[Circadian behaviour of host versus tumour outcome. A review]

The authors reviewed experimental and clinical data emphasizing the importance for host to keep a reference circadian rythmicity. This assessment seems true both in the cancerogenesis phase, as well in the active phase of tumoural disease.

[Circadian clock gene expression in human peripheral blood mononuclear cells]

Circadian clock genes have been identified in humans but information regarding their expression has remained very limited. However from a basic point as well as in a diagnostic and therapeutic perspective, it is important to evaluate molecular clock gene expression. Peripheral blood mononuclear cells represent an ideal material to investigate non-invasively the human clock at the molecular level. Several studies including ours reported rhythmic expression of clock genes in these cells, with significant intersubject variability of expression. In addition, our results reveal the existence of different chronotypes of clock gene expression patterns and suggest specific regulatory mechanisms in these human cells as compared to other peripheral tissues.

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.

Cross-talks between circadian timing system and cell division cycle determine cancer biology and therapeutics

The circadian clock orchestrates cellular functions over 24 hours, including cell divisions, a process that results from the cell cycle. The circadian clock and cell cycle interact at the level of genes, proteins, and biochemical signals. The disruption or the reinforcement of the host circadian timing system, respectively, accelerates or slows down cancer growth through modifications of host and tumor circadian clocks. Thus, cancer cells not only display mutations of cell cycle genes but also exhibit severe defects in clock gene expression levels or 24-hour patterns, which can in turn favor abnormal proliferation. Most of the experimental research actively ongoing in this field has been driven by the original demonstration that cancer patients with poor circadian rhythms had poor quality of life and poor survival outcome independently of known prognostic factors. Further basic research on the gender dependencies in circadian properties is now warranted, because a large clinical trial has revealed that gender can largely affect the survival outcome of cancer patients on chronotherapeutic delivery. Mathematical models further show that the therapeutic index of chemotherapeutic drugs can be optimized through distinct delivery profiles, depending on the initial host/tumor status and variability in circadian entrainment and/or cell cycle length. Clinical trials and systems-biology approaches in cancer chronotherapeutics raise novel issues to be addressed experimentally in the field of biological clocks. The challenge ahead is to therapeutically harness the circadian timing system to concurrently improve quality of life and down-regulate malignant growth.

Improved Tumor Control through Circadian Clock Induction by Seliciclib, a Cyclin-Dependent Kinase Inhibitor

The circadian timing system and the cell division cycle are frequently deregulated in cancer. The therapeutic relevance of the reciprocal interactions between both biological rhythms was investigated using Seliciclib, a cyclin-dependent kinase (CDK) inhibitor (CDKI). Mice bearing Glasgow osteosarcoma received Seliciclib (300 mg/kg/d orally) or vehicle for 5 days at Zeitgeber time (ZT) 3, 11, or 19. On day 6, tumor mRNA 24-hour expression patterns were determined for clock genes (Per2, Rev-erbalpha, and Bmal1) and clock-controlled cell cycle genes (c-Myc, Wee1, cyclin B1, and CDK1) with quantitative reverse transcription-PCR. Affinity chromatography on immobilized Seliciclib identified CDK1/CDK2 and extracellular signal-regulated kinase (ERK) 1/ERK2, CDK7/CDK9, and casein kinase CK1epsilon as Seliciclib targets, which respectively regulate cell cycle, transcription, and circadian clock in Glasgow osteosarcoma. Seliciclib reduced tumor growth by 55% following dosing at ZT3 or ZT11 and by 35% at ZT19 compared with controls (P < 0.001). Tolerability was also best at ZT3. Mean transcriptional activity of Rev-erbalpha, Per2, and Bmal1 was arrhythmic in the tumors of untreated mice. Seliciclib induced rhythmic clock gene expression patterns with physiologic phase relations only after ZT3 dosing. c-Myc and Wee1 mRNAs displayed synchronous circadian rhythms in the tumors of control mice receiving vehicle only but not in those of mice given the drug. Seliciclib further enhanced Wee1 expression irrespective of dosing time, an effect that reinforced G(2)-M gating. Seliciclib also inhibited CK1epsilon, which determines circadian period length. The coordination of clock gene expression patterns in tumor cells was associated with best antitumor activity of Seliciclib. The circadian clock and its upstream regulators represent relevant targets for CDKIs.

