Mechanisms linking physical activity with cancer

New Insights into the Role of Exercise in Inhibiting mTOR Signaling in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) does not express estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 and is characterized by its aggressive nature, lack of targets for targeted therapies, and early peak of recurrence. Due to these specific characteristics, chemotherapy does not usually yield substantial improvements and new target therapies and alternative strategies are needed. The beneficial responses of TNBC survivors to regular exercise, including a reduction in the rate of tumor growth, are becoming increasingly apparent. Physiological adaptations to exercise occur in skeletal muscle but have an impact on the entire body through systemic control of energy homeostasis and metabolism, which in turn influence the TNBC tumor microenvironment. Gaining insights into the causal mechanisms of the therapeutic cancer control properties of regular exercise is important to improve the prescription and implementation of exercise and training in TNBC survivors. Here, we provide new evidence of the effects of exercise on TNBC prevention, control, and outcomes, based on the inhibition of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB also known as Akt)/mammalian target of rapamycin (mTOR) (PI3K-Akt-mTOR) signaling. These findings have wide-ranging clinical implications for cancer treatment, including recurrence and case management.

Dietary inflammatory index and incidence of breast cancer in the SUN project

BACKGROUND & AIMS

Breast cancer (BC) is the most commonly diagnosed cancer, and diet is suspected to play a role in its development. Dietary factors may mediate this process through modulation of inflammation, though findings from previous studies have not been consistent. We aimed to longitudinally assess the association between the dietary inflammatory index (DII^®), a frequently used method to assess the inflammatory potential of the diet, and incident BC.

METHODS

We included 10,713 middle-aged, Spanish female university graduates from the SUN cohort. DII^® scores were derived from a validated 136-item food-frequency questionnaire, and it was based on scientific evidence on the relationship between diet and inflammatory biomarkers. Diagnosis of BC was reported by the participant or, if deceased, by the next of kin or identified from death certificates. Self-reports of BC were confirmed by revision of medical reports by an experienced oncologist. Cox proportional hazard models were used to estimate multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) for the association between quartiles of DII^® and incident BC.

RESULTS

After 10.3 years of median follow-up, we identified 100 confirmed and 168 probable incident BC cases. The multivariable-adjusted HR for participants in the 4th quartile to the 1st quartile was 1.44 (95% CI 0.76-2.72; p-trend: 0.339) when confirmed cases were analyzed, and 1.20 (95% CI 0.72-1.99; p-trend: 0.757) for the probable cases. We neither observed statistically significant differences in regard to menopausal status.

CONCLUSIONS

The apparent increase in risk between DII^® scores and BC in our cohort was not statistically significant, which could be partly explained by the small number of observed cases.

Association of physical activity and sedentary time with blood cell counts: National Health and Nutrition Survey 2003-2006

Objective

To assess the association of objectively measured levels of physical activity and sedentary time with major blood cell counts (e.g. white blood cells, red blood cells, platelets) among adults.

Methods

Data collected from the 2003–2004 and 2005–2006 cycles of the National Health and Nutrition Examination Survey (NHANES) was used to assess blood cell counts in relation to objectively measured physical activity and sedentary time (accelerometer). A series of linear regressions modes were used to assess these associations adjusting for a range of factors known to be associated with blood cell counts, including age, body mass index, dietary factors, and previous infections.

Results

Higher levels of moderate-vigorous physical activity (p_trend<0.001) and lower sedentary time (p_trend = 0.040) were associated with lower white blood cell counts.

Conclusion

These results suggest that modifiable health behaviors, such as physical activity and sedentary time, may be associated with inflammatory status through white blood cell counts, which may be important for future disease risk.

Domain-specific physical activity and sedentary behaviour in relation to colon and rectal cancer risk: a systematic review and meta-analysis

Background

Physical activity is associated with reduced risk of colorectal cancer, but most epidemiological studies have focused on occupational and recreational physical activity. The evidence for other domains of activity, and for sedentary behaviour, is limited.

Methods

Medline, Embase and Web of Science were searched from inception to December 2015 for studies examining domain-specific physical activity or sedentary behaviour and the risk of colon and/or rectal cancer. We extracted maximally adjusted relative risks (RRs) except when RRs not adjusted for body mass index, were also presented. We used random-effects meta-analysis to compute pooled RRs comparing the highest versus the lowest level of exposure. We used meta-regression to assess sources of heterogeneity in estimates.

Results

We identified 17 cohort and 21 case-control studies, of which 17 had occupational data, 23 had recreational data, three each had data on transport and household physical activity domains, and 6 studies had data on occupational sedentary behaviour. The pooled relative risks (RRs) for colon cancer were 0.74 (95% confidence interval (CI): 0.67, 0.82) for occupational activity, 0.80 (95% CI: 0.71, 0.89) for recreational activity, 0.66 (95% CI: 0.45, 0.98) for transport-related physical activity, 0.85 (95% CI: 0.71, 1.02) for household physical activity, and 1.44 (95% CI: 1.28, 1.62) for occupational sedentary behaviour. For rectal cancer, the pooled RRs were 0.88 (95% CI: 0.79, 0.98) for occupational activity, 0.87 (95% CI: 0.75, 1.01) for recreational activity, 0.88 (95% CI: 0.70, 1.12) for transport-related physical activity, 1.01 (95% CI: 0.80, 1.27) for household physical activity, and 1.02 (95% CI: 0.82, 1.28) for occupational sedentary behaviour.

Conclusions

In addition to increasing occupational and recreational physical activity, promoting physical activity during transport and reducing sedentary behaviour in the workplace may also be useful colorectal cancer prevention strategies.

Effect of exercise and/or reduced calorie dietary interventions on breast cancer-related endogenous sex hormones in healthy postmenopausal women

Background

Physical inactivity and being overweight are modifiable lifestyle risk factors that consistently have been associated with a higher risk of postmenopausal breast cancer in observational studies. One biologic hypothesis underlying this relationship may be via endogenous sex hormone levels. It is unclear if changes in dietary intake, physical activity, or both, are most effective in changing these hormone levels.

Objective

This systematic review and meta-analysis examines the effect of reduced caloric dietary intake and/or increased exercise levels on breast cancer-related endogenous sex hormones.

Methods

We conducted a systematic literature search in MEDLINE, Embase, and Cochrane’s Central Register of Controlled Trials (CENTRAL) up to March 2017. Main outcome measures were breast cancer-related endogenous sex hormones.

Randomized controlled trials (RCTs) reporting effects of reduced caloric intake and/or exercise interventions on endogenous sex hormones in healthy, physically inactive postmenopausal women were included. Studies including women using hormone therapy were excluded. The methodological quality of each study was assessed by the Cochrane’s risk of bias tool.

Results

From the 2599 articles retrieved, seven articles from six RCTs were included in this meta-analysis. These trials investigated 1588 healthy postmenopausal women with a mean age ranging from 58 to 61 years. A combined intervention of reduced caloric intake and exercise, with durations ranging from 16 to 52 weeks, compared with a control group (without an intervention to achieve weight loss) resulted in the largest beneficial effects on estrone treatment effect ratio (TER) = 0.90 (95% confidence interval (CI) = 0.83–0.97), total estradiol TER = 0.82 (0.75–0.90), free estradiol TER = 0.73 (0.66–0.81), free testosterone TER = 0.86 (0.79–0.93), and sex hormone biding globulin (SHBG) TER = 1.23 (1.15–1.31). A reduced caloric intake without an exercise intervention resulted in significant effects compared with control on total estradiol TER = 0.86 (0.77–0.95), free estradiol TER = 0.77 (0.69–0.84), free testosterone TER = 0.91 (0.84–0.98), and SHBG TER = 1.20 (1.06–1.36). Exercise without dietary change, versus control, resulted in borderline significant effects on androstenedione TER = 0.97 (0.94–1.00), total estradiol TER = 0. 97 (0.94–1.00), and free testosterone TER = 0. 0.97 (0.95–1.00).

