Leptin mediates tumor-stromal interactions that promote the invasive growth of breast cancer cells

MIG6 loss confers resistance to ALK/ROS1 inhibitors in NSCLC through EGFR activation by low-dose EGF

Although tyrosine kinase inhibitor (TKI) therapy shows marked clinical efficacy in patients with anaplastic lymphoma kinase-positive (ALK+) and ROS proto-oncogene 1-positive (ROS1+) non-small cell lung cancer (NSCLC), most of these patients eventually relapse with acquired resistance. Therefore, genome-wide CRISPR/Cas9 knockout screening was performed using an ALK+ NSCLC cell line established from pleural effusion without ALK-TKI treatment. After 9 days of ALK-TKI therapy, sequencing analysis was performed, which identified several tumor suppressor genes, such as NF2 or MED12, and multiple candidate genes. Among them, this study focused on ERRFI1, which is known as MIG6 and negatively regulates EGFR signaling. Interestingly, MIG6 loss induced resistance to ALK-TKIs by treatment with quite a low dose of EGF, which is equivalent to plasma concentration, through the upregulation of MAPK and PI3K/AKT/mTOR pathways. Combination therapy with ALK-TKIs and anti-EGFR antibodies could overcome the acquired resistance in both in vivo and in vitro models. In addition, this verified that MIG6 loss induces resistance to ROS1-TKIs in ROS1+ cell lines. This study found a potentially novel factor that plays a role in ALK and ROS1-TKI resistance by activating the EGFR pathway with low-dose ligands.

Heterotypic communication as the promoter of phenotypic plasticity of cancer cells: The role of cancer secretomes

Cellular communication relies on signaling circuits whose statuses are mainly modulated by soluble biomolecules such as carbohydrates, lipids, proteins, and metabolites as well as extracellular vesicles (EVs). Therefore, the active secretion of such biomolecules is critical for both cell homeostasis and proper pathophysiological responses in a timely fashion. In this context, proteins are among the main modulators of such biological responses. Hence, profiling cell line secretomes may be an opportunity for the identification of "signatures" of specific cell types (i.e., stromal or metastatic cells) with important prognostic/therapeutic value. This review will focus on the biological implications of cell secretomes in the context of cancer, as well as their functional roles in shaping the tumoral microenvironment (TME) and communication status of participating cells.

Role of Leptin and Adiponectin in Carcinogenesis

Hormones produced by adipocytes, leptin and adiponectin, are associated with the process of carcinogenesis. Both of these adipokines have well-proven oncologic potential and can affect many aspects of tumorigenesis, from initiation and primary tumor growth to metastatic progression. Involvement in the formation of cancer includes interactions with the tumor microenvironment and its components, such as tumor-associated macrophages, cancer-associated fibroblasts, extracellular matrix and matrix metalloproteinases. Furthermore, these adipokines participate in the epithelial-mesenchymal transition and connect to angiogenesis, which is critical for cancer invasiveness and cancer cell migration. In addition, an enormous amount of evidence has demonstrated that altered concentrations of these adipocyte-derived hormones and the expression of their receptors in tumors are associated with poor prognosis in various types of cancer. Therefore, leptin and adiponectin dysfunction play a prominent role in cancer and impact tumor invasion and metastasis in different ways. This review clearly and comprehensively summarizes the recent findings and presents the role of leptin and adiponectin in cancer initiation, promotion and progression, focusing on associations with the tumor microenvironment and its components as well as roles in the epithelial-mesenchymal transition and angiogenesis.

Leptin: A Heavyweight Player in Obesity-Related Cancers

Obesity, defined as the abnormal or excessive expansion of white adipose tissue, has reached pandemic proportions and is recognized as an important health concern since it is a common root for several comorbidities, including malignancies. Indeed, the current knowledge of the white adipose tissue, which shifts its role from an energy storage tissue to an important endocrine and metabolic organ, has opened up new avenues for the discovery of obesity's effects on tumor biology. In this review, we will report the epidemiological studies concerning the strong impact of obesity in several types of cancer and describe the mechanisms underlying the heterotypic signals between cancer cell lines and adipocytes, with particular emphasis on inflammation, the insulin/IGF-1 axis, and adipokines. Among the adipokines, we will further describe the in vitro, in vivo, and clinical data concerning the role of leptin, recognized as one of the most important mediators of obesity-associated cancers. In fact, leptin physiologically regulates energy metabolism, appetite, and reproduction, and several studies have also described the role of leptin in affecting cancer development and progression. Finally, we will summarize the newest pharmacological strategies aimed at mitigating the protumorigenic effects of leptin, underlining their mechanisms of action.

Effects of adipocyte-conditioned cell culture media on S1P treatment of human triple-negative breast cancer cells

Sphingosine-1-phosphate (S1P) is a potent sphingolipid metabolite that regulates a wide range of biological functions such as cell proliferation, cell apoptosis and angiogenesis. Its cellular level is elevated in breast cancer, which, in turn, would promote cancer cell proliferation, survival, growth and metastasis. However, the cellular concentration of S1P is normally in the low nanomolar range, and our previous studies showed that S1P selectively induced apoptosis of breast cancer cells at high concentrations (high nanomolar to low micromolar). Thus, local administration of high-concentration S1P alone or in combination of chemotherapy agents could be used to treat breast cancer. The breast mainly consists of mammary gland and connective tissue stroma (adipose), which are dynamically interacting each other. Thus, in the current study, we evaluated how normal adipocyte-conditioned cell culture media (AD-CM) and cancer-associated adipocyte-conditioned cell culture media (CAA-CM) would affect high-concentration S1P treatment of triple-negative breast cancer (TNBC) cells. Both AD-CM and CAA-CM may suppress the anti-proliferative effect and reduce nuclear alteration/apoptosis caused by high-concentration S1P. This implicates that adipose tissue is likely to be detrimental to local high-concentration S1P treatment of TNBC. Because the interstitial concentration of S1P is about 10 times higher than its cellular level, we undertook a secretome analysis to understand how S1P would affect the secreted protein profile of differentiated SGBS adipocytes. At 100 nM S1P treatment, we identified 36 upregulated and 21 downregulated secretome genes. Most of these genes are involved in multiple biological processes. Further studies are warranted to identify the most important secretome targets of S1P in adipocytes and illustrate the mechanism on how these target proteins affect S1P treatment of TNBC.

Leptin signaling in breast cancer and its crosstalk with peroxisome proliferator-activated receptors α and γ

Obesity may create a mitogenic microenvironment that influences tumor initiation and progression. The obesity-associated adipokine, leptin regulates energy metabolism and has been implicated in cancer development. It has been shown that some cell types other than adipocytes can express leptin and leptin receptors in tumor microenvironments. It has been shown that peroxisome proliferator-activated receptors (PPAR) agonists can affect leptin levels and vice versa leptin can affect PPARs. Activation of PPARs affects the expression of several genes involved in aspects of lipid metabolism. In addition, PPARs regulate cancer cell progression through their action on the tumor cell proliferation, metabolism, and cellular environment. Some studies have shown an association between obesity and several types of cancer, including breast cancer. There is some evidence that suggests that there is crosstalk between PPARs and leptin during the development of breast cancer. Through a systematic review of previous studies, we have reviewed the published relevant articles regarding leptin signaling in breast cancer and its crosstalk with peroxisome proliferator-activated receptors α and γ.

Crosstalk of Inflammatory Cytokines within the Breast Tumor Microenvironment

Several immune and immunocompetent cells, including dendritic cells, macrophages, adipocytes, natural killer cells, T cells, and B cells, are significantly correlated with the complex discipline of oncology. Cytotoxic innate and adaptive immune cells can block tumor proliferation, and others can prevent the immune system from rejecting malignant cells and provide a favorable environment for tumor progression. These cells communicate with the microenvironment through cytokines, a chemical messenger, in an endocrine, paracrine, or autocrine manner. These cytokines play an important role in health and disease, particularly in host immune responses to infection and inflammation. They include chemokines, interleukins (ILs), adipokines, interferons, colony-stimulating factors (CSFs), and tumor necrosis factor (TNF), which are produced by a wide range of cells, including immune cells, such as macrophages, B-cells, T-cells, and mast cells, as well as endothelial cells, fibroblasts, a variety of stromal cells, and some cancer cells. Cytokines play a crucial role in cancer and cancer-related inflammation, with direct and indirect effects on tumor antagonistic or tumor promoting functions. They have been extensively researched as immunostimulatory mediators to promote the generation, migration and recruitment of immune cells that contribute to an effective antitumor immune response or pro-tumor microenvironment. Thus, in many cancers such as breast cancer, cytokines including leptin, IL-1B, IL-6, IL-8, IL-23, IL-17, and IL-10 stimulate while others including IL-2, IL-12, and IFN-γ, inhibit cancer proliferation and/or invasion and enhance the body's anti-tumor defense. Indeed, the multifactorial functions of cytokines in tumorigenesis will advance our understanding of cytokine crosstalk pathways in the tumor microenvironment, such as JAK/STAT, PI3K, AKT, Rac, MAPK, NF-κB, JunB, cFos, and mTOR, which are involved in angiogenesis, cancer proliferation and metastasis. Accordingly, targeting and blocking tumor-promoting cytokines or activating and amplifying tumor-inhibiting cytokines are considered cancer-directed therapies. Here, we focus on the role of the inflammatory cytokine system in pro- and anti-tumor immune responses, discuss cytokine pathways involved in immune responses to cancer and some anti-cancer therapeutic applications.

