Metformin suppresses proliferation and invasion of drug-resistant breast cancer cells by activation of the Hippo pathway

Breast cancer drug resistance: Decoding the roles of Hippo pathway crosstalk

The most significant factors that lead to cancer-related death in breast cancer (BC) patients include drug resistance, migration, invasion, and metastasis. Several signaling pathways are involved in the development of BC. The different types of BC are initially sensitive to chemotherapy, and drug resistance can occur through multiple molecular mechanisms. Regardless of developing targeted Therapy, due to the heterogenic nature and complexity of drug resistance, it is a major clinical challenge with the low survival rate in BC patients. The deregulation of several signaling pathways, particularly the Hippo pathway (HP), is one of the most recent findings about the molecular mechanisms of drug resistance in BC, which are summarized in this review. Given that HP is one of the recent cancer research hotspots, this review focuses on its implication in BC drug resistance. Unraveling the different molecular basis of HP through its crosstalk with other signaling pathways, and determining the effectiveness of HP inhibitors can provide new insights into possible therapeutic strategies for overcoming chemoresistance in BC.

The NDR family of kinases: essential regulators of aging

Aging is defined as a progressive decline of cognitive and physiological functions over lifetime. Since the definition of the nine hallmarks of aging in 2013 by López-Otin, numerous studies have attempted to identify the main regulators and contributors in the aging process. One interesting group of proteins whose participation has been implicated in several aging hallmarks are the nuclear DBF2-related (NDR) family of serine-threonine AGC kinases. They are one of the core components of the Hippo signaling pathway and include NDR1, NDR2, LATS1 and LATS2 in mammals, along with its highly conserved metazoan orthologs; Trc in Drosophila melanogaster, SAX-1 in Caenorhabditis elegans, CBK1, DBF20 in Saccharomyces cerevisiae and orb6 in Saccharomyces pombe. These kinases have been independently linked to the regulation of widely diverse cellular processes disrupted during aging such as the cell cycle progression, transcription, intercellular communication, nutrient homeostasis, autophagy, apoptosis, and stem cell differentiation. However, a comprehensive overview of the state-of-the-art knowledge regarding the post-translational modifications of and by NDR kinases in aging has not been conducted. In this review, we summarize the current understanding of the NDR family of kinases, focusing on their relevance to various aging hallmarks, and emphasize the growing body of evidence that suggests NDR kinases are essential regulators of aging across species.

High-accuracy prediction of colorectal cancer chemotherapy efficacy using machine learning applied to gene expression data

Introduction: FOLFOX and FOLFIRI chemotherapy are considered standard first-line treatment options for colorectal cancer (CRC). However, the criteria for selecting the appropriate treatments have not been thoroughly analyzed. Methods: A newly developed machine learning model was applied on several gene expression data from the public repository GEO database to identify molecular signatures predictive of efficacy of 5-FU based combination chemotherapy (FOLFOX and FOLFIRI) in patients with CRC. The model was trained using 5-fold cross validation and multiple feature selection methods including LASSO and VarSelRF methods. Random Forest and support vector machine classifiers were applied to evaluate the performance of the models. Results and Discussion: For the CRC GEO dataset samples from patients who received either FOLFOX or FOLFIRI, validation and test sets were >90% correctly classified (accuracy), with specificity and sensitivity ranging between 85%-95%. In the datasets used from the GEO database, 28.6% of patients who failed the treatment therapy they received are predicted to benefit from the alternative treatment. Analysis of the gene signature suggests the mechanistic difference between colorectal cancers that respond and those that do not respond to FOLFOX and FOLFIRI. Application of this machine learning approach could lead to improvements in treatment outcomes for patients with CRC and other cancers after additional appropriate clinical validation.

YAP/TAZ axis was involved in the effects of metformin on breast cancer

Breast cancer is malignant tumours in women. A large amount of data analysis shows that Metformin has been shown to play a significance role in reducing the risk of breast cancer, but the mechanism remains unclear. The hippo signalling pathway can be involved in the formation, metastasis and recurrence of breast cancer. When YAP/TAZ is activated, cells can overcome contact inhibition and enter a state of uncontrolled proliferation. Therefore, YAP/TAZ is considered a potential therapeutic target for breast cancer. Eighty breast cancer patients, forty cases of triple-negative and forty cases of HER-2+, were included in this study. In vitro and in vivo experiments were used to confirm the YAP/TAZ axis was involved in the effects of metformin on breast cancer. EMT plays an important role in breast cancer, including chemoresistance and tumour metastasis. Our results confirmed that YAP could modulate the activity of EMT, which in turn altered tumour resistance. Therefore, MET can inhibit EMT by reducing the expression of YAP, and finally achieve the therapeutic effect of breast cancer. Our findings support metformin as a novel YAP inhibitor and potentially as a novel breast cancer drug.

