verlukast and Leukemia--Myeloid

The antibody-targeted therapeutic, gemtuzumab ozogamicin (GO, Mylotarg), is approved for treatment of relapsed acute myeloid leukemia (AML). We previously showed that AML blasts from GO refractory patients frequently express the drug transporters P-glycoprotein (Pgp) and/or multidrug resistance protein (MRP). We also previously reported that inhibition of drug transport by the Pgp modulator, cyclosporine A (CSA), can increase GO sensitivity in Pgp(+) AML cells and that the peripheral benzodiazepine receptor ligand, PK11195, sensitizes AML cells to standard chemotherapeutics both by inhibiting Pgp-mediated efflux and by promoting mitochondrial apoptosis. We now show that PK11195 also can overcome multiple resistance mechanisms to increase GO sensitivity in AML cells, including resistance associated with expression of drug transporters and/or antiapoptotic proteins. PK11195 substantially increases GO cytotoxicity in AML cells from many different cell lines and primary patient samples, often more effectively than CSA. We also show that PK11195 is nontoxic in NOD/SCID mice and can sensitize xenografted human AML cells to GO. Since PK11195 is well tolerated in humans as a single agent, its further study as a multifunctional chemosensitizer for anti-AML therapies, including GO-based therapies, is warranted.

Topics: Acute Disease; Aminoglycosides; Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; bcl-X Protein; Cyclosporine; Drug Resistance, Neoplasm; Gemtuzumab; Gene Expression Regulation, Leukemic; HL-60 Cells; Humans; Immunosuppressive Agents; Isoquinolines; Leukemia, Myeloid; Leukotriene Antagonists; Ligands; Mice; Mice, Inbred NOD; Mice, SCID; Propionates; Proto-Oncogene Proteins c-bcl-2; Quinolines; Receptors, GABA-A; Xenograft Model Antitumor Assays

Despite treatment with intensive chemotherapy, a considerable number of patients with acute myeloid leukemia (AML) die from their disease due to the occurrence of resistance. Overexpression of the transporter proteins P-glycoprotein (P-gp) and multidrug resistance protein (MRP) 1 has been identified as a major cause of cross-resistance to functionally and structurally unrelated drugs. In the present study, the functional activity of P-gp and MRP was determined in 104 de novo AML patients with a flow cytometric assay using rhodamine 123 (Rh123) in combination with PSC833 and carboxyfluorescein (CF) in combination with MK-571. The results were compared with clinical outcome and with known prognostic factors. The functional activity of P-gp and MRP, expressed as Rh123 efflux blocking by PSC833 and CF efflux blocking by MK-571, demonstrated a great variability in the AML patients. A strong negative correlation was observed between Rh123 efflux blocking by PSC833 and Rh123 accumulation (r(s) = -0.69, P < 0.001) and between CF efflux blocking by MK-571 and CF accumulation (r(s) = -0.59, P < 0.001). A low Rh123 accumulation and a high Rh123 efflux blocking by PSC833 were associated with a low complete remission (CR) rate after the first cycle of chemotherapy (P = 0.008 and P = 0.01, respectively). Patients with both low Rh123 and CF accumulation (n = 16) had the lowest CR rate (6%), whereas patients with both high Rh123 and CF accumulation (n = 11) had a CR rate of 73%. AML patients with French-American-British classification M1 or M2 showed a lower Rh123 accumulation than patients with French-American-British classification M4 or M5 (P = 0.02). No association was observed between the multidrug resistance parameters and overall survival of the AML patients. Risk group was the only predictive parameter for overall survival (P = 0.003).

Topics: Adolescent; Adult; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP-Binding Cassette Transporters; Cyclosporins; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Female; Flow Cytometry; Fluoresceins; Fluorescent Dyes; Glutathione; Humans; Leukemia, Myeloid; Male; Middle Aged; Multidrug Resistance-Associated Proteins; Neoplasm Proteins; Propionates; Quinolines; Randomized Controlled Trials as Topic; Reverse Transcriptase Polymerase Chain Reaction; Rhodamine 123; RNA, Messenger; Survival Analysis; Treatment Outcome; Tumor Cells, Cultured

Agonist-induced changes in intracellular calcium ion concentration ([Ca++]i) were examined in human monocytic leukemia THP-1 cells loaded with fura 2/acetoxymethyl ester (fura 2/AM). Leukotriene (LT)D4 induced a concentration-dependent biphasic response consisting of a transient phase (up to 5-fold peak increase) followed by a sustained phase, showing characteristics of a receptor-operated calcium channel. Homologous desensitization to LTD4 was observed. The responses to LTD4 were reduced by 80 to 90% in calcium-free buffer. The responses to LTD4 in a calcium-free buffer were dependent upon the duration of prior exposure of the cells to a calcium-free environment. The response at 30 or 60 min after exposure to calcium-free buffer was greater than that at earlier time points (time-dependent sensitization). Similar responses were obtained with THP-1 cells exposed to EDTA-containing buffer. It is speculated that such time-dependent sensitization is a result of changes at the receptor level. The responses to LTD4 were blocked by two specific LTD4 antagonists, MK-0571 and ICI-204,219, in a concentration-dependent manner. When given after addition of LTD4, MK-0571 or ICI-204,219 reversed the sustained phase of the LTD4-induced response, suggesting that maintenance of the response requires persistent activation of the LTD4 receptor. ICI-204,219 was 5 to 10 times more potent than MK-0571 (IC50 values of 1.1 and 9.3 nM, respectively), in agreement with results from radioligand binding studies reported separately.

Topics: Calcium; Cytosol; Humans; Indoles; Leukemia, Myeloid; Leukotriene Antagonists; Leukotriene D4; Membrane Proteins; Phenylcarbamates; Propionates; Quinolines; Receptors, Leukotriene; Sulfonamides; Tosyl Compounds; Tumor Cells, Cultured