Differential response to exercise in claudin-low breast cancer

Advances in Diet and Physical Activity in Breast Cancer Prevention and Treatment

There is currently a growing interest in diets and physical activity patterns that may be beneficial in preventing and treating breast cancer (BC). Mounting evidence indicates that indeed, the so-called Mediterranean diet (MedDiet) and regular physical activity likely both help reduce the risk of developing BC. For those who have already received a BC diagnosis, these interventions may decrease the risk of tumor recurrence after treatment and improve quality of life. Studies also show the potential of other dietary interventions, including fasting or modified fasting, calorie restriction, ketogenic diets, and vegan or plant-based diets, to enhance the efficacy of BC therapies. In this review article, we discuss the biological rationale for utilizing these dietary interventions and physical activity in BC prevention and treatment. We highlight published and ongoing clinical studies that have applied these lifestyle interventions to BC patients. This review offers valuable insights into the potential application of these dietary interventions and physical activity as complimentary therapies in BC management.

Heart failure pharmacotherapy and cancer: pathways and pre-clinical/clinical evidence

Heart failure (HF) patients have a significantly higher risk of new-onset cancer and cancer-associated mortality, compared to subjects free of HF. While both the prevention and treatment of new-onset HF in patients with cancer have been investigated extensively, less is known about the prevention and treatment of new-onset cancer in patients with HF, and whether and how guideline-directed medical therapy (GDMT) for HF should be modified when cancer is diagnosed in HF patients. The purpose of this review is to elaborate and discuss the effects of pillar HF pharmacotherapies, as well as digoxin and diuretics on cancer, and to identify areas for further research and novel therapeutic strategies. To this end, in this review, (i) proposed effects and mechanisms of action of guideline-directed HF drugs on cancer derived from pre-clinical data will be described, (ii) the evidence from both observational studies and randomized controlled trials on the effects of guideline-directed medical therapy on cancer incidence and cancer-related outcomes, as synthetized by meta-analyses will be reviewed, and (iii) considerations for future pre-clinical and clinical investigations will be provided.

Physical Exercise and Tumor Energy Metabolism

Evidence supports the antitumoral effects of physical activity, either in experimental animal models or humans. However, the biological mechanisms by which physical exercise modulates tumoral development are still unclear. An important feature of the tumor cells is the altered energy metabolism, often associated with definitions of tumor aggressiveness. Nevertheless, exercise can cause global metabolic changes in the body, as well as modulate tumor metabolism. Here we specifically discuss the metabolic changes found in tumors and how exercise can contribute to anti-tumoral effects by modulating the mitochondrial function, and tricarboxylic acid cycle-related metabolites of cancer cells. The effect of physical exercise on tumor metabolism is a new possibility for comprehension of cancer biology and developing therapies focused on tumor energy metabolism.

Normal tissue and tumor microenvironment adaptations to aerobic exercise enhance doxorubicin anti-tumor efficacy and ameliorate its cardiotoxicity in retired breeder mice

Aerobic exercise is receiving increased recognition in oncology for its multiple purported benefits. Exercise is known to induce physiologic adaptations that improve patient quality-of-life parameters as well as all-cause mortality. There also is a growing body of evidence that exercise may directly alter the tumor microenvironment to influence tumor growth, metastasis, and response to anticancer therapies. Furthermore, the physiologic adaptations to exercise in normal tissues may protect against treatment-associated toxicity and allow for greater treatment tolerance. However, the exercise prescription required to induce these beneficial tumor-related outcomes remains unclear. This study characterized the aerobic adaptations to voluntary wheel running in normal tissues and the tumor microenvironment. Female, retired breeder BALB/c mice and syngeneic breast adenocarcinoma cells were utilized in primary tumor and metastasis models. Aerobic exercise was found to induce numerous adaptations across various tissues in these mice, although primary tumor growth and metastasis were largely unaffected. However, intratumoral hypoxia and global metabolism were altered in the tumors of exercising hosts relative to non-wheel running controls. Doxorubicin chemotherapy also was found to be more efficacious at delaying tumor growth with adjuvant aerobic exercise. Additionally, doxorubicin-induced cardiac toxicity was ameliorated in exercising hosts relative to non-wheel running controls. Taken together, these data suggest that the normal tissue and tumor microenvironment adaptations to aerobic exercise can improve doxorubicin efficacy while simultaneously limiting its toxicity.

Exercise Training Improves Tumor Control by Increasing CD8+ T-cell Infiltration via CXCR3 Signaling and Sensitizes Breast Cancer to Immune Checkpoint Blockade

The mechanisms behind the antitumor effects of exercise training (ExTr) are not fully understood. Using mouse models of established breast cancer, we examined here the causal role of CD8+ T cells in the benefit acquired from ExTr in tumor control, as well as the ability of ExTr to improve immunotherapy responses. We implanted E0771, EMT6, MMTV-PyMT, and MCa-M3C breast cancer cells orthotopically in wild-type or Cxcr3-/- female mice and initiated intensity-controlled ExTr sessions when tumors reached approximately 100 mm3 We characterized the tumor microenvironment (TME) using flow cytometry, transcriptome analysis, proteome array, ELISA, and immunohistochemistry. We used antibodies against CD8+ T cells for cell depletion. Treatment with immune checkpoint blockade (ICB) consisted of anti-PD-1 alone or in combination with anti-CTLA-4. ExTr delayed tumor growth and induced vessel normalization, demonstrated by increased pericyte coverage and perfusion and by decreased hypoxia. ExTr boosted CD8+ T-cell infiltration, with enhanced effector function. CD8+ T-cell depletion prevented the antitumor effect of ExTr. The recruitment of CD8+ T cells and the antitumor effects of ExTr were abrogated in Cxcr3-/- mice, supporting the causal role of the CXCL9/CXCL11-CXCR3 pathway. ExTr also sensitized ICB-refractory breast cancers to treatment. Our results indicate that ExTr can normalize the tumor vasculature, reprogram the immune TME, and enhance the antitumor activity mediated by CD8+ T cells via CXCR3, boosting ICB responses. Our findings and mechanistic insights provide a rationale for the clinical translation of ExTr to improve immunotherapy of breast cancer.

Dual-emissive, oxygen-sensing boron nanoparticles quantify oxygen consumption rate in breast cancer cells

SIGNIFICANCE

Decreasing the oxygen consumption rate (OCR) of tumor cells is a powerful method for ameliorating tumor hypoxia. However, quantifying the change in OCR is challenging in complex experimental systems.

AIM

We present a method for quantifying the OCR of two tumor cell lines using oxygen-sensitive dual-emissive boron nanoparticles (BNPs). We hypothesize that our BNP results are equivalent to the standard Seahorse assay.

APPROACH

We quantified the spectral emissions of the BNP and accounted for external oxygen diffusion to quantify OCR over 24 h. The BNP-computed OCR of two breast cancer cell lines, E0771 and 4T07, were compared with their respective Seahorse assays. Both cell lines were also irradiated to quantify radiation-induced changes in the OCR.

RESULTS

Using a Bland-Altman analysis, our BNPs OCR was equivalent to the standard Seahorse assay. Moreover, in an additional experiment in which we irradiated the cells at their 50% survival fraction, the BNPs were sensitive enough to quantify 24% reduction in OCR after irradiation.

CONCLUSIONS

Our results conclude that the BNPs are a viable alternative to the Seahorse assay for quantifying the OCR in cells. The Bland-Altman analysis showed that these two methods result in equivalent OCR measurements. Future studies will extend the OCR measurements to complex systems including 3D cultures and in vivo models, in which OCR measurements cannot currently be made.

EO771, is it a well-characterized cell line for mouse mammary cancer model? Limit and uncertainty

Among mouse mammary tumor models, syngeneic cell lines present an advantage for the study of immune response. However, few of these models are well characterized. The tumor line EO771 is derived from spontaneous breast cancer of C57BL/6 mice. These cells are widely used but are referenced under different names: EO771, EO 771, and E0771. The characteristics of the EO771 cells are well described but some data are contradictory. This cell line presents the great interest of developing an immunocompetent neoplastic model using an orthotopic implantation reflecting the mammary tumors encountered in breast cancer patients. This review presents the phenotype characteristics of EO771 and its sensitivity to nutrients and different therapies such as radiotherapy, chemotherapy, hormone therapy, and immunotherapy.

Exercise and immunometabolic regulation in cancer

Unhealthful lifestyle factors, such as obesity, disrupt organismal homeostasis and accelerate cancer pathogenesis, partly through metabolic and immunological dysregulation. Exercise is a prototypical strategy that maintains and restores homeostasis at the organismal, tissue, cellular and molecular levels and can prevent or inhibit numerous disease conditions, including cancer. Here, we review unhealthful lifestyle factors that contribute to metabolic and immunological dysregulation and drive tumourigenesis, focusing on patient physiology (host)-tissue-tumour microenvironment interactions. We also discuss how exercise may influence distant tissue microenvironments, thereby improving tissue function through both metabolic and immunospecific pathways. Finally, we consider future directions that merit consideration in basic and clinical translational exercise studies.

