Kinase mutations and imatinib response in patients with metastatic gastrointestinal stromal tumor.
OBJECTIVE
Most gastrointestinal stromal tumors (GISTs) express constitutively activated mutant isoforms of KIT or kinase platelet-derived growth factor receptor alpha (PDGFRA) that are potential therapeutic targets for imatinib mesylate. The relationship between mutations in these kinases and clinical response to imatinib was examined in a group of patients with advanced GIST.


METHODS
GISTs from 127 patients enrolled onto a phase II clinical study of imatinib were examined for mutations of KIT or PDGFRA. Mutation types were correlated with clinical outcome.


RESULTS
Activating mutations of KIT or PDGFRA were found in 112 (88.2%) and six (4.7%) GISTs, respectively. Most KIT mutations involved exon 9 (n = 23) or exon 11 (n = 85). All KIT mutant isoforms, but only a subset of PDGFRA mutant isoforms, were sensitive to imatinib, in vitro. In patients with GISTs harboring exon 11 KIT mutations, the partial response rate (PR) was 83.5%, whereas patients with tumors containing an exon 9 KIT mutation or no detectable mutation of KIT or PDGFRA had PR rates of 47.8% (P =.0006) and 0.0% (P <.0001), respectively. Patients whose tumors contained exon 11 KIT mutations had a longer event-free and overall survival than those whose tumors expressed either exon 9 KIT mutations or had no detectable kinase mutation.


CONCLUSIONS
Activating mutations of KIT or PDGFRA are found in the vast majority of GISTs, and the mutational status of these oncoproteins is predictive of clinical response to imatinib. PDGFRA mutations can explain response and sensitivity to imatinib in some GISTs lacking KIT mutations.
Heinrich
Michael C
MC
R&D-19 3710 SW US Veterans Hospital Rd, Portland, OR 97207, USA. heinrich@ohsu.edu
Corless
Christopher L
CL
Demetri
George D
GD
Blanke
Charles D
CD
von Mehren
Margaret
M
Joensuu
Heikki
H
McGreevey
Laura S
LS
Chen
Chang-Jie
CJ
Van den Abbeele
Annick D
AD
Druker
Brian J
BJ
Kiese
Beate
B
Eisenberg
Burton
B
Roberts
Peter J
PJ
Singer
Samuel
S
Fletcher
Christopher D M
CD
Silberman
Sandra
S
Dimitrijevic
Sasa
S
Fletcher
Jonathan A
JA
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides; D016466:CHO Cells; D006224:Cricetinae; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D019008:Drug Resistance, Neoplasm; D005091:Exons; D005770:Gastrointestinal Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000556:secondary; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000068877:Imatinib Mesylate; D007124:Immunoenzyme Techniques; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010766:Phosphorylation; D010879:Piperazines / Q000627:therapeutic use*; D011379:Prognosis; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000627:therapeutic use*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics* / Q000378:metabolism; D017154:Stromal Cells / Q000473:pathology; D015996:Survival Rate; D014162:Transfection
D000970:Antineoplastic Agents; D001549:Benzamides; D004273:DNA, Neoplasm; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha