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Clonal evolution and resistance to EGFR blockade in the blood of colorectal cancer patients

An Erratum to this article was published on 07 July 2015

This article has been updated


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 samples1. 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.

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Figure 1: Mutated KRAS alleles emerge in circulating DNA during anti-EGFR therapy and decline when treatment is suspended.
Figure 2: Re-challenge with EGFR-specific antibodies in CRC cells and patients.
Figure 3: Mutated KRAS mutant clones dynamically evolve in response to pulsatile EGFR-specific antibody therapy.

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  • 26 June 2015

     In the version of this article initially published online, Alberto Bardelli´s e-mail address was incorrect. The correct address is The error has been corrected in the print, PDF and HTML versions of this article.


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The authors would like to thank all the patients that participated in the study and their families. We are grateful to the members of the Laboratory of Molecular Genetics at Candiolo Cancer Institute for critical reading and editing of this manuscript. We thank S. Destefanis for administrative support. We thank S. Lonardi and F. Bergamo (Istituto Oncologico Veneto) for clinical data collection. This work was supported by The EU Seventh Framework Programme under grant agreement no. 259015 COLTHERES (A. Bardelli); Associazione Italiana per la Ricerca sul Cancro (AIRC), IG grant no. 12812 (A. Bardelli); AIRC, MFAG grant no. 11349 (F.D.N.); Fondazione Piemontese per la Ricerca sul Cancro ONLUS (FPRC), 5 per mille 2009 Italian Ministry of Education, Universities and Research (MIUR) grant Farmacogenomica (F.D.N.); AIRC, 2010 Special Program Molecular Clinical Oncology 5 per mille, project no. 9970 (A. Bardelli); FPRC, 5 per mille 2010 and 2011 Italian Ministry of Health (A. Bardelli); and MIUR, grant PRIN (A. Bardelli). This work was partially supported by a grant to A. Avallone from the Italian Ministry of Health (RF2009-1539464). This work was supported by RD12/0036/0051, PI12/00989, PI12/00680, PT13/0010/0005 and 2014 SGR 740 grants and by the Xarxa de Banc de Tumors de Catalunya (C.M.). Investigators at Niguarda Cancer Center are supported by grant Terapia Molecolare Tumori by Fondazione Oncologia Niguarda Ca' Granda Onlus (A.S.-B. and S.S.). This work was also partially supported by Azioni, Ricerche e Cure in Oncologia (ARCO) (C.C., C.A., F.L., A.F.)

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Authors and Affiliations



A. Bardelli and G.S. designed the study. G.S., B.M., M.B., C.L., S.L., S.H., E.V., V.M., F.T. and B.B. performed the experiments. G.S., B.M., G. Corti, G. Crisafulli, E.M., G.R., S.V., F.D.N. and S.M. analyzed data. A.C., A.P., C.C., A. Amatu, A. Avallone, C.A., A. Budillon, C.M., P.R., A.F., R.B.C., F.L., S.S. and A.S.-B. treated patients and provided clinical samples. A. Bardelli and G.S. wrote the manuscript. A. Bardelli and A.S.-B. supervised the study.

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Correspondence to Andrea Sartore-Bianchi or Alberto Bardelli.

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Siravegna, G., Mussolin, B., Buscarino, M. et al. Clonal evolution and resistance to EGFR blockade in the blood of colorectal cancer patients. Nat Med 21, 795–801 (2015).

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