Low dosage combination treatment with metformin and simvastatin inhibits obesity-promoted pancreatic cancer development in male KrasG12D mice

Pancreatic ductal adenocarcinoma (PDAC), a highly lethal disease with limited therapeutic options, may benefit from repurposing of FDA-approved drugs in preventive or interceptive strategies in high-risk populations. Previous animal studies demonstrated that the use of metformin and statins as single agents at relatively high doses restrained PDAC development. Here, four-week-old mice expressing KrasG12D in all pancreatic lineages (KC mice) and fed an obesogenic high fat, high calorie diet that promotes early PDAC development were randomized onto low dosage metformin, simvastatin, or both drugs in combination administered orally. Dual treatment attenuated weight gain, fibro-inflammation, and development of advanced PDAC precursor lesions (pancreatic intraepithelial neoplasia [PanIN]-3) in male KC mice, without significant effect in females or when administered individually. Dual-treated KC mice had reduced proliferation of PanIN cells and decreased transcriptional activity of the Hippo effectors, YAP and TAZ, which are important regulators of PDAC development. Metformin and simvastatin also synergistically inhibited colony formation of pancreatic cancer cells in vitro. Together, our data demonstrated that a combination of low doses of metformin and simvastatin inhibits PDAC development and imply that both drugs are promising agents for being tested in clinical trials for preventing pancreatic cancer progression.

AMPK-Dependent YAP Inhibition Mediates the Protective Effect of Metformin against Obesity-Associated Endothelial Dysfunction and Inflammation

Hyperglycemia is a crucial risk factor for cardiovascular diseases. Chronic inflammation is a central characteristic of obesity, leading to many of its complications. Recent studies have shown that high glucose activates Yes-associated protein 1 (YAP) by suppressing AMPK activity in breast cancer cells. Metformin is a commonly prescribed anti-diabetic drug best known for its AMPK-activating effect. However, the role of YAP in the vasoprotective effect of metformin in diabetic endothelial cell dysfunction is still unknown. The present study aimed to investigate whether YAP activation plays a role in obesity-associated endothelial dysfunction and inflammation and examine whether the vasoprotective effect of metformin is related to YAP inhibition. Reanalysis of the clinical sequencing data revealed YAP signaling, and the YAP target genes CTGF and CYR61 were upregulated in aortic endothelial cells and retinal fibrovascular membranes from diabetic patients. YAP overexpression impaired endothelium-dependent relaxations (EDRs) in isolated mouse aortas and increased the expression of YAP target genes and inflammatory markers in human umbilical vein endothelial cells (HUVECs). High glucose-activated YAP in HUVECs and aortas was accompanied by increased production of oxygen-reactive species. AMPK inhibition was found to induce YAP activation, resulting in increased JNK activity. Metformin activated AMPK and promoted YAP phosphorylation, ultimately improving EDRs and suppressing the JNK activity. Targeting the AMPK-YAP-JNK axis could become a therapeutic strategy for alleviating vascular dysfunction in obesity and diabetes.

Three-Dimensional Spheroid Configurations and Cellular Metabolic Properties of Oral Squamous Carcinomas Are Possible Pharmacological and Pathological Indicators

The objective of the current study was to elucidate the clinicopathological significance and appearance of in vitro three-dimension (3D) spheroid models of oral malignant tumors that were prepared from four pathologically different squamous cell carcinoma (OSCC; low-grade; SSYP and MO-1000, intermediate-grade; LEM2) and oral adenosquamous carcinoma (OASC; high-grade; Mesimo) obtained from patients with different malignant stages. To characterize the biological significance of these cell lines themselves, two-dimensional (2D) cultured cells were subjected to cellular metabolic analysis by a Seahorse bioanalyzer alongside the measurement of the cytotoxicity of cisplatin (CDDP). The appearance of their 3D spheroids was then observed by phase contrast microscopy, and both 2D and 3D cultured cells were subject to trypsin digestion and qPCR analysis of factors related to oncogenic signaling and other related analyses. ATP-linked respiration and proton leaking were significantly different among the four cell lines, and the malignant stages of these cultures were significantly associated with increased ATP-linked respiration and decreased proton leakage. Alternatively, the appearances of these 3D spheroids were also significantly diverse among them, and their differences increased in the order of LEM2, MO-1000, SSYP, and Mesimo. Interestingly, these orders were exactly the same in that the efficacies of CDDP-induced cytotoxicity increased in the same order. qPCR analysis indicated that the levels of expression of oncogenic signaling-related factors varied among these four cell lines, and the values for fibronectin and a key regulator of mitochondrial biogenesis, PGC-1α, were prominently elevated in cultures of the worst malignant Mesimo cells. In addition, although 0.25% trypsin-induced destruction was comparable among all four 2D cultured cells, the values for the 3D spheroids were also substantially varied among these cultures. The findings reported herein indicate that cellular metabolic functions and 3D spheroid architectures may be valuable and useful indicators for estimating the pathological and drug-sensitive aspects of OSCC and OASC malignancies.

