Siravegna Giulia, Mussolin Benedetta, Buscarino Michela, Corti Giorgio, Cassingena Andrea, Crisafulli Giovanni, Ponzetti Agostino, Cremolini Chiara, Amatu Alessio, Lauricella Calogero, Lamba Simona, Hobor Sebastijan, Avallone Antonio, Valtorta Emanuele, Rospo Giuseppe, Medico Enzo, Motta Valentina, Antoniotti Carlotta, Tatangelo Fabiana, Bellosillo Beatriz, Veronese Silvio, Budillon Alfredo, Montagut Clara, Racca Patrizia, Marsoni Silvia, Falcone Alfredo, Corcoran Ryan B, Di Nicolantonio Federica, Loupakis Fotios, Siena Salvatore, Sartore-Bianchi Andrea, Bardelli Alberto
1] University of Torino, Department of Oncology, Torino, Italy. [2] Candiolo Cancer Institute - Fondazione Piemontese per l'Oncologia (FPO), Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Candiolo, Torino, Italy. [3] Fondazione Italiana per la Ricerca sul Cancro (FIRC) Institute of Molecular Oncology (IFOM), Milano, Italy.
Candiolo Cancer Institute - Fondazione Piemontese per l'Oncologia (FPO), Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Candiolo, Torino, Italy.
Nat Med. 2015 Jul;21(7):795-801. doi: 10.1038/nm.3870. Epub 2015 Jun 1.
Colorectal cancers (CRCs) evolve by a reiterative process of genetic diversification and clonal evolution. The molecular profile of CRC is routinely assessed in surgical or bioptic samples. Genotyping of CRC tissue has inherent limitations; a tissue sample represents a single snapshot in time, and it is subjected to spatial selection bias owing to tumor heterogeneity. Repeated tissue samples are difficult to obtain and cannot be used for dynamic monitoring of disease progression and response to therapy. We exploited circulating tumor DNA (ctDNA) to genotype colorectal tumors and track clonal evolution during treatment with the epidermal growth factor receptor (EGFR)-specific antibodies cetuximab or panitumumab. We identified alterations in ctDNA of patients with primary or acquired resistance to EGFR blockade in the following genes: KRAS, NRAS, MET, ERBB2, FLT3, EGFR and MAP2K1. Mutated KRAS clones, which emerge in blood during EGFR blockade, decline upon withdrawal of EGFR-specific antibodies, indicating that clonal evolution continues beyond clinical progression. Pharmacogenomic analysis of CRC cells that had acquired resistance to cetuximab reveals that upon antibody withdrawal KRAS clones decay, whereas the population regains drug sensitivity. ctDNA profiles of individuals who benefit from multiple challenges with anti-EGFR antibodies exhibit pulsatile levels of mutant KRAS. These results indicate that the CRC genome adapts dynamically to intermittent drug schedules and provide a molecular explanation for the efficacy of rechallenge therapies based on EGFR blockade.
结直肠癌（CRC）通过基因多样化和克隆进化的反复过程演变。CRC的分子特征通常在手术或活检样本中进行评估。CRC组织的基因分型存在固有局限性；组织样本代表一个时间点的单一快照，并且由于肿瘤异质性而受到空间选择偏差的影响。重复获取组织样本很困难，并且不能用于动态监测疾病进展和对治疗的反应。我们利用循环肿瘤DNA（ctDNA）对结直肠肿瘤进行基因分型，并在使用表皮生长因子受体（EGFR）特异性抗体西妥昔单抗或帕尼单抗治疗期间追踪克隆进化。我们在以下基因中鉴定出对EGFR阻断有原发性或获得性耐药的患者ctDNA中的改变：KRAS、NRAS、MET、ERBB2、FLT3、EGFR和MAP2K1。在EGFR阻断期间出现在血液中的突变KRAS克隆，在停用EGFR特异性抗体后下降，这表明克隆进化在临床进展后仍在继续。对已获得对西妥昔单抗耐药性的CRC细胞进行药物基因组分析表明，在停用抗体后KRAS克隆衰减，而群体恢复药物敏感性。从多次使用抗EGFR抗体治疗中获益个体的ctDNA谱显示出突变KRAS的脉动水平。这些结果表明，CRC基因组对间歇性给药方案具有动态适应性，并为基于EGFR阻断的再挑战疗法的疗效提供了分子解释。
