Exercise-Mediated Lowering of Glutamine Availability Suppresses Tumor Growth and Attenuates Muscle Wasting

Non-pharmaceutical interventions to optimize cancer immunotherapy

The traditional picture of cancer patients as weak individuals requiring maximum rest and protection is beginning to dissolve. Too much focus on the medical side and one's own vulnerability and mortality might be counterproductive and not doing justice to the complexity of human nature. Unlike cytotoxic and lympho-depleting treatments, immune-engaging therapies strengthen the immune system and are typically less harmful for patients. Thus, cancer patients receiving checkpoint inhibitors are not viewed as being vulnerable per se, at least not in immunological and physical terms. This perspective article advocates a holistic approach to cancer immunotherapy, with an empowered patient in the center, focusing on personal resources and receiving domain-specific support from healthcare professionals. It summarizes recent evidence on non-pharmaceutical interventions to enhance the efficacy of immune checkpoint blockade and improve quality of life. These interventions target behavioral factors such as diet, physical activity, stress management, circadian timing of checkpoint inhibitor infusion, and waiving unnecessary co-medication curtailing immunotherapy efficacy. Non-pharmaceutical interventions are universally accessible, broadly applicable, instantly actionable, scalable, and economically sustainable, creating value for all stakeholders involved. Most importantly, this holistic framework re-emphasizes the patient as a whole and harnesses the full potential of anticancer immunity and checkpoint blockade, potentially leading to survival benefits. Digital therapeutics are proposed to accompany the patients on their mission toward change in lifestyle-related behaviors for creating optimal conditions for treatment efficacy and personal growth.

Voluntary exercise does not always suppress lung cancer progression

Physical exercise can lower lung cancer incidence. However, its effect on lung cancer progression is less understood. Studies on exercising mice have shown decreased ectopic lung cancer growth through the secretion of interleukin-6 from muscles and the recruitment of natural killer (NK) cells to tumors. We asked if exercise suppresses lung cancer in an orthotopic model also. Single-housed C57Bl/6 male mice in cages with running wheels were tail vein-injected with LLC1.1 lung cancer cells, and lung tumor nodules were analyzed. Exercise did not affect lung cancer. Therefore, we also tested the effect of exercise on a subcutaneous LLC1 tumor and a tail vein-injected B16F10 melanoma model. Except for one case of excessive exercise, tumor progression was not influenced. Moderately exercising mice did not increase IL-6 or recruit NK cells to the tumor. Our data suggest that the exercise dose may dictate how efficiently the immune system is stimulated and controls tumor progression.

SLC38A6, regulated by EP300-mediated modifications of H3K27ac, promotes cell proliferation, glutamine metabolism and mitochondrial respiration in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common form of liver cancer. The incidence of HCC is increasing and effective prevention methods are needed. The solute carrier family 38 member 6 (SLC38A6) plays an important role in the metabolism of glutamine, which is a central nutrient for many cancers. However, the regulation and function of SLC38A6 in HCC are unclear. SLC38A6 levels in human HCC tissue arrays and cells were determined. SLC38A6 was silenced or overexpressed to determine its role in regulating cell viability, colony formation, cell cycle progression, glutamine metabolism and mitochondrial respiration. A luminescence assay was used to study the interaction between SLC38A6 and EP300. The interactions between SLC38A6, H3K27ac and EP300 were determined using chromatin immunoprecipitation assays. Quantitative RT-PCR and immunoblots were performed to measure mRNAs and proteins, respectively. SLC38A6 expression was higher in HCC compared with expression in normal tissue. Silencing SLC38A6 inhibited cell viability, colony formation, cell cycle progression, glutamine metabolism and mitochondrial respiration, while SLC38A6 overexpression had the opposite effects. Silencing SLC38A6 also inhibited tumor growth in vivo. Silencing EP300 significantly suppressed the interaction between H3K27ac and the SLC38A6 promoter, leading to decreased SLC38A6. SLC38A6 is regulated by EP300-mediated modifications of H3K27ac and promotes viability, colony formation, cell cycle progression, glutamine metabolism and mitochondrial respiration in HCC cells.

Exercise suppresses tumor growth independent of high fat food intake and associated immune dysfunction

Epidemiological data suggest that exercise training protects from cancer independent of BMI. Here, we aimed to elucidate mechanisms involved in voluntary wheel running-dependent control of tumor growth across chow and high-fat diets. Access to running wheels decreased tumor growth in B16F10 tumor-bearing on chow (− 50%) or high-fat diets (− 75%, p < 0.001), however, tumor growth was augmented in high-fat fed mice (+ 53%, p < 0.001). Tumor growth correlated with serum glucose (p < 0.01), leptin (p < 0.01), and ghrelin levels (p < 0.01), but not with serum insulin levels. Voluntary wheel running increased immune recognition of tumors as determined by microarray analysis and gene expression analysis of markers of macrophages, NK and T cells, but the induction of markers of macrophages and NK cells was attenuated with high-fat feeding. Moreover, we found that the regulator of innate immunity, ZBP1, was induced by wheel running, attenuated by high-fat feeding and associated with innate immune recognition in the B16F10 tumors. We observed no effects of ZBP1 on cell cycle arrest, or exercise-regulated necrosis in the tumors of running mice. Taken together, our data support epidemiological findings showing that exercise suppresses tumor growth independent of BMI, however, our data suggest that high-fat feeding attenuates exercise-mediated immune recognition of tumors.

A Bout of High-Intensity Interval Training (HIIT) in Children and Adolescents during Acute Cancer Treatment-A Pilot Feasibility Study

Low- and moderate-intensity exercise is safe and feasible during childhood cancer treatment. The feasibility of a bout of high-intensity interval training (HIIT) in this population has not been analyzed to date. Pediatric cancer patients aged between 6 and 18 years were selected based on clinical conditions to perform ten sets of 15 s HIIT (>90% of estimated maximal heart rate (HRmax)) and 1 min active recovery on a bicycle ergometer within the first three chemotherapy courses. We assessed safety and feasibility criteria and the following parameters: perceived exertion rate, heart rate, and lactate and adrenaline concentrations. Out of 212 eligible patients, 11 patients aged 13.9 ± 3.6 years (n = 7 ♂) with lymphoma, leukemia, rhabdomyosarcoma, nephroblastoma, and synovial sarcoma completed the bout of HIIT without serious adverse events. During exercise, patients reached a BORG value maxima of 16 ± 1.2, and their heart rates rose from 78 ± 17 beats per minute (bpm) at rest to 178 ± 12 bpm after exercise (90 ± 6% estimated HRmax). The power-to-weight ratio was 2 ± 0.5 W/kg (watt per kilogram). Blood lactate concentrations increased from 1.09 ± 0.50 mmol/L (millimole per liter) at rest to 5.05 ± 1.88 mmol/L post-exercise. Our preliminary data suggest that HIIT is applicable only in a small number of childhood cancer patients. Individually adapted exercise protocols for patients with multiple impairments are needed.

Therapeutic Potential of Glutamine Pathway in Lung Cancer

Cancer cells tend to obtain the substances needed for their development depending on altering metabolic characteristics. Among the reorganized metabolic pathways, Glutamine pathway, reprogrammed to be involved in the physiological process including energy supply, biosynthesis and redox homeostasis, occupies an irreplaceable role in tumor cells and has become a hot topic in recent years. Lung cancer currently maintains a high morbidity and mortality rate among all types of tumors and has been a health challenge that researchers have longed to overcome. Therefore, this study aimed to clarify the essential role of glutamine pathway played in the metabolism of lung cancer and its potential therapeutic value in the interventions of lung cancer.

AMP deamination is sufficient to replicate an atrophy-like metabolic phenotype in skeletal muscle

BACKGROUND

Skeletal muscle atrophy, whether caused by chronic disease, acute critical illness, disuse or aging, is characterized by tissue-specific decrease in oxidative capacity and broad alterations in metabolism that contribute to functional decline. However, the underlying mechanisms responsible for these metabolic changes are largely unknown. One of the most highly upregulated genes in atrophic muscle is AMP deaminase 3 (AMPD3: AMP → IMP + NH3), which controls the content of intracellular adenine nucleotides (AdN; ATP + ADP + AMP). Given the central role of AdN in signaling mitochondrial gene expression and directly regulating metabolism, we hypothesized that overexpressing AMPD3 in muscle cells would be sufficient to alter their metabolic phenotype similar to that of atrophic muscle.

