Rotating night shifts and risk of skin cancer in the nurses' health study

Unraveling the role of the circadian clock genes in cervical squamous cell carcinoma and endocervical adenocarcinoma: A prognostic indicator for prognostic, immunotherapy response, and chemotherapy sensitivity

Background: Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) account for a significant proportion of gynecological malignancies and represent a major global health concern. Globally, CESC is ranked as the fourth most common cancer among women. Conventional treatment of this disease has a less favorable prognosis for most patients. However, the discovery of early molecular biomarkers is therefore important for the diagnosis of CESC, as well as for slowing down their progression process. Methods: To identify differentially expressed genes strongly associated with prognosis, univariate Cox proportional hazard analysis and least absolute shrinkage and selection operator (LASSO) regression analysis were used. Using multiple Cox proportional hazard regression, a multifactorial model for prognostic risk assessment was then created. Results: The expression of biological clock-related genes, which varied considerably among distinct subtypes and were associated with significantly diverse prognoses, was used to categorize CESC patients. These findings demonstrate how the nomogram developed based on the 7-CRGs signature may assist physicians in creating more precise, accurate, and successful treatment plans that can aid CESC patients at 1, 3, and 5 years. Conclusions: By using machine learning techniques, we thoroughly investigated the impact of CRGs on the prognosis of CESC patients in this study. By creating a unique nomogram, we were able to accurately predict patient prognosis. At the same time, we showed new perspectives on the development of CESC and its treatment by analyzing the associations of the prognostic model with immunity, enrichment pathways, chemotherapy sensitivity, and so on. This research provides a new direction for clinical treatment.

Circadian Rhythm Dysregulation and Leukemia Development: The Role of Clock Genes as Promising Biomarkers

The circadian clock (CC) is a daily system that regulates the oscillations of physiological processes and can respond to the external environment in order to maintain internal homeostasis. For the functioning of the CC, the clock genes (CG) act in different metabolic pathways through the clock-controlled genes (CCG), providing cellular regulation. The CC’s interruption can result in the development of different diseases, such as neurodegenerative and metabolic disorders, as well as cancer. Leukemias correspond to a group of malignancies of the blood and bone marrow that occur when alterations in normal cellular regulatory processes cause the uncontrolled proliferation of hematopoietic stem cells. This review aimed to associate a deregulated CC with the manifestation of leukemia, looking for possible pathways involving CG and their possible role as leukemic biomarkers.

Circadian rhythms and cancers: the intrinsic links and therapeutic potentials

The circadian rhythm is an evolutionarily conserved time-keeping system that comprises a wide variety of processes including sleep-wake cycles, eating-fasting cycles, and activity-rest cycles, coordinating the behavior and physiology of all organs for whole-body homeostasis. Acute disruption of circadian rhythm may lead to transient discomfort, whereas long-term irregular circadian rhythm will result in the dysfunction of the organism, therefore increasing the risks of numerous diseases especially cancers. Indeed, both epidemiological and experimental evidence has demonstrated the intrinsic link between dysregulated circadian rhythm and cancer. Accordingly, a rapidly increasing understanding of the molecular mechanisms of circadian rhythms is opening new options for cancer therapy, possibly by modulating the circadian clock. In this review, we first describe the general regulators of circadian rhythms and their functions on cancer. In addition, we provide insights into the mechanisms underlying how several types of disruption of the circadian rhythm (including sleep-wake, eating-fasting, and activity-rest) can drive cancer progression, which may expand our understanding of cancer development from the clock perspective. Moreover, we also summarize the potential applications of modulating circadian rhythms for cancer treatment, which may provide an optional therapeutic strategy for cancer patients.

Daily Lifestyle and Cutaneous Malignancies

Daily lifestyle is a fundamental part of human life and its influence accumulates daily in the human body. We observe that a good daily lifestyle has a beneficial impact on our health; however, the actual effects of individual daily lifestyle factors on human skin diseases, especially skin cancers, have not been summarized. In this review, we focused on the influence of daily lifestyle on the development of skin cancer and described the detailed molecular mechanisms of the development or regulation of cutaneous malignancies. Several daily lifestyle factors, such as circadian rhythm disruption, smoking, alcohol, fatty acids, dietary fiber, obesity, and ultraviolet light, are known to be associated with the risk of cutaneous malignancies, malignant melanoma, squamous cell carcinoma, basal cell carcinoma, and Merkel cell carcinoma. Although the influence of some daily lifestyles on the risk of skin cancers is controversial, this review provides us a better understanding of the relationship between daily lifestyle factors and skin cancers.

Occupational Skin Disease in Physicians: A Review of the Literature

OBJECTIVES

Occupational skin disease (OSD) arises from work-related activity. However, there is a paucity of literature on OSD in physicians. The aim of the this review was therefore to examine and summarize what types of symptomatic OSD physicians experience.

METHODS

We conducted a systematic literature search on Cochrane Library, Embase, and Pubmed.

RESULTS

Contact dermatitis from formaldehyde and glutaraldehyde were found in 11.5 and 13.5% of cases, respectively. In total 2.4-14.9% had latex allergy. The reported standardized incidence ratio of squamous cell carcinoma and melanoma was up to 2.15 [95% confidence interval (CI) 1.57-1.95] and 3.2 (95% CI 1.38-6.31). Transmission of human papilloma virus (HPV) particles during carbon dioxide laser wart ablation were found in 70% of samples collected from protective gloves and in 52% of samples from vapors.

CONCLUSIONS

The most frequently reported OSD in physicians is contact dermatitis from allergens in disinfectants and rubber gloves. There is also a risk of cutaneous reactions to latex. The incidence of skin cancer was higher in physicians than in the general population, and the reason for this remains unexplained and potentially biased. There are no reports of transmission of patient HPV to surgeons during wart ablation, possibly because of proper use of protective equipment.

Influence of the Exposome on Skin Cancer

Skin cancer is the most frequent type of cancer in humans. While exposure to solar radiation is the most widely known and relevant causal factor, the different degrees of individual risk have not been fully elucidated. Epidemiological studies show how the risk of skin cancer is affected by other types of radiation (eg, ionizing radiation), pesticides, particulate matter in air pollution, toxins (eg, arsenic) in water and some foods. Some living entities, such as polyomavirus and human papillomavirus, can also cause specific types of cancer. Lastly, lifestyle factors such as stress, sleep, and exercise may play a role, although only a few studies shed light on these factors. The abovementioned factors make up the exposome of skin cancer, that is, the set of environmental exposures that, together with the genome and microbiome, determine the onset of disease.

Late Chronotype is Associated with Adolescent Asthma: Assessment Using the Korean-Version MCTQ

Objectives: In the study, we explored whether sleep chronotypes are associated with asthma in adolescents. Methods: We analyzed 24,655 physician-diagnosed adolescent asthmatic patients and 253,775 non-asthmatic adolescent patients from the Korea Youth Risk Behavior Web-based Survey (KYRBWS). Socioeconomic factors, health behaviors factors, psychological factors, and sleep parameters were assessed using the Munich Chronotype Questionnaire (MCTQ). Logistic regression after adjusting for multiple confounders was used to explore the association between sleep chronotype and asthma. Results: The asthmatic adolescent group slept less (≤5 h: 24.3% vs. 23.2%) than the non-asthmatic adolescent group. Mean sleep duration (430.6 ± 95.6 vs. 433.5 ± 93.6 min), midpoint of sleep on school-free days (MSF; 255.9 ± 75.9 vs. 258.3 ± 73.6 min), midpoint of sleep on school days (MSW; 199.1 ± 49.1 vs. 200.1 ± 48.4 min), sleep duration on school days (SDW; 398.2 ± 98.1 vs. 400.2 ± 96.8 min), and sleep duration on school-free days (SDF; 511.8 ± 151.9 vs. 516.7 ± 147.2 min) were significantly lower, sleep satisfaction was significantly poorer (low sleep satisfaction: 41.3% vs. 37.5%), and late chronotype was significantly higher in the asthmatic adolescent (21.1% vs. 20.0%). After adjusting for multiple confounders, late chronotype was significantly associated with an increased frequency of adolescent asthma (OR 1.05; 95% CI 1.01–1.09) compared to intermediate chronotypes. Conclusions: Although our study shows a very modest association (OR of 1.05 in the fully adjusted model), we show that the late sleep chronotype is associated with asthma in adolescents in South Korea.

Shift work and risk of skin cancer: A systematic review and meta-analysis

Shift work with circadian disruption has been considered as a carcinogenic risk factor for skin cancer. The few prior studies that investigated the association between shift work and skin cancer have inconclusive results. Our main objective was to evaluate the associations between shift work and the risks of different types of skin cancer. We systematically searched PubMed, Web of Science, Cochrane Library, EMBASE and Science Direct until October 2018 for studies that included a relationship between shift work and skin cancer. Our search yielded 193 articles and 9 studies met the criteria for our review. The included studies involved 3,579,147 participants and 17,308 skin cancer cases. Overall, ever shift work, was associated with increased risk of melanoma (RR = 1.10, 95% CI = 1.05–1.16) and a significant decrease in the risk of BCC (RR = 0.90, 95% CI = 0.88–0.93). No association between shift work and the risk of SCC was detected. Interestingly, our dose response analysis demonstrated that the risk of melanoma cumulatively increases by 2% for every year of shift work (RR = 1.02; 95% CI = 1.00–1.03). In conclusion, shift work is associated with increased risk of melanoma and deceased risk of BCC. Further studies are needed to confirm our findings and to elucidate the related potential biological mechanisms.

The Cancer Clock Is (Not) Ticking: Links between Circadian Rhythms and Cancer

Circadian rhythms regulate many physiological and behavioral processes, including sleep, metabolism and cell division, which have a 24-h oscillation pattern. Rhythmicity is generated by a transcriptional–translational feedback loop in individual cells, which are synchronized by the central pacemaker in the brain and external cues. Epidemiological and clinical studies indicate that disruption of these rhythms can increase both tumorigenesis and cancer progression. Environmental changes (shift work, jet lag, exposure to light at night), mutations in circadian regulating genes, and changes to clock gene expression are recognized forms of disruption and are associated with cancer risk and/or cancer progression. Experimental data in animals and cell cultures further supports the role of the cellular circadian clock in coordinating cell division and DNA repair, and disrupted cellular clocks accelerate cancer cell growth. This review will summarize studies linking circadian disruption to cancer biology and explore how such disruptions may be further altered by common characteristics of tumors including hypoxia and acidosis. We will highlight how circadian rhythms might be exploited for cancer drug development, including how delivery of current chemotherapies may be enhanced using chronotherapy. Understanding the role of circadian rhythms in carcinogenesis and tumor progression will enable us to better understand causes of cancer and how to treat them.

Circadian Rhythm and the Skin: A Review of the Literature

Disruption of the circadian rhythm has been implicated in a wide variety of dermatologic conditions. Research has shown that previous ultraviolet light exposure can continue to damage the deoxyribonucleic acid (DNA) of the skin, even in the dark, and has demonstrated that repair of these skin cells peaks at night. In this article, the authors reviewed the current literature on circadian rhythm effects on the skin and describe and discuss its basic principles. Better understanding of the role circadian rhythm plays in overall skin health will assist physicians in providing optimal treatment to patients, including appropriate recommendations regarding the use of topical medications and skin care at their most effective times during a 24-hour cycle. Dermatologists should also be aware that adequate sleep is necessary for optimal DNA repair activity in the skin.

Circadian (De)regulation in Head and Neck Squamous Cell Carcinoma

Head and neck cancer encompass different malignancies that develop in and around the throat, larynx, nose, sinuses and mouth. Most head and neck cancers are squamous cell carcinomas (HNSCC) that arise in the flat squamous cells that makeup the thin layer of tissue on the surface of anatomical structures in the head and neck. Each year, HNSCC is diagnosed in more than 600,000 people worldwide, with about 50,000 new cases. HNSCC is considered extremely curable if detected early. But the problem remains in treatment of inoperable cases, residues or late stages. Circadian rhythm regulation has a big role in developing various carcinomas, and head and neck tumors are no exception. A number of studies have reported that alteration in clock gene expression is associated with several cancers, including HNSCC. Analyses on circadian clock genes and their association with HNSCC have shown that expression of PER1, PER2, PER3, CRY1, CRY2,CKIε, TIM, and BMAL1 are deregulated in HNSCC tissues. This review paper comprehensively presents data on deregulation of circadian genes in HNSCC and critically evaluates their potential diagnostics and prognostics role in this type of pathology.

Melanoma, thyroid cancer, and gynecologic cancers in a cohort of female flight attendants

BACKGROUND

Flight attendants may have an increased risk of some cancers from occupational exposure to cosmic radiation and circadian disruption.

METHODS

The incidence of thyroid, ovarian, and uterine cancer among ∼6000 female flight attendants compared to the US population was evaluated via life table analyses. Associations of these cancers, melanoma, and cervical cancer with cumulative cosmic radiation dose and metrics of circadian disruption were evaluated using Cox regression.

RESULTS

Incidence of thyroid, ovarian, and uterine cancer was not elevated. No significant, positive exposure-response relations were observed. Weak, non-significant, positive relations were observed for thyroid cancer with cosmic radiation and time zones crossed and for melanoma with another metric of circadian disruption.

CONCLUSIONS

We found little evidence of increased risk of these cancers from occupational cosmic radiation or circadian disruption in female flight attendants. Limitations include few observed cases of some cancers, limited data on risk factors, and misclassification of exposures.

Can yesterday's smoking research inform today's shiftwork research? Epistemological consequences for exposures and doses due to circadian disruption at and off work

In 1950, landmark epidemiology studies by Wynder & Graham and Doll & Hill contributed to identifying smoking as a potent carcinogen. In 2007, IARC classified shiftwork involving circadian disruption (CD) as probably carcinogenic; however, epidemiological evidence in regards to the carcinogenicity of shiftwork that involves nightwork is conflicting. We hypothesize that shiftwork research is lacking chronobiological and methodological rigor and that lessons can be learned from comparison with smoking research. Herein, we provide a factual view at, and a fictional case study of, 1940s smoking research which serves as an analogy for current shiftwork research dilemmas. This analogy takes the form of limiting counting cigarettes to a particular time window (i.e. at work) rather than assessing exposures to, and doses of, accumulated smoking over 24 h, highlighting the importance of exposure and dose. Simply put, smoking insights could have been delayed or even disallowed. In conclusion, CD may be similar to smoking insofar as for quantitative measures of cumulative doses, exposures both at and off work may have to be considered. Future work must explore whether such similarity factually exists and whether CD is a cancer hazard in IARC terms.

Associations among rotating night shift work, sleep and skin cancer in Nurses' Health Study II participants

BACKGROUND

Night shift work and sleep duration have been associated with breast and other cancers. Results from the few prior studies of night shift work and skin cancer risk have been mixed and not fully accounted for other potentially important health-related variables (eg, sleep characteristics). This study evaluated the relationship between rotating night shift work and skin cancer risk and included additional skin cancer risk factors and sleep-related variables.

METHODS

The current study used data from 74 323 Nurses' Health Study (NHS) II participants. Cox proportional hazards models were used to estimate multivariable-adjusted HRs and 95% CIs for skin cancers across categories of shift work and sleep duration.

RESULTS

Over 10 years of follow-up, 4308 basal cell carcinoma (BCC), 334 squamous cell carcinoma (SCC) and 212 melanoma cases were identified. Longer duration of rotating night shifts was associated with a linear decline in risk of BCC (HR=0.93, 95% CI 0.90 to 0.97 per 5-year increase). Shift work was not significantly associated with either melanoma (HR=1.02, 95% CI 0.86 to 1.21) or SCC (HR=0.92, 95% CI 0.80 to 1.06). A short sleep duration (≤6 hours per day) was associated with lower risks of melanoma (HR=0.68, 95% CI 0.46 to 0.98) and BCC (HR=0.93, 95% CI 0.86 to 1.00) compared with the most common report of 7 hours. SCC was not associated with duration of sleep (HR=0.94, 95% CI 0.83 to 1.06).

CONCLUSIONS

Longer duration of rotating night shift work and shorter sleep duration were associated with lower risk of some skin cancers. Further research is needed to confirm and identify the mechanisms underlying these associations.

Occupational skin cancer: Systematic review

OBJECTIVE

To analyze the epidemiological profile, risk factors in the workplace environment and prevention methods for professionals at risk of skin cancer.

METHOD

A systematic review of articles on occupational skin cancer, published in the Lilacs, Scielo, Medline and Cochrane Library from January 1st, 2008, to December 31st, 2013, was performed. The search included the following terms: "neoplasias cutâneas" (DeCS), "exposição ocupacional" (DeCS), "epidemiologia" (DeCS) as well as the keyword "prevenção", and their equivalents in English.

RESULTS

After analyzing the titles and summaries of articles, the search strategy resulted in 83 references, of which 22 articles met the eligibility criteria.

DISCUSSION

We found that sun exposure is the main occupational risk factor for skin cancer, causing outdoor workers to be the most vulnerable to developing occupational skin cancer. Professionals with low levels of education and European descent are at increased risk of developing this cancer.

CONCLUSION

Outdoor workers are more vulnerable to developing occupational skin cancer, estimating that professionals with low level of education and European descent are at increased risk of developing this cancer. Therefore, companies need to invest more in the health of workers by providing protective equipment and thus preventing occupational skin cancer.

Caffeine Intake, Coffee Consumption, and Risk of Cutaneous Malignant Melanoma

BACKGROUND

Caffeine has been shown to prevent ultraviolet radiation-induced carcinogenesis and to inhibit growth of melanoma cells in experimental studies. We evaluated the association among caffeine intake, coffee consumption, and melanoma risk among three large cohort studies.

METHODS

The analysis used data from 89,220 women in the Nurses' Health Study II (1991-2009), 74,666 women in the Nurses' Health Study (1980-2008), and 39,424 men in the Health Professionals Follow-up Study (1986-2008). We used Cox proportional hazards models to estimate the hazard ratios (HR) with 95% confidence intervals (CIs) of melanoma associated with dietary intakes.