Early intervention exercise training does not delay prostate cancer progression in Pten-/- mice

BACKGROUND

There is convincing evidence that men with advanced prostate cancer experience improved quality of life as a result of exercise therapy, although there is limited preclinical, and no clinical, data to directly support the notion that exercise training improves prostate cancer prognosis or outcome. The aim of this study was to investigate the effect of regular exercise training on the early stages of prostate cancer progression, as well as assessing whether alterations to prostate cancer metabolism are induced by exercise.

METHODS

Mice with prostate-specific deletion of Pten (Pten^-/- ) remained sedentary or underwent 6 weeks of endurance exercise training or high-intensity exercise training involving treadmill running. At the conclusion of the training period, the prostate lobes were excised. A portion of fresh tissue was used to assess glucose, glutamine, and fatty acid metabolism by radiometric techniques and a second portion was fixed for histopathology.

RESULTS

Despite the implementation of an effective exercise regime, as confirmed by improvements in running capacity, neither prostate mass, cell proliferation or the incidence of high-grade prostate intraepithelial hyperplasia or noninvasive carcinoma in situ were significantly different between groups. Similarly, neither glucose uptake, oxidation and de novo lipogenesis, glutamine oxidation, or fatty acid uptake, oxidation and storage into various lipids were significantly different in prostate tissue obtained from untrained and exercise trained mice.

CONCLUSIONS

These results show that 6 weeks of moderate or high-intensity exercise training does not alter substrate metabolism in the prostate or slow the progression of Pten-null prostate cancer. These results question whether exercise is a useful therapy to prevent or delay prostate cancer progression.

Suppressing breast cancer by exercise: consideration to animal models and exercise protocols

PURPOSE

Exercise is thought to have a significant effect on chemotherapy, and previous studies have reported that exercise can increase patient survival. Thus, in this review, we aimed to summarize various animal models to analyze the effects of exercise on breast cancer.

METHODS

We summarized types of breast cancer animal models from various reports and analyzed the effects of exercise on anti-cancer factors in breast cancer animal models.

RESULTS

This review aimed to systematically investigate if exercise could aid in suppressing breast cancer. Our study includes (a) increase in survival rate through exercise; (b) the intensity of exercise should be consistent and increased; (c) a mechanism for inhibiting carcinogenesis through exercise; (d) effects of exercise on anti-cancer function.

CONCLUSION

This review suggested the necessity of a variety of animal models for preclinical studies prior to breast cancer clinical trials. It also provides evidence to support the view that exercise plays an important role in the prevention or treatment of breast cancer by influencing anticancer factors.

Effect of post-implant exercise on tumour growth rate, perfusion and hypoxia in mice

Preclinical studies have shown a larger inhibition of tumour growth when exercise begins prior to tumour implant (preventative setting) than when training begins after tumour implant (therapeutic setting). However, post-implantation exercise may alter the tumour microenvironment to make it more vulnerable to treatment by increasing tumour perfusion while reducing hypoxia. This has been shown most convincingly in breast and prostate cancer models to date and it is unclear whether other tumour types respond in a similar way. We aimed to determine whether tumour perfusion and hypoxia are altered with exercise in a melanoma model, and compared this with a breast cancer model. We hypothesised that post-implantation exercise would reduce tumour hypoxia and increase perfusion in these two models. Female, 6-10 week old C57BL/6 mice were inoculated with EO771 breast or B16-F10 melanoma tumour cells before randomisation to either exercise or non-exercising control. Exercising mice received a running wheel with a revolution counter. Mice were euthanised when tumours reached maximum ethical size and the tumours assessed for perfusion, hypoxia, blood vessel density and proliferation. We saw an increase in heart to body weight ratio in exercising compared with non-exercising mice (p = 0.0008), indicating that physiological changes occurred with this form of physical activity. However, exercise did not affect vascularity, perfusion, hypoxia or tumour growth rate in either tumour type. In addition, EO771 tumours had a more aggressive phenotype than B16-F10 tumours, as inferred from a higher rate of proliferation (p<0.0001), a higher level of tumour hypoxia (p = 0.0063) and a higher number of CD31+ vessels (p = 0.0005). Our results show that although a physiological training effect was seen with exercise, it did not affect tumour hypoxia, perfusion or growth rate. We suggest that exercise monotherapy is minimally effective and that future preclinical work should focus on the combination of exercise with standard cancer therapies.

