Selective cytotoxicity of diazenecarboxamides towards human leukemic cell lines.

In this study, the cytotoxicity of 16 diazenes towards four human leukemic cell lines was tested. Regarding their structure these 16 diazenes belong to three subclasses: diazenecarboxamides (11 compounds), diazenedicarboxamides (4 compounds) and alkyl aminocarbonyldiazenecarboxylate (1 compound). The leukemic cell lines used in this study were NALM-1, JURKAT, HL-60 and K-562. Fifteen out of 16 tested diazenes were cytotoxic towards the leukemic cell lines: 11 with high efficacy (IC(50)<50 microM) at least towards two to three leukemic cell lines, and 4 with medium efficacy (IC(50)>50 microM). Ten out of these 11 diazenes have a common structure and belong to the subclass of diazenecarboxamides. Five diazenes (SB-681, LK-34, UP-39, JK-1197, UP-11) were highly cytotoxic (IC(50) values 3.3-38.9 microM) towards all four leukemic cell lines. The selectivity of the cytotoxicity towards leukemic cells was tested by using resting and Con-A-stimulated peripheral blood mononuclear cells (PBMC) isolated from healthy donors and towards normal mouse fibroblast cell line, 3T3. The diazenes cytotoxic towards leukemic cells, did not affect the viability of the resting PBMC suggesting selectivity of their action. Moreover, eight diazenes did not affect the normal dividing cells (Con-A-stimulated PBMC and fibroblasts). Thus, we present eight diazenes which are selectively cytotoxic towards leukemic cells, not affecting normal cells even when activated to proliferation. These compounds may represent new potential agents for the treatment of leukemia patients.

Diazene JK-279 induces apoptosis-like cell death in human cervical carcinoma cells.

Diazene N-phenyl-2-(2-pyridinyl)diazenecarboxamide (JK-279) is a newly synthesized compound, cytotoxic for several tumor cell lines and their drug-resistant sublines. In human cervical carcinoma cells (HeLa), this compound reduced intracellular glutathione content and increased sensitivity to cisplatin. The aim of the present study was to elucidate the molecular mechanisms involved in the cytotoxic effect of diazene JK-279 on HeLa cells. Cytotoxicity was determined by the MTT method. Flow cytometry analysis showed that diazene JK-279 induces G(2)/M phase arrest, mediated by the increase in p21 expression, and accompanied by an alteration in the expression of survivin. The highest concentration of JK-279 altered nuclear morphology in intact cells, showing "apoptosis-like" features. No cleavage of procaspase-3, procaspase-9 and PARP, or altered expression of apoptotic proteins Bcl-2 and Bax were detected. At the same time, PS externalization and internucleosomal DNA cleavage were observed. Partial necrosis was detected as well. Our results demonstrate that cytotoxicity of diazene JK-279 is mostly the consequence of caspase-independent cell death, which is in some aspects "apoptosis-like". Taking into account the multiplicity of mechanisms used by cancer cells to prevent apoptosis, the drugs (like diazene JK-279) that would activate alternative cell death pathways could provide a useful tool for new types of cancer therapy.

Diazenes as modificators of drug-resistance in tumor cells.

To overcome the drug resistance, which is the major obstacle in the successful treatment of cancer patients, various compounds have been tested. Glutathione is one of the most promising targets for modulation. In the present study, we examined the influence of five new synthesized compounds--diazenes on the reduction of the intracellular level of GSH. Further, we investigated their ability to increase the cytotoxicity of cisplatin, vincristine and doxorubicin. In experiments human parental cervical (HeLa) and laryngeal (HEp2) carcinoma cells and their drug-resistant cell sublines (HeLaCA and CK2, respectively) were used. Intracellular GSH content was examined spectrophotometrically by the procedure developed by Tietze. The cell sensitivity to drugs was determined using a modified colorimetric MTT assay. Results showed that the rate of reduction of GSH concentration was dependent on the cell type and the type of diazenes. We did not find a correlation between the reduction in GSH level and increased cytotoxicity to selected anticancer drugs. Nevertheless, we found that: a) diazenes LV-35 and VZ-19 increased the cytotoxicity of cisplatin in HEp2 cells, b) diazene MG-19 potentiated the cytotoxicity of vincristine in HEp2 cells, and c) diazene VZ-19 in HeLaCA cells. These data suggest that specific combination of diazene and anticancer drug may be useful in the treatment of certain tumor types.

