Sex and dosing-time dependencies in irinotecan-induced circadian disruption

Circadian disruption accelerates malignant growth; thus, it should be avoided in anticancer therapy. The circadian disruptive effects of irinotecan, a topoisomerase I inhibitor, was investigated according to dosing time and sex. In previous work, irinotecan achieved best tolerability following dosing at zeitgeber time (ZT) 11 in male and ZT15 in female mice, whereas worst toxicity corresponded to treatment at ZT23 and ZT3 in male and female mice, respectively. Here, irinotecan (50 mg/kg intravenous [i.v.]) was delivered at the sex-specific optimal or worst circadian timing in male and female B6D2F1 mice. Circadian disruption was assessed with rest-activity, body temperature, plasma corticosterone, and liver mRNA expressions of clock genes Rev-erbα, Per2, and Bmal1. Baseline circadian rhythms in rest-activity, body temperature, and plasma corticosterone were more prominent in females as compared to males. Severe circadian disruption was documented for all physiology and molecular clock endpoints in female mice treated at the ZT of worst tolerability. Conversely, irinotecan administration at the ZT of best tolerability induced slight alteration of circadian physiology and clock-gene expression patterns in female mice. In male mice, irinotecan produced moderate alterations of circadian physiology and clock-gene expression patterns, irrespective of treatment ZT. However, the average expression of Rev-erbα, Per2, and Bmal1 were down-regulated 2- to 10-fold with irinotecan at the worst ZT, while being minimally or unaffected at the best ZT, irrespective of sex. Corticosterone secretion increased acutely within 2 h with a sex-specific response pattern, resulting in a ZT-dependent phase-advance or -delay in both sex. The mRNA expressions of irinotecan clock-controlled metabolism genes Ce2, Ugt1a1, and Top1 were unchanged or down-regulated according to irinotecan timing and sex. This study shows that the circadian timing system represents an important toxicity target of irinotecan in female mice, where circadian disruption persists after wrongly timed treatment. As a result, the mechanisms underling cancer chronotherapeutics are expectedly more susceptible to disruption in females as compared to males. Thus, the optimal circadian timing of chemotherapy requires precise determination according to sex, and should involve the noninvasive monitoring of circadian biomarkers.

Strain- and sex-dependent circadian changes in abcc2 transporter expression: implications for irinotecan chronotolerance in mouse ileum

Background

ATP-binding cassette transporter abcc2 is involved in the cellular efflux of irinotecan. The drug is toxic for mouse ileum, where abcc2 is highly expressed. Here, we investigate whether circadian changes in local abcc2 expression participate in the circadian rhythm of irinotecan toxicity for ileum mucosa, and further assess whether genetic background or sex modify this relation.

Methodology/Principal Findings

Ileum mucosa was obtained every 3–4 h for 24 h in male and female B6D2F₁ and B6CBAF₁ mice synchronized with light from Zeitgeber Time (ZT)0 to ZT12 alternating with 12 h of darkness. Irinotecan (50 mg/kg i.v. daily for 4 days) was administered at the sex- and strain-specific times corresponding to least (ZT11-15) or largest drug-induced body weight loss (ZT23-03-07). Abcc2 expression was determined with qRT-PCR for mRNA and with immunohistochemistry and confocal microscopy for protein. Histopathologic lesions were graded in ileum tissues obtained 2, 4 or 6 days after treatment. Two- to six-fold circadian changes were demonstrated for mRNA and protein mean expressions of abcc2 in mouse ileum (p<0.05). ZT12 corresponded to high mRNA and protein expressions, with circadian waveforms differing according to genetic background and sex. The proportion of mice spared from ileum lesions varied three-fold according to irinotecan timing, with best tolerability at ZT11-15 (p = 0.00003). Irinotecan was also best tolerated in males (p = 0.05) and in B6CBAF₁ (p = 0.0006).

Conclusions/Significance

Strain- and sex-dependent circadian patterns in abcc2 expressions displayed robust relations with the chronotolerance of ileum mucosa for irinotecan. This finding has strong potential implications for improving the intestinal tolerability of anticancer drugs through circadian delivery.

