Obesity and intermittent hypoxia increase tumor growth in a mouse model of sleep apnea

Linking obstructive sleep apnoea and lung cancer: a further step down the road

There are various pathophysiological pathways linking obstructive sleep apnoea and lung cancer https://bit.ly/48qtqOO.

Lung Micrometastases Display ECM Depletion and Softening While Macrometastases Are 30-Fold Stiffer and Enriched in Fibronectin

Mechanical changes in tumors have long been linked to increased malignancy and therapy resistance and attributed to mechanical changes in the tumor extracellular matrix (ECM). However, to the best of our knowledge, there have been no mechanical studies on decellularized tumors. Here, we studied the biochemical and mechanical progression of the tumor ECM in two models of lung metastases: lung carcinoma (CAR) and melanoma (MEL). We decellularized the metastatic lung sections, measured the micromechanics of the tumor ECM, and stained the sections for ECM proteins, proliferation, and cell death markers. The same methodology was applied to MEL mice treated with the clinically approved anti-fibrotic drug nintedanib. When compared to healthy ECM (~0.40 kPa), CAR and MEL lung macrometastases produced a highly dense and stiff ECM (1.79 ± 1.32 kPa, CAR and 6.39 ± 3.37 kPa, MEL). Fibronectin was overexpressed from the early stages (~118%) to developed macrometastases (~260%) in both models. Surprisingly, nintedanib caused a 4-fold increase in ECM-occupied tumor area (5.1 ± 1.6% to 18.6 ± 8.9%) and a 2-fold in-crease in ECM stiffness (6.39 ± 3.37 kPa to 12.35 ± 5.74 kPa). This increase in stiffness strongly correlated with an increase in necrosis, which reveals a potential link between tumor hypoxia and ECM deposition and stiffness. Our findings highlight fibronectin and tumor ECM mechanics as attractive targets in cancer therapy and support the need to identify new anti-fibrotic drugs to abrogate aberrant ECM mechanics in metastases.

Differential Impact of Intermittent vs. Sustained Hypoxia on HIF-1, VEGF and Proliferation of HepG2 Cells

Obstructive sleep apnea (OSA) is an emerging risk factor for cancer occurrence and progression, mainly mediated by intermittent hypoxia (IH). Systemic IH, a main landmark of OSA, and local sustained hypoxia (SH), a classical feature at the core of tumors, may act separately or synergistically on tumor cells. Our aim was to compare the respective consequences of intermittent and sustained hypoxia on HIF-1, endothelin-1 and VEGF expression and on cell proliferation and migration in HepG2 liver tumor cells. Wound healing, spheroid expansion, proliferation and migration were evaluated in HepG2 cells following IH or SH exposure. The HIF-1α, endothelin-1 and VEGF protein levels and/or mRNA expression were assessed, as were the effects of HIF-1 (acriflavine), endothelin-1 (macitentan) and VEGF (pazopanib) inhibition. Both SH and IH stimulated wound healing, spheroid expansion and proliferation of HepG2 cells. HIF-1 and VEGF, but not endothelin-1, expression increased with IH exposure but not with SH exposure. Acriflavine prevented the effects of both IH and SH, and pazopanib blocked those of IH but not those of SH. Macitentan had no impact. Thus, IH and SH stimulate hepatic cancer cell proliferation via distinct signaling pathways that may act synergistically in OSA patients with cancer, leading to enhanced tumor progression.

Association between obstructive sleep apnoea and cancer: a cross-sectional, population-based study of the DISCOVERY cohort

OBJECTIVES

Nocturnal hypoxia in obstructive sleep apnoea (OSA) is a potential risk factor for cancer. We aimed to investigate the association between OSA measures and cancer prevalence in a large national patient cohort.

DESIGN

Cross-sectional study.

SETTINGS

44 sleep centres in Sweden.

PARTICIPANTS

62 811 patients from the Swedish registry for positive airway pressure (PAP) treatment in OSA, linked to the national cancer registry and national socioeconomic data (the course of DIsease in patients reported to Swedish CPAP, Oxygen and VEntilator RegistrY cohort).

OUTCOME MEASURES

After propensity score matching for relevant confounders (anthropometric data, comorbidities, socioeconomic status, smoking prevalence), sleep apnoea severity, measured as Apnoea-Hypopnoea Index (AHI) or Oxygen Desaturation Index (ODI), were compared between those with and without cancer diagnosis up to 5 years prior to PAP initiation. Subgroup analysis for cancer subtype was performed.

RESULTS

OSA patients with cancer (n=2093) (29.8% females, age 65.3 (SD 10.1) years, body mass index 30 (IQR 27-34) kg/m²) had higher median AHI (n/hour) (32 (IQR 20-50) vs 30 (IQR 19-45), n/hour, p=0.002) and median ODI (n/hour) (28 (IQR 17-46) vs 26 (IQR 16-41), p<0.001) when compared with matched OSA patients without cancer. In subgroup analysis, ODI was significantly higher in OSA patients with lung cancer (N=57; 38 (21-61) vs 27 (16-43), p=0.012)), prostate cancer (N=617; 28 (17-46) vs 24, (16-39)p=0.005) and malignant melanoma (N=170; 32 (17-46) vs 25 (14-41),p=0.015).

CONCLUSIONS

OSA mediated intermittent hypoxia was independently associated with cancer prevalence in this large, national cohort. Future longitudinal studies are warranted to study the potential protective influence of OSA treatment on cancer incidence.

Experimental Models to Study End-Organ Morbidity in Sleep Apnea: Lessons Learned and Future Directions

Sleep apnea (SA) is a very prevalent sleep breathing disorder mainly characterized by intermittent hypoxemia and sleep fragmentation, with ensuing systemic inflammation, oxidative stress, and immune deregulation. These perturbations promote the risk of end-organ morbidity, such that SA patients are at increased risk of cardiovascular, neurocognitive, metabolic and malignant disorders. Investigating the potential mechanisms underlying SA-induced end-organ dysfunction requires the use of comprehensive experimental models at the cell, animal and human levels. This review is primarily focused on the experimental models employed to date in the study of the consequences of SA and tackles 3 different approaches. First, cell culture systems whereby controlled patterns of intermittent hypoxia cycling fast enough to mimic the rates of episodic hypoxemia experienced by patients with SA. Second, animal models consisting of implementing realistic upper airway obstruction patterns, intermittent hypoxia, or sleep fragmentation such as to reproduce the noxious events characterizing SA. Finally, human SA models, which consist either in subjecting healthy volunteers to intermittent hypoxia or sleep fragmentation, or alternatively applying oxygen supplementation or temporary nasal pressure therapy withdrawal to SA patients. The advantages, limitations, and potential improvements of these models along with some of their pertinent findings are reviewed.

The Combination of Sleep Disorders and Depression Significantly Increases Cancer Risk: A Nationwide Large-Scale Population-Based Study

Introduction: Sleep disorders, depression, and cancer have become increasingly prevalent worldwide. However, it is unknown whether coexistence of sleep disorders and depression influences the risk of cancer development. Therefore, we conducted a nationwide population-based study to examine this association among patients in Taiwan. Materials and Methods: A total of 105,071 individuals diagnosed with cancer and 420,284 age- and sex-matched patients without a diagnosis of cancer between 2000 and 2015 were identified from Taiwan’s National Health Insurance Research Database. The underlying chronic diseases of patients that may developed cancer were gathered and studied as the predictor. A multivariate Cox proportional odds model was used to estimate the crude and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) to estimate the interaction effect between sleep disorders and depression on the risk of cancer. Results: After adjusting for age, sex, comorbidities, and other covariates, the cancer group was associated with increased exposure to sleep disorders than the non-cancer group (aOR = 1.440, 95% CI = 1.392−1.489, p < 0.001). In addition, patients with both sleep disorders and depression were at an even higher risk for cancer than the general population (aOR = 6.857, p < 0.001). Conclusions: This retrospective cohort study shows that patients with both sleep disorders and depression are at a higher risk of cancer. Clinically, a meticulous cancer risk evaluation is recommended for patients with both sleep disorders and depression.