Metformin and HER2-positive breast cancer: Mechanisms and therapeutic implications

Due to the strong association between diabetes and cancer incidents, several anti-diabetic drugs, including metformin, have been examined for their anticancer activity. Metformin is a biguanide antihyperglycemic agent used as a first-line drug for type II diabetes mellitus. It exhibits anticancer activity by impacting different molecular pathways, such as AMP-inducible protein kinase (AMPK)-dependent and AMPK-independent pathways. Additionally, Metformin indirectly inhibits IGF-1R signaling, which is highly activated in breast malignancy. On the other hand, breast cancer is one of the major causes of cancer-related morbidity and mortality worldwide, where the human epidermal growth factor receptor-positive (HER2-positive) subtype is one of the most aggressive ones with a high rate of lymph node metastasis. In this review, we summarize the association between diabetes and human cancer, listing recent evidence of metformin's anticancer activity. A special focus is dedicated to HER2-positive breast cancer with regards to the interaction between HER2 and IGF-1R. Then, we discuss combination therapy strategies of metformin and other anti-diabetic drugs in HER2-positive breast cancer.

Engine shutdown: migrastatic strategies and prevention of metastases

Most cancer-related deaths among patients with solid tumors are caused by metastases. Migrastatic strategies represent a unique therapeutic approach to prevent all forms of cancer cell migration and invasion. Because the migration machinery has been shown to promote metastatic dissemination, successful migrastatic therapy may reduce the need for high-dose cytotoxic therapies that are currently used to prevent the risk of metastatic dissemination. In this review we focus on anti-invasive and antimetastatic strategies that hold promise for the treatment of solid tumors. The best targets for migrastatic therapy would be those that are required by all forms of motility, such as ATP availability, mitochondrial metabolism, and cytoskeletal dynamics and cell contractility.

Insights on the role of anti-inflammatory and immunosuppressive agents in the amelioration of diabetes

Diabetes is a major health problem worldwide. It is a chronic metabolic disorder that produces overt hyperglycemic condition that occurs either when the pancreas does not produce enough insulin due to excessive destruction of pancreatic β-cells (type 1 diabetes) or due to development of insulin resistance (type 2 diabetes). An autoimmune condition known as type 1 diabetes (T1D) results in the targeted immune death of β-cells that produce insulin. The only available treatment for T1D at the moment is the lifelong use of insulin. Multiple islet autoantibody positivity is used to diagnose T1D. There are four standard autoantibodies observed whose presence shows the development of T1D: antibodies against insulin, glutamic acid decarboxylase (GAD65), zinc T8 transporter (ZnT8), and tyrosine phosphatase-like protein (ICA512). In type 2 diabetes (T2D), an inflammatory response precipitates as a consequence of the immune response to high blood glucose level along with the presence of inflammation mediators produced by macrophages and adipocytes in fat tissue. The slow and chronic inflammatory condition of adipose tissue produces insulin resistance leading to increased stress on pancreatic β-cells to produce more insulin to compensate for the insulin resistance. Thus, this stress condition exacerbates the apoptosis of β-cells leading to insufficient production of insulin, resulting in hyperglycemia which signifies late stage T2D. Therefore, the therapeutic utilization of immunosuppressive agents may be a better alternative over the use of insulin and oral hypoglycemic agents for the treatment of T1D and T2D, respectively. This review enlightens the immune intervention for the prevention and amelioration of T1D and T2D in humans with main focus on the antigen-specific immune suppressive therapy.

Targeting Hippo pathway: A novel strategy for Helicobacter pylori-induced gastric cancer treatment

The Hippo pathway plays an important role in cell proliferation, apoptosis, and differentiation; it is a crucial regulatory pathway in organ development and tumor growth. Infection with Helicobacter pylori (H. pylori) increases the risk of developing gastric cancer. In recent years, significant progress has been made in understanding the mechanisms by which H. pylori infection promotes the development and progression of gastric cancer via the Hippo pathway. Exploring the Hippo pathway molecules may yield new diagnostic and therapeutic targets for H. pylori-induced gastric cancer. The current article reviews the composition and regulatory mechanism of the Hippo pathway, as well as the research progress of the Hippo pathway in the occurrence and development of H. pylori-related gastric cancer, in order to provide a broader perspective for the study and prevention of gastric cancer.

High expression of IGHG1 promotes breast cancer malignant development by activating the AKT pathway

This study researched the exact function of IgG1 heavy chain (IGHG1) on breast cancer (BC) progression. IGHG1 level within BC and paired normal tissues was acquired in Gene Expression Profiling Interactive Analysis dataset. Meanwhile, this work harvested tumor and paired healthy tissues in 42 BC cases. siRNA targeting IGHG1 was transfected into BC cells. SC79 was used to treat the transfected BC cells. CCK-8 assay, clone formation experiment, BrdU assay, Transwell experiment and flow cytometry were carried out to measure the viability, colony formation, proliferation, invasion, and apoptosis of BC cells. Paclitaxel and cisplatin sensitivity of BC cells was evaluated by MTT assay. Real-time quantitative reverse transcription-polymerase chain reaction and Western-blot were performed for measuring mRNA and protein expression. The overexpressed IGHG1 indicated dismal BC survival. IGHG1 silencing attenuated the viability, invasion, proliferation, epithelial-mesenchymal transition, but enhanced the apoptosis of BC cells. IGHG1 silencing enhanced the paclitaxel and cisplatin sensitivity of BC cells. IGHG1 silencing suppressed the activity of the MEK, AKT, and ERK pathways. AKT agonist partially reversed the inhibition of IGHG1 silencing on BC cell malignant phenotype and resistance to paclitaxel and cisplatin. IGHG1 promotes the malignant development of BC by activating the AKT pathway. It may be an effective target for BC treatment.

Action Mechanism of Metformin and Its Application in Hematological Malignancy Treatments: A Review

Hematologic malignancies (HMs) mainly include acute and chronic leukemia, lymphoma, myeloma and other heterogeneous tumors that seriously threaten human life and health. The common effective treatments are radiotherapy, chemotherapy and hematopoietic stem cell transplantation (HSCT), which have limited options and are prone to tumor recurrence and (or) drug resistance. Metformin is the first-line drug for the treatment of type 2 diabetes (T2DM). Recently, studies identified the potential anti-cancer ability of metformin in both T2DM patients and patients that are non-diabetic. The latest epidemiological and preclinical studies suggested a potential benefit of metformin in the prevention and treatment of patients with HM. The mechanism may involve the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway by metformin as well as other AMPK-independent pathways to exert anti-cancer properties. In addition, combining current conventional anti-cancer drugs with metformin may improve the efficacy and reduce adverse drug reactions. Therefore, metformin can also be used as an adjuvant therapeutic agent for HM. This paper highlights the anti-hyperglycemic effects and potential anti-cancer effects of metformin, and also compiles the in vitro and clinical trials of metformin as an anti-cancer and chemosensitizing agent for the treatment of HM. The need for future research on the use of metformin in the treatment of HM is indicated.

Evaluation of Quantification and Normalization Strategies for Phosphoprotein Phosphatase Affinity Proteomics: Application to Breast Cancer Signaling

Accurate quantification of proteomics data is essential for revealing and understanding biological signaling processes. We have recently developed a chemical proteomic strategy termed phosphatase inhibitor beads and mass spectrometry (PIB-MS) to investigate endogenous phosphoprotein phosphatase (PPP) dephosphorylation signaling. Here, we compare the robustness and reproducibility of status quo quantification methods for optimal performance and ease of implementation. We then apply PIB-MS to an array of breast cancer cell lines to determine differences in PPP signaling between subtypes. Breast cancer, a leading cause of cancer death in women, consists of three main subtypes: estrogen receptor-positive (ER+), human epidermal growth factor receptor two positive (HER2+), and triple-negative (TNBC). Although there are effective treatment strategies for ER+ and HER2+ subtypes, tumors become resistant and progress. Furthermore, TNBC has few targeted therapies. Therefore, there is a need to identify new approaches for treating breast cancers. Using PIB-MS, we distinguished TNBC from non-TNBC based on subtype-specific PPP holoenzyme composition. In addition, we identified an increase in PPP interactions with Hippo pathway proteins in TNBC. These interactions suggest that phosphatases in TNBC play an inhibitory role on the Hippo pathway and correlate with increased expression of YAP/TAZ target genes both in TNBC cell lines and in TNBC patients.

KLF2 is a clinical diagnostic and treatment biomarker of breast cancer

Background: As a highly prevalent malignancy among women worldwide, breast cancer, remains a critical public health issue necessitating the development of novel therapeutics and biomarkers. Kruppel Like Factor 2 (KLF2), a member of the Kruppel family of transcription factors, has been implicated in various types of cancer due to its diminished expression; however, the potential implications of KLF2 expression in relation to breast cancer progression, prognosis, and therapy remain unclear. Methods: The present study employed the Tumor Immune Estimation Resource (TIMER) and The Human Protein Atlas databases to investigate the expression pattern of KLF2 in pan-cancer. The relationship between KLF2 expression and clinical features or immune infiltration of The Cancer Genome Atlas (TCGA) breast cancer samples was evaluated using Breast Cancer Integrative Platform (BCIP) and TIMER. The expression levels of KLF2 in breast cancer were validated via immunohistochemical staining analysis. Gene Set Enrichment Analysis (GSEA) to study the KLF2-related gene ontology. STRING database was employed to construct a protein-protein interaction (PPI) network of KLF2 in relation to vascular endothelial growth factor A (VEGFA) and hypoxia-inducible factor 1α (HIF1α). The expression of KLF2 following diverse breast cancer therapies was analyzed in the Gene Expression Omnibus (GEO) databases. The expression of KLF2 following treatment with simvastatin was validated via immunofluorescence and western blotting. Results: Our study reveals that KLF2 displays significantly reduced expression in cancerous tissues compared to non-cancerous controls. Patients with low KLF2 expression levels exhibited poor prognosis across multiple cancer types. KLF2 expression levels were found to be reduced in advanced cancer stages and grades, while positively correlated with the expression of estrogen receptor (ER), progesterone receptor (PR), and tumor size in breast cancer. KLF2 expression is associated with diverse immune infiltration cells, and may impact the breast tumor immune microenvironment by regulating dendritic cell activation. Additionally, we observed a negative correlation between KLF2 expression levels and angiogenesis, as well as the expression of VEGFA and HIF1α. Notably, the anticancer drug simvastatin could induce KLF2 expression in both breast cancer. Conclusion: Based on our observations, KLF2 has potential as a diagnostic, prognostic, and therapeutic biomarker for breast cancer.