RESULTS

We documented 2,254 melanoma cases over 4 million person-years of follow-up. After adjustment for other risk factors, higher total caffeine intake was associated with a lower risk of melanoma (≥393 mg/day vs. <60 mg/day: HR = 0.78, 95% CI = 0.64, 0.96; Ptrend = 0.048). The association was more apparent in women (≥393 mg/day vs. <60 mg/day: HR = 0.70, 95% CI = 0.58, 0.85; Ptrend = 0.001) than in men (HR = 0.94, 95% CI = 0.75, 1.2; Ptrend = 0.81), and more apparent for melanomas occurring on body sites with higher continuous sun exposure (head, neck, and extremities; ≥393 mg/day vs. <60 mg/day: HR = 0.71, 95% CI = 0.59, 0.86; Ptrend = 0.001) than for melanomas occurring on body sites with lower continuous sun exposure (trunk including shoulder, back, hip, abdomen, and chest; HR = 0.90, 95% CI = 0.70, 1.2; Ptrend = 0.60). This pattern of association was similar to that for caffeinated coffee consumption, whereas no association was found for decaffeinated coffee consumption and melanoma risk.

CONCLUSIONS

Increasing caffeine intake and caffeinated coffee consumption is associated with decreased risk of cutaneous malignant melanomas.

Long-term ultraviolet flux, other potential risk factors, and skin cancer risk: a cohort study

BACKGROUND

Few prospective studies have examined the relationship between sun exposure, other potential risk factors, and risk of different skin cancers [including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma] simultaneously.

METHODS

We evaluated the association between a number of potential risk factors and skin cancer risk in a cohort of 108,916 US women, the Nurses' Health Study II (1989-2009).

RESULTS

During 2.05 million years of follow-up, we identified 6,955, 880, and 779 diagnoses of BCC, SCC, and melanoma, respectively. Compared with participants in the lowest quintile of cumulative ultraviolet flux in adulthood, participants in the highest quintile had multivariable-adjusted relative risks (RR) of 2.35 (Ptrend < 0.0001) for BCC, 2.53 (Ptrend = 0.009) for SCC, and 0.68 (Ptrend = 0.38) for melanoma. In contrast, the RRs were 1.68 (95% CI, 1.55-1.82) for BCC, 1.68 (95% CI, 1.34-2.11) for SCC, and 1.80 (95% CI, 1.42-2.28) for melanoma for participants with ≥5 blistering sunburns when compared with participants without sunburn between ages 15 and 20 years. We found significant interactions between family history of melanoma, number of blistering sunburns between ages 15 and 20 years and BCC risk, and between sunburn reaction as a child/adolescent and SCC risk (all Pinteraction < 0.05).

CONCLUSION

In a cohort of U.S. women, we found that sun exposures in both early life and adulthood were predictive of BCC and SCC risks, whereas melanoma risk was predominantly associated with sun exposure in early life.

IMPACT

Our results may have potential implications for the prevention of skin cancers. Cancer Epidemiol Biomarkers Prev; 23(6); 1080-9. ©2014 AACR.

Circadian Dysrhythmias, Physiological Aberrations, and the Link to Skin Cancer

Circadian rhythms are core regulators of a variety of mammalian physiologic processes and oscillate in a 24-h pattern. Many peripheral organs possess endogenous rhythmicity that is then modulated by a master clock; the skin is one of these peripheral organs. The dysregulation of rhythms is associated with decreased ability to ameliorate cellular stressors at a local and global level, which then increases the propensity for the development of neoplastic growths. In this article, we review the implications of altered circadian rhythms on DNA repair as well as modified gene expression of core clock proteins with particular focus on skin models. These findings are then correlated with epidemiologic data regarding skin cancer to showcase the effects of circadian disruption on this phenomenon.

Melatonin decreases cell proliferation, impairs myogenic differentiation and triggers apoptotic cell death in rhabdomyosarcoma cell lines

Melatonin is a small indole produced by the pineal gland and other tissues, and has numerous functions that aid in the maintenance of the whole body homeostasis, ranging from the regulation of circadian rhythms and sleep to protection from oxidative stress. Melatonin has also been reported to counteract cell growth and chemoresistance in different types of cancer. In the present study, we investigated the effects of exogenous melatonin administration on different human cell lines and primary mouse tumor cultures of rhabdomyosarcoma (RMS), the most frequent soft tissue sarcoma affecting childhood. The results showed that melatonin significantly affected the behavior of RMS cells, leading to inhibition of cell proliferation and impairment of myogenic differentiation followed by increased apoptotic cell death, as observed by immunoblotting analysis of apoptosis-related markers including Bax, Bcl-2 and caspase-3. Similar findings were observed using a combination of microscopy techniques, including scanning/transmission electron and confocal microscopy. Furthermore, melatonin in combination with doxorubicin or cisplatin, two compounds commonly used for the treatment of solid tumors, increased the sensitivity of RMS cells to apoptosis. These data indicated that melatonin may be effective in counteracting RMS tumor growth and chemoresistance.

Sleep duration and mortality: a prospective study of 113 138 middle-aged and elderly Chinese men and women

OBJECTIVES

To evaluate associations of sleep duration with total mortality and disease-specific mortality in a Chinese population.

DESIGN

Prospective study conducted from 1996 (for women)/2002 (for men) to 2010.

SETTING

A population-based cohort study in Shanghai, China.

INTERVENTION

None.

MEASUREMENTS AND RESULTS

A total of 113,138 participants (68,548 women and 44,590 men) of the Shanghai Women's and Men's Health Studies, aged 44-79 y and 40-75 y (women and men, respectively) at sleep duration assessment, were included in the study. In-person interviews were conducted to collect information on sleep duration, socioeconomic status, living conditions, history of chronic disease, participation in regular exercise, and family history of disease. The cohort has been followed using a combination of biannual in-person interviews and record linkages with Shanghai's population-based death registry. Survival status of participants on December 31, 2010 was included as the study outcome. Relative risks were calculated using a Cox proportional model stratified by sex and comorbidity score. There were 4,277 deaths (2,356 among women; 1,921 among men) during a median follow-up time of 7.12 y for women and 6.07 y for men. Among both women and men, sleep duration showed a J-shaped association with total mortality. Hazard ratios (95% confidence intervals) were 1.15 (1.01-1.32), 1.06 (0.94-1.20), 1.17 (1.04-1.32), 1.36 (1.13-1.64), and 2.11 (1.77-2.52) for women and 1.06 (0.90-1.25), 1.07 (0.94-1.23), 1.13 (1.00-1.28), 1.34 (1.10-1.62), and 1.55 (1.29-1.86) for men who slept 4-5, 6, 8, 9, and ≥ 10 h per day, respectively, compared with those who slept 7 h per day. Associations for disease-specific mortality, including cardiovascular disease, stroke, diabetes, and cancer, also generally followed the same J-shaped pattern. The sleep duration-mortality association was more evident among participants with comorbidities, but varied little by sex.

CONCLUSION

In our study population of Chinese adults, shorter and longer sleep durations were independently associated with increased risk of mortality. But longer sleep duration had a higher mortality risk of cardiovascular disease and diabetes than short sleep.

Skin, reactive oxygen species, and circadian clocks

SIGNIFICANCE

Skin, a complex organ and the body's first line of defense against environmental insults, plays a critical role in maintaining homeostasis in an organism. This balance is maintained through a complex network of cellular machinery and signaling events, including those regulating oxidative stress and circadian rhythms. These regulatory mechanisms have developed integral systems to protect skin cells and to signal to the rest of the body in the event of internal and environmental stresses.

RECENT ADVANCES

Interestingly, several signaling pathways and many bioactive molecules have been found to be involved and even important in the regulation of oxidative stress and circadian rhythms, especially in the skin. It is becoming increasingly evident that these two regulatory systems may, in fact, be interconnected in the regulation of homeostasis. Important examples of molecules that connect the two systems include serotonin, melatonin, vitamin D, and vitamin A.

CRITICAL ISSUES

Excessive reactive oxygen species and/or dysregulation of antioxidant system and circadian rhythms can cause critical errors in maintaining proper barrier function and skin health, as well as overall homeostasis. Unfortunately, the modern lifestyle seems to contribute to increasing alterations in redox balance and circadian rhythms, thereby posing a critical problem for normal functioning of the living system.

FUTURE DIRECTIONS

Since the oxidative stress and circadian rhythm systems seem to have areas of overlap, future research needs to be focused on defining the interactions between these two important systems. This may be especially important in the skin where both systems play critical roles in protecting the whole body.

Deregulated expression of circadian clock genes in gastric cancer

BACKGROUND

Gastric cancer (GC), an aggressive malignant tumor of the alimentary tract, is a leading cause of cancer-related death. Circadian rhythm exhibits a 24-hour variation in physiological processes and behavior, such as hormone levels, metabolism, gene expression, sleep and wakefulness, and appetite. Disruption of circadian rhythm has been associated with various cancers, including chronic myeloid leukemia, head and neck squamous cell carcinoma, hepatocellular carcinoma, endometrial carcinoma, and breast cancer. However, the expression of circadian clock genes in GC remains unexplored.

METHODS

In this study, the expression profiles of eight circadian clock genes (PER1, PER2, PER3, CRY1, CRY2, CKIϵ, CLOCK, and BMAL1) of cancerous and noncancerous tissues from 29 GC patients were investigated using real-time quantitative reverse-transcriptase polymerase chain reaction and validated through immunohistochemical analysis.

RESULTS

We found that PER2 was significantly up-regulated in cancer tissues (p < 0.005). Up-regulated CRY1 expression was significantly correlated with more advanced stages (stage III and IV) (p < 0.05).

CONCLUSIONS

Our results suggest deregulated expressions of circadian clock genes exist in GC and circadian rhythm disturbance may be associated with the development of GC.

Cumulative ultraviolet radiation flux in adulthood and risk of incident skin cancers in women

BACKGROUND

Solar ultraviolet (UV) exposure estimated based on residential history has been used as a sun exposure indicator in previous case-control and descriptive studies. However, the associations of cumulative UV exposure based on residential history with different skin cancers, including melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC), have not been evaluated simultaneously in prospective studies.

METHODS

We conducted a cohort study among 108,578 women in the Nurses' Health Study (1976-2006) to evaluate the relative risks of skin cancers with cumulative UV flux based on residential history in adulthood.

RESULTS

Risk of SCC and BCC was significantly lower for women in lower quintiles vs the highest quintile of cumulative UV flux (both P for trend <0.0001). The association between cumulative UV flux and risk of melanoma did not reach statistical significance. However, risk of melanoma appeared to be lower among women in lower quintiles vs the highest quintile of cumulative UV flux in lag analyses with 2-10 years between exposure and outcome. The multivariable-adjusted hazard ratios per 200 × 10(-4) Robertson-Berger units increase in cumulative UV flux were 0.979 (95% confidence interval (CI): 0.933, 1.028) for melanoma, 1.072 (95% CI: 1.041, 1.103) for SCC, and 1.043 (95% CI: 1.034, 1.052) for BCC.

CONCLUSIONS

Associations with cumulative UV exposure in adulthood among women differed for melanoma, SCC, and BCC, suggesting a potential variable role of UV radiation in adulthood in the carcinogenesis of the three major skin cancers.

Social jetlag negatively correlates with academic performance in undergraduates

Discrepancies between sleep timing on workdays and weekends, also known as social jetlag (SJL), affect the majority of the population and have been found to be associated with increased health risk and health-impairing behaviors. In this study, we explored the relationship between SJL and academic performance in a sample of undergraduates of the Semmelweis University. We assessed SJL and other sleep-related parameters with the Munich ChronoType Questionnaire (MCTQ) (n = 753). Academic performance was measured by the average grade based on weekly test results as well as scores acquired on the final test (n = 247). The average mid-sleep point on free days in the Hungarian sample fits well the regression line plotted for longitudes within the Central European Time Zone and chronotypes, confirming that sunlight has a major impact on chronotype. Multivariate analysis showed negative effect of SJL on the weekly average grade (p = 0.028, n = 247) during the lecture term with its highly regular teaching schedules, while this association disappeared in the exam period (p = 0.871, n = 247) when students had no scheduled obligations (lower SJL). We also analyzed the relationship between the time of the weekly tests and academic performance and found that students with later sleep times on free days achieved worse in the morning (p = 0.017, n = 129), while the inverse tendency was observed for the afternoon test-takers (p = 0.10, n = 118). We did not find significant association between academic performance and sleep duration or sleep debt on work days. Our data suggest that circadian misalignment can have a significant negative effect on academic performance. One possible reason for this misalignment is socially enforced sleep times.

the risk of cancer among Taiwanese female registered nurses: a nationwide retrospective study

Background

To evaluate the risk of cancer among Taiwanese female registered nurses (RNs) using a nationwide population-based dataset.

Methods

We recruited female RNs without antecedent cancer from the Taiwan National Health Insurance Research database during 2000–2010. Standardized incidence ratios (SIRs) of cancer were calculated. We also compared rates of Papanicolaou (Pap) smear use between the RNs and the general population matched by age and sex.

Results

A total of 2,077 cancers developed among 184,809 female RNs, with a follow-up of 1,371,910 person-years (median follow-up of 7.86 years), leading to an increased SIR of 1.10 [95% confidence interval (CI) 1.05–1.15]. RNs aged between 40–59 years also had a significantly increased SIR (1.14, 95% CI 1.08–1.21). For specific cancer types, RNs had an increased SIR for breast (1.28, 95% CI 1.19–1.37), thyroid (1.26, 95% CI 1.10–1.43), lung and mediastinum (1.36, 95% CI 1.13–1.62), and uterine cancers (1.23, 95% CI 1.01–1.49). A decreased SIR was found for cervix (0.48, 95% CI 0.37–0.61) and liver and biliary tract cancers (0.68, 95% CI 0.50–0.90). Pap smear use averaged 5.80 times per person among female RNs aged 35 years or older and 5.50 times per person in the age-matched control group (p = 0.009).

Conclusion

This study found that overall cancer risk was higher among female RNs than general population. For individual cancers, the risks of breast, lung, thyroid and uterine cancer were higher and the risks of cervix and liver cancer were lower than general population. The lower risk of cervical cancer might be partially explained by the increased use of Pap smears in the RNs group. Further large, unbiased population-based prospective studies are needed to investigate the association between nurses and cancer risk and identify the risk factors of cancer in nurses.

Circadian clocks and tumor biology: what is to learn from human skin biopsies?

Some of the components of the circadian molecular clock have been shown to link directly to tumor suppression. Most studies on human tumorous biopsies with consistently down-regulated clock gene expression suggested a protective role for these genes against cancer formation. To highlight some limitations of this hypothesis we review these data in light of recent evidences from animal research, epidemiologic studies, and clinical data on skin tumors. We emphasize the role of circadian rhythmic orchestration in cellular metabolism with a potential in cancer development.

A retrospective cohort study of shift work and risk of cancer-specific mortality in German male chemical workers

OBJECTIVES

Human evidence of carcinogenicity concerning shift work is inconsistent. In a previous study, we observed no elevated risk of total mortality in shift workers followed up until the end of 2006. The present study aimed to investigate cancer-specific mortality, relative to shift work.

METHODS

The cohort consisted of male production workers (14,038 shift work and 17,105 day work), employed at BASF Ludwigshafen for at least 1 year between 1995 and 2005. Vital status was followed from 2000 to 2009. Cause-specific mortality was obtained from death certificates. Exposure to shift work was measured both as a dichotomous and continuous variable. While lifetime job history was not available, job duration in the company was derived from personal data, which was then categorized at the quartiles. Cox proportional hazard model was used to adjust for potential confounders, in which job duration was treated as a time-dependent covariate.

RESULTS

Between 2000 and 2009, there were 513 and 549 deaths among rotating shift and day work employees, respectively. Risks of total and cancer-specific mortalities were marginally lower among shift workers when taking age at entry and job level into consideration and were statistically significantly lower when cigarette smoking, alcohol intake, job duration, and chronic disease prevalence at entry to follow-up were included as explanatory factors. With respect to mortality risks in relation to exposure duration, no increased risks were found in any of the exposure groups after full adjustment and there was no apparent trend suggesting an exposure-response relation with duration of shift work.

CONCLUSIONS

The present analysis extends and confirms our previous finding of no excess risk of mortality associated with work in the shift system employed at BASF Ludwigshafen. More specifically, there is also no indication of an increased risk of mortality due to cancer.

Therapeutic applications of melatonin

Melatonin is a methoxyindole synthesized within the pineal gland. The hormone is secreted during the night and appears to play multiple roles within the human organism. The hormone contributes to the regulation of biological rhythms, may induce sleep, has strong antioxidant action and appears to contribute to the protection of the organism from carcinogenesis and neurodegenerative disorders. At a therapeutic level as well as in prevention, melatonin is used for the management of sleep disorders and jet lag, for the resynchronization of circadian rhythms in situations such as blindness and shift work, for its preventive action in the development of cancer, as additive therapy in cancer and as therapy for preventing the progression of Alzheimer's disease and other neurodegenerative disorders.

Night work and the risk of cancer among men

Night work might influence cancer risk, possibly via suppression of melatonin release. In a population-based case-control study conducted in Montreal, Quebec, Canada, between 1979 and 1985, job histories, including work hours, were elicited from 3,137 males with incident cancer at one of 11 anatomic sites and from 512 controls. Compared with men who never worked at night, the adjusted odds ratios among men who ever worked at night were 1.76 (95% confidence interval (CI): 1.25, 2.47) for lung cancer, 2.03 (95% CI: 1.43, 2.89) for colon cancer, 1.74 (95% CI: 1.22, 2.49) for bladder cancer, 2.77 (95% CI: 1.96, 3.92) for prostate cancer, 2.09 (95% CI: 1.40, 3.14) for rectal cancer, 2.27 (95% CI: 1.24, 4.15) for pancreatic cancer, and 2.31 (95% CI: 1.48, 3.61) for non-Hodgkin's lymphoma. Equivocal evidence or no evidence was observed for cancers of the stomach (odds ratio (OR) = 1.34, 95% CI: 0.85, 2.10), kidney (OR = 1.42, 95% CI: 0.86, 2.35), and esophagus (OR = 1.51, 95% CI: 0.80, 2.84) and for melanoma (OR = 1.04, 95% CI: 0.49, 2.22). There was no evidence of increasing risk with increasing duration of night work, with risks generally being increased across all duration categories. Results suggest that night work may increase cancer risk at several sites among men.

