title: Enhancement of arabinocytosine (AraC) toxicity to AML cells by a differentiation agent combination.
abstract: Arabinocytosine (AraC, also known as cytarabine) is one of the mainstays of AML therapy, but like other DNA damaging therapeutic agents it is rarely curative by itself. There is an emerging realization that the therapeutic outcomes may be improved by combining AraC with other compounds. Here we report that the addition of a differentiating agent combination immediately following AraC damage to AML blasts, selectively increases the cell kill. The experiments were performed using cultured cells from established cell lines of AML (HL60 and U937). The cells were exposed to 100nM AraC, a concentration which produced approximately 25-50% cell kill, followed by a combination of 100nM 1alpha-hydroxyvitamin D2 (1-D2) and 10μM carnosic acid (CA), which together can serve as a powerful differentiating agent combination for AML cells, but are not toxic alone. AraC-induced cell death, measured by annexin V/propidium iodide, was significantly (p<0.01) increased by the 1-D2/CA combination in both cell lines, but not by 1-D2 or CA alone. The enhancement of cell death occurred by both apoptosis and necrosis, was associated with increased DNA damage and with higher levels of DNA damage response (DDR) activated marker Chk1, but the expression of p27, a cell cycle inhibitor protein, was not enhanced by 1-D2/CA. The principal finding is that a vitamin D analog 1-D2 combined with a plant-derived antioxidant CA can markedly augment the cytotoxic action of AraC, an anti-leukemia therapeutic agent.
authors: Department of Pathology & Laboratory Medicine, NJ Medical School, Rutgers, 185 South Orange Ave, Newark, NJ 07103, United States.
authors: Xuening
authors: X
authors: Wang
authors: Department of Medicine, University of Missouri Medical School, Columbia, MO 65212, United States.
authors: Jonathan S
authors: JS
authors: Harrison
authors: Department of Pathology & Laboratory Medicine, NJ Medical School, Rutgers, 185 South Orange Ave, Newark, NJ 07103, United States. Electronic address: studzins@njms.rutgers.edu.
authors: George P
authors: GP
authors: Studzinski
mesh_terms: D045784:Abietanes / Q000737:chemistry; D017304:Annexin A5 / Q000737:chemistry; D000964:Antimetabolites, Antineoplastic / Q000737:chemistry* / Q000494:pharmacology; D000975:Antioxidants / Q000737:chemistry; D017209:Apoptosis / Q000187:drug effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors; D002454:Cell Differentiation; D020552:Comet Assay; D003561:Cytarabine / Q000737:chemistry* / Q000494:pharmacology; D004249:DNA Damage; D004872:Ergocalciferols / Q000737:chemistry; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy*; D010766:Phosphorylation; D011419:Propidium / Q000737:chemistry; D020298:U937 Cells
chemical_list: D045784:Abietanes; D017304:Annexin A5; D000964:Antimetabolites, Antineoplastic; D000975:Antioxidants; D018797:Cell Cycle Proteins; D004872:Ergocalciferols; D003561:Cytarabine; D011419:Propidium; C042533:1 alpha-hydroxyergocalciferol; C018381:salvin
keywords: Acute myeloid leukemia (AML); Apoptosis; AraC; Chk1; Plant antioxidant; VDR; Vitamin D analog