CLDN6-induced apoptosis via regulating ASK1-p38/JNK signaling in breast cancer MCF-7 cells

Abrogating PDK4 activates autophagy-dependent ferroptosis in breast cancer via ASK1/JNK pathway

BACKGROUND

Targeting ferroptosis mediated by autophagy presents a novel therapeutic approach to breast cancer, a mortal neoplasm on the global scale. Pyruvate dehydrogenase kinase isozyme 4 (PDK4) has been denoted as a determinant of breast cancer metabolism. The target of this study was to untangle the functional mechanism of PDK4 in ferroptosis dependent on autophagy in breast cancer.

METHODS

RT-qPCR and western blotting examined PDK4 mRNA and protein levels in breast cancer cells. Immunofluorescence staining appraised light chain 3 (LC3) expression. Fe (2 +) assay estimated total iron level. Relevant assay kits and C11-BODIPY (591/581) staining evaluated lipid peroxidation level. DCFH-DA staining assayed intracellular reactive oxygen species (ROS) content. Western blotting analyzed the protein levels of autophagy, ferroptosis and apoptosis-signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) pathway-associated proteins.

RESULTS

PDK4 was highly expressed in breast cancer cells. Knockdown of PDK4 induced the autophagy of breast cancer cells and 3-methyladenine (3-MA), an autophagy inhibitor, countervailed the promoting role of PDK4 interference in ferroptosis in breast cancer cells. Furthermore, PDK4 knockdown activated ASK1/JNK pathway and ASK1 inhibitor (GS-4997) partially abrogated the impacts of PDK4 absence on the autophagy and ferroptosis in breast cancer cells.

CONCLUSION

To sum up, deficiency of PDK4 activated ASK1/JNK pathway to stimulate autophagy-dependent ferroptosis in breast cancer.

CLDN6 inhibited cellular biological function of nonsmall cell lung cancer cells through suppressing aerobic glycolysis via the RIP1/ASK1/JNK axis

Claudin-6 (CLDN6) has been extensively studied in different tumors to date. However, in the case of nonsmall cell lung cancer (NSCLC), CLDN6 has a largely unknown role and molecular mechanism. We detected the expression of CLDN6 in NSCLC tissues and cells using reverse transcription-quantitative polymerase chain reaction (PCR) and western blot assays. A gain-of-function experiment was performed to evaluate the biological effects of CLDN6 on NSCLC cell behaviors. Methylation-specific PCR was utilized to detect the DNA methylation of CLDN6 gene promoter region. The interaction of CLDN6 and receptor interacting protein 1 (RIP1) was determined by coimmunoprecipitation assay. Furthermore, the modulation of CLDN6 on RIP1/apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) axis was confirmed. The results showed that in NSCLC tissues and cells, CLDN6 expression level was declined, and was associated with a high level of DNA methylation. CLDN6 overexpression suppressed the viability, invasion, migration, and promoted cell apoptosis. Besides, the enhanced expression of CLDN6 reduced the glycolysis and the dysfunction of mitochondrial respiration of NSCLC cells. Mechanistic investigation confirmed that CLDN6 interacted with RIP1 and inhibited cellular biological function of NSCLC cells via RIP1/ASK1/JNK axis. Besides, CLDN6 overexpression inhibited tumor growth in vivo. In conclusion, CLDN6 inhibited NSCLC cell proliferation through inactivating aerobic glycolysis via the RIP1/ASK1/JNK axis.

Expression patterns of claudins in cancer

Claudins are four-transmembrane proteins, which were found in tight junctions. They maintain cell barriers and regulate cell differentiation and proliferation. They are involved in maintaining cellular polarity and normal functions. Different claudins show different expression patterns. The expression level and localization of claudins are altered in various cancers. They promote or inhibit proliferation, invasion, and migration of cancer cells through multiple signaling pathways. Therefore, claudins may serve as diagnostic markers, novel therapeutic targets, and prognostic risk factors. The important roles of claudins in cancer aroused our great interest. In the present review, we provide a summary of insights into expression patterns of claudins in cancer, which is more comprehensive and provides new ideas for further research.

CLDN6 Suppresses Migration and Invasion of MCF-7 and SKBR-3 Breast Cancer Cells by Blocking the SMAD/Snail/MMP-2/9 Axis

The study examined the mechanisms of action of signal protein claudin 6 (CLDN6) on migration and invasion of breast cancer cell lines MCF-7 and SKBR-3. To this end, the signal proteins SMAD were blocked with their inhibitor SB431542, the genes CLDN6 and SNAIL were knocked down with short hairpin RNAs, and MMP2 and MMP9 were inhibited with TIMP-1. Expressions of MMP2 and MMP9 mRNAs were evaluated by reverse transcription PCR, Expressions of MMP-2, MMP-9, E-cadherin, N-cadherin, and vimentin were examined by Western blotting. Migration and invasion were analyzed by scratch test and Matrigel invasion assay. SB431542 inhibited expression of MMP2 and MMP9 in both cell lines. Single use of SB431542 inhibited expression of MMP-2/MMP-9 and corresponding mRNAs, but subsequent silencing of CLDN6 gene reversed this effect. TIMP-1 reversed down-regulation of E-cadherin, upregulation of N-cadherin and vimentin, facilitation of migration and invasion evoked by CLDN6 knocking down. Silencing of SNAIL gene inhibited migration and invasion, upregulated the expression of E-cadherin, and down-regulated expression of MMP2, MMP 9, N-cadherin, and vimentin. Thus, CLDN6 suppresses the epithelial-mesenchymal transition, migration, and invasion via blocking SMAD/Snail/MMP-2/9 signaling pathway in MCF-7 and SKBR-3 cancer cell lines.