Chronic intermittent hypoxia, a hallmark of obstructive sleep apnea, promotes 4T1 breast cancer development through endothelin-1 receptors

The association between obstructive sleep apnea (OSA) and cancer is still debated and data are scarce regarding the link between OSA and breast cancer progression. Since conclusive epidemiological studies require large sample sizes and sufficient duration of exposure before incident cancer occurrence, basic science studies represent the most promising approach to appropriately address the topic. Here we assessed the impact of intermittent hypoxia (IH), the major hallmark of OSA, on the development of breast cancer and explored the specific involvement of the endothelin signaling pathway. Original in vitro and in vivo models were used where 3D-spheroids or cultures of murine 4T1 breast cancer cells were submitted to IH cycles, and nude NMRI mice, orthotopically implanted with 4T1 cells, were submitted to chronic IH exposure before and after implantation. The role of the endothelin-1 in promoting cancer cell development was investigated using the dual endothelin receptor antagonist, macitentan. In vitro exposure to IH significantly increased 4T1 cell proliferation and migration. Meta-analysis of 4 independent in vivo experiments showed that chronic IH exposure promoted tumor growth, assessed by caliper measurement (overall standardized mean difference: 1.00 [0.45-1.55], p < 0.001), bioluminescence imaging (1.65 [0.59-2.71]; p < 0.01) and tumor weight (0.86 [0.31-1.41], p < 0.01), and enhanced metastatic pulmonary expansion (0.77 [0.12-1.42]; p = 0.01). Both in vitro and in vivo tumor-promoting effects of IH were reversed by macitentan. Overall, these findings demonstrate that chronic intermittent hypoxia exposure promotes breast cancer growth and malignancy and that dual endothelin receptor blockade prevents intermittent hypoxia-induced tumor development.

Sleep-Disordered Breathing in Newly Diagnosed Patients of Lung Cancer

Sleep-disordered breathing (SDB) is highly prevalent in patients with cancer and affects their prognosis. However, data on SDB in lung cancer patients are lacking, and few studies have conducted level I polysomnography (PSG) in this patient population. This study aimed to measure SDB in newly diagnosed lung cancer patients at the sleep clinic of a tertiary respiratory institute in New Delhi, India, for eight months. This study included 30 patients. Participants received a clinical examination, completed a sleep questionnaire, and then underwent overnight PSG. We scored sleep parameters according to the American Academy of Sleep Medicine guidelines. Both descriptive and inferential statistics were used to analyze the data. We used univariate analysis with chi-square testing, and p<0.05 was considered significant. SDB and obstructive sleep apnea (OSA) were found in 66.6% and 56.6% of patients, respectively. Mild, moderate, and severe OSA were seen in 26.6%, 16.6%, and 13.3% of patients, respectively. Nocturnal oxygen desaturation (NOD) or NOD90 (i.e., when >30% of sleep time was spent with oxygen saturation levels <90%) was seen in 13.3% of patients. Adenocarcinoma was the most common histological variant of cancer. Tumor-node-metastasis staging was significantly associated with the presence of OSA (p=0.045). Lung cancer patients should receive routine PSG to identify and manage patients with SDB, especially given that symptoms of SDB such as easy fatigability and non-refreshing sleep are overlooked as symptoms of lung cancer. Proper management of SDB or OSA would help improve patients' quality of life and improve their overall prognosis.

Highlights of the ERS Lung Science Conference and Sleep and Breathing Conference 2021 and the new ECMC members

This article provides a brief description of some of the most remarkable sessions of the @EuroRespSoc Lung Science Conference and the Sleep and Breathing Conference 2021 and presents the new incoming members of the ECMC (@EarlyCareerERS) https://bit.ly/2RSDP40.

Heterogeneity of Melanoma Cell Responses to Sleep Apnea-Derived Plasma Exosomes and to Intermittent Hypoxia

Obstructive sleep apnea (OSA) is associated with increased cutaneous melanoma incidence and adverse outcomes. Exosomes are secreted by most cells, and play a role in OSA-associated tumor progression and metastasis. We aimed to study the effects of plasma exosomes from OSA patients before and after adherent treatment with continuous positive airway pressure (CPAP) on melanoma cells lines, and also to identify exosomal miRNAs from melanoma cells exposed to intermittent hypoxia (IH) or normoxia. Plasma-derived exosomes were isolated from moderate-to-severe OSA patients before (V1) and after (V2) adherent CPAP treatment for one year. Exosomes were co-incubated with three3 different melanoma cell lines (CRL 1424; CRL 1619; CRL 1675) that are characterized by genotypes involving different mutations in BRAF, STK11, CDKN2A, and PTEN genes to assess the effect of exosomes on cell proliferation and migration, as well as on pAMK activity in the presence or absence of a chemical activator. Subsequently, CRL-1424 and CRL-1675 cells were exposed to intermittent hypoxia (IH) and normoxia, and exosomal miRNAs were identified followed by GO and KEG pathways and gene networks. The exosomes from these IH-exposed melanoma cells were also administered to THP1 macrophages to examine changes in M1 and M2 polarity markers. Plasma exosomes from V1 increased CRL-1424 melanoma cell proliferation and migration compared to V2, but not the other two cell lines. Exposure to CRL-1424 exosomes reduced pAMPK/tAMPK in V1 compared to V2, and treatment with AMPK activator reversed the effects. Unique exosomal miRNAs profiles were identified for CRL-1424 and CRL-1675 in IH compared to normoxia, with six miRNAs being regulated and several KEGG pathways were identified. Two M1 markers (CXCL10 and IL6) were significantly increased in monocytes when treated with exosomes from IH-exposed CRL-1424 and CRL-1625 cells. Our findings suggest that exosomes from untreated OSA patients increase CRL-1424 melanoma malignant properties, an effect that is not observed in two other melanoma cell lines. Exosomal cargo from CRL-1424 cells showed a unique miRNA signature compared to CRL-1675 cells after IH exposures, suggesting that melanoma cells are differentially susceptible to IH, even if they retain similar effects on immune cell polarity. It is postulated that mutations in STK-11 gene encoding for the serine/threonine kinase family that acts as a tumor suppressor may underlie susceptibility to IH-induced metabolic dysfunction, as illustrated by CRL-1424 cells.

Obstructive sleep apnea and the risk of mortality in patients with lung cancer: a meta-analysis

PURPOSE

Prior reports have examined the relationship between obstructive sleep apnea (OSA) and the mortality rate of lung cancer. However, the findings remain controversial. The present meta-analysis was performed to assess the relationship between OSA and increased risk of mortality in patients with lung cancer.

METHODS

PubMed, Web of Science, and Embase were systematically searched for the correlative studies. Data were analyzed and pooled to evaluate odds ratios (ORs) of lung cancer mortality related to OSA.

RESULTS

From 249 identified studies, 3 met inclusion criteria and were analyzed, including 67 patients with lung cancer and comorbid OSA and 45 patients with lung cancer and no OSA. The meta-analysis indicated that OSA was not significantly correlated with mortality rate in lung cancer (OR = 2.005, 95% CI = 0.703 to 5.715, z = 1.30, p = 0.193). There was no significant publication bias according to Begg's tests (p = 0.296) and Egger's tests (p = 0.097).

CONCLUSION

This meta-analysis suggests that OSA is not significantly correlated with the mortality rate in lung cancer.

Intermittent hypoxia induces tumor immune escape in murine S180 solid tumors via the upregulation of TGF-β1 in mice

PURPOSE

Studies have shown that intermittent hypoxia (IH) alters host immune functions and promotes tumor growth. However, the relevant mechanisms of these effects have not been completely elucidated. We hypothesized that IH promotes the growth of tumors by changing cytokine levels in the tumor microenvironment and inducing immune escape.

