Glutathione content in human bone marrow and circadian stage relation to DNA synthesis

Genotoxicity of cytokines at chemotherapy-induced 'storm' concentrations in a model of the human bone marrow

Donor cell leukaemia (DCL) is a complication of haematopoietic stem cell transplantation where donated cells become malignant within the patient's bone marrow. As DCL predominates as acute myeloid leukaemia, we hypothesized that the cytokine storm following chemotherapy played a role in promoting and supporting leukaemogenesis. Cytokines have also been implicated in genotoxicity; thus, we explored a cell line model of the human bone marrow (BM) to secrete myeloid cytokines following drug treatment and their potential to induce micronuclei. HS-5 human stromal cells were exposed to mitoxantrone (MTX) and chlorambucil (CHL) and, for the first time, were profiled for 80 cytokines using an array. Fifty-four cytokines were detected in untreated cells, of which 24 were upregulated and 10 were downregulated by both drugs. FGF-7 was the lowest cytokine to be detected in both untreated and treated cells. Eleven cytokines not detected at baseline were detected following drug exposure. TNFα, IL6, GM-CSF, G-CSF, and TGFβ1 were selected for micronuclei induction. TK6 cells were exposed to these cytokines in isolation and in paired combinations. Only TNFα and TGFβ1 induced micronuclei at healthy concentrations, but all five cytokines induced micronuclei at storm levels, which was further increased when combined in pairs. Of particular concern was that some combinations induced micronuclei at levels above the mitomycin C positive control; however, most combinations were less than the sum of micronuclei induced following exposure to each cytokine in isolation. These data infer a possible role for cytokines through chemotherapy-induced cytokine storm, in the instigation and support of leukaemogenesis in the BM, and implicate the need to evaluate individuals for variability in cytokine secretion as a potential risk factor for complications such as DCL.

Daytime Dependence of the Activity of the Rat Brain Pyruvate Dehydrogenase Corresponds to the Mitochondrial Sirtuin 3 Level and Acetylation of Brain Proteins, All Regulated by Thiamine Administration Decreasing Phosphorylation of PDHA Ser293

Coupling glycolysis and mitochondrial tricarboxylic acid cycle, pyruvate dehydrogenase (PDH) complex (PDHC) is highly responsive to cellular demands through multiple mechanisms, including PDH phosphorylation. PDHC also produces acetyl-CoA for protein acetylation involved in circadian regulation of metabolism. Thiamine (vitamin B1) diphosphate (ThDP) is known to activate PDH as both coenzyme and inhibitor of the PDH inactivating kinases. Molecular mechanisms integrating the function of thiamine-dependent PDHC into general redox metabolism, underlie physiological fitness of a cell or an organism. Here, we characterize the daytime- and thiamine-dependent changes in the rat brain PDHC function, expression and phosphorylation, assessing their impact on protein acetylation and metabolic regulation. Morning administration of thiamine significantly downregulates both the PDH phosphorylation at Ser293 and SIRT3 protein level, the effects not observed upon the evening administration. This action of thiamine nullifies the daytime-dependent changes in the brain PDHC activity and mitochondrial acetylation, inducing diurnal difference in the cytosolic acetylation and acetylation of total brain proteins. Screening the daytime dependence of central metabolic enzymes and proteins of thiol/disulfide metabolism reveals that thiamine also cancels daily changes in the malate dehydrogenase activity, opposite to those of the PDHC activity. Correlation analysis indicates that thiamine abrogates the strong positive correlation between the total acetylation of the brain proteins and PDHC function. Simultaneously, thiamine heightens interplay between the expression of PDHC components and total acetylation or SIRT2 protein level. These thiamine effects on the brain acetylation system change metabolic impact of acetylation. The changes are exemplified by the thiamine enhancement of the SIRT2 correlations with metabolic enzymes and proteins of thiol-disulfide metabolism. Thus, we show the daytime- and thiamine-dependent changes in the function and phosphorylation of brain PDHC, contributing to regulation of the brain acetylation system and redox metabolism. The daytime-dependent action of thiamine on PDHC and SIRT3 may be of therapeutic significance in correcting perturbed diurnal regulation.

Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential

In this work novel magnetic cationic liposomal nanoformulations were synthesized for the encapsulation of a crystallographically defined ternary V(IV)-curcumin-bipyridine (VCur) complex with proven bioactivity, as potential anticancer agents. The liposomal vesicles were produced via the thin film hydration method employing N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP) and egg phosphatidylcholine lipids and were magnetized through the addition of citric acid surface-modified monodispersed magnetite colloidal magnetic nanoparticles. The obtained nanoformulations were evaluated for their structural and textural properties and shown to have exceptional stability and enhanced solubility in physiological media, demonstrated by the entrapment efficiency and loading capacity results and the in vitro release studies of their cargo. Furthermore, the generated liposomal formulations preserved the superparamagnetic behavior of the employed magnetic core maintaining the physicochemical and morphological requirements for targeted drug delivery applications. The novel nanomaterials were further biologically evaluated for their DNA interaction potential and were found to act as intercalators. The findings suggest that the positively charged magnetic liposomal nanoformulations can generate increased concentration of their cargo at the DNA site, offering a further dimension in the importance of cationic liposomes as nanocarriers of hydrophobic anticancer metal ion complexes for the development of new multifunctional pharmaceutical nanomaterials with enhanced bioavailability and targeted antitumor activity.

Circadian clock manipulation for cancer prevention and control and the relief of cancer symptoms

Life has evolved on this planet with regular daily spans of direct solar energy availability alternating with nocturnal spans of dark. Virtually every earth-borne life form has factored this circadian pattern into its biology to ensure the temporal coordination with its resonating environment, a task essential for its individual survival and that of its species. The first whole genome inspections of mutations in human colon and breast cancer have observed specific retained clock gene mutations. Single nucleotide polymorphisms within the genes of clock, clock-controlled, and melatonin pathways have been found to confer excess cancer risk or protection from cancer. Experimental studies have shown that specific core clock genes (Per2 and Per1) are tumor suppressors because their genetic absence doubles tumor numbers, and decreasing their expression in cancer cells doubles cancer growth rate, whereas their overexpression decreases cancer growth rate and diminishes tumor numbers. Experimental interference with circadian clock function increases cancer growth rate, and clinical circadian disruption is associated with higher cancer incidence, faster cancer progression, and shorter cancer patient survival. Patients with advanced lung cancer suffering greater circadian activity/sleep cycle disruption suffer greater interference with function, greater anxiety and depression, poorer nighttime sleep, greater daytime fatigue, and poorer quality of life than comparable patients who maintain good circadian integration. We must now determine whether strategies known to help synchronize the circadian clocks of normal individuals can do so in advanced cancer patients and whether doing so allows cancer patients to feel better and/or live longer. Several academic laboratories and at least 2 large pharmaceutical firms are screening for small molecules targeting the circadian clock to stabilize its phase and enhance its amplitude and thereby consolidate and coordinate circadian organization, which in turn is likely to help prevent and control human cancer. These drugs and strategies can, in turn, be used to make cancer patients with advanced disease feel and function more normally.

Circadian rhythms: mechanisms and therapeutic implications

The mammalian circadian system is organized in a hierarchical manner in that a central pacemaker in the suprachiasmatic nucleus (SCN) of the brain's hypothalamus synchronizes cellular circadian oscillators in most peripheral body cells. Fasting-feeding cycles accompanying rest-activity rhythms are the major timing cues in the synchronization of many, if not most, peripheral clocks, suggesting that the temporal coordination of metabolism and proliferation is a major task of the mammalian timing system. The inactivation of noxious food components by hepatic, intestinal, and renal detoxification systems is among the metabolic processes regulated in a circadian manner, with the understanding of the involved clock output pathways emerging. The rhythmic control of xenobiotic detoxification provides the molecular basis for the dosing time-dependence of drug toxicities and efficacy. This knowledge can in turn be used in improving or designing chronotherapeutics for the patients who suffer from many of the major human diseases.

