ABSTRACT
For obtaining new structural compounds with unique resistance profiles or novel mechanisms of action on HIV-1 from natural products, anti-HIV-1 drug screening models were used in vitro. Norcantharidin (NCTD), a derivative from cantharidin, was found to have inhibitory activities on HIV-1(IIIB) p24 antigen in lymphocyte lines MT-4, CEM and H9. It inhibited HIV-1 strain 018a (sensitive to zidovudine) from replicating with EC50 (50% effective concentration) of 14.9 micromol L(-1) and also inhibited HIV-1 strain 018c (resistant to zidovudine) from replicating with EC50 of 20.2 micromol L(-1) in primary lymphocytes peripheral blood mononuclear cells (PBMC). Norcantharidin showed synergistic activity with zidovudine on HIV-1(IIIB) in MT-4 cells, the combination index was less than 0.3. But, it was not active on HIV-1 integrase, reverse transcriptase or protease in vitro. As the structure of norcantharidin is unique and different from that of all clinic drugs approved, it would be possible to obtain new and effective compounds against HIV-1 with low toxicities after modification of norcantharidin.
Subject(s)
Anti-HIV Agents/pharmacology , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , HIV Core Protein p24/metabolism , Virus Replication , Cell Line , Drug Resistance, Viral , Drug Synergism , HIV Integrase/metabolism , HIV-1/metabolism , Humans , Leukocytes, Mononuclear/cytology , Leukocytes, Mononuclear/virology , Peptide Hydrolases/metabolism , RNA-Directed DNA Polymerase/metabolism , T-Lymphocytes/cytology , T-Lymphocytes/virology , Zidovudine/pharmacologyABSTRACT
BACKGROUND & OBJECTIVE: Norcantharidin (NCTD), the demethylated form of cantharidin, can inhibit the proliferation of many kinds of cancer cells, but its effect is milder than those of other drugs. This study was to explore the inhibitory effect of Nd3, a derivative of norcantharidin, on the proliferation of human ovarian cancer cell line SKOV3, compare its antitumor effect with that of norcantharidin, and investigate its possible molecular mechanisms. METHODS: SKOV3 cells were treated with Nd3 and norcantharidin, separately. Cell proliferation was evaluated by sulforhodamine B (SRB) assay. Cell cycle distribution and apoptosis were detected by flow cytometry. The expression of Cdc2, Cyclin B1, Bax, and Bcl-2 was detected by Western blot. RESULTS: When treated with 2.5, 5, 10, 20, 30, and 40 micromol/L Nd3 for 48 h, the inhibition rates of SKOV3 cells were 27.3%, 34.1%, 53.3%, 64.3%, 83.3%, and 96.7%, respectively, which were significantly higher than that of negative control cells (P<0.001). The 50% inhibition concentration of Nd3 was (25.1+/-2.3) micromol/L at 24 h, (21.8+/-2.8) micromol/L at 36 h, and (20.4+/-3.3) micromol/L at 48 h. When treated with 10, 20, 30, and 40 micromol/L Nd3 for 48 h, SKOV3 cells were arrested at G2/M phase at rates of 14.3%, 20.2%, 26.2%, and 27.9%; when treated with 30 micromol/L Nd3 for 12, 24, 36, and 48 h, the proportions of SKOV 3 cells at G2/M phase were 19.8%, 26.6%, 27.8%, and 32.0%. When treated with 40 micromol/L Nd3 for 48 h, the apoptosis rate of SKOV3 cells was significantly higher than that of control cells [(17.9+/-4.4)% vs. (2.5+/-2.8)%, P<0.01]. After treatment of Nd3, the expression of Cdc2, Cyclin B1, and Bcl-2 were down-regulated, and the expression of Bax was up-regulated. CONCLUSIONS: Nd3 inhibits SKOV3 cell proliferation more than norcantharidin does, blocks cell cycle at G2/M phase, and induces apoptosis. The antitumor mechanism of Nd3 is related to the changes of Cdc2, Cyclin B1, Bax, and Bcl-2 expression.
