Towards therapeutic exploitation of tumor addiction to fatty acids under acidosis

Cancer progression is influenced by the physico-chemical features of the tumor microenvironment. Considered as a major hallmark of cancer, tumor acidosis results from an exacerbated glycolytic metabolism and an insufficient clearance of protons by the vasculature. Hence, tumors have been described as more acidic than healthy tissues. Cancer cells will shift their metabolic preferences from glucose towards fatty acids (FAs) to adapt to this hostile environment and thereby will gain further advantages to survive, proliferate and metastasize. We examined whether promoting an excess uptake of specific FAs could lead to antitumor effects in these acidosis-adapted cancer cells. We found that n-3 but also n-6 polyunsaturated FAs (PUFAs) selectively induced ferroptosis in cancer cells under ambient acidosis. Upon exceeding the buffering capacity of lipid droplets, n-3 and n-6 PUFA peroxidation accounted for cytotoxic effects and even more so if their storage or beta-oxidation was inhibited. Finally, an n-3 PUFA-rich diet significantly delayed mouse tumor growth when compared to a control diet. The therapeutic potential of PUFA supplementation was further evaluated by studying the administration of n-3 PUFA-rich capsules to human volunteers. Altogether, our data point out dietary PUFAs as a selective adjuvant antitumor modality that may efficiently complement pharmacological approaches.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 202

Dealing with saturated and unsaturated fatty acid metabolism for anticancer therapy.

Although saturated fatty acid (FA) (SFA) and monounsaturated FA (MUFA) are synthesized in cancer cells from acetyl-CoA, polyunsaturated FAs (PUFAs) are necessarily obtained from diet. Depending on concentrations and metabolism, these different FAs may support tumor proliferation but also exert growth inhibitory effects. The mutual interplay between them also requires to integrate the FA oxidation component that may be concomitant with FA synthesis is cancer cells. New molecular mechanisms driving FA synthesis, lipotoxicity and anti-inflammatory activity of eicosanoids in mouse and human cancers were recently elicited. To block or take advantage of the above represent attractive perspectives of treatments to fight cancer progression. The various enzymatic reactions leading to SFA synthesis represent as many targets to prevent tumor growth. Ironically excess SFAs are per-se toxic for cancer cells and the introduction of a double bound to form MUFA is actually limiting lipotoxicity in cancer cells. Blocking stearoyl-CoA desaturase therefore represents another attractive modality. By contrast, dietary PUFAs may exert direct cytotoxic effects by promoting apoptosis or by generating anti-inflammatory eicosanoids. Altogether, these data point out the intricate relationship between SFA, MUFA and PUFA at the heart of the metabolism of proliferating cancer cells

Therapeutic exploitation of tumor addiction to fatty acids under acidosis

Acidosis is considered as a hallmark of the tumor microenvironment. Indeed, extracellular pH has been determined in a wide variety of cancers to be significantly more acidic than in normal tissues. Recently, we identified an acidosis-driven metabolic shift from a largely glycolytic metabolism towards significant alterations in fatty acid (FA) metabolism allowing the concomitance of FA oxidation and glutamine-fueled FA synthesis. In this study, we aim to take advantage of this lipid addiction of acidosis-adapted cancer cells to evaluate the possibility to force these cells to take up potentially cytotoxic FA. Growth inhibitory effects were observed with omega-6 (n-6) and omega-3 (n-3) polyunsaturated FA (PUFA) in proportion to the number of unsaturations for both PUFA. More precisely, while short-chain PUFA had only minor effects on cancer cell growth, long-chain PUFA, such as docosapentaenoic acid (DPA n-6) and docosahexaenoic acid (DHA n-3) induced specific cytotoxic effects on acidosis-adapted cells but not on parental cells (at pH 7.4). Furthermore, we found that PUFA are less (rapidly) metabolized than corresponding saturated FA and block respiration fueled by saturated FA in acidosis-adapted cancer cells. Finally, we showed that 3D tumor spheroid growth was severely impaired upon treatment with DPA n-6 and DHA n-3. This growth inhibitory effect was observed only after 4 to 7 days of PUFA administration, which corresponds to the timing for acidosis development. The above effects suggest that PUFA administration could represent a modality to block tumor growth and disease progression in vivo

