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|Ref Type||Journal Article|
|Authors||Tamborini E, Bonadiman L, Greco A, Albertini V, Negri T, Gronchi A, Bertulli R, Colecchia M, Casali PG, Pierotti MA, Pilotti S|
|Title||A new mutation in the KIT ATP pocket causes acquired resistance to imatinib in a gastrointestinal stromal tumor patient.|
|Abstract Text||Imatinib, a tyrosine kinase inhibitor of BCR-ABL, KIT, and platelet-derived growth factor receptor, is used in patients with chronic myelogenous leukemia (CML) and gastrointestinal stromal tumors (GIST). Primary and acquired resistance to the drug can occur in both diseases. Molecular mechanisms have been reported in CML and GIST for primary resistance, whereas extensive studies on the mechanisms responsible for secondary resistance have been almost exclusively reported for CML.In a patient with advanced GIST undergoing imatinib therapy, an isolated progressing peritoneal mass was excised, along with 2 still-responding lesions. Complementary DNA and genomic DNA were analyzed by sequencing for c-Kit gene mutations. KIT receptor expression and phosphorylation status were assessed by immunoprecipitation and Western blot. Transient-transfection experiments were performed with mutagenized KIT constructs, and their activation status was assessed.In addition to an exon 11 mutation, shared among all of the analyzed lesions, a novel point mutation in c-Kit exon 14 resulting in T670I substitution was found only in the progressing lesion, which harbored a phosphorylated receptor, as opposed to the finding of an inactive receptor in responding lesions. Functional analyses showed that KIT/T670I is insensitive to imatinib and that T670I mutation, introduced in a receptor responding to imatinib, subverted its sensitivity to the drug.This new mutation was confined to the progressing lesion; the resulting amino acidic substitution, T670I, affecting the ATP/imatinib pocket of KIT, makes it insensitive to the drug. Interestingly, this substitution is a homologue to the T315I mutation already reported in CML, where it is responsible for acquired resistance to imatinib.|
|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|
|Gene||Variant||Impact||Protein Effect||Variant Description||Associated with drug Resistance|
|KIT||T670I||missense||gain of function||KIT T670I lies within the ATP pocket in the protein kinase domain of the Kit protein (PMID: 15236194, PMID: 22355224). T670I confers a gain of function on Kit as indicated by constitutive Kit phosphorylation, is transforming in cultured cells, and is associated with resistance to Kit inhibitors (PMID: 17699867, PMID: 15236194).||Y|
|KIT||V560del||deletion||gain of function||KIT V560del (also reported as V559del) results in the deletion of an amino acid in the juxtamembrane domain (exon 11) of the Kit protein at amino acid 560 (PMID: 12879016). V560del confers a gain of function to Kit, resulting in constitutive, ligand independent phosphorylation of Kit and activation of Akt in cell culture (PMID: 15236194, PMID: 22282465), and transformation of cultured cells (PMID: 19861435).|
|Molecular Profile||Indication/Tumor Type||Response Type||Therapy Name||Approval Status||Evidence Type||Efficacy Evidence||References|
|KIT T670I||gastrointestinal stromal tumor||predicted - resistant||Imatinib||Case Reports/Case Series||Actionable||In a clinical case report, a patient with a gastrointestinal stromal tumor developed disease progression while being treated with Gleevec (imatinib), demonstrating a KIT T670I mutation in the progressive lesion (PMID: 15236194).||15236194|