Novel BRAF mutation in melanoma: A case report

Abstract

Abstract. In melanoma, a number of specific genetic and genomic aberrations have been identified to be important in tumorigenesis. In particular, the mutant B-Raf proto-oncogene, Serine/Threonine kinase (BRAF) gene is the target of tailored therapy with kinase inhibitor molecules. Identification of the array of mutations in patients with melanoma will be useful in determining a genetic profile of the tumor with potential implications for treatment decisions. A rare aminoacidic insertion in codon 599 of the BRAF gene (c.1797_1798insACA, T599insT) was detected by using both direct (Sanger) sequencing and pyrosequencing techniques in a metastatic melanoma of a female elderly patient. As suggested in other clinical contexts including pilocytic astrocytoma, papillary thyroid carcinomas and anaplastic thyroid carcinomas, this unusual mutation may be associated with a modified spatial structure of activated P-loop, resulting in a constitutional activation of the BRAF protein. The patient died shortly following the test, thus no biological therapy was performed. Comparable data regarding treatment of melanoma patients with rare BRAF mutations is lacking, and the response to BRAF inhibitors requires further investigation. IntroductionMutations of BRAF oncogene are common in cutaneous melanomas, being found in as much as 50% of the total number of cases. Most mutations involve exon 15, exon 11 being interested in less than 1% of cases (1). V600E in exon 15 is by far the most common (2). This mutation modifies the spatial structure of activation P-loop, causing a 500-fold increase in BRAF kinase activity and facilitating the acquisition of secondary genetic events in cancer progression (3). Target therapy for cutaneous melanomas is focused on this mutation: small molecules (vemurafenib and dabrafenib) act as Tyrosine Kinase Inhibitors (TKIs), and interrupt the BRAF/MEK step in RAS/MEK/ERK pathway, inducing apoptosis in mutated cells (4). Less frequent BRAF mutations (5,6) with alterations in the same crucial site, such as Threonine599 and Serine601 (7), have been described. Herein, we report a single case of primary cutaneous melanoma showing a mutation occurring in the P-loop activating site (c.1797_1798insACA, T599insT), which was not previously described in melanomas, but only rarely found in Pilocytic Astrocytoma (PA), Papillary Thyroid Carcinoma (PTC) and Anaplastic Thyroid Carcinoma (ATC) (8-11). In silico and in vitro data indicate that rare and/or complex mutations in codons 599-601 increase kinase activity similarly to the typical V600E (8,9,12,13). Case reportΑ 88-year-old female was presented with large, ulcerated superficial spreading melanoma on the left cheek, including a nodular polypoid component, widely ulcerated, with regression arising from a radial growth phase pigmented macula. Histologic examination showed a T4 lesion, Clark level V, with invasion into the subcutaneous fat (Fig. 1A). Angiolymphatic and perineural invasion were also described and a mitotic rate of 20/mm 2 was detected. Melanoma cells w...

<b><i>BRAF</i></b> V600 Mutational Status in Melanoma Correlates with Cytologic Features in Fine-Needle Aspirate Specimens

“…Approximately 30-72% of melanomas have been associated with a BRAF mutation in the V600 codon [4,5]. Most BRAF mutations occur as a missense mutation of a valine replaced by a glutamic acid at codon V600E in exon 15, which lies within the activation segment of the kinase domain disrupting the auto-inhibitory mechanism, resulting in the constitutive activation of the MAPK pathway and facilitating the acquisition of secondary genetic events in tumorigenesis [6,7].…”

A rare BRAF T599dup mutation conferring sensitivity to BRAF inhibitor in a patient with metastatic melanoma

“…The mutation consists of a heterozygous in‐frame three‐base‐pair insertion at position 1796 (c.1796_1797insCAC), resulting in the insertion of an additional threonine residue at amino‐acid position 599 (p.T599_V600insT), equivalent to the mutation described in the COSMIC database . This mutation was previously found in some cases of thyroid carcinoma and in one patient with metastatic melanoma who died before BRAFi treatment could be started . In silico and in vitro data indicate that rare and/or complex mutations in codons 599–601 increase kinase activity similar to the typical V600E mutation .…”

“…4 This mutation was previously found in some cases of thyroid carcinoma and in one patient with metastatic melanoma who died before BRAFi treatment could be started. 5 In silico and in vitro data indicate that rare and/or complex mutations in codons 599-601 increase kinase activity similar to the typical V600E mutation. 5 In our case, partial remission occurred within 6 weeks, which suggests that combined treatment with BRAFi and MEKi is a valuable treatment option.…”

Cutaneous Melanoma—A Long Road from Experimental Models to Clinical Outcome: A Review

“…This mutation was reported in melanomas and melanocytic nevi, leading to activation of RAS/RAF/MEK/ERK pathway, a key player in the initiation of melanocytic tumors [ 7 , 8 ]. A novel BRAF mutation (an aminoacidic insertion in codon 599) was identified in a melanoma patient in the P-loop activating site, mutation that was not discovered before in melanoma, but was detected rarely in Papillary Thyroid Carcinoma and Anaplastic Thyroid Carcinoma, which highlights the heterogeneity of this disease [ 54 ].…”

“…In addition, regulates negatively RAS family leading to RAF inhibitor resistance. To note, NF1 mutations or suppression might appear in parallel to BRAF mutations [ 51 , 52 , 53 , 54 ].…”