Impact of bevacizumab on functional recovery and histology of the liver after resection of colorectal metastases

BACKGROUND

The impact of bevacizumab on functional recovery and histology of the liver was evaluated in patients undergoing hepatic resection for colorectal liver metastases (CLM) following bevacizumab treatment.

METHODS

Consecutive patients who had resection of CLM between July 2005 and July 2009 following preoperative chemotherapy were identified retrospectively from a prospectively collected database. Patients who had received bevacizumab before the last chemotherapy line were excluded. Postoperative liver function and histology were compared between patients with and without bevacizumab treatment. Recorded parameters included serum prothrombin time, total bilirubin concentration, and levels of aspartate and alanine aminotransferase and γ-glutamyltransferase.

RESULTS

Of 208 patients identified, 67 had received last-line bevacizumab, 44 were excluded and 97 had not received bevacizumab. Most patients in the bevacizumab group (66 per cent) received a single line of chemotherapy. Bevacizumab was most often combined with 5-flurouracil/leucovorin and irinotecan (68 per cent). The median number of bevacizumab cycles was 8·6 (range 1-34). Bevacizumab administration was stopped a median of 8 (range 3-19) weeks before surgery. There were no deaths. Postoperative morbidity occurred in 43 and 36 per cent of patients in the bevacizumab and no-bevacizumab groups respectively (P = 0·353). The mean(s.d.) degree of tumour necrosis was significantly higher in the bevacizumab group (55(27) versus 32(29) per cent; P = 0·001). Complete pathological response rates were comparable (3 versus 8 per cent; P = 0·307). Postoperative changes in functional parameters and objective signs of hepatic toxicity were similar in both groups.

CONCLUSION

Preoperative administration of bevacizumab does not seem to affect functional recovery of the liver after resection of CLM. Tumour necrosis is increased following bevacizumab treatment.

Skin surface temperature rhythms as potential circadian biomarkers for personalized chronotherapeutics in cancer patients

Chronotherapeutics involve the administration of treatments according to circadian rhythms. Circadian timing of anti-cancer medications has been shown to improve treatment tolerability up to fivefold and double efficacy in experimental and clinical studies. However, the physiological and the molecular components of the circadian timing system (CTS), as well as gender, critically affect the success of a standardized chronotherapeutic schedule. In addition, a wrongly timed therapy or an excessive drug dose disrupts the CTS. Therefore, a non-invasive approach to accurately detect and monitor circadian rhythms is needed for a dynamic assessment of the CTS in order to personalize chronomodulated drug delivery schedule in cancer patients. Since core body temperature is a robust circadian biomarker, we recorded temperature at multiple locations on the skin of the upper chest and back of controls and cancer patients continuously. Variability in the circadian phase existed among patch locations in individual subjects over the course of 2-6 days, demonstrating the need to monitor multiple skin temperature locations to determine the precise circadian phase. Additionally, we observed that locations identified by infrared imaging as relatively cool had the largest 24 h temperature variations. Disruptions in skin temperature rhythms during treatment were found, pointing to the need to continually assess circadian timing and personalize chronotherapeutic schedules.

An automaton model for the cell cycle

WE CONSIDER AN AUTOMATON MODEL THAT PROGRESSES SPONTANEOUSLY THROUGH THE FOUR SUCCESSIVE PHASES OF THE CELL CYCLE: G1, S (DNA replication), G2 and M (mitosis). Each phase is characterized by a mean duration τ and a variability V. As soon as the prescribed duration of a given phase has passed, the transition to the next phase of the cell cycle occurs. The time at which the transition takes place varies in a random manner according to a distribution of durations of the cell cycle phases. Upon completion of the M phase, the cell divides into two cells, which immediately enter a new cycle in G1. The duration of each phase is reinitialized for the two newborn cells. At each time step in any phase of the cycle, the cell has a certain probability to be marked for exiting the cycle and dying at the nearest G1/S or G2/M transition. To allow for homeostasis, which corresponds to maintenance of the total cell number, we assume that cell death counterbalances cell replication at mitosis. In studying the dynamics of this automaton model, we examine the effect of factors such as the mean durations of the cell cycle phases and their variability, the type of distribution of the durations, the number of cells, the regulation of the cell population size and the independence of steady-state proportions of cells in each phase with respect to initial conditions. We apply the stochastic automaton model for the cell cycle to the progressive desynchronization of cell populations and to their entrainment by the circadian clock. A simple deterministic model leads to the same steady-state proportions of cells in the four phases of the cell cycle.