Chronomodulated irinotecan, oxaliplatin, and leucovorin-modulated 5-Fluorouracil as ambulatory salvage therapy in patients with irinotecan- and oxaliplatin-resistant metastatic colorectal cancer

PURPOSE

To evaluate the activity and tolerability of salvage chronomodulated chemotherapy combining irinotecan (I), 5-fluorouracil/leucovorin (5-FU/LV), and oxaliplatin (O) (chronoIFLO) in patients with metastatic colorectal cancer (MCRC) and prior progression on four drugs.

PATIENTS AND METHODS

Seventy-seven nonhospitalized MCRC patients received chronoIFLO every 3 weeks, with day 1: I (180 mg/m2 over 6 hours, with peak infusion rate at 05:00) and days 2-5: 5-FU/LV (700/300 mg/m2 per day over 12 hours, with peak flow rate at 04:00), and O (20 mg/m2 per day over 12 hours, with peak flow rate at 16:00). Toxicity and response were assessed every 3 weeks and every 2 months, respectively. RESULTS. Three or more prior chemotherapy lines were given to 75% of the patients. Two or more organs had metastatic disease in 65% of the patients. A median number of six courses of chronoIFLO was given. The main grade 3-4 toxicities were diarrhea (39% of the patients, 9% of the courses) and neutropenia (30% of the patients and 7% of the courses). Grade 3 peripheral sensory neuropathy occurred in 14% of the patients. Two patients achieved a partial response and 61 had stable disease, resulting in disease control for 82% of the patients. The median time to progression (TTP) was 5.5 months (95% confidence interval, 3.7-6.0). The median overall survival time was 14.2 months (9.8-17.3). Baseline performance status, serum carcinoembryonic antigen (CEA) level, and CEA doubling time were independent prognostic factors of TTP.

CONCLUSIONS

ChronoIFLO safely and durably halted tumor progression in most extensively pretreated MCRC patients.

Circadian tempo: A paradigm for genome stability?

Circadian clocks are molecular time-keeping systems that underlie daily biological rhythms in anticipation of the changing light and dark cycles. These clocks mediate daily rhythms in physiology and behavior that are thought to confer an adaptive advantage for organisms. It is hypothesized that cell cycle checkpoints are gated to an intrinsic circadian clock to protect DNA from diurnal exposure to mutagens (e.g.; UV radiation peaks with daylight and dissolved genotoxins that fluctuate with feeding periods). It is proposed that DNA replication arrest in response to genotoxic stress is a likely basis for the evolution of circadian-gated DNA replication. This protective mechanism is highly conserved and can be traced along the evolutionary time-line to the early prokaryotes, unicellular eukaryotes and viruses. Peak DNA repair capacity is normally synchronous to the crest of mutagenic stress as they oscillate with respect to time. Mutator phenotypes with increased vulnerability to genotoxic stress may therefore develop when the circadian pattern of cell cycle control, DNA repair or apoptotic response are phase-shifted relative to the rhythm of mutagenic stress. The accumulating mutations would lead to accelerated aging, genome instability and neoplasia. The proposed model delineates areas of research with potentially profound implications for carcinogenesis.

