naphthoquinones and Leukemia--Promyelocytic--Acute

Acute promyelocytic leukemia (APL) is a special subtype of acute myeloid leukemia that responds to treatment with all‑trans retinoic acid and arsenic trioxide. However, severe side effects and drug resistance limit the effectiveness of these treatments. Hence, new drugs for APL are required urgently. Shikonin, an active naphthoquinone derived from the Chinese medical herb Zi Cao exerts antitumor activity in several cancers. In the present study, the effects of shikonin on proliferation and apoptosis in NB4 cells, as well as related mechanisms were assessed. Treatment of NB4 cells with shikonin inhibited proliferation in a concentration‑ and time‑dependent manner. The cell cycle was arrested in the G1 phase. NB4 cells treated with shikonin exhibited more apoptosis and higher levels of cleaved caspase‑3 and poly ADP‑ribose polymerase than control cells. Western blotting results demonstrated that the expression of p‑p38 mitogen‑activated protein kinase (p‑p38MAPK) and p‑c‑Jun N‑terminal kinase (p‑JNK) was increased significantly by shikonin treatment, while the expression of p‑ERK and c‑Myc was decreased. In summary, these findings indicated that shikonin inhibited cell proliferation and induced apoptosis partly through modulation of the MAPKs and downregulation of c‑Myc.

Topics: Apoptosis; Caspase 3; Cell Cycle; Cell Line, Tumor; Cell Nucleus Shape; Cell Proliferation; Down-Regulation; Humans; Leukemia, Promyelocytic, Acute; Microscopy, Fluorescence; Mitogen-Activated Protein Kinases; Naphthoquinones; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-myc

Plumbagin, a naphtoquinone from the roots of Plumbago zeylanica is known to possess anticancer and anti-bacterial activity. Based on the former finding of our group in vitro demonstrating its effectiveness in human promyelocytic leukemia cells, NB4, in this study we further revealed the mitochondrial pathway involved in plumbagin-induced apoptosis. We also found that the generation of ROS was a critical mediator in plumbagin-induced apoptosis, which would be abrogated completely by antioxidant, NAC. The anticancer effect of plumbagin was investigated in vivo using NB4 tumor xenograft in NOD/SCID mice. The incidence of formation, growth characteristics, body weight and volume of tumors were observed. The histopathologic examination of tumors and organs were made. The results showed that intraperitoneal injection of plumbagin (2mg/kg body weight) daily for 3 weeks resulted to a 64.49% reduction of tumor volume compared with the control. Furthermore, there was no overt manifestation of toxicity such as weight loss, tissue damage and behavior change which appeared in Doxorubicin-treated mice (1mg/kg thrice a week). These results indicate that plumbagin has potential as a novel therapeutic agent for myeloid leukemia.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Blotting, Western; Caspases; Cell Line, Tumor; Enzyme Activation; Humans; In Situ Nick-End Labeling; Leukemia, Promyelocytic, Acute; Male; Membrane Potential, Mitochondrial; Mice; Mice, Inbred NOD; Mice, SCID; Naphthoquinones; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species; Xenograft Model Antitumor Assays

According to previous clinical experiences of the authors, plumbago zeylanica was effective against acute promyelocytic leukemia (APL). However, its effectiveness has never been proven experimentally or unequivocally clinically. This study was aimed to investigate the effects of plumbagin on the proliferation, cell cycle and apoptosis of APL cell line NB4 Cells. Cell inhibitory rates were detected by MTT colorimetric assay; morphologic changes were observed under light microscope and transmission electron microscope; apoptosis-inducing effects were determined by DNA gel electrophoresis, annexin V/PI double-stained and PI single-stained flow cytometry. The results demonstrated that 2-15 micromol/L plumbagin inhibited the proliferation of NB4 cells in a dose-dependent manner. The morphologic changes of cell apoptosis, such as chromsome condensation and apoptotic body formation, were observed by light microscope and transmission electron microscope. Cell cycle analysis showed that NB4 cells were blocked in G2/M phase of cell cycle. And plumbagin induced annexin V+/PI- cell increase and DNA fragmentation. There was a correlation between cell apoptosis rates and the concentrations of plumbagin in dose-dependent manner (P < 0.05). It is concluded that for the first time the present study shows that plumbagin can inhibit cell proliferation, block cell cycle and induce apoptosis of APL cell line NB4 cells.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Humans; Leukemia, Promyelocytic, Acute; Naphthoquinones

