Polymerase proofreading domain mutations: new opportunities for immunotherapy in hypermutated colorectal cancer beyond MMR deficiency

Publication date: Available online 23 March 2017
Source:Critical Reviews in Oncology/Hematology
Author(s): Rémi Bourdais, Benoît Rousseau, Anaïs Pujals, Helene Boussion, Charlotte Joly, Aude Guillemin, Isabelle Baumgartner, Cindy Neuzillet, Christophe Tournigand
Immune checkpoint inhibition is a new therapeutic strategy that has shown promising efficacy in many cancer types. Significant activity associated with mismatch repair (MMR) deficiency has been observed in hypermutated, microsatellite unstable (MSI) metastatic colorectal cancer (CRC). Beyond deficient-MMR tumors, somatic or germline DNA polymerase D1 (POLD1) or DNA polymerase E (POLE) alterations cause a hypermutated phenotype in CRC. This recently identified and rare subgroup of proficient-MMR tumors may also benefit from immunotherapy.In this review, we provide a comprehensive overview of recent data on CRC tumors harboring POLD1 or POLE mutations, with a focus on their molecular, histological, and clinical features. We also examine the evidence supporting the development of immune checkpoint inhibitors in this specific subgroup of CRC patients.



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