CLDN6 inhibits breast cancer metastasis through WIP-dependent actin cytoskeleton-mediated autophagy

BACKGROUND

As a breast cancer suppressor gene, CLDN6 overexpression was found to inhibit breast cancer metastasis in our previous studies, but the specific mechanism remains unclear. This study aimed to clarify the role and mechanism of CLDN6 in inhibiting breast cancer metastasis.

METHODS

Western blot, immunofluorescence and transmission electron microscopy were performed to detect autophagy. Wound healing, transwell assays and lung metastasis mouse models were used to examine breast cancer metastasis. Phalloidin staining and immunofluorescent staining were used to observe actin cytoskeleton. mRNA seq, RT-PCR, western blot, chromatin immunoprecipitation, dual luciferase reporter assay, co-immunoprecipitation and immunofluorescence were performed to define the molecular mechanism. The expression levels and clinical implication of CLDN6, WIP and LC3 in breast cancer tissues were evaluated using immunohistochemistry.

RESULTS

We demonstrated that CLDN6 inhibited breast cancer metastasis through autophagy in vitro and vivo. We unraveled a novel mechanism that CLDN6 regulated autophagy via WIP-dependent actin cytoskeleton assembly. Through its PDZ-binding motif, overexpressed CLDN6 interacted with JNK and upregulated JNK/c-Jun pathway. C-Jun promoted WIP expression at the transcriptional level. Notably, we observed c-Jun transcriptionally upregulated CLDN6 expression, and there was a positive feedback loop between CLDN6 and JNK/c-Jun. Finally, we found that CLDN6, WIP and LC3 expression correlated with each other, and WIP expression was significantly associated with lymph node metastasis of breast cancer patients.

CONCLUSIONS

The data provide a new insight into the inhibitory effects of CLDN6-mediated autophagy on breast cancer metastasis, and revealed the new mechanism of CLDN6 regulating autophagy through WIP-dependent actin cytoskeleton. Our findings enrich the theoretical basis for CLDN6 as a potential biomarker for breast cancer diagnosis and therapy.

Sq-2, a biotinylated annonaceous acetogenin, induces apoptosis, autophagy and S-phase arrest by activating the MAPK pathway in breast cancer cells

Squamocin, an annonaceous acetogenin isolated from plants in the Annonaceae family, has antitumour activity. In this study, we report that Sq-2, a biotinylated squamocin monomer, has a favorable antitumour effect on MDA-MB-231 and SKBR3 breast cancer cells in vitro. MTT assays show that Sq-2 has a better antitumour effect on MDA-MB-231 cells than Sq-5 and Sq-6. Furthermore, RNA-Seq and KEGG enrichment analyses reveal that Sq-2 activates the MAPK signaling pathway, and results of western blot analysis demonstrate that Sq-2 activates the JNK and p38 pathways in MDA-MB-231 and SKBR3 cells. Flow cytometry and western blot analysis reveal that Sq-2 induces cell apoptosis by increasing the expressions of cleaved Caspase-3 and cleaved PARP as well as the ratio of Bax/Bcl-2. Inhibition of the Caspase family by Z-VAD-FMK attenuates the viability of MDA-MB-231 cells, indicating that Sq-2 induces apoptosis in a Caspase-dependent manner. Additionally, pretreatment with the p38 inhibitor SB203580 or JNK inhibitor SP600125 partially reverses the increase in the apoptosis rate and decrease in cell viability prompted by Sq-2. Furthermore, Sq-2 treatment decreases the expression level of CyclinD1 and increases the expression levels of p21, p27, CyclinA1, and CDK2, causing S-phase arrest in MDA-MB-231 and SKBR3 cells. Further study indicates that Sq-2 stimulates autophagy in MDA-MB-231 and SKBR3 cells, and inhibition of autophagy by bafilomycin A1 increases cell viability and promotes cell survival. Sq-2, a novel biotin-squamocin compound, shows a significant inhibitory effect on the propagation of SKBR3 and MDA-MB-231 breast cancer cells. Furthermore, Sq-2 treatment not only induces S-phase arrest and activates the JNK and p38 pathways to trigger apoptosis but also causes autophagy to promote apoptosis in MDA-MB-231 and SKBR3 cells.

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The role and mechanism of claudins in cancer

Claudins are a tetraspan membrane protein multigene family that plays a structural and functional role in constructing tight junctions. Claudins perform crucial roles in maintaining cell polarity in epithelial and endothelial cell sheets and controlling paracellular permeability. In the last two decades, increasing evidence indicates that claudin proteins play a major role in controlling paracellular permeability and signaling inside cells. Several types of claudins are dysregulated in various cancers. Depending on where the tumor originated, claudin overexpression or underexpression has been shown to regulate cell proliferation, cell growth, metabolism, metastasis and cell stemness. Epithelial-to-mesenchymal transition is one of the most important functions of claudin proteins in disease progression. However, the exact molecular mechanisms and signaling pathways that explain why claudin proteins are so important to tumorigenesis and progression have not been determined. In addition, claudins are currently being investigated as possible diagnostic and treatment targets. Here, we discuss how claudin-related signaling pathways affect tumorigenesis, tumor progression, and treatment sensitivity.

Potential Molecular Mechanisms of Recurrent and Progressive Meningiomas: A Review of the Latest Literature

Meningiomas, the most frequent primary intracranial tumors of the central nervous system in adults, originate from the meninges and meningeal spaces. Surgical resection and adjuvant radiation are considered the preferred treatment options. Although most meningiomas are benign and slow-growing, some patients suffer from tumor recurrence and disease progression, eventually resulting in poorer clinical outcomes, including malignant transformation and death. It is thus crucial to identify these “high-risk” tumors early; this requires an in-depth understanding of the molecular and genetic alterations, thereby providing a theoretical foundation for establishing personalized and precise treatment in the future. Here, we review the most up-to-date knowledge of the cellular biological alterations involved in the progression of meningiomas, including cell proliferation, neo-angiogenesis, inhibition of apoptosis, and immunogenicity. Focused genetic alterations, including chromosomal abnormalities and DNA methylation patterns, are summarized and discussed in detail. We also present latest therapeutic targets and clinical trials for meningiomas' treatment. A further understanding of cellular biological and genetic alterations will provide new prospects for the accurate screening and treatment of recurrent and progressive meningiomas.

The expression and the tumor suppressor role of CLDN6 in colon cancer

As a member of the tight junction family, CLDN6 is a tumor suppressor in breast cancer, but its role in colon cancer is unknown. In this research, we aimed at revealing the function of CLDN6 in colon cancer. We found that colon cancer tissues lowly expressed CLDN6, and the expression of CLDN6 was negatively correlated with lymph node metastasis. Similarly, CLDN6 was lowly expressed in the colon cancer cell line SW1116, and overexpression of CLDN6 inhibited cell proliferation in vitro and in vivo. Consistently, the migration and invasion abilities of cells were significantly inhibited after CLDN6 overexpression. In addition, we demonstrated that CLDN6 may inhibit the migration and invasion abilities by activating the TYK2/STAT3 pathway. Therefore, our data indicated that CLDN6 acted as a tumor suppressor and had the potential to be regarded as a biomarker for the progression of colon cancer.

Abplatin(IV) inhibited tumor growth on a patient derived cancer model of hepatocellular carcinoma and its comparative multi-omics study with cisplatin

Background

Cisplatin, the alkylating agent of platinum(II) (Pt(II)), is the most common antitumor drug in clinic; however, it has many side effects, therefore it is higly desired to develop low toxicity platinum(IV) (Pt(IV)) drugs. Multi-omics analysis, as a powerful tool, has been frequently employed for the mechanism study of a certain therapy at the molecular level, which might be helpful for elucidating the mechanism of platinum drugs and facilitating their clinical application.

Methods

Strating form cisplatin, a hydrophobic Pt(IV) prodrug (CisPt(IV)) with two hydrophobic aliphatic chains was synthesized, and further encapsulated with a drug carrier, human serum albumin (HSA), to form nanoparticles, namely AbPlatin^(IV). The anticancer effect of AbPlatin^(IV) was investigated in vitro and in vivo. Moreover, transcriptomics, metabolomics and lipidomics were performed to explore the mechanism of AbPlatin(IV).

Results

Compared with cisplatin, Abplatin^(IV) exhibited better tumor-targeting effect and greater tumor inhibition rate. Lipidomics study showed that Abplatin^(IV) might induce the changes of BEL-7404 cell membrane, and cause the disorder of glycerophospholipids and sphingolipids. In addition, transcriptomics and metabolomics study showed that Abplatin^(IV) significantly disturbed the purine metabolism pathway.

Conclusions

This research highlighted the development of Abplatin^(IV) and the use of multi-omics for the mechanism elucidation of prodrug, which is the key to the clinical translation of prodrug.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01465-y.

Fluroxypyr-1-methylheptyl ester causes apoptosis of bovine mammary gland epithelial cells by regulating PI3K and MAPK signaling pathways and endoplasmic reticulum stress

Fluroxypyr-1-methylheptyl ester (FPMH) is an auxin herbicide that is widely applied to crops and pastures to block growth of post-emergence weeds. Several studies have reported the toxicity of FPMH in aquatic vertebrates. However, the adverse impacts of FPMH on mammals, including domestic animals, have not been reported. The purpose of our current study is to assess the impact of FPMH on the bovine mammary system and milk production. To evaluate the toxicity of FPMH on the mammary glands of lactating cows, the bovine mammary gland epithelial cell line, MAC-T, was exposed to various concentrations (0, 5, 7.5, 10, 15, and 20 μM) of FPMH for 24 h, and then various assessments were performed. The results showed that FPMH dose-dependently reduced MAC-T cell viability following exposure to FPMH and induced mitochondrial depolarization and apoptosis. FPMH also modulated signaling through the PI3K and MAPK pathways. In addition, the expression levels of proteins related to endoplasmic reticulum (ER) stress were upregulated, indicating induction of ER stress, and calcium homeostasis was disrupted following FPMH treatment. In conclusion, our investigation suggests that FPMH may be toxic to the bovine mammary system and may decrease dairy production.

CLDN6: From Traditional Barrier Function to Emerging Roles in Cancers

Claudins (CLDNs) are the most important tight junction proteins, which are mainly expressed in endothelial cells or epithelial cells in a tissue-specific manner. As a member of the CLDNs family, CLDN6 is highly expressed in fetal tissues such as the stomach, pancreas, lung, and kidney, but is not expressed in corresponding adult tissues. The expression of CLDN6 is regulated by a variety of factors, including but not limited to stimuli and transcription factors, DNA methylation, and post-translational modifications. CLDN6 has been found to have a key role in the formation of barriers, especially the lung epithelial barrier and the epidermal permeability barrier (EPB). Importantly, the roles of CLDN6 in cancers have gained focus and are being investigated in recent years. Strong evidence indicates that the altered expression of CLDN6 is linked to the development of various cancers. Malignant phenotypes of tumors affected by CLDN6 include proliferation and apoptosis, migration and invasion, and drug resistance, which are regulated by CLDN6-mediated key signaling pathways. Given the important role in tumors and its low or no expression in normal tissues, CLDN6 is an ideal target for tumor therapy. This review aims to provide an overview of the structure and regulation of CLDN6, and its traditional barrier function, with a special emphasis on its emerging roles in cancers, including its impact on the malignant phenotypes, signal-modulating effects, the prognosis of tumor patients, and clinical applications in cancers.

Claudin 6: Therapeutic prospects for tumours, and mechanisms of expression and regulation (Review)

Tight junctions (TJs) are an important component of cell connectivity; they maintain cell polarity, permeability and adhesion, and participate in the regulation of cell proliferation and differentiation. The claudin (CLDN) family is integral to TJs, and CLDN6 is an important member of this family. Abnormal expression of CLDN6 can destroy the integrity of TJs through various mechanisms and can serve multiple roles in the occurrence and development of tumours. CLDN6 is widely expressed in various tumours but rarely expressed in healthy adult tissues. The aim of this review is to critically examine the recent literature on CLDN6, including its structure, expression in different tumours, regulatory mechanisms and therapeutic prospects. Although some conclusions are controversial, in certain tumours, such as liver, ovarian, endometrial and oesophageal cancer, and atypical teratoid/rhabdoid tumours, research consistently shows that CLDN6 is expressed in tumour tissues but is not expressed or is expressed at low levels in surrounding tissues. In these tumours, CLDN6 has potential as a carcinoembryonic antigen and a therapeutic target.

Effects of the Tight Junction Protein CLDN6 on Cell Migration and Invasion in High-Grade Meningioma

BACKGROUND

Meningioma is a common tumor of the central nervous system, and malignant meningioma is highly aggressive and frequently recurs after surgical resection. Claudin 6 (CLDN6) is involved in cell proliferation, migration, and invasion and plays a role in maintaining tight junctions between cells and obstructing the movement of cells to neighboring tissues.

METHODS

In the present study, we evaluated the effect of tight junction protein CLDN6 expression levels on meningioma invasiveness using silencing and overexpression constructs in both in vitro and in vivo models. The expression of CLDN6 at the mRNA and protein levels was measured using quantitative reverse transcription polymerase chain reaction and Western blot assays.

RESULTS

We found that CLDN6 was expressed at higher levels in normal meningeal tissue and cell samples. Next, vectors with silenced and overexpressed CLDN6 were successfully established, and the expression of CLDN6 mRNA and protein in the IOMM-Lee and CH157-MN cell lines was downregulated after transfection with siRNA-CLDN6 and upregulated by transfection of the entire CLDN6 sequence vector. An in vitro assay revealed that abrogation of CLDN6 expression added to the capacity for tumor migration and invasion relative to the overexpression of CLDN6. In addition to the in vitro evidence, we observed a significant increase in tumor growth and invasion-associated gene expression, including matrix metalloproteinase-2, matrix metalloproteinase-9, vimentin, and N-cadherin, after silencing CLDN6 expression in vivo.

CONCLUSIONS

CLDN6 might play an important role in meningioma migration and invasion and, thus, might serve as a novel diagnostic and/or prognostic biomarker and as a potential therapeutic target.

Microcystin-LR induces ovarian injury and apoptosis in mice via activating apoptosis signal-regulating kinase 1-mediated P38/JNK pathway

As an emerging pollutant in the aquatic environment, microcystin-LR (MC-LR) can enter the body through multiple pathways, and then induce apoptosis and gonadal damage, affecting reproductive function. Previous studies focused on male reproductive toxicity induced by MC-LR neglecting its effects on females. The apoptotic signal-regulated kinase 1 (ASK1) is an upstream protein of P38/JNK pathway, closely associated with apoptosis and organ damage. However, the role of ASK1 in MC-LR-induced reproductive toxicity is unclear. Therefore, this study investigated the role of ASK1 in mouse ovarian injury and apoptosis induced by MC-LR. After MC-LR exposure, ASK1 expression in mouse ovarian granulosa cells was increased at the protein and mRNA levels, and decreased following pretreatment by antioxidant N-acetylcysteine, suggesting that MC-LR-induced oxidative stress has a regulatory role in ASK1 expression. Inhibition of ASK1 expression with siASK1 and NQDI-1 could effectively alleviate MC-LR-induced mitochondrial membrane potential damage and apoptosis in ovarian granulosa cells, as well as pathological damage, apoptosis and the decreased gonadal index in ovaries of C57BL/6 mice. Moreover, the P38/JNK pathway and downstream apoptosis-related proteins (P-P38, P-JNK, P-P53, Fas) and genes (MKK4, MKK3, Ddit3, Mef2c) were activated in vivo and vitro, but their activation was restrained after ASK1 inhibition. Data presented herein suggest that the ASK1-mediated P38/JNK pathway is involved in ovarian injury and apoptosis induced by MC-LR in mice. It is confirmed that ASK1 has an important role in MC-LR-induced ovarian injury, which provides new insights for preventing MCs-induced reproductive toxicity in females.

MiR-502 Suppresses TNF-α-Induced Nucleus Pulposus Cell Apoptosis by Targeting TARF2

Intervertebral disc degeneration (IVDD) is a common cause of low back pain. This study is aimed at investigating the role of microRNAs (miRNAs) in regulating human nucleus pulposus (NP) cell injury induced by tumor necrosis factor- (TNF-) α in IVDD. In this study, we induced NP cells with 20 ng/mL TNF-α in vitro, which promoted the obvious apoptosis of NP cells and the activation of nuclear transcription factor (NF)-κB. In contrast, using the specific NF-κB inhibitor BAY 11-7082 to treat cells greatly impaired the activation of NF-κB and increased the sensitivity of NP cells to TNF-α-induced apoptosis. Moreover, both TNF-α and BAY 11-7082 treatments were associated with marked miRNA dysregulation, with miR-502 being upregulated by TNF-α treatment and downregulated by BAY 11-7082 treatment, respectively. And the overexpression of miR-502 enhanced NF-κB activation and suppressed apoptosis of human NP cells induced by TNF-α, whereas the opposite was observed following miR-502 inhibition. Last, through bioinformatic analyses and luciferase reporter gene experiments, we identified TRAF2, an important activator of NF-κB, as a miR-502 target gene. Similarly, siRNA-mediated knockdown of the TRAF2 expression also suppressed TNF-α-induced apoptosis and enhanced NF-κB activation. Our findings provide evidence indicating that miR-502 is a key regulator of apoptosis of human NP cells induced by TNF-α by targeting TRAF2 and activating NF-κB.

Arctigenin Enhances the Cytotoxic Effect of Doxorubicin in MDA-MB-231 Breast Cancer Cells

Several reports have described the anti-cancer activity of arctigenin, a lignan extracted from Arctium lappa L. Here, we investigated the effect of arctigenin (ATG) on doxorubicin (DOX)-induced cell death using MDA-MB-231 human breast cancer cells. The results showed that DOX-induced cell death was enhanced by ATG/DOX co-treatment in a concentration-dependent manner and that this was associated with increased DOX uptake and the suppression of multidrug resistance-associated protein 1 (MRP1) gene expression in MDA-MB-231 cells. ATG enhanced DOX-induced DNA damage and decreased the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and the expressions of RAD51 and survivin. Cell death caused by ATG/DOX co-treatment was mediated by the nuclear translocation of apoptosis inducing factor (AIF), reductions in cellular and mitochondrial Bcl-2 and Bcl-xL, and increases in mitochondrial BAX levels. However, caspase-3 and -7 did not participate in DOX/ATG-induced cell death. We also found that DOX/ATG-induced cell death was linked with activation of the p38 signaling pathway and suppressions of the phosphorylations and expressions of Akt and c-Jun N-terminal kinase. Taken together, these results show that ATG enhances the cytotoxic activity of DOX in MDA-MB-231 human breast cancer cells by inducing prolonged p21 expression and p38-mediated AIF-dependent cell death. In conclusion, our findings suggest that ATG might alleviate the side effects and improve the therapeutic efficacy of DOX.