Cancer diets for cancer patients: Lessons from mouse studies and new insights from the study of fatty acid metabolism in tumors

Specific diets for cancer patients have the potential to offer an adjuvant modality to conventional anticancer therapy. If the concept of starving cancer cells from nutrients to inhibit tumor growth is quite simple, the translation into the clinics is not straightforward. Several diets have been described including the Calorie-restricted diet based on a reduction in carbohydrate intake and the Ketogenic diet wherein the low carbohydrate content is compensated by a high fat intake. As for other diets that deviate from normal composition only by one or two amino acids, these diets most often revealed a reduction in tumor growth in mice, in particular when associated with chemo- or radiotherapy. By contrast, in cancer patients, the interest of these diets is almost exclusively supported by case reports precluding any conclusions on their real capacity to influence disease outcome. In parallel, the field of tumor lipid metabolism has emerged in the last decade offering a better understanding of how fatty acids are captured, synthesized or stored as lipid droplets in cancers. Fatty acids participate to cancer cell survival in the hypoxic and acidic tumor microenvironment and also support proliferation and invasiveness. Interestingly, while such addiction for fatty acids may account for cancer progression associated with high fat diet, it could also represent an Achilles heel for tumors. In particular n-3 polyunsaturated fatty acids represent a class of lipids that can exert potent cytotoxic effects in tumors and therefore represent an attractive diet supplementation to improve cancer patient outcomes

Targeting cancer cells in acidosis with conjugates between the carnitine palmitoyltransferase 1 inhibitor etomoxir and pH (low) insertion peptides

Targeting enzymes involved in tumor metabolism is a promising way to tackle cancer progression. The inhibition of carnitine palmitoyltransferase 1 (CPT1) by etomoxir (Eto) efficiently slows down the growth of various cancers. Unfortunately, the clinical use of this drug was abandoned because of hepatotoxic effects. We report the development of pH-sensitive peptide (pHLIP)-drug conjugate to deliver Eto selectively to cancer cells exposed to acidic microenvironmental conditions. A newly designed sequence for the pHLIP peptide, named pHLIPd, was compared with a previously published reference pHLIP peptide, named pHLIPr. We showed that the conjugate between pHLIPd and Eto has a better pH-dependent insertion and structuration than the pHLIPr-based conjugate inside POPC vesicles. We observed antiproliferative effects when applied on acid-adapted cancer cells, reaching a larger inhibitory activity than Eto alone. In conclusion, this study brings the first evidence that pHLIP-based conjugates with a CPT1 inhibitor has the potential to specifically target the tumor acidic compartment and exert anticancer effects while sparing healthy tissues

Punicic Acid Triggers Ferroptotic Cell Death in Carcinoma Cells

Plant-derived conjugated linolenic acids (CLnA) have been widely studied for their preventive and therapeutic properties against diverse diseases such as cancer. In particular, punicic acid (PunA), a conjugated linolenic acid isomer (C18:3 c9t11c13) present at up to 83% in pomegranate seed oil, has been shown to exert anti-cancer effects, although the mechanism behind its cytotoxicity remains unclear. Ferroptosis, a cell death triggered by an overwhelming accumulation of lipid peroxides, has recently arisen as a potential mechanism underlying CLnA cytotoxicity. In the present study, we show that PunA is highly cytotoxic to HCT-116 colorectal and FaDu hypopharyngeal carcinoma cells grown either in monolayers or as three-dimensional spheroids. Moreover, our data indicate that PunA triggers ferroptosis in carcinoma cells. It induces significant lipid peroxidation and its effects are prevented by the addition of ferroptosis inhibitors. A combination with docosahexaenoic acid (DHA), a known polyunsaturated fatty acid with anticancer properties, synergistically increases PunA cytotoxicity. Our findings highlight the potential of using PunA as a ferroptosis-sensitizing phytochemical for the prevention and treatment of cancer