METHODS

Sarcoma-180 (S180) solid tumor cells were injected into the right flank of Kunming mice. The mice were then randomly divided into the IH and room air (RA) groups. The mice were euthanized 2 weeks after IH exposure, and the weight of tumor tissues was measured. Next, IL-6, IL-17, IL-10, and TNF-α levels in tumor tissues were measured via enzyme linked immunosorbent assay (ELISA), and hypoxia inducible factor-1α (HIF-1α) and transforming growth factor β1 (TGF-β1) expressions were examined through Western blot analysis.

RESULTS

Two weeks of IH exposure significantly accelerated the growth of S180 solid tumors. Western blot analysis results showed that the expression levels of HIF-1α and TGF-β1 in S180 tumors in the IH group were significantly upregulated compared with those in the RA group. ELISA results showed that compared with the RA group, the IH group had significantly increased TNF-α and IL-10 (P < 0.05) and significantly decreased IL-17 (P < 0.05).

CONCLUSION

IH might promote the growth of S180 solid tumors by inhibiting the antitumor immune response and inducing tumor immune escape via the upregulation of TGF-β1.

Lung cancer aggressiveness in an intermittent hypoxia murine model of postmenopausal sleep apnea

OBJECTIVE

Intermittent hypoxia (IH)-a hallmark of obstructive sleep apnea (OSA)-enhances lung cancer progression in mice via altered host immune responses that are also age and sex-dependent. However, the interactions of menopause with IH on tumor malignant properties remain unexplored. Here, we aimed to investigate lung cancer outcomes in the context of ovariectomy (OVX)-induced menopause in a murine model of OSA.

METHODS

Thirty-four female mice (C57BL/6, 12-week-old) were subjected to bilateral OVX or to Sham intervention. Six months after surgery, mice were pre-exposed to either IH or room air (RA) for 2 weeks. Then, 10 lung carcinoma (LLC1) cells were injected subcutaneously in the left flank, with IH or RA exposures continued for 4 weeks. Tumor weight, tumor invasion, and spontaneous lung metastases were assessed. Tumor-associated macrophages (TAMs) were isolated and subjected to flow cytometry polarity evaluation along with assessment of TAMs modulation of LLC1 proliferation in vitro. To determine the effect of IH and OVX on each experimental variable, a two-way analysis of variance was performed.

RESULTS

IH and OVX promoted a similar increase in tumor growth (∼2-fold; P = 0.05 and ∼1.74-fold; P < 0.05, respectively), and OVX-IH further increased it. Regarding lung metastasis, the concurrence of OVX in mice exposed to IH enhanced the number of metastases (23.7 ± 8.0) in comparison to those without OVX (7.9 ± 2.8; P < 0.05). The pro-tumoral phenotype of TAMS, assessed as M2/M1 ratio, was increased in OVX (0.06 ± 0.01; P < 0.01) and IH (0.06 ± 0.01; P < 0.01) compared with sham/RA conditions (0.14 ± 0.03). The co-culture of TAMS with naive LLC1 cells enhanced their proliferation only under IH.

CONCLUSION

In female mice, both the IH that is characteristically present in OSA and OVX as a menopause model emerge as independent contributors that promote lung cancer aggressiveness and seemingly operate through alterations in the host immune response.

Associations of self-reported obstructive sleep apnea with total and site-specific cancer risk in older women: a prospective study

BACKGROUND AND OBJECTIVES

Chronic intermittent hypoxia resulting from obstructive sleep apnea (OSA) may activate multiple carcinogenic pathways and lead to cancer development.

METHODS

We prospectively examined the association between OSA and cancer risk among 65,330 women in the Nurses' Health Study who were free of cancer in 2008 (mean age: 73.3 years). Incident cancer diagnoses were collected until 2016 and confirmed by pathology reports. Clinically diagnosed OSA was self-reported in 2008 and updated in 2012. We used time-dependent Cox regression to estimate hazard ratios (HR) for the associations of OSA with total and site-specific cancer risk.

RESULTS

We documented 5,257 incident cancer diagnoses during follow-up. In the age-adjusted model, OSA was associated with a 15% (95% CI: 1.03, 1.29) increase in total cancer risk. The association became nonsignificant after adjustment for multiple cancer risk factors (HR: 1.08; 95% CI: 0.96, 1.21). When examining cancer risk by site, OSA was associated with significantly increased risk for lung (fully adjusted HR: 1.52; 95% CI: 1.07, 2.17), bladder (fully adjusted HR: 1.94; 95% CI: 1.12, 3.35), and thyroid cancer (fully adjusted HR: 2.06; 95% CI: 1.01, 4.22) and possibly increased risk for kidney cancer (fully adjusted HR: 1.59; 95% CI: 0.84, 3.01). When grouping cancer sites by risk factor profiles, OSA was positively associated with smoking-related cancers (fully adjusted HR: 1.37; 95% CI: 1.11, 1.67), and this association was stronger in never smokers than ever smokers.

CONCLUSION

While OSA was not independently associated with overall cancer risk in older women, significant associations were observed for smoking-related cancers, especially in nonsmokers.

Obstructive Sleep Apnea and Incident Cancer: A Large Retrospective Multicenter Clinical Cohort Study

BACKGROUND

To examine the association between the severity of obstructive sleep apnea (OSA) and nocturnal hypoxemia with incident cancer.

METHODS

This was a multicenter retrospective clinical cohort study using linked clinical and provincial health administrative data on consecutive adults who underwent a diagnostic sleep study between 1994 and 2017 in four academic hospitals (Canada) who were free of cancer at baseline. Cancer status was derived from the Ontario Cancer Registry. Cox cause-specific regressions were utilized to address the objective and to calculate the 10-year absolute risk difference (ARD) in the marginal probability of incident cancer and the number needed to harm (NNH).

RESULTS

Of 33,997 individuals considered, 33,711 with no missing OSA severity were included: median age, 50 years; 58% male; and 23% with severe OSA (apnea-hypopnea index >30). Of the 18,458 individuals with information on sleep time spent with oxygen saturation (SaO₂) <90%, 5% spent >30% of sleep with SaO₂ <90% (severe nocturnal hypoxemia). Over a median of 7 years, 2,498 of 33,711 (7%) individuals developed cancer, with an incidence rate of 10.3 (10.0-10.8) per 1,000 person-years. Controlling for confounders, severe OSA was associated with a 15% increased hazard of developing cancer compared with no OSA (HR = 1.15, 1.02-1.30; ARD = 1.28%, 0.20-2.37; and NNH = 78). Severe hypoxemia was associated with about 30% increased hazard (HR = 1.32, 1.08-1.61; ARD = 2.38%, 0.47-4.31; and NNH = 42).

CONCLUSIONS

In a large cohort of individuals with suspected OSA free of cancer at baseline, the severity of OSA and nocturnal hypoxemia was independently associated with incident cancer.

IMPACT

These findings suggest the need for more targeted cancer risk awareness in individuals with OSA.

Hypoxia induced factor-1α levels in patients undergoing adenoidectomy

Among  the most common causes of nasal congestion in childhood is adenoid hypertrophy (AH) which leads to hypoxia. In this study, we studied plasma concentrations of hypoxia induced factor-1α (HIF-1α) in children undergoing adenoidectomy. The study included a total of 86 participants: 39 patients with AH and 47 healthy individuals. Serum HIF-1α levels (ng/mL) were measured by ELISA. HIF-1α concentrations were compared to the adenoid-nasopharyngeal ratio (ANR) of patients with AH, as recorded in the medical records. We found significantly higher concentrations of HIF-1α (0.30 ± 0.47 ng/mL) in patients with AH as compared to healthy controls (0.24 ± 0.07 ng/mL, p = .011). HIF-1α levels were not significantly different regarding gender between patients with AH (p = .77) and in the control group (p = .97). In patients with AH, there was a moderately significant positive correlation between HIF-1α levels and Hb (p = .000), (correlation coefficient r = 0.542). There was a positive correlation between HIF-1α and ANR in patients with AH (p = .005, r = 0.439). This study indicates that AH increases HIF-1α levels. We also observed a moderately significant positive correlation between HIF-1α and ANR in patients with AH. HIF-1α levels are a potential biomarker for hypoxia in patients with AH.