Deciphering Potential Role of Hippo Signaling Pathway in Breast Cancer: A Comprehensive Review

Breast cancer is a heterogeneous disease and a leading malignancy around the world. It is a vital cause of untimely mortality among women. Drug resistance is the major challenge for effective cancer therapeutics. In contrast, cancer stem cells (CSCs) are one of the reasons for drug resistance, tumor progression, and metastasis. The small population of CSCs present in each tumor has the ability of self-renewal, differentiation, and tumorigenicity. CSCs are often identified and enriched using a variety of cell surface markers (CD44, CD24, CD133, ABCG2, CD49f, LGR5, SSEA-3, CD70) that exert their functions by different regulatory networks, i.e., Notch, Wnt/β-catenin, hedgehog (Hh), and Hippo signaling pathways. Particularly the Hippo signaling pathway is the emerging and very less explored cancer stem cell pathway. Here, in this review, the Hippo signaling molecules are elaborated with respect to their ability of stemness as epigenetic modulators and how these molecules can be targeted for better cancer treatment and to overcome drug resistance.

Genetic Alterations and Deregulation of Hippo Pathway as a Pathogenetic Mechanism in Bone and Soft Tissue Sarcoma

The Hippo pathway is an evolutionarily conserved modulator of developmental biology with a key role in tissue and organ size regulation under homeostatic conditions. Like other signaling pathways with a significant role in embryonic development, the deregulation of Hippo signaling contributes to oncogenesis. Central to the Hippo pathway is a conserved cascade of adaptor proteins and inhibitory kinases that converge and regulate the activity of the oncoproteins YAP and TAZ, the final transducers of the pathway. Elevated levels and aberrant activation of YAP and TAZ have been described in many cancers. Though most of the studies describe their pervasive activation in epithelial neoplasms, there is increasing evidence pointing out its relevance in mesenchymal malignancies as well. Interestingly, somatic or germline mutations in genes of the Hippo pathway are scarce compared to other signaling pathways that are frequently disrupted in cancer. However, in the case of sarcomas, several examples of genetic alteration of Hippo members, including gene fusions, have been described during the last few years. Here, we review the current knowledge of Hippo pathway implication in sarcoma, describing mechanistic hints recently reported in specific histological entities and how these alterations represent an opportunity for targeted therapy in this heterogeneous group of neoplasm.

Metformin and simvastatin synergistically suppress endothelin 1-induced hypoxia and angiogenesis in multiple cancer types

Multiple cancers have been reported to be associated with angiogenesis and are sensitive to anti-angiogenic therapies. Vascular normalization, by restoring proper tumor perfusion and oxygenation, could limit tumor cell invasiveness and improve the effectiveness of anticancer treatments. However, the underlying anticancer mechanisms of antiangiogenic drugs are still unknown. Metformin (MET) and simvastatin (SVA), two metabolic-related drugs, have been shown to play important roles in modulating the hypoxic tumor microenvironment and angiogenesis. Whether the combination of MET and SVA could exert a more effective antitumor effect than individual treatments has not been examined. The antitumor effect of the synergism of SVA and MET was detected in mouse models, breast cancer patient-derived organoids, and multiple tumor cell lines compared with untreated, SVA, or MET alone. RNA sequencing revealed that the combination of MET and SVA (but not MET or SVA alone) inhibited the expression of endothelin 1 (ET-1), an important regulator of angiogenesis and the hypoxia-related pathway. We demonstrate that the MET and SVA combination showed synergistic effects on inhibiting tumor cell proliferation, promoting apoptosis, alleviating hypoxia, decreasing angiogenesis, and increasing vessel normalization compared with the use of a single agent alone. The MET and SVA combination suppressed ET-1-induced hypoxia-inducible factor 1α expression by increasing prolyl hydroxylase 2 (PHD2) expression. Furthermore, the MET and SVA combination showed a more potent anticancer effect compared with bosentan. Together, our findings suggest the potential application of the MET and SVA combination in antitumor therapy.