Beta-Lapachone a novel topoisomerase inhibitor, has been found to induce apoptosis in various human cancer cells. In this study we report that a dramatic elevation of hydrogen peroxide (H2O2) in human leukemia HL-60 cells following 1 microM beta-lapachone treatment and that this increase was effectively inhibited by treatment with antioxidant N-acetyl-L-cysteine (NAC), ascorbic acid, alpha-tocopherol. NAC strongly prevented beta-lapachone-induced apoptotic characteristics such as DNA fragmentation and apoptotic morphology. However, treatment of HL-60 cells with another topoisomerase inhibitor camptothecin (CPT) did not induce H2O2 production as compared to untreated cells. NAC also failed to block CPT-induced apoptosis. Correlated with these findings, we found that cancer cell lines K562, MCF-7, and SW620, contained high level of intracellular glutathione (GSH), were not elevated in H2O2 and were resistant to apoptosis after treatment with beta-lapachone. In contrast, cancer cell lines such as, HL-60, U937, and Molt-4 which have lower level of GSH, were readily increased of H2O2 and were sensitive to this drug. Furthermore, ectopic overexpression of Bcl-2 in HL-60 cells also attenuated beta-lapachone-induced H2O2 and conferred resistance to beta-lapachone-induced cell death. Beta-Lapachone at the concentration as low as 0.25 microM effectively induced HL-60 cells to undergo monocytic differentiation, as evidenced by CD14 antigenicity and alpha-naphthyl acetate esterase activity. Again, the beta-lapachone-induced monocytic differentiation was suppressed by NAC. These results suggest that intracellular H2O2 generation plays a crucial role in beta-lapachone-induced cell death and differentiation.

Topics: Acetylcysteine; Antioxidants; Apoptosis; Ascorbic Acid; Cell Differentiation; DNA Fragmentation; Drug Resistance; Enzyme Inhibitors; Glutathione; Humans; Hydrogen Peroxide; Leukemia, Promyelocytic, Acute; Monocytes; Naphthoquinones; Proto-Oncogene Proteins c-bcl-2; Topoisomerase I Inhibitors; Tumor Cells, Cultured; Vitamin E

beta-Lapachone and certain of its derivatives directly bind and inhibit topoisomerase I (Topo I) DNA unwinding activity and form DNA-Topo I complexes, which are not resolvable by SDS-K+ assays. We show that beta-lapachone can induce apoptosis in certain cells, such as in human promyelocytic leukemia (HL-60) and human prostate cancer (DU-145, PC-3, and LNCaP) cells, as also described by Li et al. (Cancer Res., 55: 0000-0000, 1995). Characteristic 180-200-bp oligonucleosome DNA laddering and fragmented DNA-containing apoptotic cells via flow cytometry and morphological examinations were observed in 4 h in HL-60 cells after a 4-h, > or = 0.5 microM beta-lapachone exposure. HL-60 cells treated with camptothecin or topotecan resulted in greater apoptotic DNA laddering and apoptotic cell populations than comparable equitoxic concentrations of beta-lapachone, although beta-lapachone was a more effective Topo I inhibitor. beta-Lapachone treatment (4 h, 1-5 microM) resulted in a block at G0/G1, with decreases in S and G2/M phases and increases in apoptotic cell populations over time in HL-60 and three separate human prostate cancer (DU-145, PC-3, and LNCaP) cells. Similar treatments with topotecan or camptothecin (4 h, 1-5 microM) resulted in blockage of cells in S and apoptosis. Thus, beta-lapachone causes a block in G0/G1 of the cell cycle and induces apoptosis in cells before, or at early times during, DNA synthesis. These events are p53 independent, since PC-3 and HL-60 cells are null cells, LNCaP are wild-type, and DU-145 contain mutant p53, yet all undergo apoptosis after beta-lapachone treatment. Interestingly, beta-lapachone treatment of p53 wild type-containing prostate cancer cells (i.e., LNCaP) did not result in the induction of nuclear levels of p53 protein, as did camptothecin-treated cells. Like other Topo I inhibitors, beta-lapachone may induce apoptosis by locking Topo I onto DNA, blocking replication fork movement, and inducing apoptosis in a p53-independent fashion. beta-Lapachone and its derivatives, as well as other Topo I inhibitors, have potential clinical utility alone against human leukemia and prostate cancers.