Liver histology and surgical outcomes after preoperative chemotherapy with fluorouracil plus oxaliplatin in colorectal cancer liver metastases

PURPOSE

Preoperative chemotherapy for colorectal liver metastases (CLM) can produce histologic changes in the nontumor-bearing liver (NTBL) that may impact on surgical outcomes.

PATIENTS AND METHODS

From a cohort of 303 patients treated for CLM with liver resection, 92 patients (75 received preoperative chemotherapy: group C+; and 17 were chemotherapy naïve: group C-) were randomly selected for detailed pathologic analysis. Preoperative chemotherapy consisted of fluorouracil (FU)/leucovorin alone (23 patients, the majority chronomodulated) or in combination with oxaliplatin (52 patients, all chronomodulated). To determine associations between study factors, clinical and operative variables were compared with pathology data and surgical outcomes.

RESULTS

Although clinical and operative factors were similarly distributed, C+ patients, compared with C- patients, were more likely to receive intraoperative RBC transfusions (mean units: 1.9 v 0.5, respectively; P = .03) and to have vascular abnormalities in the NTBL (52% v 18%, respectively; P = .01). Presence of the most severe forms of vascular alterations was closely associated with RBC transfusion requirements (P = .04). In contrast, moderate to severe steatosis was similarly distributed (C- group, 12%; C+ group, 13%). Although perioperative mortality and morbidity rates were similar in all groups, more than 12 courses of chemotherapy, compared with < or = 12 courses, predisposed patients to reoperation (11% v 0%, respectively; P = .04) and to longer hospitalization (15 v 11 days, respectively; P = .02).

CONCLUSION

The main hepatic lesion induced by preoperative FU/oxaliplatin chemotherapy in patients with CLM is vascular and not steatosis. Detailed pathologic analysis determined that the most severe vascular lesions are associated with increased intraoperative transfusions. The risk for other postoperative complications is related to the duration of preoperative chemotherapy administration.

Chronotherapeutics: the relevance of timing in cancer therapy

BACKGROUND

Cell physiology is regulated along the 24-h time scale by a circadian timing system composed of molecular clocks within each cell and a central coordination system in the brain. The mammalian molecular clock is made of interconnected molecular loops involving at least 12 circadian genes. The cellular clocks are coordinated by the suprachiasmatic nuclei, a hypothalamic pacemaker which also helps the organism adjust to environmental cycles. The rest-activity rhythm is a reliable marker of the circadian system function in both rodents and man. This circadian organization is responsible for predictable changes in the tolerability and efficacy of anticancer agents, and possibly also in tumor promotion or growth.

METHODS

Expected least toxic times of chemotherapy were extrapolated from experimental models to human subjects with reference to the rest-activity cycle. The clinical relevance of the chronotherapy principle, i.e. treatment administration as a function of rhythms, has been demonstrated in randomized multicenter trials.

RESULTS

Chronotherapeutic schedules have been used to safely document the activity of the association of oxaliplatin, 5-FU and leucovorin against metastatic colorectal cancer and to set up a new medicosurgical management of this disease which achieved unprecedented long term survival.

CONCLUSION

The chronotherapy concept offers further promises for improving current cancer treatment options as well as for optimizing the development of new anticancer or supportive agents.

Circadian expression of clock genes in purified hematopoietic stem cells is developmentally regulated in mouse bone marrow

OBJECTIVE

Clock genes are known to mediate circadian rhythms in the central nervous system and peripheral organs. Although they are expressed in mouse hematopoietic progenitor and stem cells, it is unknown if they are related to circadian rhythms in these cells. We therefore investigated the 24-hour patterns in the activity of several clock genes in the bone marrow (BM) side population (SP) primitive stem cells, and compared these 24-hour patterns to clock gene variations in the whole BM and liver.

METHODS

Cells were obtained from 84 B6D2F(1) mice in three replicate experiments on the second day after release into constant darkness from a standardizing light-dark schedule. mRNA expression of clock genes was measured with quantitative reverse transcriptase polymerase chain reaction.

RESULTS

mPer2 displayed circadian rhythms in SP cells, whole BM, and liver cells. mPer1 and mRev-erb alpha showed a circadian rhythm in whole BM and liver, but not SP cells. mBmal1 was not expressed rhythmically in SP cells, nor in the whole BM, contrary to rhythms observed in the liver.

CONCLUSIONS

With the exception of mPer2, most clock genes studied in primitive hematopoietic SP stem cells were not oscillating in a fully organized circadian manner, which is similar to immature cells in rapidly proliferating organs, such as the testis and thymus. These findings indicate that circadian clock gene expression variations in BM are developmentally regulated.

Phase III trial comparing 4-day chronomodulated therapy versus 2-day conventional delivery of fluorouracil, leucovorin, and oxaliplatin as first-line chemotherapy of metastatic colorectal cancer: the European Organisation for Research and Treatment of Cancer Chronotherapy Group

PURPOSE

In two previous randomized trials, the adjustment of chemotherapy delivery to circadian rhythms improved tolerability and anticancer activity compared with constant-rate infusion during 5 days in patients with metastatic colorectal cancer.

PATIENTS AND METHODS

For this multicenter randomized trial, it was hypothesized that a chronomodulated infusion of fluorouracil, leucovorin, and oxaliplatin for 4 days (chronoFLO4) would improve survival by 10% compared with conventional 2-day delivery of the same drugs (FOLFOX2). Patients were treated every 2 weeks with intrapatient dose escalation.

RESULTS

Baseline characteristics were similar in both arms for the 564 patients (36 institutions, 10 countries). Median survival was 19.6 months (95% confidence limit [CL] = 18.2, 21.2) with chronoFLO4 and 18.7 months with FOLFOX2 (95% CL = 17.7, 21.0; P = .55). The main dose-limiting toxicities were diarrhea for chronoFLO4 and neutropenia for FOLFOX2. The analysis of survival predictors showed that sex was the single most important factor (P = .001). In women, the risk of an earlier death with chronoFLO4 was increased by 38% compared with FOLFOX2, with median survival times of 16.3 and 19.1 months (P = .03), respectively. In men, the risk of death was decreased by 25% with chronoFLO4 compared with FOLFOX2, with median survival times of 21.4 and 18.3 months (P = .02), respectively.

CONCLUSION

Both regimens achieved similar median survival times more than 18 months with an acceptable toxicity. The chronomodulated schedule produced a survival advantage over FOLFOX in men. The strong sex dependency of optimal scheduling of fluorouracil, leucovorin, and oxaliplatin calls for translational investigations of determinants related to the patient's molecular clock.

Optimal circadian time of vinorelbine (V) combined with chronomodulated 5-FU in pretreated metastatic breast cancer patients. EORTC 05971 randomized multicenter study

2066

Background: Chronotherapy is an aim to increase efficacy/toxicity ratio. Objectives: to define the dosing least toxic time (DLTT) of V (30 mg/m2/d at D1 and D6), combined with chrono 5-FU (10 pm-10 am) (850 mg/m2 D2-D5) over 3 courses q3w. Methods: A logistic regression model (LRM) estimated the DLTT assuming a sinusoidal distribution over time (i.e. over the 8 different arms) of the toxicity rate observed in each arm. The associated 90% confidence limits (CL) has been obtained by bootstrap method. Results: 90 patients were recruited. Toxicity in 46 pts led to the V dosage reduction to 25 mg/m2/d. 40 and 43 pts were assigned the V30 and the V25 regimen. 12% pts went off for toxicity, 5% for PD, 1% for refusal, 1% for unrelated death. 224 cycles were analyzed . V and 5FU relative dose intensities were 79.4% and 78.2% in the V30 while 88.1% and 87.4% in the V25 pts. Over the 3 cycles, toxicity by cycle was: Grade (G) 3 and G4 leucopenia in 47% and 29%, G3 and G4 neutropenia in 12% and 77%. G3 febrile neutropenia in 34%. G2 thrombopenia and anemia in 4% each. Other G3 and G 4 toxicity were stomatitis (12%), alopecia (7%), and less than 5%: cardiovascular, lethargy, diarrhea, constipation, other gastrointestinal, infection, sensory, pulmonary. LRM could not demonstrate a DLTT for the neutropenia G3–4 incidence, the primary endpoint. However, based on the stratified by dose analysis, a 90% CI of less than 6 hours width was observed: - around 17H17 [14H04–20H03] for the incidence of leucopenia G3–4. - around 8H16 [06H04–10H39] for tolerability (dose reduction, dose delay or treatment interruption for toxicity reason). This suggests that treatment tolerability was influenced by other factors beside leucopenia nadir. No other 90% CI of less than 6 hours width could be observed for other toxicity endpoints. Conclusions: Using a novel time finding study design with ad hoc statistics, this first randomized multicenter study has determined a DLTT for Vinorelbine in 90 women with MBC. Additional studies are ongoing to further assess the relevance of this trial design method that could prove useful for improving the safety of anticancer drugs during their clinical development. Support Pierre Fabre Oncology, Ligue Bourguignonne contre le Cancer

No significant financial relationships to disclose.

Effective salvage therapy of liver-only colorectal cancer metastases with chronomodulated irinotecan-fluorouracil-oxaliplatin via hepatic artery infusion

3585

Background: Cell cycle and pharmacology genes are controlled by the molecular clock in normal liver but not in tumors (Filipski et al. JNCI 2005). As a result, circadian-based hepatic artery infusions of 3 main active drugs (ChronoHAI) could improve both tolerability and efficacy in patients (pts) with liver metastases from colorectal cancer. Methods: The therapeutic potential of 3-drug chronoHAI was evaluated in 28 heavily pretreated non hospitalized pts with metastatic colorectal cancer (MCC). They received 5-day (d) q21 d courses (c) with d1 irinotecan (160 mg/m2 from 2 to 8 am, peak at 5 am) and d2–5 oxaliplatin (20 mg/m2/d from 10 am to 10 pm, peak at 4 pm) and 5-fluorouracil (600 mg/m2/d from 10 pm to 10 am, peak at 4 am). 149 courses (c) were given (median, 5 ; 1–15) using a multichannel pump (Mélodie, Aguettant, F). Toxicity was assessed q21 d and response q3 c with CT scan. Results: Pt characteristics: prior chemotherapy lines 1/2/3/4+: 3/4/8/13 pts; WHO Performance Status 0/1/2/3 : 12/9/6/1 pts; median age: 63 years (32–73); liver only: 21 pts; liver and lung: 7 pts. Treatment was withdrawn for thrombosis (6 pts) and/or Grade (gr) 3 abdominal pain (3 pts). Grade 3–4 diarrhea and vomiting respectively occurred in 6 pts (21%) and 4 pts (14%) and were the main toxicities. Leucopenia, anemia and thrombocytopenia were respectively encountered in 5, 2 and 1 pt (< 18%). NCIC gr 3 sensory neuropathy occurred in 4 pts and alopecia in 3 pts. Of 25 pts with measurable lesions, disease progressed in 11 pts (exclusively outside the liver for 3 pts) and was controlled in 14 pts (56%), including 8 objective responses - 32% [95% C.L. 13.4 to 50.6]. Partial hepatectomy was performed in 3 pts with measurable disease (12%): R0 (2 PR) and R1 (1 SD). Median Progression free survival is 5 months [2.5 to 7.5] and median survival is 18.4 mo [10.5 to 26.3]. Five pts are alive at 2 to 51 mo. Conclusions: 3-drug chronoHAI is safe in heavily pretreated pts and achieves consistent activity against colorectal cancer liver metastases despite prior failure to oxaliplatin, irinotecan and fluorouracil. The addition of systemic molecular targeted therapy could be useful for preventing extra hepatic dissemination. Supported by ARTBC, Hôpital P. Brousse, Villejuif, France

No significant financial relationships to disclose.

Disruption of Circadian Coordination and Malignant Growth

Altered circadian rhythms predicted for poor survival in patients with metastatic colorectal or breast cancer. An increased incidence of cancers has been reported in flying attendants and in women working predominantly at night. To explore the contribution of circadian structure to tumor growth we ablated the 24-h rest-activity cycle and markedly altered the rhythms in body temperature, serum corticosterone and lymphocyte count in mice by complete stereotaxic destruction of the suprachiasmatic nuclei (SCN) or by subjecting the mice to experimental chronic jet-lag. Such disruption of circadian coordination significantly accelerated malignant growth in two transplantable tumor models, Glasgow osteosarcoma and Pancreatic adenocarcinoma. The mRNA expression of clock genes per2 and reverb-alpha in controls displayed significant circadian rhythms in the liver (Cosinor, p=0.006 and p=0.003, respectively) and in the tumor (p=0.04 and p<0.001, respectively). Both rhythms were suppressed in the liver and in the tumor of jet lagged mice. This functional disturbance of molecular clock resulted in down regulation of p53 and overexpression of c-Myc, two effects which may favor cancer growth.

