Objective: To investigate the status of c-kit and PDGFRA mutations of GIST in a the large sample of Chinese patients.
Method: One hundred and sixty-five cases were evaluated for the presence of c-kit and PDGFRA mutations. Exon 9, 11, 13, 17 of c-kit and exon 12, 18 of PDGFRA were analyzed by PCR amplification and direct sequencing.
Results: Immunohistochemical demonstrations of KIT (CD117) were seen in 94% of the cases (155/165). Overall, c-kit mutations were identified in 76.1% (118/155) of CD117 positive cases: 67.1% (104/155) involving exon 11, 7.1% (11/155) involving exon 9, 1.3% (2/155) involving exon 13 and 0.6% (1/155) involving exon 17. The c-kit exon 11 mutations were mostly heterogeneous and clustered in the classic "hot spot" at the 5' end of the exon, including in-frame deletion and point mutation. The second "hot spots" were internal tandem duplications (ITD) at the 3' end of the exon, which were associated with female patient, older age, stomach location and low mitotic counts. The exon 9 mutations correlated with a distinct subset of GISTs involving the small bowel of young male patients. A new point mutation of L641P was identified in exon 13. PDGFRA mutations were present in 50% (5/10) of CD117-negative GISTs, all involving exon 18 with the majority of mutations being D842V. One novel in-frame deletion of IMHD mutation at codon 843 - 846 with S847T was identified. GISTs with PDGFRA mutations were often larger tumors arising from the omentum/mesentery of young male patients with high risk of aggressive behavior.
Conclusions: The vast majority of GISTs in this study harbored c-kit and PDGFRA mutations, there were non-random relations between the gene mutation patterns and the locations of GISTs. It appears that Chinese GIST patients have some unique mutation patterns. It is necessary to evaluate the gene mutations status of GISTs to guide target therapy.