Leptin stimulates migration and invasion and maintains cancer stem‑like properties in gastric cancer cells

Obesity is a risk factor for various types of cancer. Leptin, an adipocyte-derived hormone, may stimulate the proliferation of gastric cancer cells. However, the effect of leptin and underlying mechanism in gastric cancer remain unclear. In the present study, the role of leptin in gastric cancer was evaluated. The effect of leptin on the JAK-STAT and MEK signaling pathways was investigated in gastric cancer cells using wound-healing and cell invasion assays, immunoblotting and inhibition studies. Cancer-initiating cells derived from gastric cancer cells were used to investigate the effect of leptin on the maintenance of stemness and epithelial-mesenchymal transition (EMT) by immunoblotting. Clinicopathological characteristics including the serum leptin level and overall survival (OS) were analyzed in patients with (n=23) and without (n=23) obesity. Leptin induced the migration and invasion of gastric cancer cells by activating AKT and ERK and upregulating vascular endothelial growth factor (VEGF). Leptin increased the mRNA and protein levels of markers of stemness (CD44) and the EMT (Snail and N-cadherin). Pharmacological inhibitors of the JAK-STAT and MEK signaling pathways decreased leptin-induced migration and invasion, and the expression of VEGF. Obesity was associated with an elevated leptin level and body mass index was positively correlated with the leptin level (P=0.001 for both). The 5-year OS rate was not significantly different between the two groups (P=0.098). Leptin stimulates the migration and invasion of gastric cancer cells by activating the JAK-STAT and MEK pathways, and contributes to the maintenance of cancer stemness and metastatic potential. The present findings support an adverse effect of obesity in gastric cancer. Consequently, targeting of leptin-associated signaling pathways may have therapeutic potential for gastric cancer.

Obesity and Breast Cancer Risk: The Oncogenic Implications of Metabolic Dysregulation

CONTEXT

Breast cancer is increasing in prevalence in parallel with rising rates of obesity worldwide. Obesity is recognized as a leading modifiable risk factor for the development of breast cancer; however, this association varies considerably by clinicopathologic features, and the underlying mechanisms are complex.

EVIDENCE ACQUISITION

Pubmed literature search using combinations of "obesity," "breast cancer risk," "diet," "exercise," "weight gain," "weight loss," "adipose tissue inflammation," "crown-like structure," "immune markers," "metformin," "gliflozins," "SGLT-2i," "GLP1-RA," and related terms.

EVIDENCE SYNTHESIS

Elevated body mass index and weight gain are associated with increased risk of postmenopausal, hormone receptor-positive breast cancer. Emerging evidence suggests that adverse measures of body composition in individuals of any weight can also confer increased breast cancer risk. Mechanistically, various factors including altered adipokine balance, dysfunctional adipose tissue, dysregulated insulin signaling, and chronic inflammation contribute to tumorigenesis. Weight loss and more specifically fat mass loss through lifestyle and pharmacologic interventions improve serum metabolic and inflammatory markers, sex hormone levels, and measures of breast density, suggesting a link to decreased breast cancer risk.

CONCLUSION

Incorporating markers of metabolic health and body composition measures with body mass index can capture breast cancer risk more comprehensively. Further studies of interventions targeting body fat levels are needed to curb the growing prevalence of obesity-related cancer.

Advances in the Prevention and Treatment of Obesity-Driven Effects in Breast Cancers

Obesity and associated chronic inflammation were shown to facilitate breast cancer (BC) growth and metastasis. Leptin, adiponectin, estrogen, and several pro-inflammatory cytokines are involved in the development of obesity-driven BC through the activation of multiple oncogenic and pro-inflammatory pathways. The aim of this study was to assess the reported mechanisms of obesity-induced breast carcinogenesis and effectiveness of conventional and complementary BC therapies. We screened published original articles, reviews, and meta-analyses that addressed the involvement of obesity-related signaling mechanisms in BC development, BC treatment/prevention approaches, and posttreatment complications. PubMed, Medline, eMedicine, National Library of Medicine (NLM), and ReleMed databases were used to retrieve relevant studies using a set of keywords, including "obesity," "oncogenic signaling pathways," "inflammation," "surgery," "radiotherapy," "conventional therapies," and "diet." Multiple studies indicated that effective BC treatment requires the involvement of diet- and exercise-based approaches in obese postmenopausal women. Furthermore, active lifestyle and diet-related interventions improved the patients' overall quality of life and minimized adverse side effects after traditional BC treatment, including postsurgical lymphedema, post-chemo nausea, vomiting, and fatigue. Further investigation of beneficial effects of diet and physical activity may help improve obesity-linked cancer therapies.

Targeting obesity-related dysfunction in hormonally driven cancers

Obesity is a risk factor for at least 13 different types of cancer, many of which are hormonally driven, and is associated with increased cancer incidence and morbidity. Adult obesity rates are steadily increasing and a subsequent increase in cancer burden is anticipated. Obesity-related dysfunction can contribute to cancer pathogenesis and treatment resistance through various mechanisms, including those mediated by insulin, leptin, adipokine, and aromatase signalling pathways, particularly in women. Furthermore, adiposity-related changes can influence tumour vascularity and inflammation in the tumour microenvironment, which can support tumour development and growth. Trials investigating non-pharmacological approaches to target the mechanisms driving obesity-mediated cancer pathogenesis are emerging and are necessary to better appreciate the interplay between malignancy, adiposity, diet and exercise. Diet, exercise and bariatric surgery are potential strategies to reverse the cancer-promoting effects of obesity; trials of these interventions should be conducted in a scientifically rigorous manner with dose escalation and appropriate selection of tumour phenotypes and have cancer-related clinical and mechanistic endpoints. We are only beginning to understand the mechanisms by which obesity effects cell signalling and systemic factors that contribute to oncogenesis. As the rates of obesity and cancer increase, we must promote the development of non-pharmacological lifestyle trials for the treatment and prevention of malignancy.

Adipokines expression and epithelial cell polarity in normal and cancerous breast tissue

Cell polarity is crucial for the correct structural and functional organization of epithelial tissue. Its disruption can lead to loss of the apicobasal polarity, alteration in the intracellular components, misregulation of the pathways involved in cell proliferation and cancer promotion. Very recent in vitro/in vivo findings demonstrated that obesity-associated alterations in tissue adipokines protein level negatively affect epithelial polarity. We performed an in silico study to investigate whether such alterations also occur in surgical samples. We aimed to explore the relationship among the expression of the genes coding for leptin (LEP), adiponectin (ADIPOQ), adipokine receptors (LEPR, ADIPOR1 and ADIPOR2), and a panel of polarity-associated genes in normal tissue from breast reduction mammoplasty, and a series of paired samples of histologically normal (HN) tissue and invasive cancer. Results indicated that, in normal tissue, the expression of adipokines and their receptors negatively correlated with that of the polarity-associated genes and GGT1, which codes for γ-glutamyl transferase (GGT) enzyme, a marker of cell distress and membrane disruption. This negative correlation progressively decreased in HN and cancerous tissue, and loss of correlation between ADIPOR2 and polarity-associated genes appeared the most noticeable alteration. Given the growing role of obesity in breast cancer etiology and the opposite action of leptin and adiponectin in epithelial tissue remodeling, ADIPOR2 loss could be addressed as a key mechanism leading to an unbalanced leptin stimulatory activity, subsequent cell polarity disruption and eventually tumor initiation, a finding that requires to be confirmed also at the protein level and with in vivo models.

Predictive Role of Leptin Receptor (Ob-R) Overexpression in Patients with Early Breast Cancer Receiving Neoadjuvant Systemic Treatment

The primary aim of this retrospective study was to investigate the correlation between the immunohistochemical expression of Ob-R (leptin receptor) with pCR (pathological complete response) in early breast cancer patients receiving neoadjuvant systemic treatment (NST). A total of 100 women with breast cancer receiving NST (2017-2020) followed by surgical resection were retrospectively obtained. Demographic parameters and clinicopathological factors (e.g., treatment modalities, immunohistochemistry (IHC), and cancer subtype) were obtained from the patient's clinical records. In the analyzed breast cancer cohort, high expression of Ob-R was found in 52% of tumors and there was a significantly higher incidence in the HER2+ and TNBC subgroups. Overall, a significantly greater percentage of patients with Ob-R positive tumors achieved pCR compared with Ob-R negative patients (57.7% vs. 27.1%; p = 0.002). This result was observed in most breast cancer subtypes. In patients with HER2+ breast cancer, there was no difference in Ob-R expression in relation to the HR status. Ob-R cell positivity was significantly higher in younger breast cancer patients (p = 0.008), those who were premenopausal (p = 0.011), and in those with a BMI > 25 kg/m² (p = 0.019). A significantly greater percentage of early breast cancer patients with Ob-R positive tumors achieved pCR compared with Ob-R negative patients. Furthermore, breast cancer patients with positive Ob-R expression were significantly younger than those with negative Ob-R expression. This association was not explained by differences in BMI between young and old patients.

S100A4 Is Involved in Stimulatory Effects Elicited by the FGF2/FGFR1 Signaling Pathway in Triple-Negative Breast Cancer (TNBC) Cells

Triple-negative breast cancer (TNBC) is an aggressive breast tumor subtype characterized by poor clinical outcome. In recent years, numerous advancements have been made to better understand the biological landscape of TNBC, though appropriate targets still remain to be determined. In the present study, we have determined that the expression levels of FGF2 and S100A4 are higher in TNBC with respect to non-TNBC patients when analyzing “The Invasive Breast Cancer Cohort of The Cancer Genome Atlas” (TCGA) dataset. In addition, we have found that the gene expression of FGF2 is positively correlated with S100A4 in TNBC samples. Performing quantitative PCR, Western blot, CRISPR/Cas9 genome editing, promoter studies, immunofluorescence analysis, subcellular fractionation studies, and ChIP assays, we have also demonstrated that FGF2 induces in TNBC cells the upregulation and secretion of S100A4 via FGFR1, along with the ERK1/2–AKT–c-Rel transduction signaling. Using conditioned medium from TNBC cells stimulated with FGF2, we have also ascertained that the paracrine activation of the S100A4/RAGE pathway triggers angiogenic effects in vascular endothelial cells (HUVECs) and promotes the migration of cancer-associated fibroblasts (CAFs). Collectively, our data provide novel insights into the action of the FGF2/FGFR1 axis through S100A4 toward stimulatory effects elicited in TNBC cells.

Tumor Metabolic Reprogramming by Adipokines as a Critical Driver of Obesity-Associated Cancer Progression

Adiposity is associated with an increased risk of various types of carcinoma. One of the plausible mechanisms underlying the tumor-promoting role of obesity is an aberrant secretion of adipokines, a group of hormones secreted from adipose tissue, which have exhibited both oncogenic and tumor-suppressing properties in an adipokine type- and context-dependent manner. Increasing evidence has indicated that these adipose tissue-derived hormones differentially modulate cancer cell-specific metabolism. Some adipokines, such as leptin, resistin, and visfatin, which are overproduced in obesity and widely implicated in different stages of cancer, promote cellular glucose and lipid metabolism. Conversely, adiponectin, an adipokine possessing potent anti-tumor activities, is linked to a more favorable metabolic phenotype. Adipokines may also play a pivotal role under the reciprocal regulation of metabolic rewiring of cancer cells in tumor microenvironment. Given the fact that metabolic reprogramming is one of the major hallmarks of cancer, understanding the modulatory effects of adipokines on alterations in cancer cell metabolism would provide insight into the crosstalk between obesity, adipokines, and tumorigenesis. In this review, we summarize recent insights into putative roles of adipokines as mediators of cellular metabolic rewiring in obesity-associated tumors, which plays a crucial role in determining the fate of tumor cells.

Targeting Metabolic Cross Talk Between Cancer Cells and Cancer-Associated Fibroblasts

Although cancer has classically been regarded as a genetic disease of uncontrolled cell growth, the importance of the tumor microenvironment (TME) [1, 2] is continuously emphasized by the accumulating evidence that cancer growth is not simply dependent on the cancer cells themselves [3, 4] but also dependent on angiogenesis [5-8], inflammation [9, 10], and the supporting roles of cancer-associated fibroblasts (CAFs) [11-13]. After the discovery that CAFs are able to remodel the tumor matrix within the TME and provide the nutrients and chemicals to promote cancer cell growth [14], many studies have aimed to uncover the cross talk between cancer cells and CAFs. Moreover, a new paradigm in cancer metabolism shows how cancer cells act like "metabolic parasites" to take up the high-energy metabolites, such as lactate, ketone bodies, free fatty acids, and glutamine from supporting cells, including CAFs and cancer-associated adipocytes (CAAs) [15, 16]. This chapter provides an overview of the metabolic coupling between CAFs and cancer cells to further define the therapeutic options to disrupt the CAF-cancer cell interactions.

The Primary Cilium of Adipose Progenitors Is Necessary for Their Differentiation into Cancer-Associated Fibroblasts that Promote Migration of Breast Cancer Cells In Vitro

Cancer associated fibroblasts (CAFs) are central elements of the microenvironment that control tumor development. In breast cancer, CAFs can originate from adipose progenitors (APs). We, and others, have shown that the primary cilium, an antenna-shaped organelle, controls several aspects of APs’ biology. We studied the conversion of human APs into CAFs by breast cancer cell lines (BCCs). Deletion of the cilium of APs by a pharmacological inhibitor, or by siRNA, allow us to demonstrate that the cilium is necessary for the differentiation of APs into CAFs. BCCs increase production of TGF-β1 by APs, which is a known inducer of CAFs. Pharmacological inhibition of TGF-β1 signaling in APs prevents their conversion into CAFs. Since we previously showed that deletion of the APs’ cilium inhibits TGF-β1 signaling, we propose that BCCs induce TGF-β1 production in Aps, which binds to the primary cilium of Aps and leads to their differentiation into CAFs. Inhibition of APs conversion into CAFs induces a loss in some of the biological effects of CAFs since deletion of the cilium of APs decreases their effect on the migration of BCCs. This is the first observation of a function of the cilium of APs in their conversion into CAFs, and its consequences on BCCs.

The metastatic phenotype shift toward myofibroblast of adipose-derived mesenchymal stem cells promotes ovarian cancer progression

Ovarian cancer metastasizes to organs in the abdominal cavity, such as the omentum that is a rich source of adipose-derived mesenchymal stem cells (ADSCs). In present, ADSCs have received more and more attention for their roles in the development of cancer. In this study, we examined α-smooth muscle actin (α-SMA) expression and carcinoma-associated fibroblast (CAF)-like differentiation capabilities in ADSCs from omentum of different patients. The effects of ADSCs on the proliferation and invasion of epithelial ovarian cancer cells (EOCCs) were also assessed in vitro and in vivo. Our results showed that ADSCs from omentum of ovarian cancer patients, no matter whether metastasis or not, expressed higher levels of α-SMA than ADSCs from patients with benign gynecologic disease. Using direct and indirect co-culture system, we found that EOCCs induced ADSCs to express CAF markers, including α-SMA and fibroblast activation protein, via the transforming growth factor beta 1 (TGF-β1) signaling pathway. Moreover, co-cultured ADSCs exhibited functional properties similar to those of CAFs, including the ability to promote EOCCs proliferation, progression and metastasis both in vitro and in vivo. Furthermore, blocking the TGF-β1 pathway can counteract the CAF-like differentiation and tumor promotion effect of ADSCs. Our results suggest that ADSCs are a source of CAFs and that they participate in the interaction between EOCCs and the omental microenvironment. EOCCs could induce ADSCs in the omentum to differentiate before ovarian cancer metastasis, which participate in the formation of omental metastatic niches and promote the proliferation and invasion of ovarian cancer.

The Thousand Faces of Leptin in the Lung

Leptin is a pleotropic hormone known to regulate a wide range of systemic functions, from satiety to inflammation. Increasing evidence has shown that leptin and its receptor (ObR) are not only expressed in adipose tissue but also in several organs, including the lungs. Leptin levels were first believed to be elevated only in the lungs of obese patients, and leptin was suspected to be responsible for obesity-related lung complications. Aside from obesity, leptin displays many faces in the respiratory system, independently of body weight, as this cytokine-like hormone plays important physiological roles, from the embryogenic state to maturation of the lungs and the control of ventilation. The leptin-signaling pathway is also involved in immune modulation and cell proliferation, and its dysregulation can lead to the onset of lung diseases. This review article addresses the thousand faces of leptin and its signaling in the lungs under physiological conditions and in disease.

Knockdown of Leptin Receptor Affects Macrophage Phenotype in the Tumor Microenvironment Inhibiting Breast Cancer Growth and Progression

Aberrant leptin (Ob) signaling, a hallmark of obesity, has been recognized to influence breast cancer (BC) biology within the tumor microenvironment (TME). Here, we evaluated the impact of leptin receptor (ObR) knockdown in affecting BC phenotype and in mediating the interaction between tumor cells and macrophages, the most abundant immune cells within the TME. The stable knockdown of ObR (ObR sh) in ERα-positive and ERα-negative BC cells turned the tumor phenotype into a less aggressive one, as evidenced by in vitro and in vivo models. In xenograft tumors and in co-culture experiments between circulating monocytes and BC cells, the absence of ObR reduced the recruitment of macrophages, and also affected their cytokine mRNA expression profile. This was associated with a decreased expression and secretion of monocyte chemoattractant protein-1 in ObR sh clones. The loss of Ob/ObR signaling modulated the immunosuppressive TME, as shown by a reduced expression of programmed death ligand 1/programmed cell death protein 1/arginase 1. In addition, we observed increased phagocytic activity of macrophages compared to control Sh clones in the presence of ObR sh-derived conditioned medium. Our findings, addressing an innovative role of ObR in modulating immune TME, may open new avenues to improve BC patient health care.

Cancer associated fibroblasts: role in breast cancer and potential as therapeutic targets

Introduction: Cancer associated fibroblasts (CAFs) are the largest population of stromal cells in breast tumors. Emerging evidence has suggested that CAFs are important players not only in fostering tumor growth and spread but also in altering the tumor response to therapeutic agents. On the basis of these observations, huge efforts have been made to exploit CAFs as potential targets for breast cancer therapy.Areas covered: The current understanding of the hallmarks and biology of CAFs, their multilayered interplay with various cell populations of breast tumor microenvironment toward cancer initiation, progression, metastasis and resistance to anticancer therapies are discussed. In addition, a comprehensive overview of the CAFs-based molecular druggable targets in breast tumors is provided. The most relevant literature, in particular the studies retrieved in Medline in the last 10 years, served for this purpose.Expert opinion: The interest on CAFs as a target to fight breast cancer has becoming a hot topic for drug discovery. Indeed, several CAFs-targeted approaches are emerging as appealing therapeutic strategies in breast cancer. At pre-clinical level, this research field is speedily advancing toward the assessment of successful tactics targeting CAFs in breast cancer. Therefore, anti-CAFs therapies may display an intriguing potential to be exploited in clinical studies.

Leptin Signaling Contributes to Aromatase Inhibitor Resistant Breast Cancer Cell Growth and Activation of Macrophages

Obesity represents a risk factor for breast cancer development and therapy resistance, but the molecular players underling these links are unclear. Here, we identify a role for the obesity-cytokine leptin in sustaining aromatase inhibitor (AI) resistant growth and progression in breast cancer. Using as experimental models MCF-7 breast cancer cells surviving long-term treatment with the AI anastrozole (AnaR) and Ana-sensitive counterparts, we found that AnaR cells expressed higher levels of leptin and its receptors (ObR) along with a constitutive activation of downstream effectors. Accordingly, leptin signaling inhibition reduced only AnaR cell growth and motility, highlighting the existence of an autocrine loop in mechanisms governing drug-resistant phenotypes. In agreement with ObR overexpression, increasing doses of leptin were able to stimulate to a greater extent growth and migration in AnaR than sensitive cells. Moreover, leptin contributed to enhanced crosstalk between AnaR cells and macrophages within the tumor microenvironment. Indeed, AnaR, through leptin secretion, modulated macrophage profiles and increased macrophage motility through CXCR4 signaling, as evidenced by RNA-sequencing, real-time PCR, and immunoblotting. Reciprocally, activated macrophages increased AnaR cell growth and motility in coculture systems. In conclusion, acquired AI resistance is accompanied by the development of a leptin-driven phenotype, highlighting the potential clinical benefit of targeting this cytokine network in hormone-resistant breast cancers, especially in obese women.

Leptin in Tumor Microenvironment

Leptin is a hormone that plays a major role as mediator of long-term regulation of energy balance, suppressing food intake, and stimulating weight loss. More recently, important physiological roles other than controlling appetite and energy expenditure have been suggested for leptin, including neuroendocrine, reparative, reproductive, and immune functions. These emerging peripheral roles let hypothesize that leptin can modulate also cancer progression. Indeed, many studies have demonstrated that elevated chronic serum concentrations of leptin, frequently seen in obese subjects, represent a stimulatory signal for tumor growth. Current knowledge indicates that also different non-tumoral cells resident in tumor microenvironment may respond to leptin creating a favorable soil for cancer cells. In addition, leptin is produced also within the tumor microenvironment creating the possibility for paracrine and autocrine action. In this review, we describe the main mechanisms that regulate peripheral leptin availability and how leptin can shape tumor microenvironment.

Stromal-associated cytokines bias the interplay between gene expression and DNA methylation in human breast cancers

In human tumours, the crosstalk between cancer cells and their microenvironment is involved in tumour progression, metastasis and resistance to anti-cancer therapies. Among the factors involved in this exchange of information pro-inflammatory cytokines seem to play a crucial role. We observed that a group of pro-inflammatory cytokines, interleukin 6 (IL6), interleukin 1-beta (IL1b), and tumour necrosis factor-alpha (TNFa), preferentially activated genes exhibiting a high basal methylation level at their transcription start sites, in the human breast cancer cell line MCF7. In human breast tumours, these responding genes were also hypermethylated, and some of them (N = 104) were differentially methylated across human breast tumour samples (The Cancer Genome Atlas cohort). While their expression was positively correlated with the stromal content of the tumours and the expression of stromal-associated pro-inflammatory cytokines, the expression of this subset of genes was negatively correlated with their methylation level at their 5' end. Nevertheless, while the methylation level of this subset of genes was not correlated with the stromal cell content of the tumours, this negative correlation was partially lost in tumours with high stromal cell content. Consistently, we observed that the methylation level in this subset of genes influenced the correlation between gene expression and stromal cell content. Thus, these data indicated that the stromal component of breast tumours should be taken into account for DNA methylation and gene expression studies and suggest an additional pathway, via DNA methylation, in the cross-talk between cancer cells and their microenvironment in human breast cancers.

The Adipose Stem Cell as a Novel Metabolic Actor in Adrenocortical Carcinoma Progression: Evidence from an In Vitro Tumor Microenvironment Crosstalk Model

Metabolic interplay between the tumor microenvironment and cancer cells is a potential target for novel anti-cancer approaches. Among stromal components, adipocytes and adipose precursors have been shown to actively participate in tumor progression in several solid malignancies. In adrenocortical carcinoma (ACC), a rare endocrine neoplasia with a poor prognosis, cancer cells often infiltrate the fat mass surrounding the adrenal organ, enabling possible crosstalk with the adipose cells. Here, by using an in vitro co-culture system, we show that the interaction between adipose-derived stem cells (ASCs) and the adrenocortical cancer cell line H295R leads to metabolic and functional reprogramming of both cell types: cancer cells limit differentiation and increase proliferation of ASCs, which in turn support tumor growth and invasion. This effect associates with a shift from the paracrine cancer-promoting IGF2 axis towards an ASC-associated leptin axis, along with a shift in the SDF-1 axis towards CXCR7 expression in H295R cells. In conclusion, our findings suggest that adipose precursors, as pivotal components of the ACC microenvironment, promote cancer cell reprogramming and invasion, opening new perspectives for the development of more effective therapeutic approaches.

Phosphodiesterase 5 (PDE5) Is Highly Expressed in Cancer-Associated Fibroblasts and Enhances Breast Tumor Progression

The overexpression of phosphodiesterase (PDE) 5 is frequently found in various human cancers, such as those of the breast. However, PDE5’s role in the tumor microenvironment is still unknown. As PDE5 represents a high-value therapeutic target, we investigated whether the expression and function of PDE5 in breast cancer-associated fibroblasts (CAFs) may be clinically relevant to malignant progression. PDE5 expression was increased in human breast cancer stroma compared with normal stroma and was correlated to a shorter overall survival. Treatment of CAFs, isolated from breast tumor biopsies, with selective PDE5 inhibitors inhibited their proliferation, motility, and invasiveness, and negatively controlled tumor–stroma interactions in both ‘in vitro’ and ‘in vivo’ models. PDE5 stable overexpression transformed immortalized mouse embryonic fibroblasts (MEFs) towards an activated fibroblast phenotype, impacting their intrinsic characteristics and paracrine effects on breast cancer cell growth and migration through an enhanced production of the C-X-C motif chemokine 16 (CXCL16). On the other hand, CAF exposure to PDE5 inhibitors was associated with reduced CXCL16 expression and secretion. Importantly, CXCL16 levels in breast cancer stroma showed a strong correlation with PDE5 levels and poor patient outcomes. In conclusion, PDE5 is overexpressed in breast cancer stroma, enhances the tumor-stimulatory activities of fibroblasts, and impacts clinical outcomes; thus, we propose this enzyme as an attractive candidate for prognosis and a potential target for treatments in breast cancer patients.

