Caspases promoted DADAG-induced apoptosis in human leukemia HL-60 cells.
(1/6)
AIM: To investigate the roles of caspases in diacetyldianhydrogalactitol (DADAG)-induced apoptosis in human leukemia HL-60 cells. METHODS: Inhibition of proliferation was measured by MTT assay. DADAG-induced apoptosis in HL-60 cells was observed by electron microscopy, flow cytometry, and DNA fragmentation assay. Caspase-3 activity was determined by ApoAlert CPP32 colorimetric assay kit. The cleavage of substrates of caspases was detected by Western blot. RESULTS: DADAG exhibited potent antiproliferative activity and induced apoptosis in HL-60 cells. After treatment with DADAG 8 mg/L for 24 h, caspase-3 activity increased markedly and the cleavage of poly-(ADP-ribose) polymerase (PARP), lamin B, and DFF45 appeared. All of the apoptotic signals were suppressed by z-VAD fmk (a general inhibitor of caspase activities), whereas z-DEVD fmk, a selective inhibitor of caspase-3 activity, only induced partial reversion of the apoptotic effects. CONCLUSION: DADAG induced apoptosis in HL-60 cells by activating caspases. Caspases promoted apoptosis through the cleavage of substrates of PARP, lamin B, and DFF45. (+info)
Loss in cell killing effectiveness of anticancer drugs in human gastric cancer clones due to recovery from potentially lethal damage in vitro.
(2/6)
The ability of human gastric cancer clones to recover from potentially lethal damage was studied. Recovery was greatest following treatments with bleomycin or Adriamycin; the recovery ratios (i.e., survival) increased almost 8-fold during a posttreatment incubation period. Recovery was also possible following treatments with actinomycin D, 1,2:5,6-dianhydrogalactitol, and diaziquone; however, the recovery ratios never increased above 2. No recovery was observed following treatment with 5-fluorouracil. Recovery from potentially lethal damage may be related to the heterogeneity in survival responses observed following treatment with some anticancer drugs. Bleomycin and Adriamycin treatments result in large heterogeneous survival fractions among these human stomach cancer clones, and the potentially lethal damage recovery ratios were larger (and variable). However, actinomycin D, diaziquone, and 1,2:5,6-dianhydrogalacticol produce very uniform killing effects in these cells and the recovery ratios are very much smaller and less variable. Finally the large amount of recovery observed after bleomycin or Adriamycin treatments resulted in the loss of cell killing effectiveness of the agents. Because the survival fractions increased during the recovery period, the net effect on cell killing was reduced to an amount normally obtained with doses that were up to six times smaller. (+info)
Pharmacokinetics of dibromodulcitol in humans: a phase I study.
(3/6)
A combined clinical and pharmacokinetic phase I study of the substituted hexitol dibromodulcitol (DBD), administered as a single oral monthly dose, has been performed. Twenty-three patients with advanced neoplasms received DBD doses ranging from 600 to 1,800 mg/m2 body surface area (BSA). The dose-limiting toxicity was myelosuppression, with both significant granulocytopenia and thrombocytopenia occurring at dose levels of 1,500 to 1,800 mg/m2. The average pharmacokinetic parameters for DBD, calculated on the basis of a one-compartment model with first-order absorption and elimination, include the elimination constant, .005 +/- .002/min; absorption constant, .012 +/- .009/min; and an apparent volume of distribution, 1.03 +/- .4 L/kg. The area under the drug concentration curve (AUC) and the peak drug level (Cmax) were linearly related to the dose administered (P less than .001). The mean AUC was 18.7 +/- 6.1 mmol/L min, and the mean Cmax was 47.1 +/- 16.8 mumol/L when normalized to a DBD dose of 1 gm/m2. The elimination constant was significantly reduced in patients with abnormal hepatic function (P less than .01). The elimination constant was not correlated with renal function. The half-life of DBD in plasma (158 minutes) was considerably shorter than the four-to eight-hour half-life of total radioactivity in plasma measured by previous investigators following the administration of radiolabeled DBD. (+info)
Enhanced cell killing through the use of cell kinetics-directed treatment schedules for two-drug combinations in vitro.
(4/6)
Kinetics-directed drug treatment schedules were tested in Chinese hamster ovary cells. Ten hr after treatment with 1,2:5,6-dianhydrogalactitol (DAG) (at a dose lethal to less than 5% of the cells), a 150% enrichment of cells into the S phase of the cell cycle was observed. This blockade in S phase was reversible and was followed at 18 hr after an exposure to DAG by a 200% increase in the fraction of cells in the G2-M phases of the cell cycle. Bleomycin, known to be most effective against G2 + M cells, had the greatest effect on cell killing when administered at that time. Rapid analysis by flow microfluorometry techniques was used to determine the DAG-induced kinetics changes, thus allowing treatment with the second drugs at the most opportune time. The DAG-induced kinetics changes were also demonstrated in a line of human adenocarcinoma of the stomach in vitro and in Ehrlich ascites tumor cells in vivo. In all cases, the enrichment of cells into S phase was reversible at the doses used and was followed by a reversible blockade in G2-M. (+info)
Use of 1,2:5,6-dianhydrogalactitol in studies on cell kinetics-directed chemotherapy schedules in human tumors in vivo.
(5/6)
Recently, it has been shown that 1,2:5,6-dianhydrogalactitol (DAG) can cause reversible alterations in cell cycle kinetics. Following treatment of CHO cells in vitro and Ehrlich ascites tumor cells in vivo, significant increases in the fraction of cells in S phase were observed to occur, and this was followed by an increase in the fractions of cells in G2 and mitosis. Treatments with S or G2-M phase-specific drugs at the peak enrichment times after DAG was given resulted in greater cell kills than when given by any other schedule. We have extended these kinetics-directed drug schedule studies to human tumors in vivo. The first phase was to determine whether DAG could be used to perturb cell kinetics in vivo as effectively in patients as it was in vitro. In 14 of 17 tumors studied, increases in the S-phase fractions were observed (ranging from 30 to 240% increases). The hr at which the S-phase peaks were observed (post-DAG treatment) was variable among the patients and among the tumors studied. However, this points out the value of obtaining actual cell kinetics data from serially biopsied tumors growing on the body surface and illustrates the importance that these data may have in helping to select an optimal time at which to give an S phase-specific drug. If such tumor cell kinetics-directed scheduling is ultimately shown to be effective, it will represent a means of individualizing therapy for a large fraction of tumor patients whose tumors are growing on or near the surface of the body. The tumors utilized in these studies were squamous carcinomas of the head and neck, skin, anus, and cervix; adenocarcinomas of the breast and rectum; and malignant melanoma. The second phase of this study will be to determine the tumor responses in patients treated with such kinetics-directed schedules. (+info)
Alkylation by 1,2:5,6-dianhydrogalactitol of deoxyribonucleic acid and guanosine.
(6/6)
DNA was alkylated in neutral solution at 37 degrees C with 1,2:5,6-dianhydrogalactitol and hydrolysed to yield two principal products, identified as 7-galactitylguanine and 1,6-dideoxy-1,6-di(guanin-7-yl)galactitol. The reaction products were separated by chromatography on Sephadex G-10 and Dowex 50 (H+ form). The two compounds were also obtained by reaction between dianhydrogalactitol and guanosine in acetic acid. The products were characterized from their u.v.-spectral data by comparison with those of the 7-alkylguanines and were also identified by mass spectrometry. (+info)