Conclusions and relevance

This meta-analysis of six RCTs demonstrated that there are beneficial effects of exercise, reduced caloric dietary intake or, preferably, a combination of exercise and diet on breast cancer-related endogenous sex hormones in physically inactive postmenopausal women.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1009-8) contains supplementary material, which is available to authorized users.

Lifestyle Interventions for Breast Cancer Prevention

One-in-eight women in the United States will develop breast cancer in her lifetime. Despite the established efficacy of selective estrogen receptor modulators and aromatase inhibitors in reducing the risk of developing hormone receptor positive breast cancer, use of these therapies in clinical practice is often limited by concerns over toxicities that may negatively influence quality of life. There is emerging interest in the oncology community to understand how modifiable risk factors related to energy balance-such as obesity, physical inactivity, and poor dietary patterns-may relate to breast cancer risk. Over the past three decades, observational studies have reported that obesity, physical inactivity, sedentary behavior, and dietary patterns are associated with increased breast cancer risk. However, uncertainty exists about whether the observed associations are attributable to confounding from other factors. Randomized controlled trials are necessary to provide unbiased efficacy estimates of lifestyle changes on breast cancer risk. However, such trials would typically require a large sample size, long-term follow up, and substantial financial investment. One approach to manage these barriers is to leverage recent advances in precision prevention to select high-risk study participants to reduce sample size or shorten length of follow up. This approach may accelerate the translation of epidemiologic discoveries into proven population-based breast cancer prevention interventions.

Physical activity and sedentary behavior in relation to mortality among renal cell cancer survivors

Background

The relations of physical activity and sedentary behavior to mortality risk among patients with renal cell cancer have not yet been evaluated.

Methods

We conducted a prospective cohort study among 667 renal cell cancer survivors aged 50–71 years of the National Institutes of Health (NIH)-AARP Diet and Health Study with a median follow-up time of 7.1 years. Post-diagnosis physical activity, TV viewing, and total sitting time were assessed using self-administered questionnaires. Hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality were estimated using Cox proportional hazards models.

Results

Increasing levels of moderate to vigorous physical activity were related to decreased risk of overall mortality [multivariable-adjusted HRs for <1 hr/wk (reference), 1 to 3 hrs/wk, ≥3 to <7 hrs/wk, and ≥7 hrs/wk = 1.0, 1.16, 0.94, and 0.60 (95% CI = 0.38–0.96; p-trend = 0.03)]. In contrast, television viewing was associated with increased risk of overall mortality in the age- and sex-adjusted model (HR for >4 hrs/d vs. 0 to 2 hrs/d = 1.52, 95% CI = 1.02–2.26; p-trend = 0.04), but the relation was attenuated following further control for other covariates (multivariable-adjusted HR = 1.44, 95% CI = 0.92–2.24; p-trend = 0.11). Total sitting time was unrelated to all-cause mortality.

Conclusion

Among renal cancer patients, moderate to vigorous physical activity is associated with decreased risk of overall mortality. Clinicians should consider discussing the potential benefits of physical activity for longevity among survivors of renal cell cancer.

Outdoor air pollution, green space, and cancer incidence in Saxony: a semi-individual cohort study

BACKGROUND

There are a few epidemiological studies that (1) link increased ambient air pollution (AP) with an increase in lung cancer incidence rates and (2) investigate whether residing in green spaces could be protective against cancer. However, it is completely unclear whether other forms of cancer are also affected by AP and if residential green spaces could lower cancer incidence rates in general. Therefore, the objective was to estimate whether AP and green space are associated with several cancer types.

METHODS

The analysis was based on routine health care data from around 1.9 million people from Saxony who were free of cancer in 2008 and 2009. Incident cancer cases (2010-2014) of mouth and throat, skin (non-melanoma skin cancer - NMSC), prostate, breast, and colorectum were defined as: (1) one inpatient diagnosis, or (2) two outpatient diagnoses in two different quarters within one year and a specific treatment or death within two quarters after the diagnosis. Exposures, derived from freely available 3rd party data, included particulate matter with aerodynamic diameter of less than 10 μm (PM10) and nitrogen dioxide (N02) as well as green space (Normalized Difference Vegetation Index - NDVI). Associations between air pollutants, green space, and cancer incidence were assessed by multilevel Poisson models. Age, sex, physician contacts, short- and long-term unemployment, population density, and having an alcohol-related disorder were considered as potential confounders.

RESULTS

Three thousand one hundred seven people developed mouth and throat cancer, 33,178 NMSC, 9611 prostate cancer, 9577 breast cancer, and 11,975 colorectal cancer during the follow-up period (2010-2014). An increase in PM10 of 10 μg/m3 was associated with a 53% increase in relative risk (RR) of mouth and throat cancer and a 52% increase in RR of NMSC. Prostate and breast cancer were modestly associated with PM10 with an increase in RR of 23 and 19%, respectively. The associations with N02 were in the same direction as PM10 but the effect estimates were much lower (7-24%). A 10% increase in NDVI was most protective of mouth and throat cancer (- 11% RR) and of NMSC (- 16% RR). Colorectal cancer was not affected by any of the exposures.

CONCLUSIONS

In addition to the studies carried out so far, this study was able to provide evidence that higher ambient AP levels increase the risk of mouth and throat cancer as well as of NMSC and that a higher residential green space level might have a protective effect for NMSC in areas with low to moderate UV intensity. Nevertheless, we cannot rule out residual confounding by socioeconomic or smoking status.

Outdoor air pollution, green space, and cancer incidence in Saxony: a semi-individual cohort study

BACKGROUND

There are a few epidemiological studies that (1) link increased ambient air pollution (AP) with an increase in lung cancer incidence rates and (2) investigate whether residing in green spaces could be protective against cancer. However, it is completely unclear whether other forms of cancer are also affected by AP and if residential green spaces could lower cancer incidence rates in general. Therefore, the objective was to estimate whether AP and green space are associated with several cancer types.

METHODS

The analysis was based on routine health care data from around 1.9 million people from Saxony who were free of cancer in 2008 and 2009. Incident cancer cases (2010-2014) of mouth and throat, skin (non-melanoma skin cancer - NMSC), prostate, breast, and colorectum were defined as: (1) one inpatient diagnosis, or (2) two outpatient diagnoses in two different quarters within one year and a specific treatment or death within two quarters after the diagnosis. Exposures, derived from freely available 3rd party data, included particulate matter with aerodynamic diameter of less than 10 μm (PM₁₀) and nitrogen dioxide (N0₂) as well as green space (Normalized Difference Vegetation Index - NDVI). Associations between air pollutants, green space, and cancer incidence were assessed by multilevel Poisson models. Age, sex, physician contacts, short- and long-term unemployment, population density, and having an alcohol-related disorder were considered as potential confounders.

RESULTS

Three thousand one hundred seven people developed mouth and throat cancer, 33,178 NMSC, 9611 prostate cancer, 9577 breast cancer, and 11,975 colorectal cancer during the follow-up period (2010-2014). An increase in PM₁₀ of 10 μg/m³ was associated with a 53% increase in relative risk (RR) of mouth and throat cancer and a 52% increase in RR of NMSC. Prostate and breast cancer were modestly associated with PM₁₀ with an increase in RR of 23 and 19%, respectively. The associations with N0₂ were in the same direction as PM₁₀ but the effect estimates were much lower (7-24%). A 10% increase in NDVI was most protective of mouth and throat cancer (- 11% RR) and of NMSC (- 16% RR). Colorectal cancer was not affected by any of the exposures.

CONCLUSIONS

In addition to the studies carried out so far, this study was able to provide evidence that higher ambient AP levels increase the risk of mouth and throat cancer as well as of NMSC and that a higher residential green space level might have a protective effect for NMSC in areas with low to moderate UV intensity. Nevertheless, we cannot rule out residual confounding by socioeconomic or smoking status.

Self-rated walking pace and all-cause, cardiovascular disease and cancer mortality: individual participant pooled analysis of 50 225 walkers from 11 population British cohorts

BACKGROUND/OBJECTIVES

Walking pace is associated with risk of premature mortality. However, whether this relationship is independent of total volume of physical activity and highest physical activity intensity remains unclear. We examined the associations between walking pace and cause-specific mortality, investigating the potential modifying effect of factors such as total physical activity volume, highest physical activity intensity, age, sex and body mass index (BMI).

METHODS

Prospective pooled analysis of 11 population-based baseline surveys in England and Scotland between 1994 and2008 that were linked with mortality records. Multivariate-adjusted Cox proportional hazards models examined associations between walking pace (slow, average, brisk/fast) and all-cause, cancer and cardiovascular disease (CVD) mortality.

RESULTS

50 225 walkers were entered in the core analyses. Among participants who did not experience an event in the first 2 years of follow-up (n=49 731), walking at an average or brisk/fast pace was associated with a reduced risk of all-cause (20% (95% CI 12% to 28%) and 24% (95% CI 13% to 33%), respectively) and CVD mortality (24% (95% CI 9% to 36%) and 21% (95% CI 1% to 38%), respectively), compared with reporting walking at a slow pace. In stratified analyses, such associations were evident among those over 50 years, those not meeting the physical activity recommendations and those who did not undertake vigorous-intensity activity. There were no interactions by sex or BMI. No associations were seen between pace and cancer mortality.

CONCLUSION

Walking benefits health. Assuming causality, these analyses suggest that increasing walking pace could reduce risk for all-cause and CVD mortality. Walking pace could be emphasised in public health messages, especially in situations when increase in walking volume or frequency is less feasible.

Grain Intake and Clinical Outcome in Stage III Colon Cancer: Results From CALGB 89803 (Alliance)

Background

Energy balance–related risk factors for colon cancer recurrence and mortality—type II diabetes, hyperinsulinemia, inflammation, and visceral obesity—are positively correlated with consumption of refined grains and negatively correlated with consumption of whole grains. We examined the relationship between the consumption of refined and whole grains with cancer recurrence and mortality in a cohort of patients with colon cancer.

Methods

We conducted a prospective observational study of 1024 patients with stage III colon cancer who participated in a randomized trial of postoperative chemotherapy. Patients reported consumption of refined and whole grains using a food frequency questionnaire during and six months after chemotherapy. The primary outcome was disease-free survival (DFS). Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression models. All P values are two-sided.

Results

During a median follow-up of 7.3 years, 394 patients experienced a DFS event. The hazard ratio for DFS was 1.56 (95% CI = 1.09 to 2.24) for patients consuming three or more servings per day of refined grains compared with patients consuming less than one serving per day (P_trend = .005). The hazard ratio for DFS was 0.89 (95% CI = 0.66 to 1.20) for patients consuming three or more servings per day of whole grains compared with patients consuming less than one serving per day (P_trend = .54). The hazard ratio for DFS of substituting one serving per day of refined grain with one serving per day of whole grain was 0.87 (95% CI = 0.79 to 0.96, P = .007).

Conclusions

The choice of grain consumed may be associated with cancer recurrence and mortality. Future studies are necessary to confirm our findings and to inform the design of randomized trials.

Aerobic Exercise Training Attenuates Tumor Growth and Reduces Insulin Secretion in Walker 256 Tumor-Bearing Rats

Aerobic exercise training can improve insulin sensitivity in many tissues; however, the relationship among exercise, insulin, and cancer cell growth is unclear. We tested the hypothesis that aerobic exercise training begun during adolescence can attenuate Walker 256 tumor growth in adult rats and alter insulin secretion. Thirty-day-old male Wistar rats engaged in treadmill running for 8 weeks, 3 days/week, 44 min/day, at 55-65% VO2max until they were 90 days old (TC, Trained Control). An equivalently aged group was kept inactive during the same period (SC, Sedentary Control). Then, half the animals of the SC and TC groups were reserved as the control condition and the other half were inoculated with Walker 256 cancer cells, yielding two additional groups (Sedentary Walker and Trained Walker). Zero mortalities were observed in tumor-bearing rats. Body weight (BW), food intake, plasma glucose, insulin levels, and peripheral insulin sensitivity were analyzed before and after tumor cell inoculation. We also evaluated tumor growth, metastasis and cachexia. Isolated pancreatic islets secretory activity was analyzed. In addition, we evaluated mechanic sensibility. Our results showed improved physical performance according to the final workload and VO2max and reduced BW in trained rats at the end of the running protocol. Chronic adaptation to the aerobic exercise training decreased tumor weight, cachexia and metastasis and were associated with low glucose and insulin levels and high insulin sensitivity before and after tumor cell inoculation. Aerobic exercise started at young age also reduced pancreatic islet insulin content and insulin secretion in response to a glucose stimulus, without impairing islet morphology in trained rats. Walker 256 tumor-bearing sedentary rats also presented reduced pancreatic islet insulin content, without changing insulin secretion through isolated pancreatic islets. The mechanical sensitivity test indicated that aerobic exercise training did not cause injury or trigger inflammatory processes prior to tumor cell inoculation. Taken together, the current study suggests that aerobic exercise training applied during adolescence may mitigate tumor growth and related disorders in Walker 256 tumor-bearing adult rats. Improved insulin sensibility, lower glucose and insulin levels and/or reduced insulin secretion stimulated by glucose may be implicated in this tumor attenuation.

Does Strength-Promoting Exercise Confer Unique Health Benefits? A Pooled Analysis of Data on 11 Population Cohorts With All-Cause, Cancer, and Cardiovascular Mortality Endpoints

Public health guidance includes recommendations to engage in strength-promoting exercise (SPE), but there is little evidence on its links with mortality. Using data from the Health Survey for England and the Scottish Health Survey from 1994-2008, we examined the associations between SPE (gym-based and own-body-weight strength activities) and all-cause, cancer, and cardiovascular disease mortality. Multivariable-adjusted Cox regression was used to examine the associations between SPE (any, low-/high-volume, and adherence to the SPE guideline (≥2 sessions/week)) and mortality. The core sample comprised 80,306 adults aged ≥30 years, corresponding to 5,763 any-cause deaths (736,463 person-years). Following exclusions for prevalent disease/events occurring in the first 24 months, participation in any SPE was favorably associated with all-cause (hazard ratio (HR) = 0.77, 95% confidence interval (CI): 0.69, 0.87) and cancer (HR = 0.69, 95% CI: 0.56, 0.86) mortality. Adhering only to the SPE guideline was associated with all-cause (HR = 0.79, 95% CI: 0.66, 0.94) and cancer (HR = 0.66, 95% CI: 0.48, 0.92) mortality; adhering only to the aerobic activity guideline (equivalent to 150 minutes/week of moderate-intensity activity) was associated with all-cause (HR = 0.84, 95% CI: 0.78, 0.90) and cardiovascular disease (HR = 0.78, 95% CI: 0.68, 0.90) mortality. Adherence to both guidelines was associated with all-cause (HR = 0.71, 95% CI: 0.57, 0.87) and cancer (HR = 0.70, 95% CI: 0.50, 0.98) mortality. Our results support promoting adherence to the strength exercise guidelines over and above the generic physical activity targets.

A healthy lifestyle index and its association with risk of breast, endometrial, and ovarian cancer among Canadian women

PURPOSE

Several modifiable risk factors have been associated with risk of female cancers, but there is limited data regarding their combined effect on risk among Canadian women. Therefore, we assessed the joint association of modifiable risk factors, using a healthy lifestyle index (HLI) score, with risk of specific reproductive cancers.

METHOD

This study included a subcohort of 3,185 of the 39,618 women, who participated in the Canadian Study of Diet, Lifestyle, and Health, and in whom 410, 177, and 100 postmenopausal breast, endometrial, and ovarian cancers, respectively, were ascertained. We estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards regression models modified for the case-cohort design.

RESULTS

Each unit increase in the HLI score was associated with 3% and 5% reductions in risk of postmenopausal breast cancer and endometrial cancer, respectively (HR 0.97; 95% CI 0.94-0.99 and HR 0.95; 95% CI 0.90-0.99, respectively). Compared to those with HLI score in the lowest category, those in the highest category had 30% and 46% reductions in risk of these cancers, respectively. The HLI score was not associated with altered risk of ovarian cancer.

CONCLUSION

Our findings suggest that promoting a healthy lifestyle may aid in the primary prevention of postmenopausal breast and endometrial cancers.

Lifetime physical inactivity is associated with increased risk for Hodgkin and non-Hodgkin lymphoma: A case-control study

BACKGROUND

Although physical activity is a well-established risk factor for several cancer types, studies evaluating its association with lymphoma have yielded inconclusive results. In such cases where physical activity is not clearly associated with cancer risk in a dose-dependent manner, investigators have begun examining physical inactivity as an independent exposure of interest.

METHODS

Associations of self-reported, lifetime physical inactivity with risk of developing Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) were evaluated in a hospital-based case control study using data from the Patient Epidemiology Data System at Roswell Park Comprehensive Cancer Center. Participants included 87 patients with HL and 236 patients with NHL as well as 348 and 952 cancer-free controls, respectively. Multivariable-adjusted logistic regression models were fit to calculate odds ratios (OR) and 95% confidence intervals (CI) estimating the association between physical inactivity and lymphoma risk.

RESULTS

We observed significant, positive associations between lifetime recreational physical inactivity and risk of both HL (OR = 1.90, 95% CI: 1.15-3.15) and NHL (OR = 1.35, 95% CI: 1.01-1.82).

CONCLUSIONS

The current analysis provides evidence for a positive association between physical inactivity and risk of both HL and NHL. These results add to a growing body of research suggesting that lifetime physical inactivity may be an important independent, modifiable behavioral risk factor for cancer.

Physical activity across the lifespan and liver cancer incidence in the NIH-AARP Diet and Health Study cohort

While liver cancer rates in the United States are increasing, 5‐year survival is only 17.6%, underscoring the importance of prevention. Physical activity has been associated with lower risk of developing liver cancer, but most studies assess physical activity only at a single point in time, often in midlife. We utilized physical activity data from 296,661 men and women in the NIH‐AARP Diet and Health Study cohort to test whether physical activity patterns over the life course could elucidate the importance of timing of physical activity on liver cancer risk. We used group modeling of longitudinal data to create physical activity trajectories using four time points across the life course from teenage years through middle age, identifying seven distinct trajectories. We then used Cox proportional hazards regression to assess the association between the physical activity trajectories and risk of hepatocellular carcinoma, the most common type of liver cancer. We found that, in adjusted analyses, compared to those with consistently low physical activity patterns, those who maintained activity levels over time had a 26–36% lower risk of liver cancer and those who increased physical activity over time had no associations with risk, while those who decreased activity over time had a nonsignificantly higher risk of liver cancer. Our results suggest that sustained physical activity is associated with lower risk of hepatocellular carcinoma, while increasing physical activity later in life may not yield the same benefit. Future research with larger sample sizes and more detailed data on dose and timing of physical activity may continue to yield insight into this association between physical activity and liver cancer risk.

Body mass index throughout adulthood, physical activity, and risk of multiple myeloma: a prospective analysis in three large cohorts

Background

Obesity is the only known modifiable multiple myeloma (MM) risk factor. However, the influence of obesity in earlier or later adulthood and the role of other energy balance correlates in MM development are unclear.

Methods

We leveraged repeatedly updated data from the Nurses’ Health Study, Health Professionals Follow-up Study, and Women’s Health Study cohorts to further explore energy balance measures in MM etiology. Exposures derived from questionnaires included young adult body mass index (BMI), cumulative average BMI, BMI change since young adulthood, and cumulative average physical activity and walking. We assessed MM risk related to those variables with Cox proportional hazard models.

Results

We observed 575 incident MM cases in over five million person-years of follow-up across the cohorts. In pooled analyses, MM risk increased 17% per 5 kg/m² increase in cumulative average BMI (95% confidence interval (CI): 1.05, 1.29) and 28% per 5 kg/m² increase in young adult BMI (CI: 1.12, 1.47); adjustment for BMI change since young adulthood did not affect either association. BMI change since young adulthood and cumulative average physical activity and walking were not significantly associated with MM risk.

Conclusions

These findings suggest that a high BMI in early and later adulthood are risk factors for MM.

Weight, physical activity and breast cancer survival

Weight, weight change and physical activity may affect prognosis among women who are diagnosed with breast cancer. Observational studies show associations between overweight/obesity and weight gain with several measures of reduced prognosis in women with breast cancer, and some suggestions of lower survival in women who are underweight or who experience unexplained weight loss after diagnosis. Observational studies have also shown an association between higher levels of physical activity and reduced breast cancer-specific and all-cause mortality, although a dose–response relationship has not been established. The effects of purposive dietary weight loss and increase in physical activity on survival or recurrence in breast cancer are not yet established, and randomised controlled trials are needed for definitive data. This paper presents the epidemiologic evidence on weight status, weight change, and physical activity and breast cancer survival; suggests potential mediating mechanisms; summarises evidence on weight loss interventions in breast cancer survivors; describes ongoing randomised clinical trials designed to test the effects of weight loss or physical activity on breast cancer survival; and provides information on available guidelines on weight and physical activity for cancer survivors.

Cancer and Exercise: Warburg Hypothesis, Tumour Metabolism and High-Intensity Anaerobic Exercise

There is ample evidence that regular moderate to vigorous aerobic physical activity is related to a reduced risk for various forms of cancer to suggest a causal relationship. Exercise is associated with positive changes in fitness, body composition, and physical functioning as well as in patient-reported outcomes such as fatigue, sleep quality, or health-related quality of life. Emerging evidence indicates that exercise may also be directly linked to the control of tumour biology through direct effects on tumour-intrinsic factors. Beside a multitude of effects of exercise on the human body, one underscored effect of exercise training is to target the specific metabolism of tumour cells, namely the Warburg-type highly glycolytic metabolism. Tumour metabolism as well as the tumour–host interaction may be selectively influenced by single bouts as well as regularly applied exercise, dependent on exercise intensity, duration, frequency and mode. High-intensity anaerobic exercise was shown to inhibit glycolysis and some studies in animals showed that effects on tumour growth might be stronger compared with moderate-intensity aerobic exercise. High-intensity exercise was shown to be safe in patients; however, it has to be applied carefully with an individualized prescription of exercise.

Effects of physical activity on colorectal cancer risk among family history and body mass index subgroups: a systematic review and meta-analysis

Background

Physical activity is consistently associated with a reduced risk of colorectal cancer in epidemiologic studies. This association among higher risk subgroups, such as those with a first-degree family history of colorectal cancer or high body mass index remains unclear.

Methods

We searched MEDLINE for studies examining physical activity and colorectal cancer risk among higher risk subgroups through July 11, 2017. Fifteen and three studies were eligible for inclusion for body mass index and first-degree family history of colorectal cancer subgroups, respectively. Estimates of the highest to lowest comparison of physical activity for each subgroup of risk were pooled using random-effects models.

Results

The pooled associations of physical activity and colorectal cancer risk for those without and with a first-degree family history of colorectal cancer were 0.56 (95% confidence interval (CI) = 0.39–0.80) and 0.72 (95% CI = 0.39–1.32), respectively (p_{heterogeneity} = 0.586). The pooled associations of physical activity and colorectal cancer risk for the low and high body mass index groups were 0.74 (95% CI = 0.66–0.83) and 0.65 (95% CI = 0.53–0.79), respectively (p_{heterogeneity} = 0.389).

Conclusions

Overall, a stronger relative risk of physical activity on colorectal cancer risk was observed in the higher body mass index group, although the difference was not statistically significant, suggesting an added benefit of physical activity as a cancer prevention strategy in population groups with strong risk factors for colorectal cancer. Additional research among these subgroups is warranted.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3970-5) contains supplementary material, which is available to authorized users.

Relationship between physical activity, disability, and physical fitness profile in sedentary Latina breast cancer survivors

OBJECTIVE

To report baseline data from a physical activity (PA) intervention for Latina breast cancer survivors, and assess the relationship between PA, fitness, and disability.

METHODS

Eighty-nine Latina breast cancer survivors from San Juan, PR and Houston, TX (age: 55.4 ± 9.9 years; BMI: 29.87 ± 5.62 kg/m²; ≥ 3 months post-treatment) participated in this study. At baseline participants completed fitness testing (six-minute walk test [6MWT], 30-second sit-stand; grip strength, lower and upper extremity and low back strength, shoulder range of motion, balance testing), and assessment of physical activity (PA) and disability. PA was assessed using the International Physical Activity Questionnaire (IPAQ). A subsample (n = 27) received an accelerometer to compare objective versus self-reported PA.

RESULTS

Participants exhibited low PA (M = 76.5 MET·minutes/week; SD = 183.4), poor fitness (6MWT M = 436.4 meters, SD = 99.1; 30s sit-stand, M = 11.6 stands, SD = 3.1), and no detectable disability. In an adjusted model lower extremity fitness was associated with PA, with a one repetition increase in sit-to-stand associated with 49 additional minutes of self-reported PA plus walking per week. The correlation between IPAQ moderate-vigorous PA and accelerometer was 0.38 (p = 0.047).

CONCLUSION

Latina breast cancer survivors have low physical activity and fitness levels that increase their risk of disability, cardiometabolic comorbidities, and potential cancer recurrence.

Molecular Mechanisms Linking Exercise to Cancer Prevention and Treatment

The benefits of exercise training for cancer patients are becoming increasingly evident. Physical exercise has been shown to reduce cancer incidence and inhibit tumor growth. Here we provide the status of the current molecular understanding of the effect of exercise on cancer. We propose that exercise has a role in controlling cancer progression through a direct effect on tumor-intrinsic factors, interplay with whole-body exercise effects, alleviation of cancer-related adverse events, and improvement of anti-cancer treatment efficacy. These findings have wide-ranging societal implications, as this understanding may lead to changes in cancer treatment strategies.

Objective Measures of Physical Activity and Cardiometabolic and Endocrine Biomarkers

PURPOSE

Although physical activity is an established risk factor for chronic disease prevention, the specific mechanisms underlying these relationships are poorly understood. We examined the associations between total activity counts and moderate-vigorous physical activity (MVPA) measured by accelerometer, and physical activity energy expenditure measured by doubly labeled water, with plasma levels of proinsulin, insulin, c-peptide, insulin growth factor binding protein-3, insulin growth factor-1, adiponectin, leptin, and leptin-sR.

METHODS

We conducted a cross-sectional analysis of 526 healthy US women in the Women's Lifestyle Validation Study, 2010 to 2012. We performed multiple linear regression models adjusting for potential lifestyle and health-related confounders to assess the associations between physical activity, measured in quartiles (Q) and biomarkers.

RESULTS

Participants in Q4 versus Q1 of total activity counts had lower proinsulin (-20%), c-peptide (-7%), insulin (-31%), and leptin (-46%) levels, and higher adiponectin (55%), leptin-sR (25%), and insulin growth factor-1 (9.6%) levels (all P trend ≤ 0.05). Participants in Q4 versus Q1 of MVPA had lower proinsulin (-26%), c-peptide (-7%), insulin (-32%), and leptin (-40%) levels, and higher adiponectin (31%) and leptin-sR (22%) levels (all P trend ≤ 0.05). Further adjustment for body mass index (BMI) attenuated these associations, but the associations with adipokines remained significant. Those in Q4 versus Q1 of physical activity energy expenditure had lower leptin (-21%) and higher leptin-sR (10%) levels (all P trend ≤ 0.05), after additional adjustment for BMI. In the sensitivity analysis, the associations were similar but attenuated when physical activity was measured using the subjective physical activity questionnaire.

CONCLUSIONS

Our data suggest that greater physical activity is modestly associated with favorable levels of cardiometabolic and endocrine biomarkers, where the strongest associations were found with accelerometer-measured physical activity. These associations may be only partially mediated through BMI, further supporting the role of physical activity in the reduction of cardiometabolic and endocrine disease risk, independent of adiposity.

Influence of physical activity on the immune system in breast cancer patients during chemotherapy

PURPOSE

Physical activity can impact the immune system in different ways, e.g. by alteration of the humoral and cellular immune response. Physical activity at medium intensity enhances numbers of cytotoxic T cells, NK cells and macrophages in healthy people. The aim of this study was to compare the effects of endurance and resistance training on the immune system in breast cancer patients during adjuvant chemotherapy.

METHODS

In a prospective, controlled and randomized intervention exploratory trial, 12-week supervised endurance or resistance training were compared with usual care twice a week. Endpoints were the absolute numbers of the immune cells such as CD3⁺ T lymphocytes including CD4⁺- and CD8⁺, αβ T cells, γδT cells, CD3^-/CD16⁺/56⁺ NK cells and CD19⁺ B cells, before and after 12 weeks of treatment. Cell numbers were analyzed using fluorescence-activated cell sorting.

