Dietary fat without body weight gain increases in vivo MCF‐7 human breast cancer cell growth and decreases natural killer cell cytotoxicity

Targeting lipid metabolism in cancer metastasis

This review delves into the most recent research on the metabolic adaptability of cancer cells and examines how their metabolic functions can impact their progression into metastatic forms. We emphasize the growing significance of lipid metabolism and dietary lipids within the tumor microenvironment, underscoring their influence on tumor progression. Additionally, we present an outline of the interplay between metabolic processes and the epigenome of cancer cells, underscoring the importance regarding the metastatic process. Lastly, we examine the potential of targeting metabolism as a therapeutic approach in combating cancer progression, shedding light on innovative drugs/targets currently undergoing preclinical evaluation.

Targeting adipocyte-immune cell crosstalk to control breast cancer progression

Adipocytes are crucial components of breast cancer and are involved in regulating the progression, therapeutic efficacy, and prognosis of breast cancer patients. Characterized by storing energy and producing a variety of secretory factors, adipocytes are responsible for inducing obesity and regulating the tumor immune activity. Adipocytes communicate with tumor infiltrating immune cells through the secreted adipokines, cytokines, and exosomes in the breast cancer TIME, which shapes the tumor supporting environment to facilitate the immune escape of tumor cells. In-depth studies of the crosstalk between adipocytes and TIME can not only provide a more comprehensive regulatory landscape of TIME, but also be conducive to screening novel targets for future precision targeted therapy. The aim of this review is to discuss recent studies for understanding the role of crosstalk between adipocytes and immune cells in shaping the breast cancer immune microenvironment.

The role of lipids in cancer progression and metastasis

Lipids have essential biological functions in the body (e.g., providing energy storage, acting as a signaling molecule, and being a structural component of membranes); however, an excess of lipids can promote tumorigenesis, colonization, and metastatic capacity of tumor cells. To metastasize, a tumor cell goes through different stages that require lipid-related metabolic and structural adaptations. These adaptations include altering the lipid membrane composition for invading other niches and overcoming cell death mechanisms and promoting lipid catabolism and anabolism for energy and oxidative stress protective purposes. Cancer cells also harness lipid metabolism to modulate the activity of stromal and immune cells to their advantage and to resist therapy and promote relapse. All this is especially worrying given the high fat intake in Western diets. Thus, metabolic interventions aiming to reduce lipid availability to cancer cells or to exacerbate their metabolic vulnerabilities provide promising therapeutic opportunities to prevent cancer progression and treat metastasis.

Obesity, Inflammation, and Immune System in Osteoarthritis

Obesity remains the most important risk factor for the incidence and progression of osteoarthritis (OA). The leading cause of OA was believed to be overloading the joints due to excess weight which in turn leads to the destruction of articular cartilage. However, recent studies have proved otherwise, various other factors like adipose deposition, insulin resistance, and especially the improper coordination of innate and adaptive immune responses may lead to the initiation and progression of obesity-associated OA. It is becoming increasingly evident that multiple inflammatory cells are recruited into the synovial joint that serves an important role in pathological changes in the synovial joint. Polarization of macrophages and macrophage-produced mediators are extensively studied and linked to the inflammatory and destructive responses in the OA synovium and cartilage. However, the role of other major innate immune cells such as neutrophils, eosinophils, and dendritic cells in the pathogenesis of OA has not been fully evaluated. Although cells of the adaptive immune system contribute to the pathogenesis of obesity-induced OA is still under exploration, a quantity of literature indicates OA synovium has an enriched population of T cells and B cells compared with healthy control. The interplay between a variety of immune cells and other cells that reside in the articular joints may constitute a vicious cycle, leading to pathological changes of the articular joint in obese individuals. This review addresses obesity and the role of all the immune cells that are involved in OA and summarised animal studies and human trials and knowledge gaps between the studies have been highlighted. The review also touches base on the interventions currently in clinical trials, different stages of the testing, and their shortcomings are also discussed to understand the future direction which could help in understanding the multifactorial aspects of OA where inflammation has a significant function.

