title: Fitness conferred by BCR-ABL kinase domain mutations determines the risk of pre-existing resistance in chronic myeloid leukemia.
abstract: Chronic myeloid leukemia (CML) is the first human malignancy to be successfully treated with a small molecule inhibitor, imatinib, targeting a mutant oncoprotein (BCR-ABL). Despite its successes, acquired resistance to imatinib leads to reduced drug efficacy and frequent progression of disease. Understanding the characteristics of pre-existing resistant cells is important for evaluating the benefits of first-line combination therapy with second generation inhibitors. However, due to limitations of assay sensitivity, determining the existence and characteristics of resistant cell clones at the start of therapy is difficult. Here we combined a mathematical modeling approach using branching processes with experimental data on the fitness changes (i.e., changes in net reproductive rate) conferred by BCR-ABL kinase domain mutations to investigate the likelihood, composition, and diversity of pre-existing resistance. Furthermore, we studied the impact of these factors on the response to tyrosine kinase inhibitors. Our approach predicts that in most patients, there is at most one resistant clone present at the time of diagnosis of their disease. Interestingly, patients are no more likely to harbor the most aggressive, pan-resistant T315I mutation than any other resistance mutation; however, T315I cells on average establish larger-sized clones at the time of diagnosis. We established that for patients diagnosed late, the relative benefit of combination therapy over monotherapy with imatinib is significant, while this benefit is modest for patients with a typically early diagnosis time. These findings, after pre-clinical validation, will have implications for the clinical management of CML: we recommend that patients with advanced-phase disease be treated with combination therapy with at least two tyrosine kinase inhibitors.
authors.affiliation: Program for Industrial and Systems Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Kevin
authors.initials: K
authors.lastname: Leder
authors.forename: Jasmine
authors.initials: J
authors.lastname: Foo
authors.forename: Brian
authors.initials: B
authors.lastname: Skaggs
authors.forename: Mercedes
authors.initials: M
authors.lastname: Gorre
authors.forename: Charles L
authors.initials: CL
authors.lastname: Sawyers
authors.forename: Franziska
authors.initials: F
authors.lastname: Michor
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D016044:Fusion Proteins, bcr-abl / Q000737:chemistry* / Q000235:genetics*; D056084:Genetic Fitness / Q000187:drug effects; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000175:diagnosis / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D059645:Mutation Rate; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics*; D012307:Risk Factors; D013997:Time Factors
chemical_list: D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl