Involvement of LKB1 in epithelial-mesenchymal transition (EMT) of human lung cancer cells

LKB1 Loss Correlates with STING Loss and, in Cooperation with β-Catenin Membranous Loss, Indicates Poor Prognosis in Patients with Operable Non-Small Cell Lung Cancer

To investigate the incidence and prognostically significant correlations and cooperations of LKB1 loss of expression in non-small cell lung cancer (NSCLC), surgical specimens from 188 metastatic and 60 non-metastatic operable stage I-IIIA NSCLC patients were analyzed to evaluate their expression of LKB1 and pAMPK proteins in relation to various processes. The investigated factors included antitumor immunity response regulators STING and PD-L1; pro-angiogenic, EMT and cell cycle targets, as well as metastasis-related (VEGFC, PDGFRα, PDGFRβ, p53, p16, Cyclin D1, ZEB1, CD24) targets; and cell adhesion (β-catenin) molecules. The protein expression levels were evaluated via immunohistochemistry; the RNA levels of LKB1 and NEDD9 were evaluated via PCR, while KRAS exon 2 and BRAFV600E mutations were evaluated by Sanger sequencing. Overall, loss of LKB1 protein expression was observed in 21% (51/248) patients and correlated significantly with histotype (p < 0.001), KRAS mutations (p < 0.001), KC status (concomitant KRAS mutation and p16 downregulation) (p < 0.001), STING loss (p < 0.001), and high CD24 expression (p < 0.001). STING loss also correlated significantly with loss of LKB1 expression in the metastatic setting both overall (p = 0.014) and in lung adenocarcinomas (LUACs) (p = 0.005). Additionally, LKB1 loss correlated significantly with a lack of or low β-catenin membranous expression exclusively in LUACs, both independently of the metastatic status (p = 0.019) and in the metastatic setting (p = 0.007). Patients with tumors yielding LKB1 loss and concomitant nonexistent or low β-catenin membrane expression experienced significantly inferior median overall survival of 20.50 vs. 52.99 months; p < 0.001 as well as significantly greater risk of death (HR: 3.32, 95% c.i.: 1.71-6.43; p <0.001). Our findings underscore the impact of the synergy of LKB1 with STING and β-catenin in NSCLC, in prognosis.

LKB1 depletion-mediated epithelial-mesenchymal transition induces fibroblast activation in lung fibrosis

The factors that determine fibrosis progression or normal tissue repair are largely unknown. We previously demonstrated that autophagy inhibition-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments local myofibroblast differentiation in pulmonary fibrosis by paracrine signalling. Here, we report that liver kinase B1 (LKB1) inactivation in ATII cells inhibits autophagy and induces EMT as a consequence. In IPF lungs, this is caused by downregulation of CAB39L, a key subunit within the LKB1 complex. 3D co-cultures of ATII cells and MRC5 lung fibroblasts coupled with RNA sequencing (RNA-seq) confirmed that paracrine signalling between LKB1-depleted ATII cells and fibroblasts augmented myofibroblast differentiation. Together these data suggest that reduced autophagy caused by LKB1 inhibition can induce EMT in ATII cells and contribute to fibrosis via aberrant epithelial-fibroblast crosstalk.

Roflumilast inhibits tumor growth and migration in STK11/LKB1 deficient pancreatic cancer

Pancreatic cancer is a malignant tumor of the digestive system. It is highly aggressive, easily metastasizes, and extremely difficult to treat. This study aimed to analyze the genes that might regulate pancreatic cancer migration to provide an essential basis for the prognostic assessment of pancreatic cancer and individualized treatment. A CRISPR knockout library directed against 915 murine genes was transfected into TB 32047 cell line to screen which gene loss promoted cell migration. Next-generation sequencing and PinAPL.py- analysis was performed to identify candidate genes. We then assessed the effect of serine/threonine kinase 11 (STK11) knockout on pancreatic cancer by wound-healing assay, chick agnosia (CAM) assay, and orthotopic mouse pancreatic cancer model. We performed RNA sequence and Western blotting for mechanistic studies to identify and verify the pathways. After accelerated Transwell migration screening, STK11 was identified as one of the top candidate genes. Further experiments showed that targeted knockout of STK11 promoted the cell migration and increased liver metastasis in mice. Mechanistic analyses revealed that STK11 knockout influences blood vessel morphogenesis and is closely associated with the enhanced expression of phosphodiesterases (PDEs), especially PDE4D, PDE4B, and PDE10A. PDE4 inhibitor Roflumilast inhibited STK11-KO cell migration and tumor size, further demonstrating that PDEs are essential for STK11-deficient cell migration. Our findings support the adoption of therapeutic strategies, including Roflumilast, for patients with STK11-mutated pancreatic cancer in order to improve treatment efficacy and ultimately prolong survival.

MiRNAs in Lung Adenocarcinoma: Role, Diagnosis, Prognosis, and Therapy

Lung cancer has emerged as a significant public health challenge and remains the leading cause of cancer-related mortality worldwide. Among various types of lung malignancies, lung adenocarcinoma (LUAD) stands as the most prevalent form. MicroRNAs (miRNAs) play a crucial role in gene regulation, and their involvement in cancer has been extensively explored. While several reviews have been published on miRNAs and lung cancer, there remains a gap in the review regarding miRNAs specifically in LUAD. In this review, we not only highlight the potential diagnostic, prognostic, and therapeutic implications of miRNAs in LUAD, but also present an inclusive overview of the extensive research conducted on miRNAs in this particular context.

STK11 mutation impacts CD1E expression to regulate the differentiation of macrophages in lung adenocarcinoma

BACKGROUND

The deficiency of serine/threonine protein kinase 11 (STK11), one of the most common tumor suppressor genes in non-small-cell lung cancer, is a crucial player in tumor immune microenvironment regulation. This study attempted to unveil how mutated STK11 impact the differentiation of macrophages in lung adenocarcinoma (LUAD).

METHODS

STK11 and CD1E expression levels in different cell models were assessed by quantitative reverse transcription polymerase chain reaction. Western blot was utilized to detect the protein expression levels of STK11, CD1E, apoptosis markers, and AMPK signaling pathway markers after transfection treatment. Cell viability and macrophage differentiation were detected by CCK-8 and flow cytometry. Immunohistochemistry and immunofluorescence were employed to detect the expression of related genes and macrophage markers, respectively.

RESULTS

This study found that STK11 mutations promoted the proliferation of LUAD cells and inhibited the differentiation of M1 macrophages, apoptosis, and the AMPK signaling pathway. Mutated STK11 led to CD1E downregulation, which curbed the differentiation of M1 macrophages and hence promoted LUAD progression. It was further validated by the in vivo experimental results that STK11 mutation significantly decreased the immune infiltration of M1 macrophages and promoted LUAD progression.

CONCLUSION

It was revealed that STK11 mutation affected CD1E expression to regulate macrophage differentiation in LUAD and then promote tumor progression. In this way, CD1E could be a potential biological target for the therapeutic interventions of STK11-mutant LUAD patients. These findings also threw new light on a new therapeutic strategy for STK11-mutant tumor patients that assisted the macrophage polarization pathway.

Downregulation of a tumor suppressor gene LKB1 in lung transplantation as a biomarker for chronic murine lung allograft rejection

BACKGROUND

We recently demonstrated decreased tumor suppressor gene liver kinase B1 (LKB1) level in lung transplant recipients diagnosed with bronchiolitis obliterans syndrome. STE20-related adaptor alpha (STRADα) functions as a pseudokinase that binds and regulates LKB1 activity.

METHODS

A murine model of chronic lung allograft rejection in which a single lung from a B6D2F1 mouse was orthotopically transplanted into a DBA/2J mouse was employed. We examined the effect of LKB1 knockdown using CRISPR-CAS9 in vitro culture system.

RESULTS

Significant downregulation of LKB1 and STRADα expression was found in donor lung compared to recipient lung. STRADα knockdown significantly inhibited LKB1, pAMPK expression but induced phosphorylated mammalian target of rapamycin (mTOR), fibronectin, and Collagen-I, expression in BEAS-2B cells. LKB1 overexpression decreased fibronectin, Collagen-I, and phosphorylated mTOR expression in A549 cells.

CONCLUSIONS

We demonstrated that downregulation of LKB1-STRADα pathway accompanied with increased fibrosis, results in development of chronic rejection following murine lung transplantation.

Targeting KRASp.G12C Mutation in Advanced Non-Small Cell Lung Cancer: a New Era Has Begun

OPINION STATEMENT

KRASp.G12C mutation occurs in 12% of newly diagnosed advanced NSCLC and has recently emerged as a positive predictive biomarker for the selection of advanced NSCLC patients who may respond to novel KRASp.G12C inhibitors. The recent discovery of a new binding pocket under the effector region of KRAS G12C oncoprotein has made direct pharmacological inhibition of the KRASp.G12 mutation possible, leading to the clinical development of a new series of direct selective inhibitors, with a potential major impact on patients' survival and quality of life. Promising efficacy and tolerability data emerging from the early phase CodeBreak trial have already supported the regulatory approval of sotorasib as first in class targeted treatment for the second-line treatment of KRASp.G12C-positive NSCLC population, following immunotherapy-based first-line therapies, while the randomized phase III CodeBreak 200 clinical study has recently confirmed a significant superiority of sotorasib over docetaxel in terms of progression-free survival and quality of life. However, KRAS mutant NSCLC is a high heterogeneous disease characterized by a high rate of co-mutations, most frequently involving P53, STK11, and KEAP1 genes, which significantly modulate the composition of the tumor microenvironment and consequently affect clinical responses to both immunotherapy and targeted inhibitors now available in clinical practice. Both pre-clinical and clinical translational series have recently revealed a wide spectrum of resistance mechanisms occurring under selective KRASG12C inhibitors, including both on-target and off-target molecular alterations as well as morphological switching, negatively affecting the antitumor activity of these drugs when used as single agent therapies. The understanding of such biological background along with the emergence of pre-clinical data provided a strong rational to investigate different combination strategies, including the inhibition of SHP2, SOS1, and KRAS G12C downstream effectors, as well as the addition of immunotherapy and/or chemotherapy to targeted therapy. The preliminary results of these trials have recently suggested a promising activity of SHP2 inhibitors in the front-line setting, while toxicity issues limited the concurrent administration of immune-checkpoint inhibitors and sotorasib. The identification of predictive genomic/immunological biomarkers will be crucial to understand how to optimally sequencing/combining different drugs and ultimately personalize treatment strategies under clinical investigation, to definitively increase the survival outcomes of KRASp.G12C mutant advanced NSCLC patients.

Forward Genetic Screens as Tools to Investigate Role and Mechanisms of EMT in Cancer

Epithelial-mesenchymal transition (EMT) is a process of cellular plasticity regulated by complex signaling networks. Under physiological conditions, it plays an important role in wound healing and organ repair. Its importance for human disease is given by its central role in chronic fibroproliferative diseases and cancer, which represent leading causes of death worldwide. In tumors, EMT is involved in primary tumor growth, metastasis and therapy resistance. It is therefore a major requisite to investigate and understand the role of EMT and the mechanisms leading to EMT in order to tackle these diseases therapeutically. Forward genetic screens link genome modifications to phenotypes, and have been successfully employed to identify oncogenes, tumor suppressor genes and genes involved in metastasis or therapy resistance. In particular, transposon-based insertional mutagenesis screens and CRISPR-based screens are versatile and easy-to-use tools applied in recent years to discover and identify novel cancer-related mechanisms. Here, we review the contribution of forward genetic screens to our understanding of how EMT is regulated and how it is involved in various aspects of cancer. Based on the current literature, we propose these methods as additional tools to investigate EMT.

HECTD3 enhances cell radiation resistance and migration by regulating LKB1 mediated ZEB1 in glioma

Homologous to the E6-associated protein carboxyl terminus domain containing 3 (HECTD3) has been reported to play a role in carcinogenesis. Here, we explored the role of HECTD3 in regulating the radiation resistance of glioma, and the underlying mechanism. HECTD3 expressions in glioma tissues were assessed using Western blotting, qRT-PCR and immunohistochemistry. Glioma cells were exposed to 2, 4, 6 or 8Gy X-ray to mimic the radiation treatment. CCK-8, clone formation assay, flow cytometry assay, transwell chambers and animal assay were used to test cell viability, apoptosis, migration, invasiveness and tumorigenesis, respectively. HECTD3 expression was increased in glioma tissues, especially from patients with radiation resistance. Knockdown of HECTD3 promoted cell apoptosis and inhibited cell viability under the condition of 8Gy X-ray, as well as suppressed cell migration and invasiveness. In mechanism, HECTD3 positively regulated ZEB1 expression through regulating the ubiquitination of LKB1 protein. Overexpression of ZEB2 significantly abolished the effects of HECTD3 downregulation in inhibiting the radiation resistance and migration of glioma cells. Moreover, downregulation of HECTD3 further enhanced the anti-tumor effect of X-ray on glioma growth in vivo. In conclusion, HECTD3 was overexpressed in glioma patients with radiation resistance. Knockdown of HECTD3 sensitized glioma cells to radiation and inhibited cell migration by downregulating ZEB1 expression via regulating the ubiquitination of LKB1 protein. This study reveals that HECTD3 might be a potent target to enhance the radiation sensitivity of glioma.

MDM2-mediated ubiquitination of LKB1 contributes to the development of diabetic cataract

Diabetic cataract (DC) is a common complication of diabetes mellitus. The epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a crucial event in the development of DC. Murine double minute 2 (MDM2) is an E3 ubiquitin ligase that promotes EMT by regulating diverse targets. However, little is known about how MDM2 is involved in the pathogenesis of DC. We found the mRNA and protein levels of MDM2 were up-regulated in the lens of DC patients and rats. Thus, high glucose (HG)-induced human lens epithelial cells (HLECs) were constructed for further investigation. The results showed that the level of MDM2 was increased in HG-cultured HLECs, and the MDM2 knockdown alleviated HG-induced abnormal migration, EMT, and oxidative stress damage. Moreover, co-immunoprecipitation and ubiquitination assays demonstrated that MDM2 down-regulated LKB1 expression by ubiquitination degradation. LKB1 was found to be lower expressed in human and rat DC lenses, and HG-stimulated HLECs. Also, LKB1 overexpression mitigated HG-induced dysfunction of HLECs. Finally, our data showed that the changes related to EMT and oxidative stress induced by MDM2 knockdown were restored by down-regulation of LKB1. Together, MDM2 may involve in the pathogenesis of DC through down-regulating LKB1. MDM2 might be an effective therapeutical target of DC.

Role of STK11 in ALK‑positive non‑small cell lung cancer (Review)

Anaplastic lymphoma kinase (ALK) inhibitors have been shown to be effective in treating patients with ALK-positive non-small cell lung cancer (NSCLC), and crizotinib, ceritinib and alectinib have been approved as clinical first-line therapeutic agents. The availability of these inhibitors has also largely changed the treatment strategy for advanced ALK-positive NSCLC. However, patients still inevitably develop resistance to ALK inhibitors, leading to tumor recurrence or metastasis. The most critical issues that need to be addressed in the current treatment of ALK-positive NSCLC include the high cost of targeted inhibitors and the potential for increased toxicity and resistance to combination therapy. Recently, it has been suggested that the serine/threonine kinase 11 (STK11) mutation may serve as one of the biomarkers for immunotherapy in NSCLC. Therefore, the main purpose of this review was to summarize the role of STK11 in ALK-positive NSCLC. The present review also summarizes the treatment and drug resistance studies in ALK-positive NSCLC and the current status of STK11 research in NSCLC.