Natural killer cell therapy: A new frontier for obesity-associated cancer

Natural killer (NK) cell infiltration of solid tumours is associated with better outcomes, placing augmentation of NK cell abundance in tumours as an attractive immunotherapeutic approach. The unique ability of NK cells to target cancer cells without antigen specificity increases their versatility and applicability as an immunotherapeutic tool. However, successful utilisation of NK cell-based therapies in solid tumours is still at an early stage. Obesity has become a global health epidemic, and the prevalence of obesity-associated cancers has significantly increased. Obesity-associated malignancies provide a unique challenge for the successful application of cell-based immunotherapies including NK cell-based therapies because significant numbers of NK and T cells are recruited to the visceral adipose tissue at the expense of successful tumour infiltration and eradication. As such, immunotherapy efficacy has been disappointing for obesity-associated malignancies such as oesophageal and gastric adenocarcinoma. Therefore, immunotherapies for obesity-associated cancers warrant our further attention. Indeed, it is becoming ever more obvious that more innovative approaches are needed to re-invigorate anti-tumour immunity and overcome immune exclusion in such tumours. In this review, we briefly summarise the dysfunctionality of NK cells in obesity-associated cancer. We outline the NK cell-based immunotherapeutic approaches which hold promise as effective treatments in this disease space, including CAR-NK cells. Furthermore, we suggest future avenues which possess the potential to transform immunotherapy and specifically NK cell therapy efficacy for obesity-associated cancer.

The relationship between dairy products intake and breast cancer incidence: a meta-analysis of observational studies

BACKGROUND

The effect of dairy products intake on breast cancer (BC) is highly controversial. This study aims to investigate the relationship between dairy intake and BC incidence.

METHODS

A search was carried out in PubMed, EBSCO, Web of Science, and Cochrane Library databases before January 2021. The primary objective was the risk of BC and intake of dairy products were exposure variables.

RESULTS

The meta-analysis comprised 36 articles with 1,019,232 participants. Total dairy products have a protective effect on female population (hazard ratio (HR) =0.95, 95% confidence interval (CI) =0.91-0.99, p = 0.019), especially for estrogen receptor-positive (ER+) (HR = 0.79, p = 0.002) and progesterone receptor-positive (PR+) BC (HR = 0.75, p = 0.027). For ER+/PR+ BC, there is a trend of protection, but it has not reached statistical significance (HR = 0.92, p = 0.075). Fermented dairy products can reduce BC risk in postmenopausal population (HR = 0.96, 95%CI = 0.93-0.99, p = 0.021), but have no protective effect on premenopausal population (HR = 0.98, 95%CI = 0.94-1.03, p = 0.52). Non-fermented dairy products have no significant effect on BC occurrence (p > 0.05). High-fat dairy products are harmful to women, without statistical difference (HR = 1.06, 95%CI = 1.00-1.13, p = 0.066). On the contrary, low-fat dairy products can protect the premenopausal population (HR = 0.94, 95%CI = 0.89-1.00, p = 0.048).

CONCLUSION

The intake of dairy products can overall reduce BC risk in the female population, but different dairy products have varying effects on different BC subtypes and menopausal status.

Natural Killer Cell Dysfunction in Obese Patients with Breast Cancer: A Review of a Triad and Its Implications

Natural killer cells (NK cells) are a crucial constituent of the innate immune system as they mediate immunity against viruses, bacteria, parasites, and most importantly, tumor cells. The exact mechanism of how the innate immune system and specifically NK cells interact with cancer cells is complex and is yet to be understood. Several factors that constitute the tumor microenvironment (TME) such as hypoxia and TGF-β are believed to play a role in the complex physiological reaction of NK cells to tumor cells. On the other hand, several risk factors are implicated in the development and progression of breast cancer, most importantly: obesity. Cytokines released from adipose tissue such as adipokines, leptin, and resistin, among others, are also believed to facilitate tumor progression. In this study, we aimed to build a triad of breast cancer, obesity, and NK cell dysfunction to elucidate a link between these pillars on a cellular level. Directing efforts towards solidifying the link between these factors will help in designing a targeted immunotherapy with a low side-effect profile that can revolutionize breast cancer treatment and improve survival in obese patients.