Claudin 10 acts as a novel biomarker for the prognosis of patients with ovarian cancer

Ovarian cancer (OC) is one of the most fatal gynecological malignancies in the world and confers a poor 5-year survival rate. The present study was designed to discover novel prognostic markers for patients with OC in order to estimate disease metastasis or recurrence. Based on the large cohorts of transcriptome data from multicenter sources, a comprehensive analysis was performed to explore potential prognostic markers. A total of 269 differentially expressed genes were identified, of which 32 were upregulated and 237 downregulated in OC tissues compared with the corresponding expression in normal tissues. Kaplan-Meier analysis, log-rank test and nomogram analysis were employed to demonstrate that low expression levels of claudin 10 (CLDN10) were associated with a less favorable disease prognosis. The most promising prognostic marker for OC was subsequently selected. Additionally, the prognostic nomogram was constructed in order to assess the 5-year survival rate using CLDN10 expression as a prognostic marker for OC. Furthermore, gene set enrichment analysis and analysis of the tumor-associated competing endogenous RNA network were performed to elucidate the potential biological processes associated with CLDN10 expression. The current results indicated that CLDN10 may influence OC progression via transforming growth factor-β (TGF-β)- or WNT/β-catenin-induced epithelial-to-mesenchymal transition (EMT). The associations among CLDN10, microRNA-486-5p, TGF-β, WNT/β-catenin and EMT should be further investigated in future studies.

Relationship between apical junction proteins, gene expression and cancer

The apical junctional complex (AJC) is a cell-cell adhesion system present at the upper portion of the lateral membrane of epithelial cells integrated by the tight junction (TJ) and the adherens junction (AJ). This complex is crucial to initiate and stabilize cell-cell adhesion, to regulate the paracellular transit of ions and molecules and to maintain cell polarity. Moreover, we now consider the AJC as a hub of signal transduction that regulates cell-cell adhesion, gene transcription and cell proliferation and differentiation. The molecular components of the AJC are multiple and diverse and depending on the cellular context some of the proteins in this complex act as tumor suppressors or as promoters of cell transformation, migration and metastasis outgrowth. Here, we describe these new roles played by TJ and AJ proteins and their potential use in cancer diagnostics and as targets for therapeutic intervention.

A SUMOylation-dependent HIF-1α/CLDN6 negative feedback mitigates hypoxia-induced breast cancer metastasis

Background

We have previously described CLDN6 as a tumor suppressor gene in breast cancer. Here, a new finding is that CLDN6 was upregulated under hypoxia, a commonly recognized factor that promotes tumor metastasis. In this study, we aim to explain this confusing finding and delineate the role of CLDN6 in the breast cancer metastasis induced by hypoxia.

Methods

RNAi and ChIP assays were used to confirm that CLDN6 is transcriptional regulated by HIF-1α. mRNA seq and KEGG analysis were performed to define the downstream pathways of CLDN6. The roles of the CLDN6/SENP1/HIF-1α signaling on tumor metastasis were evaluated by function experiments and clinical samples. Finally, the possible transcription factor of SENP1 was suspected and then validated by ChIP assay.

Results

We demonstrated a previously unrecognized negative feedback loop exists between CLDN6 and HIF-1α. CLDN6 was transcriptionally up-regulated by HIF-1α under hypoxia. On the other hand, in cytoplasm CLDN6 combines and retains β-catenin, a transcription factor of SENP1, causing β-catenin degradation and preventing its nuclear translocation. This process reduced SENP1 expression and prevented the deSUMOylation of HIF-1α, ultimately leading to HIF-1α degradation and breast cancer metastasis suppression.

Conclusions

Our data provide a molecular mechanistic insight indicating that CLDN6 loss may lead to elevated HIF-1α-driven breast cancer metastasis in a SUMOylation-dependent manner.

Downregulation of CLDN6 inhibits cell proliferation, migration, and invasion via regulating EGFR/AKT/mTOR signalling pathway in hepatocellular carcinoma

Accumulating evidence showed that the claudin-6 (CLDN6) expression was abnormal in many cancers, while its expression and biological functions in hepatocellular carcinoma (HCC) is still unclear. The present study demonstrated that CLDN6 was upregulated in HCC tissues compared with tumour-adjacent tissues. CLDN6 silencing was significantly inhibited proliferation, migration, and invasion of HepG2 cells. Meanwhile, downregulation of CLDN6 remarkably inhibited the activation of EGFR/AKT/mTOR signalling pathway. Interestingly, the effect of CLDN6 overexpression on HepG2 cell proliferation and invasion could be inhibited by EGFR/AKT/mTOR signalling pathway inhibitor (AG1478). SIGNIFICANCE OF THE STUDY: These findings suggested that CLDN6 may act as an oncogene in HCC and improve HepG2 cell proliferation, migration, and invasion may via EGFR/AKT/mTOR signalling pathway.