A precision medicine approach to metabolic therapy for breast cancer in mice

Increasing evidence highlights approaches targeting metabolism as potential adjuvants to cancer therapy. Sodium-glucose transport protein 2 (SGLT2) inhibitors are the newest class of antihyperglycemic drugs. To our knowledge, SGLT2 inhibitors have not been applied in the neoadjuvant setting as a precision medicine approach for this devastating disease. Here, we treat lean breast tumor-bearing mice with the SGLT2 inhibitor dapagliflozin as monotherapy and in combination with paclitaxel chemotherapy. We show that dapagliflozin enhances the efficacy of paclitaxel, reducing tumor glucose uptake and prolonging survival. Further, the ability of dapagliflozin to enhance the efficacy of chemotherapy correlates with its effect to reduce circulating insulin in some but not all breast tumors. Our data suggest a genetic signature for breast tumors more likely to respond to dapagliflozin in combination with paclitaxel. In the current study, tumors driven by mutations upstream of canonical insulin signaling pathways responded to this combined treatment, whereas tumors driven by mutations downstream of canonical insulin signaling did not. These data demonstrate that dapagliflozin enhances the response to chemotherapy in mice with breast cancer and suggest that patients with driver mutations upstream of canonical insulin signaling may be most likely to benefit from this neoadjuvant approach.

Hippo signaling pathway and respiratory diseases

The hippo signaling pathway is a highly conserved evolutionary signaling pathway that plays an important role in regulating cell proliferation, organ size, tissue development, and regeneration. Increasing evidences consider that the hippo signaling pathway is involved in the process of respiratory diseases. Hippo signaling pathway is mainly composed of mammalian STE20-like kinase 1/2 (MST1/2), large tumor suppressor 1/2 (LATS1/2), WW domain of the Sav family containing protein 1 (SAV1), MOB kinase activator 1 (MOB1), Yes-associated protein (YAP) or transcriptional coactivator with PDZ-binding motif (TAZ), and members of the TEA domain (TEAD) family. YAP is the cascade effector of the hippo signaling pathway. The activation of YAP promotes pulmonary arterial vascular smooth muscle cells (PAVSMCs) proliferation, which leads to pulmonary vascular remodeling; thereby the pulmonary arterial hypertension (PAH) is aggravated. While the loss of YAP leads to high expression of inflammatory genes and the accumulation of inflammatory cells, the pneumonia is consequently exacerbated. In addition, overexpressed YAP promotes the proliferation of lung fibroblasts and collagen deposition; thereby the idiopathic pulmonary fibrosis (IPF) is promoted. Moreover, YAP knockout reduces collagen deposition and the senescence of adult alveolar epithelial cells (AECs); hence the IPF is slowed. In addition, hippo signaling pathway may be involved in the repair of acute lung injury (ALI) by promoting the proliferation and differentiation of lung epithelial progenitor cells and intervening in the repair of pulmonary capillary endothelium. Moreover, the hippo signaling pathway is involved in asthma. In conclusion, the hippo signaling pathway is involved in respiratory diseases. More researches are needed to focus on the molecular mechanisms by which the hippo signaling pathway participates in respiratory diseases.

Novel sequential therapy with metformin enhances the effects of cisplatin in testicular germ cell tumours via YAP1 signalling

Background

Testicular germ cell tumours (TGCTs) are the most commonly diagnosed malignancy in young men. Although cisplatin has been shown to be effective to treat TGCT patients, long-term follow-up has shown that TGCT survivors who accepted cisplatin treatment suffered from a greater number of adverse reactions than patients who underwent orchiectomy alone. As metformin has shown an anticancer effect in various cancers, we investigated whether metformin could enhance the effects of cisplatin to treat TGCTs.

Methods

The anticancer effects of different treatment strategies consisting of metformin and cisplatin in TCam-2 and NTERA-2 cells were assessed in vitro and in vivo. First, we used a colony formation assay, CCK-8 and MTT assays to explore the viability of TGCT cells. Flow cytometry was used to assess the cell cycle and apoptosis of TGCTs. Then, Western blotting was used to detect the protein expression of TGCTs cells after different treatments. In addition, a xenograft model was used to investigate the effects of the different treatments on the proliferation of TGCT cells. Immunohistochemistry assays were performed to analyse the expression of related proteins in the tissues from the xenograft model.

Results

Metformin inhibited the proliferation of TCam-2 and NTERA-2 cells by arresting them in G1 phase, while metformin did not induce apoptosis in TGCT cells. Compared with cisplatin monotherapy, the CCK-8, MTT assay and colony formation assay showed that sequential treatment with metformin and cisplatin produced enhanced anticancer effects. Further study showed that metformin blocked the cells in G1 phase by inducing phosphorylated YAP1 and reducing the expression of cyclin D1, CDK6, CDK4 and RB, which enhanced the chemosensitivity of cisplatin and activated the expression of cleaved caspase 3 in TGCTs.

Conclusions

Our study discovers the important role of YAP1 in TGCTs and reports a new treatment strategy that employs the sequential administration of metformin and cisplatin, which can reduce the required cisplatin dose and enhance the sensitivity of TGCT cells to cisplatin. Therefore, this sequential treatment strategy may facilitate the development of basic and clinical research for anticancer therapies to treat TGCTs.

