Reference Detail

Ref Type Journal Article
PMID (25003536)
Authors Rapisuwon S, Parks K, Al-Refaie W, Atkins MB
Title Novel somatic KIT exon 8 mutation with dramatic response to imatinib in a patient with mucosal melanoma: a case report.
Journal Melanoma research
Vol 24
Issue 5
Date 2014 Oct
URL
Abstract Text Primary mucosal melanomas represent ∼1.3% of all cases of melanoma diagnosed in the USA. The sinonasal location is the most common primary site. Mutations in the KIT gene occur in 10-22% of mucosal melanomas. Tumor response to imatinib mesylate has been reported in about half of the patients with tumors harboring KIT mutations. Responses are almost exclusively restricted to tumors with mutations in KIT exon 9 or 11. We report a case of a patient with a sinonasal mucosal melanoma with a novel exon 8 mutation (C443S) who had marked initial response to imatinib. Somatic exon 8 KIT mutations have not been previously reported in mucosal melanoma or in other human solid tumors; however, such mutations have been reported in canine and feline mast cell tumors. Protein transcripts from exon 8 play an important role in the structural and functional integrity of the extracellular domain of KIT. In preclinical studies, a mutation in exon 8 led to autophosphorylation, independent of KIT ligand, and constitutive activation of the tyrosine kinase. This biology may explain the successful application of imatinib in animals with tumors harboring exon 8 KIT mutations and in our patient with mucosal melanoma. This report expands the population of patients with melanoma who might benefit from imatinib to those with somatic exon 8 KIT mutations. Such mutations should be looked for in patients with mucosal melanoma.

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Molecular Profile Treatment Approach
Gene Name Source Synonyms Protein Domains Gene Description Gene Role
Therapy Name Drugs Efficacy Evidence Clinical Trials
Drug Name Trade Name Synonyms Drug Classes Drug Description
Variant Impact Protein Effect Variant Description Associated with drug Resistance
C443S missense unknown KIT C443S lies within the Ig-like C2-type domain 5 of the Kit protein (UniProt.org). C443S has been identified in the scientific literature (PMID: 25003536), but has not been biochemically characterized and therefore, its effect on Kit protein function is unknown (PubMed, Mar 2019).
Molecular Profile Indication/Tumor Type Response Type Therapy Name Approval Status Evidence Type Efficacy Evidence References
KIT C443S mucosal melanoma sensitive Imatinib Case Reports/Case Series Actionable In a clinical case study, a patient with mucosal melanoma harboring KIT C443S demonstrated a substantial response to Gleevec (imatinib) in the first two weeks and then developed progression at 15 weeks (PMID: 25003536). 25003536