Unraveling the Role of STK11/LKB1 in Non-small Cell Lung Cancer

There are two major groups of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLCs can be further separated into three different categories: lung adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Pulmonary adenocarcinomas represent nearly half of all lung cancer cases and are known to be caused by smoking, certain occupational exposures, and specific genetic mutations. Scientists have noticed that most NSCLCs are driven by defects in the following genes: EGFR, BRAF, ALK, MET, and HER. Abnormalities in the STK11/LKB1 gene have also been shown to induce lung adenocarcinoma. LKB1-deficient cancer cells contain an overactive AMPK “energy sensor,” which inhibits cellular death and promotes glucose, lipid, and protein synthesis via the mTOR protein complex. Studies have also discovered that the loss of STK11/LKB1 favors oncogenesis by creating an immunosuppressive environment for tumors to grow and accelerate events such as angiogenesis, epithelial-mesenchymal transition (EMT), and cell polarity destabilization. STK11/LKB1-mutant lung cancers are currently treated with radiotherapy with or without chemotherapy. Recent clinical trials studying the effects of glutaminase inhibitors, mTOR inhibitors, and anti-PD-L1 therapy in lung cancer patients have yielded promising results. This narrative review provides an overview of the STK11/LKB1 gene and its role in cancer development. Additionally, a summary of the LKB1/APMK/mTOR is provided.

STK11/LKB1 Modulation of the Immune Response in Lung Cancer: From Biology to Therapeutic Impact

The STK11/LKB1 gene codes for liver kinase B1 (STK11/LKB1), a highly conserved serine/threonine kinase involved in many energy-related cellular processes. The canonical tumor-suppressive role for STK11/LKB1 involves the activation of AMPK-related kinases, a master regulator of cell survival during stress conditions. In pre-clinical models, inactivation of STK11/LKB1 leads to the progression of lung cancer with the acquisition of metastatic properties. Moreover, preclinical and clinical data have shown that inactivation of STK11/LKB1 is associated with an inert tumor immune microenvironment, with a reduced density of infiltrating cytotoxic CD8⁺ T lymphocytes, a lower expression of PD-(L)1, and a neutrophil-enriched tumor microenvironment. In this review, we first describe the biological function of STK11/LKB1 and the role of its inactivation in cancer cells. We report descriptive epidemiology, co-occurring genomic alterations, and prognostic impact for lung cancer patients. Finally, we discuss recent data based on pre-clinical models and lung cancer cohorts analyzing the results of STK11/LKB1 alterations on the immune system and response or resistance to immune checkpoint inhibitors.

Modulating Tumor Microenvironment: A Review on STK11 Immune Properties and Predictive vs Prognostic Role for Non-small-cell Lung Cancer Immunotherapy

OPINION STATEMENT

The quest for immunotherapy (IT) biomarkers is an element of highest clinical interest in both solid and hematologic tumors. In non-small-cell lung cancer (NSCLC) patients, besides PD-L1 expression evaluation with its intrinsic limitations, tissue and circulating parameters, likely portraying the tumor and its stromal/immune counterparts, have been proposed as potential predictors of IT responsiveness. STK11 mutations have been globally labeled as markers of IT resistance. After a thorough literature review, STK11 mutations condition the prognosis of NSCLC patients receiving ICI-containing regimens, implying a relevant biological and clinical significance. On the other hand, waiting for prospective and solid data, the putative negative predictive value of STK11 inactivation towards IT is sustained by less evidence. The physiologic regulation of multiple cellular pathways performed by STK11 likely explains the multifaceted modifications in tumor cells, stroma, and tumor immune microenvironment (TIME) observed in STK11 mutant lung cancer, particularly explored in the molecular subgroup of KRAS co-mutation. IT approaches available thus far in NSCLC, mainly represented by anti-PD-1/PD-L1 inhibitors, are not promising in the case of STK11 inactivation. Perceptive strategies aimed at modulating the TIME, regardless of STK11 status or specifically addressed to STK11-mutated cases, will hopefully provide valid therapeutic options to be adopted in the clinical practice.

Immunohistochemical and genetic characteristics of HPV-associated endocervical carcinoma with an invasive stratified mucin-producing carcinoma (ISMC) component

Invasive stratified mucin-producing carcinoma (ISMC) is a recently described entity of human papillomavirus (HPV)-associated endocervical adenocarcinoma with phenotypic plasticity and aggressive clinical behavior. To identify the cell of origin of ISMC, we investigated the immunohistochemical expression of cervical epithelial cell markers (CK7, PAX8, CK5/6, p63, and CK17), stemness markers (ALDH1 and Nanog), and epithelial-mesenchymal transition (EMT) markers (Snail, Twist, and E-cadherin) in 10 pure and mixed type ISMCs with at least 10% of ISMC component in the entire tumor, seven usual type endocervical adenocarcinomas (UEAs), and seven squamous cell carcinomas (SCCs). In addition, targeted sequencing was performed in 10 ISMCs. ISMC was significantly associated with larger tumor size (p = 0.011), more frequent lymphovascular invasion and lymph node metastasis (p < 0.001), higher FIGO stage (p = 0.022), and a tendency for worse clinical outcomes (p = 0.056) compared to other HPV-associated subtypes. ISMC showed negative or borderline positivity for PAX8, CK5/6, and p63, which were distinct from UEA and SCC (p < 0.01). Compared to UEA and SCC, ISMC showed higher expression for ALDH1 (p = 0.119 for UEA and p = 0.009 for SCC), Snail (p = 0.036), and Twist (p = 0.119), and tended to show decreased E-cadherin expression (p = 0.083). In next-generation sequencing analysis, ISMC exhibited frequent STK11, MET, FANCA, and PALB2 mutations compared to conventional cervical carcinomas, and genes related to EMT and stemness were frequently altered. EMT-prone and stemness characteristics and peripheral expression of reserve cell and EMT markers of ISMC suggest its cervical reserve cell origin. We recommend PAX8, CK5/6, and p63 as diagnostic triple biomarkers for ISMC. These findings highlight the distinct biological basis of ISMC.

STK11 loss drives rapid progression in a breast cancer patient resulting in pulmonary tumor thrombotic microangiopathy

We experienced a case of breast cancer in which liver metastases spread rapidly and the patient died of pulmonary tumor thrombotic microangiopathy (PTTM). PTTM is a fatal cancer-associated respiratory complication disease. To reveal genetic alterations of the clinical course, we performed next generation sequencing of the serial specimens using the Ion AmpliSeqTM Comprehensive Cancer Panel and RNA sequencing for transcriptomic data, followed by gene set analysis. The analysis revealed an oncogenic TP53 R213* mutation in all specimens and STK11 loss in tissues sampled after disease progression. Immunohistochemistry with an anti-STK11 antibody confirmed no STK11 expression in the samples after progression. Transcriptome analysis showed a significant downregulation of proteins associated with apoptosis in the specimens with STK11 loss. STK11 loss may have triggered the rapid progression of PTTM from a comprehensive genomic analysis.

The role of HPV gene expression and selected cellular MiRNAs in lung cancer development

BACKGROUND

The high mortality rate of lung cancer can be justified that strong need to explore new aspect of tumor biology. Human papillomavirus (HPV) has been detected as risk factor for the development of lung cancer. The aim of this study was to determine the role of HPV and cellular/miRNAs genes expression in the epithelial-mesenchymal transition (EMT) and development of lung cancer.

METHODS

In this case-control study, 109 lung cancer tissue and 52 controls were included. We analyzed the presence of HPV infection, its genotypes (in positive samples) and the expression of viral genes (E2, E6 and E7). Also, We examined the expression of celluar factors including (a) p53 and retinoblastoma (Rb) (as anti-carcinogenic genes), (b) EMT related genes, (c) selected miRNAs.

RESULTS

Our results reported 51.4% and 23.1% of HPV genome in tumor tissues and control tissues samples, respectively. There was a significant association between the HPV positive status and lung cancer (OR = 3.26, 95% C.I = 1.47-7.02, P = 0.001). HPV type 16 was the most prevalent genotype in tissues. The expression of p53, RB, TIMP1, CCNG-1, E-cad and PTPN13 were decreased while MMP-2 and N-cad were increased in HPV-positive tumor/control tissues compared to HPV-negative tissues. Also, among miRNAs, let-7, miR-23, miR-34, miR-125, miR-146 were downregulated and miR-20, miR-424 were upregulated in HPV-positve tissues compared to HPV-negative tissues.

CONCLUSION

This study demonstrated that HPV infection and interaction with cellular genes and miRNAs promote EMT which involved in the lung cancer development.

Beyond LKB1 Mutations in Non-Small Cell Lung Cancer: Defining LKB1less Phenotype to Optimize Patient Selection and Treatment

LKB1 is frequently mutated in non-small cell lung cancer (NSCLC). LKB1-mutated NSCLCs often have a dismal prognosis and receive lower benefit from the currently available therapies. LKB1 acts as a cell emergency brake in low-energy conditions, by modulating the activity of crucial anabolic enzymes. Thus, loss of LKB1 activity leads to the enhancement of tumor cell proliferation also under conditions of energy shortage. This unrestrained growth may be exploited as an Achilles heel in NSCLC, i.e., by inhibiting mitochondrial respiration. Recently, clinical trials have started to investigate the efficacy of metabolism-based treatments in NSCLCs. To date, enrollment of patients within these trials is based on LKB1 loss of function status, defined by mutation in the gene or by complete absence of immunohistochemical staining. However, LKB1 impairment could be the consequence of epigenetic regulations that partially or completely abrogate protein expression. These epigenetic regulations result in LKB1 wild-type tumors with aggressiveness and vulnerabilities similar to those of LKB1-mutated ones. In this review, we introduced the definition of the “LKB1less phenotype”, and we summarized all currently known features linked to this status, in order to optimize selection and treatment of NSCLC patients with impaired LKB1 function.

The Key Role of IP6K: A Novel Target for Anticancer Treatments?

Inositol and its phosphate metabolites play a pivotal role in several biochemical pathways and gene expression regulation: inositol pyrophosphates (PP-IPs) have been increasingly appreciated as key signaling modulators. Fluctuations in their intracellular levels hugely impact the transfer of phosphates and the phosphorylation status of several target proteins. Pharmacological modulation of the proteins associated with PP-IP activities has proved to be beneficial in various pathological settings. IP₇ has been extensively studied and found to play a key role in pathways associated with PP-IP activities. Three inositol hexakisphosphate kinase (IP₆K) isoforms regulate IP₇ synthesis in mammals. Genomic deletion or enzymic inhibition of IP₆K1 has been shown to reduce cell invasiveness and migration capacity, protecting against chemical-induced carcinogenesis. IP₆K1 could therefore be a useful target in anticancer treatment. Here, we summarize the current understanding that established IP₆K1 and the other IP₆K isoforms as possible targets for cancer therapy. However, it will be necessary to determine whether pharmacological inhibition of IP₆K is safe enough to begin clinical study. The development of safe and selective inhibitors of IP₆K isoforms is required to minimize undesirable effects.

STK11 (LKB1) missense somatic mutant isoforms promote tumor growth, motility and inflammation

Elucidating the contribution of somatic mutations to cancer is essential for personalized medicine. STK11 (LKB1) appears to be inactivated in human cancer. However, somatic missense mutations also occur, and the role/s of these alterations to this disease remain unknown. Here, we investigated the contribution of four missense LKB1 somatic mutations in tumor biology. Three out of the four mutants lost their tumor suppressor capabilities and showed deficient kinase activity. The remaining mutant retained the enzymatic activity of wild type LKB1, but induced increased cell motility. Mechanistically, LKB1 mutants resulted in differential gene expression of genes encoding vesicle trafficking regulating molecules, adhesion molecules and cytokines. The differentially regulated genes correlated with protein networks identified through comparative secretome analysis. Notably, three mutant isoforms promoted tumor growth, and one induced inflammation-like features together with dysregulated levels of cytokines. These findings uncover oncogenic roles of LKB1 somatic mutations, and will aid in further understanding their contributions to cancer development and progression.

Paula Granado-Martínez, Sara Ortega, Elena González-Sánchez et al. report a functional analysis of four cancer-associated mutant isoforms of the gene STK11 using cell-based and animal models. They find the mutant isoforms no longer show tumor suppressor activity, promote tumor growth, and affect the regulation of cytokines and genes involved in vesicle trafficking.

A non-proliferative role of pyrimidine metabolism in cancer

Background

Nucleotide metabolism is a critical pathway that generates purine and pyrimidine molecules for DNA replication, RNA synthesis, and cellular bioenergetics. Increased nucleotide metabolism supports uncontrolled growth of tumors and is a hallmark of cancer. Agents inhibiting synthesis and incorporation of nucleotides in DNA are widely used as chemotherapeutics to reduce tumor growth, cause DNA damage, and induce cell death. Thus, the research on nucleotide metabolism in cancer is primarily focused on its role in cell proliferation. However, in addition to proliferation, the role of purine molecules is established as ligands for purinergic signals. However, so far, the role of the pyrimidines has not been discussed beyond cell growth.

Scope of the review

In this review we present the key evidence from recent pivotal studies supporting the notion of a non-proliferative role for pyrimidine metabolism (PyM) in cancer, with a special focus on its effect on differentiation in cancers from different origins.

Major conclusion

In leukemic cells, the pyrimidine catabolism induces terminal differentiation toward monocytic lineage to check the aberrant cell proliferation, whereas in some solid tumors (e.g., triple negative breast cancer and hepatocellular carcinoma), catalytic degradation of pyrimidines maintains the mesenchymal-like state driven by epithelial-to-mesenchymal transition (EMT). This review further broadens this concept to understand the effect of PyM on metastasis and, ultimately, delivers a rationale to investigate the involvement of the pyrimidine molecules as oncometabolites. Overall, understanding the non-proliferative role of PyM in cancer will lead to improvement of the existing antimetabolites and to development of new therapeutic options.

MiR-590-3p regulates proliferation, migration and collagen synthesis of cardiac fibroblast by targeting ZEB1

Previous studies have implicated the attractive and promising role of miR‐590‐3p to restore the cardiac function following myocardial infarction (MI). However, the molecular mechanisms for how miR‐590‐3p involves in cardiac fibrosis remain largely unexplored. Using human cardiac fibroblasts (HCFs) as the cellular model, luciferase report assay, mutation, EdU assay and transwell migration assay were applied to investigate the biological effects of miR‐590‐3p on the proliferation, differentiation, migration and collagen synthesis of cardiac fibroblasts. We found that miR‐590‐3p significantly suppressed cell proliferation and migration of HCFs. The mRNA and protein expression levels of α‐SMA, Col1A1 and Col3A were significantly decreased by miR‐590‐3p. Moreover, miR‐590‐3p directly targeted at the 3’UTR of ZEB1 to repress the translation of ZEB1. Interfering with the expression of ZEB1 significantly decreased the cell proliferation, migration activity, mRNA and protein expressions of α‐SMA, Col1A1 and Col3A. Furthermore, the expressions of miR‐590‐3p and ZEB1 were identified in infarct area of MI model in pigs. Collectively, miR‐590‐3p suppresses the cell proliferation, differentiation, migration and collagen synthesis of cardiac fibroblasts by targeting ZEB1. These works will provide useful biological information for future studies on potential roles of miR‐590‐3p as the therapeutic target to recover cardiac function following MI.

Involvement of E-cadherin/AMPK/mTOR axis in LKB1-induced sensitivity of non-small cell lung cancer to gambogic acid

Liver kinase B1 (LKB1) is a tumor suppressor that functions as master regulator of cell growth, metabolism, survival, and polarity. Patients with NSCLC possessing mutated LKB1 respond to chemotherapy differently from those with wild-type LKB1. Gambogic acid (GA), a small molecule from natural product, has been established as an anti-tumor agent due to its potent activity and low toxicity. Here, we find out that NSCLC cells with wild-type LKB1 are more sensitive to GA in vitro and in vivo. Mechanistic studies pinpoint that the selective inhibition of mTOR signaling confers the stronger suppression of NSCLC in presence of wild-type LKB1, which is involved in the enhancement of p-AMPK. Further studies reveal that GA increases p-AMPK levels through up-regulation of E-cadherin associated with LKB1. In addition, induction of E-cadherin by GA may be through down-regulation of ZEB1, which is independent with LKB1 status. Hence, our findings support that enhanced E-cadherin by GA cooperates LKB1, leading to up-regulation of p-AMPK, and thus blocking of mTOR signaling pathway, which provide theoretical foundation for utilization of GA as a potential targeted drug against NSCLC harboring wild-type LKB1.