Role of dietary fat on obesity-related postmenopausal breast cancer: insights from mouse models and methodological considerations

The increasing incidence rate of breast cancer in the last few decades is known to be linked to the upward trend of obesity prevalence worldwide. The consumption of high-fat diet in particular has been correlated with postmenopausal breast cancer risk. The underlying mechanisms, using suitable and reliable experimental mouse model, however, is lacking. The current review aims to discuss the evidence available from mouse models on the effects of dietary fats intake on postmenopausal breast cancer. We will further discuss the biochemical mechanisms involved in the occurrence of postmenopausal breast cancer. In addition, the methodological considerations and their limitations in obesity-related postmenopausal breast cancer, such as choice of mouse models and breast cancer cell lines as well as the study duration will be reviewed. The current review will provide a platform for further development of new xenograft models which may offer the opportunity to investigate the mechanisms of postmenopausal breast cancer in a greater detail.

Cellular and Molecular Players in the Interplay between Adipose Tissue and Breast Cancer

The incidence and severity of obesity are rising in most of the world. In addition to metabolic disorders, obesity is associated with an increase in the incidence and severity of a variety of types of cancer, including breast cancer (BC). The bidirectional interaction between BC and adipose cells has been deeply investigated, although the molecular and cellular players involved in these mechanisms are far from being fully elucidated. Here, we review the current knowledge on these interactions and describe how preclinical research might be used to clarify the effects of obesity over BC progression and morbidity, with particular attention paid to promising therapeutic interventions.

High-Fat Diet and Feeding Regime Impairs Number, Phenotype, and Cytotoxicity of Natural Killer Cells in C57BL/6 Mice

Overweight and obesity are major public health challenges worldwide. Obesity is associated with a higher risk for the development of several cancer types, but specific mechanisms underlying the link of obesity and cancer are still unclear. Natural killer (NK) cells are circulating lymphoid cells promoting the elimination of virus-infected and tumor cells. Previous investigations demonstrated conflicting results concerning the influence of obesity on functional NK cell parameters in small animal models. The aim of the present study was to clarify potential obesity-associated alterations of murine NK cells in vivo, implementing different feeding regimes. Therefore, C57BL/6 mice were fed a normal-fat diet (NFD) or high-fat diet (HFD) under restrictive and ad libitum feeding regimes. Results showed diet and feeding-regime dependent differences in body weight, visceral fat mass and plasma cytokine concentrations. Flow cytometry analyses demonstrated significant changes in total cell counts as well as frequencies of immune cell populations in peripheral blood comparing mice fed NFD or HFD in an ad libitum or restrictive manner. Mice fed the HFD showed significantly decreased frequencies of total NK cells and the mature CD11b⁺CD27⁺ NK cell subset compared to mice fed the NFD. Feeding HFD resulted in significant changes in the expression of the maturation markers KLRG1 and CD127 in NK cells. Furthermore, real-time PCR analyses of NK-cell related functional parameters in adipose tissue revealed significant diet and feeding-regime dependent differences. Most notable, real-time cytotoxicity assays demonstrated an impaired cytolytic activity of splenic NK cells toward murine colon cancer cells in HFD-fed mice compared to NFD-fed mice. In conclusion, our data demonstrate that feeding a high-fat diet influences the frequency, phenotype and function of NK cells in C57BL/6 mice. Interestingly, restricted feeding of HFD compared to ad libitum feeding resulted in a partial prevention of the obesity-associated alterations on immune cells and especially on NK cells, nicely fitting with the current concept of an advantage for interval fasting for improved health.

Characterization of Surface Receptor Expression and Cytotoxicity of Human NK Cells and NK Cell Subsets in Overweight and Obese Humans

Obesity is associated with an increased risk for several cancer types and an altered phenotype and functionality of natural killer (NK) cells. This study aimed to investigate the association of overweight and obesity with NK cell functions and receptor expression profiles in humans. Therefore, peripheral blood mononuclear cells were isolated from normal weight, overweight, and obese healthy blood donors. In depth analysis of immune cell populations and 23 different surface markers, including NK cell receptors, NK-cell-related markers as well as functional intracellular markers on total NK cells and NK subgroups were performed by multicolor flow cytometry. The data revealed a decreased expression of the activating NK cell receptors KIR2DS4 and NKp46 as well as an increased expression of the inhibitory NK cell receptors NKG2A and Siglec-7 in overweight and obese compared to normal weight individuals. Additionally, the expression of the adhesion molecule CD62L and the maturation and differentiation marker CD27 was downregulated in NK cells of overweight and obese subjects. Furthermore, the cytotoxicity of NK cells against colorectal cancer cells was decreased in overweight and obese subjects. Investigations on underlying killing mechanisms demonstrated a reduced TRAIL expression on NK cells of obese subjects suggesting an impaired death receptor pathway in obesity. The present study gives new insights into an impaired functionality and phenotype of NK cells and NK cell subsets in overweight and obesity. These phenotypic alterations and dysfunction of NK cells might be an explanation for the increased cancer risk in obesity.

Characterization of natural killer cells in colorectal tumor tissue of rats fed a control diet or a high-fat diet

BACKGROUND

Obesity is a major public health problem with an increasing prevalence reaching pandemic levels. The incidence and mortality for colorectal cancer is augmented in overweight and obese individuals. Previous studies demonstrated an impaired number, phenotype and functionality of natural killer (NK) cells under obese conditions. So far, the influence of obesity on NK cells in colorectal cancer tissue remained unclear. Therefore, the aim of the study was to investigate the occurrence and localization of NK cells in colorectal tumors of normal weight and diet-induced obese rats.

METHODS

Wistar rats were fed a normal-fat diet (control) or a high-fat diet (HFD) to induce obesity. In half of the experimental groups azoxymethane (AOM) was injected to induce colorectal cancer. Tumors in colon and rectum were histopathologically classified in adenomas and adenocarcinomas and immunohistologically stained with the rat NK cell marker CD161. Occurrence and localization of NK cells were analyzed and quantified in the tunica mucosa and tunica submucosa of colorectal adenomas and the tunica submucosa of colorectal adenocarcinomas.

RESULTS

NK cells are localized in the tunica mucosa and the tunica submucosa of colorectal tumors with NK cell accumulations as follicle-like aggregates especially in regions of the lamina muscularis mucosae and the lamina propria mucosae of the tunica mucosa as well as in regions of the tunica submucosa adjacent to the lamina muscularis mucosae. Although not statistically significant, the CD161 staining was clearly reduced in the tunica mucosa of colorectal tumors of rats fed a HFD compared to rats fed a control diet. Moreover, the CD161 staining in the tunica mucosa was positively correlated with the final body weight of AOM-treated rats independent of the supplied diet.

DISCUSSION

For the first time, these results provide information about the localization and quantity of NK cells in colorectal tumor tissue of rats fed a control diet or high-fat diet. The slight reduction of NK cell number in colorectal tissue of rats fed a high-fat diet may contribute to an impaired tumor defense and the increased colorectal tumor outcome in diet-induced obese rats.

Obesity-Associated Alterations of Natural Killer Cells and Immunosurveillance of Cancer

Obesity is accompanied by a systemic chronic low-grade inflammation as well as dysfunctions of several innate and adaptive immune cells. Recent findings emphasize an impaired functionality and phenotype of natural killer (NK) cells under obese conditions. This review provides a detailed overview on research related to overweight and obesity with a particular focus on NK cells. We discuss obesity-associated alterations in subsets, distribution, phenotype, cytotoxicity, cytokine secretion, and signaling cascades of NK cells investigated in vitro as well as in animal and human studies. In addition, we provide recent insights into the effects of physical activity and obesity-associated nutritional factors as well as the reduction of body weight and fat mass on NK cell functions of obese individuals. Finally, we highlight the impact of impaired NK cell physiology on obesity-associated diseases, focusing on the elevated susceptibility for viral infections and increased risk for cancer development and impaired treatment response.

Elevated tumor LDLR expression accelerates LDL cholesterol-mediated breast cancer growth in mouse models of hyperlipidemia

