Chung Hoow Kok

Contrasting effects of diclofenac and ibuprofen on active imatinib uptake into leukaemic cells

Background:The human organic cation transporter-1 (OCT-1) is the primary active protein for imatinib uptake into target BCR-ABL-positive cells. Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used by chronic myeloid leukaemia (CML) patients on imatinib to manage musculoskeletal complaints.Methods:Here we investigated the impact of NSAIDs on functional activity of the OCT-1 (OCT-1 activity; OA) in CML cells.Results:Although ten of twelve NSAIDs tested had no significant impact on OA (P>0.05), we observed increased OA (27% increase in K562; 22% increase in KU812 cells, P<0.05) and reduced IC50imatinib when treated with diclofenac. Co-incubation with imatinib and diclofenac resulted in a significantly lower viable cell number compared with imatinib alone. In contrast, ibuprofen led to a significant decrease in OA, an increase in IC50imatinib and thus reduced the cytotoxicity of imatinib. In primary CML samples, diclofenac significantly increased OA, particularly in patients with low OA (<4u2009ng per 200u2009000 cells), and significantly decreased IC50imatinib. Ibuprofen induced significant decreases in OA in CML samples and healthy donors.Conclusion:On the basis of the expected impact of these two drugs on OA, ibuprofen should be avoided in combination with imatinib. Further studies are warranted regarding the potential benefit of diclofenac to improve OA in a clinical setting.

Repression of Gadd45α by activated FLT3 and GM-CSF receptor mutants contributes to growth, survival and blocked differentiation

The tumor suppressor Gadd45α was earlier shown to be a repressed target of sustained receptor-mediated ERK1/2 signaling. We have identified Gadd45α as a downregulated gene in response to constitutive signaling from two FLT3 mutants (FLT3-ITD and FLT3-TKD) commonly found in AML, and a leukemogenic GM-CSF receptor trans-membrane mutant (GMR-V449E). GADD45A mRNA downregulation is also associated with FLT3-ITD+ AML. Sustained ERK1/2 signaling contributes significantly to receptor-mediated downregulation of Gadd45α mRNA in FDB1 cells expressing activated receptor mutants, and in the FLT3-ITD+ cell line MV4;11. Knockdown of Gadd45α with shRNA led to increased growth and survival of FDB1 cells and enforced expression of Gadd45α in FDB1 cells expressing FLT3-ITD or GMR-V449E resulted in reduced growth and viability. Gadd45α overexpression in FLT3-ITD+ AML cell lines also resulted in reduced growth associated with increased apoptosis and G1/S cell cycle arrest. Overexpression of Gadd45α in FDB1 cells expressing GMR-V449E was sufficient to induce changes associated with myeloid differentiation suggesting Gadd45α downregulation contributes to the maintenance of receptor-induced myeloid differentiation block. Thus, we show that ERK1/2-mediated downregulation of Gadd45α by sustained receptor signaling contributes to growth, survival and arrested differentiation in AML.

GADD45A methylation predicts poor overall survival in acute myeloid leukemia and is associated with IDH1/2 and DNMT3A mutations.

GADD45A methylation predicts poor overall survival in acute myeloid leukemia and is associated with IDH 1/2 and DNMT3A mutations

Low GFI1 expression in white blood cells of CP-CML patients at diagnosis is strongly associated with subsequent blastic transformation.

Low GFI1 expression in white blood cells of CP–CML patients at diagnosis is strongly associated with subsequent blastic transformation

Elevated PTPN2 expression is associated with inferior molecular response in de-novo chronic myeloid leukaemia patients.

Elevated PTPN2 expression is associated with inferior molecular response in de-novo chronic myeloid leukaemia patients