Smoking and risk of skin cancer: a prospective analysis and a meta-analysis

BACKGROUND

The association between smoking and the risk of skin cancer has not been well established.

METHODS

In two large cohorts in the USA, we prospectively examined the risks of melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) among participants grouped according to smoking variables.

RESULTS

Among men, compared with never smokers, ever smokers had a significantly lower risk of melanoma [relative risk (RR) = 0.72; 95% confidence interval (CI): 0.58-0.86]; those who smoked for ≥30 years had an RR of 0.65 (95% CI: 0.48-0.89) (P(trend) = 0.003); those who smoked ≥15 cigarettes per day had an RR of 0.32 (95% CI: 0.13-0.78) (P(trend) = 0.006) and those who smoked for > 45 pack years had an RR of 0.66 (95% CI: 0.45-0.97) (P(trend) = 0.03). Ever smokers also had a slightly lower risk of BCC (RR = 0.94; 95% CI: 0.90-0.98). There was no significant association for SCC (RR = 0.99; 95% CI: 0.89-1.12). In women, no significant association was found for melanoma (RR = 0.96; 95% CI: 0.83-1.10). Compared with never smokers, ever smokers had a slightly higher risk of BCC (RR = 1.06; 95% CI: 1.03-1.08) and a higher risk of SCC (RR = 1.19; 95% CI: 1.08-1.31). A significant inverse association between smoking and melanoma was limited to the head and neck (RR = 0.65; 95% CI: 0.42-0.89).

CONCLUSIONS

Smoking was inversely associated with melanoma risk, especially on the head and neck. Further studies are warranted to investigate the underlying mechanism(s).

Effect of circadian clock mutations on DNA damage response in mammalian cells

The circadian clock is a global regulatory mechanism that confers daily rhythmicity on many biochemical and physiological functions, including DNA excision repair in mammalian organisms. Here, we investigated the effect of the circadian clock on the major DNA damage response pathways by using mouse cell lines mutated in genes encoding proteins in the positive (Bmal1, CLOCK) or negative (Cry 1/2, Per 1/2) arms of the transcription-translation feedback loop that generates the circadian clock. We find that cells mutated in these genes are indistinguishable from wild-type in their response to UV, ionizing radiation and mitomycin C. We conclude that either the majority of DNA damage response reactions are not controlled by the circadian clock or that, even if such a control exists at the organism level, it is supplanted by homeostatic control mechanisms at the cellular level in tissue culture. We suggest that caution must be exercised in extrapolating from experiments in tissue culture to whole animals with respect to the effect of the circadian clock on cellular response to DNA damaging agents.

Shift Work and Cancer: State of Science and Practical Consequences

In 2007, an expert Working Group convened by the IARC Monographs Programme concluded that shift work that involves circadian disruption is probably carcinogenic to humans (Group 2A). We scrutinised the epidemiological basis for this conclusion, with a focus on, but not limited to, breast and prostate cancers. We further considered practical consequences for shift workers in our industry against the background of new findings.

We carried out a literature search including the epidemiological studies cited by IARC and newer available literature on shift work and cancer.

Since the IARC assessment, eleven new studies have emerged, ten of which have already been published, with inconclusive results. Heterogeneity of exposure metrics and study outcomes and emphasis on positive but non-significant results make it difficult to draw general conclusions. Also, several reviews and commentaries, which have been published meanwhile, came to equivocal results. Published evidence is widely seen as suggestive but inconclusive for an adverse association between night work and breast cancer, and limited and inconsistent for cancers at other sites and all cancers combined.

At this point in time it can not be ruled out that shift work including night work may increase the risk for some cancers in those who perform it. However, shift schedules can be organised in ways that minimise the associated health risks, and the risks may be further reduced through the implementation of structured and sustained health promotion programs specifically tailored to the needs of shift workers.

Cancer incidence in professional flight crew and air traffic control officers: disentangling the effect of occupational versus lifestyle exposures

Flight crew are occupationally exposed to several potentially carcinogenic hazards; however, previous investigations have been hampered by lack of information on lifestyle exposures. The authors identified, through the United Kingdom Civil Aviation Authority medical records, a cohort of 16,329 flight crew and 3,165 air traffic control officers (ATCOs) and assembled data on their occupational and lifestyle exposures. Standardised incidence ratios (SIRs) were estimated to compare cancer incidence in each occupation to that of the general population; internal analyses were conducted by fitting Cox regression models. All-cancer incidence was 20-29% lower in each occupation than in the general population, mainly due to a lower incidence of smoking-related cancers [SIR (95% CI) = 0.33 (0.27-0.38) and 0.42 (0.28-0.60) for flight crew and ATCOs, respectively], consistent with their much lower prevalence of smoking. Skin melanoma rates were increased in both flight crew (SIR = 1.87; 95% CI = 1.45-2.38) and ATCOs (2.66; 1.55-4.25), with rates among the former increasing with increasing number of flight hours (p-trend = 0.02). However, internal analyses revealed no differences in skin melanoma rates between flight crew and ATCOs (hazard ratio: 0.78, 95% CI = 0.37-1.66) and identified skin that burns easily when exposed to sunlight (p = 0.001) and sunbathing to get a tan (p = 0.07) as the strongest risk predictors of skin melanoma in both occupations. The similar site-specific cancer risks between the two occupational groups argue against risks among flight crew being driven by occupation-specific exposures. The skin melanoma excess reflects sun-related behaviour rather than cosmic radiation exposure.