The weight of obesity in breast cancer progression and metastasis: Clinical and molecular perspectives

The escalating epidemic of overweight and obesity is currently recognized as one of the most significant health and economic concern worldwide. At the present time, over 1.9 billion adults and more than 600 million people can be, respectively, classified as overweight or obese, and numbers will continue to increase in the coming decades. This alarming scenario implies important clinical implications since excessive adiposity can progressively cause and/or exacerbate a wide spectrum of co-morbidities, including type 2 diabetes mellitus, hypertension, cardiovascular disease, and even certain types of cancer, including breast cancer. Indeed, pathological remodelling of white adipose tissue and increased levels of fat-specific cytokines (mainly leptin), as a consequence of the obesity condition, have been associated with several hallmarks of breast cancer, such as sustained proliferative signaling, cellular energetics, inflammation, angiogenesis, activating invasion and metastasis. Different preclinical and clinical data have provided evidence indicating that obesity may worsen the incidence, the severity, and the mortality of breast cancer. In the present review, we will discuss the epidemiological connection between obesity and breast cancer progression and metastasis and we will highlight the candidate players involved in this dangerous relationship. Since the major cause of death from cancer is due to widespread metastases, understanding these complex mechanisms will provide insights for establishing new therapeutic interventions to prevent/blunt the effects of obesity and thwart breast tumor progression and metastatic growth.

Key Role of Obesity in Genitourinary Tumors with Emphasis on Urothelial and Prostate Cancers

Background: In human populations, a certain amount of data correlate obesity/body mass index (BMI) with urothelial cancer (UC) and prostate cancer (PCa) occurrence, however this is not fully elucidated at all stages of disease. In an attempt to shed light on uncertain areas in such field, in the present review we illustrate the main molecular mechanisms linking obesity and cancer, focusing on the correlation between obesity and tumor risk, disease progression and response to chemo- and immunotherapy in patients with UC and the predictive/prognostic role of obesity in PCa patients treated with the currently available therapeutic approaches. Methods: We did a large-scale literature search on existing scientific websites focusing on keywords "obesity", "body mass index (BMI)", "urothelial cancer", "prostate cancer", "docetaxel", "cabazitaxel", "abiraterone acetate", "enzalutamide", and "radium223". Results: Many adipocytes-induced molecules support tumor proliferation through activation of various cellular pathways. The available evidence in the postoperative setting do the role of BMI in oncological outcomes prediction still not completely clear. Likewise, in metastatic UC patients controversial results link the role of obesity/BMI with clinical outcomes of tumor response to chemotherapy. Adipose stromal cells recruitment, induced by PCa cells, from white adipose tissue to the tumor sites inducing cell invasiveness was associated with poor survival. Conflicting data, although more oriented towards a better survival outcome, resulted in obese patients treated with docetaxel. In PCa cell-lines a certain cabazitaxel chemo resistance adipose stromal cells (ASC)-mediated was demonstrated. In metastatic castration-resistant PCa patients with high BMI (>25 kg/m2) receiving abiraterone acetate there were significant worse survival outcomes, while in enzalutamide patients BMI did not affect survival outcome. In radium 223 patients higher BMI significantly correlated with favorable overall survival. Conclusions: The main focus of this review was to understand the interplay between obesity/BMI and UC/PCa. Several pathogenic cellular pathways exploring the issue are discussed, opening the way to challenging tailored treatments on the basis of BMI. Improving the knowledge of molecular connections between obesity and UC and PCa could favor the development of new therapies likely reducing chemo- and immunotherapy drug resistance.

Obesity and Breast Cancer: Role of Leptin

Obesity-related breast cancer is an important threat that affects especially post-menopausal women. The link between obesity and breast cancer seems to be relying on the microenvironment generated at adipose tissue level, which includes inflammatory cytokines. In addition, its association with systemic endocrine changes, including hyperinsulinemia, increased estrogens levels, and hyperleptinemia may be key factors for tumor development. These factors may promote tumor initiation, tumor primary growth, tissue invasion, and metastatic progression. Although the relationship between obesity and breast cancer is already established, the different pathophysiological mechanisms involved are not clear. Obesity-related insulin resistance is a well-known risk factor for breast cancer development in post-menopausal women. However, the role of inflammation and other adipokines, especially leptin, is less studied. Leptin, like insulin, appears to be a growth factor for breast cancer cells. There exists a link between leptin and metabolism of estrogens and between leptin and other factors in a more complex network. As a result, obesity-associated hyperleptinemia has been suggested as an important mediator in the pathophysiology of breast cancer. On the other hand, recent data on the paradoxical effect of obesity on cancer immunotherapy efficacy has brought some controversy, since the proinflammatory effect of leptin may help the effect of immune checkpoint inhibitors. Therefore, a better knowledge of the molecular mechanisms that mediate leptin action may be helpful to understand the underlying processes which link obesity to breast cancer in post-menopausal women, as well as the possible role of leptin in the response to immunotherapy in obese patients.

Leptin Modulates Exosome Biogenesis in Breast Cancer Cells: An Additional Mechanism in Cell-to-Cell Communication

Exosomes—small membrane vesicles secreted by both normal and malignant cells upon fusion of endosomal multivesicular bodies (MVBs) with the plasma membrane—play an important role in cell-to-cell communication. During the last decade, several reports have highlighted the involvement of these nanovesicles in many aspects of breast cancer development and progression, but the extracellular signals governing their generation in breast cancer cells have not been completely unraveled. Here, we investigated the role of the obesity hormone leptin, a well-known adipokine implicated in mammary tumorigenesis, on the mechanisms regulating exosome biogenesis and release in both estrogen receptor α (ERα)—positive MCF-7 and triple-negative MDA-MB-231 breast cancer cells. We found that leptin treatment enhanced the number of MVBs in the cytoplasm of breast cancer cells and increased the amount of exosomes released in cell conditioned media. At molecular level, leptin increased the protein expression of Tsg101—a key component of the endosomal sorting complex required for transport I (ESCRT-I)—by a post-transcriptional mechanism involving its direct interaction with the chaperone protein Hsp90. Targeting leptin signaling, by a selective leptin receptor antagonist the peptide LDFI (Leu-Asp-Phe-Ile), abrogated leptin effects on Tsg101 expression and on exosome secretion in breast cancer cells. In conclusion, our findings, identifying for the first time leptin/leptin receptor/Hsp90 axis as an important regulator of exosome generation in mammary carcinoma cells, suggest that targeting this signaling pathway might represent a novel therapeutic strategy to impair exosome secretion and interrupt the dangerous cell-to-cell communication in breast cancer.

The Emerging Role of Adiponectin in Female Malignancies

Obesity, characterized by excess body weight, is now accepted as a hazardous health condition and an oncogenic factor. In different epidemiological studies obesity has been described as a risk factor in several malignancies. Some biological mechanisms that orchestrate obesity-cancer interaction have been discovered, although others are still not completely understood. The unbalanced secretion of biomolecules, called "adipokines", released by adipocytes strongly influences obesity-related cancer development. Among these adipokines, adiponectin exerts a critical role. Physiologically adiponectin governs glucose levels and lipid metabolism and is fundamental in the reproductive system. Low adiponectin circulating levels have been found in obese patients, in which its protective effects were lost. In this review, we summarize the epidemiological, in vivo and in vitro data in order to highlight how adiponectin may affect obesity-associated female cancers.

The Nutritional Cytokine Leptin Promotes NSCLC by Activating the PI3K/AKT and MAPK/ERK Pathways in NSCLC Cells in a Paracrine Manner

Purpose

Leptin is a nutritional cytokine encoded by the obesity gene whose concentration in the tumor microenvironment is closely related to the occurrence and progression of cancer. However, previous evidence has suggested that there is no clear relationship between serum leptin concentrations and lung cancer progression. Cancer-associated fibroblasts (CAFs), the most abundant component of the tumor microenvironment in a variety of solid tumors, were recently reported to produce leptin. Therefore, it was inferred that leptin is most likely to affect non-small-cell lung cancer (NSCLC) through an autocrine and paracrine mechanism. In the current study, we investigated the paracrine effect and mechanism of leptin produced by CAFs on NSCLC by establishing a novel in vitro cell coculture system.

