Analysis of KIT Mutations in Sporadic and Familial Gastrointestinal Stromal Tumors: Therapeutic Implications through Protein Modeling

Abstract

Purpose: Gastrointestinal stromal tumors (GIST) are characterized by expressing a gainof-function mutation in KIT, and to a lesser extent, PDGFR. Imatinib mesylate, a tyrosine kinase inhibitor, has activity against GISTs that contain oncogenic mutations of KIT. In this study, KIT and PDGFRa mutation status was analyzed and protein modeling approaches were used to assess the potential effect of KIT mutations in response to imatinib therapy. Experimental Design: Genomic DNA was isolated from GIST tumors. Exons 9, 11, 13, and 17 of c-KIT and exons 12, 14, and 18 of PDGFRa were evaluated for oncogenic mutations. Protein modeling was used to assess mutations within the juxtamembrane region and the kinase domain of KIT. Results: Mutations in KITexons 9,11, and 13 were identified in GISTs with the majority of changes involving the juxtamembrane region of KIT. Molecular modeling indicates that mutations in this region result in disruption of the KITautoinhibited conformation, and lead to gain-of-function activation of the kinase. Furthermore, a novel germ-line mutation in KIT was identified that is associated with an autosomal dominant predisposition to the development of GIST. Conclusions: We have used protein modeling and structural analyses to elucidate why patients with GIST tumors containing exon11mutations are the most responsive to imatinib mesylate treatment. Importantly, mutations detected in this exon and others displayed constitutive activation of KIT. Furthermore, we have found tumors that are both KITand PDGFRa mutation negative, suggesting that additional, yet unidentified, abnormalities may contribute to GIST tumorigenesis.

KIT kinase mutants show unique mechanisms of drug resistance to imatinib and sunitinib in gastrointestinal stromal tumor patients

“…The primary JM KIT mutation in GIST patients has been proposed to negatively impact the inhibitory conformation of the JM domain (16), an effect also observed for the A-loop mutant D816H in our studies. Because sunitinib and imatinib efficacies 5.…”

Characterization of novel germline c-kit gene mutation, KIT-Tyr553Cys, observed in a family with multiple gastrointestinal stromal tumors

“…30,31,33,34,[36][37][38][39][40]43,44,46,49 KIT-Val559Ala mutation is the most frequent type, which has been detected in five families. 33,34,38,39,49 Recently, we found a germline mutation at exon 11, KIT-Tyr553Cys, in a 68-yearold woman with multiple GISTs.…”

“…As described above, various types of exon 11 germline c-kit gene mutations have been reported, 30,31,33,34,[36][37][38][39][40]43,44,46,49 but KIT-Tyr553Cys mutation has not been reported yet. Even in somatic c-kit gene mutation in sporadic GISTs, substitution of amino acid at codon 553 appears to be very rare.…”

“…30 To our knowledge, B20 families with germline c-kit gene mutations and multiple GISTs have been reported so far. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] Thirteen families including the first case have the c-kit gene mutation at exon 11, 30,31,33,34,[36][37][38][39][40]43,44,46,49 three families at exon 13, 32,45,48 three families at exon 17 35,42,47 and one family at exon 8. 41 In addition to multiple GISTs, patients of these families have hyperplasia of ICCs in the gut wall.…”

Adjuvant treatment of patients with gastrointestinal stromal tumors: stratification of patients into risk group

“…Ряд авторов связывает данный тип мутаций с высокой степенью злокачественности опу-холи [35,36]. Другие считают, что мутации в 11 экзоне KIT часто встречаются в доброка-чественных ГИСО [37].…”