Peroxidation of n-3 and n-6 polyunsaturated fatty acids in the acidic tumor environment leads to ferroptosis-mediated anticancer effects

Tumor acidosis promotes disease progression through a stimulation of fatty acid (FA) metabolism in cancer cells. Instead of blocking the use of FAs by acidic cancer cells, we examined whether excess uptake of specific FAs could lead to antitumor effects. We found that n-3 but also remarkably n-6 polyunsaturated FA (PUFA) selectively induced ferroptosis in cancer cells under ambient acidosis. Upon exceeding buffering capacity of triglyceride storage into lipid droplets, n-3 and n-6 PUFA peroxidation led to cytotoxic effects in proportion to the number of double bonds and even more so in the presence of diacylglycerol acyltransferase inhibitors (DGATi). Finally, an n-3 long-chain PUFA-rich diet significantly delayed mouse tumor growth when compared with a monounsaturated FA-rich diet, an effect further accentuated by administration of DGATi or ferroptosis inducers. These data point out dietary PUFA as a selective adjuvant antitumor modality that may efficiently complement pharmacological approaches

Creation of snacks enriched with polyunsaturated fatty acids and benefits for metabolic parameters: a double-blind randomised controlled trial in overweight subjects

Background: There is a considerable increase in metabolic disorders in the world population, such as obesity, type 2 diabetes, cardiovascular disease and steatotic liver disease associated with metabolic dysfunction (SAMLD). There is growing interest in understanding dietary lipid metabolism and improving food quality for human well-being and disease prevention. In particular, certain polyunsaturated fatty acids (PUFAs) such as alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), rumenic acid (RmA) and punicic acid (PunA) are known to have positive biological activities on human health and have attracted the interest of many scientists. The supply of healthy foods is also a priority. Aims. The aims are to study the feasibility of incorporating eggs naturally enriched with ALA, DHA, RmA and PunA into crackers, and to test their tolerance and their effects on metabolic parameters and body composition in humans fed with these test crackers compared with control crackers (Omegasnack study). Methodology: A double-blind randomized controlled trial was conducted on 25 overweight subjects with abdominal adiposity. Hens were fed with pomegranate oil and flax seeds to obtain eggs naturally enriched in ALA, DHA, RmA, PunA, which were used in the test crackers and hens were fed with olive oil to obtain eggs naturally enriched in oleic acid, which were used in control crackers. Human subjects were randomly assigned into two groups: a control group consuming control crackers and a test group receiving test crackers. Each group consumed a serving of the respective crackers (67.5 grams) as an afternoon snack every day for 70 days. Clinical, anthropometric and biological data were evaluated. Body composition was assessed by bioimpedance analysis and abdominal CT scan. Liver status was assessed by non-invasive scores and transient elastography. Results: Fatty acids of interest were efficiently incorporated into test crackers made with eggs from hens fed modified diets. The test crackers were significantly enriched with PUFAs n-3 such as DHA and conjugated fatty acids such as PunA and RmA, providing a daily intake of 141, 662 and 1119 mg, respectively (p<0.05 versus control crackers). The characteristics of the subjects were as follows with no difference between the two groups: mean age of 45.9 years, mean BMI of 28.1 kg/m², mean waist circumference of 99.1 cm, median hepatic elasticity of 4.6 kPa, mean controlled attenuation parameter of 258 dB/m. Insulin resistance was noted, with a mean HOMA-IR of 2.9. The mean triglyceride level was 105.3 mg/dL and the mean fatty liver index 48.5. The median visceral fat area was 114.3 cm². The median sekeletal muscle index was 48.6 cm²/m². The estimated compliance was 95% in both groups. Test and control crackers were well tolerated and increased satiety while reducing hunger and intention to eat in the future, but no impact on weight or waist circumference was noted. There was no change in circulating cholesterol or triglyceride levels. Liver transaminases and GGT remained stable during the study for both control and test group. Glucose metabolism and insulin resistance parameters were measured in the fasted state and did not appear to be strongly affected by either type of crackers. There was no difference in body composition (liver fat, adiposity, muscle surface or density) between the two groups. A significant transient decrease in HOMA-IR was detected with the test crackers during the study (HOMA-IR 2.77 ± 1.26 vs. baseline 3.15 ± 1.27, p< 0.05). The fatty acid composition of plasma and red blood cells was modified by the type of cracker consumed. In the test group, RmA and PunA significantly increased in plasma (12.9 ± 8.8 vs. 4.7 ± 2.6 mg/L and 4.4 ± 2.4 vs ND, p < 0.05) and RmA was efficiently incorporated into human red blood cells (0.33 ± 0.08 vs. 0.09 ± 0.03 weight % of total identified fatty acids, p<0.05). Conclusion: PUFAs can be successfully incorporated into snacks without adverse effects. The study demonstrates their potential long-term benefits by effectively incorporating them into plasma and red blood cells. These findings argue in favor of studying the inclusion of PUFAs in snack products to promote health through long-term trials in specific groups of patients

