Irisin Association with Ki-67, MCM3 and MT-I/II in Squamous Cell Carcinomas of the Larynx

The Role of FNDC5/Irisin in Cardiovascular Disease

Disorders of cardiomyocyte metabolism play a crucial role in many cardiovascular diseases, such as myocardial infarction, heart failure and ischemia-reperfusion injury. In myocardial infarction, cardiomyocyte metabolism is regulated by mitochondrial changes and biogenesis, which allows energy homeostasis. There are many proteins in cells that regulate and control metabolic processes. One of them is irisin (Ir), which is released from the transmembrane protein FNDC5. Initial studies indicated that Ir is a myokine secreted mainly by skeletal muscles. Further studies showed that Ir was also present in various tissues. However, its highest levels were observed in cardiomyocytes. Ir is responsible for many processes, including the conversion of white adipose tissue (WAT) to brown adipose tissue (BAT) by increasing the expression of thermogenin (UCP1). In addition, Ir affects mitochondrial biogenesis. Therefore, the levels of FNDC5/Ir in the blood and myocardium may be important in cardiovascular disease. This review discusses the current knowledge about the role of FNDC5/Ir in cardiovascular disease.

The Role of Irisin/FNDC5 Expression and Its Serum Level in Breast Cancer

Irisin (Ir) is an adipomyokine formed from fibronectin type III domain-containing protein 5 (FNDC5), which can be found in various cancer tissues. Additionally, FNDC5/Ir is suspected of inhibiting the epithelial-mesenchymal transition (EMT) process. This relationship has been poorly studied for breast cancer (BC). The ultrastructural cellular localizations of FNDC5/Ir were examined in BC tissues and BC cell lines. Furthermore, we compared serum levels of Ir with FNDC5/Ir expression in BC tissues. The aim of this study was to examine the levels of EMT markers, such as E-cadherin, N-cadherin, SNAIL, SLUG, and TWIST, and to compare their expression levels with FNDC5/Ir in BC tissues. Tissue microarrays with 541 BC samples were used to perform immunohistochemical reactions. Serum levels of Ir were assessed in 77 BC patients. We investigated FNDC5/Ir expression and ultrastructural localization in MCF-7, MDA-MB-231, and MDA-MB-468 BC cell lines and in the normal breast cell line (Me16c), which was used as the control. FNDC5/Ir was present in BC cell cytoplasm and tumor fibroblasts. FNDC5/Ir expression levels in BC cell lines were higher compared to those in the normal breast cell line. Serum Ir levels did not correlate with FNDC5/Ir expression in BC tissues but were associated with lymph node metastasis (N) and histological grade (G). We found that FNDC5/Ir correlated moderately with E-cadherin and SNAIL. Higher Ir serum level is associated with lymph node metastasis and increased grade of malignancy. FNDC5/Ir expression is associated with E-cadherin expression level.

Association of Irisin/FNDC5 with ERRα and PGC-1α Expression in NSCLC

The rapid growth and division of cancer cells are associated with mitochondrial biogenesis or switching to glycolysis. ERRα, PGC-1α and irisin/FNDC5 are some of the proteins that can influence these processes. The aim of this study was to determine the correlation of these proteins in non-small cell lung cancer (NSCLC) and to investigate their association with clinicopathological parameters. Immunohistochemistry reactions were performed on tissue microarrays (860 NSCLC, 140 non-malignant lung tissue). The normal fibroblast cell line (IMR-90) and lung cancer cell lines (NCI-H1703 and NCI-H522) were used as co-cultures. The mRNA levels of FNDC5 and ESRRA (encoding ERRα) were assessed in IMR-90 cells after co-culture with lung cancer cells. We observed a decreased level of ERRα with an increase in tumor size (T), stages of the disease, and lymph node metastases (N). In the adenocarcinoma (AC) subtype, patients with a higher ERRα expression had significantly longer overall survival. A moderate positive correlation was observed between FNDC5 mRNA and ESRRA mRNA in NSCLCs. The expression of FNDC5 mRNA in IMR-90 cells increased after 24 h, and ESRRA gene expression increased after 48 h of co-culture. The ERRα receptor with PGC-1α participates in the control of FNDC5/irisin expression. Normal fibroblasts revealed an upregulation of the FNDC5 and ESRRA genes under the influence of lung cancer cells.

