Abstract
Perivascular epithelioid cell neoplasms (PEComa) are a family of rare mesenchymal tumors with hybrid myo-melanocytic differentiation. Although most PEComas harbor loss-of-function TSC1/TSC2 mutations, a small subset were reported to carry TFE3 gene rearrangements. As no comprehensive genomic study has addressed the molecular classification of PEComa, we sought to investigate by multiple methodologies the incidence and spectrum of genetic abnormalities and their potential genotype-phenotype correlations in a large group of 38 PEComas. The tumors were located in soft tissue (11 cases) and visceral sites (27) including uterus, kidney, liver, lung, and urinary bladder. Combined RNA sequencing and fluorescence in situ hybridization analysis identified 9 (23%) TFE3 gene-rearranged tumors, with 3 cases showing an SFPQ/PSF-TFE3 fusion and 1 case showing a novel DVL2-TFE3 gene fusion. The TFE3-positive lesions showed a distinctive nested/alveolar morphology and were equally distributed between soft tissue and visceral sites. In addition, novel RAD51B gene rearrangements were identified in 3 (8%) uterine PEComas, which showed a complex fusion pattern and were fused to RRAGB/OPHN1 genes in 2 cases. Other nonrecurrent gene fusions, HTR4-ST3GAL1 and RASSF1-PDZRN3, were identified in 2 cases. Targeted exome sequencing using the IMPACT assay was used to address whether the presence of gene fusions is mutually exclusive from TSC gene abnormalities. TSC2 mutations were identified in 80% of the TFE3 fusion-negative cases tested. Coexistent TP53 mutations were identified in 63% of the TSC2-mutated PEComas. Our results showed that TFE3-rearranged PEComas lacked coexisting TSC2 mutations, indicating alternative pathways of tumorigenesis. In summary, this comprehensive genetic analysis significantly expands our understanding of molecular alterations in PEComas and brings forth the genetic heterogeneity of these tumors.
摘要
血管周上皮样细胞肿瘤(PEComa)是一组混有肌-黑色素分化的少见间叶源性肿瘤。尽管大多数PEComa具有TSC1/TSC2功能丧失性突变,但据报道一小部分病例有TFE3基因重排。目前针对PEComa的分子分型尚无全面的基因组研究,我们运用多种方法调查分析了38例PEComas,试图研究它的遗传学异常发生率、谱系以及基因型和表型的潜在相关性。肿瘤位于软组织(11例)和内脏器官(27例),后者包括子宫、肾、肝、肺和膀胱。联合应用RNA测序分析和FISH检测证实9例(23%)有TFE3基因重排,3例显示SFPQ/PSF-TFE3基因融合,1例显示DVL2-TFE3基因融合。TFE3阳性的病变呈明显的巢状/腺泡状形态学表现,发生于软组织和内脏器官的例数相同。另外,3例子宫PEComas中发现新的RAD51B基因重排,显示复杂的基因融合模式,其中2例是与RRAGB/OPHN1融合。2例PEComas中发现其它基因融合:HTR4-ST3GAL1和RASSF1-PDZRN3。采用过去检测基因融合是否存在的IMPACT方法进行目标外显子组测序,检测结果与TSC基因异常相互排斥。TFE3融合阴性的病例有80%发现TSC2突变,TSC2突变的PEComas中63%有TP53突变并存。研究结果显示TFE3重排的PEComas缺乏TSC2突变并存,提示肿瘤发生机制中可能涉及到其它不同的替代通路。总之,全面的基因分析明显拓宽了我们对PEComas分子改变的理解,呈现出肿瘤的遗传异质性。
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