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Host circadian clock as a control point in tumor progression
Elisabeth Filipski1, Verdun M King, XiaoMei Li
1Institut National de la Santé et de la Recherche Médicale, Equipe Propre INSERM 0118 Cancer chronotherapeutics, Université Paris XI, Paul Brousse Hospital, Villejuif, France.
Background:
The circadian timing system controlled by the suprachiasmatic nuclei (SCN) of the hypothalamus regulates daily rhythms of motor activity and adrenocortical secretion. An alteration in these rhythms is associated with poor survival of patients with metastatic colorectal or breast cancer. We developed a mouse model to investigate the consequences of severe circadian dysfunction upon tumor growth.
Methods:
The SCN of mice were destroyed by bilateral electrolytic lesions, and body activity and body temperature were recorded with a radio transmitter implanted into the peritoneal cavity. Plasma corticosterone levels and circulating lymphocyte counts were measured (n = 75 with SCN lesions, n = 64 sham-operated). Complete SCN destruction was ascertained postmortem. Mice were inoculated with implants of Glasgow osteosarcoma (n = 16 with SCN lesions, n = 12 sham-operated) or pancreatic adenocarcinoma (n = 13 with SCN lesions, n = 13 sham-operated) tumors to determine the effects of altered circadian rhythms on tumor progression. Time series for body temperature and rest-activity patterns were analyzed by spectral analysis and cosinor analysis. Parametric data were compared by the use of analysis of variance (ANOVA) and survival curves with the log-rank test. All statistical tests were two-sided.
Results:
The 24-hour rest-activity cycle was ablated and the daily rhythms of serum corticosterone level and lymphocyte count were markedly altered in 75 mice with complete SCN destruction as compared with 64 sham-operated mice (two-way ANOVA for corticosterone: sampling time effect P<.001, lesion effect P =.001, and time x lesion interaction P<.001; for lymphocytes P =.001,.002, and.002 respectively). Body temperature rhythm was suppressed in 60 of the 75 mice with SCN lesions (P<.001). Both types of tumors grew two to three times faster in mice with SCN lesions than in sham-operated mice (two-way ANOVA: P<.001 for lesion and for tumor effects; P =.21 for lesion x tumor effect interaction). Survival of mice with SCN lesions was statistically significantly shorter compared with that of sham-operated mice (log-rank P =.0062).
Conclusions:
Disruption of circadian rhythms in mice was associated with accelerated growth of malignant tumors of two types, suggesting that the host circadian clock may play an important role in endogenous control of tumor progression.
Insights
Disrupting the circadian timing system by destroying the suprachiasmatic nuclei (SCN) in mice accelerated tumor growth and reduced survival. This highlights the circadian clock's role in controlling cancer progression.
Area of Science:
- Chronobiology
- Oncology
- Neuroscience
Background:
- The suprachiasmatic nuclei (SCN) regulate daily rhythms crucial for physiological processes.
- Altered circadian rhythms are linked to poorer survival in metastatic cancers.
- A mouse model was created to study circadian dysfunction's impact on tumor growth.
Purpose of the Study:
- To investigate the consequences of severe circadian dysfunction on tumor progression.
- To determine the role of the host circadian clock in endogenous tumor control.
Main Methods:
- Bilateral electrolytic lesions were used to destroy the SCN in mice.
- Rest-activity, body temperature, corticosterone, and lymphocyte counts were monitored.
- Mice were inoculated with osteosarcoma or pancreatic adenocarcinoma tumors.
Main Results:
- SCN lesions ablated the rest-activity cycle and altered daily rhythms of corticosterone and lymphocytes.
- Tumor growth was 2-3 times faster in mice with SCN lesions compared to controls.
- Survival was significantly shorter in mice with disrupted circadian rhythms.
Conclusions:
- Disruption of circadian rhythms accelerates the growth of malignant tumors.
- The host circadian clock plays a significant role in the endogenous control of tumor progression.