Expression and prognostic significance of a new tumor metastasis suppressor gene LASS2 in human bladder carcinoma

Expression of LASS2 Can be Regulated by Dihydroartemisinin to Regulate Cisplatin Chemosensitivity in Bladder Cancer Cells

INTRODUCTION

The aim of this study was to investigate the potential of dihydroartemisinin to augment the efficacy of cisplatin chemotherapy through the modulation of LASS2 expression.

METHODS

TCMSP, CTR-DB, TCGA-BLC, and other databases were used to analyze the possibility of LASS2 as the target gene of dihydroartemisinin. Cell experiments revealed the synergistic effect of DDP and DHA. Animal experiments showed that DHA inhibited the growth of DDP-treated mice. In addition, WB, real-time PCR, and immunohistochemical analysis showed that DHA enhanced LASS2 (CERS2) expression in bladder cancer cells and DDP-treated mice.

RESULTS

LASS2 is associated with cisplatin chemosensitivity.LASS2 expression levels are different between BLC tissues and normal tissues. COX analysis showed that patients with high LASS2 expression had a higher cumulative overall survival rate than those with low LASS2 expression. The Sankey plot showed that LASS2 expression is lower in BLC tissues with more advanced stage and distant metastasis. The docking score of DHA and LASS2 reached the maximum value of -5.5259, indicating that DHA had a strong binding affinity with LASS2 targets. CCK8 assay showed that the most effective concentration ratio of DHA to DDP was 2.5 μg/ml + 10μg/ml. In vivo experiments showed that DHA inhibited tumor growth in cisplatin-treated mice. In addition, WB, RT-qPCR, and immunohistochemical analysis showed that DHA was able to enhance LASS2 expression in BLC cells and DDP-treated mice.

CONCLUSION

The upregulation of LASS2 (CERS2) expression in bladder cancer cells by DHA has been found to enhance cisplatin chemosensitivity.

A review of nuclear Dbf2-related kinase 1 (NDR1) protein interaction as promising new target for cancer therapy

Nuclear Dbf2-related kinase 1 (NDR1) is a nuclear Dbf2-related (NDR) protein kinase family member, which regulates cell functions and participates in cell proliferation and differentiation through kinase activity. NDR1 regulates physiological functions by interacting with different proteins. Protein-protein interactions (PPIs) are crucial for regulating biological processes and controlling cell fate, and as a result, it is beneficial to study the actions of PPIs to elucidate the pathological mechanism of diseases. The previous studies also show that the expression of NDR1 is deregulated in numerous human cancer samples and it needs the context-specific targeting strategies for NDR1. Thus, a comprehensive understanding of the direct interaction between NDR1 and varieties of proteins may provide new insights into cancer therapies. In this review, we summarize recent studies of NDR1 in solid tumors, such as prostate cancer and breast cancer, and explore the mechanism of action of PPIs of NDR1 in tumors.

LASS2 enhances chemosensitivity to cisplatin by inhibiting PP2A-mediated β-catenin dephosphorylation in a subset of stem-like bladder cancer cells

BACKGROUND

The benefits of first-line, cisplatin-based chemotherapy for muscle-invasive bladder cancer are limited due to intrinsic or acquired resistance to cisplatin. Increasing evidence has revealed the implication of cancer stem cells in the development of chemoresistance. However, the underlying molecular mechanisms remain to be elucidated. This study investigates the role of LASS2, a ceramide synthase, in regulating Wnt/β-catenin signaling in a subset of stem-like bladder cancer cells and explores strategies to sensitize bladder cancer to cisplatin treatment.

METHODS

Data from cohorts of our center and published datasets were used to evaluate the clinical characteristics of LASS2. Flow cytometry was used to sort and analyze bladder cancer stem cells (BCSCs). Tumor sphere formation, soft agar colony formation assay, EdU assay, apoptosis analysis, cell viability, and cisplatin sensitivity assay were used to investigate the functional roles of LASS2. Immunofluorescence, immunoblotting, coimmunoprecipitation, LC-MS, PCR array, luciferase reporter assays, pathway reporter array, chromatin immunoprecipitation, gain-of-function, and loss-of-function approaches were used to investigate the underlying mechanisms. Cell- and patient-derived xenograft models were used to investigate the effect of LASS2 overexpression and a combination of XAV939 on cisplatin sensitization and tumor growth.

RESULTS

Patients with low expression of LASS2 have a poorer response to cisplatin-based chemotherapy. Loss of LASS2 confers a stem-like phenotype and contributes to cisplatin resistance. Overexpression of LASS2 results in inhibition of self-renewal ability of BCSCs and increased their sensitivity to cisplatin. Mechanistically, LASS2 inhibits PP2A activity and dissociates PP2A from β-catenin, preventing the dephosphorylation of β-catenin and leading to the accumulation of cytosolic phospho-β-catenin, which decreases the transcription of the downstream genes ABCC2 and CD44 in BCSCs. Overexpression of LASS2 combined with a tankyrase inhibitor (XAV939) synergistically inhibits tumor growth and restores cisplatin sensitivity.

CONCLUSIONS

Targeting the LASS2 and β-catenin pathways may be an effective strategy to overcome cisplatin resistance and inhibit tumor growth in bladder cancer patients.

The Role of Longevity Assurance Homolog 2/Ceramide Synthase 2 in Bladder Cancer

The human CERS2 gene encodes a ceramide synthase enzyme, known as CERS2 (ceramide synthase 2). This protein is also known as LASS2 (LAG1 longevity assurance homolog 2) and TMSG1 (tumor metastasis-suppressor gene 1). Although previously described as a tumor suppressor for different types of cancer, such as prostate or liver cancer, it has also been observed to promote tumor growth in adenocarcinoma. In this review, we focus on the influence of CERS2 in bladder cancer (BC), approaching the existing literature about its structure and activity, as well as the miRNAs regulating its expression. From a mechanistic point of view, different explanations for the role of CERS2 as an antitumor protein have been proposed, including the production of long-chain ceramides, interaction with vacuolar ATPase, and its function as inhibitor of mitochondrial fission. In addition, we reviewed the literature specifically studying the expression of this gene in both BC and biopsy-derived tumor cell lines, complementing this with an analysis of public gene expression data and its association with disease progression. We also discuss the importance of CERS2 as a biomarker and the presence of CERS2 mRNA in extracellular vesicles isolated from urine.

Natural Products and Small Molecules Targeting Cellular Ceramide Metabolism to Enhance Apoptosis in Cancer Cells

Molecular targeting strategies have been used for years in order to control cancer progression and are often based on targeting various enzymes involved in metabolic pathways. Keeping this in mind, it is essential to determine the role of each enzyme in a particular metabolic pathway. In this review, we provide in-depth information on various enzymes such as ceramidase, sphingosine kinase, sphingomyelin synthase, dihydroceramide desaturase, and ceramide synthase which are associated with various types of cancers. We also discuss the physicochemical properties of well-studied inhibitors with natural product origins and their related structures in terms of these enzymes. Targeting ceramide metabolism exhibited promising mono- and combination therapies at preclinical stages in preventing cancer progression and cemented the significance of sphingolipid metabolism in cancer treatments. Targeting ceramide-metabolizing enzymes will help medicinal chemists design potent and selective small molecules for treating cancer progression at various levels.

Homeobox Gene Expression Dysregulation as Potential Diagnostic and Prognostic Biomarkers in Bladder Cancer

Homeobox genes serve as master regulatory transcription factors that regulate gene expression during embryogenesis. A homeobox gene may have either tumor-promoting or tumor-suppressive properties depending on the specific organ or cell lineage where it is expressed. The dysregulation of homeobox genes has been reported in various human cancers, including bladder cancer. The dysregulated expression of homeobox genes has been associated with bladder cancer clinical outcomes. Although bladder cancer has high risk of tumor recurrence and progression, it is highly challenging for clinicians to accurately predict the risk of tumor recurrence and progression at the initial point of diagnosis. Cystoscopy is the routine surveillance method used to detect tumor recurrence. However, the procedure causes significant discomfort and pain that results in poor surveillance follow-up amongst patients. Therefore, the development of reliable non-invasive biomarkers for the early detection and monitoring of bladder cancer is crucial. This review provides a comprehensive overview of the diagnostic and prognostic potential of homeobox gene expression dysregulation in bladder cancer.

The ceramide synthase (CERS/LASS) family: Functions involved in cancer progression

INTRODUCTION

Ceramide synthases (CERSes) are also known longevity assurance (LASS) genes. CERSes play important roles in the regulation of cancer progression. The CERS family is expressed in a variety of human tumours and is involved in tumorigenesis. They are closely associated with the progression of liver, breast, cervical, ovarian, colorectal, head and neck squamous cell, gastric, lung, prostate, oesophageal, pancreatic and blood cancers. CERSes play diverse and important roles in the regulation of cell survival, proliferation, apoptosis, migration, invasion, and drug resistance. The differential expression of CERSes in tumour and nontumour cells and survival analysis of cancer patients suggest that some CERSes could be used as potential prognostic markers. They are also important potential targets for cancer therapy.

METHODS

In this review, we summarize the available evidence on the inhibitory or promotive roles of CERSes in the progression of many cancers. Furthermore, we summarize the identified upstream and downstream molecular mechanisms that may regulate the function of CERSes in cancer settings.

Identify Potential Urine Biomarkers for Bladder Cancer Prognosis Using NGS Data Analysis and Experimental Validation

Bladder cancer (BC) is one of the most often reported malignancies globally, with a high recurrence rate and associated morbidity and mortality, especially in advanced BC. There has been a surge in the number of molecular targets revealed for BC prognosis and treatment. However, there is still a great need to discover novel biomarkers. Consequently, the current study investigated biomarkers that might indicate the progression of bladder cancer. In this study, bioinformatics analysis was done on a single GEO dataset, and TCGA-BLCA information was connected with differentially expressed genes (DEGs). The levels of mRNA and protein expression were validated using qRT-PCR. According to our findings, CRYAB, ECM1, ALDOB, AOC, GPX3, IGFBP7, AQP2, LASS2, TMEM176A, GALNT1, and LASS2 were highly enriched in cell division, identical protein binding, and developmental process in bladder cancer patients. In addition, among the highly differentiated genes, ECM1, GALNT1, LASS2, and GPX3 showed significant molecular alterations in BC, which are crucial for marker identification. Moreover, the mRNA, CNVs, and protein levels of ECM1, GALNT1, LASS2, and GPX3 were significantly increased in BC patients. Our predictions and analysis studies stated that these four genes act as urine biomarkers and played a crucial role in disease prognosis and the therapeutic process of bladder cancer. Our outcomes showed that these four novel urine biomarkers have the potential to provide innovative diagnostics, early predictions, and disease targets, ultimately improving the BC patient's prognosis.

Updates on the Pivotal Roles of Mitochondria in Urothelial Carcinoma

Mitochondria are important organelles responsible for energy production, redox homeostasis, oncogenic signaling, cell death, and apoptosis. Deregulated mitochondrial metabolism and biogenesis are often observed during cancer development and progression. Reports have described the crucial roles of mitochondria in urothelial carcinoma (UC), which is a major global health challenge. This review focuses on research advances in the role of mitochondria in UC. Here, we discuss the pathogenic roles of mitochondria in UC and update the mitochondria-targeted therapies. We aim to offer a better understanding of the mitochondria-modulated pathogenesis of UC and hope that this review will allow the development of novel mitochondria-targeted therapies.

CEBPγ facilitates lamellipodia formation and cancer cell migration through CERS6 upregulation

Ceramide synthase 6 (CERS6) promotes lung cancer metastasis by stimulating cancer cell migration. To examine the underlying mechanisms, we performed luciferase analysis of the CERS6 promoter region and identified the Y-box as a cis-acting element. As a parallel analysis of database records for 149 non-small-cell lung cancer (NSCLC) cancer patients, we screened for trans-acting factors with an expression level showing a correlation with CERS6 expression. Among the candidates noted, silencing of either CCAAT enhancer-binding protein γ (CEBPγ) or Y-box binding protein 1 (YBX1) reduced the CERS6 expression level. Following knockdown, CEBPγ and YBX1 were found to be independently associated with reductions in ceramide-dependent lamellipodia formation as well as migration activity, while only CEBPγ may have induced CERS6 expression through specific binding to the Y-box. The mRNA expression levels of CERS6, CEBPγ, and YBX1 were positively correlated with adenocarcinoma invasiveness. YBX1 expression was observed in all 20 examined clinical lung cancer specimens, while 6 of those showed a staining pattern similar to that of CERS6. The present findings suggest promotion of lung cancer migration by possible involvement of the transcription factors CEBPγ and YBX1.

Alternative splicing of ceramide synthase 2 alters levels of specific ceramides and modulates cancer cell proliferation and migration in Luminal B breast cancer subtype

Global dysregulation of RNA splicing and imbalanced sphingolipid metabolism has emerged as promoters of cancer cell transformation. Here, we present specific signature of alternative splicing (AS) events of sphingolipid genes for each breast cancer subtype from the TCGA-BRCA dataset. We show that ceramide synthase 2 (CERS2) undergoes a unique cassette exon event specifically in Luminal B subtype tumors. We validated this exon 8 skipping event in Luminal B cancer cells compared to normal epithelial cells, and in patient-derived tumor tissues compared to matched normal tissues. Differential AS-based survival analysis shows that this AS event of CERS2 is a poor prognostic factor for Luminal B patients. As Exon 8 corresponds to catalytic Lag1p domain, overexpression of AS transcript of CERS2 in Luminal B cancer cells leads to a reduction in the level of very-long-chain ceramides compared to overexpression of protein-coding (PC) transcript of CERS2. We further demonstrate that this AS event-mediated decrease of very-long-chain ceramides leads to enhanced cancer cell proliferation and migration. Therefore, our results show subtype-specific AS of sphingolipid genes as a regulatory mechanism that deregulates sphingolipids like ceramides in breast tumors, and can be explored further as a suitable therapeutic target.

Ceramide synthases: insights into the expression and prognosis of lung cancer

CerSs (ceramide synthases), a group of enzymes that catalyze the formation of ceramides from sphingoid base and acyl-CoA substrates. As far, six types of CerSs (CerS1-CerS6) have been found in mammals. Each of these enzymes have unique characteristics, but maybe more noteworthy is the ability of individual CerS isoform to produce a ceramide with a characteristic acyl chain distribution. As key regulators of sphingolipid metabolism, CerSs highlight their unique characteristics and have emerging roles in regulating programmed cell death, cancer and many other aspects of biology. However, the role of CerSs in lung cancer has not been fully elucidated. In this study, there was no significant change in the sequence or copy number of CerSs gene, which could explain the stability of malignant tumor development through COSMIC database. In addition, gene expression in lung cancer was examined using the Oncomine^TM database, and the prognostic value of each gene in non-small cell lung cancer (NSCLC) was analyzed by Kaplan-Meier analysis. The results showed that high mRNA expression levels of CerS2, CerS3, CerS4 and CerS5 in all NSCLC patients were associated with improved prognosis. Among them, CerS2 and CerS5 are also highly expressed in adenocarcinoma (Ade), but not in squamous cell carcinoma (SCC). In contrast, high or low expression of CerS1 and CerS6 no difference was observed in patients with NSCLC, Ade and SCC. Integrated the data of this study suggested that these CerSs may be a potential tumor markers or drug target of new research direction.

CERS6 required for cell migration and metastasis in lung cancer

Sphingolipids constitute a class of bio‐reactive molecules that transmit signals and exhibit a variety of physical properties in various cell types, though their functions in cancer pathogenesis have yet to be elucidated. Analyses of gene expression profiles of clinical specimens and a panel of cell lines revealed that the ceramide synthase gene CERS6 was overexpressed in non–small‐cell lung cancer (NSCLC) tissues, while elevated expression was shown to be associated with poor prognosis and lymph node metastasis. NSCLC profile and in vitro luciferase analysis results suggested that CERS6 overexpression is promoted, at least in part, by reduced miR‐101 expression. Under a reduced CERS6 expression condition, the ceramide profile became altered, which was determined to be associated with decreased cell migration and invasion activities in vitro. Furthermore, CERS6 knockdown suppressed RAC1‐positive lamellipodia/ruffling formation and attenuated lung metastasis efficiency in mice, while forced expression of CERS6 resulted in an opposite phenotype in examined cell lines. Based on these findings, we consider that ceramide synthesis by CERS6 has important roles in lung cancer migration and metastasis.

Association of rs8444 polymorphism in the LASS2 3'-UTR and bladder cancer risk in Chinese population

The aim of the present study was to explore the correlations between single nucleotide polymorphisms in LASS2 gene 3'-untranslated regions and bladder cancer risk in Chinese population. We first performed PCR and sequence for LASS2-3'-UTR in 105 bladder cancer patients and 100 control subjects. Next, multivariate logistic regression analysis was used to determine the relationship between single nucleotide polymorphisms frequency and susceptibility of bladder cancer, and clinical features in 105 cases. In addition, survival curves and Cox Regression analysis were used to investigate the effect of single nucleotide polymorphisms on clinical outcome in 58 cases. Finally, quantitative reverse-transcription PCR and immunohistochemical were performed to explore the influence of single nucleotide polymorphisms on LASS2 expression. We found that a single nucleotide polymorphism (rs8444 C>T) located in the 3'-UTR of LASS2 was significantly associated with the risk of bladder cancer. We also showed the frequency of rs8444 T genotype was higher in bladder cancer group and correlated with the risk of clinical prognosis. Yet, there were no significant correlations between T/C allele frequencies and the distributions of rs8444 genotype and tumor-node-metastasis stage, histological grade and distant metastasis in bladder cancer. Furthermore, we demonstrated that rs8444 C>T could affect LASS2 expression by single nucleotide polymorphism-related mRNA stability. Our results showed that LASS2-3'-UTR rs8444 C>T polymorphism was significantly associated with the individual risk and the poor overall survival of bladder cancer, suggesting that rs8444 TT genotype maybe act as an independent risk factor of susceptibility and clinical prognosis for bladder cancer in Chinese population.