Circadian rhythm in dihydropyrimidine dehydrogenase activity and reduced glutathione content in peripheral blood of nasopharyngeal carcinoma patients

Dihydropyrimidine dehydrogenase (DPD) is a rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism. Glutathione (GSH) is a tripeptide involved in platinum complex detoxification. This study explored the circadian rhythms of DPD activity and GSH concentration in the peripheral blood of 16 patients with histologically proven nasopharyngeal carcinoma (NPC) in order to guide the establishment of chronotherapeutic schedules for this cancer. DPD activity and GSH concentration were determined by high performance liquid chromatography (HPLC). Both variables displayed significant circadian rhythms (Cosinor analysis: p = 0.009 and 0.012, respectively). Peak DPD activity occurred at about 02:30 h; whereas, peak GSH concentration occurred around 12:40 h. The differences between the peak and nadir mean values were 25.5% and 38.7%, respectively. The study showed that the circadian rhythms in DPD activity and GSH concentration in Chinese NPC are similar to those reported for western patients with colorectal cancer, despite the differences in race and kinds of cancer. These findings imply that the chronotherapeutic schedule of 5-FU and platinum used to treat European colorectal cancer patients probably is applicable to Chinese NPC patients.

Circadian regulation of cell cycle and apoptosis proteins in mouse bone marrow and tumor

Proapoptotic drugs such as docetaxel displayed least toxicity and highest antitumor efficacy following dosing during the circadian rest phase in mice, suggesting that cell cycle and apoptotic processes could be regulated by the circadian clock. In study 1, mouse bone marrow and/or tumor were obtained every 4 h for 24 h in C3H/HeN mice with or without MA13/C mammary adenocarcinoma in order to determine the circadian patterns in cell-cycle phase distribution and BCL-2 anti-apoptotic protein expression. In study 2, mouse bone marrow from B6D2F1 mice was sampled every 3 h for 24 h in order to confirm the BCL-2 rhythm and to study its relation with 24 h changes in the expression of proapoptotic BCL-2-associated X protein (BAX) protein and clock genes mPer2, mBmal1, mClock, and mTim mRNAs. The rhythms in G1-, S- or G2/M-phase cells were shifted in tumor compared with bone marrow. In the tumor, the mean proportion of G2/M-phase cells increased by 75% from late rest to late activity span (P from cosinor = 0.001). No 24 h rhythm was found for BCL-2 in tumors. In contrast to this, in the bone marrow, mean BCL-2 expression varied 2.8-fold in B6D2F1 mice (P=0.025) and 3- or 4.5-fold in tumor-bearing and nontumor-bearing C3H/HeN mice, with a peak during the early rest span (P=0.024 and P<0.001, respectively). BAX varied fivefold during the 24 h span with a major peak occurring near mid-activity (P=0.007). The mean mRNAs of mPer2, mClock, and mBmal1 varied twofold to threefold over the 24 h, with high values during the activity span (P<0.05). In the tumor, the circadian organization in cell-cycle phase distribution was shifted and BCL2 rhythm was ablated. Conversely, a molecular circadian clock likely regulated BCL-2 and BAX expression in the bone marrow, increasing cellular protection against apoptosis during the rest span.

Rhythms in human bone marrow and blood cells

In 24h studies of bone marrow (BM), circadian stage-dependent variations were demonstrated in the proliferative activity of BM cells from subsets of 35 healthy diurnally active men. On an average, the percentage of total BM cells in deoxyribonucleic acid (DNA) synthesis phase was 188% greater at midday than at midnight (circadian rhythm: p = 0.018; acrophase or peak time of 13: 16h). Patients with malignant disease (n = 15) and a normal cortisol circadian rhythm showed higher fractions of BM cells in S-phase at midday. Colony-forming units--granulocyte/macrophage (CFU-GM), an indicator of myeloid progenitor cells, showed the same circadian variation as DNA S-phase (average range of change or ROC = 136%; circadian rhythm: p < 0.001; acrophase of 12:09h). Deoxyribonucleic acid S-phase and CFU-GM in BM both showed a circannual rhythm (p = 0.015 and 0.008) with an identical acrophase of August 12. The daily peak in BM glutathione content, a tripeptide involved in cellular defense against cytotoxic damage, preceded BM proliferative peaks by 4-5 h (ROC = 31-90%; circadian rhythm: p = 0.05; acrophase of 08:30h). Myeloid (ROC = 57%; circadian rhythm: p = 0.056; acrophase at 08:40h) and erythroid (ROC = 26%; circadian rhythm: p = 0.01; acrophase of 13:01h) precursor cells were positively correlated (r = 0.41; p < 0.001), indicating a circadian temporal relationship and equal influence on S-phase of total BM cells. Yield of positive selected CD34+ progenitor stem cells also showed significant circadian variation (ROC = 595%; circadian rhythm: p = 0.02; acrophase of 12:40h). Thus, the temporal synchrony in cell cycling renders BM cells more sensitive at specific times to hematopoietic growth factors and cell cycle-specific cytotoxic drugs. Moreover, proper timing of BM harvesting may improve progenitor cell yield. When using marker rhythms in the blood to allow for individualized timing of BM procedures, the times of low values in white blood corpuscles, neutrophils, and lymphocytes and high values in cortisol were predictive of the times of highest BM erythroid, myeloid, and total S-phase numbers occurring in the following 12 h.

