Gastroenterology

Gastroenterology

Volume 125, Issue 3, September 2003, Pages 660-667
Gastroenterology

Rapid communication
Gain-of-function mutations of platelet-derived growth factor receptor α gene in gastrointestinal stromal tumors

https://doi.org/10.1016/S0016-5085(03)01046-1Get rights and content

Abstract

Background & Aims: 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) α, we examined whether GISTs without KIT mutations had a mutation of PDGFR α. Methods: Whole coding region of PDGFR α complementary DNA (cDNA) was sequenced in GISTs with or without KIT mutations. Mutant PDGFR α cDNA was transfected into 293T human embryonic kidney cells, and autophosphorylation of PDGFR α was examined. Proliferation of Ba/F3 murine lymphoid cells stably transfected with mutant PDGFR α cDNA was estimated by tritium thymidine incorporation. Wild-type KIT cDNA was cotransfected with mutant PDGFR α cDNA, and immunoprecipitation by anti-KIT antibody was performed. Inhibitory effect of Imatinib mesylate on activated PDGFR α was examined. Results: We found 2 types of constitutively activated mutations of PDGFR α, 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 α bound and activated the cotransfected wild-type KIT. The constitutive activation of PDGFR α with Val-561 to Asp was inhibited effectively by Imatinib mesylate but that of PDGFR α with Asp-842 to Val was inhibited only weakly, even at the concentration of 10 μmol/L. Conclusions: The gain-of-function mutations of PDGFR α appear to play an important role in development of GISTs without KIT mutations.

Section snippets

Patients and tissue specimens

We collected 70 fresh samples of GIST tissues during surgical procedures at Osaka University Medical School and its affiliated hospitals. Paraffin sections (3 μm thick) of the formalin-fixed tissues were cut and used for H&E staining and immunohistochemistry. Mesenchymal tumors were identified to be GISTs when they were positive for KIT and/or CD34 by immunohistochemistry.1, 2 Genomic DNA was extracted from paraffin sections (10 μm thick), and used for the sequencing of exon 9 of PDGFR α DNA.

Identification of KIT mutations in GISTs and expression of PDGFR α in GISTs

The whole coding region of KIT cDNA was sequenced in 70 GISTs. Deletion, insertion, and/or point mutation were found at the juxtamembrane domain in 58 GISTs, and duplication of 2 amino acids (codons 501-Ala and 502-Tyr) were found at the extracellular domain in 4 GISTs. No KIT mutations were found in the remaining 8 GISTs.

By Northern blotting, PDGFR α transcripts were detected in most GISTs, and there was a tendency for the expression levels to be stronger in GISTs without KIT mutations than in

Discussion

We found gain-of-function mutations of PDGFR α gene in 5 of 8 GISTs without KIT mutations. No such PDGFR α mutations were found in GISTs with KIT mutations. All GISTs with the gain-of-function mutations of PDGFR α gene primarily developed in the stomach. One GIST patient with 561-Val to Asp PDGFR α mutation died of cancerous peritoneal dissemination 6 years after the primary surgery. The other GIST patient with 561-Val to Asp PDGFR α mutation had local recurrence, but the lesion appeared to be

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  • Cited by (0)

    Supported by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

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