Evaluation of CERS2 Gene as a Potential Biomarker for Bladder Cancer

The ceramide synthase 2 (CERS2) gene has been linked to tumour recurrence and invasion in many different types of cancers including bladder cancer. In this study, the expression levels of CERS2 in bladder cancer cell lines were analysed using qRT-PCR and the protein expression in clinical bladder cancer histopathological specimens were examined via immunohistochemistry. The potential utility of CERS2 as a predictive biomarker of response to oncolytic virotherapy was assessed by correlating the CERS2 mRNA expression to IC₅₀ values of cells treated with the Newcastle disease virus (NDV), AF2240 strain. This study demonstrates that CERS2 is differentially expressed in different types of bladder cancer cell lines and that the siRNA-mediated downregulation of the expression of CERS2 reduces the migratory potential of UMUC1 bladder cancer cells. However, there were no significant correlations between the expression levels of the CERS2 protein with bladder cancer grade/stage or between the IC50 values of cells treated with NDV and CERS2 expression. Although the utility of CERS2 expression may be limited, its potential as an antimigration cancer therapeutic should be further examined.

miR-3622a promotes proliferation and invasion of bladder cancer cells by downregulating LASS2

As a tumor metastasis suppressor gene, LASS2 has been found to be negatively associated with the stage of bladder cancer and overall survival of patients. However, the mechanisms regulating LASS2 in bladder cancer remain poorly understood. Here, we aim to identify a miRNA that targets LASS2 from bladder cancer-associated miRNAs and to reveal its potential functions in bladder cancer cells. Through miRNA microarray and bioinformatics analyses, we identified miR-3622a as a negative regulator of LASS2. The expression levels of miR-3622a in bladder cancer tissues were negatively correlated with the overall survival of patients. Overexpression of miR-3622a significantly increased the proliferation and invasion abilities of bladder cancer cells. In conclusion, our results indicate that miR-3622a promotes the proliferation and invasion of bladder cancer cells by downregulating LASS2.

Clinical and pathological significance of Homo sapiens ceramide synthase 2 (CerS-2) in diverse human cancers

Homo sapiens ceramide synthase 2 (CerS-2) plays an important role in inhibiting invasion and metastasis of tumor cells and has been reported as a tumor metastasis suppressor gene in diverse cancers. Thus, low level of CerS-2 protein might suggest a bad prognosis and up-regulation of CerS-2 protein might act as a promising therapeutic strategy for malignant tumors. In this review, we discussed the expression, as well as the clinical and pathological significance of CerS-2 in diverse human cancers. The pathological processes and molecular pathways regulated by CerS-2 were also summarized.

MicroRNA-98 promotes drug resistance and regulates mitochondrial dynamics by targeting LASS2 in bladder cancer cells

MicroRNA-98(miR-98) has been shown to be critical for tumorigenesis, however its involvement in bladder cancer are unclear. The present study aims to investigate the expression, biological roles and potential mechanisms of miR-98 in human bladder cancer. We found that miR-98 was upregulated in bladder urothelial carcinoma tissues compared with adjacent normal tissues. In addition, miR-98 expression was higher in bladder cancer cell lines than in uroepithelial cell line SV-HUC-1. Functional studies revealed that miR-98 mimic promoted proliferation of T24 cells while miR-98 inhibitor inhibited proliferation of BIU-87 cells. Moreover, miR-98 mimic increased cisplatin/doxorubicin resistance and inhibited apoptosis in T24 cells, while miR-98 inhibitor decreased chemoresistance and facilitated apoptosis in BIU-87 cells. Further experiments using MitoTracker and JC-1 staining showed that miR-98 could regulate mitochondrial fission/fusion balance and mitochondrial membrane potential. Western blot showed that miR-98 upregulated cyclin D1, p-Drp1 and Drp1. Using luciferase reporter assay, we demonstrated that LASS2 acted as a direct target of miR-98. LASS2 overexpression induced mitochondrial fusion and downregulated mitochondrial potential, with decreased p-Drp1 status. Additionally, LASS2 siRNA abrogated the effects of miR-98 mimic on Drp1phosphorylation and chemoresistance. We also found a negative correlation between LASS2 and miR-98 in bladder cancer tissues. In conclusion, our study demonstrates that miR-98 targets LASS2 and regulates bladder cancer chemoresistance through modulation of mitochondrial function.

Overexpression of LASS2 inhibits proliferation and causes G0/G1 cell cycle arrest in papillary thyroid cancer

Background

The aim of this study was to investigate the role of LAG1 longevity-assurance homologue 2 (LASS2) in papillary thyroid cancer (PTC).

Methods

Immunohistochemistry staining was conducted to explore the expression levels of LASS2 in PTC tissues and adjacent normal thyroid tissues and nodular goiter tissues. Western blotting and RT-qPCR were performed to explore the expression levels of LASS2 in three PTC cell lines (TPC-1, K1, BCPAP). An Adv-LASS2-GFP recombinant adenovirus vector was constructed and transduced into BCPAP cells. Then CCK-8 assay, colony formation assay, cell cycle distribution, and apoptosis were performed. Western blotting was used to examine the expression of p21, cyclin D1, cyclin-dependent kinase 4, p53 and p-p53.

Results

LASS2 was downregulated in PTC tissues compared with adjacent thyroid tissues or nodular goiter tissues. In addition, the expression of LASS2 was found to be associated with TNM stage and lymph node metastasis. BCPAP cells expressed the lowest LASS2 compared to TPC-1 cells or K1 cells. Overexpression of LASS2 significantly inhibited proliferation, promoted apoptosis and caused G0/G1 cell cycle arrest in BCPAP cells. Furthermore, overexpression of LASS2 significantly increased the expression of p21, inhibited the expression of cyclin D1 and cyclin-dependent kinase 4, and increased the expression of p-p53, but did not effect the expression of p53 in BCPAP cells.

Conclusion

Our findings indicate that overexpression of LASS2 inhibits PTC cell proliferation, promotes apoptosis and causes G0/G1 cell cycle arrest via a p53-dependent pathway. Thus, LASS2 may serve as a novel biomarker in PTC.

Hepatocyte-specific deletion of LASS2 protects against diet-induced hepatic steatosis and insulin resistance

Homo sapienslongevity assurance homolog 2 of yeast LAG1 (LASS2) is expressed mostly in human liver. Here, we explored roles of LASS2 in pathogenesis of hepatic steatosis. Hepatocyte-specific LASS2 knockout (LASS2^-/-) mice were generated using Cre-LoxP system. LASS2^-/- and wild-type (WT) mice were fed with chow or high-fat diet (HFD). We found LASS2^-/- mice were resistant to HFD-induced hepatic steatosis and insulin resistance. In HFD-fed mice, LASS2 deficiency significantly inhibited p38 MAPK and ERK1/ERK2 signaling in mouse liver. This effect was mediated by a significant increase of V-ATPase activity and a decrease of ROS level. We also observed that elevated expression of LASS2 in mouse hepatocyte cell line AML12 obviously decreased V-ATPase activity and increased ROS level by activation of p38 MAPK and ERK1/ERK2 signaling. Our findings indicate that LASS2 plays an important role in the pathogenesis of diet-induced hepatic steatosis and is a potential novel target for prevention and intervention of liver diseases.

LASS2 regulates invasion and chemoresistance via ERK/Drp1 modulated mitochondrial dynamics in bladder cancer cells

Mitochondria coordinated a lot of vital cellular processes of energy production and distribution. Change of mitochondrial functions has been implicated in cancer progression. The present study aims to investigate the involvement of mitochondria dynamics in LASS2 induced invasion and chemoresistance of bladder cancer cells. J82 and BIU87 cell lines were used for LASS2 plasmid transfection while siRNA knockdown was carried out in 5637 cell line. Matrigel invasion assay and Annexin V/PI staining demonstrated that LASS2 negatively regulated cancer cell invasion and chemoresistance. JC-1 staining suggested that LASS2 overexpression downregulated mitochondrial membrane potential. Mitotracker staining showed that LASS2 induced mitochondrial fusion and inhibited mitochondrial fission. In addition, LASS2 overexpression downregulated expression of mitochondrial fission protein p-Drp1 Drp1 and Fis1. While depletion of LASS2 exhibited the opposite effects. Drp1 inhibitor Mdivi abolished invasion and chemoresistance induced by LASS2 siRNA. Furthermore, we found that LASS2 overexpression could inhibit phosphorylation of ERK, which act upstream of Drp1. ERK inhibitor PD98059 suppressed Drp1 phosphorylation and abrogated the effects of LASS2 depletion. In conclusion, the present study demonstrated that LASS2 inhibits bladder cancer invasion and chemoresistance through regulation of ERK-Drp1 induced mitochondrial dynamics.

Liver-specific deletion of LASS2 delayed regeneration of mouse liver after partial hepatectomy

The capacity of liver regeneration is critical for patients with liver diseases. However, cellular and molecular mechanisms of liver regeneration are still incompletely defined. Here, we assessed roles of LASS2 in liver regeneration following partial hepatectomy (PHx) in mice. Our results showed that protein level of LASS2 remarkably increased during liver regeneration after PHx in wildtype (WT) mice. Comparing to WT mice, liver regeneration index after PHx was significantly decreased from day 1 to day 5 in liver-specific LASS2 knockout (LASS2-LKO) mice. Interestingly, liver mass of LASS2-LKO mice could sufficiently recover at day 14 after PHx. Immunohistochemistry (IHC) and western blot analyses revealed that proliferation markers, such as PCNA and Ki67, were potently reduced during liver regeneration in LASS2-LKO mice. In addition, several cell cycle related molecules, such as cyclin A, CDK2 and p-Rb, were decreased in LASS2-LKO mice after PHx. Co-immunoprecipitation assay further revealed a decreased formation of CDK4/cyclin D1 complex after PHx in LASS2-LKO mice. However, phosphorylation of Akt was significantly activated from day 2 after PHx in LASS2-LKO mice when compared with that in WT mice, which may explain the recovery of liver mass at the late stage of liver regeneration in LASS2-LKO mice. Taken together, we conclude that LASS2 plays an important role in efficient liver regeneration in response to PHx.

The role of LASS2 in regulating bladder cancer cell tumorigenicity in a nude mouse model

Previous in vitro studies have demonstrated that LAG1 longevity assurance homolog 2 (LASS2) is a novel tumor suppressor gene that is significantly associated with the proliferation and invasion ability of tumor cells. However, the role LASS2 serves in regulating bladder cancer cell tumorigenicity and tumor growth in vivo has not yet been elucidated in animal or clinical studies. In the present study, LASS2 knockdown in human bladder cancer EJ-M3 cells significantly promoted the growth of xenografts in nude mice compared with the control group, while overexpression of LASS2 suppressed tumor growth; however, this was not statistically significant. Furthermore, LASS2 knockdown resulted in more apparent heteromorphism and a higher activity of matrix metalloproteinase (MMP)-2 and MMP-9 in xenograft tumors. The data from the present study demonstrated that LASS2 knockdown significantly promoted the tumorigenicity and growth of EJ-M3 xenograft tumors in nude mice, and that LASS2 overexpression has a tendency to inhibit the growth of xenografts, suggesting that it may be a potential therapeutic target for bladder cancer.

LASS2 inhibits growth and invasion of bladder cancer by regulating ATPase activity

Homo sapiens longevity assurance homolog 2 of yeast LAG1 (LASS2) is a novel suppressor of human cancer metastasis, and downregulation of LASS2 has been associated with a poor prognosis in patients with bladder cancer (BC). However, the molecular mechanism underlying LASS2-mediated inhibition of tumor invasion and metastasis in BC remains unclear. LASS2 has been reported to directly bind to subunit C of vacuolar H⁺-ATPase (V-ATPase) in various types of cancer, suggesting that LASS2 may inhibit cancer invasion and metastasis by regulating the function of V-ATPase. The present study investigated the effect of LASS2-specific small interfering (si)RNA on the invasion and metastasis of the RT4 human BC cell line, which has a low metastatic potential, and its functional interaction with V-ATPase. Silencing of LASS2 in RT4 cells was able to increase V-ATPase activity, the extracellular hydrogen ion concentration and, in turn, the activation of secreted matrix metalloproteinase (MMP)-2 and MMP-9, which occurred simultaneously with enhanced cell proliferation, cell survival and cell invasion in vitro, as well as acceleration of BC growth in vivo. In this process, it was found that siRNA-LASS2 treatment was able to suppress cell apoptosis induced by doxorubicin. These findings suggest that silencing of LASS2 may enhance the growth, invasion and metastasis of BC by regulating ATPase activity.

The asialoglycoprotein receptor suppresses the metastasis of hepatocellular carcinoma via LASS2-mediated inhibition of V-ATPase activity

The asialoglycoprotein receptor (ASGR), which is expressed mainly in hepatocytes, is downregulated in poorly differentiated hepatocellular carcinoma (HCC). Here we investigated the role of ASGR1 in HCC metastasis as well as the possible underlying molecular mechanisms. We found that ASGR1 was downregulated in HCC tissue compared with adjacent non-tumorous liver tissue and that lower ASGR1 expression was associated with higher TNM stage and poorer prognosis in HCC patients. ASGR1 overexpression inhibited hepatoma cell migration and invasion in vitro and in vivo, while ASGR1 knockdown had the opposite effects. Furthermore, ASGR1 interacted directly with human longevity assurance homolog 2 of yeast LAG1 (LASS2). Knockdown of LASS2 attenuated the inhibitory effects of ASGR1 on hepatoma cell migration and invasion in vitro. ASGR1 decreased V-ATPase activity in hepatoma cells, and this was reversed by LASS2 knockdown. Finally, HCC patients with low LASS2 levels had poor prognosis, while those with high ASGR1 and LASS2 levels had better prognosis. Thus, ASGR1 may act as a potential metastasis suppressor in HCC, and the combination of ASGR1 and LASS2 may help predict the prognosis of HCC patients.

The enigma of ceramide synthase regulation in mammalian cells

Ceramide synthases (CerS) are key enzymes in the lipid metabolism of eukaryotic cells. Their products, ceramides (Cer), are components of cellular membranes but also mediate signaling functions in physiological processes such as proliferation, skin barrier function and cerebellar development. In pathophysiological processes such as multiple sclerosis and tumor progression, ceramide levels are altered, which can be ascribed, partly, to dysregulation of CerS gene transcription. Most publications deal with the effects of altered ceramide levels on physiological and pathophysiological processes, but the regulation of the appropriate CerS is frequently not investigated. This is insufficient for the clarification of the role of ceramides, because most ceramide species are generated by at least two CerS. The mechanisms of CerS regulation are manifold and it seems that each CerS isoform is regulated individually. For this reason, we discuss the different CerS separately in this review. From transcriptional regulation to alteration of protein activity, the possibilities to influence CerS are diverse. Furthermore, CerS are influenced by a variety of molecules including hormones and lipids. Without claiming completeness, we provide a résumé of the regulatory mechanisms for each CerS in mammalian cells and how dysregulation of these mechanisms during physiological processes may lead to pathophysiological processes.

Repression of the miR-93-enhanced sensitivity of bladder carcinoma to chemotherapy involves the regulation of LASS2

The aberrant expression of miRNA has an important function in bladder cancer (BC). Previous studies indicate that LASS2 is involved in the development of sensitivity to chemotherapy in cancer cells. In the present study, the miRNAs related to LASS2 were selected by using miRNA profiling to distinguish chemo-resistant and chemo-sensitive tumor specimens from patients. Higher levels of miR-93 were observed in the cisplatin-resistant BC cell line RT4, compared to the cell line T24. The role of miR-93 in chemo-sensitivity was demonstrated both in cell culture and mouse tumor xenograft models. We found that inhibiting miR-93 promoted cisplatin-induced apoptosis due to the accumulation of DNA damage. A reporter gene assay was performed, and the results showed miR-93 was not a target of the 3′ untranslated region of LASS2, but had an altered protein expression level. Inhibitors of miR-93 could also enhance the chemo-sensitivity of tumor cells transfected with si-LASS2, but the effect was very slight. These findings suggest that miR-93 plays an important role in the chemo-sensitivity of BC, and may be involved in regulating the LASS2 gene.

