Sex moderates circadian chemotherapy effects on survival of patients with metastatic colorectal cancer: a meta-analysis.

BACKGROUND: Molecular circadian clocks can modify cancer chemotherapy effects, with a possible moderation according to sex differences. We investigated whether sex determine the optimal delivery schedule of chemotherapy for metastatic colorectal cancer. PATIENTS AND METHODS: A meta-analysis was performed using individual data from three international Phase III trials comparing 5-fluorouracil, leucovorin and oxaliplatin administered in chronomodulated (chronoFLO) or conventional (CONV) infusions. The data from 345 females and 497 males were updated at 9 years. The main end point was survival. RESULTS: Overall survival was improved in males on chronoFLO when compared with CONV (P = 0.009), with respective median values of 20.8 (95% CL, 18.7 to 22.9) and 17.5 months (16.1 to 18.8). Conversely, median survival was 16.6 months (13.9 to 19.3) on chronoFLO and 18.4 months (16.6 to 20.2) on CONV in females (P = 0.012). The sex versus schedule interaction was a strong predictive factor of optimal treatment schedule, with a hazard ratio of 1.59 (1.30 to 1.75) for overall survival (P = 0.002) in multivariate analysis. CONCLUSIONS: Males lived significantly longer on chronomodulated chemotherapy rather than on conventional chemotherapy. The current chronoFLO schedule deserves prospective assessment as a safe and more effective first-line treatment option than conventional delivery for male patients.

High-dose definitive concomitant chemoradiotherapy in non-metastatic locally advanced esophageal cancer: toxicity and outcome.

This study is a retrospective analysis of high-dose definitive concomitant chemoradiotherapy in locally advanced esophageal cancer in a single institution. The aim of the study was to identify and quantify the toxicity associated with the high-dose treatment and to analyze the outcome of this treatment. Forty-six patients (41 men and 5 women, median age of 67.5 years) with disease stage IIA-III esophageal cancer were treated with high-dose definitive chemoradiotherapy. Thirty patients had squamous cell carcinomas and 16 had adenocarcinomas. The patients were treated with three courses of chemotherapy. Each chemotherapy course consisted of cisplatin 100 mg/m(2), day 1 and 5-Fluorouracil 1000 mg/m(2)/day, day 1-5. One course was given every 3 weeks. Concurrent radiotherapy (66 Gy/33 fractions) was administered during the last two courses of chemotherapy. Toxicity grades three and four were seen in 47.5% and 40% of the patients, respectively. Treatment related mortality occurred in one patient (2.5%) due to neutropenic septicemia. Follow-up time for surviving patients (2/46) was 45 and 112 months. For the entire study population, the median time to local recurrence in the radiotherapy field was 33 months and the median time to distant metastasis was 8.7 months, whereas median overall survival was 10.8 months and median disease-specific survival 11 months. For responders to chemoradiotherapy, the median time to local recurrence was 76 months, the median time to distant metastasis 16.8 months, the median overall survival and the median disease-specific survival for the responders were both 17 months. The 2, 3 and 5-year survival rates were 22%, 15% and 11% for the entire study population, and 31%, 24% and 17% for the responders to chemoradiotherapy, respectively. By multivariate analysis response to chemoradiotherapy and lower disease stage were positive prognostic factors for survival. The results of our study have shown that concurrent high-dose chemoradiotherapy provides long-term local tumor control in locally advanced esophageal cancer. However, toxicities following this high-dose treatment, while manageable, were significant. Survival rates were not improved by high-dose chemoradiotherapy compared with what is reported in previous studies applying lower doses of definitive chemoradiotherapy.

