Expression and mutation statuses of epidermal growth factor receptor in thymic epithelial tumors.
BACKGROUND
Epidermal growth factor receptor (EGFR) gene mutations have been reported to correlate with the sensitivity to the tyrosine kinase inhibitor treatment for advanced lung cancers. Since several reports have shown that invasive thymoma overexpress the EGFR protein, we examined the EGFR expression and mutation statuses in thymoma and thymic carcinoma tissues.


METHODS
EGFR mutation statuses from 99 thymic epithelial tumor samples were evaluated by a rapid and sensitive TaqMan assay using Applied Biosysytems 7500 real-time PCR system. Probes were designed according to the 13 different EGFR mutations reported previously in lung cancers. A total of 38 thymoma samples were directly sequenced for the EGFR gene. Protein expressions were evaluated for 56 thymic epithelial tumors by immunohistochemistry.


RESULTS
EGFR gene mutations were not detected in any of the thymoma and thymic cancer samples using TaqMan PCR assay. Of the 38 samples 3 showed a heterozygous silent mutation without changes in the protein, a G to A transition at the nucleotide 2361 in exon 18. EGFR expression was significantly higher in invasive thymomas (stages III-IV, 15/19 were positive) than in early stage thymomas (stages I-II, 7/33 were positive) (P < 0.0001). All four carcinomas and all seven B3 thymomas showed EGFR positive staining.


CONCLUSIONS
Although EGFR mutation at the tyrosine kinase domain is unlikely to be a therapeutic target for thymoma, the information about EGFR expression would contribute to the further identification of the therapeutic target for advanced thymomas.
Suzuki
Eriko
E
Department of Surgery II, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan.
Sasaki
Hidefumi
H
Kawano
Osamu
O
Endo
Katsuhiko
K
Haneda
Hiroshi
H
Yukiue
Haruhiro
H
Kobayashi
Yoshihiro
Y
Yano
Motoki
M
Fujii
Yoshitaka
Y
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D009367:Neoplasm Staging; D016133:Polymerase Chain Reaction; D013945:Thymoma / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D013953:Thymus Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology
D066246:ErbB Receptors