摘要
胰腺癌恶性程度高,预后差,目前群体研究证据所提供的治疗方案对改善胰腺癌的预后效果有限。究其原因,还是由于胰腺癌高度恶性的生物学行为以及个体间的异质性造成了其治疗效果的差异。精准治疗模式在癌症领域的蓬勃发展也为胰腺癌的治疗带来了新的希望。目前胰腺癌在靶向治疗、分子分型、个体化肿瘤模型等方面都有了一些进展,为精准治疗模式在胰腺癌治疗领域的应用提供了基础。胰腺癌的四大驱动突变(KRAS、TP53、CDKN2A、SMAD4)在胰腺癌的发生发展中起着重要作用,但目前还缺乏相对应的靶向药物。II期临床试验证实AMG510对有KRAS G12C突变的实体瘤患者治疗效果显著,但KRAS G12C突变在胰腺癌患者中占比较低。POLO试验结果提示奥拉帕利可以提高BRCA基因胚系突变的转移性胰腺癌患者的无进展生存期,基于此结果,NCCN指南已推荐奥拉帕利用于BRCA1/2基因胚系突变晚期胰腺癌的维持治疗。此外,KEYNOTE-158 II期临床试验提示存在错配修复缺陷相关基因(MLH1、MSH2等)突变以及高度微卫星不稳定的胰腺癌患者可能从PD-1抑制剂的治疗中获益。总体上看,目前胰腺癌可干预靶点较少,针对四大高频突变及其相关通路靶向药物的研发是胰腺癌精准治疗的重要方向。相对于传统的病理学分型,转录组学分型从胰腺癌患者的基因表达差异对患者进行分型,为精准治疗的实施提供更多有价值的信息。从2011年首个胰腺癌转录组学分型被提出后,已有多个研究从不同角度提出了新的转录组学分型标准。综合来看,根据转录组学特征可以将胰腺癌大致分为两型:经典型和基底样型。相对于经典型胰腺癌,基底样型胰腺癌对化疗的反应不佳,预后也更差。未来的研究中,表观遗传学和蛋白组学的发展可能会为胰腺癌的分子分型和临床转化提供新的路径。个体化肿瘤模型可以为癌症患者筛选潜在有效的治疗药物,是胰腺癌个体化治疗的又一重要途径。相对于传统的肿瘤细胞系,人源肿瘤异种移植模型(PDX)和类器官更好地保留了肿瘤的分子特征和生物学行为特征。我中心的研究实践证实了胰腺癌PDX和类器官有相对较高的建模成功率,其中类器官模型可以准确预测患者对化疗药物的敏感性。但是PDX和类器官在肿瘤微环境上与人体有较大差别,同时建模方法和药敏检测也缺乏统一标准,限制了其推广和应用。总体上看,胰腺癌的精准治疗还处于探索阶段。未来胰腺癌精准治疗的发展应侧重于借助多组学探索胰腺癌治疗的新靶点、建立生物样本库加速药物的临床前研究、开展前瞻性临床试验促进基础研究成果的临床转化。随着基础医学的进步以及精准医疗实践的深入,精准医疗模式一定能为胰腺癌的治疗带来更多的希望。
Chinese Journal of General Surgery, 2021, 30(9):997-1005.
胰腺癌恶性程度高,研究预测未来10年内胰腺癌相关死亡人数将上升至所有癌种的第2位,仅次于肺
美国国家癌症研究所将精准医学定义为“一种利用个体的基因、蛋白和环境信息来预防、诊断和治疗疾病的医学模式”。从2001年第1版人类基因组草图发表之后,基因分型和基因组学已为越来越多的癌种提供了有价值的治疗信息。目前肿瘤的精准治疗已拓展到包括转录组学、蛋白组学、疾病大数据、个体化肿瘤模型等多个领域,为肿瘤的治疗提供了新的突破口。在胰腺癌的基础和临床研究中,精准治疗也有了一些进展,主要集中在靶向治疗、分子分型、个体化肿瘤模型等方面。本文中,笔者对近年来胰腺癌精准治疗领域的研究进行了总结和展望。
胰腺癌的发生是一个多基因参与的复杂过程。胰腺癌相关的基因突变主要发生在KRAS、TP53、CDKN2A和SMAD4四个基因
虽然大多数胰腺癌都存在相似的核心突变,但不同的胰腺癌生物学行为仍有很大的不同,一些低频突变对胰腺癌的发生发展所起的作用也同样不可忽视。
同源DNA修复(homologous DNA repair,HDR)基因突变发生在约24%的胰导管腺癌(pancreatic ductal adenocarcinoma,PDAC)
程序性细胞死亡受体1(programmed cell death protein 1,PD-1)等免疫检查点抑制剂也是精准治疗研究的重要方向。研究显示,肿瘤突变负荷与PD-1治疗后的客观缓解率程正相
NTRK基因融合突变在促进肿瘤形成中起着重要作