Sleep Apnoea Adverse Effects on Cancer: True, False, or Too Many Confounders?

Obstructive sleep apnoea (OSA) is a prevalent disorder associated with increased cardiovascular, metabolic and neurocognitive morbidity. Recently, an increasing number of basic, clinical and epidemiological reports have suggested that OSA may also increase the risk of cancer, and adversely impact cancer progression and outcomes. This hypothesis is convincingly supported by biological evidence linking certain solid tumours and hypoxia, as well as by experimental studies involving cell and animal models testing the effects of intermittent hypoxia and sleep fragmentation that characterize OSA. However, the clinical and epidemiological studies do not conclusively confirm that OSA adversely affects cancer, even if they hold true for specific cancers such as melanoma. It is likely that the inconclusive studies reflect that they were not specifically designed to test the hypothesis or because of the heterogeneity of the relationship of OSA with different cancer types or even sub-types. This review critically focusses on the extant basic, clinical, and epidemiological evidence while formulating proposed directions on how the field may move forward.

Role of the Cyclooxygenase Pathway in the Association of Obstructive Sleep Apnea and Cancer

The objective of this review is to examine the findings that link obstructive sleep apnea (OSA) with cancer and the role played by the cyclooxygenase (COX) pathway in this association. Epidemiological studies in humans suggest a link between OSA and increased cancer incidence and mortality. Studies carried out in animal models have shown that intermittent hypoxia (IH) induces changes in several signaling pathways involved in the regulation of host immunological surveillance that results in tumor establishment and invasion. IH induces the expression of cyclooxygenase 2 (COX-2) that results in an increased synthesis of prostaglandin E2 (PGE₂). PGE₂ modulates the function of multiple cells involved in immune responses including T lymphocytes, NK cells, dendritic cells, macrophages, and myeloid-derived suppressor cells. In a mouse model blockage of COX-2/PGE₂ abrogated the pro-oncogenic effects of IH. Despite the fact that aspirin inhibits PGE₂ production and prevents the development of cancer, none of the epidemiological studies that investigated the association of OSA and cancer included aspirin use in the analysis. Studies are needed to investigate the regulation of the COX-2/PGE₂ pathway and PGE₂ production in patients with OSA, to better define the role of this axis in the physiopathology of OSA and the potential role of aspirin in preventing the development of cancer.

Obesity attenuates the effect of sleep apnea on active TGF-ß1 levels and tumor aggressiveness in patients with melanoma

Active transforming growth factor-β1 (TGF-β1), a cytokine partially regulated by hypoxia and obesity, has been related with poor prognosis in several tumors. We determine whether obstructive sleep apnea (OSA) increases serum levels of active TGF-β1 in patients with cutaneous melanoma (CM), assess their relationship with melanoma aggressiveness and analyze the factors related to TGF-β1 levels in obese and non-obese OSA patients. In a multicenter observational study, 290 patients with CM were underwent sleep studies. TGF-β1 was increased in moderate-severe OSA patients vs. non-OSA or mild OSA patients with CM. In OSA patients, TGF-β1 levels correlated with mitotic index, Breslow index and melanoma growth rate, and were increased in presence of ulceration or higher Clark levels. In CM patients, OSA was associated with higher TGF-β1 levels and greater melanoma aggressiveness only in non-obese subjects. An in vitro model showed that IH-induced increases of TGF-β1 expression in melanoma cells is attenuated in the presence of high leptin levels. In conclusion, TGF-β1 levels are associated with melanoma aggressiveness in CM patients and increased in moderate-severe OSA. Moreover, in non-obese patients with OSA, TGF-β1 levels correlate with OSA severity and leptin levels, whereas only associate with leptin levels in obese OSA patients.

Obstructive sleep apnea and cancer: a complex relationship

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) has been recognized as a risk factor for cancer mainly through hypoxia, based on studies that did not distinguish among cancer types. The purpose of this review is to discuss the most recent data on epidemiology and pathophysiology of the OSA-cancer association.

RECENT FINDINGS

According to epidemiological studies, OSA may have different influences on each type of cancer, either increasing or decreasing its incidence and aggressiveness. Time spent with oxygen saturation below 90% appears the polysomnographic variable most strongly associated with unfavorable effects on cancer. Experimental studies support the role of hypoxia as an important risk factor for cancer growth and aggressiveness, especially when it shows an intermittent pattern. These effects are largely mediated by the hypoxia-inducible factor, which controls the synthesis of molecules with effects on inflammation, immune surveillance and cell proliferation. Sleep fragmentation participates in increasing cancer risk. Modulating effects of age remain controversial.

SUMMARY

Effects of OSA on cancer may largely vary among neoplastic diseases, both in their magnitude and direction. The worse risk associated with intermittent rather than persistent hypoxia, and the effects of OSA therapy on cancer natural history are still poorly known, and deserve new careful studies.

The Association of Sleep Disorders, Obesity and Sleep-Related Hypoxia with Cancer

BACKGROUND

Sleep disorders have emerged as potential cancer risk factors.

OBJECTIVE

This review discusses the relationships between sleep, obesity, and breathing disorders with concomitant risks of developing cancer.

RESULTS

Sleep disorders result in abnormal expression of clock genes, decreased immunity, and melatonin release disruption. Therefore, these disorders may contribute to cancer development. Moreover, in sleep breathing disorder, which is frequently experienced by obese persons, the sufferer experiences intermittent hypoxia that may stimulate cancer cell proliferation.

DISCUSSION

During short- or long- duration sleep, sleep-wake rhythm disruption may occur. Insomnia and obstructive sleep apnea increase cancer risks. In short sleepers, an increased risk of stomach cancer, esophageal squamous cell cancer, and breast cancer was observed. Among long sleepers (>9 hours), the risk of some hematologic malignancies is elevated.

CONCLUSION

Several factors including insomnia, circadian disruption, obesity, and intermittent hypoxia in obstructive sleep apnea are contributing risk factors for increased risk of several types of cancers. However, further studies are needed to determine the more significant of these risk factors and their interactions.

Intrahepatic Expression of Fatty Acid Translocase CD36 Is Increased in Obstructive Sleep Apnea

Nocturnal intermittent hypoxia (IH) featuring obstructive sleep apnea (OSA) dysregulates hepatic lipid metabolism and might contribute to the development of non-alcoholic fatty liver disease (NAFLD) observed in OSA patients. However, further research is required to better understanding the molecular mechanisms underlying IH-induced hepatic lipid accumulation. Therefore, the aim of the present study was to determine the effects of OSA on hepatic CD36 expression and the impact of IH by using a mouse model of OSA. Histological analysis, lipid content and CD36 expression were assessed in livers from subjects who underwent liver biopsy and polygraphic study during sleep, and in livers from mice submitted to chronic IH mimicking OSA. Among those who presented OSA features, NAFLD were significantly more frequent than in control subjects with normal respiratory function (77.8 vs. 36.4%, respectively), and showed more severe liver disease. Interestingly, CD36 expression was significantly overexpressed within the liver of OSA patients with respect to controls, and a significant positive correlation was observed between hepatic levels of CD36 and the values of two well-known respiratory parameters that characterized OSA: apnea/hypopnea index (AHI) and oxygen desaturation index (ODI). Moreover, hepatic lipid accumulation as well as induction of hepatic lipogenic genes, and CD36 mRNA and protein expression were significantly higher in livers from mice exposed to IH conditions for 8 weeks than in their corresponding littermates. This study provides novel evidence that IH featuring OSA could contribute to NAFLD setup partly by upregulating hepatic CD36 expression.

