Gain-of-function mutations of platelet-derived growth factor receptor alpha gene in gastrointestinal stromal tumors.
OBJECTIVE
Most gastrointestinal stromal tumors (GISTs) have gain-of-function mutations of c-kit receptor tyrosine kinase (KIT) gene, but some GISTs do not. We investigated the cause of GISTs without KIT mutations. Because GISTs apparently expressed platelet-derived growth factor receptor (PDGFR) alpha, we examined whether GISTs without KIT mutations had a mutation of PDGFR alpha.


METHODS
Whole coding region of PDGFR alpha complementary DNA (cDNA) was sequenced in GISTs with or without KIT mutations. Mutant PDGFR alpha cDNA was transfected into 293T human embryonic kidney cells, and autophosphorylation of PDGFR alpha was examined. Proliferation of Ba/F3 murine lymphoid cells stably transfected with mutant PDGFR alpha cDNA was estimated by tritium thymidine incorporation. Wild-type KIT cDNA was cotransfected with mutant PDGFR alpha cDNA, and immunoprecipitation by anti-KIT antibody was performed. Inhibitory effect of Imatinib mesylate on activated PDGFR alpha was examined.


RESULTS
We found 2 types of constitutively activated mutations of PDGFR alpha, Val-561 to Asp or Asp-842 to Val, in 5 of 8 GISTs without KIT mutations but not in 10 GISTs with KIT mutations. Stable transfection of each mutation induced autonomous proliferation of Ba/F3 cells. Constitutively activated mutant PDGFR alpha bound and activated the cotransfected wild-type KIT. The constitutive activation of PDGFR alpha with Val-561 to Asp was inhibited effectively by Imatinib mesylate but that of PDGFR alpha with Asp-842 to Val was inhibited only weakly, even at the concentration of 10 micromol/L.


CONCLUSIONS
The gain-of-function mutations of PDGFR alpha appear to play an important role in development of GISTs without KIT mutations.
Hirota
Seiichi
S
Department of Pathology, Osaka University Medical School, Suita, Japan. hiros@patho.med.osaka-u.ac.jp
Ohashi
Akiko
A
Nishida
Toshirou
T
Isozaki
Koji
K
Kinoshita
Kazuo
K
Shinomura
Yasuhisa
Y
Kitamura
Yukihiko
Y
D019943:Amino Acid Substitution; D001549:Benzamides; D005770:Gastrointestinal Neoplasms / Q000235:genetics*; D006801:Humans; D000068877:Imatinib Mesylate; D009154:Mutation; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics*
D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha