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【35under35】周严医生:SMARCA4缺失肺部肿瘤诊治进展

2022年07月31日
作者:周严 
医院:上海市胸科医院

   

               
周严
上海市胸科医院

上海市胸科医院/上海交通大学附属胸科医院 呼吸内科 主治医师 博士
国际肺癌研究协会(IASLC) 会员
中国临床肿瘤学会(CSCO) 会员
美国匹兹堡大学、美国堪萨斯大学访问学者
主持国自然青年基金1项 主持上海市青年英才扬帆计划1项和上海市“医苑新星”青年医师人才计划1项
主攻方向:肿瘤-神经-免疫交互分子机制
相关论文发表在Cancer Research等高影响力杂志
第一/通讯SCI论文累计影响因子大于45分

疾病介绍

本世纪初的一系列研究证实了染色质重塑蛋白BAF(也称为SWI/SNF)复合物分子在肿瘤发生中发挥重要作用。Wong等人在 2000年报道了由SMARCA4编码的BAF(SWI/SNF)复合物亚基的缺失,也被称为Brahma相关基因1(BRG1)[1]。前列腺癌、乳腺癌和胰腺癌的体外实验也证明了该基因的抑癌作用[2]。2003年,Reisman等人报道SMARCA4缺失在非小细胞肺癌(NSCLC)中也偶尔可见,并与较差预后相关[1]。2015年, LeLoarer等人报道19例患者,以年轻男性吸烟者为主,形态学上为快速增大的胸部肿块与横纹肌样特征,未分化免疫表型,伴SMARCA4缺失,并且疾病进展迅速。 由于这些肿瘤在转录组学上更类似于BAF缺失肉瘤,作者提出了新术语“SMARCA4缺失胸腔肉瘤(DTS)”来描述这类具有非常独特病理学特征的肿瘤[3]。很多组织来源的肿瘤均可伴发SMARCA4缺失,包括发生在肺、鼻窦、子宫内膜和胃肠道等,表现为局部肿瘤去分化和横纹肌样特征[4]。因此,SMARCA4-DTS和SMARCA4缺失的NSCLC之间存在一些形态学重叠也就不足为奇了,这两者之间的确切关系仍有待阐明。Rekhtman等人最近的一项研究在形态学、免疫组化和遗传学证据探索中表明SMARCA4-DTS可能为一种与吸烟相关的肉瘤样/未分化癌的新类型[5]。2021年WHO肿瘤分类标准使用术语““thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-DUT)”来替代先前描述为SMARCA4-DTS的肿瘤。SMARCA4-DUT目前被认为是一种区别与SMARCA4缺失NSCLC的肿瘤类型。

临床特征

胸腔SMARCA4-DUT多发生于年轻患者,平均年龄在30-59岁之间,绝大多数为男性大量吸烟者[3, 5]。患者胸腔肿块通常表现为体积大、浸润性、 压缩性以及淋巴结坏死的病理特征。虽然纵隔受累为主要表现,但大多数病例都与肺实质有局部黏连,通常伴随明显的肺气肿;并与NSCLC相似,容易远处转移,常累及骨、肺、脑和肾上腺[6]。诊断时的症状通常与疾病的发展程度相关,包括呼吸困难、胸痛、骨痛和骨或脑转移引起的癫痫发作。疾病进展迅速,大多数患者在数月内死亡;中位总生存期(mOS)为5-7个月[3, 6, 7],2年OS率仅为12.5%[7]。与胸腔SMARCA4-DUT患者相似,SMARCA4缺失的NSCLC患者往往是具有较大侵袭性肿块的年轻男性吸烟者,且生存期短,临床预后差[8]。

形态学和免疫组化特征

形态学上,SMARCA4缺失的NSCLC通常表现出实体成分为主[8],也可能显示出横纹肌样特征,在SMARCA4缺失的区域肿瘤细胞呈现非贴壁生长方式[9]。在某些病例中,这些低分化的实体区域可能与经典的中分化NSCLC区域相毗邻。在这种情况下,免疫组化显示SMARCA4(BRG1)缺失可能仅限于分化程度较差的区域,提示SMARCA4缺失是肿瘤进展/去分化的一种方式。然而,通过免疫组化方法,在中高分化的肺腺或鳞癌中也偶尔会观察到 SMARCA4/BRG1缺失[10]。

SMARCA4缺失的NSCLC通常表达角蛋白keratin阳性(强于SMARCA4-DUT), TTF1阴性,SMARCA2常同时表达[10]。角蛋白7和HepPar1阳性表达可用于区分SMARCA4缺失NSCLC的一个重要亚群[11]。HepPar1胞浆表达显示出与肝细胞癌相似的颗粒状形态;然而,肝细胞癌中常见的其他标记物如甲胎蛋白、甘氨糖-3或精氨酸酶 1在SMARCA4缺失的NSCLC中表达并不一致[11]。

治疗策略

尽管大多数治疗方案的疗效不佳,但有一些病例报告显示 ,使用纳武单抗(O药)[12]或派姆单抗(K药)[13, 14]治疗的患者肿瘤明显消退,这表明免疫治疗可能在SMARCA4-胸部肿瘤的治疗中发挥重要作用。

SMARCA4-肿瘤患者占NSCLC的8%,并可能受益于免疫检查点抑制剂[15]或含铂化疗[16]。 另有临床前研究表明,BAF(SWI/SNF)缺失肿瘤的患者可能受益于BET抑制剂的治疗[17]。

安罗替尼是一种小分子多靶点酪氨酸激酶抑制剂,能有效抑制VEGFR、PDGFR、FGFR、c-Kit等信号通路,具有抗肿瘤血管生成和抑制肿瘤生长的作用;适用于腺泡状软组织肉瘤、透明细胞肉瘤以及既往至少接受过含蒽环类化疗方案治疗后进展或复发的其他晚期软组织肉瘤患者的治疗。

笔者目前收治一例SMARCA4-NSCLC患者,应用派姆单抗(K药)联合安罗替尼治疗,连续15个月未进展,最佳疗效PR,此病人目前仍在K药联合安罗替尼治疗中。由此推测,免疫联合安罗替尼可能为SMARCA4-NSCLC患者的可选治疗方案之一。

参考文献

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