The Association of Sleep Apnea and Cancer in Veterans

Objective

To test the association between preexisting obstructive sleep apnea (OSA) and subsequent cancer in a large long-term cohort of veteran patients.

Study Design

Retrospective matched cohort study.

Setting

The Veterans Affairs Health Care System.

Subjects and Methods

All veteran patients diagnosed with OSA between 1993 and 2013 by International Classification of Diseases, Ninth Revision ( ICD-9) codes in any Veterans Affairs facility and veteran patients without an OSA diagnosis, matched to patients with OSA by age and index year. Cancer diagnoses were identified by ICD-9 codes for the time period at least 2 years after OSA diagnosis or index date. We tested the association between OSA and cancer using multivariate Cox regression with time since cohort entry as the time axis, adjusting for potential confounders.

Results

The cohort included 1,377,285 patients (726,008 with and 651,277 without an OSA diagnosis) with mean age of 55 years, predominantly male (94%), a minority obese (32%), and median follow-up of 7.4 years (range, 2.0-25.2). The proportion of patients diagnosed with cancer was higher in those with vs without an OSA diagnosis (8.3% vs 3.6%; mean difference 4.8%; 95% confidence interval [CI], 4.7%-4.8%; P < .001). After adjusting for age, sex, year of cohort entry, smoking status, alcohol use, obesity, and comorbidity, the hazard of incident cancer was nearly double in patients with vs without an OSA diagnosis (hazard ratio, 1.97; 95% CI, 1.94-2.00; P < .001).

Conclusion

Preexisting OSA was strongly associated with subsequent cancer in this veteran cohort, independent of several known cancer risk factors. These findings suggest that OSA may be a strong, independent risk factor for subsequent cancer development.

Effects of Far-infrared Ray on Temozolomide-treated Glioma in Rats

BACKGROUND/AIM

Malignant glioma is a rapidly progressive primary brain cancer. The aim of the study was to investigate the effect of far-infrared ray (FIR) on temozolomide (TMZ)-treated glioma in rats.

MATERIALS AND METHODS

Male, 8-week old, Fischer 344 inbred rats with glioma were randomly divided into three study groups (20 rats in each group). The control group received saline only once daily for 5 days. The TMZ group received TMZ (30 mg/kg) once daily for 5 days. The TMZ plus FIR group received TMZ (30 mg/kg) once daily for 5 days and infrared-c irradiation of 40 min twice daily for 4 weeks. The relative tumor fold and the expression of hypoxia-induced factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were compared using one-way ANOVA at the end of study.

RESULTS

The relative tumor fold of the TMZ+FIR group was significantly higher compared to the control group, and was borderline higher compared to the TMZ group at Day 7. The relative tumor fold of TMZ+FIR group was significantly higher compared to the control group and the TMZ group at Days 14, 21 and 28. HIF-1α expression of TMZ+FIR group was borderline higher compared to the control group at Day 28. The VEGF expression of TMZ+FIR group was significantly higher compared to the control group and the TMZ group at Day 28.

CONCLUSION

FIR might increase the growth of glioma under TMZ treatment in rats possibly via increasing VEGF expression, but not HIF-1α expression.

Effects of Obstructive Sleep Apnea-Hypopnea Syndrome on Serum Carcinoembryonic Antigen Levels in Patients with Type 2 Diabetes Mellitus

Background

Type 2 diabetes mellitus (T2DM) is related to the serum carcinoembryonic antigen (CEA) level, which is used as a marker of colorectal cancer. Obstructive sleep apnea-hypopnea syndrome (OSAS) has been recently reported to have cancer-promoting effects. The aim of our study was to observe the effect of OSAS on serum levels of CEA in patients with T2DM.

Material/Methods

We enrolled 401 T2DM patients in this study. There were 244 patients with OSAS and 157 patients without OSAS.

Results

The CEA level in T2DM patients with OSAS was higher than that in those without OSAS (p<0.05). The participants with AHI scores ≥30 had higher CEA levels than those with 5≤ AHI scores <30 (p<0.05). The AHI score and ODI score were independently associated with increased risk of high CEA level in T2DM patients (odds ratio [OR]=1.052, 95% confidence interval [CI]: 1.011~1.095) and (OR=1.214, 95% CI: 1.070~1.377). Moreover, among male T2DM patients, the AHI score and ODI score had a linear correlation with the CEA level; this association was also observed in T2DM patients who smoked, had an HbA1c level ≥7%, or had a BMI ≥28 kg/m² (all p<0.05).

Conclusions

The AHI score and ODI score were positively associated with the CEA level in T2DM patients. The relationship was stronger in male T2DM patients and in those who smoked, were obese, or had poor glycemic control. The mechanism may be related to metabolic disorders, and the potential increased risk of colorectal cancer should be investigated in a prospective study.

Obstructive sleep apnea severity and subsequent risk for cancer incidence

In vitro and animal models suggest that obstructive sleep apnea (OSA) increases cancer risk. However, the impact of OSA severity on cancer risk is poorly understood.

We conducted a case-cohort study (a variant of the case-control study design), nested in a cohort of patients with a clinical diagnosis of OSA. OSA patients diagnosed between 2005 and 2013 were linked to a population-based cancer registry to identify cancers diagnosed subsequent to OSA between 2005 and 2015. Medical records were reviewed for a representative sample of 1162 OSA patients from this cohort (including 24 with subsequent cancer), and for an additional 304 OSA patients diagnosed with cancer; information regarding OSA severity indicators, including apnea-hypopnea index (AHI) was abstracted from these records. Adjusted Cox proportional hazards regression were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for associations of OSA severity indicators on cancer incidence.

Compared with individuals in the lowest AHI category (5–14.9), indicating mild OSA, the adjusted HR (95% CI) for cancer incidence associated with having moderate (15–29.9) or severe (30+) OSA were 0.72 (0.40–1.29) and 0.87 (0.52–1.45) respectively. Associations with other severity indicators were not significantly associated with cancer. However, the proportion of patients with severe OSA (AHI ≥30) was consistently higher across numerous cancer sites relative to the subcohort, suggesting increased cancer risk relative to patients with less severe OSA.

The absence of significant associations with OSA severity measures suggest that the underlying mechanisms deserve further investigation.

Intermittent hypoxia enhances the tumor programmed death ligand 1 expression in a mouse model of sleep apnea

Background

As a hallmark of obstructive sleep apnea (OSA), intermittent hypoxia (IH) promotes tumor progress. The high expression of programmed death 1 and programmed death ligand 1 (PD-L1) in tumor leads to immune evasion and subsequently aggravates tumor progress. This study aims to determine the tumor PD-L1 expression under the IH condition.

Methods

A total of 24 C57BL/6J mice were randomly assigned to the normoxia (control, CTL) group and the IH group. Mice in the IH group were subjected to the IH condition for 5 weeks. Lung cancer cells were injected into the flank of each mouse after 1 week of IH exposure. Tumor PD-L1 expression was detected by immunohistochemistry (IHC). Correlation between tumor weight, tumor volume, and expression of PD-L1 was analyzed.

Results

Compared to the CTL group, mice in the IH group had a high PD-L1 expression. The IH can enhance the tumor PD-L1 expression. Tumor weight, volume, and HIF-1α levels were closely associated with the PD-L1 expression in the IH group, while dissimilar findings were observed in the CTL group.

Conclusions

The IH enhances tumor PD-L1 expression in OSA mimicking mice. Additional studies are required to clarify the underlying mechanism.

Effect of cyclical intermittent hypoxia on Ad5CMVCre induced solitary lung cancer progression and spontaneous metastases in the KrasG12D+; p53fl/fl; myristolated p110fl/fl ROSA-gfp mouse

BACKGROUND

Epidemiological data suggests that obstructive sleep apnea (OSA) is associated with increased cancer incidence and mortality. We investigate the effects of cyclical intermittent hypoxia (CIH), akin to the underlying pathophysiology of OSA, on lung cancer progression and metastatic profile in a mouse model.

