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Analysis of transforming growth factor (TGF)-alpha/epidermal growth factor receptor, hepatocyte growth
1Laboratory of Experimental Carcinogenesis, Division of Basic Sciences, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
Abstract:
Experimental data suggest that dysregulation of growth factors and the cognate receptors may play an important role in hepatocarcinogenesis. The objective of the present study was to characterize the expression of two hepatotrophic growth factor/receptor systems [transforming growth factor-alpha/epidermal growth factor receptor (TGF-alpha/EGFR) and hepatocyte growth factor/c-met receptor (HGF/c-met)], both of which are implicated in the development of human liver tumors. In addition, we have analyzed the expression of transforming growth factor-beta receptor type II (TGF-beta-RII) and p53, genes associated with growth inhibition and tumor suppression, respectively. Surgical biopsy specimens from 86 human hepatocellular carcinomas were analyzed. TGF-alpha was overexpressed in 17%, equally expressed in 21%, and down-regulated in 62% of the hepatocellular carcinomas when compared to the surrounding hepatic tissue. No major changes were found with EGFR expression. HGF was over-expressed in 33% and down-regulated in 21% of the tumors. The c-met receptor was overexpressed in 20%, equally expressed in 48%, and down-regulated in 32% of the neoplasms. In contrast, TGF-beta-RII was overexpressed in only 8%, equal in 42%, and down-regulated in 50% of tumors. Nuclear staining of p53, indicative of a mutation(s), was observed in the great majority of the tumors (80%), whereas no nuclear p53 was detected in peritumoral tissues. Interestingly, simultaneous down-regulation of c-met and TGF-beta-RII was observed in 23% of the hepatocellular carcinomas, 85% of which also showed nuclear p53 staining. Taken together, our data suggest that down-regulation of c-met and TGF-beta-RII may, together with p53 mutations, play a significant role in human liver carcinogenesis.
Insights
Dysregulation of growth factors like transforming growth factor-alpha (TGF-alpha) and hepatocyte growth factor (HGF), along with their receptors, is linked to liver cancer. Down-regulation of c-met and TGF-beta receptor type II (TGF-beta-RII), coupled with p53 mutations, significantly contributes to hepatocarcinogenesis.
Area of Science:
- Hepatology and Cancer Biology
- Molecular Oncology
- Biochemistry of Growth Factors
Background:
- Growth factors and their receptors are crucial in cell growth and differentiation.
- Aberrant signaling pathways involving growth factors are implicated in various cancers, including hepatocellular carcinoma (HCC).
- Specific systems like transforming growth factor-alpha/epidermal growth factor receptor (TGF-alpha/EGFR) and hepatocyte growth factor/c-met receptor (HGF/c-met) are known to influence liver development and tumorigenesis.
Purpose of the Study:
- To investigate the expression patterns of key growth factor/receptor systems (TGF-alpha/EGFR, HGF/c-met) in human hepatocellular carcinoma.
- To analyze the expression of growth inhibitory and tumor suppressor genes, specifically transforming growth factor-beta receptor type II (TGF-beta-RII) and p53.
- To correlate the expression of these molecules with the development of liver tumors.
Main Methods:
- Analysis of surgical biopsy specimens from 86 human hepatocellular carcinoma (HCC) cases.
- Quantitative assessment of gene and protein expression levels for TGF-alpha, EGFR, HGF, c-met, TGF-beta-RII, and p53.
- Comparison of expression levels in tumor tissues versus surrounding non-cancerous hepatic tissue.
- Detection of p53 mutations through nuclear staining.
Main Results:
- TGF-alpha showed variable expression (overexpressed, equal, down-regulated) in HCC compared to normal tissue.
- EGFR expression remained largely unchanged.
- HGF and its receptor c-met exhibited altered expression, with overexpression and down-regulation observed in a significant portion of tumors.
- TGF-beta-RII was frequently down-regulated.
- Mutations in p53, indicated by nuclear staining, were present in 80% of HCCs.
- A notable subset of HCCs (23%) displayed simultaneous down-regulation of c-met and TGF-beta-RII, with 85% of these also showing p53 mutations.
Conclusions:
- The study highlights complex expression changes of growth factor systems in human HCC.
- Down-regulation of c-met and TGF-beta-RII, in conjunction with p53 mutations, appears to be a significant pathway in human liver carcinogenesis.
- These findings provide insights into the molecular mechanisms underlying HCC development and suggest potential therapeutic targets.