Antitumor effects of celecoxib on K562 leukemia cells are mediated by cell-cycle arrest, caspase-3 activation, and downregulation of Cox-2 expression and are synergistic with hydroxyurea or imatinib.
Celecoxib, a specific cyclooxygenase-2 (Cox-2) inhibitor, has been shown to possess antitumor activity in a variety of cancer cells. However, the antitumor activity of celecoxib in hematopoietic tumors, especially in chronic myeloid leukemia (CML), has not been well established. This study was designed to investigate the effect of celecoxib on growth and apoptosis in a human CML cell line (K562 cells) or in primary CML cells, and to examine the synergistic actions of celecoxib and hydroxyurea or imatinib on K562 cell proliferation and apoptosis. Celecoxib significantly inhibited the growth of both K562 and primary CML cells and induced apoptosis in a dose-dependent fashion. The IC50 of celecoxib was 46 microM for inhibition of K562 cell proliferation. The effect of celecoxib on growth inhibition was accompanied by the downregulation of cyclin D1 and cyclin E and p-Rb expression, the upregulation of P16(INK4a) and P27KIP expression, and a G1-S phase arrest of the cell cycle. The pro-apoptotic effect of celecoxib was determined to be mediated by caspase-3 activation. When K562 cells were pretreated with DEVD-fmk, a specific inhibitor of caspases, the apoptotic activity of celecoxib was, in part, abrogated. Importantly, we demonstrated for the first time that K562 cells were Cox-2-positive both at the mRNA and protein levels. We noted the following observations: (i) we detected Cox-2 mRNA in K562 cells by reverse transcription-PCR (RT-PCR) and protein expression by western blot analysis; (ii) Cox-2 expression in K562 cells was stimulated by IL-1beta, a specific inducing agent of Cox-2 expression; (iii) primary CML cells from CML patient bone marrow also exhibited Cox-2 protein expression. Furthermore, Cox-2 expression was downregulated at higher doses of celecoxib (80-160 microM), suggesting a Cox-2-dependent mechanism was involved in the drug's effects of growth inhibition and induction of apoptosis. In addition, a synergistic effect was observed when cells were exposed to low-dose celecoxib (40 microM) and hydroxyurea (10 mM) or a combination of celecoxib (40 microM) and imatinib (0.2 microM). These findings provide the basis for uncovering the mechanism of celecoxib's antitumor effects and developing a new therapeutic strategy for treating CML.
Zhang
Guang-Sen
GS
Division of Hematology, Institute of Molecular Hematology, The Second Xiang Ya Hospital, Central South University, Changsha City, Hunan, PR China. zgsllzy@public.cs.hn.cn
Liu
Ding-Sheng
DS
Dai
Chong-Wen
CW
Li
Rui-Juan
RJ
D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D001854:Bone Marrow Cells / Q000201:enzymology / Q000473:pathology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D000068579:Celecoxib; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D016193:G1 Phase / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology / Q000627:therapeutic use; D000068877:Imatinib Mesylate; D007375:Interleukin-1 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D010879:Piperazines / Q000494:pharmacology / Q000627:therapeutic use; D011720:Pyrazoles / Q000494:pharmacology / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology / Q000627:therapeutic use; D016196:S Phase / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology / Q000627:therapeutic use
D000970:Antineoplastic Agents; D001549:Benzamides; C436291:CDKN1B protein, human; D061945:Caspase Inhibitors; D019927:Cyclin E; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010879:Piperazines; D011720:Pyrazoles; D011743:Pyrimidines; D013449:Sulfonamides; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000068877:Imatinib Mesylate; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000068579:Celecoxib; D006918:Hydroxyurea