Feasibility of cetuximab given with a simplified schedule every 2 weeks in advanced colorectal cancer: a multicenter, retrospective analysis

Cetuximab was approved using a weekly schedule, alone or in combination with chemotherapy (CT). However, many CT regimens in metastatic colorectal cancer (CRC) are delivered every 2 weeks (q2wks). Preliminary data suggested that a simplified schedule using cetuximab q2wks, 500 mg/m² would be equivalent to the standard weekly administration. Medical data of all patients with advanced CRC who received cetuximab q2wks were retrospectively collected and checked for consistency by an independent monitor in 4 European centers. Ninety-one patients were treated between 2005 and 2007 when the K-RAS mutational status of tumors was not determined routinely. They received a median of 4 (0-5) previous drugs, including previous weekly cetuximab in 38.5% of patients. Cetuximab q2wks was associated with an irinotecan-based regimen in 85.7% of patients. The median number of cetuximab administrations was 6 (1-23). Skin toxicity was observed in 68.2% of evaluable patients (grade 3 in 15%). Only one grade 1 allergy was reported. In the 84 patients beyond first-line therapy, response rate was 29.3%. The median progression-free survival was 3.0 months (range 2.2-3.8), and median overall survival was 9.0 months (range 6.2-11.8). Cetuximab q2wks appears safe and effective in heavily pretreated patients and convenient in combination with q2wks CT schedules.

Regenerative nodular hyperplasia of the liver related to chemotherapy: impact on outcome of liver surgery for colorectal metastases

Background

Regenerative nodular hyperplasia (RNH) represents the end-stage of vascular lesions of the liver induced by chemotherapy. The goal was to evaluate its incidence and impact on the outcome of patients resected for colorectal liver metastases (CLM).

Methods

Patients who underwent hepatectomy for CLM after six cycles or more of first-line chemotherapy, between January 1990 and November 2006, were included. Detailed histopathologic analysis of the nontumoral liver was performed according to a standard format.

Results

From a cohort of 856 resected patients at our institution, 771 (90%) received preoperative chemotherapy. Of these, 146 fulfilled the selection criteria and were included: 24 (16%) received 5-fluorouracil (5-FU) and leucovorin (LV) alone, 92 (63%) had 5-FU/LV and oxaliplatin, 18 (12%) had 5-FU/LV and irinotecan, and 12 (8%) were treated by 5-FU/LV, oxaliplatin, and irinotecan. RNH occurred in 22 of 146 patients (15%). Twenty of these patients (91%) received oxaliplatin, of whom six (30%) had chronomodulated therapy. Patients treated by oxaliplatin more often had RNH compared with oxaliplatin-naïve patients (22 vs. 4%). Although operative mortality was nil, the presence of RNH was associated with increased postoperative hepatic morbidity (50 vs. 29%). Elevated preoperative gamma-glutamyltransferase (GGT) (>80 U/L; >1N) and total bilirubin levels (>15 μmol/L; >1N) were independent predictors of RNH.

Conclusions

Patients with CLM who receive preoperative oxaliplatin have an increased risk of RNH and associated postoperative morbidity. Increased serum GGT and bilirubin are useful markers to predict the presence of RNH.

Cancer inhibition through circadian reprogramming of tumor transcriptome with meal timing

Circadian disruption accelerates cancer progression, whereas circadian reinforcement could halt it. Mice with P03 pancreatic adenocarcinoma (n = 77) were synchronized and fed ad libitum (AL) or with meal timing (MT) from Zeitgeber time (ZT) 2 to ZT6 with normal or fat diet. Tumor gene expression profiling was determined with DNA microarrays at endogenous circadian time (CT) 4 and CT16. Circadian mRNA expression patterns were determined for clock genes Rev-erbalpha, Per2, and Bmal1, cellular stress genes Hspa8 and Cirbp, and cyclin A2 gene Ccna2 in liver and tumor. The 24-hour patterns in telemetered rest-activity and body temperature and plasma corticosterone and insulin-like growth factor-I (IGF-I) were assessed. We showed that MT inhibited cancer growth by approximately 40% as compared with AL (P = 0.011) irrespective of calorie intake. Clock gene transcription remained arrhythmic in tumors irrespective of feeding schedule or diet. Yet, MT upregulated or downregulated the expression of 423 tumor genes, according to CT. Moreover, 36 genes involved in cellular stress, cell cycle, and metabolism were upregulated at one CT and downregulated 12 h apart. MT induced >10-fold circadian expression of Hspa8, Cirbp, and Ccna2 in tumors. Corticosterone or IGF-I patterns played no role in tumor growth inhibition. In contrast, MT consistently doubled the circadian amplitude of body temperature. Peak and trough respectively corresponded to peak expressions of Hspa8 and Cirbp in tumors. The reinforcement of the host circadian timing system with MT induced 24-hour rhythmic expression of critical genes in clock-deficient tumors, which translated into cancer growth inhibition. Targeting circadian clocks represents a novel potential challenge for cancer therapeutics.

Cetuximab and circadian chronomodulated chemotherapy as salvage treatment for metastatic colorectal cancer (mCRC): safety, efficacy and improved secondary surgical resectability

BACKGROUND

Circadian rhythm disruption was linked to high serum levels of Transforming Growth Factor Receptor α, an Epidermal Growth Factor Receptor (EGFR) ligand and poor survival in patients with metastatic colorectal cancer (mCRC). We hypothesized that EGFR blockade with cetuximab would enhance the activity of chronotherapy as a result of improved circadian coordination.

METHODS

All the patients with mCRC referred to our unit for progression on prior chemotherapy over a 30-month-period received weekly cetuximab and fortnightly chronotherapy.

RESULTS

Fifty-six patients were treated with a median of six courses of fluoropyrimidine-based chemotherapy and irinotecan (61%), oxaliplatin (25%) or both (14%) after a median of three prior regimens. We found no EFGR amplification by FISH in the tumor of 27 consecutive patients. Acneiform rash and diarrhea were the most common toxicities. Objective response rate was 32.1% and positively correlated with rash grade (p = 0.025). None of the responders had K-Ras mutation in their tumor. Median progression-free and overall survival were 4.6 and 13.7 months, respectively. Complete macroscopic resections of metastases in liver, lung or other abdominopelvic sites were performed following tumor downstaging by the treatment regimen in 11 patients (21%), 8 of whom being alive at 3 years. These figures are twice as high as those reported for first-line combination of cetuximab with conventional chemotherapy or for third line chronotherapy.

CONCLUSIONS

The addition of cetuximab to chronotherapy allowed safe and effective therapeutic control of metastases, including their complete resection, despite previous failure of several treatment regimens.

Tumor growth rate determines the timing of optimal chronomodulated treatment schedules

In host and cancer tissues, drug metabolism and susceptibility to drugs vary in a circadian (24 h) manner. In particular, the efficacy of a cell cycle specific (CCS) cytotoxic agent is affected by the daily modulation of cell cycle activity in the target tissues. Anti-cancer chronotherapy, in which treatments are administered at a particular time each day, aims at exploiting these biological rhythms to reduce toxicity and improve efficacy of the treatment. The circadian status, which is the timing of physiological and behavioral activity relative to daily environmental cues, largely determines the best timing of treatments. However, the influence of variations in tumor kinetics has not been considered in determining appropriate treatment schedules. We used a simple model for cell populations under chronomodulated treatment to identify which biological parameters are important for the successful design of a chronotherapy strategy. We show that the duration of the phase of the cell cycle targeted by the treatment and the cell proliferation rate are crucial in determining the best times to administer CCS drugs. Thus, optimal treatment times depend not only on the circadian status of the patient but also on the cell cycle kinetics of the tumor. Then, we developed a theoretical analysis of treatment outcome (TATO) to relate the circadian status and cell cycle kinetic parameters to the treatment outcomes. We show that the best and the worst CCS drug administration schedules are those with 24 h intervals, implying that 24 h chronomodulated treatments can be ineffective or even harmful if administered at wrong circadian times. We show that for certain tumors, administration times at intervals different from 24 h may reduce these risks without compromising overall efficacy.

