BackgroundLung cancer is the second common cancer type in western countries and has a high mortality. During the development and progression of the tumor, the nutrients in its environment play a central role. The tumor cells depend crucially on glucose metabolism and uptake. Tumor cell metabolism is dominated by the Warburg effect, where tumor cells produce large amounts of lactate from pyruvate under aerobic conditions. We thus reasoned that, reducing carbohydrates in the diet might support anti-tumoral effects of current immunotherapy and additionally target tumor immune escape.ObjectivesThe link between reducing carbohydrates to improve current immunotherapy is not clear. We thus aimed at analyzing the effects of different glucose levels on the tumor development, progression and the anti-tumoral immune response.MethodsWe correlated the clinical parameters of our LUAD cohort with different metabolic markers. Additionally, we performed cell culture experiments with A549 tumor cell line under different glucose levels. Lastly, we investigated the effect of low and high carbohydrate diet in an experimental murine model of lung cancer on the tumor progression and different immune subsets.ResultsHere we found a positive correlation between the body mass index (BMI), blood glucose levels, reduced overall survival (OS) and the expression of Insulin-like growth factor-1 receptor (IGF1R) in the lung tumoral region of patients with lung adenocarcinoma (LUAD). Furthermore, increasing extracellular glucose induced IGF1R expression in A549 LUAD cells. Functional studies in a murine model of LUAD demonstrated that, glucose restricted diet resulted in decreased tumor load in vivo. This finding was associated with increased presence of lung infiltrating cytotoxic CD8+ T effector memory (TEM), tissue resident memory T (TRM) and natural killer cells as well as reduced IGFR mRNA expression, suggesting that glucose restriction regulates lung immunity in the tumor microenvironment.ConclusionsThese results indicate that, glucose restricted diet improves lung immune responses of the host and suppresses tumor growth in experimental lung adenocarcinoma. As glucose levels in LUAD patients were negatively correlated to postoperative survival rates, glucose-restricted diet emerges as therapeutic avenue for patients with LUAD.

Neoplasms of the lungs are the leading cause of cancer incidence and mortality worldwide. Although immunotherapy has increased the overall survival of patients with lung cancer, there is the need to improve this treatment. At this regard, blood lipid levels are thought to be linked to cancer risk and thus a preventive intervention through regulation of the nutrition of patients with lung cancer is gaining much attention. In this study, we therefore asked about the contribution of serum lipids and cholesterol cellular metabolism in lung cancer development and progression. We measured different serum lipids and analyzed cholesterol synthesis enzymes 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR) and acetyl-coenzyme A cholesterol acetyltransferase 1 (ACAT1) as well as the cholesterol cellular export protein ATP-binding cassette (ABC) A-1 mRNA by quantitative PCR (qPCR) in the control and tumoral regions of post-surgery lung tissues to analyze the accumulation of cholesterol in cancer cells in a cohort of patients with lung adenocarcinoma (LUAD). We found that triglycerides in serum directly correlated with the body mass index (BMI) in patients with LUAD. By contrast, we found that high-density lipoprotein (HDL) cholesterol inversely correlated with the BMI, C-reactive protein (CRP) and overall survival and total cholesterol inversely correlated with the tumor diameter, serum CRP and overall survival in these LUAD patients. Functionally, the role of cholesterol is indispensable for the growth and development of normal animal cells where it is tightly regulated. Excess of cellular cholesterol regulated by HMGCR is converted to cholesteryl esters by the enzyme ACAT1 and exported extracellularly by the cholesterol transporter ABCA1. Here we found HMGCR and ACAT1 upregulated and ABCA1 downregulated in the lung’s tumoral region of our LUAD cohort, indicating cholesterol dysregulated cellular export in lung tumor cells.

Lung cancer is one of the most common cancer types in the western world, with a high lethality and increasing incidence. One major factor, supporting tumor growth is a high sugar diet. Thus, reducing the sugar intake by different diets might be a way to improve current cancer treatment. These metabolic changes are accompanied by regulation of systemic levels of Insulin and insulin like growth factors. As oppose to normal cells, tumor cells metabolism mainly depends on glycolysis. Thus, reducing diet carbohydrate intake might be a way to improve current immunotherapy by inducing immunological changes caused by the extracellular glucose concentration in tumor microenvironment. Therefore, we cultured the human lung adenocarcinoma (ADC) cell line A549 with different extracellular glucose concentrations to analyze effects by flow cytometry and qPCR. Moreover, lung tissue samples from patients with non small cell lung cancer (NSCLC), were analyzed by qPCR. In a murine model of lung ADC, tumor cells were injected intravenously and mice were fed with different diets. Lung cells were isolated and analyzed by flow cytometry. Here we show that, IGF1R expression is upregulated in A549 cells line, depending on increasing extracellular glucose concentration. Moreover, in studies on human cohorts of patients with NSCLC, we found a direct correlation between BMI and IGF1R expression and its downstream signaling. Finally, in a murine model of disease, diet glucose restriction decreased significantly tumor load associated with increased lung infiltrating CD8+ T-cells and tissue-resident memory T-cells. Thus, this study supports the need to introduce glucose restrictions in the diet of patients with NSCLC in association with current immunotherapy.