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Growth control by epidermal growth factor and transforming growth factor-alpha in human lung squamous carcinoma cells
G J Rabiasz1, S P Langdon, J M Bartlett
1ICRF Medical Oncology Unit, Western General Hospital, Edinburgh, UK.
Abstract:
Although EGF receptor expression is generally elevated in human lung squamous carcinoma, the biological significance of this phenomenon and the role of EGF and TGF-alpha in this disease are poorly understood. We have investigated three human lung squamous carcinoma cell lines (NX002, CX140 and CX143) and have shown, using an antibody (EGFR1) directed against the EGF receptor, that the majority of cells in all three lines express the EGF receptor. Using a ligand binding assay, Scatchard analysis indicated high concentrations (1,300-2,700 fmol mg-1 protein) of a single low affinity binding site (Kd = 3-5 nM) within these lines. Addition of EGF or TGF-alpha at concentrations greater than 0.1 nM resulted in growth inhibition of all three lines and this was associated with an accumulation of cells in the G2/M phase of the cell cycle. Growth inhibitory effects were not explained by an enhancement of cellular differentiation as monitored by involucrin expression and the ability to form cornified envelopes. While the presence of EGF could not be detected in medium conditioned by the NX002 cell line, mRNA for TGF-alpha was detected in all three lines suggesting the possibility of an autocrine loop. These results together with reports of growth inhibition by EGF and TGF-alpha in other systems suggest that EGF and similar molecules might have a growth regulatory role in lung cancer cells and modulation of such may have therapeutic potential.
Insights
Epidermal Growth Factor (EGF) and TGF-alpha inhibit lung squamous carcinoma cell growth by halting the cell cycle. This suggests potential therapeutic strategies targeting these growth factors in lung cancer.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Epidermal Growth Factor (EGF) receptor is often elevated in lung squamous carcinoma.
- The roles of EGF and TGF-alpha in this cancer are not well understood.
Purpose of the Study:
- To investigate the expression and function of the EGF receptor in human lung squamous carcinoma cell lines.
- To explore the effects of EGF and TGF-alpha on the growth of these cells.
Main Methods:
- Utilized antibody EGFR1 to detect EGF receptor expression.
- Employed ligand binding assays and Scatchard analysis for receptor characterization.
- Assessed cell cycle progression and differentiation markers (involucrin, cornified envelopes).
Main Results:
- All three lung squamous carcinoma cell lines expressed EGF receptors with high concentrations and low affinity binding sites.
- EGF and TGF-alpha inhibited cell growth, causing G2/M phase arrest.
- No evidence of enhanced differentiation was observed; TGF-alpha mRNA was detected, suggesting autocrine signaling.
Conclusions:
- EGF and TGF-alpha exhibit growth-inhibitory effects on lung squamous carcinoma cells.
- These findings suggest a potential autocrine loop and therapeutic implications for targeting EGF signaling pathways in lung cancer.