Chronobiology of the mammalian response to ionizing radiation. Potential applications in oncology

Ionizing radiation from all sources under appropriate conditions leads to cell death and tissue damage. It is used in cancer treatment under the assumption of a higher radiosensitivity of the fast dividing tumor cells as compared with adjacent host tissues. The radiosensitivities of proliferating host tissues like bone marrow and gastrointestinal lining epithelium are dose limiting. Since these host tissues and many tumors show circadian and other periodicities in their cell proliferation, the timing of radiation treatment according to host and/or tumor rhythms is expected to improve the toxic/therapeutic ratio of the treatment. The experimental data on the chronobiology of radiation exposure show circadian rhythmicity in radiation response after whole body irradiation in mice and rats with highest toxicity in light-dark 12h:12h synchronized animals during their daily activity span. Bone marrow toxicity as well as gastrointestinal epithelial damage show circadian rhythms in part due to radiation damage to the stem cells involved and especially in the intestine also due to damage to the microvasculature. Chronoradiotherapy of malignant tumors seems promising, alone or in combination with response modifiers, provided the host and potential tumor rhythms can be monitored.

Circadian rhythmicity of whole-blood glutathione in healthy subjects

OBJECTIVES

Physiologic rhythms of antioxidants have been the subject of considerable interest in recent years. Physiologically, it is known that 24-h variability in whole-blood glutathione (GSH) could depend on various factors, such as meal composition, protein dietary content, meal-related hormonal modifications, and stress. Experiments were conducted to determine if the circadian variations previously observed in hepatic concentrations of reduced glutathione in animals also occurred in healthy volunteers.

METHODS

The circadian periodicity of whole-blood glutathione was explored. All parameters were measured enzymatically at 4-h intervals over a 24-h period.

RESULTS

Circadian rhythms were not found. The rhythms peak for glutathione content occurred at 9 h with a small peak at 21 h. The nadir occurred at 17 h and 1 h.

CONCLUSION

These data show that despite this wide distribution of glutathione throughout the day we could not find any significant intertime variability.

Clinical applications of magnetic drug targeting

Cancer patients often present with localized disease. Yet, surgical eradication or radiation treatment is not always possible or meaningful. Site-directed drug targeting is one way of local or regional antitumor treatment. Magnetically controlled drug targeting is one of the various possibilities of drug targeting. This technology is based on binding established anticancer drugs with ferrofluids that concentrate the drug in the area of interest (tumor site) by means of magnetic fields. Then, the drug desorbs from the ferrofluid and enfolds its mechanism of action. This paper gives the reader an overview of current applications of ferrofluids (magnetic liquids) in conjunction with magnetic fields as they relate to the latest advances in medical applications and in particular to anticancer treatment.

Circadian variation of cell proliferation and cell cycle protein expression in man: clinical implications

Most physiological, biochemical and behavioural processes have been shown to vary in a regular and predictable periodic manner with respect to time. This review focuses on the circadian rhythm in cell proliferation in bone marrow and gut and how this is associated with a circadian expression of cell cycle proteins in human oral mucosa. The control of circadian rhythms by the suprachiasmatic nuclei and the evolving understanding of the genetic and molecular biology of the circadian clock is outlined. Finally, the potential clinical impact of chronobiology in cancer medicine is discussed.

Circadian rhythm of cell division

The existence of circadian oscillations in the level of hormones, in numerous physiological parameters, in toxicity and in behavior is now fully recognized in all living organisms. In contrast, the synchronisation and regulation of cell proliferation by circadian rhythms in vivo is only starting to be appreciated. This article reviews the experimental evidence for circadian synchronisation of cell division in different mammalian tissues (mainly the gastro-intestinal tract and hemapoietic system), including tumoral tissues. The possible causes of this coupling of the cell cycle phases to the circadian rhythm are discussed. Testing of novel antitumour agents using murine models should take into consideration the temporal difference between murine and human circadian control of proliferation (the peak of DNA synthesis occurs during the activity period, i.e. during daytime in man, and at night-time in mice and rats). Experimental and clinical data clearly support the important implications of the circadian control of the cell cycle in the optimisation of cancer chemotherapy, both for reducing toxicity and increasing the antitumour effects.

Glutathione in human plasma: decline in association with aging, age-related macular degeneration, and diabetes

Blood samples were analyzed for GSH and GSH redox state in 40 age-related macular degeneration (ARMD) patients (> 60 y), 33 non-ARMD diabetic patients (> 60 years), 27 similarly aged non-ARMD and nondiabetic individuals (> 60 years), and 19 younger individuals (< 60 years) without ARMD or diabetes. Results showed a significantly lower plasma GSH in older individuals (ARMD, diabetes, and controls) than in younger individuals (p < .01). Total GSH (GSHt) obtained following treatment with dithiothreitol was significantly lower only in diabetic cases (p < .05) but also approached significance for ARMD cases (p = .089). Estimation of redox potential indicated that the plasma GSH pool is considerably more oxidized in all of the older groups. Analyses of whole blood GSH showed that GSH was significantly lower in diabetic cases compared to the other groups, but did not reveal any difference associated with age or ARMD. In contrast, GSSG in whole blood was significantly higher in the older groups compared to the younger controls. The results suggest that in studies of age-related pathologies, oxidation of GSH may be a more important parameter than a decline in pool size, while in specific pathologies such as diabetes, both oxidation and a decline in pool size may be important.

Pharmacologic modulation of reduced glutathione circadian rhythms with buthionine sulfoximine: relationship with cisplatin toxicity in mice

The relationship between the rhythm in reduced glutathione (GSH) and that in cisplatin (CDDP) toxicity was investigated in a total of 560 male B6D2F1 mice, using buthionine sulfoximine (BSO). GSH was measured by high-performance liquid chromatography (HPLC) in four tissues, at each of six sampling times, 4 hr apart. A significant 24-hr rhythm was statistically validated in liver, jejunum, and colon, but not in bone marrow. Relative to liver, glutathione content was 56% in colon, 38% in bone marrow, 25% in jejunum, and negligible in kidney, where cysteine, a final product of GSH catabolism, displayed a 12-hr rhythmic variation. This rhythm may reflect that in the activity of GSH-degrading enzymes. BSO (450 mg/kg ip, 4 hr before sampling) reduced liver GSH threefold and kidney cysteine content was halved, but this pretreatment had no significant effect upon GSH content in the other organs. Furthermore, the period of the physiologic liver GSH rhythm changed from 24 hr to a composite (24 + 12 hr) period. This change in the period may result from an unmasking of the 12-hr rhythm in GSH-degrading enzyme activity by GSH synthesis blockade. Maximal values occurred in the mid-rest span and in the mid-active span after BSO administration. In the other tissues, the 24-hr period remained unchanged. BSO injection largely enhanced CDDP toxicity (as assessed by survival, leukopenia, and histologic lesions in kidney and bone marrow) and kidney mean platinum concentration. Furthermore, BSO pretreatment modified the period of CDDP toxicity rhythm: survival followed a significant 12-hr-rhythm, instead of a 24-hr rhythm. The cycling of GSH concentration results from a balance between synthesis and catabolism and likely constitutes one of the main components of the circadian rhythm in CDDP toxicity in mice.

