60例胃肠道间质瘤（GISTs）中的c-kit和血小板衍生生长因子受体A（PDGFRA）突变

He Hui-ying, Xiang Yi-ning, Li Yan, Zhong Hao-hao, Wu Bing-quan, Zheng Jie

Department of Pathology, Peking University School of Basic Medical Scienes, Beijng 100083, China.

Beijing Da Xue Xue Bao Yi Xue Ban. 2005 Jun 18;37(3):320-4.

OBJECTIVE

To explore the status of activating mutations of c-kit and PDGFRA in GIST of Chinese patients.

METHODS

Sixty GISTs, confirmed by immunoreactivity of CD117, CD34, SMA, S-100 and Desmin, were evaluated for the presence of c-kit exons 9, 11, 13 and 17 mutations, and PDGFRA exons 12 and 18 mutations. The PCR products were sequenced directly for mutations, using DNA extracted from paraffin-embedded tissue.

RESULTS

53% of the tumors were located in the stomach, 22% in the small bowel, 8% in the colo rectum, 2% in the esophagus and 15% in the extragastrointestinal tract. Immunohistochemical demonstrations of c-kit (CD117) were seen in 90% cases. Overall, c-kit mutations were detected in 63.3% of patients as follows: 58.3% in exon 11, 3.3% in exon 9, 1.7% in exon 13 and none in exon 17. The types of c-kit exon 11 mutations were mostly heterogeneous and clustered in the classic "hot spot" at the 5' end of exon 11, 42.9% being point mutation and in-frame deletion at Codon 557-560. 14.3% of cases showed internal tandem duplications (ITD) at the 3' end of exon 11 in a region of a second hot spot for c-kit mutations. Interestingly, these cases were associated with female predominance, stomach location and occurrence in older patients. The present study failed to identify a significant association between c-kit mutation status and risk of aggressive behavior in GISTs. Exon 9 mutations consisted of ITP of six nucleotides encoding Ala-Tyr. A new point mutation of L641P was revealed in exon 13. PDGFRA mutations were found in 5% of all the 60 cases with none of the positive cases expressed detectable KIT protein. The type of mutation was the commonest point mutation of D842V of exon 18.

CONCLUSION

Most KIT expressing GIST show c-kit mutations that are preferentially located within the classic hot spot of exon 11. A second hot spot -ITD at the 3' end of exon 11 seems to associate with a subgroup of gastric GISTs in older females. c-kit exons 9, 13 and 17 mutations are rare events in GIST of China. PDGFRA oncogenic mutations are more likely seen in KIT-negative GISTs arising in the peritoneal surface and have an unfavorable clinical course.

目的

探讨中国患者胃肠道间质瘤（GIST）中c-kit和血小板衍生生长因子受体α（PDGFRA）激活突变的状况。

方法

选取60例经CD117、CD34、平滑肌肌动蛋白（SMA）、S-100和结蛋白免疫反应性确诊的GIST，评估c-kit基因外显子9、11、13和17的突变情况，以及PDGFRA基因外显子12和18的突变情况。使用从石蜡包埋组织中提取的DNA，直接对聚合酶链反应（PCR）产物进行测序以检测突变。

结果

53%的肿瘤位于胃，22%位于小肠，8%位于结直肠，2%位于食管，15%位于胃肠道外。90%的病例可见c-kit（CD117）免疫组化阳性。总体而言，63.3%的患者检测到c-kit突变，具体如下：外显子11突变占58.3%，外显子9突变占3.3%，外显子13突变占1.7%，外显子17未检测到突变。c-kit外显子11突变类型大多为异质性，聚集在外显子11 5'端的经典“热点”区域，42.9%为密码子557 - 560处的点突变和框内缺失。14.3%的病例在外显子11 3'端的第二个c-kit突变热点区域出现内部串联重复（ITD）。有趣的是，这些病例以女性居多，位于胃，且多见于老年患者。本研究未发现c-kit突变状态与GIST侵袭性行为风险之间存在显著关联。外显子9突变由编码丙氨酸-酪氨酸的六个核苷酸的插入/缺失（ITP）组成。外显子13发现了一个新的L641P点突变。60例患者中5%检测到PDGFRA突变，所有阳性病例均未检测到可检测的KIT蛋白表达。突变类型为外显子18最常见的D842V点突变。

结论

大多数表达KIT的GIST显示c-kit突变，这些突变优先位于外显子11的经典热点区域。外显子11 3'端的第二个热点——ITD似乎与老年女性胃GIST的一个亚组相关。c-kit外显子9、13和17突变在中国GIST中是罕见事件。PDGFRA致癌突变更可能见于腹膜表面发生的KIT阴性GIST，且临床病程不良。