Insulin-like growth factor 1 receptor expression in wild-type GISTs: a potential novel therapeutic target

Aberrations of the Insulin-like Growth Factor (IGF) system have been found in association with a variety of cancer types. The potential role of IGF1R has been postulated in a small subset of GISTs, but until now the implications of its aberrations have not been defined. The aim of the study was to examine the IGF1R status in patients with gastric GIST in regard to KIT and PDGFRA genotype. Fresh resection specimens were collected from 8 primary tumours [2 wild-type (WT) and 6 mutant cases]. IGF1R was studied as gene expression profiling with Affymetrix GeneChip HG-U133Plus 2.0 arrays and as genomic copy number with SNP array analysis Affymetrix Genome Wide Human SNP 6.0 arrays, and at protein level with western blotting (WB) and immunohistochemistry (IHC). The unsupervised analysis of gene expression profiling of our patients merged with a data set from gastric GISTs identified 2 patients out of 8 with different expression of IGF1R. The data were confirmed by WB and IHC. In particular, IGF1R was upregulated in 2 young patients (<30-years old), who had both WT disease and metastases at diagnosis. The SNP array analysis showed that none of the tumours had IGF1R amplification. GISTs are characterized by abnormalities of the KIT and PDGFRA receptors that affect prognosis and response to tyrosine kinase inhibitors. Both young adult with WT GIST had the over-expression of IGF1R at mRNA and protein level. These results further confirm the hypothesis that IGF1R may be a potential therapeutic target in GISTs lacking KIT and PDGFRA mutations.