RESULTS

Despite different physical interventions in all groups immune cell count decreased in CD3 T cells including TCR αβ and CD4 T cells, NK cells and CD19 B cells 12 weeks after initiation of chemotherapy and start of the physical intervention program, while the reduction of γδ T cells and CD8 T cells is less prominent in the RT and UC group.

CONCLUSION

Chemotherapy led to a decrease in nearly all measured immune cells. In this study, physical intervention with endurance or resistance training did not suppress cellular immunity any further. Larger multicenter trials are needed to evaluate the exact impact of sports intervention on immune cell subpopulations.

Obesity, Diabetes and Gastrointestinal Malignancy: The role of Metformin and other Anti-diabetic Therapy

The association between Diabetes and cancer has been known for decades with obesity and insulin resistance being postulated as the main underlying risk factors for both disorders. With rise of the epidemic of obesity in the USA and around the globe, there has been a rise in diabetes that is currently reaching epidemic proportions. Diabetes is known to be associated with increased risk of several types of malignancy including breast, cervical, pancreatic and colon cancer. In this review, we discuss the epidemic of obesity and its consequential epidemic of diabetes highlighting the pathophysiologic mechanisms of increased cancer in the diabetic population. We will then discuss the role of insulin therapy as well as, other antidiabetic medications, particularly metformin that has been to be associated with lower risk as well as better survival with GI malignancies based on several studies including a study that was recently published by our group.

LIFETIME PHYSICAL INACTIVITY IS ASSOCIATED WITH LUNG CANCER RISK AND MORTALITY

INTRODUCTION

Investigations of the independent associations of physical inactivity with cancer endpoints have been mounting in the epidemiological literature, in part due to the high prevalence of physical inactivity among cancer patients and to evidence that inactivity associates with carcinogenesis via pathways independent of obesity. Yet, physical inactivity is not currently recognized as a well-established risk or prognostic factor for lung cancer. As such, we examined the associations of lifetime physical inactivity with lung cancer risk and mortality in a hospital-based, case-control study.

PRESENTATION OF CASE

Materials and Methods: The analyses included data from 660 lung cancer patients and 1335 matched cancer-free controls. Multivariable logistic regression analyses were utilized to assess the association between lifetime physical inactivity and lung cancer risk, and Cox proportional hazards models were utilized to estimate the association between lifetime physical inactivity and mortality among lung cancer cases.Results: We observed a significant positive association between lifetime physical inactivity and lung cancer risk: [Odds ratio (OR)=2.23, 95% confidence interval (CI): 1.77-2.81]; the association remained significant among never smokers (OR=3.00, 95% CI:1.33-6.78) and non-smokers (OR=2.33, 95% CI: 1.79-3.02). We also observed a significant positive association between lifetime physical inactivity and lung cancer mortality [Hazard ratio (HR)=1.40, 95% CI: 1.14-1.71]; the association remained significant in non-smokers (HR=1.51, 95% CI: 1.16-1.95).

DISCUSSION/CONCLUSION

These data add to the body of evidence suggesting that physical inactivity is an independent risk and prognostic factor for cancer. Additional research utilizing prospectively collected data is needed to substantiate the current findings.

Physical activity, mediating factors and risk of colon cancer: insights into adiposity and circulating biomarkers from the EPIC cohort

Background

There is convincing evidence that high physical activity lowers the risk of colon cancer; however, the underlying biological mechanisms remain largely unknown. We aimed to determine the extent to which body fatness and biomarkers of various biologically plausible pathways account for the association between physical activity and colon cancer.

Methods

We conducted a nested case-control study in a cohort of 519 978 men and women aged 25 to 70 years followed from 1992 to 2003. A total of 713 incident colon cancer cases were matched, using risk-set sampling, to 713 controls on age, sex, study centre, fasting status and hormonal therapy use. The amount of total physical activity during the past year was expressed in metabolic equivalent of task [MET]-h/week. Anthropometric measurements and blood samples were collected at study baseline.

Results

High physical activity was associated with a lower risk of colon cancer: relative risk ≥91 MET-h/week vs <91 MET-h/week = 0.75 [95% confidence interval (CI): 0.57 to 0.96]. In mediation analyses, this association was accounted for by waist circumference: proportion explained effect (PEE) = 17%; CI: 4% to 52%; and the biomarkers soluble leptin receptor (sOB-R): PEE = 15%; 95% CI: 1% to 50% and 5-hydroxyvitamin D (25[OH]D): PEE = 30%; 95% CI: 12% to 88%. In combination, these factors explained 45% (95% CI: 20% to 125%) of the association. Beyond waist circumference, sOB-R and 25[OH]D additionally explained 10% (95% CI: 1%; 56%) and 23% (95% CI: 6%; 111%) of the association, respectively.

Conclusions

Promoting physical activity, particularly outdoors, and maintaining metabolic health and adequate vitamin D levels could represent a promising strategy for colon cancer prevention.

Dietary Weight Loss, Exercise, and Oxidative Stress in Postmenopausal Women: A Randomized Controlled Trial

Oxidative stress, a potential mechanism linking obesity and cancer, results from an imbalance between activation/inactivation of reactive oxygen species, byproducts of cellular metabolism. In a randomized controlled trial, we investigated effects of diet and/or exercise on biomarkers of oxidative stress. A total of 439 overweight/obese [body mass index (BMI) > 25 kg/m²] postmenopausal women, ages 50 of 75 years, were randomized to 12 months of (i) reduced-calorie weight loss diet ("diet"; n = 118); (ii) moderate-to-vigorous intensity aerobic exercise ("exercise"; n = 117); (iii) combined diet and exercise intervention ("diet + exercise"; n = 117); or (iv) control (n = 87). Outcomes were circulating markers of oxidative stress, including fluorescent oxidation products (FOP), F₂-isoprostanes, and oxidized low-density lipoprotein (LDL). On average, participants were 57.9 years, with a BMI of 30.9 kg/m² F₂-isprostanes were significantly reduced in the diet (-22.7%, P = 0.0002) and diet + exercise (-23.5%, P < 0.0001) arms versus controls (-2.99%) and nonsignificantly reduced in the exercise arm (-14.5%, P = 0.01). Participants randomized to the diet and diet + exercise arms had significant increases in levels of FOP [control -5.81%; diet +14.77% (P = 0.0001); diet + exercise +17.45%, (P = 0.0001)]. In secondary analyses, increasing weight loss was statistically significantly associated with linear trends of greater reductions in oxidized LDL and in F₂-isoprostanes and increases in FOP. Compared with controls, exercise participants whose maximal oxygen consumption increased had significant decreases in levels of F₂-isoprostanes and in oxidized LDL and increases in FOP. Dietary weight loss, with or without exercise, significantly reduced some markers of oxidative stress in postmenopausal women. Cancer Prev Res; 9(11); 835-43. ©2016 AACR.

Physical activity among cancer survivors-what is their perception and experience?

PURPOSE

Physical activity (PA) plays an important role relating to cancer. The aim of this study was to investigate the attitude to and experience with the subject of PA in cancer in a large group of tumour patients.

METHODS

A standardised questionnaire was carried out and distributed to patients online and in printed form.

