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Title: Cellular mechanisms underlying complete hematological response of chronic myeloid leukemia to BRAF and MEK1/2 inhibition in a patient with concomitant metastatic melanoma
Austin Authors: Andrews, Miles C;Turner, Natalie;Boyd, Janis;Roberts, Andrew W;Grigg, Andrew P ;Behren, Andreas;Cebon, Jonathan S 
Affiliation: Medical Oncology, Austin Health, Heidelberg, Victoria, Australia
Ludwig Institute for Cancer Research, Austin Branch, Heidelberg, Victoria, Australia
Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria, Australia
School of Cancer Medicine, La Trobe University, Heidelberg, Victoria, Australia
Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
Clinical Haematology and Bone Marrow Transplantation, Royal Melbourne Hospital, Parkville, Victoria, Australia
Haematology, Austin Health, Austin Hospital, Heidelberg, Victoria, Australia
Issue Date: 1-Dec-2015 2015-07-22
Publication information: Clinical Cancer Research; 21(23): 5222-5234
Abstract: PURPOSE: Targeted MEK inhibition is an emerging therapy in a number of solid tumors. It holds particular promise in BRAF V600E mutation-positive malignant melanoma, where constitutive activation and cell growth through the MAP kinase (MAPK) pathway is well established. In vitro and preclinical research indicates that MAPK pathway activation is important in chronic myeloid leukemia (CML) leukemogenesis; however, the potential of MEK inhibition has not yet been investigated clinically in the setting of such hematologic malignancies. EXPERIMENTAL DESIGN: We report a case of complete hematologic response of CML to MEK inhibition in a patient with synchronous metastatic melanoma, who received treatment with combination BRAF and MEK1/2 inhibitors. We studied the effects of these agents on proliferation and outgrowth of myeloid precursors, and longitudinal shifts in peripheral blood phenotyping during the course of treatment. A model cell line system was used to examine the effects of dabrafenib and trametinib on MAPK and BCR-ABL1 signaling. RESULTS: After 35 weeks on treatment with BRAF and MEK inhibitors, complete hematologic response was observed without recourse to BCR-ABL1-targeted therapy. MEK inhibition was principally responsible for impaired proliferation of both mature and primitive myeloid precursors, as well as growth and hemoglobinization of erythroid precursors. Paradoxical activation of the MAPK pathway was seen in response to BRAF inhibitor therapy but this was easily overcome by clinically relevant doses of concurrent MEK inhibitor. CONCLUSIONS: These studies suggest that further evaluation of the optimal MAPK targeting approach is warranted to extend therapeutic options in CML.
DOI: 10.1158/1078-0432.CCR-15-0393
PubMed URL:
Type: Journal Article
Subjects: Antineoplastic Agents
Leukemia, Myelogenous, Chronic, BCR-ABL Positive
Proto-Oncogene Proteins B-raf
Protein Kinase Inhibitors
Appears in Collections:Journal articles

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