Overexpression of a Novel Tumor Metastasis Suppressor Gene TMSG1/LASS2 Induces Apoptosis via a Caspase-dependent Mitochondrial Pathway

The tumor metastasis suppressor gene 1 (TMSG1), also designated homo sapiens longevity assurance homologue 2 of yeast LAG1 (LASS2), is a novel tumor metastatic suppressor gene. Although its effects on metastasis have been reported, its biological functions remain unclear. The purpose of this study was to investigate the effects of TMSG1/LASS2 protein on apoptosis and proliferation in human embryonic kidney cell lines HEK293 and 293 T and explore the potential mechanisms. Cell growth, morphology, expressions of apoptotic-related proteins and cell cycle distribution were evaluated in HEK293 and 293 T cells transfected with TMSG1/LASS2 expression plasmids or vector controls. MTT assays showed that overexpression of TMSG1/LASS2 inhibited cell proliferation; and morphological observations and flow cytometric assays with Annexin V/propidium iodide showed TMSG1/LASS2 overexpression increased apoptosis in these cells. Western blot analysis demonstrated that overexpression of TMSG1/LASS2 resulted in the downregulation of Bcl-2, release of cytochrome c from mitochondria, activation of procaspase-9 and procaspase-3, and the cleavage of PARP. Subsequent cell cycle analysis showed that TMSG1/LASS2 overexpression inhibited cell proliferation by mediating the induction of G0/G1 cell cycle arrest. Together, these results confirmed that TMSG1/LASS2 is a potential metastasis suppressor gene, and suggested that the mechanism involved the induction of apoptosis and inhibition of cell proliferation via a caspase-dependent mitochondrial pathway.

Targeting ceramide synthase 6-dependent metastasis-prone phenotype in lung cancer cells

Sphingolipids make up a family of molecules associated with an array of biological functions, including cell death and migration. Sphingolipids are often altered in cancer, though how these alterations lead to tumor formation and progression is largely unknown. Here, we analyzed non-small-cell lung cancer (NSCLC) specimens and cell lines and determined that ceramide synthase 6 (CERS6) is markedly overexpressed compared with controls. Elevated CERS6 expression was due in part to reduction of microRNA-101 (miR-101) and was associated with increased invasion and poor prognosis. CERS6 knockdown in NSCLC cells altered the ceramide profile, resulting in decreased cell migration and invasion in vitro, and decreased the frequency of RAC1-positive lamellipodia formation while CERS6 overexpression promoted it. In murine models, CERS6 knockdown in transplanted NSCLC cells attenuated lung metastasis. Furthermore, combined treatment with l-α-dimyristoylphosphatidylcholine liposome and the glucosylceramide synthase inhibitor D-PDMP induced cell death in association with ceramide accumulation and promoted cancer cell apoptosis and tumor regression in murine models. Together, these results indicate that CERS6-dependent ceramide synthesis and maintenance of ceramide in the cellular membrane are essential for lamellipodia formation and metastasis. Moreover, these results suggest that targeting this homeostasis has potential as a therapeutic strategy for CERS6-overexpressing NSCLC.

Development of pheochromocytoma in ceramide synthase 2 null mice

Pheochromocytoma (PCC) and paraganglioma are rare neuroendocrine tumors of the adrenal medulla and sympathetic and parasympathetic paraganglia, for which mutations in ∼15 disease-associated genes have been identified. We now document the role of an additional gene in mice, the ceramide synthase 2 (CerS2) gene. CerS2, one of six mammalian CerS, synthesizes ceramides with very-long (C22-C24) chains. The CerS2 null mouse has been well characterized and displays lesions in several organs including the liver, lung and the brain. We now demonstrate that changes in the sphingolipid acyl chain profile of the adrenal gland lead to the generation of adrenal medullary tumors. Histological analyses revealed that about half of the CerS2 null mice developed PCC by ∼13 months, and the rest showed signs of medullary hyperplasia. Norepinephrine and normetanephrine levels in the urine were elevated at 7 months of age consistent with the morphological abnormalities found at later ages. Accumulation of ceroid in the X-zone was observed as early as 2 months of age and as a consequence, older mice displayed elevated levels of lysosomal cathepsins, reduced proteasome activity and reduced activity of mitochondrial complex IV by 6 months of age. Together, these findings implicate an additional pathway that can lead to PCC formation, which involves alterations in the sphingolipid acyl chain length. Analysis of the role of sphingolipids in PCC may lead to further understanding of the mechanism by which PCC develops, and might implicate the sphingolipid pathway as a possible novel therapeutic target for this rare tumor.

miR-9 promotes cell proliferation and inhibits apoptosis by targeting LASS2 in bladder cancer

MicroRNA-9 upregulation was reported in several tumors. However, its function and mechanism in human bladder cancer remains obscure. The present study aims to identify the expression pattern, biological roles and potential mechanism of miR-9 in human bladder cancers. We found that expression level of miR-9 in bladder cancer tissues was higher than normal tissues. miR-9 mimic transfection was performed in T24 and 5637 cells with low miR-9 expression, and miR-9 inhibitor was employed in BIU-87 cell line with high endogenous expression. miR-9 increased cell proliferation, cell cycle progression, invasion and chemoresistance, with upregulation of cyclin D1, MMP9, Bcl-2, and survivin and downregulation of E-cadherin. Using luciferase reporter assay, we confirmed that LASS2 was a direct target of miR-9 in bladder cancer cells. Transfection of miR-9 mimic downregulated LASS2 expression. LASS2 transfection downregulated Bcl-2 and survivin expression, which were induced by miR-9 mimic in both cell lines. In conclusion, these results indicate that miR-9 upregulation might be associated with malignant phenotype of bladder cancer. miR-9 promotes chemoresistance of bladder cancer cells by target LASS2.

Tumor metastasis suppressor gene-1 and tumors

Tumor metastasis suppressor gene-1 (TMSG-1) is a newly discovered tumor metastasis suppressor gene that plays important roles in promoting apoptosis and inhibiting invasion and metastasis of tumor cells. The inhibitory function of TMSG-1 in tumor cells may be related to vacuolar H⁺-ATPase and ceramide, but the underlying mechanism remains unknown. This review discusses the discovery of TMSG-1, the structure of TMSG-1 protein, as well as its possible mechanisms of action, expression in tumors and applications.

