ABSTRACT
Intracellular signal transduction by kinase-mediated phosphorylation is essential for the survival and growth of lymphoma cells. This study analysed the multikinase inhibitor sorafenib for its cytotoxic activity against lymphoma cells. We found that sorafenib reduced cell viability at low micromolar concentrations in a time-dependent manner in cell lines and primary cell suspensions representing major types of aggressive B- and T-cell lymphomas. In cells surviving short term exposure, proliferative arrest occurred leading to complete loss of in vitro clonogenicity. Previously described sorafenib targets within the RAF kinase family were found to be expressed and phosphorylated in all cell lines, and sorafenib perturbed the activation of classical RAF/MEK/ERK pathway targets. However, using a global phoshoprotein array, the most consistent downstream effect of sorafenib in NHL cells was the inhibition of mitogen-activated protein kinase 14 (MAPK14) and panAKT phosphorylation. In conclusion, sorafenib has significant in vitro efficacy against aggressive B- and T-cell lymphoma cells, associated with inhibition of MAPK14 and panAKT.
Subject(s)
Antineoplastic Agents/pharmacology , Benzenesulfonates/pharmacology , Lymphoma, Non-Hodgkin/drug therapy , Mitogen-Activated Protein Kinase 14/antagonists & inhibitors , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Pyridines/pharmacology , Apoptosis/drug effects , Cell Cycle/drug effects , Cell Death/drug effects , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical/methods , Humans , Lymphoma, Non-Hodgkin/metabolism , Lymphoma, Non-Hodgkin/pathology , Mitogen-Activated Protein Kinase 14/metabolism , Niacinamide/analogs & derivatives , Phenylurea Compounds , Phosphorylation , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction/drug effects , Sorafenib , Tumor Cells, Cultured , Tumor Stem Cell Assay/methodsABSTRACT
BACKGROUND: Inhibition of BCR-ABL tyrosine kinase activity has evolved as a mainstay of therapy for patients with chronic myeloid leukemia. However, a fraction of leukemic cells persists under targeted therapy and can lead to disease progression on cessation of treatment. DESIGN AND METHODS: We analyzed bone marrow progenitor cells with the side population phenotype, and characterized the role of the intracellular ABC transporter A3 in imatinib detoxification. RESULTS: BCR-ABL-positive leukemic cells contribute to the side population cell compartment in untreated patients. Such leukemic side population cells, as well as CD34-positive progenitors from chronic myeloid leukemia samples, strongly express the intracellular ABCA3. Functionally, ABCA3 levels are critical for the susceptibility of chronic myeloid leukemia blast cell lines to specific BCR-ABL inhibition by imatinib. The transporter is localized in the limiting membrane of lysosomes and multivesicular bodies, and intracellular [(14)C]-labeled imatinib accumulates in such organelles. The lysosomal storage capacity increases with ABCA3 expression, thus regulating imatinib sequestration. CONCLUSIONS: The intracellular ABC transporter A3 is expressed in chronic myeloid leukemia progenitor cells and may contribute to intrinsic imatinib resistance by facilitating lysosomal sequestration in chronic myeloid leukemia cells.