Obesity is associated with an increase in cancer-specific mortality in women with breast cancer. Elevated cholesterol, particularly low-density lipoprotein cholesterol (LDL-C) is frequently seen in obese women. Here, we aimed to determine the importance of elevated circulating LDL, and LDL receptor (LDLR) expression in tumor cells, on the growth of breast cancer using mouse models of hyperlipidemia. We describe two novel immunodeficient mouse models of hyperlipidemia (Rag1^−/−/LDLR^−/− and Rag1^−/−/ApoE (apolipoprotein E)^−/− mice), in addition to established immunocompetent LDLR^−/− and ApoE^−/− mice. The mice were used to study the effects of elevated LDL-C in human triple negative (MDA-MB-231) and mouse Her2/Neu overexpressing (MCNeuA) breast cancers. Tumors derived from MCNeuA and MDA-MB-231 cells had high LDLR expression and formed larger tumors in mice with high circulating LDL-C concentrations than in mice with lower LDL-C. Silencing the LDLR in the tumor cells led to decreased growth of Her2Neu overexpressing tumors in LDLR^−/− and ApoE^−/− mice, with increased Caspase 3 cleavage. Additionally, in vitro, silencing the LDLR led to decreased cell survival in serum-starved conditions, associated with Caspase 3 cleavage. Examining publically available human datasets, we found that high LDLR expression in human breast cancers was associated with decreased recurrence-free survival, particularly in patients treated with systemic therapies. Overall, our results highlight the importance of the LDLR in the growth of triple negative and HER2 overexpressing breast cancers in the setting of elevated circulating LDL-C, which may be important contributing factors to the increased recurrence and mortality in obese women with breast cancer.

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.

Crown-like Structures in Breast Adipose Tissue from Normal Weight Women: Important Impact

Crown-like structures (CLS), composed of macrophages surrounding dead or dying adipocytes, are a histologic hallmark of the proinflammatory process by which adipose tissue contributes to the increased risk and worse prognosis of breast cancer in obese, postmenopausal patients. In this issue of Cancer Prevention Research, Iyengar and colleagues report the intriguing finding that CLS can be identified in a significant proportion of normal-BMI women undergoing mastectomy for breast cancer risk reduction or therapy. This surprising observation suggests that some normal weight women may have similar mechanisms driving initiation and/or progression of breast cancer as those contributing to the increased incidence and worse prognosis of breast cancer in obese postmenopausal women. The possibility of a common mechanism in both lean and obese women provides added impetus to more fully define this process and evaluate its important implications for prevention and screening strategies as well as therapeutic interventions. Cancer Prev Res; 10(4); 223-5. ©2017 AACRSee related article by Iyengar et al., p. 235-43.

Role of metabolism during viral infections, and crosstalk with the innate immune system

Viruses have been for long polemic biological particles which stand in the twilight of being living entities or not. As their genome is reduced, they rely on the metabolic machinery of their host in order to replicate and be able to continue with their infection process. The understanding of their metabolic requirements is thus of paramount importance in order to develop tailored drugs to control their population, without affecting the normal functioning of their host. New advancements in high throughput technologies, especially metabolomics are allowing researchers to uncover the metabolic mechanisms of viral replication. In this short review, we present the latest discoveries that have been made in the field and an overview of the intrinsic relationship between metabolism and innate immunity as an important part of the immune system.

Enhancement of Lytic Activity by Leptin Is Independent From Lipid Rafts in Murine Primary Splenocytes

Leptin, a pleiotropic adipokine, is known as a regulator of food intake, but it is also involved in inflammation, immunity, cell proliferation, and survival. Leptin receptor is integrated inside cholesterol-rich microdomains called lipid rafts, which, if disrupted or destroyed, could lead to a perturbation of lytic mechanism. Previous studies also reported that leptin could induce membrane remodeling. In this context, we studied the effect of membrane remodeling in lytic activity modulation induced by leptin. Thus, primary mouse splenocytes were incubated with methyl-β-cyclodextrin (β-MCD), a lipid rafts disrupting agent, cholesterol, a major component of cell membranes, or ursodeoxycholic acid (UDCA), a membrane stabilizer agent for 1 h. These treatments were followed by splenocyte incubation with leptin (absence, 10 and 100 ng/ml). Unlike β-MCD or cholesterol, UDCA was able to block leptin lytic induction. This result suggests that leptin increased the lytic activity of primary spleen cells against syngenic EO771 mammary cancer cells independently from lipid rafts but may involve membrane fluidity. Furthermore, natural killer cells were shown to be involved in the splenocyte lytic activity. To our knowledge it is the first publication in primary culture that provides the link between leptin lytic modulation and membrane remodeling. J. Cell. Physiol. 232: 101-109, 2017. © 2016 Wiley Periodicals, Inc.