Cancer incidence among Nordic airline cabin crew

Airline cabin crew are occupationally exposed to cosmic radiation and jet lag with potential disruption of circadian rhythms. This study assesses the influence of work-related factors in cancer incidence of cabin crew members. A cohort of 8,507 female and 1,559 male airline cabin attendants from Finland, Iceland, Norway and Sweden was followed for cancer incidence for a mean follow-up time of 23.6 years through the national cancer registries. Standardized incidence ratios (SIRs) were defined as ratios of observed and expected numbers of cases. A case-control study nested in the cohort (excluding Norway) was conducted to assess the relation between the estimated cumulative cosmic radiation dose and cumulative number of flights crossing six time zones (indicator of circadian disruption) and cancer risk. Analysis of breast cancer was adjusted for parity and age at first live birth. Among female cabin crew, a significantly increased incidence was observed for breast cancer [SIR 1.50, 95% confidence interval (95% CI) 1.32-1.69], leukemia (1.89, 95% CI 1.03-3.17) and skin melanoma (1.85, 95% CI 1.41-2.38). Among men, significant excesses in skin melanoma (3.00, 95% CI 1.78-4.74), nonmelanoma skin cancer (2.47, 95% CI 1.18-4.53), Kaposi sarcoma (86.0, 95% CI 41.2-158) and alcohol-related cancers (combined SIR 3.12, 95% CI 1.95-4.72) were found. This large study with complete follow-up and comprehensive cancer incidence data shows an increased incidence of several cancers, but according to the case-control analysis, excesses appear not to be related to the cosmic radiation or circadian disruptions from crossing multiple time zones.

New perspectives in melatonin uses

This review summarizes the metabolism, secretion, regulation and sites of action of melatonin. An updated description of the melatonin receptors, including their signal transduction mechanisms, distribution and characterization of receptor genes, is given. Special emphasis is focused on the clinical aspects and potential uses of melatonin in the sleep-wake rhythms, in the immune function, in cancer therapy, in neuroprotection against oxidative damage and antioxidant activities in different tissues. Finally, combined effects of melatonin with other drugs are discussed.

The efficacy and safety of melatonin in concurrent chemotherapy or radiotherapy for solid tumors: a meta-analysis of randomized controlled trials

BACKGROUND

Recently, melatonin has been associated with cancer both in vitro and in vivo. However, the value of melatonin in the treatment of cancer remains disputable. Hence, we performed a systematic review of randomized controlled trials (RCTs) of melatonin in solid tumor cancer patients and observed its effect on tumor remission, 1-year survival, and side effects due to radiochemotherapy.

METHODS

An electronic search was conducted using the databases Pubmed, Medline, EMBASE, Cochrane library, and CNKI, from inception to November 2011. Trials using melatonin as adjunct treatment concurrent with chemotherapy or radiotherapy for cancer were included. Pooled relative risk (RR) for the tumor remission, 1-year survival, and radiochemotherapy-related side effects were calculated using the software Revman 5.0.

RESULTS

The search strategy identified 8 eligible RCTs (n = 761), all of which studied solid tumor cancers. The dosage of melatonin used in the 8 included RCTs was 20 mg orally, once a day. Melatonin significantly improved the complete and partial remission (16.5 vs. 32.6%; RR = 1.95, 95% CI, 1.49-2.54; P < 0.00001) as well as 1-year survival rate (28.4 vs. 52.2%; RR = 1.90; 95% CI, 1.28-2.83; P = 0.001), and dramatically decreased radiochemotherapy-related side effects including thrombocytopenia (19.7 vs. 2.2%; RR = 0.13; 95% CI, 0.06-0.28; P < 0.00001), neurotoxicity (15.2 vs. 2.5%; RR = 0.19; 95% CI, 0.09-0.40; P < 0.0001), and fatigue (49.1 vs. 17.2%; RR = 0.37; 95% CI, 0.28-0.48; P < 0.00001). Effects were consistent across different types of cancer. No severe adverse events were reported.

CONCLUSIONS

Melatonin as an adjuvant therapy for cancer led to substantial improvements in tumor remission, 1-year survival, and alleviation of radiochemotherapy-related side effects.

No association between Parkinson disease alleles and the risk of melanoma

BACKGROUND

Recent data showed that melanoma was more common among patients with Parkinson disease than individuals without Parkinson disease and vice versa. It has been hypothesized that these two diseases may share common genetic and environmental risk factors.

METHODS

We evaluated the association between single-nucleotide polymorphisms (SNP) selected on the basis of recent genome-wide association studies (GWAS) on Parkinson disease risk and the risk of melanoma using 2,297 melanoma cases and 6,651 controls.

RESULTS

The Parkinson disease SNP rs156429 in the chromosome 7p15 region was nominally associated with melanoma risk with P value of 0.04, which was not significant after the Bonferroni correction for multiple comparisons. No association was observed between the remaining 31 Parkinson disease SNPs and the risk of melanoma. The genetic score based on the number of Parkinson disease risk allele was not associated with melanoma risk [OR for the highest genetic score quartile (30-35) vs. the lowest (15-20), 1.13, 95% confidence interval (CI), 0.47-2.70].

CONCLUSION

The Parkinson disease SNPs identified in published GWAS do not seem to play an important role in melanoma development.

IMPACT

The Parkinson disease susceptibility loci discovered by GWAS contribute little to the observed epidemiologic association between the Parkinson disease and melanoma.

Is shift work making your patient sick? Emerging theories and therapies for treating shift work disorder

"Shift work" is a term that applies to a wide array of nontraditional work schedules. Shift work disorder (SWD) is a circadian rhythm sleep disorder experienced by a subset of shift workers that is characterized by excessive sleepiness during work and/or insomnia during scheduled sleep times. It is estimated to affect up to 2 million Americans, and is associated with increased morbidity and mortality from metabolic risk factors, cardiovascular and gastrointestinal diseases, depression, accidents, and some kinds of cancers. Patient history is all that is needed to make a diagnosis with the International Classification of Sleep Disorders-Second Edition criteria as described herein. Circadian rhythm disorders, in which an underlying misalignment of circadian rhythm with the sleep-wake cycle occurs, may be treated by behavioral and pharmacologic approaches, including the use of hypnotics to improve the duration of sleep. However, evidence is limited with these approaches in patients diagnosed with SWD. Other treatment options may include pharmacologic interventions such as modafinil and armodafinil, which have shown efficacy in this population. Combined therapy can reduce insomnia and excessive sleepiness, and improve attention and alertness during work shifts and the subsequent commute home.