Licochalcone A inhibits cell growth through the downregulation of the Hippo pathway via PES1 in cholangiocarcinoma cells

Overexpression or activation of Yes-associated protein (YAP) is common in cancer cells. Thus, targeting YAP may be a strategy for cancer therapy. Licochalcone A (LicA) is a primary active compound of licorice root and is known to have medicinal effects, such as antioxidant, antibacterial, antiviral, and anticancer effects. However, the anticancer pharmacological mechanism of LicA has not been investigated in cholangiocarcinoma. In this study, we investigated the antiproliferative effect of LicA and the underlying molecular mechanism in HCCC-9810 and RBE human cholangiocarcinoma cells. Our experiments indicated that LicA suppressed the growth of cholangiocarcinoma cells through inactivation of the Hippo pathway. Pescadillo ribosomal biogenesis factor 1 (PES1) was notably upregulated and related to carcinogenesis. We also found that LicA suppressed the expression and nuclear localization of PES1, which was associated with the inhibition of YAP expression and transcriptional activity.

Apoptosis in Type 2 Diabetes: Can It Be Prevented? Hippo Pathway Prospects

Diabetes mellitus is a heterogeneous disease of complex etiology and pathogenesis. Hyperglycemia leads to many serious complications, but also directly initiates the process of β cell apoptosis. A potential strategy for the preservation of pancreatic β cells in diabetes may be to inhibit the implementation of pro-apoptotic pathways or to enhance the action of pancreatic protective factors. The Hippo signaling pathway is proposed and selected as a target to manipulate the activity of its core proteins in therapy-basic research. MST1 and LATS2, as major upstream signaling kinases of the Hippo pathway, are considered as target candidates for pharmacologically induced tissue regeneration and inhibition of apoptosis. Manipulating the activity of components of the Hippo pathway offers a wide range of possibilities, and thus is a potential tool in the treatment of diabetes and the regeneration of β cells. Therefore, it is important to fully understand the processes involved in apoptosis in diabetic states and completely characterize the role of this pathway in diabetes. Therapy consisting of slowing down or stopping the mechanisms of apoptosis may be an important direction of diabetes treatment in the future.

Willin/FRMD6: A Multi-Functional Neuronal Protein Associated with Alzheimer's Disease

The FERM domain-containing protein 6 (FRMD6), also known as Willin, is an upstream regulator of Hippo signaling that has recently been shown to modulate actin cytoskeleton dynamics and mechanical phenotype of neuronal cells through ERK signaling. Physiological functions of Willin/FRMD6 in the nervous system include neuronal differentiation, myelination, nerve injury repair, and vesicle exocytosis. The newly established neuronal role of Willin/FRMD6 is of particular interest given the mounting evidence suggesting a role for Willin/FRMD6 in Alzheimer's disease (AD), including a series of genome wide association studies that position Willin/FRMD6 as a novel AD risk gene. Here we describe recent findings regarding the role of Willin/FRMD6 in the nervous system and its actions in cellular perturbations related to the pathogenesis of AD.

Metformin attenuates silica-induced pulmonary fibrosis via AMPK signaling

Background

Silicosis is one of the most common occupational pulmonary fibrosis caused by respirable silica-based particle exposure, with no ideal drugs at present. Metformin, a commonly used biguanide antidiabetic agent, could activate AMP-activated protein kinase (AMPK) to exert its pharmacological action. Therefore, we sought to investigate the role of metformin in silica-induced lung fibrosis.

Methods

The anti-fibrotic role of metformin was assessed in 50 mg/kg silica-induced lung fibrosis model. Silicon dioxide (SiO₂)-stimulated lung epithelial cells/macrophages and transforming growth factor-beta 1 (TGF-β1)-induced differentiated lung fibroblasts were used for in vitro models.

Results

At the concentration of 300 mg/kg in the mouse model, metformin significantly reduced lung inflammation and fibrosis in SiO₂-instilled mice at the early and late fibrotic stages. Besides, metformin (range 2–10 mM) reversed SiO₂-induced cell toxicity, oxidative stress, and epithelial-mesenchymal transition process in epithelial cells (A549 and HBE), inhibited inflammation response in macrophages (THP-1), and alleviated TGF-β1-stimulated fibroblast activation in lung fibroblasts (MRC-5) via an AMPK-dependent pathway.

Conclusions

In this study, we identified that metformin might be a potential drug for silicosis treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03036-5.

Metformin: review of epidemiology and mechanisms of action in pancreatic cancer

Pancreatic ductal adenocarcinoma continues to be a lethal disease, for which efficient treatment options are very limited. Increasing efforts have been taken to understand how to prevent or intercept this disease at an early stage. There is convincing evidence from epidemiologic and preclinical studies that the antidiabetic drug metformin possesses beneficial effects in pancreatic cancer, including reducing the risk of developing the disease and improving survival in patients with early-stage disease. This review will summarize the current literature about the epidemiological data on metformin and pancreatic cancer as well as describe the preclinical evidence illustrating the anticancer effects of metformin in pancreatic cancer. Underlying mechanisms and targets of metformin will also be discussed. These include direct effects on transformed pancreatic epithelial cells and indirect, systemic effects on extra-pancreatic tissues.