A Pilot Study on the Potential of RNA-Associated to Urinary Vesicles as a Suitable Non-Invasive Source for Diagnostic Purposes in Bladder Cancer

Bladder cancer is one of the most common cancers and, together with prostate carcinoma, accounts for the majority of the malignancies of the genitourinary tract. Since prognosis ameliorates with early detection, it will be beneficial to have a repertoire of diagnostic markers that could complement the current diagnosis protocols. Recently, cell-secreted extracellular vesicles have received great interest as a source of low invasive disease biomarkers because they are found in many body fluids, including urine. The current work describes a pilot study to generate an array-based catalogue of mRNA associated to urinary vesicles, and also a comparison with samples obtained from bladder cancer patients. After an analysis of presence/absence of transcripts in bladder cancer EVs, a list of genes was selected for further validation using PCR technique. We found four genes differentially expressed in cancer samples. LASS2 and GALNT1 were present in cancer patients, while ARHGEF39 and FOXO3 were found only in non-cancer urinary vesicles. Previous studies have pointed to the involvement of those genes in tumour progression and metastasis.

Enhancement of DEN-induced liver tumourigenesis in hepatocyte-specific Lass2-knockout mice coincident with upregulation of the TGF-β1-Smad4-PAI-1 axis

Longevity assurance homolog 2 of yeast LAG1 (Lass2) gene is capable of suppressing the proliferation and metastasis of several types of tumours including liver cancer. In the present study, hepatocyte-specific Lass2-knockout (Lass2 KO) and wild-type (WT) mice were exposed to the carcinogen, diethylnitrosamine (DEN), to induced liver tumours. At week 23 following DEN injection, tumours were produced in 100% of the Lass2 KO mice and 21.4% of the WT mice. At week 40, 100% of the Lass2 KO mice and 78.6% of the WT mice developed tumours, with no distinct significant difference in tumour occurrences between the two genotypes; yet, tumours in the Lass2 KO mouse livers were more numerous and larger in size. Hepatocellular carcinoma (HCC) was confirmed by α-fetoprotein (AFP). PCNA and EdU assays indicated more active proliferation whereas TUNEL assay revealed decreased apoptosis in Lass2 KO livers, when compared with the WT control. The expression of plasminogen activator inhibitor type-1 (PAI-1), a tumour-promoting gene, in the liver tissues of the 2 genotypes was detected using qPCR and western blotting, showing that PAI-1 levels were significantly elevated in Lass2 KO livers at week 40 following DEN introduction. Moreover, the expression of PAI-1-related TGF-β1, Smad-4 and -7 was detected, displaying an elevation in TGF-β1 and Smad-4 (not including Smad-7) in the Lass2 KO livers. Our data demonstrates that i) Lass2 is a protective gene against DEN-induced liver tumourigenesis; and ii) upregulation of the TGF-β1-Smad4-PAI-1 axis may contribute to the vulnerability of Lass2-knockout mice to DEN.

Bladder cancer: a simple model becomes complex

Bladder cancer is one of the most frequent malignancies in developed countries and it is also characterized by a high number of recurrences. Despite this, several authors in the past reported that only two altered molecular pathways may genetically explain all cases of bladder cancer: one involving the FGFR3 gene, and the other involving the TP53 gene. Mutations in any of these two genes are usually predictive of the malignancy final outcome. This cancer may also be further classified as low-grade tumors, which is always papillary and in most cases superficial, and high-grade tumors, not necessarily papillary and often invasive. This simple way of considering this pathology has strongly changed in the last few years, with the development of genome-wide studies on expression profiling and the discovery of small non-coding RNA affecting gene expression. An easy search in the OMIM (On-line Mendelian Inheritance in Man) database using "bladder cancer" as a query reveals that genes in some way connected to this pathology are approximately 150, and some authors report that altered gene expression (up- or down-regulation) in this disease may involve up to 500 coding sequences for low-grade tumors and up to 2300 for high-grade tumors. In many clinical cases, mutations inside the coding sequences of the above mentioned two genes were not found, but their expression changed; this indicates that also epigenetic modifications may play an important role in its development. Indeed, several reports were published about genome-wide methylation in these neoplastic tissues, and an increasing number of small non-coding RNA are either up- or down-regulated in bladder cancer, indicating that impaired gene expression may also pass through these metabolic pathways. Taken together, these data reveal that bladder cancer is far to be considered a simple model of malignancy. In the present review, we summarize recent progress in the genome-wide analysis of bladder cancer, and analyse non-genetic, genetic and epigenetic factors causing extensive gene mis-regulation in malignant cells.

Expression of a tumor-associated gene, LASS2, in the human bladder carcinoma cell lines BIU-87, T24, EJ and EJ-M3

Homo sapiens longevity assurance homolog 2 of yeast LAG1 (LASS2), a metastasis suppressor gene of human cancer, is the most abundantly expressed member of the ceramide synthase gene family. Expression of LASS2 has been reported in carcinomas of the prostate, liver and breast. However, there has been no report on the expression of LASS2 in human bladder cancer cell lines. In order to investigate the expression and potential role of this new tumor metastasis supressor gene in human bladder cancer, we compared the proliferation, metastasis and invasion among the BIU-87, T24, EJ and EJ-M3 human bladder cancer cell lines. The mRNA expression levels of the LASS2 gene were examined using real-time quantitative PCR (qPCR). The expression levels of LASS1 and LASS3 mRNA were used as references. The protein expression level of the LASS2 gene was detected using western blotting. The most aggressive of these four human cancer cell lines was observed to be EJ-M3. The expression of LASS2 mRNA was significantly correlated with diverse proliferation, metastasis and invasion. The expression levels of LASS1 and LASS3 mRNA were not correlated with these parameters. At the protein level, we observed that the more aggressive the cancer cell line, the lower the LASS2 protein expression level. Therefore, LASS2 expression may be correlated with the development and progression of human bladder cancer and may be a prognostic indicator for this cancer.