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Mutational status of EGFR and KIT in thymoma and thymic carcinoma
Kiyotaka Yoh1, Yutaka Nishiwaki, Genichiro Ishii
1Division of Thoracic Oncology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan. kyoh@east.ncc.go.jp
Abstract:
This study was conducted to evaluate the prevalence of EGFR and KIT mutations in thymomas and thymic carcinomas as a means of exploring the potential for molecularly targeted therapy with tyrosine kinase inhibitors. Genomic DNA was isolated from 41 paraffin-embedded tumor samples obtained from 24 thymomas and 17 thymic carcinomas. EGFR exons 18, 19, and 21, and KIT exons 9, 11, 13, and 17, were analyzed for mutations by PCR and direct sequencing. Protein expression of EGFR and KIT was evaluated immunohistochemically. EGFR mutations were detected in 2 of 20 thymomas, but not in any of the thymic carcinomas. All of the EGFR mutations detected were missense mutations (L858R and G863D) in exon 21. EGFR protein was expressed in 71% of the thymomas and 53% of the thymic carcinomas. The mutational analysis of KIT revealed only a missense mutation (L576P) in exon 11 of one thymic carcinoma. KIT protein was expressed in 88% of the thymic carcinomas and 0% of the thymomas. The results of this study indicate that EGFR and KIT mutations in thymomas and thymic carcinomas are rare, but that many of the tumors express EGFR or KIT protein.
Insights
EGFR and KIT mutations are rare in thymomas and thymic carcinomas. However, many tumors express EGFR or KIT protein, suggesting potential for targeted therapies.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Thymomas and thymic carcinomas are rare tumors of the thymus.
- Molecularly targeted therapies, such as tyrosine kinase inhibitors, offer potential treatment avenues.
- Epidermal Growth Factor Receptor (EGFR) and KIT are key targets in various cancers.
Purpose of the Study:
- To investigate the prevalence of EGFR and KIT mutations in thymomas and thymic carcinomas.
- To assess the potential for using tyrosine kinase inhibitors in treating these thymic malignancies.
Main Methods:
- Genomic DNA extraction from 41 paraffin-embedded thymic tumor samples (24 thymomas, 17 thymic carcinomas).
- Polymerase Chain Reaction (PCR) and direct sequencing to analyze EGFR and KIT gene mutations.
- Immunohistochemistry to evaluate EGFR and KIT protein expression.
Main Results:
- EGFR mutations were found in 2 of 20 thymomas (both missense mutations in exon 21), but none in thymic carcinomas.
- EGFR protein expression was observed in 71% of thymomas and 53% of thymic carcinomas.
- A single KIT missense mutation (L576P in exon 11) was detected in one thymic carcinoma.
- KIT protein expression was high in thymic carcinomas (88%) but absent in thymomas (0%).
Conclusions:
- EGFR and KIT mutations are infrequent in thymomas and thymic carcinomas.
- Despite rare mutations, significant EGFR and KIT protein expression indicates potential therapeutic targets.
- Further research into targeted therapies for thymic malignancies warrants consideration.