Circadian rhythms and cancer chemotherapy

Experimental and clinical pertinent data regarding circadian rhythmicities are reviewed in (1) target tissues, i.e., healthy tissues (actively proliferating or not) and tumor tissues, (2) pharmacology of anticancer agents, (3) toxicity and tolerance of these agents and (4) antitumor activity of cancer chemotherapy. The basic concepts of chronotolerance and/or of chronoefficacy have brought new hopes for further amelioration in the management of cancer patients. Quite recent published Phase II and III clinical trials have demonstrated that new improvements on the therapeutic index have been achieved through ambulatory chronotherapy for various solid tumors.

Chronobiology. Implications for cancer chemotherapy

Experimental studies have documented that both the toxicity and the antitumor activity of many cancer drugs are time dependent. Early clinical trials have confirmed this observation for several drugs. The basic concepts of chronobiology and its application to pharmacology are reviewed. As an example, clinical trials of circadian fluoropyrimidine delivery are reviewed. Other clinical results are presented in table form. The mechanisms pertinent to the circadian time dependence of fluoropyrimidines are discussed.

The time of administration of 3'-azido-3'-deoxythymidine (AZT) determines its host toxicity with possible relevance to AZT chemotherapy

3'-Azido-3'-deoxythymidine (AZT) is the drug most widely used in the treatment of AIDS. Its major drug-related toxicity is bone marrow suppression, which limits the dose of AZT that can be used. It is essential that AZT be phosphorylated for antiviral effect. We have recently demonstrated that thymidine kinase (TK), the initial enzyme in AZT anabolism, follows a circadian pattern in rat bone marrow. The present study was undertaken to determine whether AZT toxicity is related to the time of its administration and whether the variation in toxicity is correlated with the circadian variation in TK activity. Male Sprague-Dawley rats were housed under standardized conditions of light and dark (lights on 0600 to 1800 and lights off 1800 to 0600) for 4 weeks. The animals were randomly divided into seven groups; six groups were administered AZT by intraperitoneal injection at the same dose of 750 mg/kg of body weight at various times (0400, 0800, 1200, 1600, 2000, and 2400), and one group was used as a control. AZT-related toxic effects, including bone marrow toxicity, differed significantly among the treatment groups, depending on the time of AZT administration (by analysis of variance and Cosinor analysis, P < 0.001). The least toxicity was observed in rats receiving AZT at 1600 (10 h after light onset [10 HALO], in late sleep span) and the greatest toxicity was observed in those injected at 0400 (22 HALO, in late activity span). To verify these results, we administered AZT by intraperitoneal injection at an approximately 50% lethal dose (1,500 mg/kg) to two groups of rats, one at 1200 (6 HALO, in the middle of the sleep span) and the other at 2400 (18 HALO, in the middle of the activity span). AZT lethality was significantly higher in rats receiving AZT at 2400 (18 HALO, in the middle of the activity span). Further statistical analysis demonstrated that the variation in AZT toxicity was correlated with the circadian variation in TK activity in bone marrow of the same species (peak activity at 0400 [22 HALO, in late activity span] and trough activity at 1600 [10 HALO, in late sleep span]), suggesting that the circadian variation in TK activity may be the biochemical basis for the observed circadian variation in AZT toxicity. These results may be useful in the design of improved AZT chemotherapeutic regimens.