METHODS

Intrathoracic injection of Ad5CMVCre virus into a genetically engineered mouse (GEM) KrasG12D+/-; p53fl/fl; myristolated-p110αfl/fl-ROSA-gfp was utilized to induce a solitary lung cancer. Male mice were then exposed to either CIH or Sham for 40-41 days until harvest. To monitor malignant progression, serial micro CT scans with respiratory gating (no contrast) was performed. To detect spontaneous metastases in distant organs, H&E and immunohistochemistry were performed.

RESULTS

Eighty-eight percent of injected Ad5CMVCre virus was recovered from left lung tissue, indicating reliable and accurate injections. Serial micro CT demonstrated that CIH increases primary lung tumor volume progression compared to Sham on days 33 (p = 0.004) and 40 (p<0.001) post-injection. In addition, CIH increases variability in tumor volume on day 19 (p<0.0001), day 26 (p<0.0001), day 33 (p = 0.025) and day 40 (p = 0.004). Finally, metastases are frequently detected in heart, mediastinal lymph nodes, and right lung using H&E and immunohistochemistry.

CONCLUSIONS

Using a GEM mouse model of metastatic lung cancer, we report that male mice with solitary lung cancer have accelerated malignant progression and increased variability in tumor growth when exposed to cyclical intermittent hypoxia. Our results indicate that cyclical intermittent hypoxia is a pathogenic factor in non-small cell lung cancer that promotes the more rapid growth of developing tumors.

Obstructive sleep apnoea and comorbidity - an overview of the association and impact of continuous positive airway pressure therapy

INTRODUCTION

Obstructive sleep apnoea (OSA) is highly prevalent and there is considerable evidence supporting an independent association with a wide range of co-morbidities including cardiovascular, endocrine and metabolic, neuropsychiatric, pulmonary, and renal. Areas covered: A PubMed search of all the recent literature relating to OSA and co-morbidities was undertaken to critically evaluate the potential relationships and possible benefit of continuous positive airway pressure (CPAP) therapy. Expert commentary: The evidence supporting an independent association is stronger for some co-morbidities than others and in cardiovascular diseases is strongest for hypertension and atrial fibrillation. Potential mechanisms include intermittent hypoxia, fluctuating intrathoracic pressure, and recurring micro-arousals that trigger cell and molecular consequences including sympathetic excitation, systemic inflammation and oxidative stress, in addition to metabolic and endothelial dysfunction. Different mechanisms may predominate in individual co-morbidities. Recent long term randomised controlled trials have cast doubt on benefits to co-morbidities from CPAP therapy of OSA, especially where co-morbidities are already established. However, benefits may result in patients who are compliant with therapy and further research is required to clearly establish the role of OSA therapy in both primary and secondary prevention of co-morbidities.

Obstructive Sleep Apnea Activates HIF-1 in a Hypoxia Dose-Dependent Manner in HCT116 Colorectal Carcinoma Cells

Obstructive sleep apnea (OSA) affects a significant proportion of the population and is linked to increased rates of cancer development and a worse cancer outcome. OSA is characterized by nocturnal intermittent hypoxia and animal models of OSA-like intermittent hypoxia show increased tumor growth and metastasis. Advanced tumors typically have regions of chronic hypoxia, activating the transcription factor, HIF-1, which controls the expression of genes involved in cancer progression. Rapid intermittent hypoxia from OSA has been proposed to increase HIF-1 activity and this may occur in tumors. The effect of exposing a developing tumor to OSA-like intermittent hypoxia is largely unknown. We have built a cell-based model of physiological OSA tissue oxygenation in order to study the effects of intermittent hypoxia in HCT116 colorectal cancer cells. We found that HIF-1α increases following intermittent hypoxia and that the expression of HIF-target genes increases, including those involved in glycolysis, the hypoxic pathway and extracellular matrix remodeling. Expression of these genes acts as a 'hypoxic' signature which is associated with a worse prognosis. The total dose of hypoxia determined the magnitude of change in the hypoxic signature rather than the frequency or duration of hypoxia-reoxygenation cycles per se. Finally, transcription of HIF1A mRNA differs in response to chronic and intermittent hypoxia suggesting that HIF-1α may be regulated at the transcriptional level in intermittent hypoxia and not just by the post-translational oxygen-dependent degradation pathway seen in chronic hypoxia.

Intermittent hypoxia promotes carcinogenesis in azoxymethane and dextran sodium sulfate-induced colon cancer model

Intermittent hypoxia (IH), a characteristic of obstructive sleep apnea, is known to promote cancer progression and aggressiveness in mouse models. However, little is known regarding the effect of IH on cancer initiation. Here, the effect of IH on carcinogenesis was explored in azoxymethane (AOM) and dextran sodium sulfate (DSS)-induced colon cancer models with three different protocols. In the first protocol, two other application time points (early or late initiation of IH) were applied. In the second protocol, mice were divided into only two groups, and then exposed to either N or IH conditions for 14 days. In the third protocol, a pharmacological inhibition study for anti-inflammation (5-aminosalicylate) or anti-oxidative stress (N-acetylcysteine [NAC]) was performed. The number of tumors was significantly higher in the IH-1 than in the N or IH-2 groups. 8-oxo-2'-deoxyguanosine (8-OHdG) levels were higher in tumors of the IH-1 group than in that of the N and IH-2 groups. Gene expression related to reactive oxygen species production was higher in the IH-1 group than in the N and IH-2 groups, and it showed a positive correlation with 8-OHdG levels. Prior to cancer development 8-OHdG levels were already elevated in colonic epithelial regions in the IH group, possibly due to an imbalance between oxidative stress and antioxidant systems. NAC treatment resulted in a significant reduction in the number of tumors in mice exposed to IH. In conclusion, IH promotes carcinogenesis in a chemically-induced colon cancer model where elevated 8-OHdG may contribute to the increased tumor induction.

Anti-tumor effect of endostatin in a sleep-apnea mouse model with tumor

BACKGROUND

Obstructive sleep apnea (OSA) is associated with cancer incidence and mortality. The underlying mechanism is unclear. This study aims to evaluate the influence of intermittent hypoxia (IH), a novel hallmark of OSA, on tumor and to access the anti-tumor effect of endostatin on a mouse model with OSA.

METHODS

The C57BL/6 J mice were randomly classified into four groups: control (normoxia) (CTL), control plus endostatin (CTL + ED), IH, and IH plus endostatin (IH + ED). Mice in IH and IH + ED groups were subjected to IH 8 h per day in 5 weeks. Lewis lung cancer cells were injected into the flank of each mouse after 1 week of IH exposure. Endostatin was also intraperitoneally injected after tumor volume reached about 200 mm³. The maximum standard uptake values (SUVmax) were detected by micro-positron emission tomography-computed tomography (micro-PET-CT) imaging prior and post-endostatin administration. Microvessel density (MVD) and vascular endothelial growth factor (VEGF) were determined for evaluating the anti-tumor effect of endostatin among the normoxia and IH conditions.

RESULTS

Mice had higher SUVmax in the IH group than the CTL group (p < 0.01). When compared with mice in the CTL group, those in the IH group had significantly greater MVD values (p < 0.001). The SUVmax can be attenuated by endostatin both in the CTL (p < 0.01) and IH conditions (p < 0.001). When compared with CTL group, mice in the IH group had increased MVD values (p < 0.001) and VEGF expression both at mRNA (p < 0.05) and protein levels (p < 0.001 in western blotting results). Treatment with endostatin attenuated serum and tissue VEGF levels, lowering the MVD values. As compared to normoxia condition, the endostatin-therapeutic effects were more significant under the IH condition (p < 0.05 in western blotting results).

