The New Assay Exploration And Significance For Detection Of EGFR Gene Mutation In Non-small-cell Lung Cancer

[Objective] This study was designed to explore the new assay and significance for detection of EGFR gene mutation in non-small-cell lung cancer.[Method] The expression of EGFR and mutation EGFR proteins(del EGFR, L858R EGFR) in 140 tumor specimens of human non-small-cell lung cancer was detected by Envision immunohistochemial staining with mutation specific antibody. DNA was extracted by traditional phenol-chloroform and ethanol precipitation from the excised tumor specimens of 140 non-small-cell lung cancer patients. Exon 19 and 21 were amplified by polymerase chain reaction(PCR),followed by direct sequencing. We compared the results of the IHC and DNA sequencing.[Results] 1.The results of immunohistochemistry1.1 IHC with EGFR antibody stained 49 samples(35%) with the immunohistochemical(IHC) positive scores of EGFR were detected in 140 samples of NSCLC patients. Of 49 positive cases, 35 cases were AC samples, and 14 cases were SCC samples. The difference between the percentage positively stained of the AC group and SCC group was not significant(p>0.05).1.2 Del EGFR mutation-specific antibody IHC staining The 10 cases with IHC positive scores of Del EGFR were detected in 90 cases of AC group, none with positve scores was detected in SCC group. There were significant differences of the IHC positive score between AC and SCC group(p<0.05).1.3 L858R EGFR mutation-specific antibody IHC staining The 9 cases with IHC positive scores of L858R EGFR were detected in 90 cases of AC group, none with positve scores was detected in SCC group. There were significant differences of the IHC positive score between AC and SCC group(p<0.05).2. Exon 19 and 21 of EGFR mutation2.1 The result of DNA sequencing Exon 19 and 21 EGFR mutation were detected in 24 of 140 cases with non-small cell lung cancer tissues(17.14%).Among the 24 cases, 14 cases were detected with exon 19 of EGFR, which delE746-A750 with exon 19 were detected in 10 cases, and 4 cases were detected with rare mutation of exon 19.The others 10 cases were detected with L858R of exon 21.The 24 cases of EGFR mutation were detected in AC group, none with EGFR mutation was detected in SCC group. There were significant differences of exon 19 and 21 EGFR mutation between AC and SCC group(p<0.05).2.2 Comparison the results of IHC and DNA sequencing 19 cases with IHC positively scores of EGFR mutation-specific antibodies were detected respectively with exon 19 and 21 EGFR mutation.4 of 5 cases were detected with rare EGFR mutation of exon 19,and one case with IHC negatively score of L858R EGFR mutation-specific antibody was detected with exon 21 of EGFR mutation.3. The relation between the expression of IHC positively score with EGFR mutation-specific antibody and clinicopathologic characterIn 19 cases which were expressed positively of IHC with EGFR mutation-specific antibody, 5 cases were men and 14 cases were women,7 cases were smokers and 12 cases were non-smokers. 19 cases were all adenocarcinoma and none were squamous cell carcinoma. The expression positively with EGFR mutation-specific antibody were more frequently observed in women(14/72,19.4%) than in men(5/68,7.35%), in adenocarcinomas(19/90,21.11%) than squamous(0/50).There was no difference in expression positively rates between smokers and non-smokers.[Conclusion] 1. The expression of EGFR antibody was not associated with the histological types of lung carcinoma;2. The expression rates of IHC positively score in AC group with EGFR mutation-specific antibody was higher than that in SCC group, in female patients were higher than in male patients.3. Comparison the result of DNA sequencing, IHC with EGFR mutation-specific antibodies will be a more rapid, convenient, sensitive and specific methodology to provide significant evidence for targeted therapy of non-small-cell lung cancer patients.