Methods

A noncontact coculture device was designed and made by 3D printing. CAFs and paired normal lung fibroblasts (NLFs) from 5 patients were successfully isolated and cocultured with two NSCLC cell lines in a coculture system. The background expression of leptin was detected by western blot. The in situ expression of leptin and its receptor (Ob-R) in NSCLC tissues and paired normal lung tissues was analyzed by immunohistochemistry. Furthermore, we downregulated the expression of leptin in CAFs and assessed changes in its promotion on NSCLC cells in the coculture system. Finally, changes in the phosphorylation of ERK1/2 and AKT were examined to investigate the molecular mechanisms responsible for the paracrine promotion of NSCLC cells by leptin.

Results

Leptin was overexpressed in nearly all five primary CAF lines compared with its expression in paired NLFs. IHC staining showed that the expression of leptin was high in NSCLC cells, slightly lower in CAF, and negative in normal lung tissue. Ob-R was strongly expressed in NSCLC cells. The ability of A549 and H1299 cells to proliferate and migrate was enhanced by high leptin levels in both the cocultured fibroblasts and the culture medium. Furthermore, western blot assays suggested that the MAPK/ERK1/2 and PI3K/AKT signaling pathways were activated by leptin produced by CAFs, which demonstrated that the functions of paracrine leptin in NSCLC are as those of the serum leptin to other cancers.

Conclusion

Leptin produced by CAF promotes proliferation and migration of NSCLC cells probably via PI3K/AKT and MAPK/ERK1/2 signaling pathways in a paracrine manner.

Obesity, Leptin and Breast Cancer: Epidemiological Evidence and Proposed Mechanisms

The prevalence of obesity has been steadily increasing over the past few decades in several developed and developing countries, with resultant hazardous health implications. Substantial epidemiological evidence has shown that excessive adiposity strongly influences risk, prognosis, and progression of various malignancies, including breast cancer. Indeed, it is now well recognized that obesity is a complex physiologic state associated with multiple molecular changes capable of modulating the behavior of breast tumor cells as well of the surrounding microenvironment. Particularly, insulin resistance, hyperactivation of insulin-like growth factor pathways, and increased levels of estrogen due to aromatization by the adipose tissue, inflammatory cytokines, and adipokines contribute to breast cancerogenesis. Among adipokines, leptin, whose circulating levels increase proportionally to total adipose tissue mass, has been identified as a key member of the molecular network in obesity. This review summarizes the current knowledge on the epidemiological link existing between obesity and breast cancer and outlines the molecular mechanisms underlying this connection. The multifaceted role of the obesity adipokine leptin in this respect is also discussed.

Activation of antioxidant defences of human mammary epithelial cells under leptin depend on neoplastic state

BACKGROUND

Obesity is associated with oxidative stress, a major factor in carcinogenesis, and with high leptin concentration. The aim of this study was to determine the effects of leptin on the antioxidant response in three human mammary epithelial cells each presenting a different neoplastic status: healthy human mammary epithelial cells (HMEC), oestrogen-receptor positive MCF-7 cells and triple-negative MDA-MB-231 cells.

METHODS

This in vitro kinetic study characterized the cell antioxidant response after 1, 6 and 24 h in the presence of leptin (10 or 100 ng/ml).The antioxidant response was defined in terms of cell glutathione content, gene expression and catalytic activity of antioxidant enzymes (i.e. glutathione peroxidase 1 (Gpx1), glutathione reductase (GR), glutathione S transferase (GST), heme-oxygenase 1 (HO-1) and cyclooxygenase-2 (COX-2)). Oxidative stress occurrence was assessed by lipid hydro peroxide (HPLIP) and isoprostane concentrations in culture media at 24 h.

RESULTS

At both concentrations used, leptin induced ROS production in all cell models, contributing to various antioxidant responses linked to neoplastic cell status. HMEC developed a highly inducible antioxidant response based on antioxidant enzyme activation and an increase in cell GSH content at 10 ng/ml of leptin. However, at 100 ng/ml of leptin, activation of antioxidant response was lower. Conversely, in tumour cells, MCF-7 and MDA-MB-231, leptin did not induce an efficient antioxidant response, at either concentration, resulting in an increase of lipid peroxidation products.

CONCLUSIONS

Leptin can modulate the oxidative status of mammary epithelial cells differently according to their neoplastic state. These novel results shed light on oxidative status changes in mammary cells in the presence of leptin.

Adipocyte-derived IL-6 and leptin promote breast Cancer metastasis via upregulation of Lysyl Hydroxylase-2 expression

BACKGROUND

Adipocytes make up the major component of breast tissue, accounting for 90% of stromal tissue. Thus, the crosstalk between adipocytes and breast cancer cells may play a critical role in cancer progression. Adipocyte-breast cancer interactions have been considered important for the promotion of breast cancer metastasis. However, the specific mechanisms underlying these interactions are unclear. In this study, we investigated the mechanisms of adipocyte-mediated breast cancer metastasis.

METHODS

Breast cancer cells were cocultured with mature adipocytes for migration and 3D matrix invasion assays. Next, lentivirus-mediated loss-of-function experiments were used to explore the function of lysyl hydroxylase (PLOD2) in breast cancer migration and adipocyte-dependent migration of breast cancer cells. The role of PLOD2 in breast cancer metastasis was further confirmed using orthotopic mammary fat pad xenografts in vivo. Clinical samples were used to confirm that PLOD2 expression is increased in tumor tissue and is associated with poor prognosis of breast cancer patients. Cells were treated with cytokines and pharmacological inhibitors in order to verify which adipokines were responsible for activation of PLOD2 expression and which signaling pathways were activated in vitro.

RESULTS

Gene expression profiling and Western blotting analyses revealed that PLOD2 was upregulated in breast cancer cells following coculture with adipocytes; this process was accompanied by enhanced breast cancer cell migration and invasion. Loss-of-function studies indicated that PLOD2 knockdown suppressed cell migration and disrupted the formation of actin stress fibers in breast cancer cells and abrogated the migration induced by following coculture with adipocytes. Moreover, experiments performed in orthotopic mammary fat pad xenografts showed that PLOD2 knockdown could reduce metastasis to the lung and liver. Further, high PLOD2 expression correlated with poor prognosis of breast cancer patients. Mechanistically, adipocyte-derived interleukin-6 (IL-6) and leptin may facilitate PLOD2 upregulation in breast cancer cells and promote breast cancer metastasis in tail vein metastasis assays. Further investigation revealed that adipocyte-derived IL-6 and leptin promoted PLOD2 expression through activation of the JAK/STAT3 and PI3K/AKT signaling pathways.

CONCLUSIONS

Our study reveals that adipocyte-derived IL-6 and leptin promote PLOD2 expression by activating the JAK/STAT3 and PI3K/AKT signaling pathways, thus promoting breast cancer metastasis.

Leptin impairs the therapeutic effect of ionizing radiation in oral squamous cell carcinoma cells

PURPOSE

Leptin, an important hormone controlling energy homeostasis, has been linked to the pathogenesis of oral squamous cell carcinoma (OSCC). Evidence indicates that head and neck cancer patients undergoing radiotherapy show decreased leptin levels after radiotherapy treatment. Thus, we investigated, through phenotypic and molecular analyses, whether leptin can compromise the therapeutic effect of ionizing radiation and neoplastic behavior of OSCC cells.

METHODS

The human OSCC-derived cell lines SCC9 and SCC4 were treated with human recombinant leptin and exposed to 6 Gy of irradiation. We performed the in vitro assays of cell migration, death, proliferation, and colony-forming ability. The reactive oxygen species (ROS) levels and proteome analysis by mass spectrometry were also conducted.

RESULTS

Leptin was able to increase cell proliferation, migration, and colony-forming ability, despite the suppressive effect induced by irradiation. Furthermore, the leptin promoted a significant reduction of ROS intracellular accumulation, and increased expression of the cancer-related proteins, as ACTC1, KRT6A, and EEF2 in irradiated OSCC cells.

CONCLUSIONS

Our findings suggest that leptin impairs responsivity of OSCC cells to the ionizing radiation, reducing the suppressive effects of irradiation on the neoplastic phenotype, and increasing protein expression critical to carcinogenesis.

