Stable circadian mechanisms of toxicity of two platinum analogs (cisplatin and carboplatin) despite repeated dosages in mice.

The toxicities and tissue uptake of cisplatin (CDDP) and carboplatin (CBDCA) vary largely according to the time of injection of a single dose. Repeated dosages may alter the mechanisms involved with such circadian-dependent toxicity. Weekly i.v. injections of CDDP (5 mg/kg) or CBDCA (50 mg/kg) were given over 2 months to 288 male B6D2F1 mice standardized by an alternation of 12 hr of light and 12 hr of darkness at any one of three circadian dosing times (0, 8 or 16 hr after light onset--HALO). Survival; body weight; complete blood cell counts; histologic lesions in kidney, liver, spleen, bone marrow and intestinal tract; platinum concentration in kidney, spleen and colon were determined every 2 weeks throughout treatment. Thrombocytopenia was 10-fold larger following CBDCA as compared with CDDP. Severe bone marrow necrosis was cumulative following CDDP, but reversible following CBDCA. Leukopenia and bone marrow lesions were, respectively, half as severe following the dosing of either drug at 16 HALO compared with 0 or 8 HALO. Cortical tubular necrosis was observed in CDDP-treated mice. It was cumulative and half as extensive after drug dosing at 16 HALO, as compared with 0 or 8 HALO (P less than or equal to .05). Total Pt accumulation in all three tissues was 3- to 4-fold higher following repeated dosages of CDDP as compared with CBDCA. Tissue Pt uptake was halved after CDDP or CBDCA dosing at 16 HALO as compared with 8 HALO (P less than or equal to .01). Dosing either Pt complex at the appropriate time is even more critical if administrations are to be repeated. Mechanisms appear to involve the circadian rhythm-dependent ability of target tissues to take up the drug.

Circadian rhythm in toxicities and tissue uptake of 1,2-diamminocyclohexane(trans-1)oxalatoplatinum(II) in mice.

Mechanisms involved in the circadian rhythm in murine tolerance for the new platinum analogue, 1,2-diamminocyclohexane(trans-1)oxalatoplatinum(II) (1-OHP) were sought in 404 male C57BL/6 x DBA/2 F1 mice standardized by 12 h light-12 h dark. A potentially lethal dose of 1-OHP (17 mg/kg i.v.) resulted in 76% long-term survival at 15 h after light onset (HALO) (activity span) as compared to 24% after treatment at 7 HALO (rest span) (chi 2 21.3; P less than 0.001). A total of 204 mice received the same dose of 1-OHP at one of three circadian stages (0, 8, or 16 HALO). No renal toxicity was encountered. Bone marrow and jejunal villi constituted the chief targets of 1-OHP toxicity at this dosage and schedule. Hematological tolerance as gauged by leukocyte counts was optimal when the drug was given at 16 HALO (P from analysis of variance, less than 0.001). Jejunal lesions were less severe after 1-OHP dosing at 16 HALO as compared to 8 HALO (P less than 0.001). Total platinum concentrations were determined in 18 tissues 24 h after 1-OHP dosing. The highest levels of platinum were found in the spleen on day 1 as well as on day 5 following 1-OHP treatment. Despite the fact that the highest platinum concentrations in tissues usually corresponded to drug dosing at 8 HALO, no correlation was documented between such variables and tissue toxicity. Tissue pharmacokinetics of 1-OHP contribute only in part if at all to the circadian rhythm in hematological and jejunal toxicity of this drug.

Circadian time dependence of murine tolerance for carboplatin.

A large amplitude circadian rhythm in murine tolerance for the anticancer agent, carboplatin (cyclobutane dicarboxylatoplatinum II, CBDCA) was demonstrated. Two studies were performed in a total of 266 male B6D2F1 mice standardized by LD 12:12. In the first experiment CBDCA (80 mg/kg/day) was administered intravenously (iv) daily for three consecutive days at all six circadian stages (3, 7, 11, 15, 19, or 23 hr after light onset, HALO). CBDCA dosing at 15 HALO resulted in 58% long-term survivors as compared to 0% after treatment at 3 or 23 HALO (chi 2 = 28; p less than 0.001). In the second experiment, CBDCA (72 or 80 mg/kg/day X 3 days, iv) was administered at any of three circadian stages (0, 8, or 16 HALO). Mice were killed, blood was collected, and seven tissues were obtained 5 and 10 days after the first dose, in order to determine serum urea and creatinine concentrations, leukocyte and red blood cell counts, and to evaluate histologic lesions. No renal toxicity was encountered. Bone marrow and colon mucosa were the major target tissues of CBDCA in these dosages and schedules. CBDCA dosing at 16 HALO was least toxic to the bone marrow as assessed by peripheral leukocyte count and histologic score (p from ANOVA less than 0.05). Histologically assessed lesions of the colon mucosa were less severe after CBDCA dosing at 16 HALO as compared to those at 8 HALO, and significantly so for the lowest dosage tested (p approximately 0.05). Uptake of CBDCA 24 hr after the third dose ranged from 23 micrograms/g of dry tissue in the colon to 7 micrograms/g in the duodenum. Mean tissue concentrations increased between Day 4 and Day 10 for the liver and spleen, and remained similar for the kidney. No consistent circadian dependence was found with regard to Day 4 mean Pt uptake in different tissues, whereas the lowest Day 10 Pt concentrations corresponded to CBDCA dosing at 16 HALO for all tissues investigated. Toxicity did not appear to be directly related to the total platinum concentration in these tissues.