Tumor necrosis factor-α triggers opposing signals in head and neck squamous cell carcinoma and induces apoptosis via mitochondrial- and non-mitochondrial-dependent pathways

Head and neck squamous cell carcinoma (HNSCC) remains one of the most common malignancies worldwide. Although the treatment outcomes of HNSCC have improved in recent years, the prognosis of patients with advanced-stage disease remains poor. Current treatment strategies for HNSCC include surgery as a primary therapy, while radio-, chemo-, and biotherapeutics can be applied as second-line therapy. Although tumor necrosis factor-α (TNF-α) is a potent tumor suppressor cytokine, the stimulation of opposing signals impairs its clinical utility as an anticancer agent. The aim of this study was to elucidate the mechanisms regulating TNF-α‑induced opposing signals and their biological consequences in HNSCC cell lines. We determined the molecular mechanisms of TNF-α-induced opposing signals in HNSCC cells. Our in vitro analysis indicated that one of these signals triggers apoptosis, while the other induces both apoptosis and cell survival. The TNF-α-induced survival of HNSCC cells is mediated by the TNF receptor-associated factor 2 (TRAF2)/nuclear factor (NF)-κB-dependent pathway, while TNF-α-induced apoptosis is mediated by mitochondrial and non-mitochondrial-dependent mechanisms through FADD-caspase-8-caspase-3 and ASK-JNK-p53-Noxa pathways. The localization of Noxa protein to both the mitochondria and endoplasmic reticulum (ER) was found to cause mitochondrial dysregulation and ER stress, respectively. Using inhibitory experiments, we demonstrated that the FADD‑caspase-8‑caspase-3 pathway, together with mitochondrial dysregulation and ER stress-dependent pathways, are essential for the modulation of apoptosis, and the NF-κB pathway is essential for the modulation of anti-apoptotic effects/cell survival during the exposure of HNSCC cells to TNF-α. Our data provide insight into the mechanisms of TNF-α-induced opposing signals in HNSCC cells and may further help in the development of novel therapeutic approaches with which to minimize the systemic toxicity of TNF-α.

Quinalizarin induces ROS‑mediated apoptosis via the MAPK, STAT3 and NF‑κB signaling pathways in human breast cancer cells

Quinalizarin has been demonstrated to exhibit potent antitumor activities in lung cancer and gastric cancer cells, but currently, little is known regarding its anticancer mechanisms in human breast cancer cells. The aim of the present study was to investigate the apoptotic effects of quinalizarin in MCF-7 cells and to analyze its molecular mechanisms. The MTT assay was used to evaluate the viability of human breast cancer cells that had been treated with quinalizarin and 5-fluorouracil. Flow cytometric analyses and western blotting were used to investigate the effects of quinalizarin on apoptosis and cycle arrest in MCF-7 cells with focus on reactive oxygen species (ROS) production. The results demonstrated that quinalizarin exhibited significant cytotoxic effects on human breast cancer cells in a dose-dependent manner. Accompanying ROS, quinalizarin induced MCF-7 cell mitochondrial-associated apoptosis by regulating mitochondrial-associated apoptosis, and caused cell cycle arrest at the G₂/M phase in a time-dependent manner. Furthermore, quinalizarin can activate p38 kinase and JNK, and inhibit the extracellular signal-regulated kinase, signal transducer and activator of transcription 3 (STAT3) and NF-κB signaling pathways. These effects were blocked by mitogen-activated protein kinase (MAPK) inhibitor and N-acetyl-L-cysteine. The results from the present study suggested that quinalizarin induced G₂/M phase cell cycle arrest and apoptosis in MCF-7 cells through ROS-mediated MAPK, STAT3 and NF-κB signaling pathways. Thus, quinalizarin may be useful for human breast cancer treatment, as well as the treatment of other cancer types.

Estrogen receptor β inhibits breast cancer cells migration and invasion through CLDN6-mediated autophagy

Background

Estrogen receptor β (ERβ) has been reported to play an anti-cancer role in breast cancer, but the regulatory mechanism by which ERβ exerts this effect is not clear. Claudin-6 (CLDN6), a tight junction protein, acts as a tumor suppressor gene in breast cancer. Our previous studies have found that 17β-estradiol (E2) induces CLDN6 expression and inhibits MCF-7 cell migration and invasion, but the underlying molecular mechanisms are still unclear. In this study, we aimed to investigate the role of ERβ in this process and the regulatory mechanisms involved.

Methods

Polymerase chain reaction (PCR) and western blot were used to characterize the effect of E2 on the expression of CLDN6 in breast cancer cells. Chromatin immunoprecipitation (ChIP) assays were carried out to confirm the interaction between ERβ and CLDN6. Dual luciferase reporter assays were used to detect the regulatory role of ERβ on the promoter activity of CLDN6. Wound healing and Transwell assays were used to examine the migration and invasion of breast cancer cells. Western blot, immunofluorescence and transmission electron microscopy (TEM) were performed to detect autophagy. Xenograft mouse models were used to explore the regulatory effect of the CLDN6-beclin1 axis on breast cancer metastasis. Immunohistochemistry (IHC) was used to detect ERβ/CLDN6/beclin1 expression in breast cancer patient samples.

