BRAF mutations exist in numerous types of
cancer, including
melanomas,
colorectal cancers and
lung cancers. The V600E-specific inhibitor
vemurafenib has marked clinical activity in patients with BRAF V600E-mutated
melanoma. However, there are many cases of resistance to
vemurafenib. This may be due to the reported intra-
tumor heterogeneity of the BRAF V600E mutation in primary
melanomas. BRAF mutations are found in 1-5% of non-
small cell carcinomas (NSCLCs), almost exclusively in
adenocarcinoma. A few cases have been reported in which
vemurafenib was effective against BRAF V600E-mutated
lung cancers. In a previous study, five
lung adenocarcinomas with BRAF V600E mutation were detected by direct sequencing. The present study analyzed these
tumors for the percentage of mutation (%mutation) by competitive allele-specific polymerase chain reaction (CAST-PCR) assay. In addition, sections of all components of the
adenocarcinomas were obtained by
laser microdissection and analyzed. The %mutations of BRAF V600E within the macrodissected
tumors (cases 1-5) were: Case 1, 10.0%; case 2, 8.0%; case 3, 8.9%; case 4, 21.5%; and case 5, 14.9%. In four cases (cases 2-5), the %mutations of each
adenocarcinoma component were as follows: Case 2, lepidic growth 6.5-24.5%, papillary 1.3-11.2% and acinar 9.8%; case 3, solid 2.5-69.9%, acinar 12.4-27.1% and papillary 3.7-17.4%; case 4, acinar 10.0-45.0% and papillary 44.0%; and case 5, papillary 3.7-93.4%. Sensitive BRAF mutation detection methods were used and evidence for heterogeneity of the BRAF V600E mutation in these
lung adenocarcinoma cases was observed. Targeted
therapy with a BRAF V600E inhibitor such as
vemurafenib may have potential in the treatment of
lung cancer with this mutation; however, it is necessary to consider how the treatment effect of and drug resistance to BRAF V600E inhibitors are affected by the presence of heterogeneity in future studies.