Expression of p53 in cisplatin-resistant ovarian cancer cell lines: modulation with the novel platinum analogue (1R, 2R-diaminocyclohexane)(trans-diacetato)(dichloro)-platinum(IV).

The compound (1R,2R-diaminocyclohexane)(transdiacetato)(dichloro)platinum(IV) (DACH-acetato-Pt) is a novel platinum-based antitumor agent with clinical potential against cisplatin-resistant disease that is under development in our laboratory. In view of the central role of the wild-type p53 tumor suppressor gene in drug-induced apoptosis, we evaluated the cytotoxicity of cisplatin and DACH-acetato-Pt in a panel of cisplatin-resistant ovarian tumor models with differing p53 status. Cisplatin was relatively more effective against mutant or null p53 cell lines (continuous drug exposure IC50, 1.2-3.3 microM) than it was against those harboring wild-type p53 (IC50, 2.8-9.9 microM). In contrast, DACH-acetato-Pt was considerably more active in wild-type p53 models (IC50, 0.17-1.5 microM) than it was in mutant or null models (IC50, 2.7-11.3 microM). Inactivation of wild-type p53 function in OVCA-429 cells by the human papillomavirus type 16 (HPV 16) E6 plasmid increased resistance to DACH-acetato-Pt by 3-5-fold, which confirmed the drug's dependence on wild-type p53 for its high cytotoxic potency. Differences between the two platinum agents were also evident in cell cycle studies: cisplatin arrested both wild-type and mutant p53 cells in G2-M, whereas DACH-acetato-Pt arrested wild-type p53 cells in G1 and mutant p53 cells in G2-M. The G1 arrest by DACH-acetato-Pt was abrogated in HPV 16 E6 transfectant clones of OVCA-429 cells. In agreement with effects on cell cycle progression, a 2-h pulse exposure to low concentrations (< or =25 microM) of DACH-acetato-Pt induced marked increases in p53 and p21Waf1/Cip1 expression in OVCA-429 cells. Cisplatin, in direct contrast, had no effect on expression of p53 or p21Waf1/Cip1 until the drug concentration was increased to 125 microM. In HPV 16 E6 transfectants of OVCA-429 cells, induction of p53 by the two agents was severely attenuated, and corresponding increases in p21Waf1/Cip1 were abrogated. This suggests that p21Waf1/Cip1 increases were p53 dependent. Collectively, the results demonstrate that DACH-acetato-Pt is very distinct from cisplatin. In particular, the greater activity of DACH-acetato-Pt in cisplatin-resistant wild-type p53 ovarian tumor models can be ascribed to its ability to more efficiently induce p53 protein and activate p53 functions.

Role of p53 in the ability of 1,2-diaminocyclohexane-diacetato-dichloro-Pt(IV) to circumvent cisplatin resistance.

Several reports indicate that the mechanism of resistance to cisplatin is multifactorial. However, DNA damage tolerance appears to be the more significant mechanism. It is clear that resistance in general is a major clinical concern, and a number of approaches have been taken to circumvent this clinical impediment. One approach is through analog development, and we have identified 1,2-diaminocyclohexane-diacetatodichloro-platinum(IV) as an analog with activity in cisplatin resistance. The activity is greatest against ovarian tumor cell lines where the latent, non-inducible wild-type p53 function can be reactivated by the analog. This functional activation of p53 also corresponds to a reduced threshold for tolerance to DNA damage induced by the analog. Interestingly, cell lines with mutant or null p53 are cross-resistant to the analog. The data indicate that cisplatin resistance due to an increase in DNA damage tolerance can arise through a loss of p53 function, and that functional activation of latent wild-type p53 by the analog facilitates cell death and circumvents this resistance mechanism.

Neonatal outcome following methadone exposure in utero.

To examine the relationship between maternal methadone exposure and neonatal head circumference and abstinence syndrome, we examined the records of 172 opiate-addicted gravidas enrolled in a methadone maintenance program in an urban hospital over a 2-year period. Higher doses of methadone in the third trimester were associated with increased head circumference reflecting both increased gestational duration and improved overall growth. Neonatal withdrawal was positively correlated with gestational age at delivery and race, with nonblack infants exhibiting higher neonatal abstinence scores than blacks following adjustment for maternal dose and gestational age at delivery. Selection of optimal methadone dosage is a complex problem in which the favorable neurobehavioral outcome associated with increased growth and gestational age must be weighed against the risks associated with more severe neonatal withdrawal. Our findings of improved overall fetal growth and gestational duration associated with higher methadone doses suggest that more liberal methadone dosing in pregnancy may improve long-term neonatal outcome.

Teratology studies of compound LY171883 administered orally to rats and rabbits.

The teratogenic potential of the leukotriene antagonist LY171883, a novel antiasthma agent, was investigated in CD rats and Dutch Belted rabbits. Mated female rats were dosed with 0, 10, 65, or 425 mg/kg/day on gestation days 6 through 15 and killed on gestation day 20. Mated female rabbits were dosed with 0, 20, 65, or 200 mg/kg/day on gestation days 6 through 18 and killed on gestation day 28. Maternal toxicity was indicated at 425 mg/kg in rats and 200 mg/kg in rabbits by depressed body weight gain and food consumption. In the rabbit study four abortions occurred at 200 mg/kg, most likely secondarily to maternal toxicity. LY171883 did not cause embryo/fetal toxicity or teratogenicity in rats or rabbits at doses up to and including those that were maternally toxic.