Leptin acts on neoplastic behavior and expression levels of genes related to hypoxia, angiogenesis, and invasiveness in oral squamous cell carcinoma

Assessment of salivary and serum leptin in tobacco smokers and oral squamous cell carcinoma-A case-control study

OBJECTIVES

Oral squamous cell carcinoma (OSCC) is the most common head and neck malignancy and tobacco-related cancers account for a significant portion of all oral cancers. Cancer patients often suffer from cachexia, which contributes significantly to mortality. Leptin is a protein released by adipocytes identified to play an important role in obesity and inflammation. The present study aimed to quantify and compare salivary and serum leptin in tobacco smokers and OSCC.

MATERIALS AND METHODS

The present prospective case-control study enrolled 42 subjects divided equally among OSCC and tobacco smokers without oral lesions (TS). Both saliva and blood were collected from each subject and leptin levels were determined using enzyme-linked immunosorbent assay. The data obtained were analysed using Mann Whitney U, Kruskal Wallis, Friedman, and Spearman correlation tests (p < 0.05).

RESULTS

A significant reduction in both salivary and serum leptin levels in OSCC was observed (p < 0.001, 0.002 respectively). In addition, significant reductions in weight and body mass index were also observed during follow-ups at 3, 6, and 9 months (p < 0.001 for both).

CONCLUSIONS

Reduced salivary and serum leptin levels in OSCC proved that it is an important diagnostic marker, with non-invasive saliva measurement being more patient-friendly. Future multicentric studies with higher samples in OSCC subgroups are warranted.

CLINICAL RELEVANCE

Leptin reduction in oral squamous cell carcinoma proved to be an important diagnostic marker. Non-invasive salivary techniques could be employed in mass screening programmes. The significant correlation between leptin and BMI also shed insight into the overall well-being of the patient.

The role of neck adipose tissue in lymph node metastasis of head and neck cancer

Previous studies indicated that adipose tissue significantly influences cancer invasion and lymphatic metastasis. However, the impact of neck adipose tissue (NAT) on lymph node metastasis associated with head and neck cancer remains ambiguous. Here, we systematically assess the classification and measurement criteria of NAT and evaluate the association of adipose tissue and cancer-associated adipocytes with head and neck cancer. We delve into the potential mechanisms by which NAT facilitate cervical lymph node metastasis in head and neck cancer, particularly through the secretion of adipokines such as leptin, adiponectin, and Interleukin-6. Our aim is to elucidate the role of NAT in the progression and metastasis of head and neck cancer, offering new insights into prevention and treatment.

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.

Obesity and cancer: focus on leptin

Over the past decades, obesity has grown to epidemic proportions worldwide. It has been associated with an increased risk for different types of cancer. In addition, obesity has been associated with a poor prognosis, an increased risk of metastasis and mortality, and resistance to anti-cancer therapies. The pathophysiological mechanisms underlying the obesity-cancer connection have not yet been fully elucidated. However, this connection could result, at least in part, from the action of adipokines, whose levels are increased in obesity. Among these adipokines, evidence suggests leptin's critical role in linking obesity to cancer. In this review, we first summarize the current state of the literature regarding the implication of leptin in tumorigenic processes. Next, we focus on the effects of leptin on the anti-tumor immune response. Then, we discuss the influence of leptin on the efficiency of antineoplastic treatments and the development of tumor resistance. Finally, we highlight the use of leptin as a potential target for the prevention and treatment of cancer.

Ras drives malignancy through stem cell crosstalk with the microenvironment

Squamous cell carcinomas are triggered by marked elevation of RAS-MAPK signalling and progression from benign papilloma to invasive malignancy1-4. At tumour-stromal interfaces, a subset of tumour-initiating progenitors, the cancer stem cells, obtain increased resistance to chemotherapy and immunotherapy along this pathway5,6. The distribution and changes in cancer stem cells during progression from a benign state to invasive squamous cell carcinoma remain unclear. Here we show in mice that, after oncogenic RAS activation, cancer stem cells rewire their gene expression program and trigger self-propelling, aberrant signalling crosstalk with their tissue microenvironment that drives their malignant progression. The non-genetic, dynamic cascade of intercellular exchanges involves downstream pathways that are often mutated in advanced metastatic squamous cell carcinomas with high mutational burden7. Coupling our clonal skin HRASG12V mouse model with single-cell transcriptomics, chromatin landscaping, lentiviral reporters and lineage tracing, we show that aberrant crosstalk between cancer stem cells and their microenvironment triggers angiogenesis and TGFβ signalling, creating conditions that are conducive for hijacking leptin and leptin receptor signalling, which in turn launches downstream phosphoinositide 3-kinase (PI3K)-AKT-mTOR signalling during the benign-to-malignant transition. By functionally examining each step in this pathway, we reveal how dynamic temporal crosstalk with the microenvironment orchestrated by the stem cells profoundly fuels this path to malignancy. These insights suggest broad implications for cancer therapeutics.

Leptin attenuates hypoxia-induced apoptosis in human periodontal ligament cells via the reactive oxygen species-hypoxia-inducible factor-1α pathway

NEW FINDINGS

What is the central question of this study? Does leptin have an effect on hypoxia-induced apoptosis in human periodontal ligament cells (hPDLCs), and what is the potential underlying mechanism? What is the main finding and its importance? Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of hypoxia-inducible factor-1α and accumulation of reactive oxygen species (ROS). Leptin shows feedback inhibition on hypoxia-induced ROS-mediated apoptosis in hPDLCs, suggesting a new application of leptin for hypoxic damage in periodontal diseases.

ABSTRACT

Hypoxia-induced apoptosis of human periodontal ligament cells (hPDLCs) is an important contributor to the progression of various periodontal diseases. Although leptin has been shown to protect connective tissue cells against hypoxia-induced injury, whether it might do so by attenuating hypoxia-induced apoptosis in hPDLCs remains unclear. Here, using CoCl₂ treatment, we simulated hypoxic conditions in hPDLCs and explored whether apoptosis and reactive oxygen species (ROS) levels were related to hypoxia. After small interfering RNA (siRNA) inhibition of leptin and hypoxia-inducible factor-1α (HIF-1α), the levels of apoptosis, ROS and leptin expression were measured. We showed that in CoCl₂ -treated hPDLCs, significantly higher cell apoptosis rates and ROS accumulation were observed. Cobalt chloride also increased leptin and HIF-1α expression in hPDLCs. Further investigation of the pathway demonstrated that inhibition of ROS attenuated hypoxia-induced cell apoptosis and leptin expression, whereas siRNA inhibition of leptin aggravated hypoxia-induced cell apoptosis and ROS accumulation. Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of ROS and HIF-1α pathways, and leptin shows feedback inhibition on ROS-mediated apoptosis in hPDLCs. These findings suggest a new application of leptin for hypoxic damage in periodontal diseases.

CircRNA-Mediated Regulation of Angiogenesis: A New Chapter in Cancer Biology

Angiogenesis is necessary for carcinoma progression and is regulated by a variety of pro- and anti-angiogenesis factors. CircRNAs are RNA molecules that do not have a 5'-cap or a 3'-polyA tail and are involved in a variety of biological functions. While circRNA-mediated regulation of tumor angiogenesis has received much attention, the detailed biological regulatory mechanism remains unclear. In this review, we investigated circRNAs in tumor angiogenesis from multiple perspectives, including its upstream and downstream factors. We believe that circRNAs have natural advantages and great potential for the diagnosis and treatment of tumors, which deserves further exploration.

Might anxiety disorders promote head and neck cancer development?

Cancer patients present a higher risk of experiencing anxiety disorders (AD). However, it is not clear if AD might be associated with cancer development. Thus, our study aimed to evaluate if AD might be related to head and neck squamous cell carcinoma (HNSCC) development. The combination of an applied animal basic study and a retrospective diagnostic case and control study in patients was performed. As a result, we obtained that stress reduced the locomotor activity of the animals in the group stress and stress + 4NqO (p < 0.0001). The stress showed no influence on the progression of neoplasia in mice. In the same way, the case group did not present differences in anxiety scores in comparison to control. Moreover, no association between HNSCC staging and anxiety scores was observed. In conclusion, our in vivo findings in humans and animals have shown that there is no relationship between AD and oral squamous cell carcinoma.