Diazenes: modificators of tumor cell resistance to cisplatin.

Most studies indicate that modulation of glutathione metabolism may be one of the most promising means of reversing clinical drug resistance. Five new diazene compounds have been synthesized: JK-279, JK-835, JK-913, JK-925 and LV-57 that should, according to their structure and biochemical properties, lower the GSH concentration. In the present study, we examined the influence of diazenes on cisplatin resistance in human cervical (HeLa) and laryngeal carcinoma (HEp2) cells as well as in their cisplatin-resistant sublines (HeLaCA and CK2, respectively). Intracellular GSH content was examined spectrophotometrically by the procedure developed by Tietze. The cell sensitivity to drugs was determined using a modified colorimetric MTT assay. Results show that all examined diazenes lowered GSH concentration. This decrease was insignificant for JK-835 and JK-925 in HeLa and HeLaCA cells, and JK-925 in CK2 cells. In human cervical carcinoma HeLa and HeLaCA cells, JK-279 was mostly active in sensitizing the cells to cisplatin, especially in drug-resistant cells. JK-913, JK-835 and LV-57 reverted partially resistance to cisplatin in HEp2 cells, while none of the diazenes was active in CK2 cells. In conclusion, diazene JK-279 may be useful in the combined treatment (cisplatin + diazene) for the certain type of cancer.

Novel ring contraction of 3-hydroxy-2,4(1H,3H)-quinolinediones in aqueous alkali. The first convenient route to 2-hydroxyindoxyls.

Ring contraction of 3-hydroxy-2,4(1H,3H)-quinolinediones (1) in aqueous potassium hydroxide resulted in the formation of 2-hydroxyindoxyls and/or dioxindoles. The choice of N-substituent and the reaction conditions govern the chemoselectivity of the reaction. N-Phenyl-substituted derivatives 1 give 2-hydroxyindoxyls, while N-alkyl- and N-benzyl-substituted derivatives afford the corresponding dioxindols. On the basis of byproduct analysis, as well as independent experiments, the most plausible reaction mechanism is proposed.

NMR Investigation of the Copper(II)-Ciprofloxacin System.

A proton NMR study was performed on the copper(ll)-ciprofloxacin system. The proton relaxation times (T(1)) were determined from the titration data in acidic and basic media. In acidic medium the H5 signal is dramatically affected and it is assumed that copper is bonded to the quinolone through carbonyl and one of the carboxyl oxygens. Such bonding is in agreement with the X-ray literature data for the complex [Cu(cf)(1)]Cl(2).6H(2)O isolated from the slightly acidic solution. There are additional significant changes in (1)T(1) of H3' and H5' atoms which suggest that the terminal nitrogen atom of the piperazine ring system-N4' also interacts with copper in the basic conditions. Thus it is plausible that more than one species are present in the solution at high pH values.

Diazene JK-279: potential anticancer drug.

The aim of this study was to examine the cytotoxic effect of 10 newly synthesized diazenecarboxamides (diazenes). Using a modified colorimetric MTT assay, their cytotoxicity was determined on 10 human cell lines: cervical carcinoma parental and cisplatin-resistant cells, laryngeal carcinoma parental and cisplatin- and vincristine-resistant cells, glioblastoma parental and cisplatin-resistant cells, breast adenocarcinoma parental and doxorubicin-resistant cells, and mammary carcinoma cells. Results show that diazene JK-279 was most effective, reducing significantly the cell survival of all 10 cell lines examined, including five drug-resistant cell lines. A cytotoxic effect was observed also on nine from 10 cell lines for diazene JK-835. A small reduction in cell survival was obtained (mainly for highest drug concentrations) for diazenes LV-57 and MG-19 on two cell lines, and JK-429 and JK-913 on one cell line. Other diazenes did not demonstrate any cytotoxic activity. The results encourage further research on diazene JK-279 as a potential anticancer drug.