Cell killing and kinetic effects of diglycolaldehyde on dividing and nondividing mammalian cells in vitro.

The effects of the anticancer drug diglycolaldehyde (NSC-118994) were studied on Chinese hamster ovary cells growing in vitro. Dividing cells, specifically those in S-phase, were more sensitive to the drug than were nondividing cells, although a large fraction of nondividing cells was also killed by doses up to 800 microgram/ml. Dose-dependent effects on cell progression kinetics were observed in all phases of the cell cycle except in mitosis, during which treated cells progressed at control rates into G1-phase. The inhibition of cell progression from G1- into S-phase (most sensitive phase of the cell cycle) put self-limiting restrictions on the cell killing effects of the drug.

Cell killing, kinetics, and recovery responses induced by 1,2:5,6-dianhydrogalactitol in dividing and nondividiing cells in vitro.

The survival and cell kinetics effect of 1,2:5,6-dianhydrogalactitol, NSC-132313 (galactitol), were studied on mammalian cells. Nondividing or plateau-phase cells were almost two times more sensitive to galactitol than were cells treated in the dividing state (dose required to reduce survival by 63% on the exponential part of the survival curve (DO)=4.2 mug/ml/hr for dividing cells vs. DO=2.4 mug/ml/hr in nondividing cells). The survival curves were characterized as having shoulder regions, followed by exponential decreases in survival as the drug doses were increased above 12 mug/ml for 1 hour. Synchronized mitotic and G1 phase cells were equally sensitive to galacitol, with approximately 90% of the cells killed by 1-hour exposures to 12.5 mug galactitol/ml. Cells in early S phase were the least sensitive to this drug dose (survival greater than 20%); however, the cells became more sensitive as they progressed through the S phase and into the G2 phase. There were no large differences observed in survival sensitivities anywhere in the cell cycle, suggesting that galactitol was not a cell-cycle phase-specific agent. Cells in mitosis or G1 phases of the cell cycle at the time of treatment with galacitol progressed normally into the next stage of the cell cycle; however, cells exposed to galactitol in S or G2 phases exhibited dose-dependent delays in those phases of the cell cycle. Nondividing cells exposed to high doses of galactitol could not recover from potentially lethal damage (PLD); however, nondividing cells exposed to lower galactitol doses (lethal dose to 10% of the cells) did exhibit slight recovery from PLD. Dividing cells did not recover from PLD at any of the doses tested. Both dividing and nondividing cells were more sensitive (cell kill) to galactitol when it was administered in two dose fractions 4-8 hours apart than when the same total integral dose was given as a single exposure. A 25-50% greater cell kill was achieved in nondividing cell populations given two dose fractions versus a single exposure to galactitol. Up to 60% greater cell kill was obtained with fractionalated doses in dividing cell populations. These responses to fractionated dose treatments were also dose-dependent.

Modification of the response to actinomycin D-induced sublethal damage by simultaneous recovery from potentially lethal damage in mammalian cells.

Exponentially growing cells and cells that were allowed to enter a plateau or nondividing state of growth by depleting the medium of growth-essential nutrients were used in these studies. Nondividing Chinese hamster ovary cells in vitro are less sensitive to actinomycin D (AMD) than are exponentially growing cells. The cells were tested for their ability to recover from AMD-induced potentially lethal damage (PLD) or sublethal damage. The proliferating and the nonproliferating cells do not recover from PLD or sublethal damage, and they experience further reductions in survival when they are maintained under the medium conditions of their respective growth states. However, when dividing cells are placed in conditions suboptimal for growth (incubated in depleted plateau medium after treatment with AMD), they did exhibit increased survival. The PLD recovery was so great under these conditions that it masked the true response of the cells to fractionated doses of AMD. When adjustments were made for the PLD recovery, the resulting data indicated a slight but measurable increase in survival. Since AMD inhibits cell progression in all stages of the cell cycle, this increase in survival observed with fractionated doses of AMD may be due to true recovery from sublethal damage, although the movement of cells into less sensitive stages of the cell cycle between treatments cannot be ruled out.