microRNAs Biogenesis, Functions and Role in Tumor Angiogenesis

microRNAs (miRNAs) are small non-coding RNA molecules, evolutionary conserved. They target more than one mRNAs, thus influencing multiple molecular pathways, but also mRNAs may bind to a variety of miRNAs, either simultaneously or in a context-dependent manner. miRNAs biogenesis, including miRNA transcription, processing by Drosha and Dicer, transportation, RISC biding, and miRNA decay, are finely controlled in space and time. miRNAs are critical regulators in various biological processes, such as differentiation, proliferation, apoptosis, and development in both health and disease. Their dysregulation is involved in tumor initiation and progression. In tumors, they can act as onco-miRNAs or oncosuppressor-miRNA participating in distinct cellular pathways, and the same miRNA can perform both activities depending on the context. In tumor progression, the angiogenic switch is fundamental. miRNAs derived from tumor cells, endothelial cells, and cells of the surrounding microenvironment regulate tumor angiogenesis, acting as pro-angiomiR or anti-angiomiR. In this review, we described miRNA biogenesis and function, and we update the non-classical aspects of them. The most recent role in the nucleus, as transcriptional gene regulators and the different mechanisms by which they could be dysregulated, in tumor initiation and progression, are treated. In particular, we describe the role of miRNAs in sprouting angiogenesis, vessel co-option, and vasculogenic mimicry. The role of miRNAs in lymphoma angiogenesis is also discussed despite the scarcity of data. The information presented in this review reveals the need to do much more to discover the complete miRNA network regulating angiogenesis, not only using high-throughput computational analysis approaches but also morphological ones.

Clinical - pathological significance of leptin receptor (LEPR) expression in squamous cell carcinoma of the skin

Adipokine leptin functions through its transmembrane receptors (LEPR). In many malignant tumors it stimulates the growth, migration and invasion of malignant cells. The aim of our work is to examine the effect of LEPR expression on the clinical-morphological properties of squamous cell carcinoma of the skin (cSCC). The biopsy material obtained by excision of squamous cell skin cancer was used. The test group consisted of excision biopsies of squamous cell carcinoma of the skin (n = 62), and the control group (n = 62) consisted of excision biopsies of non-tumor tissue of the skin (from the tumor environment) from an operative preparation delivered to the Pathohistology Department. After routine processing and paraffin molding, histochemical Hematoxylin-Eosin and immunohistochemical ABC method with anti LEPR and Ki67 antibodies were applied at 4 μm sections. The statistical software package SPSS for Windows (26.0) was used to analyze obtained results. Intracytoplasmic and intramembranous LEPR expression was found in 100 % of examined cSCCs. LEPR expression was statistically significantly associated with proliferation index and histologic grade of tumors. Pronounced LEPR expression was associated with a high proliferation index in 66.7 % of cases and with poorly differentiated cSCC in 94.4 %. Multivariate regression analysis showed that cSCCs with pronounced LEPR expression were seven times more often poorly differentiated than tumors with moderate or LEPR expression in trace. Our results indicate that LEPR expression is a predictor of the malignant potential of cSCC, so that based on LEPR expression, it is possible to identify an aggressive cSCC phenotype, which provides the possibility of individualizing anti-tumor treatment using LEPR antagonists.

Obesity: An emerging driver of head and neck cancer

Obesity has become pandemic and emerged as one of the most critical global health care problems worldwide since last century. Recent studies have demonstrated that there may be a causal link between obesity and higher risks and mortality of cancers, including prostate, breast, colon, and thyroid cancers, head and neck cancer (HNC). This review focuses on the relationship between obesity and HNC, and the molecular mechanism of abnormal lipid metabolism in HNC. Elucidating the mechanism may open up new possibilities for strategies to reduce risk and mortality of HNC in an increasingly obese population.

Leptin-induced signaling pathways in cancer cell migration and invasion

BACKGROUND

Increasing evidence indicates that obesity is associated with tumor development and progression. Leptin is an adipocyte-related hormone with a key role in energy metabolism and whose circulating levels are elevated in obesity. The effect of leptin on cancer progression and metastasis and its underlying mechanisms are still unclear. Leptin can impact various steps in tumor metastasis, including epithelial-mesenchymal transition, cell adhesion to the extracellular matrix (ECM), and proteolysis of ECM components. To do so, leptin binds to its receptor (OB-Rb) to activate signaling pathways and downstream effectors that participate in tumor cell invasion as well as distant metastasis.

CONCLUSIONS

In this review, we describe metastasis steps in detail and characterize metastasis-related molecules activated by leptin, which may help to develop a roadmap that guides future work. In addition, we conclude that a profound understanding of the fundamental molecular processes that contribute to leptin-induced metastasis may pave the way for the development of new prognostic molecules and appropriate approaches to the treatment of obesity-related cancers.

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.

MiR-873 inhibition enhances gefitinib resistance in non-small cell lung cancer cells by targeting glioma-associated oncogene homolog 1

BACKGROUND

The five-year survival rate of non-small cell lung cancer (NSCLC) patients is very low. MiR-873 is involved in the growth, metastasis, and differentiation of tumors. Herein, we determined the target gene and influence of miR-873 in NSCLC.

METHODS

MiRanda and Targetscan websites were used to predict the target gene of miR-873 in NSCLC. Luciferase activity was examined using a dual luciferase reporter gene assay kit. The viability, tube formation, and proliferation of cells were analyzed by cell counting kit-8, angiogenic analysis, and flow cytometry, respectively. The levels of miR-873 and GLI1 were evaluated using quantitative real-time PCR and Western blot assays.

RESULTS

Low levels of GLI1 and high levels of miR-873 were observed in an NSCLC cell line (PC9) highly sensitive to EGFR-tyrosine kinase inhibitors. There was a negative correlation between miR-873 and GLI1 expression in PC9 and PC9/GR cells. The inhibition of miR-873 enhanced GLI1 levels. MiR-873 expression was inhibited by gefitinib. Gefitinib markedly reduced the viability, tube formation, and cell number in PC9 cells. However, suppression of miR-873 enhanced the resistance and knockdown of GLI1 enhanced the sensitivity of PC9 cells to gefitinib.

CONCLUSIONS

GLI1 is a target gene of miR-873 in NSCLC. The inhibition of miR-873 increased gefitinib resistance of NSCLC cells via the upregulation of GLI1. These results indicate that miR-873-GLI1 signaling is involved in gefitinib resistance in NSCLC.

Leptin signaling axis specifically associates with clinical prognosis and is multifunctional in regulating cancer progression

Leptin is a peptide hormone that has been characterized as the ligand of leptin receptor (LEPR). The observation of leptin secretion and leptin receptor expression beyond the normal tissues suggests the potentially critical roles other than its physiological function. In addition to the original function in controlling appetite and energy expenditure, leptin-mediated signaling axis through leptin receptor is multifunctional which plays role in the regulation toward broad types of cancer. Emerging evidences has indicated leptin's function in promoting several processes which are relevant to cancer progression including cell proliferation, metastasis, angiogenesis and drug resistance. We relatively display leptin and leptin receptor expression levels in pan-cancer panel based on the transcriptome analysis via dataset The Cancer Genome Atlas (TCGA), and show the clinical association of the axis in predicting cancer prognosis. The results indicate the pathological impacts of this axis on many types of cancer. This review mainly focuses on leptin-mediated effects and its downstream signaling related to the progression of cancers, and displays the clinical significance of this axis including the impact on cancer patient survival.

The potential role of leptin in tumor invasion and metastasis

The adipocyte-released hormone-like cytokine/adipokine leptin behaves differently in obesity compared to its functions in the normal healthy state. In obese individuals, elevated leptin levels act as a pro-inflammatory adipokine and are associated with certain types of cancers. Further, a growing body of evidence suggests that higher circulating leptin concentrations and/or elevated expression of leptin receptors (Ob-R) in tumors may be poor prognostic factors. Although the underlying pathological mechanisms of leptin's association with poor prognosis are not clear, leptin can impact the tumor microenvironment in several ways. For example, leptin is associated with a number of biological components that could lead to tumor cell invasion and distant metastasis. This includes interactions with carcinoma-associated fibroblasts, tumor promoting effects of infiltrating macrophages, activation of matrix metalloproteinases, transforming growth factor-β signaling, etc. Recent studies also have shown that leptin plays a role in the epithelial-mesenchymal transition, an important phenomenon for cancer cell migration and/or metastasis. Furthermore, leptin's potentiating effects on insulin-like growth factor-I, epidermal growth factor receptor and HER2/neu have been reported. Regarding unfavorable prognosis, leptin has been shown to influence both adenocarcinomas and squamous cell carcinomas. Features of poor prognosis such as tumor invasion, lymph node involvement and distant metastasis have been recorded in several cancer types with higher levels of leptin and/or Ob-R. This review will describe the current scenario in a precise manner. In general, obesity indicates poor prognosis in cancer patients.