METHODS

AMPD3 and GFP (control) were overexpressed in mouse tibialis anterior (TA) muscles via plasmid electroporation and in C2C12 myotubes using adenovirus vectors. TA muscles were excised one week later, and AdN were quantified by UPLC. In myotubes, targeted measures of AdN, AMPK/PGC-1α/mitochondrial protein synthesis rates, unbiased metabolomics, and transcriptomics by RNA sequencing were measured after 24 h of AMPD3 overexpression. Media metabolites were measured as an indicator of net metabolic flux. At 48 h, the AMPK/PGC-1α/mitochondrial protein synthesis rates, and myotube respiratory function/capacity were measured.

RESULTS

TA muscles overexpressing AMPD3 had significantly less ATP than contralateral controls (-25%). In myotubes, increasing AMPD3 expression for 24 h was sufficient to significantly decrease ATP concentrations (-16%), increase IMP, and increase efflux of IMP catabolites into the culture media, without decreasing the ATP/ADP or ATP/AMP ratios. When myotubes were treated with dinitrophenol (mitochondrial uncoupler), AMPD3 overexpression blunted decreases in ATP/ADP and ATP/AMP ratios but exacerbated AdN degradation. As such, pAMPK/AMPK, pACC/ACC, and phosphorylation of AMPK substrates, were unchanged by AMPD3 at this timepoint. AMPD3 significantly altered 191 out of 639 detected intracellular metabolites, but only 30 transcripts, none of which encoded metabolic enzymes. The most altered metabolites were those within purine nucleotide, BCAA, glycolysis, and ceramide metabolic pathways. After 48 h, AMPD3 overexpression significantly reduced pAMPK/AMPK (-24%), phosphorylation of AMPK substrates (-14%), and PGC-1α protein (-22%). Moreover, AMPD3 significantly reduced myotube mitochondrial protein synthesis rates (-55%), basal ATP synthase-dependent (-13%), and maximal uncoupled oxygen consumption (-15%).

CONCLUSIONS

Increased expression of AMPD3 significantly decreased mitochondrial protein synthesis rates and broadly altered cellular metabolites in a manner similar to that of atrophic muscle. Importantly, the changes in metabolites occurred prior to reductions in AMPK signaling, gene expression, and mitochondrial protein synthesis, suggesting metabolism is not dependent on reductions in oxidative capacity, but may be consequence of increased AMP deamination. Therefore, AMP deamination in skeletal muscle may be a mechanism that alters the metabolic phenotype of skeletal muscle during atrophy and could be a target to improve muscle function during muscle wasting.

Voluntary wheel running can lead to modulation of immune checkpoint molecule expression

BACKGROUND

Exercise and physical activity (PA) are associated with reduced tumor growth and enhanced intra-tumoral immune cell infiltration in mice. We aimed to investigate the role of PA achieved by voluntary wheel running in promoting the immunogenic profile across several murine tumor models, and to explore the potential of checkpoint blockade and PA in the form of voluntary wheel running as combination therapy.

MATERIAL AND METHODS

The experiments were performed with C57BL/6 mice bearing subcutaneous tumors while having access to running wheels in their cages, where key immunoregulatory molecules expressed in the tumor tissue were measured by qPCR. Furthermore, we tested the hypothesis that wheel running combined with PD-L1 -or PD-1 inhibitor treatment could lead to an additive effect on tumor growth in mice bearing B16 melanoma tumors.

RESULTS

Wheel running increased immune checkpoint expression (PD-1, PD-L1, PD-L2, CD28, B7.1 and B7.2) in B16 tumor-bearing mice, while induction of only PD-L2 was found in E0771 breast cancer and Lewis Lung Cancer. In studies combining voluntary wheel running with PD-1 -and PD-L1 inhibitors we found significant effects of wheel running on attenuating B16 melanoma tumor growth, in line with previous studies. We did, however, not find an additive effect of combining either of the two immunotherapeutic treatments with access to running wheels.

CONCLUSION

B16 tumors displayed upregulated expression of immune regulatory molecules and decreased tumor growth in response to PA. However, combining PA with PD-1 or PD-L1 blockade did not lead to a further augmented inhibition of tumor growth.