RESULTS

Nine hundred five patients answered the questionnaire. Most tumour patients (60%) received information about PA after their cancer therapy. The Internet was often rated to be inadequate as a source of information. One in two tumour patients were recommended PA by a therapist. During the acute phase, the majority (57% of the 776) did not receive a sport-therapeutic exercise programme. Two thirds (68%) of the 898 patients indicated regularly engaging in PA at least 3 or 5 days per week. In most cases (30% of the 787), 2 to 4 h per week were dedicated to PA. In addition to a desire to increase well-being, enjoyment played a large role. Weakness and lack of willpower are among the most common barriers. Most tumour patients confirmed that PA improved their body awareness (58%) or gave them the feeling that they could do something to better cope with the disease (61%) or feel better (68%).

CONCLUSION

On the one hand, the information requirements of tumour patients with respect to PA have not been adequately taken into account by practitioners. On the other hand, there are still subjective inhibitions on the part of the patients, which keep them from engaging in PA.

The Effects of Resistance Exercise on Biomarkers of Breast Cancer Prognosis: A Pooled Analysis of Three Randomized Trials

Background: Using a secondary data analysis from randomized controlled trials comparing one year of resistance exercise (n = 109) to a placebo control condition (n = 106) in postmenopausal, posttreatment breast cancer survivors, we investigated the influence of resistance training and changes in body composition on markers associated with cancer progression.Methods: Measures included serum levels of insulin, IGF-1, IGFBP1-3, leptin, serum amyloid A (SAA), adiponectin, C-reactive protein (CRP), IL1β, TNFα, IL6, and IL8, and body composition (total, lean and fat mass in kg) by DXA at baseline, 6, and 12 months. Linear mixed effects models were used to examine the association between group, biomarkers, and body composition and whether or not changes in muscle strength or body composition influenced the effect of exercise on biomarkers.Results: CRP decreased over time among women participating in resistance training compared with increases in controls (P = 0.045). In stratified analyses and compared with increases in controls, women who gained strength reduced CRP (P = 0.003) and maintained levels of IL1β and IL6. Among exercisers who lost weight (≥2 kg), CRP (P = 0.045), leptin (P < 0.01), and SAA (P = 0.029) decreased, whereas IGF-BP1 (P = 0.036) increased compared with controls.Conclusions: Resistance training may lower inflammation and improve insulin pathway profiles, but the magnitude and degree of benefit from exercise may depend upon whether or not women gained strength, a possible marker of compliance with training, and/or lost weight during exercise.Impact: Future resistance training trials should consider these potential influencing factors as they may determine how well exercise can slow cancer progression and prevent disease recurrence. Cancer Epidemiol Biomarkers Prev; 27(2); 146-53. ©2017 AACR.

Exercise-Induced Catecholamines Activate the Hippo Tumor Suppressor Pathway to Reduce Risks of Breast Cancer Development

Strong epidemiologic evidence documents the protective effect of physical activity on breast cancer risk, recurrence, and mortality, but the underlying mechanisms remain to be identified. Using human exercise-conditioned serum for breast cancer cell incubation studies and murine exercise interventions, we aimed to identify exercise factors and signaling pathways involved in the exercise-dependent suppression of breast cancer. Exercise-conditioned serum from both women with breast cancer (n = 20) and healthy women (n = 7) decreased MCF-7 (hormone-sensitive) and MDA-MB-231 (hormone-insensitive) breast cancer cell viability in vitro by 11% to 19% and reduced tumorigenesis by 50% when preincubated MCF-7 breast cancer cells were inoculated into NMRI-Foxn1^nu mice. This exercise-mediated suppression of cell viability and tumor formation was completely blunted by blockade of β-adrenergic signaling in MCF-7 cells, indicating that catecholamines were the responsible exercise factors. Both epinephrine (EPI) and norepinephrine (NE) could directly inhibit breast cancer cell viability, as well as tumor growth in vivo EPI and NE activate the tumor suppressor Hippo signaling pathway, and the suppressive effect of exercise-conditioned serum was found to be mediated through phosphorylation and cytoplasmic retention of YAP and reduced expression of downstream target genes, for example, ANKRD1 and CTGF. In parallel, tumor-bearing mice with access to running wheels showed reduced growth of MCF-7 (-36%, P < 0.05) and MDA-MB-231 (-66%, P < 0.01) tumors and, for the MCF-7 tumor, increased regulation of the Hippo signaling pathway. Taken together, our findings offer a mechanistic explanation for exercise-dependent suppression of breast cancer cell growth. Cancer Res; 77(18); 4894-904. ©2017 AACR.

Sitting time and occupational and recreational physical activity in relation to the risk of esophageal squamous cell carcinoma

Backgrounds

Sitting time and physical activity are associated with cancer risk; however, their roles in the development of esophageal squamous cell carcinoma (ESCC) are inconclusive. This study aimed to investigate the effects of total sitting time, occupational activity time (OAT), and recreational activity time (RAT) on ESCC risk.

Methods

Five hundred fifty-seven ESCC patients and 543 healthy controls matched by sex and age were recruited for this study. Conditional logistic regression was performed to obtain odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Longer total sitting time (adjusted OR [AOR] 2.54, 95% CI 1.58–4.09) and longer OAT (AOR 2.90, 95% CI 2.11–3.99) were associated with higher ESCC risk, while longer RAT (AOR 0.27, 95% CI 0.19–0.38) could reduce ESCC risk. When the body mass index was incorporated into the multivariable models, the results changed slightly. In risk estimation according to sex, the same trends were observed in both men and women. Furthermore, longer RAT could completely or partially diminish the impacts of longer sitting time and OAT on increasing ESCC risk.

Conclusion

Long sitting time and long OAT can increase the risk of ESCC, while long RAT is significantly associated with decreased ESCC risk.

Inherent aerobic capacity-dependent differences in breast carcinogenesis

Although regular physical activity is associated with improvement in aerobic capacity and lower breast cancer risk, there are heritable sets of traits that affect improvement in aerobic capacity in response to physical activity. Although aerobic capacity segregates risk for a number of chronic diseases, the effect of the heritable component on cancer risk has not been evaluated. Therefore, we investigated breast carcinogenesis in rodent models of heritable fitness in the absence of induced physical activity. Female offspring of N:NIH rats selectively bred for low (LIAC) or high (HIAC) inherent aerobic capacity were injected intraperitoneally with 1-methyl-1-nitrosurea (70 mg/kg body wt). At study termination 33 weeks post-carcinogen, cancer incidence (14.0 versus 47.3%; P < 0.001) and multiplicity (0.18 versus 0.85 cancers per rat; P < 0.0001) were significantly decreased in HIAC versus LIAC rats, respectively. HIAC had smaller visceral and subcutaneous body fat depots than LIAC and activity of two proteins that regulated the mammalian target of rapamycin, protein kinase B (Akt), and adenosine monophosphate-activated protein kinase were suppressed and activated, respectively, in HIAC. Although many factors distinguish between HIAC and LIAC, it appears that the protective effect of HIAC against breast carcinogenesis is mediated, at least in part, via alterations in core metabolic signaling pathways deregulated in the majority of human breast cancers.