Topics: Apoptosis; Breast Neoplasms; Camptothecin; Cell Division; Dimethyl Sulfoxide; Drug Screening Assays, Antitumor; G1 Phase; Humans; Leukemia, Promyelocytic, Acute; Male; Naphthoquinones; Prostatic Neoplasms; Resting Phase, Cell Cycle; Time Factors; Topoisomerase I Inhibitors; Tumor Cells, Cultured; Tumor Stem Cell Assay

beta-Lapachone, a plant product, has been shown to be a novel inhibitor of DNA topoisomerase I, with a mode of action different from camptothecin and a chemical structure distinct from those of current anti-cancer drugs. We observed that beta-lapachone, at concentrations of less than 8 microM, induces cell death with characteristics of apoptosis in human prostate cancer cell lines. This effect of beta-lapachone was also observed in a human promyelocytic leukemia cell line (HL-60). beta-Lapachone-induced apoptosis is independent of p53 expression, and ectopic overexpression of bcl-2 did not confer significant resistance to beta-lapachone. Among other human carcinoma and adenoma cell lines tested, human breast and ovary carcinoma showed sensitivity to the cytotoxic effect of beta-lapachone without manifesting signs of apoptosis. These results suggest that beta-lapachone is a potential compound to be added to cancer chemotherapy, particularly for prostate cancer.

Topics: Apoptosis; Cell Survival; Drug Screening Assays, Antitumor; Flow Cytometry; Humans; Leukemia, Promyelocytic, Acute; Male; Naphthoquinones; Prostatic Neoplasms; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured; Tumor Stem Cell Assay; Tumor Suppressor Protein p53

beta-Lapachone is a plant product that has been found to have many pharmacological effects. To date, very little is known about its biochemical target. In this study, we found that beta-lapachone inhibits the catalytic activity of topoisomerase I from calf thymus and human cells. But, unlike camptothecin, beta-lapachone does not stabilize the cleavable complex, indicating a different mechanism of action. beta-Lapachone inhibits topoisomerase I-mediated DNA cleavage induced by camptothecin. Incubation of topoisomerase I with beta-lapachone before adding DNA substrate dramatically increases this inhibition. Incubation of topoisomerase I with DNA prior to beta-lapachone makes the enzyme refractory, and treatment of DNA with beta-lapachone before topoisomerase has no effect. These results suggest a direct interaction of beta-lapachone with topoisomerase I rather than DNA substrate. beta-Lapachone does not inhibit binding of enzyme to DNA substrate. In cells, beta-lapachone itself does not induce a SDS-K(+)-precipitable complex, but it inhibits complex formation with camptothecin. We propose that the direct interaction of beta-lapachone with topoisomerase I does not affect the assembly of the enzyme-DNA complex but does inhibit the formation of cleavable complex.

Topics: Animals; Camptothecin; Cattle; Cell Line; DNA, Kinetoplast; Humans; Kinetics; Leukemia, Promyelocytic, Acute; Models, Structural; Molecular Structure; Naphthoquinones; Nucleic Acid Conformation; Plasmids; Protein Binding; Substrate Specificity; Thymus Gland; Topoisomerase I Inhibitors; Tumor Cells, Cultured

Based on the "2-phenylnaphthalene-type" structural pattern hypothesis developed in our laboratory, a number of benzo[b]naphtho[2,3-d]furan-6,11-diones were designed, synthesized, and evaluated in vitro for their inhibitory action against the growth of human promyelocytic leukemia cells (HL-60), small-cell lung cancer (SCLC), SCLC cells resistant to cisplatin (SCLC/CDDP), National Cancer Institute's disease-oriented primary antitumor 60 cell-line panel, and drug-stimulated topoisomerase II-mediated DNA cleavages. Many compounds designed were found to possess potent activity in one or more of the biological tests. In general, activity found in one of the cell lines tested is often echoed in other cell lines and many also expressed substantial inhibitory activity against topoisomerase II-mediated cleavage activities. One of these compounds, 3-[2-(dimethylamino)ethoxy]-1-hydroxybenzo[b]naphthol[2,3-d]furan- 6,11-dione (8j), exhibited strong inhibitory activity throughout the entire series of test panel. Thus, it appears that the proposed structural pattern hypothesis has received substantial support through experimental verification.

Topics: Antineoplastic Agents; Carcinoma, Small Cell; Cisplatin; DNA Topoisomerases, Type II; Furans; Humans; Leukemia, Promyelocytic, Acute; Naphthoquinones; Structure-Activity Relationship; Tumor Cells, Cultured