CONCLUSIONS

These results indicate that circadian system could play an important role in malignant growth control. This should be taken into consideration in cancer prevention and therapy.

Circadian pharmacology of l-alanosine (SDX-102) in mice

L-alanosine (SDX-102) exerts its cytotoxicity through inhibition of de novo purine biosynthesis, an effect potentiated by methylthioadenosine phosphorylase (MTAP) deficiency. The relevance of circadian dosing time was investigated for chronotherapeutic optimization of SDX-102. Toxicity was assessed in healthy mice following single (1,150, 1,650, or 1,850 mg/kg/d) or multiple doses (250 or 270 mg/kg/d). Efficacy was tested in mice with P388 leukemia receiving multiple doses (225 or 250 mg/kg/d). SDX-102 was administered at six circadian times 4 hours apart in mice synchronized with 12 hours of light alternating with 12 hours of darkness. MTAP expression was determined in liver, bone marrow, small intestinal mucosa, and P388 cells. Dosing at 19 hours after light onset reduced lethality 5-fold after single administration and 3-fold after multiple doses as compared with worst time [P < 0.001 and P < 0.01, respectively (chi2 test)]. Neutropenia, lymphopenia, and bone marrow hemorrhagic lesions were significantly less in mice dosed at 19 hours after light onset as compared with 7 hours after light onset. SDX-102 at 7 hours after light onset transiently ablated the 24-hour patterns in body temperature and activity. A circadian rhythm characterized small intestinal MTAP expression with a maximum at 6:30 hours after light onset (P = 0.04). A minor survival improvement was found in MTAP-deficient P388 mice receiving SDX-102 at 7 or 23 hours after light onset as compared with other times (P = 0.03, log-rank test). In conclusion, the therapeutic index of SDX-102 was improved by the delivery of SDX-102 in the mid to late activity span. These results support the concept of chronomodulated infusion of SDX-102 in cancer patients.

The circadian timing system, a coordinator of life processes. implications for the rhythmic delivery of cancer therapeutics

Cell physiology is regulated along the 24-h time scale by a circadian timing system composed of molecular clocks within each cell and a central coordination system in the brain. The mammalian molecular clock is made of interconnected molecular loops involving at least 12 circadian genes. The cellular clocks are coordinated by the suprachiasmatic nucleus, a hypothalamic pacemaker which also helps the organism adjust to environmental cycles. The rest-activity rhythm is a reliable marker of the circadian system function in both rodents and Man. It can be monitored non-invasively through several devices or systems. The circadian organization is responsible for predictable changes in the tolerability and efficacy of anticancer agents, and also controls tumor promotion and growth. The clinical relevance of the chronotherapy principle, i.e. treatment administration as a function of rhythms, has been demonstrated in randomized multicenter trials,using programmable-in-time drug delivery systems. Chronotherapeutic schedules first documented the safety and the activity of oxaliplatin-based combination chemotherapy inpatients with metastatic colorectal cancer. The chronotherapy concept offers further promises for improving current cancer treatment options as well as for optimizing the development of new anticancer or supportive agents. Technological developments of chronotherapeutics in daily practice are essential in order to non invasively assess dynamic changes in biological functions and to insure temporally-adjusted therapeutics interventions.

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.

Atypical patterns of circadian clock gene expression in human peripheral blood mononuclear cells

Circadian ( approximately 24 h) rhythms in physiology and behaviour are observed in all mammals, including humans. These rhythms are generated by circadian clocks located in the hypothalamus and also in most peripheral tissues. Clock genes are essential components of circadian clocks, and mutations or polymorphisms within several of them have been associated with circadian disorders in humans. However, information about human clock gene expression has remained very limited. Peripheral blood mononuclear cells (PBMCs) represent an ideal material to investigate non-invasively the human clock at the molecular level. In the present study, we analysed the expression of three key clock genes, PER2, BMAL1 and REV-ERBalpha in PBMCs from ten healthy humans over a 24-h cycle. PER2 and BMAL1 were found to oscillate throughout the light-dark cycle in all subjects. Interestingly, despite normal melatonin and cortisol secretion patterns, two groups of subjects could be distinguished with significantly different mean PER2 and BMAL1 acrophases. BMAL1 oscillated with approximately the same phase as PER2, instead of being anti-phasic as anticipated from data previously obtained in other peripheral tissues. Furthermore, this unusual phase relationship of PER2 and BMAL1 in human PBMCs was associated with a constant expression of REV-ERBalpha, a crucial regulator of BMAL1, which is highly rhythmic in many other systems. These results reveal the existence of different chronotypes of clock gene expression patterns and suggest specific regulatory mechanisms in human PBMCs.