Loss of FGL1 induces epithelial‑mesenchymal transition and angiogenesis in LKB1 mutant lung adenocarcinoma

Liver kinase b1 (LKB1) is a tumor suppressor, and the inactivated mutation frequency of LKB1 in lung adenocarcinoma is ~20%. The present study aimed to explore potential novel biomarkers in LKB1 mutant lung adenocarcinoma. Gene expression data from lung adenocarcinoma patients were downloaded from The Cancer Genome Atlas and the Gene Expression Omnibus databases. R software was used to analyze the gene expression profiles. Reverse transcription‑quantitative PCR (RT‑qPCR), western blot and immunohistochemistry (IHC) analyses were used to examine gene expression and function. Gene function was further explored via gene set enrichment analysis. A colony formation assay was used to evaluate cell proliferation. A wound‑healing assay and immunofluorescence analysis were used to evaluate cell migration and epithelial‑mesenchymal transition (EMT), respectively. Wound healing assay, immunofluorescence, western blot, RT‑qPCR and IHC results for EMT‑associated markers demonstrated that a loss of fibrinogen‑like 1 (FGL1) induced EMT in LKB1 mutant lung adenocarcinoma. RT‑qPCR and IHC analyses of angiogenesis‑related markers revealed that loss of FGL1 promoted angiogenesis in LKB1 mutant lung adenocarcinoma. Overall, the present results demonstrated that loss of FGL1 induced EMT and angiogenesis in LKB1 mutant lung adenocarcinoma. FGL1 may be a novel biomarker to indicate EMT and angiogenesis in patients with LKB1 mutant lung adenocarcinoma.

Plumbagin promotes human hepatoma SMMC-7721 cell apoptosis via caspase-3/vimentin signal-mediated EMT

Background/aims

Plumbagin (PL) has been shown to effectively inhibit tumor growth and migration of hepatocellular carcinoma cells in previous studies, but the specific mechanism for this remains unclear. The purpose of this study was to investigate the effects of PL-induced apoptosis in epithelial–mesenchymal transition (EMT) of human hepatocellular carcinoma (HCC) in vivo and in vitro.

Methods

SMMC-7721 cells were cultured, an EMT model was induced in vitro by TGF-β1, cell proliferation was detected by the MTT assay, cell invasion was analyzed by the Transwell invasion assay, and the apoptosis rate was measured by flow cytometry. RT-PCR was used to detect vimentin, E-cadherin, N-cadherin and snail mRNA, and Western blotting was used to detect the vimentin, caspase-3, PARP-1, E-cadherin, N-cadherin and snail protein expression levels. HE staining and TUNEL staining, immunohistochemistry and immunofluorescence were used to detect the expression levels of bax and bcl-2 in hepatocarcinoma xenografts and to evaluate their apoptosis in vivo.

Results

The in vitro results showed that PL inhibited the proliferation of EMT model cells, increased the apoptosis rate of the EMT model, and significantly decreased the vimentin, PARP-1, N-cadherin and snail protein levels, but significantly increased E-cadherin and caspase-3 protein expression. In addition, the in vivo results indicated that PL can affect the expression of bax/bcl-2 apoptotic marker proteins.

Conclusion

PL may induce apoptosis of human hepatocellular carcinoma cells undergoing epithelial–mesenchymal transition by increasing the caspase-3 protein level and cleaving vimentin.

Effect of asiatic acid on epithelial-mesenchymal transition of human alveolar epithelium A549 cells induced by TGF-β1

Asiatic acid (AA) is a pentacyclic triterpenoid isolated from Centella asiatica (L.) Urban that possesses significant antitumor activities. In the present study, the mechanism of AA on transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) was investigated in the lung cancer cell line A549. To do so, cell morphological alterations were observed and recorded at different time periods. Cells treated with TGF-β1 were spindle-shaped and characterized as stromal cells, whereas AA-treated cells exhibited epithelial cell characteristics and increased intercellular adhesion. The MTT assay demonstrated that the high concentration of AA inhibited the viability of A549 cells treated with TGF-β. In addition, the wound healing and Transwell assays revealed that AA inhibited TGF-β1-induced invasion and migration of A549 cells. Furthermore, AA treatment increased the mRNA and protein expression levels of E-cadherin, and decreased the expression levels of snail family transcriptional repressor (Snail), N-cadherin, vimentin and β-catenin in TGF-β1-treated A549 cells. In conclusion, these results suggested that AA may inhibit TGF-β1-induced EMT in lung cancer through increased expression of E-cadherin, and inhibition of Snail, N-cadherin and vimentin expression.

Long non-coding RNA MIAT competitively binds miR-150-5p to regulate ZEB1 expression in osteosarcoma

Long non-coding RNAs (LncRNAs), are significant in a number of biological stages and illnesses. The myocardial infarction associated transcript (MIAT) serves a function in numerous types of illness and physiological and pathological processes, including paranoid schizophrenia, diabetic retinopathy, myocardial infarction and neuroendocrine prostate cancer. However, the function of the lncRNA MIAT in the development of osteosarcoma is unknown. It has been identified that during the development of osteosarcoma, MIAT is upregulated in tumor tissues compared to adjacent non-tumor tissues. The spreading and proliferation of osteosarcoma cells was reduced by MIAT knockdown. These findings indicate that MIAT functions by competing with critical RNAs to target miR-150-5p and activate zinc finger E-box binding homeobox 1 to modulate the function of osteosarcoma cells. Together, the present findings may contribute to the understanding of the pathogenesis of osteosarcoma.

EMT induced by loss of LKB1 promotes migration and invasion of liver cancer cells through ZEB1-induced YAP signaling

Liver cancer cells often exhibit mesenchymal phenotypes, a critical phenotypic alteration of cancer cells termed the epithelial-mesenchymal transition (EMT). To examine whether liver kinase B1 (LKB1) serves a potential role in EMT in liver carcinogenesis, in the present study, it was determined that the expression of LKB1 decreased in the hepatocellular carcinoma (HCC) cell line, compared with a normal liver cell line. LKB1 overexpression decreased cell motility and invasiveness. Furthermore, the loss of LKB1 induced the expression of several EMT marker proteins, including that of Zinc Finger E-Box Binding Homeobox 1 (ZEB1). Notably, the expression of Yes-associated protein (YAP) was positively associated with that of ZEB1 in LKB1-knockdown cells with a mesenchymal phenotype. Here, we describe the direct regulation of the Hippo pathway effector YAP by ZEB1. The findings of the present study demonstrate that ZEB1 regulates the expression of YAP and regulates the expression of downstream target genes to promote malignant progression.

Comparative Proteomics of Chromium-Transformed Beas-2B Cells by 2D-DIGE and MALDI-TOF/TOF MS

Chromium (Cr) is a highly toxic, common heavy metal used in industrial production. There are two types of Cr in nature: hexavalent chromium (Cr(VI)) and chromium trichloride (Cr(III)). Cr(III) is involved in the metabolism of sugars and lipids, whereas Cr(VI) is absorbed through the respiratory tract and skin and generates free radicals that result in secondary toxicity. Cr(VI) leads to cancer in the occupational population and is therefore recognized as a human carcinogen by the International Agency for Research on Cancer. The specific mechanism underlying Cr-induced carcinogenesis is complex. In this study, two-dimensional fluorescence difference gel electrophoresis and matrix-assisted laser desorption ionization-time-of-flight/time-of-flight mass spectrometry-based techniques were performed to analyze differentially expressed proteins between Beas-2B human bronchial epithelial cells and Cr(VI)-transformed Beas-2B cells. Many differentially expressed proteins were identified in the cells after malignant transformation, including serine/threonine kinase 11, endothelial nitric oxide synthase 3, apolipoprotein A1, vinculin, and lamin A/C. These proteins are involved in many signaling and metabolic pathways, including apoptosis, autophagy, the PI3K/Akt signaling pathway, focal adhesion, cell motility, and actin cytoskeleton rearrangement.