The Impact of ESR1 Mutations on the Treatment of Metastatic Breast Cancer

After nearly 20 years of research, it is now established that mutations within the estrogen receptor (ER) gene, ESR1, frequently occur in metastatic breast cancer and influence response to hormone therapy. Though early studies presented differing results, sensitive sequencing techniques now show that ESR1 mutations occur at a frequency between 20 and 40% depending on the assay method. Recent studies have focused on several "hot spot mutations," a cluster of mutations found in the hormone-binding domain of the ESR1 gene. Throughout the course of treatment, tumor evolution can occur, and ESR1 mutations emerge and become enriched in the metastatic setting. Sensitive techniques to continually monitor mutant burden in vivo are needed to effectively treat patients with mutant ESR1. The full impact of these mutations on tumor response to different therapies remains to be determined. However, recent studies indicate that mutant-bearing tumors may be less responsive to specific hormonal therapies, and suggest that aromatase inhibitor (AI) therapy may select for the emergence of ESR1 mutations. Additionally, different mutations may respond discretely to targeted therapies. The need for more preclinical mechanistic studies on ESR1 mutations and the development of better agents to target these mutations are urgently needed. In the future, sequential monitoring of ESR1 mutational status will likely direct personalized therapeutic regimens appropriate to each tumor's unique mutational landscape.

Ligand-activated PPARγ downregulates CXCR4 gene expression through a novel identified PPAR response element and inhibits breast cancer progression

Stromal Derived Factor-1α (SDF-1α) and its cognate receptor CXCR4 play a key role in mediating breast cancer cell invasion and metastasis. Therefore, drugs able to inhibit CXCR4 activation may add critical tools to reduce tumor progression, especially in the most aggressive form of the breast cancer disease. Peroxisome Proliferator-Activated Receptor (PPAR) γ, a member of the nuclear receptor superfamily, has been found to downregulate CXCR4 gene expression in different cancer cells, however the molecular mechanism underlying this effect is not fully understood. Here, we identified a novel PPARγ-mediated mechanism that negatively regulates CXCR4 expression in both epithelial and stromal breast cancer cells. We found that ligand-activated PPARγ downregulated CXCR4 transcriptional activity through the recruitment of the silencing mediator of retinoid and thyroid hormone receptor (SMRT) corepressor onto a newly identified PPAR response element (PPRE) within the CXCR4 promoter in breast cancer cell lines. As a consequence, the PPARγ agonist rosiglitazone (BRL) significantly inhibited cell migration and invasion and this effect was PPARγ-mediated, since it was reversed in the presence of the PPARγ antagonist GW9662. According to the ability of cancer-associated fibroblasts (CAFs), the most abundant component of breast cancer stroma, to secrete high levels of SDF-1α, BRL reduced migratory promoting activities induced by conditioned media (CM) derived from CAFs and affected CXCR4 downstream signaling pathways activated by CAF-CM. In addition, CAFs exposed to BRL showed a decreased expression of CXCR4, a reduced motility and invasion along with a phenotype characterized by an altered morphology. Collectively, our findings provide novel insights into the role of PPARγ in inhibiting breast cancer progression and further highlight the utility of PPARγ ligands for future therapies aimed at targeting both cancer and surrounding stromal cells in breast cancer patients.

Targeting Metabolic Cross Talk between Cancer Cells and Cancer-Associated Fibroblasts

Although tumorigenesis has classically been regarded as a genetic disease of uncontrolled cell growth, the importance of the tumor microenvironment (TME) is continuously emphasized by the accumulating evidence that cancer growth is not simply dependent on the cancer cells themselves [1, 2] but also dependent on angiogenesis [3–6], inflammation [7, 8], and the supporting roles of cancer-associated fibroblasts (CAFs) [9, 10]. After the discovery that CAFs are able to remodel the tumor matrix within the TME and provide the nutrients and chemicals to promote cancer cell growth [11], many studies have aimed to uncover the cross talk between cancer and CAFs. Moreover, a new paradigm in cancer metabolism shows how cancer cells act like “metabolic parasites” to uptake the high-energy metabolites, such as lactate, ketone bodies, free fatty acid, and glutamine from supporting cells, including CAFs and cancer-associated adipocytes (CAAs) [12, 13]. This chapter provides an overview of the metabolic coupling between CAFs and cancer to further define the therapeutic options to disrupt the CAF-cancer cell interactions.

The roles of tricellular tight junction protein lipolysis-stimulated lipoprotein receptor in malignancy of human endometrial cancer cells

Lipolysis-stimulated lipoprotein receptor (LSR) has been identified as a novel molecular constituent of tricellular contacts that have a barrier function for the cellular sheet. LSR recruits tricellulin (TRIC), which is the first molecular component of tricellular tight junctions. Knockdown of LSR increases cell motility and invasion of certain cancer cells. However, the behavior and the roles of LSR in endometrial cancer remain unknown. In the present study, we investigated the behavior and roles of LSR in normal and endometrial cancer cells in vivo and in vitro. In endometriosis and endometrial cancer, LSR was observed not only in the subapical region but also throughout the lateral region as well as in normal endometrial epithelial cells in the secretory phase, and LSR in the cancer was reduced in correlation with the malignancy. Knockdown of LSR by the siRNA in cells of the endometrial cancer cell line Sawano, induced cell migration, invasion and proliferation, while TRIC relocalized from the tricellular region to the bicellular region at the membrane. In Sawano cells and normal HEEs, a decrease of LSR induced by leptin and an increase of LSR induced by adiponectin and the drugs for type 2 diabetes metformin and berberine were observed via distinct signaling pathways including JAK2/STAT. In Sawano cells, metformin and berberine prevented cell migration and invasion induced by downregulation of LSR by the siRNA and leptin treatment. The dissection of the mechanism in the downregulation of endometrial LSR during obesity is important in developing new diagnostic and therapy for endometrial cancer.

DNA methylation signal has a major role in the response of human breast cancer cells to the microenvironment

Breast cancer-associated fibroblasts (CAFs) have a crucial role in tumor initiation, metastasis and therapeutic resistance by secreting various growth factors, cytokines, protease and extracellular matrix components. Soluble factors secreted by CAFs are involved in many pathways including inflammation, metabolism, proliferation and epigenetic modulation, suggesting that CAF-dependent reprograming of cancer cells affects a large set of genes. This paracrine signaling has an important role in tumor progression, thus deciphering some of these processes could lead to relevant discoveries with subsequent clinical implications. Here, we investigated the mechanisms underlying the changes in gene expression patterns associated with the cross-talk between breast cancer cells and the stroma. From RNAseq data obtained from breast cancer cell lines grown in presence of CAF-secreted factors, we identified 372 upregulated genes, exhibiting an expression level positively correlated with the stromal content of breast cancer specimens. Furthermore, we observed that gene expression changes were not mediated through significant DNA methylation changes. Nevertheless, CAF-secreted factors but also stromal content of the tumors remarkably activated specific genes characterized by a DNA methylation pattern: hypermethylation at transcription start site and shore regions. Experimental approaches (inhibition of DNA methylation, knockdown of methyl-CpG-binding domain protein 2 and chromatin immunoprecipitation assays) indicated that this set of genes was epigenetically controlled. These data elucidate the importance of epigenetics marks in the cancer cell reprogramming induced by stromal cell and indicated that the interpreters of the DNA methylation signal have a major role in the response of the cancer cells to the microenvironment.

Superactive human leptin antagonist (SHLA), triple Lan1 and quadruple Lan2 leptin mutein as a promising treatment for human folliculoma

PURPOSE

There are no data showing a direct correlation between obesity and increased blood leptin levels with folliculoma. Moreover, folliculoma is not the best studied among other ovarian cancer types. We investigated whether oestradiol can modulate ObR expression in some oestrogen-responsive tissues and that leptin exerts its activity not only via the leptin receptor but also through cross talk with other signalling systems. We hypothesise that blocking ObR expression could be a novel treatment for gonadal ovarian cancer.

METHODS

We evaluated the effect of SHLA, Lan1 and Lan2 blockers on cell proliferation (BrdU incorporation assay), ObR and ERα/β gene expression (qPCR), oestradiol secretion (ELISA) and cell cycle protein expression (Western blot) in the non-cancerous cell line HGrC1 and two granulosa cancer cell lines: the juvenile form (COV434) and the adult form (KGN).

RESULTS

ObR gene expression in cancer cell lines was 50% higher than in the non-cancer cells. Lan-1 and Lan-2 decreased ObR expression in COV434, while it had no effect in KGN cells. Higher ERβ expression in non-cancer and higher ERα expression in both cancer cell lines was noted. SHLA and Lan-1 changed the ratio towards greater expression of ERβ, characteristic of non-cancer granulosa cells. All ObR antagonists in HCrC1 and KGN but only Lan-2 in COV434 reversed leptin-stimulated proliferation. In both non-cancer and cancer granulosa cells, leptin acts as a cyclinD/cdk4, cyclin A/cdk2 and E2F inhibitor.

CONCLUSION

These results indicate that SHLA and Lan2 are promising leptin receptor inhibitors that can eliminate the negative effects of leptin. These compounds should be considered in further ex vivo studies on the cancer microenvironment.