Implication of Irisin in Different Types of Cancer: A Systematic Review and Meta-Analysis

Cancer is a set of diseases characterized by several hallmark properties, such as increased angiogenesis, proliferation, invasion, and metastasis. The increased angiogenic activity constantly supplies the tumors with nutrients and a plethora of cytokines to ensure cell survival. Along these cytokines is a newly discovered protein, called irisin, which is released into the circulation after physical exercise. Irisin is the product of fibronectin type III domain-containing protein 5 (FNDC5) proteolytic cleavage. Recently it has been the topic of investigation in several types of cancer. In this study, we conducted a systematic review and meta-analysis to investigate its implication in different types of cancer. Our results suggest that irisin expression is decreased in cancer patients, thus it can be used as a valid biomarker for the diagnosis of several types of cancer. In addition, our results indicate that irisin may have an important role in tumor progression and metastasis since it is involved in multiple signaling pathways that promote cell proliferation and migration.

Proliferating Lymphatic Endothelial Cells as a Prognostic Marker in Head and Neck Squamous Cell Carcinoma

Podoplanin and Ki-67 are two important markers of cancer progression. The aim of this study is to evaluate double immunostaining for Ki-67 and podoplanin in head and neck squamous cell carcinoma (HNSCC), and to observe the involvement of lymphagiogenesis in tumoral and peritumoral areas, as well as the density of tumor proliferation correlated with histopathological grading. A total of 50 patients with HNSCC were included in this study. We carried out a morphological evaluation of tissue samples, after that, cases were selected for double Ki-67 and podoplanin immunostaining. Podoplanin expression was significantly correlated with histopathological grade (p < 0.05; p = 0.037) and expression of Ki-67 (p < 0.05; p = 0.050). A high expression of podoplanin, as well as of the proliferation factor Ki-67, was observed in histopathological grade G3 and the correlation between these (p < 0.05; p = 0.028), and implication of LMVD and LVI was not significant (LMVD p = 0.577; LVI p = 0.976). This study demonstrated the importance of double immunolabeling in assessing lymphagiogenesis and tumor proliferation in correlation with histopathological grades in HNSCC.

Expression of Irisin/FNDC5 in Breast Cancer

Irisin is a myokine formed from fibronectin type III domain-containing protein 5 (FNDC5), which can be found in various cancer tissues. FNDC5 and irisin levels have been poorly studied in the tumor tissues of breast cancer (BC). The aim of this study was to determine the levels of irisin expression in BC tissues and compare them to clinicopathological factors and Ki-67 and PGC-1α expression levels. Tissue microarrays (TMAs) with 541 BC tissues and 61 samples of non-malignant breast disease (NMBD; control) were used to perform immunohistochemical reactions. FNDC5 gene expression was measured in 40 BC tissue samples, 40 samples from the cancer margin, and 16 NMBD samples. RT-PCR was performed for the detection of FNDC5 gene expression. Higher irisin expression was found in BC patients compared to normal breast tissue. FNDC5/irisin expression was higher in patients without lymph node metastases. Longer overall survival was observed in patients with higher irisin expression levels. FNDC5/irisin expression was increased in BC tissues and its high level was a good prognostic factor for survival in BC patients.

Role of irisin in physiology and pathology

Irisin, out-membrane part of fibronectin type III domain-containing 5 protein (FNDC5), was activated by Peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) during physical exercise in skeletal muscle tissues. Most studies have reported that the concentration of irisin is highly associated with health status. For instance, the level of irisin is significantly lower in patients with obesity, osteoporosis/fractures, muscle atrophy, Alzheimer's disease, and cardiovascular diseases (CVDs) but higher in patients with cancer. Irisin can bind to its receptor integrin αV/β5 to induce browning of white fat, maintain glucose stability, keep bone homeostasis, and alleviate cardiac injury. However, it is unclear whether it works by directly binding to its receptors to regulate muscle regeneration, promote neurogenesis, keep liver glucose homeostasis, and inhibit cancer development. Supplementation of recombinant irisin or exercise-activated irisin might be a successful strategy to fight obesity, osteoporosis, muscle atrophy, liver injury, and CVDs in one go. Here, we summarize the publications of FNDC5/irisin from PubMed/Medline, Scopus, and Web of Science until March 2022, and we review the role of FNDC5/irisin in physiology and pathology.