The Association between Dairy Intake and Breast Cancer in Western and Asian Populations: A Systematic Review and Meta-Analysis

Purpose

To date, studies investigating the association between dairy consumption and breast cancer in women have produced conflicting results. As diet is an important, modifiable factor affecting cancer development, the aim of this study was to examine the association between dairy consumption and breast cancer risk.

Methods

PubMed, Embase, and Cochrane Library databases were searched with a priority for prospective cohort studies. Case-control studies were also considered in case of the absence of a cohort study.

Results

We analyzed 22 prospective cohort studies (1,566,940 participants) and five case-control studies (33,372 participants). High and modest dairy consumption (>600 and 400-600 g/day, respectively) significantly reduced the risk of breast cancer compared with low dairy consumption (<400 g/day; risk ratio [RR], 0.90, 95% confidence interval [CI], 0.83-0.98, and RR, 0.94, 95% CI, 0.91-0.98, respectively). A significant linear relationship between dairy consumption and breast cancer risk was found on dose-response analysis. Subgroup analysis found that yogurt (RR, 0.91; 95% CI, 0.83-0.99) and low-fat dairy (RR, 0.85; 95% CI, 0.75-0.96) reduced the risk of breast cancer, while other dairy product types did not. A reduced risk was observed for people in the United States (RR, 0.91; 95% CI, 0.83-0.99) and in those followed for ≥10 years (RR, 0.90; 95% CI, 0.81-0.99). Additionally, the highest level of dairy consumption among Asians was associated with a reduced risk of breast cancer (odds ratio, 0.74; 95% CI, 0.62-0.88).

Conclusion

Dairy consumption was inversely associated with the risk of developing breast cancer and this effect was dependent on the dose, dairy-type, and time.

A nude mouse model of obesity to study the mechanisms of resistance to aromatase inhibitors

Obesity is a risk factor for breast cancer progression. Breast cancer patients who are overweight or obese or have excess abdominal fat have an increased risk of local or distant recurrence and cancer-related death. Hormone depletion therapies can also cause weight gain, exacerbating the risk for these patients. To understand the effect of obesity on hormone-dependent human breast cancer tumors, we fed ovariectomized athymic nude mice a diet containing 45% kcal fat and 17% kcal sucrose (high fat sucrose diet (HFSD)), 10% kcal fat (low fat diet (LFD)), or a standard chow diet (chow). The mice fed the HFSD developed metabolic abnormalities consistent with the development of obesity such as weight gain, high fasting blood glucose, and impaired glucose tolerance. These mice also developed hyperinsulinemia and insulin resistance. The obese mice also had a higher tumor growth rate compared to the lean mice. Furthermore, the obese mice showed a significantly reduced responsiveness to letrozole. To understand the role of obesity in this reduced responsiveness, we examined the effect of insulin on the growth of MCF-7Ca cells in response to estrogen or letrozole. The presence of insulin rendered MCF-7Ca cells less responsive to estrogen and letrozole. Exogenous insulin treatment of MCF-7Ca cells also resulted in increased p-Akt as well as ligand-independent phosphorylation of ERα. These findings suggest that diet-induced obesity may result in reduced responsiveness of tumors to letrozole due to the development of hyperinsulinemia. We conclude that obesity influences the response and resistance of breast cancer tumors to aromatase inhibitor treatment.

Leptin, adipocytes and breast cancer: Focus on inflammation and anti-tumor immunity

More than one million new cases of breast cancer are diagnosed worldwide each year and more than 400,000 deaths are caused by the disease. The origin of this pathology is multifactorial and involved genetic, hormonal, environmental and nutritional factors including obesity in postmenopausal women. The role played by the adipose tissue and their secretions, ie adipokines, is beginning to be recognized. Plasma adipokine levels, which are modulated during obesity, could have “remote” effects on mammary carcinogenesis. Breast cancer cells are surrounded and locally influenced by an adipocyte microenvironment, which is probably more extensive in obese people. Hence, leptin appears to be strongly involved in mammary carcinogenesis and may contribute to the local pro-inflammatory mechanisms, especially in obese patients, who have increased metastatic potential and greater risk of mortality. This review presents the multifaceted role of leptin in breast cancer development and the different molecular pathways involved such as inflammation, oxidative stress and antitumor immunity.