controversial. METHODS: One hundred thirty-eight HCCs were analyzed for total EGFR (t-EGFR) and phospho-EGFR (p-EGFR) expression and gene amplification using immunohistochemistry and fluorescence in situ hybridization. The role of EGFR was analyzed in relation to the clinicopathological features. RESULTS: Weak to strong p-EGFR immunostaining was noted in 42 of the 138 HCCs. p-EGFR expression correlated with alcoholism (P = 0.03) and chronic hepatitis B infection (P = 0.041). There was no correlation between t-EGFR expression and any of the clinicopathological features. Amplification of the EGFR gene was not identified in the 138 HCCs, but 39.1% of the HCCs showed balanced polysomy of both the EGFR gene and centromere 7. Moreover, 65 tumors showed > 2.2 copies per tumor cell. EGFR copy number gain (CNG) was significantly correlated with gender (P = 0.0491), tumor grade (P = 0.006), and vascular invasion (P = 0.005). HCCs with EGFR CNG also had a poor recurrence-free survival (RFS), as compared with HCCs without EGFR CNG (P = 0.031). When exploring the impact of gender, a significant association of EGFR CNG was found with tumor grade (P = 0.044) and cirrhosis (P = 0.015) exclusively in the male group only; however, the OS and RFS analysis show no significant difference between male and female groups. CONCLUSIONS: EGFR CNG was related to crucial clinicopathological features and early recurrence, indicating that EGFR CNG might be a poor prognosis factor for Taiwanese HCC.

Essential role of ß-human 8-oxoguanine DNA glycosylase 1 in mitochondrial oxidative DNA repair.

8-Oxoguanine (8-OG) is the major mutagenic base lesion in DNA caused by reactive oxygen species (ROS) and accumulates in both nuclear and mitochondrial DNA (mtDNA). In humans, 8-OG is primarily removed by human 8-OG DNA glycosylase 1 (hOGG1) through the base excision repair (BER) pathway. There are two major hOGG1 isoforms, designated α- and ß-hOGG1, generated by alternative splicing, and they have distinct subcellular localization: cell nuclei and mitochondria, respectively. Using yeast two-hybrid screening assays, we found that ß- but not α-hOGG1 directly interacts with the mitochondrial protein NADH:ubiquinone oxidoreductase 1 beta subcomplex 10 (NDUFB10), an integral factor in Complex 1 on the mitochondrial inner membrane. Using coimmunoprecipitation and immunofluorescence studies, we found that this interaction was greatly increased by hydrogen peroxide-induced oxidative stress, suggesting that ß- but not α-hOGG1 is localized in the mitochondrial inner membrane. Analyses of nuclear and mtDNA damage showed that the ß- but not α- hogg1 knockdown (KD) cells were severely defective in mitochondrial BER, indicating an essential requirement of ß-hOGG1 for mtDNA repair. ß-hogg1 KD cells were also found to be mildly deficient in Complex I activity, suggesting that ß-hOGG1 is an accessory factor for the mitochondrial integral function for ATP synthesis. In summary, our findings define ß-hOGG1 as an important factor for mitochondrial BER and as an accessory factor in the mitochondrial Complex I function.