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

DNA synthesis and contents of reduced glutathione (GSH) and oxidized glutathione were determined every 4 hours during a 24-hour period in 70 human bone marrow samples from 10 healthy males. The mean GSH contents during the sampling periods were low, varying from 1.94 to 3.27 nmol/mg protein between the subjects; the mean values for all samples were 2.54 +/- 0.06 nmol/mg protein. The GSH content varied markedly within the individual according to circadian stage (31.0% to 90.2%; mean, 51.4%). Between individuals the mean percentage of cells in DNA synthesis varied from 10.6% to 14.5%, but there was an intraindividual circadian stage-dependent variation, ranging from 48.9% to 274.0% (mean, 126.6%), relative to the lowest value. After adjustment for a slight phase difference between GSH content and DNA synthesis observed for some of the subjects, a statistically significant correlation was found between the GSH content and the fraction of cells in DNA synthesis. The myelosuppressive effect of many chemotherapeutic agents assumed to be detoxified by GSH-dependent mechanism(s) should be considered in the light of the low GSH content in human bone marrow, the circadian variation of DNA synthesis, and the circadian stage-dependent relationship of the GSH content and DNA synthesis.

DNA synthesis and ploidy in non-Hodgkin's lymphomas demonstrate intrapatient variation depending on circadian stage of cell sampling.

Significant circadian cell cycle variations with a maximal number of cells in S-phase during the night have been found in a series of 24 patients (18 men and 6 women) with histologically established non-Hodgkin's lymphomas. Pathological lymph nodes of a total of 26 patients were punctured and aspirated by fine needle technique every 4 h during a single 24-h time span. Twenty-four patients (92.3%) had Stage III or IV disease. Twelve patients (46.1%) had low grade, 10 patients (38.5%) had intermediate grade, and 4 patients (15.4%) had high grade lymphomas according to the Working Formulation. The samples were analyzed by flow cytometry, and DNA synthesis (S-phase) and ploidy were determined according to circadian stage. The individual mean 24-h S-phase varied from 2.2 +/- 1.2% (mean +/- SD) to 24.0 +/- 3.3%. Within the group of patients with low grade lymphomas, a wide range in mean S-phase from 2.4 +/- 1.2% to 9.2 +/- 2.8% was observed. The percentage variation within each patient between the lowest and highest S-phase as compared to the lowest value (range of change) during the 24-h time span varied from 21 to 353%, with a mean range of change of 128 +/- 19%. When each individual S-phase series was converted to percent of mean and combined for analysis by one-way analysis of variance to test for time-effect across 2 12-h time spans (8 p.m.-8 a.m. versus 8 a.m.-8 p.m.), S-phase variation according to circadian stage was found to be statistically significant (P < 0.004), with higher values found in the 8 p.m.-8 a.m. time span. By single cosinor analysis, S-phase yielded a near significant P value of 0.069 for the least-squares fit of a 24-h cosine to all data as percent of mean, with the acrophase found to be near midnight (0.05 h). For those patients with low and intermediate grade lymphomas and with mean S-phase values < 10.0%, we found that mean S-phase was higher during winter (5.8 +/- 0.4%) than during spring (3.8 +/- 0.3%) or during fall (3.6 +/- 0.3%) (P < 0.001, analysis of variance). Twenty-one of the 26 patients (80.8%) had an aneuploid, hypodiploid, or near diploid population in one or several of the repeated samples. For the whole series, the DNA indices for the aneuploid populations varied from 1.09 to 1.96, the median DNA index being 1.20.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in folate status as determined by reduction in total plasma homocysteine levels during leucovorin modulation of 5-fluorouracil therapy in cancer patients.

We measured plasma total homocysteine (tHcy) in 14 patients (13 patients with colorectal cancer and 1 patient with breast cancer) during their first treatment with 5-fluorouracil (5-FU) plus leucovorin [LV (5-FULV)]. Eight of these patients were investigated a second time after 3-10 cycles (median, 4 cycles) with 5-FULV. Each cycle consisted of two administrations of 5-FU (500 mg/m2) and LV (60 mg/m2) given 24 h apart. The first administration of 5-FULV on day 1 of the first cycle induced a rapid reduction of the tHcy level from 12.5 micromol/liter (10.4-15.1 micromol/liter; geometric mean with 95% confidence interval of the mean) to 9.1 micromol/liter (7.5-11.1 micromol/liter) in 24 h. tHcy remained stable at this level after the second administration of 5-FULV. In addition, the 5-FULV regimen caused a concurrent 4-fold increase in both serum and erythrocyte folate. The fifth cycle with 5-FULV had only marginal effects on the tHcy level. 5-FU without LV modulation had no effect on the plasma tHcy or folate status in eight breast cancer patients. Our data establish the reduction of tHcy as a responsive indicator of LV pharmacodynamics.

Partially wedged beams improve radiotherapy treatment of urinary bladder cancer.

BACKGROUND AND PURPOSE: Partially wedged beams (PWBs) having wedge in one part of the field only, can be shaped using dynamic jaw intensity modulation. The possible clinical benefit of PWBs was tested in treatment plans for muscle-infiltrating bladder cancer. MATERIAL AND METHODS: Three-dimensional treatment plans for 25 bladder cancer patients were analyzed. The originally prescribed standard conformal four-field box technique, which includes the use of lateral ordinary wedge beams, was compared to a modified conformal treatment using customized lateral PWBs. In these modified treatment plans, only the anterior parts of the two lateral beams had a wedge. To analyze the potential clinical benefit of treatment with PWBs, treatment plans were scored and compared using both physical parameters and biological dose response models. One tumour control probability model and two normal tissue complication probability (NTCP) models were applied. Different parameters for normal tissue radiation tolerance presented in the literature were used. RESULTS: By PWBs the dose homogeneity throughout the target volume was improved for all patients, reducing the average relative standard deviation of the target dose distribution from 2.3 to 1.8%. A consistent reduction in the maximum doses to surrounding normal tissue volumes was also found. The most notable improvement was demonstrated in the rectum where the volume receiving more than the prescribed tumour dose was halved. Treatment with PWBs would permit a target dose escalation of 2-6 Gy in several of the patients analyzed, without increasing the overall risk for complications. The number of patients suitable for dose escalation ranged from 3 to 15, depending on whether support from all or only one of the five applied NTCP model/parameter combinations were required in each case to recommend dose escalation. CONCLUSION: PWBs represent a simple dose conformation tool that may allow radiation dose escalation in the treatment of muscle-infiltrating urinary bladder tumours.

Cytometry and time-dependent variations in peripheral blood and bone marrow cells: a literature review and relevance to the chronotherapy of cancer.

By flow cytometry of individual cells, multiple cell properties can be analyzed. Such parameters may be important in relation to cytotoxic treatment of cancer. For example, DNA measurements will answer questions regarding cell kinetics. Myelosuppression is the major dose-limiting toxicity during cancer treatment. Therefore, the study of cell cycle parameters in bone marrow cells is highly relevant. However, inattention to the existence and potential importance of biological rhythms may introduce artifacts and misleading results. The literature of rhythms in hematology is reviewed. Time-dependent variations in hematological variables have been extensively studied and rhythms have been described for all kinds of blood cells. Also the numbers of hemopoietic stem cells in the bone marrow undergo circadian variations. Our group has shown how such variations change with aging in mice. The relevance of time sequence studies in aging research of hemopoiesis was clearly demonstrated. In animal studies using cytometry, our group has demonstrated extensive circadian variations in cell cycle distribution of bone marrow cells, especially the DNA synthesis (S-phase). In humans a few and rather small time sequence studies of the bone marrow have been performed, so far. In this overview the clinical implications of circadian rhythms of S-phase variations measured by flow cytometry of human bone marrow cells are discussed. Male volunteers were examined every 4 h around-the-clock. The data indicated a lower proliferative activity during night, suggesting the possibility of reducing the bone marrow toxicity to cancer treatment when taking these time-dependent variations into consideration.

Circadian cell kinetics in humans. Aspects related to cancer chemotherapy.

A prerequisite for the investigation of cell kinetics, and especially circadian cell kinetics, has been the development from the 1950s and onwards of several methods for studying kinetic parameters in different mammalian tissues. A large number of such studies have subsequently taken place in the rodent, mostly as non-circadian experiments, but also a large number of studies have now documented on circadian proliferative rhythms in many different murine tissues. Results from cytokinetic studies in the human have also accumulated through the years. Of special interest has been the demonstration of temporal variations in rapidly proliferating tissues studies as the bone marrow and gut mucosa relative to cytotoxic anticancer therapy. Analyses of proliferation in human tumours have also indicated rhythms in malignant solid tumours. Thus, these studies have demonstrated that there exist rhythms in bone marrow and gut cytokinetics which increases the likelihood that certain times of day will be less toxic for the administration of cytotoxic drugs. Furthermore, optimizing anticancer therapy according to a circadian schedule may also increase the tumour cell death rat, due both to an indirect dose-escalating effect and a direct increased tumour effect.

Circadian phase relationships between peripheral blood variables and bone marrow proliferative activity in clinical health.

Potential life-threatening drug induced side effects to the bone marrow (BM) may be reduced by the proper timing of chemotherapy (chronotherapy) according to circadian stage. Blood and BM samples were obtained concomitantly every 4h for 24h from 16 healthy men (19 series total) to compare circadian patterns in peripheral blood (PB) as reference rhythms for BM DNA. Circadian rhythm characteristics from population mean cosinor summary follow (phi = acrophase): in PB: cortisol, p = 0.014, phi = 13:04h; leukocytes (/mm3), p = 0.001, phi = 00:16h; neutrophils (%WBC), p = 0.001, phi = 15:36h; neutrophils (/mm3), p = 0.101, phi = 22:36h; lymphocytes (%WBC), p = 0.009, phi = 03:24h; lymphocytes (/mm3), p = 0.001, phi = 0.1:40h; in BM:DNA, p = 0.014, phi = 13:04h; and CFU-GM, p = 0.041, phi = 13:12h. When all DNA synthesis (S-phase) values were correlated with PB values by repeatedly advancing the DNA values by 4h, significant correlations with cortisol were found by advancing S-phase by 8h (r = 0.19, p = 0.050). Lymphocytes correlated best with S-phase when shifted by 12h (r = 0.37, p < 0.001), while neutrophils as % of leukocytes (but not absolute counts) correlated significantly when S-phase was delayed by 4h (r = 0.35, p < 0.001). These correlations confirm the phase relationships determined for the circadian rhythms. These findings suggest that the proper timing of an optimized anticancer cytotoxic chronotherapy can be confirmed and guided via sampling of marker rhythms (such as lymphocytes) in peripheral blood which have been found to demonstrate a relatively fixed relation to the circadian stage-dependent variation in unaffected BM proliferative activity.

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.

Circadian and infradian aspects of the cell cycle: from past to future.

A review of some aspects of circadian and infradian rhythms of the cell cycle is given. The background is that the research of the last decade has given entirely new insights into the cell cycle as a dynamic process which occurs in waves. After some short historical notes on the development of methodology for study of cell kinetics, it is reviewed how the strong variability of this function was recognized from the 1960's. This again led to an increasing understanding of the rhythmic pattern of cell renewal in various tissues of the body. Conventional methods for studying cell population kinetics gave general insights into both circadian and infradian rhythms, but were hampered by several shortcomings. The techniques were time consuming, and usually one and only one parameter could be studied at a time. However, this general knowledge both had a strong impact on the understanding of cell kinetics and provided a basis for designing cancer chemotherapy. Today we are facing a new area in the study of cell population kinetics. New, rapid and automated methods for multiparameter studies of both cell kinetics and other biological properties of cell populations have given entirely new possibilities for cell kinetic research. Methods, mainly connected to analytical cytology, can discriminate subpopulations with varying kinetic properties, and also enable monitoring of cell proliferation in normal and malignant tissues of patients. Chronobiology has had a strong impact on the understanding of cell population kinetics in the body. In the light of the new developments in the fields of growth factors and their regulatory influences on the cell cycle, important and fundamental aspects of biological rhythms are now being elucidated.

Circannual rhythm in DNA synthesis (S-phase) in healthy human bone marrow and rectal mucosa.

Cytotoxic anti-cancer drugs are meant to interact with tumor cells to impair the replicative and/or transcriptional functions of DNA in order to reduce proliferative rate and cause cell death. These drugs also affect rapidly proliferating healthy tissues such as the bone marrow and the gastrointestinal tract, thereby resulting in toxicity-related dose reductions and/or delays in treatment. We previously demonstrated a circadian rhythm in DNA synthesis (S-phase) of total bone marrow (BM) nucleated cells in 16 healthy, diurnally active men sampled every 4 h for 24 h (19 series). Highest values determined by flow cytometry were found near midday. We also reported a circadian rhythm in DNA synthesis of the rectal mucosa (RM) in 16 healthy men sampled every 2-3 h for 24 h under fed and fasting conditions (24 series). Highest proliferative activity as reflected by in vitro [3H]Tdr uptake, was found near the time of awakening. Circannual (about yearly) rhythmicity in cell division rates may also influence treatment effects. Our BM and RM DNA data, which were collected over several years, were reanalyzed for seasonality by ANOVA and for circannual rhythm by the least-squares fit of a 1 year cosine. Characteristics of circadian amplitudes and acrophases were also compared between seasons. In addition to a significant circadian rhythm, a significant circannual rhythm in cell proliferation in healthy BM (P = 0.008) and RM (P < 0.001) could be established on the basis of these serially independent data. The range between the lowest and highest points of the fitted 1 year cosine (circannual double amplitude) was comparable to the circadian range for BM (25%); it was at least doubled for RM (70%). Highest values occurred in the late summer for BM and mid-fall for RM. Based on limited data in some seasons, the circadian patterns were more prominent in the fall and winter, with larger amplitudes and later acrophases, when compared with summer for BM and spring and summer for RM. Thus, in addition to time of day, time of year may influence chemo- and immunotherapeutic strategies and should be considered in the design of preclinical and clinical treatment regimens and other procedures.

Current concepts for chronochemotherapy of cancer.

In this article, a survey on the concepts and scientific basis for applying chemotherapy against malignant tumors on a circadian schedule is given. The idea is to give the cytostatic drugs at times of the day when optimal effect on the tumor is achieved, but at the same time causing minimal toxic side effects. Following a brief description of the complexity of cancer tissue, some aspects of the present status of cancer chemotherapy in general are reviewed. Applications of chronobiology in cancer treatment are then surveyed together with possibilities to increase cytostatic doses and reduce side effects. When optimal tumor cell kill is achieved, the next step is to address the circadian aspects of normal organs, including the proliferative behavior of tissues with rapid cell renewal. Finally, the question of how regulatory mechanisms responsible for normal circadian rhythms can be interfered with is addressed. Cancer chronochemotherapy today combined with modern infusional technology is a promising field for improving cancer treatment in general and reducing side effects and is expected to make important progress in the near future.

Circadian variation in serum cortisol and circulating neutrophils are markers for circadian variation of bone marrow proliferation in cancer patients.

Serum cortisol, circulating white blood cells and DNA cell cycle distribution in bone marrow cells were measured during daytime (11.00) and at midnight (24.00) over single 24-hour periods in 15 cancer patients. The neutrophils and fraction of bone marrow cells in S-phase showed the same circadian variation as cortisol with higher values in daytime as compared to midnight in 11 patients with a normal cortisol rhythm (p < 0.05). The lymphocytes, eosinophils and basophils all had significantly higher values at midnight as compared to daytime. There were significant correlations between cortisol and neutrophils, lymphocytes, eosinophils and basophils. The correlation between neutrophils and fractions of bone marrow cells in S-phase and S + G2/M-phase were highly significant (r = 0.74, p = 0.0001 and r = 0.72, p = 0.0001, respectively). In 8 of 13 patients (61.5%) without bone marrow infiltration both cortisol and neutrophils showed identical circadian variation as bone marrow cells in S-phase and S + G2/M-phase. Furthermore, for the total series a significant correlation between S-phase, cortisol and neutrophils was found by multiple regression analysis (p < 0.0001). These findings strengthen the possibility of using the circadian variation in cortisol and neutrophils as marker rhythms for circadian variation in bone marrow proliferation, thus allowing optimization of cytotoxic therapy and individualization of chronotherapy.

Radical radiation treatment of invasive and locally advanced bladder carcinoma in elderly patients.

A total of 146 patients with invasive or locally advanced carcinoma of the bladder (T2-T4) underwent radiation treatment. A significantly higher complete response rate was observed with doses equal to or above 55 Gy and with doses corresponding to cumulative radiation effect (CRE) values of 1700 radiation effect units (reu) or more. In multivariate analysis, decreasing time from the first diagnosis of bladder carcinoma to radiation treatment and 1 or more transurethral resections was associated with a significant increase in survival; increases in T category and sedimentation rate were negative prognostic factors. Although both radiation dose and CRE levels had a significant effect on survival in univariate analysis, an increase in CRE levels alone was associated with a significant increase in survival in multivariate analysis. However, the most important predictor of survival was whether the patient showed a complete local response or not. This study emphasises the importance of treating patients with an adequate radiation dose over a short period of time in order to achieve the maximum radiobiological effect and thereby increase the possibility of cure.