Proliferation patterns in acute myeloid leukemia: leukemic clonogenic growth and in vivo cell cycle kinetics

In a prospective study of 33 newly diagnosed patients with acute myeloid leukemia (AML), we analyzed the relationship of proliferation parameters with clinical parameters, response to induction therapy, and survival. The median follow-up was 26 months. The proliferative capacity of the leukemic progenitor cells was studied using colony-forming assays (number of colony-forming units, growth pattern, and spontaneous clonogenic growth capacity). The cell kinetic parameters of the bone marrow blasts were determined by in vivo labeling with iododeoxyuridine and subsequent flow cytometry: labeling index (LI), DNA synthesis time (Ts), potential doubling time. No or only weak relationships were observed between the experimental and clinical parameters such as age, sex, % blasts, white blood cell count, FAB subtype, cytogenetics, and % CD 34+ cells. This suggests that clonogenic growth and cell cycle kinetics of bone marrow blasts are independent cell biologic properties of AML. No association between the proliferation parameters and induction response rate was noticed. Analysis of the overall survival and event-free survival revealed trends to longer survival rates in patients with a below-median LI (< or = 7.6%) and below-median Ts value (< or = 14.3 h). These trends were more pronounced in the group of de novo AML (n = 23), where the prolonged event-free survival in patients with below-median Ts reached statistical significance (p = 0.02). None of the other parameters appeared significantly correlated with survival, although there was a trend to longer survival rates in patients who had no spontaneous clonogenic growth capacity (p = 0.13). In conclusion, proliferation parameters in leukemic cells provide additional information on the cell biologic characteristics of AML, and these parameters may have prognostic value for response and duration of survival in AML.

DNA cell cycle distribution and glutathione (GSH) content according to circadian stage in bone marrow of cancer patients

DNA cell cycle distribution and glutathione (GSH) content in bone marrow were measured both at daytime and midnight over single 24 h periods in 15 cancer patients. Between patients the S-phase demonstrated a difference from lowest to highest value of 700%, whereas the corresponding difference for the G2/M-phase was nearly 900%. The mean GSH content measured in the bone marrow at the two timepoints was 2.24 +/- 0.21 nmol mg-1 protein, range 0.91-4.19 nmol mg-1 protein. A statistically significant higher fraction of cells in S-phase and G2/M-phase was found at daytime as compared to midnight when excluding the four patients with an abnormal circadian variation in cortisol. No significant temporal variation in total bone marrow GSH content was found, although a weak correlation between S-phase and GSH content was demonstrated (r = 0.42; P less than 0.05). This correlation was strengthened when not including the six patients with an abnormal cortisol pattern (4) and bone marrow infiltration (2) (r = 0.66; P = 0.005). Cells in S-phase demonstrated a positive correlation with cells in G2/M-phase (r = 0.64; P less than 0.0001). A negative correlation was found between GSH content and age (r = 0.53; P less than 0.005). Finally, a statistically significant positive correlation was demonstrated between cortisol and both S-phase and G2/M-phase (r = 0.57; P less than 0.001 and r = 0.38; P less than 0.05, respectively). The present study suggests a possibility of optimising cancer therapy and use of hematopoietic growth factors by determining individual average values and circadian stage dependent variation in bone marrow DNA cell cycle distribution. Furthermore, GSH content in bone marrow may predict this tissue's sensitivity to cytotoxic agents.

Aging and cancer: plasma antioxidants and lipid peroxidation in young and aged breast cancer patients

The relationship between aging and cancer is complex because the intrication takes place at the cell, the organism and the environment levels. On the other hand, carcinogenesis is a multi-step process, and different mechanisms may be involved in each step. For example, oxidants and antioxidants may play a different role depending upon the phase considered. Tumors in older patients are generally described as slow growing. The difference in tumor aggressiveness between young and older patients is especially obvious in breast cancer patients. The age specificity of some breast risk factors suggests that breast cancer which has been diagnosed in an aged woman was induced late in her life. We address the question whether the characteristics of a senescent organism with regards to oxidant-antioxidant status could be causally related to the slow evolution of tumors in old patients.