Circadian time dependence of murine tolerance for the alkylating agent peptichemio.

Since the extent of host toxicity of cytostatics is considerably affected by dosing time, a chronopharmacologic approach was undertaken for optimizing the therapeutic index of the alkylating agent, peptichemio (PTC). In 4 studies involving a total of 463 male B6D2F1 mice, a highly statistically significant circadian rhythm characterized murine tolerance for PTC (8 or 10 mg/kg/day i.v. X 3 days). Six circadian stages were explored (3, 7, 11, 15, 19 and 23 Hours After Light Onset--HALO). Day-40 survival rate varied between 20% (PTC at 3 HALO) and 55% (PTC at 15 HALO) (chi 2 = 16.7; P less than 0.01). In each study, body weight loss was maximal in mice injected with PTC at 3 HALO and minimal in those treated at 15 HALO (P less than 0.01). In a further study involving 96 male B6D2F1 mice, the toxicity of PTC on several target tissues (bone marrow, spleen, small bowel, colon, liver, kidney and lungs) was investigated by histology and leukocyte count as a function of drug dosing time. A circadian rhythm in the susceptibility of the bone marrow, the spleen and the intestinal tract was demonstrated. Optimal murine tolerance for PTC resulted from dosing it at 15 HALO, e.g. in the first half of the activity span.

Circadian rhythm in tolerance of mice for etoposide.

Etoposide (40 mg/kg/day X 3 days and 60 mg/kg/day X 3 days) was best tolerated by male B6D2F1 mice when given in the second half of the rest span of their sleep-wake circadian cycle. Such a time-qualified treatment resulted in increased long-term survival rate, highest peripheral leukocyte count at nadir, and lowest body weight loss, as compared to results from drug dosing in the activity span. Assuming that such results may be extrapolated to human beings, the treatment time of etoposide associated with an optimal tolerance would be located in the second half of the sleeping span (usually near 5.00 hrs).

Circadian rhythm in tolerance of mice for the new anthracycline analog 4'-O-tetrahydropyranyl-adriamycin (THP).

A statistically significant circadian rhythm in tolerance of 226 male B6D2F1 mice synchronized with LD 12:12 for 4'-O-tetrahydropyranyl-adriamycin (THP) was demonstrated. Four intravenous dosages (18, 25, 32 and 40 mg/kg) and six different dosing times (3, 7, 10, 14, 19 and 23 hr after light onset-HALO) were compared. Survival rate, body weight loss and leukopenia depended on both the dose and time of injection. The overall survival rate varied between 83% (light-rest span) and 56% (dark-activity span) (chi2 = 17; d.f. = 2; P less than 0.001). Maximal body weight loss occurred 4-5 days after drug injection. Total leukocyte counts were determined on these days. Both body weight loss and leukopenia were reduced by approximately 100% in those mice injected in their late rest span (7-10 HALO) as compared to those treated in the middle of their activity span (19 HALO). Circadian rhythms in day-60 survival rate, body weight loss and leukopenia were statistically validated by cosinor analysis, with estimated peak times (acrophases) occurring respectively at 7:30, 9:20 and 8:40 HALO. Minor cardiac lesions consisting of diffuse vacuolization and loss of muscular striation were observed in histologic sections from 3/32 hearts (16 controls, 16 treated). All three corresponded to THP given at 19 (2/2 mice) or 23 HALO (1/4 mice). Thus lethal, hematologic and possibly cardiac tolerance for THP were largely optimized by administering the drug to mice in their late span (7-10 HALO).

A histological assessment of the four-day subrenal capsule assay (SRCA).

A four-day subrenal capsule assay (SRCA) was developed, since fragments of human tumours implanted under the renal capsule of immunocompetent mice became rejected by the host within six days. The assay requires a histological assessment of both its exploitability and the extent of drug-induced anti-tumour lesions. 45 tumours from 43 patients with solid tumour were submitted to an SRCA in 1410 male B6D2F1 mice. After being biopsied each tumour was dissected by a pathologist, cut into 50 pieces (1.5 mm3), and one piece was implanted under the renal capsule of 35 mice; the mean tumour diameter was measured on day 0. The mice were randomized into groups of 6 to 10 animals each. On days 1, 2 and 3, the mice were treated with either placebo (control group) or with various anticancer agents. On day 4 the animals were sacrificed, the mean tumour diameter measured, the tumour bearing kidney fixed in Bouin's picroformol solution and processed for histological analysis after staining with hematein. Fragments of fresh explants of human tumours retained their proliferative and metabolic capacity: mitoses were observed as well as keratinizing cells in epidermoid carcinomas and melanin-producing cells in melanomas. Proliferation of tumour cells was seen along the renal capsule suggesting their affinity for connective tissue. Capillaries filled with mouse erythrocytes were also seen. No or minimal lymphocytic infiltration was found. Drug oncolytic effects ranged from minor cellular degeneration to almost complete necrosis and were documented by the scoring of histologic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)