Chronotherapy of cancers aims at exploiting daily physiological rhythms to improve anti-cancer efficacy and tolerance to drugs by administering treatments at a specific time of the day. Recent clinical trials have shown that chronotherapy can be beneficial in improving quality of life and median life span in patients, but that it can also have negative effects if the timing is wrong. A theoretical basis for the rational development of individualized therapy schedules is still lacking. Here, we use a simple cell population model to show how biological rhythms and the cell cycle interact to modulate the response to cancer therapy. In particular, we show that the proliferation rate of cancer cells determines when treatments are most effective. We provide a simple formulation of the problem that can be used to compute an objective response function based on the drug sensitivity and the proliferation rate of tumor cells. Finally, we show that in some cases, treating at a different time every day may be more appropriate than standard daily chronotherapy. These results constitute an important step in designing individualized chronotherapy treatments, and point out to ways to design better clinical trials.

Circadian Timing in Cancer Treatments

The circadian timing system is composed of molecular clocks, which drive 24-h changes in xenobiotic metabolism and detoxification, cell cycle events, DNA repair, apoptosis, and angiogenesis. The cellular circadian clocks are coordinated by endogenous physiological rhythms, so that they tick in synchrony in the host tissues that can be damaged by anticancer agents. As a result, circadian timing can modify 2- to 10-fold the tolerability of anticancer medications in experimental models and in cancer patients. Improved efficacy is also seen when drugs are given near their respective times of best tolerability, due to (a) inherently poor circadian entrainment of tumors and (b) persistent circadian entrainment of healthy tissues. Conversely, host clocks are disrupted whenever anticancer drugs are administered at their most toxic time. On the other hand, circadian disruption accelerates experimental and clinical cancer processes. Gender, circadian physiology, clock genes, and cell cycle critically affect outcome on cancer chronotherapeutics. Mathematical and systems biology approaches currently develop and integrate theoretical, experimental, and technological tools in order to further optimize and personalize the circadian administration of cancer treatments.

Tumor marker evolution: comparison with imaging for assessment of response to chemotherapy in patients with colorectal liver metastases

Background

As the real clinical significance of carcinoembryonic antigen (CEA) and carbohydrate antigen 19.9 (CA19.9) evolution during preoperative chemotherapy for colorectal liver metastases (CLM) is still unknown, we explored the correlation between biological and radiological response to chemotherapy, and their comparative impact on outcome after hepatectomy.

Methods

All patients resected for CLM at our hospital between 1990 and 2004 with the following eligibility criteria were included in the study: (1) preoperative chemotherapy, (2) complete resection of CLM, (3) no extrahepatic disease, and (4) elevated baseline tumor marker values. A 20% change of tumor marker levels while on chemotherapy was used to define biological response (decrease) or progression (increase). Correlation between biological and radiological response at computed tomography (CT) scan, and their impact on overall survival (OS) and progression-free survival (PFS) after hepatectomy were determined.

Results

Among 119 of 695 consecutive patients resected for CLM who fulfilled the inclusion criteria, serial CEA and CA19.9 were available in 113 and 68 patients, respectively. Of patients with radiological response or stabilization, 94% had similar biological evolution for CEA and 91% for CA19.9. In patients with radiological progression, similar biological evolution was observed in 95% of cases for CEA and in 64% for CA19.9. On multivariate analysis, radiological response (but not biological evolution) independently predicted OS. However, progression of CA19.9, but not radiological response, was an independent predictor of PFS.

Conclusions

In patients with CLM and elevated tumor markers, biological response is as accurate as CT imaging to assess “clinical” response to chemotherapy. With regards to PFS, CA19.9 evolution has even better prognostic value than does radiological response. Assessment of tumor markers could be sufficient to evaluate chemotherapy response in a nonsurgical setting, limiting the need of repeat imaging.