DNA synthesis in human bone marrow is circadian stage dependent.

Fraction of human bone marrow (BM) cells in DNA synthesis has been studied by sampling BM from the sternum or the iliac crests every 4 hours during one 24-hour period in 16 healthy male volunteers. Three of the subjects underwent the sampling procedure twice, resulting in 19 24-hour profiles. The percentage of cells in DNA synthesis measured by flow cytometry demonstrated a large variation along the circadian time scale for each 24-hour profile, with a range of variation from 29% to 339% from lowest to highest value. Seventeen profiles (89.5%) had the highest DNA synthesis during waking hours between 08:00 hours and 20:00 hours, and the lowest percentage of cells in DNA synthesis between 00:00 hours and 04:00 hours. The mean value of the lowest DNA synthesis for each 19 24-hour period was 8.7% +/- 0.6%, while the mean value of the highest DNA synthesis was 17.6% +/- 0.6%, ie, a twofold difference. There was no difference in DNA synthesis between winter and summer. A significantly higher DNA synthesis was demonstrated for samples obtained from sternum as compared with the iliac crests, but the same circadian pattern was demonstrated for both localizations. By taking circadian stage-dependent variations in DNA synthesis into account it may be possible to reduce BM sensitivity to cytotoxic chemotherapy, to increase the effect of hematopoietic growth factors as well as increase the fraction of proliferating cells with careful selection of time of day for harvesting BM cells for auto- or allografting.

Colony-forming unit-granulocyte-macrophage and DNA synthesis of human bone marrow are circadian stage-dependent and show covariation.

Bone marrow samples from sternum and iliac crests were harvested every 4 hours during 19 24-hour periods from 16 healthy male volunteers, and myeloid progenitor cells were cultured by the colony-forming unit-granulocyte-macrophage (CFU-GM) assay. A large interindividual variation was observed in the mean number of colonies during each 24-hour period, with the highest 24-hour mean colony number being about 600% greater than the lowest (range: 16 +/- 2.3 to 100.3 +/- 4.5). For each individual the difference between the lowest and highest colony number throughout the day ranged from 47.4% to 256.3% of the mean colony number of each series. A circadian stage-dependent variation in the number of colony-forming units of myeloid progenitor cells (CFU-GM) of human bone marrow was demonstrated, with values 150% higher, on the average, during the day as compared with the night. The overall data (891 CFU-GM replicates) exhibited a significant 24-hour rhythm (P less than .001) with an acrophase at midday (12.09 hours with 95% confidence limits from 10.32 to 13.49 hours) and a trough at midnight. This 24-hour variation was found to covary with DNA synthesis in the total proliferating bone marrow cell population. A seasonal effect on CFU-GM numbers was detected by ANOVA (P = .014) and by the least squares fit of a 1-year cosine (P = .015), with the highest number found in summer. The potential relevance of these findings should be examined in relation to cytotoxic cancer therapy, use of hematopoietic growth factors, and bone marrow transplantation.

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.

Methylthioadenosine phosphorylase in human breast cancer.

Methylthioadenosine (MTA) phosphorylase activity was measured in 47 biopsies from primary breast cancers (n = 34) and metastatic tumors (n = 13). Most specimens were also evaluated by DNA flow cytometry and determination of estrogen and progesterone receptor contents. Median MTA phosphorylase activity was 317 pmol/mg protein/min (range 50-1312 pmol/mg protein/min), but great variations were observed. Samples from four individuals had very low MTA phosphorylase activity (less than or equal to 70 pmol/mg protein/min). No correlation with aneuploidy, receptor status, or the presence of metastases in the lymph nodes could be demonstrated. However, MTA phosphorylase activity showed a significant (p = 0.009) negative correlation with the fraction of cells in the S-phase of the cell cycle.