Inhibition of MDR1 activity and induction of apoptosis by analogues of nifedipine and diltiazem: an in vitro analysis.
We report herein the reversal of multidrug resistance-1 (MDR1) in A2780/DX3 cells by the two nifedipine-like compounds 1 and 2 that are part of a library of 1,4-dihydropyridines (1,4-DHPs) calcium-channel modulators bearing in C-4 a different substituted imidazo[2,1-b]thiazole system. By methylthiazol tetrazolium (MTT) assay, cytofluorimetry, and fluorescence microscopy we evaluated their ability to reverse MDR in our cell system. Moreover, together with compound 3 (the diltiazem-like 8-(4-chlorophenyl)-5-methyl-8-[(2Z)-pent-2-en-1-yloxy]-8H-[1,2,4]oxadiazolo[3,4-c][1,4]thiazin-3-one) we analyzed their ability to potentiate the triggering of apoptosis after exposure to doxorubicin, through the nuclear morphological analysis after 4',6-diamidino-2-phenylindole (DAPI), the fluorescein isothiocyanate (FITC)-Annexin-V/propidium iodide (PI) staining and the caspase activity determination. Our results demonstrate that compounds 1 and 2, at concentrations showing a very low (5%) or absent inhibition of cell proliferation, in combination with doxorubicin enhance its antiproliferative activity (from 30% to 54% IC(50) reduction) in A2780/DX3 cells through an increase of doxorubicin intracellular accumulation. These compounds together with compound 3, which has already been demonstrated to act as a potent inhibitor of MDR1 function, were also able to significantly potentiate the activation of the apoptosis machinery triggered by the exposure to doxorubicin. In conclusion, our results identify two new molecules structurally related to the calcium-channel blocker nifedipine, but characterized by a very low LTCC blockers activity, able to potentiate the antiproliferative and apoptotic activities of doxorubicin through an increase of its intracellular concentration likely caused by the inhibition of MDR1 function.
Viale
Maurizio
M
Istituto Nazionale per la Ricerca sul Cancro, S.C. Terapia Immunologica, L.go R. Benzi 10, 16132, Genova, Italy. maurizio.viale@istge.it
Cordazzo
Cinzia
C
de Totero
Daniela
D
Budriesi
Roberta
R
Rosano
Camillo
C
Leoni
Alberto
A
Ioan
Pierfranco
P
Aiello
Cinzia
C
Croce
Michela
M
Andreani
Aldo
A
Rambaldi
Mirella
M
Russo
Patrizia
P
Chiarini
Alberto
A
Spinelli
Domenico
D
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004110:Diltiazem / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007211:Indoles / Q000378:metabolism; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D011419:Propidium / Q000378:metabolism; D013194:Staining and Labeling
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017304:Annexin A5; D007211:Indoles; D011419:Propidium; C007293:DAPI; D004317:Doxorubicin; D020169:Caspases; D004110:Diltiazem; D009543:Nifedipine