Création de crackers enrichis en acides gras polyinsaturés avec des bénéfices pour les paramètres métaboliques : un essai contrôlé randomisé en double aveugle chez des sujets en surpoids

Introduction : Les acides gras polyinsaturés (AGPI) tels que l'acide alpha-linolénique (ALA), l'acide docosahexaénoïque (DHA), l'acide ruménique (RmA) et l'acide punicique (PunA) sont considérés comme ayant des effets bénéfiques dans la prévention et le traitement de plusieurs problèmes métaboliques. Dans cette optique, des œufs naturellement enrichis en ALA, DHA, RmA et PunA ont été incorporés dans des crackers tests afin de proposer un en-cas sain riche en acides gras spécifiques. Les objectifs sont d'étudier la faisabilité de l'incorporation de ces acides gras dans les crackers, et d'évaluer les bénéfices métaboliques de la consommation de ces crackers par rapport à des contrôles. Méthodes : Un essai contrôlé randomisé en double aveugle a été mené sur 25 sujets en surpoids présentant une adiposité abdominale, répartis au hasard en deux groupes : un groupe témoin consommant des crackers contrôles fabriqués à partir d'œufs enrichis en acide oléique et un groupe test recevant des crackers test. Cet en-cas (+/- 67,5 grammes) a été administrée comme collation quotidienne de l'après-midi, pendant 70 jours (étude omegasnack, NCT05413954). Résultats : Les AGPI intéressants ont été efficacement incorporés dans les crackers fabriqués avec des œufs de poules nourries avec des régimes alimentaires modifiés. Les crackers tests et les crackers contrôles ont été bien tolérés et ont augmenté la satiété. Aucune différence entre les deux groupes n’a été notée en ce qui concerne le tour de taille, la composition corporelle (stéatose hépatique, adiposité viscérale, surface musculaire, myostéatose) ou le niveau de résistance à l'insuline. Les taux de cholestérol et de triglycérides circulants n'ont pas été modifiés. La composition en acides gras du plasma et des globules rouges a été modifiée par le type de crackers consommés. Dans le groupe test, les RmA et PunA ont augmenté de manière significative dans le plasma et l’RmA a été efficacement incorporé dans les globules rouges. Conclusion : Les AGPI peuvent être incorporés avec succès dans des snacks sans effets indésirables. L'étude démontre leurs avantages potentiels à long terme en les incorporant efficacement dans le plasma et les globules rouges. Ces résultats plaident en faveur de l'étude de l'inclusion des AGPI dans des en-cas sains