Utilizing the Hippo pathway as a therapeutic target for combating endocrine-resistant breast cancer

Drug resistance is always a great obstacle in any endocrine therapy of breast cancer. Although the combination of endocrine therapy and targeted therapy has been shown to significantly improve prognosis, refractory endocrine resistance is still common. Dysregulation of the Hippo pathway is often related to the occurrence and the development of many tumors. Targeted therapies of this pathway have played important roles in the study of triple negative breast cancer (TNBC). Targeting the Hippo pathway in combination with chemotherapy or other targeted therapies has been shown to significantly improve specific antitumor effects and reduce cancer antidrug resistance. Further exploration has shown that the Hippo pathway is closely related to endocrine resistance, and it plays a "co-correlation point" role in numerous pathways involving endocrine resistance, including related pathways in breast cancer stem cells (BCSCs). Agents and miRNAs targeting the components of the Hippo pathway are expected to significantly enhance the sensitivity of breast cancer cells to endocrine therapy. This review initially explains the possible mechanism of the Hippo pathway in combating endocrine resistance, and it concludes by recommending endocrine therapy in combination with therapies targeting the Hippo pathway in the study of endocrine-resistant breast cancers.

Mechanisms of metformin inhibiting cancer invasion and migration

Cancer currently ranks among the leading causes of death globally. Cancer invasion and metastasis transform locally grown cancers to a systemic and life-threatening disease, which accounts for the most significant challenge in cancer treatment. Recent studies showed that Metformin, the most commonly used first-line oral drug for the treatment of type 2 diabetes (T2DM), could prevent and treat various cancers. Moreover, multiple evidence suggested that metformin inhibited cancer invasion and metastasis, which could improve the prognosis of cancer patients administrated with metformin. To better understand the anti-cancer role of metformin, the present review summarized the potential mechanisms of inhibiting cancer invasion and metastasis by metformin, including AMPK signaling pathway, EMT signaling pathway, epigenetic modification and so on. However, multiple problems remain unresolved and more clinical trials are needed to prove the inhibition of cancer invasion and metastasis by metformin.

Leukemia inhibitory factor promotes gastric cancer cell proliferation, migration, and invasion via the LIFR-Hippo-YAP pathway

The long-term outcome of gastric cancer (GC) patients remains unsatisfactory despite some recent improvements. Leukemia inhibitory factor (LIF) is a prognostic biomarker for some solid tumors, however its role in GC remains unknown. In this study, we demonstrated that LIF and LIF receptor (LIFR) are overexpressed in GC tissues and established that a correlation exists between them. LIF and LIFR expression are associated with tumor differentiation, lymphovascular invasion, tumor stage, lymph node metastasis, and pTNM stage, indicating that they may be useful prognostic factors. LIF promoted GC cell proliferation, colony formation, invasion, migration, and tumor growth; it also promoted cell cycle progression and inhibited apoptosis; and knocking out the LIFR gene reversed the effects of LIF. LIF inhibited the activity of the Hippo pathway, resulting in reduced phosphorylation of YAP, increased YAP nuclear translocation, and increased cell proliferation. Finally, silencing YAP mRNA expression suppressed cell proliferation. Overall, the results demonstrate that LIF promotes the malignant biological behavior of GC cells through LIFR-Hippo-YAP signaling. LIF may therefore be a useful biomarker for GC.

Metformin suppresses proliferation and invasion of drug-resistant breast cancer cells by activation of the Hippo pathway

Drug resistance limits the clinical efficacy of breast cancer therapies, and overexpression or activation of Yes-associated protein (YAP) is common in drug-resistant cancer cells. Thus, inhibition of YAP may reduce resistance to anti-cancer drugs. Metformin (MET), a first-line diabetes medication that also has anti-tumour activities, induces AMP-activated protein kinase (AMPK), directly phosphorylates YAP and inhibits YAP transcriptional activity. In this study, we determined the effect of MET on the proliferation and invasion of drug-resistant breast cancer cells and then investigated the underlying molecular mechanism. Our in vivo and in vitro experiments indicated that MET suppressed breast cancer by an AMPK-independent pathway to decrease YAP nuclear localization. In drug-sensitive cells, MET activated the Hippo pathway by increasing KIBRA and FRMD6 expression, but this did not occur in drug-resistant cells. Scribble (SCRIB), a cell polarity protein, was notably down-regulated in tamoxifen- and paclitaxel-resistant breast cancer cells relative to sensitive cells. We also found that MET suppressed the proliferation and invasion of drug-resistant breast cancer cells by increasing the expression and cell membrane localization of SCRIB, which enhanced the interaction of SCRIB with MST1 and LATS1, and inhibited YAP nuclear localization and transcriptional activity.