CONCLUSIONS

Micro-PET-CT imaging is a promising non-invasive technique to evaluate the tumor metabolic characteristics under IH condition in vivo. The anti-tumor effect of endostatin under IH condition is superior to that of the normoxia condition.

Models of intermittent hypoxia and obstructive sleep apnea: molecular pathways and their contribution to cancer

Obstructive sleep apnea (OSA) is common and linked to a variety of poor health outcomes. A key modulator of this disease is nocturnal intermittent hypoxia. There is striking epidemiological evidence that patients with OSA have higher rates of cancer and cancer mortality. Small-animal models demonstrate an important role for systemic intermittent hypoxia in tumor growth and metastasis, yet the underlying mechanisms are poorly understood. Emerging data indicate that intermittent hypoxia activates the hypoxic response and inflammatory pathways in a manner distinct from chronic hypoxia. However, there is significant heterogeneity in published methods for modeling hypoxic conditions, which are often lacking in physiological relevance. This is particularly important for studying key transcriptional mediators of the hypoxic and inflammatory responses such as hypoxia-inducible factor (HIF) and NF-κB. The relationship between HIF, the molecular clock, and circadian rhythm may also contribute to cancer risk in OSA. Building accurate in vitro models of intermittent hypoxia reflective of OSA is challenging but necessary to better elucidate underlying molecular pathways.

Obstructive Sleep Apnea Monocytes Exhibit High Levels of Vascular Endothelial Growth Factor Secretion, Augmenting Tumor Progression

Obstructive sleep apnea (OSA) is a syndrome characterized by repeated pauses in breathing induced by a partial or complete collapse of the upper airways during sleep. Intermittent hypoxia (IH), a hallmark characteristic of OSA, has been proposed to be a major determinant of cancer development, and patients with OSA are at a higher risk of tumors. Both OSA and healthy monocytes have been found to show enhanced HIF1α expression under IH. Moreover, these cells under IH polarize toward a tumor-promoting phenotype in a HIF1α-dependent manner and influence tumor growth via vascular endothelial growth factor (VEGF). Monocytes from patients with OSA increased the tumor-induced microenvironment and exhibited an impaired cytotoxicity in a 3D tumor in vitro model as a result of the increased HIF1α secretion. Adequate oxygen restoration both in vivo (under continuous positive airway pressure treatment, CPAP) and in vitro leads the monocytes to revert the tumor-promoting phenotype, demonstrating the plasticity of the innate immune system and the oxygen recovery relevance in this context.

Sleep-disordered breathing in patients with newly diagnosed lung cancer

Background

There are currently no data on the prevalence of sleep-disordered breathing (SDB) in patients with newly-diagnosed lung cancer. This might be of interest given that SDB is associated with increased cancer incidence and mortality. Furthermore, intermittent hypoxia has been linked with tumor growth and progression. The aim of the current study was to investigate the prevalence of SDB in patients with newly-diagnosed lung cancer.

Methods

Patients with newly-diagnosed lung cancer from three centers in Germany were screened for SDB using a two-channel screening system (ApneaLink™). SDB was defined as an apnea-hypopnea index of > 5/h, and was classified as mild if the AHI was 5–15/h whereas an AHI ≥15/h was classified as severe SDB. The presence of SDB-related symptoms was assessed using the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI).

Results

A total of 100 patients were included. The overall prevalence of SDB was 49%; 32 patients (32%) had mild SDB with a median AHI of 7.7/h (quartile [Q1 5.4/h, Q3 10.4/h]) and a median oxygen desaturation index of 8.5 [Q1 4.2/h; Q3 13.4/h] and seventeen patients (17%) had moderate to severe SDB with a median AHI of 25.2 [Q1 18/h, Q3 45.5/h] and a median oxygen desaturation index of 20.6/h [Q1 9.6/h, Q3 36.6/h]. Patients with moderate to severe SDB had mild daytime sleepiness (ESS score 8.24 ± 3.96 vs. 5.74 ± 3.53 in those without SDB vs. 6.22 ± 2.72 in those with mild SDB; p = 0.0343). The PSQI did not differ significantly between the three groups (p = 0.1137).

Conclusions

This study showed a high prevalence of SDB in patients with newly-diagnosed lung cancer. In these patients SDB was associated with intermittent hypoxia and increased daytime sleepiness. Additional research is needed to determine whether SDB influences prognosis and morbidity in patients with lung cancer.

Trial registration

NCT02270853 (ClinicalTrials.gov), date of registration: 14th October 2014.

Intermittent hypoxia promotes melanoma lung metastasis via oxidative stress and inflammation responses in a mouse model of obstructive sleep apnea

Background

Recently, increased tumor incidence and cancer-related mortality have been reported among patients with obstructive sleep apnea (OSA). Intermittent hypoxia (IH), the hallmark feature of OSA, contributes to the metastasis of tumors. However, the molecular mechanisms by which tumor metastasis is accelerated by OSA-like IH remain to be elucidated.

Methods

C57BL/6 J male mice were subjected to intravenous injection of B16F10 melanoma cells before receiving IH treatment. Then, the animals were randomly distributed into three groups (n = 8 each): normoxia (N) group, IH group, and antioxidant tempol group (IHT, exposed to IH after treatment with tempol). After the mice were sacrificed, the number and weight of lung metastatic colonies were assessed. The lung tissues with tumor metastasis were analyzed for markers of oxidative stress and inflammation and for HIF-1α using western blotting and real-time PCR (qRT-PCR). The level of reactive oxygen species (ROS) in B16F10 cell was also assessed after N, IH and IH with tempol treatments.

Results

Compared with normoxia, IH significantly increased the number and weight of mouse lung metastatic colonies. Treatment of B16F10 cells with IH significantly enhanced ROS generation. Lung tissues with tumor metastasis provided evidence of increased oxidative stress, as assessed by p22^phox and SOD mRNA levels and the NRF2 protein level, as well as increased inflammation, as assessed by TNF-α and IL-6 mRNA levels and the NF-κB P65 protein level. HIF-1α protein levels were increased in response to IH treatment. Tempol, an important antioxidant, ameliorated IH-induced melanoma lung metastasis in mice and reduced oxidative stress and inflammation responses.

Conclusions

These results support the hypothesis that oxidative stress and inflammation responses play an important role in the pathogenesis of OSA-like IH-induced melanoma lung metastasis in mice. Antioxidant intervention provides a novel strategy for the prevention and treatment of cancer in OSA populations.

Alzheimer's Disease Mutant Mice Exhibit Reduced Brain Tissue Stiffness Compared to Wild-type Mice in both Normoxia and following Intermittent Hypoxia Mimicking Sleep Apnea

Background

Evidence from patients and animal models suggests that obstructive sleep apnea (OSA) may increase the risk of Alzheimer's disease (AD) and that AD is associated with reduced brain tissue stiffness.

Aim

To investigate whether intermittent hypoxia (IH) alters brain cortex tissue stiffness in AD mutant mice exposed to IH mimicking OSA.

Methods

Six-eight month old (B6C3-Tg(APPswe,PSEN1dE9)85Dbo/J) AD mutant mice and wild-type (WT) littermates were subjected to IH (21% O₂ 40 s to 5% O₂ 20 s; 6 h/day) or normoxia for 8 weeks. After euthanasia, the stiffness (E) of 200-μm brain cortex slices was measured by atomic force microscopy.

Results

Two-way ANOVA indicated significant cortical softening and weight increase in AD mice compared to WT littermates, but no significant effects of IH on cortical stiffness and weight were detected. In addition, reduced myelin was apparent in AD (vs. WT), but no significant differences emerged in the cortex extracellular matrix components laminin and glycosaminoglycans when comparing baseline AD and WT mice.

Conclusion

AD mutant mice exhibit reduced brain tissue stiffness following both normoxia and IH mimicking sleep apnea, and such differences are commensurate with increased edema and demyelination in AD.

