BRAF^V600E mutation: A promising target in colorectal neuroendocrine carcinoma

Abstract

To determine the role of BRAF mutation and MAPK signaling as well as the effects of BRAF and MEK directed therapy in gastroenteropancreatic neuroendocrine neoplasia (GEP-NEN), with a focus on highly aggressive gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC). Using Sanger sequencing of BRAF exon 15 we determined the frequency of BRAF mutations in 71 primary GEP-NENs. MEK phosphorylation was examined by immunohistochemistry in corresponding tissue samples. To evaluate the biological relevance of BRAF mutation and MAPK signaling in GEP-NECs, effects of a pharmacological BRAF and MEK inhibition were analyzed in NEC cell lines both in vitro and in vivo. BRAF mutation was detected in 9.9% of all GEP-NENs. Interestingly, only NECs of the colon harbored BRAF mutations, leading to a mutation frequency of 46.7% in this subgroup of patients. In addition, a BRAF mutation was significantly associated with high levels of MEK phosphorylation (pMEK) and advanced tumor stages. Pharmacological inhibition of BRAF and MEK abrogated NEC cell growth, inducing G1 cell cycle arrest and apoptosis only in BRAF mutated cells. BRAF inhibitor dabrafenib and MEK inhibitor trametinib prevented growth of BRAF positive NEC xenografts. High frequencies of BRAF mutation and elevated expression levels of pMEK were detected in biologically aggressive and highly proliferative colorectal NECs. We provide evidence that targeting BRAF oncogene may represent a therapeutic strategy for patients with BRAF mutant colorectal NECs.

Gastroenteropancreatic High-Grade Neuroendocrine Neoplasms: Histology and Molecular Analysis, Two Sides of the Same Coin

“…We can speculate that EGFR monoclonal antibody-based regimens could be taken into account for pan RAS WT NEC patients. Again, moving to a tailored treatment, NEC ≥55% BRAF mutated patients may benefit from BRAF-MEK combination therapy as previously described [41,42]. Frequent RAS mutations have also been described in pancreatic NECs [40], but large-scale studies are lacking due to the rarity of the condition.…”

Mps1 is associated with the BRAFV600E mutation and predicts poor outcome in patients with colorectal cancer

“…The 1796T>A mutation results in an amino acid substitution at position 600 in BRAF, from valine to glutamic acid. This mutation occurs within the activation segment of the kinase domain and leads to the continuous activation of the MAPK/ERK signaling pathway (7,8). Although oral BRAF inhibitors have remarkable clinical activity in metastatic melanomas with BRAF V600E , resistance to therapy invariably develops in patients with CRC with the same BRAF mutation (9,10).…”

Preliminary Study on the Identification of BRAFV600E Mutation in Colorectal Cancer by Near-Infrared Spectroscopy

“…48,49 Currently, Sanger sequencing, RT-PCR, NGS, and immunohistochemical methods are mainly used to detect BRAF mutation. 19,21,22,26 Among these methods, the first three methods require high standard requirement of samples and complicated procedures for sampling, which limit their application as routine detection methods. 24 IHC is also affected by various factors such as specimen fixation time and fixative types.…”

“…2,16,17 Given the critical genetic, prognostic, and therapeutic significance of BRAF V600E , it is vital to ensure accurate identification of CRC patients with BRAF V600E mutations. 10,18 Currently, in diagnostics and laboratory research, there are many methods used for genotypic assessment of BRAF mutation, ranging from traditional Sanger sequencing 19 and next-generation sequencing (NGS) 20 to mutation-specific real-time polymerase chain reaction (RT-PCR) assays, 21,22 and also mass spectrometry-based methods. 23 However, for all these methods it is necessary to extract DNA from tissues.…”