Increased expression of monoamine oxidase A is associated with epithelial to mesenchymal transition and clinicopathological features in non-small cell lung cancer

Monoamine oxidase A (MAOA), a mitochondrial enzyme, is closely associated with neurological disorders. Recently, MAOA has been linked to the progression of prostate cancer, hepatocellular carcinoma, and cholangiocarcinoma. However, MAOA was reported to have different effects on the progression of these types of cancer, and the role of MAOA in non-small cell lung cancer (NSCLC) progression remains unclear. The present study determined the expression of MAOA and epithelial to mesenchymal transition (EMT) markers in 45 pairs of NSCLC and matched non-tumor adjacent lung tissues, and further analyzed the correlation between MAOA expression and the EMT or the development of clinicopathological features. The results demonstrated that protein and mRNA expression levels of MAOA in NSCLC tissues were higher than those observed in the matched non-tumor adjacent lung tissues. Furthermore, the increased MAOA expression in NSCLC tissues was positively correlated with N-cadherin (r=0.525, P=0.002), Slug (r=0.515, P=0.001), and Twist (r=0.448, P=0.008) expressions, but negatively correlated with E-cadherin expression (r=-0.387, P=0.01). Additionally, the elevated MAOA expression in NSCLC tissues was associated with late stage NSCLC (Z=-2.596, P=0.029) and lymph node metastases (Z=-2.378, P=0.020). These findings suggest that MAOA may have a role in promoting NSCLC progression by mediating EMT.

Integration of pan-cancer transcriptomics with RPPA proteomics reveals mechanisms of epithelial-mesenchymal transition

Integrating data from multiple regulatory layers across cancer types could elucidate additional mechanisms of oncogenesis. Using antibody-based protein profiling of 736 cancer cell lines, along with matching transcriptomic data, we show that pan-cancer bimodality in the amounts of mRNA, protein, and protein phosphorylation reveals mechanisms related to the epithelial-mesenchymal transition (EMT). Based on the bimodal expression of E-cadherin, we define an EMT signature consisting of 239 genes, many of which were not previously associated with EMT. By querying gene expression signatures collected from cancer cell lines after small-molecule perturbations, we identify enrichment for histone deacetylase (HDAC) inhibitors as inducers of EMT, and kinase inhibitors as mesenchymal-to-epithelial transition (MET) promoters. Causal modeling of protein-based signaling identifies putative drivers of EMT. In conclusion, integrative analysis of pan-cancer proteomic and transcriptomic data reveals key regulatory mechanisms of oncogenic transformation.

Profiling molecular and phenotypic characteristics of large collections of cancer cell lines can be used to identify distinct and common oncogenic pathways across cancer types. So far, most large-scale data obtained from cancer cell lines have been at the genomic, transcriptomic, and phenotypic levels. Recently, high-quality data at the level of cell signaling through protein abundances and phosphorylation sites has become available. By integrating this newly generated protein data with prior transcriptomic data, and by visualizing all cancer cell lines using dimensionality reduction techniques, pan-cancer cell lines are strikingly shown to organize into a gradient of epithelial to mesenchymal types. Interestingly, many of the measured proteins and transcripts display bimodality; the expression of genes, proteins, and protein phosphorylations is either high or low, strongly suggesting that they act as molecular switches. Focusing on further characterizing molecular switches of epithelial-mesenchymal transitions, we identify candidate regulators and small molecules that can induce or reverse such transition, as well as potential causal relationships between proteins. Since the mesenchymal state of tumors is known to be associated with metastasis and later-stage cancer development, better understanding the regulatory mechanisms of epithelial-to-mesenchymal transition can lead to improved targeted therapeutics.

LKB1 loss cooperating with BRAF V600E promotes melanoma cell invasion and migration by up-regulation MMP-2 via PI3K/Akt/mTOR pathway

The serine/threonine kinase LKB1, act as a tumor suppressor, has been reported in several sporadic cancers. However, how the loss of LKB1 promotes melanoma invasion and metastasis remains incompletely understood. In this study, we inactivated LKB1expression by RNA interference in BRAF mutation and wild type melanoma cells respectively. We found LKB1 inactivation cooperate with BRAF V600E lead to melanoma cells more aggressive by a series of experiments including wound scratch test, Transwell assay. While single alteration, either LKB1 loss or BRAF V600E, fails to enhance melanoma cells invasion ability. Mechanistically, LKB1 loss synergism with BRAF V600E resulted in the activation of the PI3K/Akt/mTOR signaling pathway and significant up-regulation expression of MMP-2. In addition, LKB1 expression in human melanoma tissues was negatively associated with MMP-2 expression in the presence of BRAF V600E. Thus, our findings indicate a probable explanation on LKB1 function as a tumor suppressor in melanoma and a new therapeutic strategy for melanoma by targeting on BRAF and LKB1 together.

Liver kinase B1 restoration promotes exosome secretion and motility of lung cancer cells

Liver kinase B1 (LKB1) regulates a variety of cellular functions, including cell polarity, energy metabolism and cell growth, by targeting multiple signaling pathways such as AMPK/mTOR and p53. LKB1 functions as a tumor suppressor in sporadic cancers including lung cancer. Extracellular vesicles such as exosomes secreted by cancer cells modulate the tumor microenvironment and progression by targeting both tumor cells (autocrine actions) and other types of cells associated with tumors (paracrine actions). While the roles of LKB1 in cellular signaling in general is well-studied, its specific role in exosome-mediated signaling remains to be explored. To this purpose, we reintroduced LKB1 into H460 and A549 lung cancer cells that are endogenously deficient in LKB1 expression. Notably, we found that while restoration of LKB1 significantly reduced lung cancer cell growth as expected, it greatly promoted cell motility and enhanced the release of exosomes. In addition, exosomes isolated from H460 cells with stable restoration of LKB1 had much higher ability in stimulating lung cancer cell migration than did those from H460 cells lacking LKB1. Mechanistically, restoration of LKB1 in H460 cells inhibited cellular expression and exosomal secretion of migration-suppressing microRNAs (miRNAs), including miR-125a, miR-126 and let7b. Taken together, the present study revealed a new role for LKB1 in promoting cell motility by downregulating migration-suppressing miRNA expression and exosome secretion.

Honokiol activates LKB1-miR-34a axis and antagonizes the oncogenic actions of leptin in breast cancer

Leptin, a major adipocytokine produced by adipocytes, is emerging as a key molecule linking obesity with breast cancer therefore, it is important to find effective strategies to antagonize oncogenic effects of leptin to disrupt obesity-cancer axis. Here, we examine the potential of honokiol (HNK), a bioactive polyphenol from Magnolia grandiflora, as a leptin-antagonist and systematically elucidate the underlying mechanisms. HNK inhibits leptin-induced epithelial-mesenchymal-transition (EMT), and mammosphere-formation along with a reduction in the expression of stemness factors, Oct4 and Nanog. Investigating the downstream mediator(s), that direct leptin-antagonist actions of HNK; we discovered functional interactions between HNK, LKB1 and miR-34a. HNK increases the expression and cytoplasmic-localization of LKB1 while HNK-induced SIRT1/3 accentuates the cytoplasmic-localization of LKB1. We found that HNK increases miR-34a in LKB1-dependent manner as LKB1-silencing impedes HNK-induced miR-34a which can be rescued by LKB1-overexpression. Finally, an integral role of miR-34a is discovered as miR-34a mimic potentiates HNK-mediated inhibition of EMT, Zeb1 expression and nuclear-localization, mammosphere-formation, and expression of stemness factors. Leptin-antagonist actions of HNK are further enhanced by miR-34a mimic whereas miR-34a inhibitor results in inhibiting HNK's effect on leptin. These data provide evidence for the leptin-antagonist potential of HNK and reveal the involvement of LKB1 and miR-34a.

5'-AMP-Activated Protein Kinase Regulates Papillary (TPC-1 and BCPAP) Thyroid Cancer Cell Survival, Migration, Invasion, and Epithelial-to-Mesenchymal Transition

BACKGROUND

Differentiated thyroid carcinomas (DTC) are associated with a good prognosis and a high survival rate. However, tumor recurrence occurs in approximately 20-30% of DTC patients, reinforcing the importance of identifying new molecular targets for cancer management. It has been shown that the 5'-AMP-activated protein kinase (AMPK) is over-activated in papillary thyroid cancer (PTC). This study aimed to investigate the effects of 5-aminoimidazole-4-carboxamide-ribonucleoside (AICAR), an AMPK activator, on various aspects of thyroid cancer cell behavior, including cell survival, apoptosis, migration, invasion, and epithelial-to-mesenchymal transition (EMT), in the human thyroid cancer cell lines BCPAP and TPC-1.