Circadian Disruption in Experimental Cancer Processes

The circadian timing system (CTS) coordinated by the suprachiasmatic nuclei (SCN) of the hypothalamus regulates daily rhythms of behavior, physiology, as well as cellular metabolism and proliferation. Altered circadian rhythms predict for poor survival in cancer patients. An increased incidence of several cancers has been reported in flight attendants and in shift workers. To explore the contribution of the CTS to tumor growth, we developed experimental models of disrupted or enhanced circadian coordination through stereotaxic destruction of the SCN, modifications of photoperiodic or feeding synchronizers and/or the administration of pharmacologic agents. SCN ablation or exposure to experimental chronic jetlag (CJL, consisting of an 8-hour advance of the light-dark cycle every 2 days) caused alterations in circadian physiology and significantly accelerated tumor growth. CJL suppressed or altered the rhythms of clock gene and cell cycle gene expression in mouse liver. It increased p53 and decreased c-Myc expression, a result in line with the promotion of diethylnitrosamine -initiated hepatocarcinogenesis in jet-lagged mice. The accelerating effect of CJL on tumor growth was counterbalanced by the regular timing of food access over the 24-h. Meal timing prevented the circadian disruption produced by CJL and slowed down tumor growth. In synchronized mice, meal timing reinforced host circadian coordination, phase-shifted the transcriptional rhythms of clock genes in the liver of tumor-bearing mice and slowed down cancer progression. These results support the role of the CTS in cancer progression and call for the development of therapeutic strategies aimed at preventing or treating circadian clock dysfunctions.

Rescue chemotherapy using multidrug chronomodulated hepatic arterial infusion for patients with heavily pretreated metastatic colorectal cancer

BACKGROUND

: Hepatic arterial infusion (HAI) chemotherapy delivers a high concentration of drugs both to liver metastases and to healthy liver with specific, limiting, hepatobiliary toxicities. Relevant detoxification and cellular proliferation pathways are controlled by the molecular circadian clock in normal liver but not in advanced tumors. In this article, the authors report their experience with chronomodulated HAI chemotherapy as rescue therapy in heavily pretreated patients who had metastatic colorectal cancer.

METHODS

: Data from all consecutive patients with colorectal cancer liver metastases who received HAI with chronomodulated, multidrug chemotherapy regimens in the authors' center after failure on standard chemotherapy were reviewed for efficacy and safety.

RESULTS

: Twenty-nine patients were treated, including 76% with liver metastasis only and 24% with liver and lung metastases. Seventy-five percent of patients had received > or =3 chemotherapy lines, including intravenous, chronomodulated chemotherapy in 59% of patients. Patients received a median of 4 HAI courses (range, 1-9 courses). The most frequent grade (according to National Cancer Institute of Canada Common Toxicity Criteria [version 3]) 3 and 4 nonhematologic toxicities were vomiting, diarrhea, abdominal pain, and fatigue. No severe hematologic or hepatic toxicities and no chemical cholangitis were reported. An objective tumor response was observed in 10 patients (34.5%), including 4 patients who subsequently underwent R0 or R1 hepatic resection. The median progression-free survival and overall survival were 4.5 months (95% confidence limits, 2.4-6.5 months) and 18 months (95% confidence limits, 5.8-30.2 months), respectively.

CONCLUSIONS

: HAI chronomodulated chemotherapy had well tolerated activity in selected, heavily pretreated patients, and the authors believe it deserves to be assessed prospectively in clinical trials among patients who have less advanced disease. Cancer 2009. (c) 2009 American Cancer Society.

Liver circadian clock, a pharmacologic target of cyclin-dependent kinase inhibitor seliciclib

