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Primary and Metastatic Cutaneous Melanomas Express ALK Through Alternative Transcriptional Initiation.

原发性或转移性皮肤黑色素瘤通过替代转录启动途径表达ALK

Busam KJ,Vilain RE,Lum T,Busam JA,Hollmann TJ,Saw RP,Coit DC,Scolyer RA,Wiesner T

Abstract

A number of common driver mutations have been identified in melanoma, but other genetic or epigenetic aberrations are also likely to play a role in the pathogenesis of melanoma and present potential therapeutic targets. Translocations of the anaplastic lymphoma kinase (ALK), for example, have been reported in spitzoid melanocytic neoplasms leading to kinase-fusion proteins that result in immunohistochemically detectable ALK expression. In this study, we sought to determine whether ALK was also expressed in nonspitzoid primary and metastatic cutaneous melanomas. ALK immunohistochemistry was performed on 603 melanomas (303 primary and 300 metastatic tumors) from 600 patients. ALK immunohistochemistry expression was identified in 7 primary and 9 metastatic tumors. In 5 of 7 primary tumors and in 6 of 9 metastatic lesions, the majority of tumor cells were immunoreactive for ALK. In the other 2 primary and 3 metastatic lesions, positive staining was identified in less than half of the tumor cells. ALK positivity was found in the presence or absence of BRAF or NRAS mutations. In contrast to prior observations with ALK-positive Spitz tumors, none of the ALK-positive melanomas harbored a translocation. Instead, the ALK-positive melanomas predominantly expressed the recently described ALK isoform, ALK, which lacks the extracellular and transmembrane domains of wild-type ALK, consists primarily of the intracellular tyrosine kinase domain, and originates from an alternative transcriptional initiation site within the ALK gene. The findings are clinically relevant as patients with metastatic melanoma who have ALK expression may potentially benefit from treatment with ALK kinase inhibitors.

摘要

已证实黑色素瘤中有大量常见的驱动突变,但是其他遗传学或表观遗传学畸变也有可能在黑色素瘤的致病过程中发挥着重要作用,并有望成为潜在的治疗靶点。例如,曾有报道发现Spitzoid黑色素瘤中间变性淋巴瘤激酶(ALK)的异位产生激酶融合蛋白,从而导致免疫组织化学方法可检测到ALK。

本研究中,我们试图确定原发性或转移性皮肤非Spitzoid黑色素瘤中ALK是否也有表达。

本研究利用免疫组织化学方法对来自600个患者的603份黑色素瘤标本(303份为原发性,300份为转移性)进行ALK检测。7份原发性和9份转移性标本中检测到ALK的表达。5/7份原发性癌标本和6/9份转移性肿瘤标本中,大部分肿瘤细胞呈ALK阳性,其余的2份原发性标本和3份转移性标本中,ALK阳性的肿瘤细胞不足一半。BRAF和NRAS基因突变与否均可见ALK阳性。与先前ALK阳性Spitz肿瘤中的发现不同的是,ALK阳性的非Spitz黑色瘤中无一发生ALK易位。相反,ALK阳性的黑色素瘤主要表达最近报导的ALK的同工型,即缺乏野生型ALK的细胞外结构域和跨膜结构域,而主要由胞内的酪氨酸激酶结构域组成,源自ALK基因内的另一种转录启动途径。

这些结果具有重要临床意义,当患者为ALK阳性的转移性黑色素瘤时,有望自ALK激酶抑制剂治疗获益。

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