METHODS

BCPAP and TPC-1 cells were cultivated in Dulbecco's modified Eagle's medium, and the non-tumor-derived cell line Nthy-ORI was grown in RPMI. Cells were treated or not with AICAR for different periods of time. The cell growth rate, cell cycle phase, apoptosis, cell migration, and invasion were analyzed using transwell inserts, and EMT was quantified by the expression of mesenchymal and epithelial markers.

RESULTS

AMPK is activated in thyroid cancer cell lines, and AICAR treatment further increased AMPK phosphorylation. After 48 hours of AICAR treatment, the percentage of cells in the G2/M phase decreased, and a G0/G1-phase arrest was induced in both cell lines. AMPK activation effectively induced apoptosis in the BCPAP and TPC-1 cancer cell lines, while no apoptosis induction was observed in Nthy-ORI cells. AICAR also reduced the migration of Nthy-ORI and BCPAP cells by 30% and approximately 60% in TPC-1 cells. AICAR had no effect on cell invasion in Nthy-ORI and TPC-1 cells, but a significant reduction of cell invasion was observed in BCPAP cells. AICAR induced a significant reduction of N-cadherin and no changes in the expression of vimentin or TCF/Zeb1 protein in BCPAP cells. No differences in the expression of EMT markers were found in the AICAR-treated Nthy-ORI cells. A remarkable reduction of vimentin, TCF/Zeb1, and N-cadherin protein expression was detected in the TPC-1 cells.

CONCLUSIONS

Increased activation of AMPK in PTC cell lines leads to a strong antitumor response, as measured by the inhibition of cell proliferation, cell migration, and induction of cell death. AMPK activation also reverses EMT in TPC-1 cells.

Attenuated LKB1-SIK1 signaling promotes epithelial-mesenchymal transition and radioresistance of non-small cell lung cancer cells

Background

Radiotherapy is one of the main therapeutic approaches for non–small cell lung cancer (NSCLC). However, radioresistant cancer cells can eventually cause tumor relapse and even fatal metastasis. It is thought that radioresistance and metastasis could be potentially linked by epithelial-mesenchymal transition (EMT). In this study, we established radioresistant NSCLC cells to investigate the potential relationship among radioresistance, EMT, and enhanced metastatic potential and the underlying mechanism involving liver kinase B1 (LKB1)-Salt-inducible kinase 1 (SIK1) signaling.

Methods

The radioresistant cell lines A549R and H1299R were generated by dose-gradient irradiation of the parental A549 and H1299 cells. The radioresistance/sensitivity was evaluated by Cell Counting Kit-8 assay, apoptosis analysis, and/or clonogenic cell survival assay. The EMT phenotype and the signaling change were assessed by Western blotting. The abilities of invasion and migration were evaluated by transwell assays and wound healing assays.

Results

The radioresistant cell lines A549R and H1299R displayed mesenchymal features with enhanced invasion and migration. Mechanistically, A549R and H1299R cells had attenuated LKB1-SIK1 signaling, which leaded to the up-regulation of Zinc-finger E-box-binding homeobox factor 1 (ZEB1)—a transcription factor that drives EMT. Re-expression of LKB1 in A549R cells reversed the EMT phenotype, whereas knockdown of LKB1 in H1299R cells further promoted the EMT phenotype. Moreover, re-expression of LKB1 in A549 cells increased the radiosensitivity, whereas knockdown of LKB1 in H1299 cells decreased the radiosensitivity.

Conclusions

Our findings suggest that attenuated LKB1-SIK1 signaling promotes EMT and radioresistance of NSCLC cells, which subsequently contributes to the enhanced metastatic potential. Targeting the LKB1-SIK1-ZEB1 pathway to suppress EMT might provide therapeutic benefits.

LKB1 kinase-dependent and -independent defects disrupt polarity and adhesion signaling to drive collagen remodeling during invasion

LKB1 is a serine/threonine kinase and a commonly mutated gene in lung adenocarcinoma. The majority of LKB1 mutations are truncations that disrupt its kinase activity and remove its C-terminal domain (CTD). Because LKB1 inactivation drives cancer metastasis in mice and leads to aberrant cell invasion in vitro, we sought to determine how compromised LKB1 function affects lung cancer cell polarity and invasion. Using three-dimensional models, we show that LKB1 kinase activity is essential for focal adhesion kinase-mediated cell adhesion and subsequent collagen remodeling but not cell polarity. Instead, cell polarity is overseen by the kinase-independent function of its CTD and more specifically its farnesylation. This occurs through a mesenchymal-amoeboid morphological switch that signals through the Rho-GTPase RhoA. These data suggest that a combination of kinase-dependent and -independent defects by LKB1 inactivation creates a uniquely invasive cell with aberrant polarity and adhesion signaling that drives invasion into the microenvironment.

Energy sensing and cancer: LKB1 function and lessons learnt from Peutz-Jeghers syndrome

We describe in this review increasing evidence that loss of LKB1 kinase in Peutz-Jeghers syndrome (PJS) derails the existing natural balance between cell survival and tumour growth suppression. LKB1 deletion can plunge cells into an energy/oxidative stress-induced crisis which leads to the activation of alternative and often carcinogenic pathways to maintain cellular energy levels. It therefore appears that although LKB1 deficiency can suppress oncogenic transformation in the short term, it can ultimately lead to more progressed and malignant phenotypes by driving abnormal cell differentiation, genomic instability and increased tumour heterogeneity.

Tumor progression, metastasis, and modulators of epithelial-mesenchymal transition in endometrioid endometrial carcinoma: an update

Endometrioid endometrial carcinoma (EEC), also known as type 1 endometrial cancer (EC), accounts for over 70-80% of all cases that are usually associated with estrogen stimulation and often develops in a background of atypical endometrial hyperplasia. The increased incidence of EC is mainly confined to this type of cancer. Most EEC patients present at an early stage and generally have a favorable prognosis; however, up to 30% of EEC present as high risk tumors, which have invaded deep into the myometrium at diagnosis and progressively lead to local or extra pelvic metastasis. The poor survival of advanced EC is related to the lack of effective therapies, which can be attributed to poor understanding of the molecular mechanisms underlying the progression of disease toward invasion and metastasis. Multiple lines of evidence illustrate that epithelial-mesenchymal transition (EMT)-like events are central to tumor progression and malignant transformation, endowing the incipient cancer cell with invasive and metastatic properties. The aim of this review is to summarize the current knowledge on molecular events associated with EMT in progression, invasion, and metastasis of EEC. Further, the role of epigenetic modifications and microRNA regulation, tumor microenvironment, and microcystic elongated and fragmented glands like invasion pattern have been discussed. We believe this article may perhaps stimulate further research in this field that may aid in identifying high risk patients within this clinically challenging patient group and also lead to the recognition of novel targets for the prevention of metastasis - the most fatal consequence of endometrial carcinogenesis.

Honokiol, an Active Compound of Magnolia Plant, Inhibits Growth, and Progression of Cancers of Different Organs

Honokiol (C₁₈H₁₈O₂) is a biphenolic natural product isolated from the bark and leaves of Magnolia plant spp. During the last decade or more, honokiol has been extensively studied for its beneficial effect against several diseases. Investigations have demonstrated that honokiol possesses anti-carcinogenic, anti-inflammatory, anti-oxidative, anti-angiogenic as well as inhibitory effect on malignant transformation of papillomas to carcinomas in vitro and in vivo animal models without any appreciable toxicity. Honokiol affects multiple signaling pathways, molecular and cellular targets including nuclear factor-κB (NF-κB), STAT3, epidermal growth factor receptor (EGFR), cell survival signaling, cell cycle, cyclooxygenase and other inflammatory mediators, etc. Its chemopreventive and/or therapeutic effects have been tested against chronic diseases, such as cancers of different organs. In this chapter, we describe and discuss briefly the effect of honokiol against cancers of different organs, such as melanoma, non-melanoma, lung, prostate, breast, head and neck squamous cell carcinoma, urinary bladder cancer, gastric cancer, and neuroblastoma, etc. and describe its mechanism of action including various molecular and cellular targets. Although more rigorous in vivo studies are still needed, however it is expected that therapeutic effects and activities of honokiol may help in the development and designing of clinical trials against chronic diseases in human subjects.