Exercise-dependent regulation of the tumour microenvironment

The integrity and composition of the tumour microenvironment (TME) is highly plastic, undergoing constant remodelling in response to instructive signals derived from alterations in the availability and nature of systemic host factors. This 'systemic milieu' is directly modulated by host exposure to modifiable lifestyle factors such as exercise. Host exposure to regular exercise markedly reduces the risk of the primary development of several cancers and might improve clinical outcomes following a diagnosis of a primary disease. However, the molecular mechanisms that underpin the apparent antitumour effects of exercise are poorly understood. In this Opinion article, we explore the putative effects of exercise in reprogramming the interaction between the host and the TME. Specifically, we speculate on the possible effects of exercise on reprogramming 'distant' tissue microenvironments (those not directly involved in the exercise response) by analysing how alterations in the systemic milieu might modulate key TME components to influence cancer hallmarks.

Cross-country skiing is associated with lower all-cause mortality: A population-based follow-up study

The prospective relationship between leisure-time cross-country skiing and any fatal events is uncertain. We aimed to assess the associations of leisure-time cross-country skiing habits with the risk of all-cause mortality in a general population. A 12-month physical activity questionnaire was used at baseline to assess the frequency, average duration, and intensity of cross-country skiing in a prospective population-based cohort of 2087 middle-aged men from eastern Finland. Hazard ratios (HRs; 95% confidence intervals) were calculated for all-cause mortality. During a median (interquartile range) follow-up of 26.1 (18.7-28.0) years, 1028 all-cause mortality outcomes were recorded. In analyses adjusted for several established risk factors and other potential confounders, when compared to men who did not do any cross-country skiing, the HRs (95% CIs) of all-cause mortality were 0.84 (0.73-0.97) and 0.80 (0.67-0.96) for men who did 1-200 and >200 metabolic equivalent-hours per year of cross-country skiing, respectively. Similarly, compared to men who did not do any cross-country skiing, the corresponding adjusted HRs (95% CIs) for all-cause mortality were 0.84 (0.72-0.97) and 0.82 (0.69-0.97) for men who did 1-60 min/wk and >60 min/wk of cross-country skiing, respectively. The associations were similar across several subgroups, except for evidence of effect modification by body mass index and history of diabetes. Total volume as well as duration of leisure-time cross-country skiing is each inversely and independently associated with all-cause mortality in a middle-aged Caucasian male population.

Exercise protects from cancer through regulation of immune function and inflammation

Exercise training has been extensively studied in cancer settings as part of prevention or rehabilitation strategies, yet emerging evidence suggests that exercise training can also directly affect tumor-specific outcomes. The underlying mechanisms for this exercise-dependent cancer protection are just starting to be elucidated. To this end, evasion of immune surveillance and tumor-associated inflammation are established as hallmarks of cancer, and exercise may target cancer incidence and progression through regulation of these mechanisms. Here, I review the role of exercise in protection from cancer through mobilization and activation of cytotoxic immune cells, restriction of inflammatory signaling pathways in myeloid immune cells, and regulation of acute and chronic systemic inflammatory responses. In conclusion, I propose that exercise has the potential to target tumor growth through regulation of immune and inflammatory functions, and exercise may be pursued as anticancer treatment through incorporation into standard oncological therapy to the benefit of the cancer patients.

Significantly enhanced lung metastasis and reduced organ NK cell functions in diet-induced obese rats

BACKGROUND

Obesity was identified as a major risk factor for malignant diseases, but underlying mechanisms remain unclear. Natural killer (NK) cells, a pivotal aspect of innate immunity, are capable of identifying and killing virally infected and tumor cells. Previous studies have shown altered NK cell functions in obesity, and the current study aimed to investigate the relationship between altered NK cell functions and increased cancer risk in obesity.

METHODS

To induce obesity male F344-rats received a high-fat diet (34% fat) or a control diet (4% fat). Thereafter, syngeneic mammary adenocarcinoma cells (MADB106) or a vehicle were intravenously (i.v.) injected. 15 min after injection, half of each group of rats were killed, lungs removed and immunohistochemically stained. Numbers of NK cells, MADB106 cells and NK cell-tumor cell interactions were quantified. Twenty-one days after tumor-cell injection the other half group of rats was killed and lung metastases were counted and relative mRNA concentrations of different NK cell receptors were determined.

RESULTS

After short-term MADB106-challenge, DIO fed animals showed significantly decreased NK cell numbers in the blood and NK cell-tumor cell interactions in the lung as compared to their control littermates. Twenty-one days after MADB106 injection, the lungs of the DIO fed rats showed significantly more lung metastases compared to control animals, accompanied by reduced relative mRNA concentrations of the activating NK cell receptor NKG2D.

CONCLUSIONS

We conclude that induction of obesity in F344-rats leads to reduced lung NK cell function against tumor cells and results in significantly enhanced lung metastasis as compared to lean animals. It can be hypothesized that obesity-induced altered NK cell functions play an important role in cancer growth and metastasis.

Does Regular Exercise Counter T Cell Immunosenescence Reducing the Risk of Developing Cancer and Promoting Successful Treatment of Malignancies?

Moderate intensity aerobic exercise training or regular physical activity is beneficial for immune function. For example, some evidence shows that individuals with an active lifestyle exhibit stronger immune responses to vaccination compared to those who are inactive. Encouragingly, poor vaccine responses, which are characteristic of an ageing immune system, can be improved by single or repeated bouts of exercise. In addition, exercise-induced lymphocytosis, and the subsequent lymphocytopenia, is thought to facilitate immune surveillance, whereby lymphocytes search tissues for antigens derived from viruses, bacteria, or malignant transformation. Aerobic exercise training is anti-inflammatory and is linked to lower morbidity and mortality from diseases with infectious, immunological, and inflammatory aetiologies, including cancer. These observations have led to the view that aerobic exercise training might counter the age-associated decline in immune function, referred to as immunosenescence. This article summarises the aspects of immune function that are sensitive to exercise-induced change, highlighting the observations which have stimulated the idea that aerobic exercise training could prevent, limit, or delay immunosenescence, perhaps even restoring aged immune profiles. These potential exercise-induced anti-immunosenescence effects might contribute to the mechanisms by which active lifestyles reduce the risk of developing cancer and perhaps benefit patients undergoing cancer therapy.

Cancers of the Esophagus and Stomach: Potential Mechanisms Behind the Beneficial Influence of Physical Activity

OBJECTIVE

To compare findings from several recent meta-analyses showing a reduced risk of gastric and esophageal cancers in physically active individuals, to assess the magnitude of this benefit, and to seek information on potential underlying mechanisms.

DATA SOURCES

A comprehensive search of Ovid/Medline from 1996 to February 2016, using the terms physical activity or exercise or training and esophageal or gastric cancer, and supplementing the articles identified by material from references lists and personal files.

MAIN RESULTS

Moderate-to-vigorous physical activity is associated with a 20% to 30% reduction in the risk of gastroesophageal adenocarcinomas, with a significant dose/response relationship. Benefit is greater in women than in men, and greater for noncardia than for cardia or esophageal tumors. Mechanisms could include a reduction of visceral fat (with a lesser production of cancer promoting hormones and reduced gastroesophageal reflux) and/or a lesser likelihood of smoking and excessive alcohol consumption. Physical activity does not protect against Helicobacter pylori infections or gastric ulceration, but mechanisms related to the impact of exercise on immune function, antioxidant mechanisms, and gastroesophageal reflux remain to be explored.

CONCLUSIONS

Regular, moderate-to-vigorous physical activity is associated with a clinically significant reduction in the risk of gastroesophageal adenocarcinomas, but mechanisms are as yet unclear, and a causal relationship remains to be proven.