Preclinical relevance of dosing time for the therapeutic index of gemcitabine-cisplatin

The relevance of gemcitabine timing for chronotherapeutic optimisation was investigated. Healthy mice received multiple doses of gemcitabine (120, 160 or 200 mg kg⁻¹ injection (inj)⁻¹) at one of six circadian times (3, 7, 11, 15, 19 or 23 h after light onset – HALO) on days 1, 4, 7 and 10 or a single dose of gemcitabine (400 mg kg⁻¹) at 11 or 23 HALO±cisplatin (5 mg kg⁻¹ at 1 min, 4 or 8 h later). Mice bearing Glasgow osteosarcoma received multiple doses of gemcitabine (200 mg kg⁻¹ inj⁻¹) at 11 or 23 HALO±cisplatin (5 mg kg⁻¹ inj⁻¹ at 1 min or 4 h later) on days of 10, 13, 16 and 19 following tumour inoculation. A circadian rhythm in body weight loss was statistically validated, with 1030 HALO corresponding to the least toxic time (95% CL, 0800 to 1300). Gemcitabine dosing produced least body weight loss and least neutropenia after injection at 11 vs 23 HALO, whether the drug was given alone or with cisplatin (P=0.001). Gemcitabine–cisplatin tolerability was improved by dosing gemcitabine at 11 HALO and CDDP at 15 HALO (P<0.001). The administration of this schedule to tumour-bearing mice increased median survival three-fold as compared to treatments where both drugs were given simultaneously at 11 or 23 HALO (P=0.02). The optimal schedule would correspond to the delivery of gemcitabine upon awakening and cisplatin near mid-activity in cancer patients.

[Algorithm of determination of circadian gene expression profiles analysed with DNA microarrays]

DNA microarrays allow to simultaneously determine the expression level of thousands of genes. A nycthemeral study must enable to conclude which ones show a circadian rhythm. Two aspects prove this to be quite difficult: firstly, what does "circadian" exactly mean and how to quantify this qualification, and secondly which genes pertain to this definition. Our method, derived from linear optimisation procedures, consists in determining a cost function, depending from magnitudes characterising the notion of circadian rhythm. Given number of genes present on the microarray are known to be expressed rhythmically; their time series are considered as reference series. We have further constructed random series having the same temporal structure as the circadian gene series. We then carried out an optimisation procedure to determine the weighting coefficients in order to obtain a cost function value which orders the time series as follows: the reference series are in the first rows and the random series have low scores. We have tested this method on over 6000 genes expressed in mouse liver. We obtained a circadian gene detection probability of 100% with a false positive rate inferior to 1%.

Chronobiologie et immunité

At all times, cycles have focused men's attention and fashioned his life. Today, thanks to genetic, one can find tracks of circadian rhythms programming until cell's DNA, and this in a very amazing and similar manner from amoebas to mammals. A particular rhythm interests the researcher in oncology: the circadian rhythm of melatonin. It stands at the junction of several domains: somatic, immune and psychic, through the many receptors found on leukocytes, through the links between this hormone production and the one of many cytokines but also with activity, life habits and "stress". On an other hand, antioxydant action of melatonin gives a serious argument concerning its possible role in cancer aetiology. As for them, studies on sleep confirm the large ubiquity of biological cycles, for instance thanks to the observation of the impact of particular genetic mutations on advance or delayed sleep syndrome. Because of the great diversity of cyclic phenomena, the study of chronobiology cannot be undertaken today without a wide interdisciplinary collaboration. During the 13th congress of the "Association Francaise de Chronobiologie Medicale", this study has been continued mainly in three different directions of research: fundamental, applied and transverse. Many original experimental results have been presented and new ways of multidisciplinary research specified. The important scientific fecundity of this very convivial annual congress never lacks to satisfy its participants: it continues to favour the onset of new projects, enabling to avoid major shelves thanks to the constructive criticism of each domain specialists.