Circadian disruption accelerates malignant growth and shortens survival, both in experimental tumor models and cancer patients. In previous experiments, tumor circadian disruption was rescued with seliciclib, an inhibitor of cyclin-dependent kinases (CDKs). This effect occurred at a selective dosing time and was associated with improved antitumor activity. In the current study, seliciclib altered robust circadian mRNA expression of the clock genes Rev-erb alpha, Per2, and Bmal1 in mouse liver following dosing at zeitgeber time (ZT) 3 (i.e., 3 h after the onset of the 12 h light span), when mice start to rest, but not at ZT19, near the middle of the 12 h dark span, when mice are most active. However, liver exposure to seliciclib, as estimated by the liver area under the concentration x time curve (AUC), was approximately 80% higher at ZT19 than at ZT3 (p = 0.049). Circadian clock disruption was associated with increased serum liver enzymes and modified glycogen distribution in hepatocytes, as revealed by biochemical determinations and optic and electronic microscopy. The extent of increase in liver enzymes was most pronounced following dosing at ZT3, as compared to ZT19 (p < 0.04). Seliciclib further up-regulated the transcriptional activity of c-Myc, a cell cycle gene that promotes cell cycle entry and G1-S transition (p < 0.001), and down-regulated that of Wee1, which gates cell cycle transition from G2 to M (p < 0.001). These effects did not depend upon drug dosing time. Overall, the results suggest the circadian time of seliciclib delivery is more critical than the amount of drug exposure in determining its effects on the circadian clock. Seliciclib-induced disruption of the liver molecular clock could account for liver toxicity through the resulting disruption of clock-controlled detoxification pathways. Modifications of cell cycle gene expression in the liver likely involve other mechanisms. Circadian clocks represent relevant targets to consider for optimization of therapeutic schedules of CDK inhibitors.

Relations between strain and gender dependencies of irinotecan toxicity and UGT1A1, CES2 and TOP1 expressions in mice

Irinotecan hydrochloride (CPT-11) can display severe toxicities in individual cancer patients. CPT-11 is bio-activated through CES, detoxified through UGT1A1 and inhibits TOP1. CPT-11 toxicity and UGT1A1, CES2 and TOP1 mRNAs and UGT1A1 protein were determined in male and female C57BL/6, B6D2F1 and B6CBAF1, as potential models for tailoring CPT-11 delivery. CPT-11 was administered intravenously (40-90 mg/kg/day for 4 days at 7h after light onset). The relations between dose and lethal toxicity or body weight loss were steep and similar in C57BL/6 (lethality, p=0.001; weight loss, p=0.002) and B6D2F1 (p=0.01; p=0.03, respectively), but weak in B6CBAF1. Females displayed less toxicity than males (p<0.001). Mean mRNA expression of UGT1A1 was highest in B6CBAF1 (p=0.039) and in females (p<0.001). Both CES2 and TOP1 varied according to strain and gender (p<0.001). The three gene expression data explained the most severe toxicity of CPT-11 in male B6D2F1, but displayed inconsistent relations with toxicity in the other groups. Mean UGT1A1 protein expression was highest in males as compared to females, and so by approximately 8-fold in C57BL/6 as compared to B6D2F1 (p<0.0001). Genetic background and gender significantly altered the molecular prediction of irinotecan toxicity by UGT1A1, CES2 and TOP1 mRNA expressions.

Circadian disruption accelerates liver carcinogenesis in mice

BACKGROUND

The circadian timing system rhythmically controls behavior, physiology, cellular proliferation and xenobiotic metabolism over the 24-h period. The suprachiasmatic nuclei in the hypothalamus coordinate the molecular clocks in most mammalian cells through an array of circadian physiological rhythms including rest-activity, body temperature, feeding patterns and hormonal secretions. As a result, shift work that involves circadian disruption is probably carcinogenic in humans. In experimental models, chronic jet-lag (CJL) suppresses rest-activity and body temperature rhythms and accelerates growth of two transplantable tumors in mice. CJL also suppresses or significantly alters the expression rhythms of clock genes in liver and tumors. Circadian clock disruption from CJL downregulates p53 and upregulates c-Myc, thus favoring cellular proliferation. Here, we investigate the role of CJL as a tumor promoter in mice exposed to the hepatic carcinogen, diethylnitrosamine (DEN).

METHODS

In experiment 1 (Exp 1), the dose-dependent carcinogenicity of chronic intraperitoneal (i.p.) administration of DEN was explored in mice. In Exp 2, mice received DEN at 10 mg/kg/day (cumulative dose: 243 mg/kg), then were randomized to remain in a photoperiodic regimen where 12 h of light alternates with 12 h of darkness (LD 12:12) or to be submitted to CJL (8-h advance of light onset every 2 days). Rest-activity and body temperature were monitored. Serum liver enzymes were determined repeatedly. Mice were sacrificed and examined for neoplastic lesions at 10 months.

