BRAF V600E Mutation of Non-Small Cell Lung Cancer in Korean Patients

Abstract

Background and Objectives: BRAF mutational status in resected non-small cell lung cancer (NSCLC) in the Korean population is poorly understood. We explored BRAF (particularly BRAF V600E) mutational status among Korean patients with NSCLC. Materials and Methods: This study included 378 patients with resected primary NSCLC who were enrolled from January 2015 to December 2017. The authors obtained formalin-fixed paraffin-embedded (FFPE) tissue blocks and performed peptide nucleic acid (PNA)-clamping polymerase chain reaction (PCR) for detecting BRAF V600, real-time PCR for detecting BRAF V600E, and immunohistochemical analyses using the mutation-specific Ventana VE1 monoclonal antibody. For positive cases in any methods mentioned above, direct Sanger sequencing was additionally performed. Results: The PNA-clamping method revealed the BRAF V600 mutation in 5 (1.3%) of the 378 patients. Among these five patients, real-time PCR, direct Sanger sequencing detected BRAF V600E mutations in three (0.8%) patients. Thus, two cases showed differences in their PNA-clamping and the others. Direct Sanger sequencing of PNA-clamping PCR product was performed for two cases showing negative results on direct Sanger sequencing; both contained BRAF mutations other than V600E. All patients harboring BRAF mutations had adenocarcinomas, and all patients with V600E mutation exhibited minor micropapillary components. Conclusions: Despite the low incidence of the BRAF mutation among Korean patients with NSCLC, lung adenocarcinoma patients with micropapillary components should be prioritized in terms of BRAF mutation testing. Immunohistochemical staining using Ventana VE1 antibody may serve as a screening examination for BRAF V600E.

Keywords: B-type Raf kinase (BRAF); Ventana VE1 antibody; immunohistochemistry; lung cancer.

Figure 1

Histologic feature and immunohistochemistry. (A–D). Patient 142; all ×200. (A) A Hematoxylin and eosin (H&E)-stained section showing acinar and micropapillary structures. (B) Immunohistochemistry for VE1 (staining intensity 3). (C) Immunohistochemistry for VE1 (staining intensity 2). (D) Immunohistochemistry for VE1 (staining intensity 1). (E,F) Patient number 270; all ×200. (E) An H&E-stained section showing solid and acinar growth patterns. (F) Negative immunostaining for VE1. (G,H) Patient number 324; all ×200. (G) An H&E-stained section showing an acinar growth pattern. (H) Negative immunostaining for VE1. (I,J) Patient number 348; all ×200. (I) An H&E-stained section showing an acinar pattern and a few micropapillary structures. (J) Immunohistochemistry for VE1 (staining intensity 3). (K,L) Patient number 358; all ×200. (K) An H&E-stained section showing an acinar pattern and a few micropapillary structures. (L) Immunohistochemistry for VE1 (staining intensity 2).

Figure 2

Results of direct Sanger sequencing. (A) Case number 142 carries the c.1799 T > A (p. V600E) mutation. (B) Case number 270 is wild-type for B-type Raf kinase (BRAF). (C) Case number 324 is wild-type for BRAF. (D) Case number 348 carries the c.1799 T > A (p. V600E) mutation. (E) Case number 358 carries the c.1799 T > A (p. V600E) mutation.

Figure 3

Direct sequencing of peptide nucleic acid (PNA) polymerase chain reaction (PCR) products reveals two p. V600E-negative cases. (A) Case number 270 carries the c.1798_1799 CA > TT (p. V600K) for B-type Raf kinase (BRAF) mutation. (B) Case number 324 carries the c.1800 C > T (p. V600V) and c.1801 T > C (p. K601E) BRAF mutations.