Updates on "adiponcosis": More new incoming evidence strengthening the obesity-cancer link

Appraising the Effect of Potential Risk Factors on Thyroid Cancer: A Mendelian Randomization Study

CONTEXT

Various risk factors have been associated with the risk of thyroid cancer in observational studies. However, the causality of the risk factors is not clear given the susceptibility of confounding and reverse causation.

OBJECTIVE

A 2-sample Mendelian randomization approach was used to estimate the effect of potential risk factors on thyroid cancer risk.

METHODS

Genetic instruments to proxy 55 risk factors were identified by genome-wide association studies (GWAS). Associations of these genetic variants with thyroid cancer risk were estimated in GWAS of the FinnGen Study (989 cases and 217 803 controls). A Bonferroni-corrected threshold of P = 9.09 × 10-4 was considered significant, and P < 0.05 was considered to be suggestive of an association.

RESULTS

Telomere length was significantly associated with increased thyroid cancer risk after correction for multiple testing (OR 4.68; 95% CI, 2.35-9.31; P = 1.12 × 10-5). Suggestive associations with increased risk were noted for waist-to-hip ratio (OR 1.85; 95% CI, 1.02-3.35; P = 0.042) and diastolic blood pressure (OR 1.60; 95% CI, 1.08-2.38; P = 0.019). Suggestive associations were noted between hemoglobin A1c (HbA1c) (OR 0.20; 95% CI, 0.05-0.82; P = 0.025) and decreased risk of thyroid cancer. Risk of thyroid cancer was not associated with sex hormones and reproduction, developmental and growth, lipids, diet and lifestyle, or inflammatory factors (All P > 0.05).

CONCLUSION

Our study identified several potential targets for primary prevention of thyroid cancer, including central obesity, diastolic blood pressure, HbA1c, and telomere length, which should inform public health policy.

The Potential Role of Nutrition in Lung Cancer Establishment and Progression

Lung cancer is a devastating disease with a high incidence and low survival rates, so recent studies have focused on analyzing the risk factors that might prevent this disease from developing or have protective/therapeutic effects. Nutrition is an important key factor in the prevention and treatment of lung cancer. Various factors appear to be involved in the development of the latter, such as cigarette smoking or certain external environmental factors. The increase in oxidative stress is therefore an integral part of the carcinogenesis process. The biological role of bioactive factors derived from adipose tissue, mainly adipokines, is implicated in various cancers, and an increasing body of evidence has shown that certain adipocytokines contribute to the development, progression and prognosis of lung cancer. Not all adipokines stimulate tumor growth; in fact, adiponectin inhibits carcinogenesis by regulating both cell growth and the levels of inflammatory cytokines. Adiponectin expression is deregulated in several cancer types. Many nutritional factors have been shown to increase adiponectin levels and therefore could be used as a new therapeutic strategy for combating lung cancer. In addition, foods with antioxidant and anti-inflammatory properties play a key role in the prevention of many human diseases, including lung cancer. The purpose of this review is to analyze the role of diet in lung cancer in order to recommend dietary habit and lifestyle changes to prevent or treat this pathology.

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.

Obesity and Waist Circumference are Possible Risk Factors for Thyroid Cancer: Correlation with Different Ultrasonography Criteria

Background

Obesity has an important role in the pathogenesis of cancer; however, there are no clear mechanisms explaining the association between obesity and risk of thyroid cancer (TC).

Methods

It is a cross-sectional study including 184 patients with benign thyroid nodules (BN) and 19 patients with TC. Body mass index (BMI), waist circumference (WC), hip circumference (HC), waist/hip (W/H) ratio were assessed and correlated to relevant clinico-pathological features of the patients, different ultra-sonographic (U/S) criteria and risk of malignancy.

Results

There was a significant increase in BMI, WC and W/H ratio in TC patients compared to BN group (P=0.001, 0.011 and 0.003). Increased BMI, WC and HC were associated significantly with solid nodules (P<0.05). WC increased in hypoechoic (103.1±15.4cm) and heterogeneous (103.8±16.7cm) nodules, compared to isoechoic (97.3±15.5cm) and hyperechoic (96.1±10cm) nodules (P=0.046). It also increased with lymph nodes enlargement (P=0.04). There was a significant association between WC and TIRADS classification (P=0.032), as it increased with TR4b (118.5 ± 12.9 cm) and TR5 (117.3 ± 13.9 cm) compared to TR2 (114.1 ± 15.7 cm, P=0.025 and 0.008, respectively). WC is an independent predictor for TC [OR: 1.092, CI: 1.020-1.170, P=0.012]. It achieved sensitivity, specificity and AUC (71.4%, 68.7% and 0.750; respectively), at a cutoff value of 108.5 cm (P=0.003), and when combined with BMI at a cutoff value of 32.59 (77.8% and 68.4%, respectively, AUC: 0.780, P<0.001).

Conclusion

Central adiposity is strongly associated with the risk of TC. WC is more superior to BMI when correlated with TIRADS classification and also is an independent predictor for TC.

Growth hormone-releasing hormone (GHRH) deficiency promotes inflammation-associated carcinogenesis

The somatotropic axis, in addition to its well-known metabolic and endocrine effects, plays a pivotal role in modulation of inflammation. Moreover, growth hormone (GH)-releasing hormone (GHRH) has been involved in the development of various human tumors. In this work we aimed to investigate the consequences of GHRH deficiency on the development of inflammation-associated colon carcinogenesis in a mouse model of isolated GH deficiency due to generalized ablation of the GHRH gene [GHRH knock out (GHRHKO)]. Homozygous GHRHKO (-/-) male mice and wild type (C57/BL6, +/+) male mice as control group, were used. After azoxymetane (AOM)/dextran sodium sulfate (DSS) treatment -/- mice displayed higher Disease Activity Index (DAI) score, and more marked weight loss compared to +/+ animals. Additionally, -/- mice showed a significant increase in total tumors, in particular of large size predominantly localized in distal colon. In colonic tissue of AOM/DSS-treated -/- mice we found the presence of invasive adenocarcinomas, dysplasia and colitis with mucosal ulceration. Conversely, AOM/DSS-treated +/+ mice showed only presence of adenomas, without invasion of sub-mucosa. Treatment with AOM/DSS significantly increased prostaglandin (PG)E₂ and 8-iso-PGF_2α levels along with cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-α, nuclear factor kappa B (NF-kB) and inducible nitric oxide synthase (iNOS) gene expression, in colon specimens. The degree of increase of all these parameters was more markedly in -/- than +/+ mice. In conclusion, generalized GHRH ablation increases colon carcinogenesis responsiveness in male mice. Whether this results from lack of GH or GHRH remains to be established.

Adiponectin as Link Factor between Adipose Tissue and Cancer

Adipose tissue is a key regulator of energy balance playing an active role in lipid storage as well as in synthesizing several hormones directly involved in the pathogenesis of obesity. Obesity represents a peculiar risk factor for a growing list of cancers and is frequently associated to poor clinical outcome. The mechanism linking obesity and cancer is not completely understood, but, amongst the major players, there are both chronic low-grade inflammation and deregulation of adipokines secretion. In obesity, the adipose tissue is pervaded by an abnormal number of immune cells that create an inflammatory environment supporting tumor cell proliferation and invasion. Adiponectin (APN), the most abundant adipokine, shows anti-inflammatory, anti-proliferative and pro-apoptotic properties. Circulating levels of APN are drastically decreased in obesity, suggesting that APN may represent the link factor between obesity and cancer risk. The present review describes the recent advances on the involvement of APN and its receptors in the etiology of different types of cancer.