Low LKB1 Expression Results in Unfavorable Prognosis in Prostate Cancer Patients

Background

The present study aimed to compare the expression of liver kinase B1 (LKB1) in prostate cancer (PCa) tissues and the paired adjacent tissues, then to evaluate the statistical relationship between LKB1 expression and prognosis of PCa patients.

Material/Methods

The relative expression of LKB1 at mRNA level was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of LKB1 at protein level was measured by immunohistochemistry (IHC) method. The relationship between LKB1 expression and clinicopathologic characteristics was estimated by chi-square test. Kaplan-Meier method was used to analyze the overall survival of PCa patients with different LKB1 expression. Cox regression analysis was performed to estimate the significance of LKB1 expression and clinicopathologic characteristics in the prognosis of PCa patients.

Results

The relative expression of LKB1 at mRNA level was significantly lower in PCa tissues than in the normal tissues (P<0.001). The LKB1 expression was proved to be affected by clinical stage (P=0.019) and PSA concentration (P=0.031) of PCa patients. Moreover, patients with negative LKB1 expression had shorter survival than those with positive expression. Cox regression analysis confirmed that LKB1 could be regarded as a prognostic biomarker for PCa patients (P=0.001, HR=3.981, 95% CI=1.698–9.336).

Conclusions

The expression of LKB1 was lower in PCa tissues and might be a predictor for the prognosis of PCa patients.

[Mechanism of Warburg effect and its effect on tumor metastasis]

肿瘤细胞葡萄糖代谢的一个特点就是在氧含量正常的情况下依然选择利用糖酵解，即Warburg效应。Warburg效应的内在机制十分复杂，可能与癌基因激活、抑癌基因失活，糖代谢酶表达异常和肿瘤微环境改变等有关，具体的机制还有待进一步研究。Warburg效应这种代谢重编程与肿瘤的发生发展有着密切联系，为肿瘤细胞提供生长优势，帮助其逃避凋亡，同时为肿瘤的转移创造合适的环境，促进肿瘤转移。本文概述了Warburg效应的发生机制及其对肿瘤转移的作用。

MicroRNA regulation of tumorigenesis, cancer progression and interpatient heterogeneity: towards clinical use

In the past two decades, microRNAs have emerged as crucial mediators of organ development and human disease. Here, we discuss their role as drivers or suppressors of the hallmarks of cancer during tumorigenesis and progression, in defining interpatient heterogeneity and the promise of therapeutic application.

Role of the LKB1/AMPK pathway in tumor invasion and metastasis of cancer cells (Review)

Liver kinase B1 (LKB1), also known as serine/threo-nine kinase 11 (STK11), is a tumor suppressor that is inactivated in Peutz-Jeghers familial cancer syndrome. LKB1 phosphorylates and activates AMP-activated protein kinase (AMPK), which negatively regulates cancer cell proliferation and metabolism. However, recent evidence demonstrates that the LKB1/AMPK pathway is involved in the process of tumor invasion and migration, which is an important hallmark of carcinoma progression to higher pathological grades of malignancy. This review focuses on the function of the LKB1/AMPK pathway in the invasion and migration of cancer cells and provides an overview of therapeutic strategies aimed at this pathway in malignant tumors.

Inositol pyrophosphates promote tumor growth and metastasis by antagonizing liver kinase B1

The inositol pyrophosphates, molecular messengers containing an energetic pyrophosphate bond, impact a wide range of biologic processes. They are generated primarily by a family of three inositol hexakisphosphate kinases (IP6Ks), the principal product of which is diphosphoinositol pentakisphosphate (IP7). We report that IP6K2, via IP7 synthesis, is a major mediator of cancer cell migration and tumor metastasis in cell culture and in intact mice. IP6K2 acts by enhancing cell-matrix adhesion and decreasing cell-cell adhesion. This action is mediated by IP7-elicited nuclear sequestration and inactivation of the tumor suppressor liver kinase B1 (LKB1). Accordingly, inhibitors of IP6K2 offer promise in cancer therapy.

Loss of LKB1 disrupts breast epithelial cell polarity and promotes breast cancer metastasis and invasion

Background

LKB1, also known as STK11, is a master kinase that serves as an energy metabolic sensor and is involved in cell polarity regulation. Recent studies have indicated that LKB1 is related to breast tumorigenesis and breast cancer progression. However, little work has been done on the roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer. In this study, we tried to prove that loss of LKB1 disrupts breast epithelial cell polarity and causes tumor metastasis and invasion.

Methods

The relationships of LKB1 expression to clinic-pathological parameters and epithelial markers E-cadherin and high-molecular-weight -cytokeratin (HMW-CK) were investigated in 80 clinical breast cancer tissue samples and their paired normal control breast tissue samples by using immunohistochemistry. Then, the LKB1 expressions in metastatic and non-metastatic breast cancer cell lines were compared. The roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer were determined by using immunofluorescence, western blot assay, and cell migration and invasive assays. Finally, the non-transformed human breast cell line MCF-10A was cultured in three dimensions to further reveal the role of LKB1 in breast epithelial cell polarity maintenance.

Results

Histopathological analysis showed that LKB1 expression level was significantly negatively correlated with breast cancer TNM stage, and positively correlated with ER/PR status and expression levels of E-cadherin and HMW-CK. Immunofluorescence staining showed that LKB1 was co-localized with E-cadherin at adheren junctions. In vitro analysis revealed that loss of LKB1 expression enhanced migration, invasion and the acquisition of mesenchymal phenotype, while LKB1 overexpression in MDA-MB-435 s cells, which have a low basal level of LKB1 expression, promoted the acquisition of epithelial phenotype. Finally, it was found for the first time that endogenous LKB1 knockdown resulted in abnormal cell polarity in acini formed by non-transformed breast epithelial cells grown in 3D culture.

Conclusion

Our data indicated that low expression of LKB1 was significantly associated with established markers of unfavorable breast cancer prognosis, such as loss of ER/PR, E-cadherin and HMW-CK. Knockdown of endogenous LKB1 gave rise to dysregulation of cell polarity and invasive phenotype of breast cancer cells.

Transport in technicolor: mapping ATP-binding cassette transporters in sea urchin embryos

One quarter of eukaryotic genes encode membrane proteins. These include nearly 1,000 transporters that translocate nutrients, signaling molecules, and xenobiotics across membranes. While it is well appreciated that membrane transport is critical for development, the specific roles of many transporters have remained cryptic, in part because of their abundance and the diversity of their substrates. Multidrug resistance ATP-binding cassette (ABC) efflux transporters are one example of cryptic membrane proteins. Although most organisms utilize these ABC transporters during embryonic development, many of these transporters have broad substrate specificity, and their developmental functions remain incompletely understood. Here, we review advances in our understanding of ABC transporters in sea urchin embryos, and methods developed to spatially and temporally map these proteins. These studies reveal that multifunctional transporters are required for signaling, homeostasis, and protection of the embryo, and shed light on how they are integrated into ancestral developmental pathways recapitulated in disease.

Loss of the tumor suppressor LKB1 promotes metabolic reprogramming of cancer cells via HIF-1α

One of the major metabolic changes associated with cellular transformation is enhanced nutrient utilization, which supports tumor progression by fueling both energy production and providing biosynthetic intermediates for growth. The liver kinase B1 (LKB1) is a serine/threonine kinase and tumor suppressor that couples bioenergetics to cell-growth control through regulation of mammalian target of rapamycin (mTOR) activity; however, the influence of LKB1 on tumor metabolism is not well defined. Here, we show that loss of LKB1 induces a progrowth metabolic program in proliferating cells. Cells lacking LKB1 display increased glucose and glutamine uptake and utilization, which support both cellular ATP levels and increased macromolecular biosynthesis. This LKB1-dependent reprogramming of cell metabolism is dependent on the hypoxia-inducible factor-1α (HIF-1α), which accumulates under normoxia in LKB1-deficient cells and is antagonized by inhibition of mTOR complex I signaling. Silencing HIF-1α reverses the metabolic advantages conferred by reduced LKB1 signaling and impairs the growth and survival of LKB1-deficient tumor cells under low-nutrient conditions. Together, our data implicate the tumor suppressor LKB1 as a central regulator of tumor metabolism and growth control through the regulation of HIF-1α-dependent metabolic reprogramming.