RESULTS

In Exp 1, DEN produced liver cancers in all the mice receiving 10 mg/kg/day. In Exp 2, mice on CJL had increased mean plasma levels of aspartate aminotransferase and more liver tumors as compared to LD mice at approximately 10 months (p = 0.005 and 0.028, respectively). The mean diameter of the largest liver tumor was twice as large in CJL vs LD mice (8.5 vs 4.4 mm, p = 0.027). In LD, a single histologic tumor type per liver was observed. In CJL, up to four different types were associated in the same liver (hepatocellular- or cholangio-carcinomas, sarcomas or mixed tumors). DEN itself markedly disrupted the circadian rhythms in rest-activity and body temperature in all the mice. DEN-induced disruption was prolonged for >or= 3 months by CJL exposure.

CONCLUSIONS

The association of circadian disruption with chronic DEN exposure suggests that circadian clocks actively control the mechanisms of liver carcinogenesis in mice. Persistent circadian coordination may further be critical for slowing down and/or reverting cancer development after carcinogen exposure.

Circadian rhythm in rest and activity: a biological correlate of quality of life and a predictor of survival in patients with metastatic colorectal cancer

The rest-activity circadian rhythm (CircAct) reflects the function of the circadian timing system. In a prior single-institution study, the extent of CircAct perturbation independently predicted for survival and tumor response in 192 patients receiving chemotherapy for metastatic colorectal cancer. Moreover, the main CircAct parameters correlated with several health-related quality of life (HRQoL) scales. In this prospective study, we attempted to extend these results to an independent cohort of chemotherapy-naive metastatic colorectal cancer patients participating in an international randomized phase III trial (European Organisation for Research and Treatment of Cancer 05963). Patients were randomized to receive chronomodulated or conventional infusion of 5-fluorouracil, leucovorin, and oxaliplatin as first-line treatment for metastatic colorectal cancer. Patients from nine institutions completed the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-C30 and wore a wrist accelerometer (actigraph) for 3 days before chemotherapy delivery. Two validated parameters (I<O and r24) were used to estimate CircAct. Of 130 patients with baseline CircAct assessments, 96 had baseline HRQoL data. I<O was confirmed to correlate with global quality of life, physical functioning, social functioning, fatigue, and appetite loss (r > |0.25|; P < 0.01). I<O further independently predicted for overall survival with a hazard ratio of 0.94 (P < 0.0001). The associations between CircAct parameters, HRQoL, and survival, which were shown in this international study involving previously untreated metastatic colorectal cancer patients, confirm prior single-institution findings in mostly pretreated metastatic colorectal cancer patients. The circadian timing system constitutes a novel therapeutic target. Interventions that normalize circadian timing system dysfunction may affect quality of life and survival in cancer patients.

Circadian Rhythm of Irinotecan Tolerability in Mice

The toxicity of irinotecan (CPT-11), a topoisomerase-I inhibitor largely used in cancer patients, was investigated as a function of the circadian time of its administration in mice, with mortality, body weight loss, leukopenia, neutropenia, intestinal lesions, and bone marrow cell cycle phase distribution as end points. Four experiments were performed on a total of 773 male mice standardized with 12h light/12h darkness. Irinotecan was administered daily for 4 or 10 consecutive days (D1-4 and D1-10, respectively, in different experiments) at one of six circadian stages expressed in hours after light onset (HALO). The survival curves differed significantly as a function of the dosage and circadian time of drug administration by the D1-10 schedule, with 70% survival at 7 or 11 HALO and 51% at 19 or 23 HALO (p=0.039 from log rank test). CPT-11 administration at 19 or 23 HALO resulted in (1) greatest mean body weight loss at nadir; (2) most severe colic and bone marrow lesions and/or slowest recovery; and (3) deepest neutropenia nadir and/or slowest hematologic recovery. These circadian treatment time-related differences were statistically validated. The bone marrow cell cycle data revealed a four to eight-fold larger G2-M phase arrest following irinotecan administration at 19 or 23 HALO in comparison to the other times of drug administration, apparently representative of the repair of more extensive DNA damage (p < 0.001 from ANOVA) when the medication was given at these circadian times. Overall, CPT-11 was better tolerated by mice treated during the light (animals' rest) span. The results support the administration of CPT-11 to cancer patients in the second half of the night, during sleep, in order to improve drug tolerability.