STAT3 activation by leptin receptor is essential for TNBC stem cell maintenance

Leptin (LEP) binds to the long form of the leptin receptor (LEPRb), leading to the activation of multiple signaling pathways that are potential targets for disrupting the obesity-breast cancer link. In triple-negative breast cancer (TNBC), LEP is hypothesized to predominantly mediate its tumorigenic effects via a subpopulation of LEPRb-positive tumor cells termed cancer stem cells (CSCs) that can initiate tumors and induce tumor progression. Previously, we showed that LEP promotes CSC survival in vivo Moreover, silencing LEPRb in TNBC cells compromised the CSC state. The mechanisms by which LEPRb regulates TNBC CSC intracellular signaling are not clear. We hypothesized that activation of LEPRb signaling is sufficient to drive CSC maintenance in TNBC. Here, we show that activation of LEPRb in non-CSCs isolated using our CSC reporter system resulted in a transition to the stem cell state. In CSCs, LEP induced STAT3 phosphorylation, whereas LEP did not induce STAT3 phosphorylation in non-CSCs. Introduction of constitutively active STAT3 into LEPRb-transfected non-CSCs significantly induced NANOG, SOX2 and OCT4 expression compared with control non-CSCs. To determine the intracellular phospho-tyrosine residue of LEPRb that is necessary for the induction of the stem cell state in non-CSCs, we transfected the tyrosine residue point mutants L985, F1077 and S1138 into non-CSCs. Non-CSCs transfected with the L985 mutant exhibited increased STAT3 phosphorylation, increased SOCS3 expression and an induction of GFP expression compared with non-CSCs expressing the F1077 and S1138 mutants. Our data demonstrate that LEPRb-induced STAT3 activation is essential for the induction and maintenance of TNBC CSCs.

Metastasis of breast cancer cells to the bone, lung, and lymph nodes promotes resistance to ionizing radiation

BACKGROUND

Metastasis represents the leading cause of breast cancer deaths, necessitating strategies for its treatment. Although radiotherapy is employed for both primary and metastatic breast cancers, the difference in their ionizing radiation response remains incompletely understood. This study is the first to compare the radioresponse of a breast cancer cell line with its metastatic variants and report that such metastatic variants are more radioresistant.

MATERIALS AND METHODS

A luciferase expressing cell line was established from human basal-like breast adenocarcinoma MDA-MB-231 and underwent in vivo selections, whereby a cycle of inoculations into the left cardiac ventricle or the mammary fat pad of athymic nude mice, isolation of metastases to the bone, lung and lymph nodes visualized with bioluminescence imaging, and expansion of obtained cells was repeated twice or three times. The established metastatic cell lines were assessed for cell proliferation, wound healing, invasion, clonogenic survival, and apoptosis.

RESULTS

The established metastatic cell lines possessed an increased proliferative potential in vivo and were more chemotactic, invasive, and resistant to X‑ray-induced clonogenic inactivation and apoptosis in vitro.

CONCLUSION

Breast cancer metastasis to the bone, lung, and lymph nodes promotes radioresistance.

Leptin signals via TGFB1 to promote metastatic potential and stemness in breast cancer

Epidemiological studies have shown obesity to be linked with poorer outcomes in breast cancer patients. The molecular mechanisms responsible for the increased risk of invasive/metastatic disease with obesity are complex, but may include elevated levels of adipokines such as leptin. Using physiological levels of leptin found in obesity in a novel chronic in vitro treatment model (≤200 ng/ml for 14 days), we confirmed the occurrence of leptin-mediated changes in growth, apoptosis and metastatic behavior, and gene expression changes representing epithelial-to-mesenchymal transition (EMT) and a cancer stem cell (CSC) like phenotype in breast epithelial and cancer cell lines (MCF10A, MCF10AT1, MCF7 and MDA-MB-231). Further, we have discovered that these effects were accompanied by increased expression of TGFB1, and could be significantly reduced by co-treatment with neutralizing antibody against TGFB1, indicating that the induction of these characteristics was mediated via TGFB1. Occurring in both MCF7 and MCF10AT1 cells, it suggests these actions of leptin to be independent of estrogen receptor status. By linking leptin signalling to the established TGFB1 pathway of metastasis / EMT, this study gives a direct mechanism by which leptin can contribute to the poorer outcomes of obese cancer patients. Inhibitors of TGFB1 are in currently in phase III clinical trials in other malignancies, thus identifying the connection between leptin and TGFB1 will open new therapeutic opportunities for improving outcomes for obese breast cancer patients.

The Spatial Relationship of Malignant and Benign Breast Lesions with Respect to the Fat-Gland Interface on Magnetic Resonance Imaging

The fat-gland interface in the breast is noteworthy in that major vessels and lymphatic channels supplying the breast are located there; however, the relationship between breast lesion formation and the fat-gland interface is poorly understood. Here we evaluate the location of malignant and benign breast lesions with respect to the fat-gland interface in 881 women 50 years of age and younger, utilizing MR imaging. We find that most breast lesions are located in or near the interface in qualitative (89.7%) and quantitative (90.0%, 1 cm within the interface) analyses. This propensity for the fat-gland interface is not accounted for by breast anatomy, whereby 12.3% and 55.7% of breast volume is within 2 mm and 1 cm of the interface, respectively. Malignant lesions were located in or near the interface in significantly higher proportions than benign lesions in qualitative (94.3% vs. 67.3%, P < 0.001) and quantitative (49.7% vs. 34.5%, P < 0.001, 2 mm within the interface) analyses. This phenomenon may reflect a biological importance of the fat-gland interface in breast cancer development and progression.

Leptin as a mediator of tumor-stromal interactions promotes breast cancer stem cell activity

Breast cancer stem cells (BCSCs) play crucial roles in tumor initiation, metastasis and therapeutic resistance. A strict dependency between BCSCs and stromal cell components of tumor microenvironment exists. Thus, novel therapeutic strategies aimed to target the crosstalk between activated microenvironment and BCSCs have the potential to improve clinical outcome. Here, we investigated how leptin, as a mediator of tumor-stromal interactions, may affect BCSC activity using patient-derived samples (n = 16) and breast cancer cell lines, and determined the potential benefit of targeting leptin signaling in these model systems. Conditioned media (CM) from cancer-associated fibroblasts and breast adipocytes significantly increased mammosphere formation in breast cancer cells and depletion of leptin from CM completely abrogated this effect. Mammosphere cultures exhibited increased leptin receptor (OBR) expression and leptin exposure enhanced mammosphere formation. Microarray analyses revealed a similar expression profile of genes involved in stem cell biology among mammospheres treated with CM and leptin. Interestingly, leptin increased mammosphere formation in metastatic breast cancers and expression of OBR as well as HSP90, a target of leptin signaling, were directly correlated with mammosphere formation in metastatic samples (r = 0.68/p = 0.05; r = 0.71/p = 0.036, respectively). Kaplan-Meier survival curves indicated that OBR and HSP90 expression were associated with reduced overall survival in breast cancer patients (HR = 1.9/p = 0.022; HR = 2.2/p = 0.00017, respectively). Furthermore, blocking leptin signaling by using a full leptin receptor antagonist significantly reduced mammosphere formation in breast cancer cell lines and patient-derived samples. Our results suggest that leptin/leptin receptor signaling may represent a potential therapeutic target that can block the stromal-tumor interactions driving BCSC-mediated disease progression.

Hyperglycemia, tumorigenesis, and chronic inflammation

Hyperglycemia is the most prominent sign that characterizes diabetes. Hyperglycemia favors malignant cell growth by providing energy to cancer cells. Clinical studies also showed an increased risk of diabetes being associated with different types of cancers. In addition, poorly regulated glucose metabolism in diabetic patients is often found with increased levels of chronic inflammatory markers, e.g., interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, and emerging evidence has highlighted activation of the immune response in the progression and development of cancer cells. Therefore, uncontrolled proinflammatory responses could conceivably create a chronic inflammatory state, promoting a tumor-favorable microenvironment and potentially triggering immune overactivation and cancer growth. To further understand how hyperglycemia contributes to immune overactivation, the tumor microenvironment and the development of chronic inflammation-associated tumors may provide insights into tumor biology and immunology. This paper provides a brief introduction to hyperglycemia-associated diseases, followed by a comprehensive overview of the current findings of regulatory molecular mechanisms of glycosylation on proteoglycans in the extracellular matrix under hyperglycemic conditions. Then, the authors discuss the role of hyperglycemia in tumorigenesis (particularly in prostate, liver, colorectal, and pancreatic cancers), as well as the contribution of hyperglycemia to chronic inflammation. The authors end with a brief discussion on the future perspectives of hyperglycemia/tumorigenesis and potential applications of alternative/effective therapeutic strategies for hyperglycemia-associated cancers.