除了以上治疗靶点外,其它还包括以ALK基因重排、NRG1基因融合、BRAF基因缺失为靶点的药物研究也在进行当中,不过还处于较早期的研究阶
2020年,“Know Your Tumor”项目的回顾性分析了靶向治疗对于胰腺癌患者生存结局的影
目前胰腺靶向治疗中存在的挑战主要是治疗靶点所覆盖的人群较少,以及临床医生对于胰腺癌靶向治疗的认识上存在不足。在胰腺癌患者中,存在可干预分子改变的患者约占所有胰腺癌的12%~25
总体上看,借鉴于其他癌种靶向治疗的经验,胰腺癌靶向治疗的时代序幕已缓缓拉开。但想要让更多胰腺癌患者真正从靶向治疗中获益,仍然任重道远。
传统的病理学分型是基于形态学,将胰腺癌分为导管腺癌、腺鳞癌和腺泡细胞癌等类型。但此分类方法对胰腺癌治疗的帮助较小,不同病理类型的胰腺癌通常也会用相同的化疗方案进行治疗。基于基因组学和转录组学的分析方法让我们认识到即便是相似的病理类型,也有着不同的分子改变和发展路径,而根据基因组和转录组等分子改变对胰腺癌患者进行分型,可以为精准治疗的实施提供更多有价值的信息。
2011年,Collisson
2015年,Moffitt
2016年,Bailey
2020年,Chan-Seng-Yue
除了上述研究外,来自癌症基因组图谱(The Cancer Genome Atlas,TCGA)的研
近年来,胰腺癌基因组学和转录组学发展迅速,对胰腺癌分子机制的认识有希望会为胰腺癌患者带来新的治疗方法和管理策略。但是,从总体上看,胰腺癌分子分型的发展还处于较初级的阶段,目前的胰腺癌分子分型对于患者预后的判断是有帮助的,但是对于治疗方案的选择帮助较小,这可能还需要前瞻性的临床试验进行探索。另外,胰腺癌的分子分型不应局限于基因组和转录组的分析,表观遗传学和蛋白组学的发展可能会为胰腺癌的分子分型和临床转化提供新的路径。
目前胰腺癌治疗靶点少的困境一时难以解决,而转录组学分型尚未带来治疗上的进步,所以用胰腺癌患者来源的肿瘤组织建立个体化的肿瘤模型,为患者筛选敏感的化疗药物或靶向药物,成为了胰腺癌个体化治疗的又一重要途径。目前常用的个体化肿瘤模型主要包括人源肿瘤异种移植模型(patient-derived tumor xenograft,PDX)和类器官(organoid)。相对于传统的肿瘤细胞系,PDX和类器官更好地保留了原始肿瘤的分子特征和生物学行为特
PDX模型是通过将手术或穿刺获得的肿瘤组织移植到免疫缺陷小鼠的皮下或者原位器官而建
Hidalgo
但是PDX模型也有一定的局限性。首先,PDX建模所需的组织多来源于手术切除,而胰腺癌的手术切除率只有15%~20
类器官是成体干细胞或多能干细胞在体外三维培养而形成的具有特定空间结构的细胞团,它能够模拟体内组织的结构和功能,并在体外进行长期传代。对人体来源的肿瘤细胞在合适条件下进行三维培养,就可以的得到个体化的肿瘤类器官模型。肿瘤类器官同样也可以保留肿瘤的组织形态学、基因组及转录组等特
相对于PDX,类器官的培养需要的细胞量较少,穿刺所获得的细胞也能保证较高的培养成功
同样,类器官作为一种肿瘤研究模型,也存在一些局限性。首先,类器官模型缺乏间质成分和免疫成
虽然PDX和类器官都具有一些局限性,但两者作为最具临床应用前景的肿瘤模型,其价值已经被多项研究所证实,随着新技术的发展以及培养成本的下降,它们有望在胰腺癌的个体化治疗中发挥更大的作用。
总体上看,胰腺癌的精准治疗还处于探索阶段,基础研究的进步尚未有效转化为临床的获益。笔者认为胰腺癌的精准治疗还应从以下几个方面进行发展和完善:首先,应借鉴其他癌种精准治疗的成功经验,从基因组、转录组、蛋白质组、表观遗传学等方面探索胰腺癌的发生发展规律,为开发新的靶向药物和利用已有的靶向药物提供理论支持。其次是建立胰腺癌PDX及类器官生物样本库,为胰腺癌患者提供个体化的用药指导,同时利用生物样本库加速新药的临床前研究。第三是开展前瞻性的临床研究,为精准医疗的实施提供证据支持,促进基础研究成果的临床转化。虽然目前胰腺癌的精准治疗仍然迷雾重重,但已经有越来越多的研究证实了精准治疗模式在胰腺癌治疗中的巨大潜力。随着研究者对胰腺癌认识上的深入,精准治疗模式一定能使更多胰腺癌患者获益。
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