Moderate Exercise Modulates Tumor Metabolism of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) stands out for its aggressiveness and accelerated rate of proliferation. Evidence shows that exercise may exert antitumorigenic effects, but the biochemical mechanisms underlying them remain unclear. Our objective was to evaluate the ability of exercise to modulate tumor growth and energy metabolism in an experimental TNBC model. Female BALB/c mice were sedentary or trained for 12 weeks and inoculated with 1 × 10⁴ 4T1 cells in the eighth week. Analyzes of macronutrient oxidation, mitochondrial respiration, and expression of genes related to cell metabolism were performed. The results showed that the trained group had a smaller tumor mass and the mitochondria in the tumors presented lower respiratory rates in the state of maximum electron transport capacity. Additionally, the tumors of the exercised group showed a higher expression of genes related to tumor suppressors, while the genes linked with cellular growth were similar between groups. Furthermore, the training modulated the corporal macronutrient oxidation to almost exclusive carbohydrate oxidation, while the sedentary condition metabolized both carbohydrate and lipids. Therefore, the exercise reduced tumor growth, with an impact on mitochondrial and macronutrient metabolism. Our results shed light on the understanding of the antitumorigenic effects of physical exercise, particularly regarding the metabolic transformations in TNBC.

Exercise reduces immune suppression and breast cancer progression in a preclinical model

Exercise is associated with favorable changes in circulating immune cells and improved survival in early-stage breast cancer patients, but the mechansims remain to be fully elucidated. Preclinical studies indicate that physical activity started before tumor injection reduces tumor incidence and progression. Here we tested whether exercise has anti-tumor effects in mice with established 4T1 mammary carcinoma, a mouse model of triple negative breast cancer. Exercise slowed tumor progression and reduced the tumor-induced accumulation of myeloid-derived suppressor cells (MDSCs). The reduction in MDSCs was accompanied by a relative increase in natural killer and CD8 T cell activation, suggesting that exercise restores a favorable immune environment. Consistently, exercise improved responses to a combination of programmed cell death protein 1 (PD-1) blockade and focal radiotherapy. These data support further investigations of exercise in breast cancer patients treated with combinations of immunotherapy and cytotoxic agents to improve cancer outcomes.

Effects of Exercise on the Tumour Microenvironment

Epidemiological evidence suggests that exercise improves survival in cancer patients. However, much is still unknown regarding the mechanisms of this positive survival effect and there are indications that exercise may not be universally beneficial for cancer patients. The key to understanding in which situations exercise is beneficial may lie in understanding its influence on the tumour microenvironment (TME)-and conversely, the influence of the tumour on physical functioning. The TME consists of a vast multitude of different cell types, mechanical and chemical stressors and humoral factors. The interplay of these different components greatly influences tumour cell characteristics and, subsequently, tumour growth rate and aggression. Exercise exerts whole-body physiological effects and can directly and indirectly affect the TME. In this chapter, we first discuss the possible role of exercise capacity ('fitness') and exercise adaptability on tumour responsiveness to exercise. We summarise how exercise affects aspects of the TME such as tumour perfusion, vascularity, hypoxia (reduced oxygenation) and immunity. Additionally, we discuss the role of myokines and other circulating factors in eliciting these changes in the TME. Finally, we highlight unanswered questions and key areas for future research in exercise oncology and the TME.

Exercise inhibits tumor growth and central carbon metabolism in patient-derived xenograft models of colorectal cancer

Background

While self-reported exercise is associated with a reduction in the risk of recurrence in colorectal cancer, the molecular mechanisms underpinning this relationship are unknown. Furthermore, the effect of exercise on intratumoral metabolic processes has not been investigated in detail in human cancers. In our current study, we generated six colorectal patient patient-derived xenografts (CRC PDXs) models and treated each PDX to voluntary wheel running (exercise) for 6–8 weeks or no exposure to the wheel (control). A comprehensive metabolomics analysis was then performed on the PDXs to identify exercise induced changes in the tumor that were associated with slower growth.

Results

Tumor growth inhibition was observed in the voluntary wheel running group compared to the control group in three of the six models. A metabolomics analysis first revealed that central carbon metabolism was affected in each model irrespective of treatment. Interestingly, comparison of responsive and resistant models showed that levels of metabolites in nucleotide metabolism, known to be coupled to mitochondrial metabolism, were predictive of response. Furthermore, phosphocreatine levels which are linked to mitochondrial energy demands were associated with inhibition of tumor growth.

Conclusion

Altogether, this study provides evidence that changes to tumor cell mitochondrial metabolism may underlie in part the benefits of exercise.

Electronic supplementary material

The online version of this article (10.1186/s40170-018-0190-7) contains supplementary material, which is available to authorized users.