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The ras gene family in human non-small-cell lung cancer
1Division of Experimental Therapy, The Netherlands Cancer Institute, Amsterdam.
Abstract:
The three ras genes code for proteins with a putative role in cellular signal transduction. They belong to a larger family of small guanosine-triphosphate (GTP)-binding proteins. The ras proteins acquire transforming activity when amino acids are substituted at one of a few specific sites, as a result of a point mutation in the gene. In about one third of adenocarcinomas of the lung, a K-ras mutation is present in codon 12 of the gene. Patients with early stages of K-ras mutation-positive tumors have a very unfavorable prognosis, even if apparently radical resection of the tumor has taken place. K-ras mutations are very rare among nonsmokers, and it is reasonable to assume that carcinogens in tobacco smoke directly cause the mutation. The types of ras mutations found in lung cancer are different from those in gastrointestinal malignancies. Colon cancer is mainly associated with mutations leading to substitution of the normal glycine at amino acid position 12 of K-ras by either valine or aspartic acid, and mutations in N-ras are not exceptional. In contrast, the predominant mutation in lung cancer leads to substitution of cysteine in codon 12. Several other members of the ras gene superfamily are also expressed in human lung cancer, but a possible relationship with lung tumorigenesis remains to be established.
Insights
K-ras mutations in lung adenocarcinoma are linked to poor prognosis and may be caused by tobacco carcinogens. These mutations differ from those found in colon cancer, with cysteine substitution common in lung tumors.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Ras genes encode guanosine-triphosphate (GTP)-binding proteins crucial for cellular signal transduction.
- Point mutations in ras genes can activate proteins, leading to cellular transformation and cancer.
- K-ras mutations are frequently observed in lung adenocarcinomas, particularly in codon 12.
Purpose of the Study:
- To investigate the prevalence and characteristics of ras gene mutations in lung cancer.
- To compare ras mutation patterns in lung cancer with those in gastrointestinal malignancies.
- To explore the potential link between K-ras mutations and prognosis in early-stage lung adenocarcinoma.
Main Methods:
- Analysis of ras gene mutations in tumor samples from lung adenocarcinoma patients.
- Comparison of mutation data with clinical outcomes and patient history (e.g., smoking status).
- Comparative analysis of ras mutation types across different cancer types (lung vs. gastrointestinal).
Main Results:
- K-ras mutations are present in approximately one-third of lung adenocarcinomas.
- K-ras mutations in codon 12 are associated with an unfavorable prognosis in early-stage lung cancer.
- K-ras mutations are rare in non-smokers, suggesting a role for tobacco carcinogens.
- Lung cancer predominantly shows cysteine substitution at codon 12, differing from colon cancer's glycine substitutions.
- Ras gene superfamily members are expressed in lung cancer, but their specific role requires further investigation.
Conclusions:
- K-ras mutations, particularly at codon 12, are significant oncogenic drivers in lung adenocarcinoma with prognostic implications.
- Tobacco smoke is a likely causative agent for K-ras mutations in lung cancer.
- Distinct ras mutation profiles exist between lung and gastrointestinal cancers, indicating tissue-specific mechanisms.
- Further research is needed to elucidate the role of other ras superfamily members in lung tumorigenesis.