Altered CD8+ T-Cell Lymphocyte Function and TC1 Cell Stemness Contribute to Enhanced Malignant Tumor Properties in Murine Models of Sleep Apnea

Study Objective

The presence of obstructive sleep apnea (OSA) in patients with cancer appears to be accompanied by poorer outcomes. However, the mechanisms underlying such association are unknown. Tumor infiltrating lymphocytes (TILs), including CD8+ T cells, function as cytotoxic T lymphocytes (CTLs) and mount immune responses to cancer by the release of cytolytic enzymes, including granzyme B (GzmB), perforin (Prf), and cytokines such as interferon (IFN)-γ.

Methods

Using established in vivo mouse models, we investigated CD8+ T cells and cancer stem cells (CSCs) in intermittent hypoxia (IH) and sleep fragmentation (SF) in the context of tumor environment.

Results

Both IH and SF promoted increased tumor growth and invasion toward adjacent tissues compared to controls. The number and frequency of GzmB-producing CD8+ T cells per milligram of tumor tissue was significantly reduced in IH-exposed mice with impaired cytolytic function in both the groups and correlated with tumor weight. We also found that Oct4+ and CD44+CD133+ expressing CSCs were considerably increased in IH and SF tumors, respectively.

Conclusions

Reductions in GzmB in intratumoral CD8+ T cells in combination with the changes in tumor microenvironment that maintain the ability of CSCs to self-renew and even confer this capability to the nonstem population are compatible with reduced immunosurveillance and adverse tumor outcomes in animal models of OSA.

Intermittent hypoxia and cancer: Undesirable bed partners?

The deleterious effects of intermittent hypoxia (IH) on cancer biology have been primarily evaluated in the context of the aberrant circulation observed in solid tumors which results in recurrent intra-tumoral episodic hypoxia. From those studies, IH has been linked to an accelerated tumor progression, metastasis and resistance to therapies. More recently, the role of IH in cancer has also been studied in the context of obstructive sleep apnea (OSA), since IH is a hallmark characteristic of this condition. Such recent studies are undoubtedly adding more information regarding the role of IH on tumor malignancy. In terms of the IH patterns associated with OSA, this altered oxygenation paradigm has been recently proposed as a determinant factor in fostering cancer incidence and progression from both in vitro and in vivo experimental models. Here, we summarize all the available evidence to date linking IH effects on several types of cancer.

Síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) y su relación con el cáncer

Desde hace algunos años se ha sugerido que los pacientes con síndrome de apnea-hipopnea obstructiva del sueño sin tratamiento tienen una mayor probabilidad de cáncer sólido y de mortalidad por cáncer, sin embargo hay dudas frente al tema. Por esta razón, en este artículo se describen, por un lado, los estudios más importantes al respecto y, por el otro, la fisiopatología propuesta por los investigadores que plantean esta asociación donde la hipoxia, el daño oxidativo del DNA, la disfunción endotelial y la disrupción de la arquitectura del sueño juegan un papel fundamental, además de otras consideraciones interesante.

Accelerated tumor growth under intermittent hypoxia is associated with hypoxia-inducible factor-1-dependent adaptive responses to hypoxia

Mounting evidence has revealed a causative role of intermittent hypoxia (IH) in cancer progression in mouse models of obstructive sleep apnea (OSA), but most studies have focused on the effects of IH following tumor implantation using an exposure to single IH frequency. Thus, we aimed to investigate 1) the potential effect of IH on the initial tumor growth in patients with OSA without an interaction with other mechanisms induced by IH in mice and 2) the influence of the IH frequency on tumor growth, which were tested using pre-conditioning with IH (Pre-IH) and 2 different IH frequencies, respectively. Pre-IH was achieved by alternatively maintaining melanoma cells between normoxia (10 min, 21% O₂) and hypoxia (50 min, 1% O₂) for 7 days (12 cycles per day) before administering them to mice. The conditions for IH-1 and IH-2 were 90 s of 12% FiO₂ followed by 270s of 21% FiO₂ (10 cycles/h), and 90 s of 12% FiO₂ and 90 s of 21% FiO₂ (20 cycles/h), respectively, for 8 h per day. Tumor growth was significantly higher in the Pre-IH group than in the normoxia group. In addition, the IH-2 group showed more accelerated tumor growth compared to the normoxia and IH-1 groups. Immunohistochemistry and gene-expression results consistently showed the up-regulation of molecules associated with HIF-1α-dependent hypoxic adaptation in tumors of the Pre-IH and IH-2 groups. Our findings reveal that IH increased tumor progression in a frequency-dependent manner, regardless of whether it was introduced before or after in vivo tumor cell implantation.

Frequency and magnitude of intermittent hypoxia modulate endothelial wound healing in a cell culture model of sleep apnea

Intermittent hypoxia (IH) has been implicated in the cardiovascular consequences of obstructive sleep apnea (OSA). However, the lack of suitable experimental systems has precluded assessment as to whether IH is detrimental, protective, or both for the endothelium. The aim of the work was to determine the effects of frequency and amplitude of IH oxygenation swings on aortic endothelial wound healing. Monolayers of human primary endothelial cells were wounded and subjected to constant oxygenation (1%, 4%, 13%, or 20% O₂) or IH at different frequencies (0.6, 6, or 60 cycles/h) and magnitude ranges (13-4% O₂ or 20-1% O₂), using a novel well-controlled system, with wound healing being measured after 24 h. Cell monolayer repair was similar at 20% O₂ and 13% O₂, but was considerably increased (approximately twofold) in constant hypoxia at 4% O₂ The magnitude and frequency of IH considerably modulated wound healing. Cycles ranging 13-4% O₂ at the lowest frequency (0.6 cycles/h) accelerated endothelial wound healing by 102%. However, for IH exposures consisting of 20% to 1% O₂ oscillations, wound closure was reduced compared with oscillation in the 13-4% range (by 74% and 44% at 6 cycles/h and 0.6 cycles/h, respectively). High-frequency IH patterns simulating severe OSA (60 cycles/h) did not significantly modify endothelial wound closure, regardless of the oxygenation cycle amplitude. In conclusion, the frequency and magnitude of hypoxia cycling in IH markedly alter wound healing responses and emerge as key factors determining how cells will respond in OSA.NEW & NOTEWORTHY Intermittent hypoxia (IH) induces cardiovascular consequences in obstructive sleep apnea (OSA) patients. However, the vast array of frequencies and severities of IH previously employed in OSA-related experimental studies has led to controversial results on the effects of IH. By employing an optimized IH experimental system here, we provide evidence that the frequency and magnitude of IH markedly alter human aortic endothelial wound healing, emerging as key factors determining how cells respond in OSA.

Monocytes inhibit NK activityviaTGF-β in patients with obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is associated with cancer incidence and mortality. The contribution of the immune system appears to be crucial; however, the potential role of monocytes and natural killer (NK) cells remains unclear.

Quantitative reverse transcriptase PCR, flow cytometry andin vitroassays were used to analyse the phenotype and immune response activity in 92 patients with OSA (60 recently diagnosed untreated patients and 32 patients after 6 months of treatment with continuous positive airway pressure (CPAP)) and 29 healthy volunteers (HV).

We determined that monocytes in patients with OSA exhibit an immunosuppressive phenotype, including surface expression of glycoprotein-A repetitions predominant protein (GARP) and transforming growth factor-β (TGF-β), in contrast to those from the HV and CPAP groups. High levels of TGF-β were detected in OSA sera. TGF-β release by GARP+monocytes impaired NK cytotoxicity and maturation. This altered phenotype correlated with the hypoxic severity clinical score (CT90). Reoxygenation eventually restored the altered phenotypes and cytotoxicity.

This study demonstrates that GARP+monocytes from untreated patients with OSA have an NK-suppressing role through their release of TGF-β. Our findings show that monocyte plasticity immunomodulates NK activity in this pathology, suggesting a potential role in cancer incidence.