肝细胞癌的蛋白质组学研究进展

Effect of overexpression of wild-type p53 on POLD1 expression and malignant cell behavior in human hepatocellular carcinoma cell line SMMC-7721

AIM: To investigate the impact of overexpression of wild-type p53 on cell proliferation and malignant phenotype in human hepatocellular carcinoma cell line SMMC-7721 and to explore possible mechanism involved.

METHODS: Enhanced green fluorescence protein gene-containing eukaryotic expression plasmids expressing p53-specific small interfering RNA (shRNA) (p53-siRNA) or wild-type p53 (pEGFP-p53) were constructed and introduced into SMMC-7721 cells by Lipofection-2000-mediated transfection. Meanwhile, the pEGFP-C1 empty vector was also transfected into SMMC-7721 cells. Cell lines stably expressing p53-siRNA, pEGFP-p53 or pEGFP-C1 were screened in medium containing G418. After transfection, the expression of p53 and POLD1 mRNAs was detected by RT-PCR. The changes in malignant cell behavior were determined by cell growth curve determination and colony formation assay.

RESULTS: Compared to control SMMC-7721 cells, p53 mRNA expression was increased and POLD1 gene expression was decreased in SMMC-7721 cells transfected with the plasmid carrying wild-type p53 gene, while p53 mRNA expression was reduced and POLD1 mRNA expression was increased in SMMC-7721 cells transfected with the plasmid carrying p53-siRNA. MTT results showed that cell growth rate was faster in SMMC-7721 cells transfected with the plasmid carrying p53-siRNA than in control SMMC-7721 cells, but was slower in SMMC-7721 cells transfected with the plasmid carrying wild-type p53 gene than in control cells. Colony formation assay showed that colony formation rate was lower in SMMC-7721 cells transfected with the plasmid carrying wild-type p53 gene than in control cells (38.1% vs 52.6%, P < 0.05), but was higher in cells tranfected with the plasmid carrying p53-siRNA than in control cells (72.6% vs 52.6%, P < 0.05). High expression of wild-type p53 inhibited POLD1 transcription and cell proliferation, while low expression of wild-type p53 promoted POLD1 transcription and cell proliferation.

CONCLUSION: Wild-type p53 controls liver cancer cell proliferation and malignant phenotype possibly by regulating POLD1 expression.

Significance of POLD1 expression in primary hepatocellular carcinoma

AIM: To investigate the significance of expression of DNA polymerase delta catalytic subunit gene (POLD1) and its protein product p125 in hepatocellular carcinoma (HCC).

METHODS: The expression of POLD1 mRNA and protein in 20 surgically resected HCC tissue samples was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTS: The expression level of POLD1 mRNA was significantly higher in HCC than in matched tumor-adjacent noncancerous tissue (0.70 ± 0.34 vs 0.37 ± 0.23, P < 0.05). The expression level of p125 in HCC was also significantly higher than that in tumor-adjacent tissue (0.63 ± 0.19 vs 0.39 ± 0.21, P < 0.05). p125 expression was correlated with tumor size and clinical stage, but not with HBV infection, age and sex in HCC.

CONCLUSION: POLD1 mRNA and protein expression is significantly correlated with pathological stage of HCC. POLD1 may be used as a diagnostic maker and a potential therapeutic target for HCC.