Results

Here, E2 upregulated the expression of CLDN6, which was mediated by ERβ. ERβ regulated CLDN6 expression at the transcriptional level. ERβ inhibited the migration and invasion of breast cancer cells through CLDN6. Interestingly, this effect was associated with CLDN6-induced autophagy. CLDN6 positively regulated the expression of beclin1, which is a key regulator of autophagy. Beclin1 knockdown reversed CLDN6-induced autophagy and the inhibitory effect of CLDN6 on breast cancer metastasis. Moreover, ERβ and CLDN6 were positively correlated, and the expression of CLDN6 was positively correlated with beclin1 in breast cancer tissues.

Conclusion

Overall, this is the first study to demonstrate that the inhibitory effect of ERβ on the migration and invasion of breast cancer cells was mediated by CLDN6, which induced the beclin1-dependent autophagic cascade.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1359-9) contains supplementary material, which is available to authorized users.

Claudin-18 expression in oesophagogastric adenocarcinomas: a tissue microarray study of 523 molecularly profiled cases

BACKGROUND

Claudin-18 (CLDN18) is a highly specific tight junction protein of the gastric mucosa. An isoform of CLDN18, the Claudin 18.2, has recently emerged as an innovative drug target for metastatic gastric cancer.

METHODS

We investigated the immunohistochemical profile of CLDN18, p53, p16, E-cadherin, MSH2, MSH6, MLH1, PSM2, HER2, and PDL-1 in a large series of 523 primary gastric carcinomas (GCs; n = 408) and gastro-oesophageal carcinomas (GECs; n = 115) and 135 matched and synchronous nodal metastases. The status of HER2 and EBER by means of chromogenic in situ hybridisation (CISH) was also evaluated.

RESULTS

High membranous CLDN18 expression was present in 150/510 (29.4%) primary cases and in 45/132 (34.1%) metastases. An abnormal expression (i.e. nuclear and/or cytoplasmic) was observed in 115 (22.5%) primary cases and in 33 (25.0%) metastases. A 38.8% of the cases showed significant CLDN18 intratumoural variability among the different tissue microarray cores obtained from the same tumour. Positive membrane CLDN18 expression was statistically associated with non-antral GCs (p = 0.016), Lauren diffuse type (p = 0.009), and with EBV-associated cancers (p < 0.001).

CONCLUSIONS

CLDN18 is frequently expressed in gastric and gastro-oesophageal cancers; further studies should investigate the prognostic significance of CLDN18 heterogeneity in order to implement its test into clinical practice.

NADPH Oxidase Isoforms Are Involved in Glucocorticoid-Induced Preosteoblast Apoptosis

Oxidative stress induced by long-term glucocorticoid (GC) use weakens the repair capacity of bone tissue. Nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase (NOX) is a superoxide-generating enzyme that plays an important role in regulating bone metabolism. To clarify the role of nonphagocytic NOX isoforms in osteoblast reactive oxygen species (ROS) generation and apoptosis, dexamethasone was used to establish a high-dose GC environment in vitro. A dose-dependent increase in intracellular ROS generation was demonstrated, which was accompanied by increased osteoblastic MC3T3-E1 cell apoptosis. Addition of the ROS inhibitor NAC (N-acetyl-L-cysteine) or NOX inhibitor DPI (diphenyleneiodonium) reversed this effect, indicating that NOX-derived ROS can induce osteoblast apoptosis under high-dose dexamethasone stimulation. NOX1, NOX2, and NOX4 are NOX homologs recently identified in bone tissue. To clarify the NOX isoforms that play a role in osteoblast ROS generation, Nox1, Nox2, and Nox4 mRNA expression and NOX2 and NOX4 protein expression were analyzed. Nox1 and Nox4 mRNA expression was elevated in a dose-dependent manner after culture in 100 nM, 250 nM, 500 nM, or 1000 nM dexamethasone, and the increased expression of NOX1 mRNA was more significant compared with NOX4 mRNA. Small interfering RNAs (siRNAs) were used to confirm the role of NOX1 and NOX4 in ROS generation. To clarify the signaling pathway in ROS-induced osteoblast apoptosis, mitogen-activated protein kinase (MAPK) signaling molecules were analyzed. Phosphorylated ASK1 and p38 levels were significantly higher in the 1000 nM dexamethasone group, which NAC or DPI markedly attenuated. However, the total mRNA and protein levels of ASK1 and p38 between the dexamethasone group and control were not significantly different. This is related to ROS regulating the posttranslational modification of ASK1 and p38 in MC3T3-E1 cell apoptosis. Altogether, NOX1- and NOX4-derived ROS plays a pivotal role in high-dose dexamethasone-induced preosteoblast apoptosis by increasing phosphorylated ASK1 and p38 and may be an important mechanism in steroid-induced avascular necrosis of the femoral head (SANFH).

Expression of CLDN6 in tissues of gastric cancer patients: Association with clinical pathology and prognosis

Expression of claudin-6 (CLDN6) in the tissues of gastric cancer patients and its association with clinical pathology and prognosis were investigated. A retrospective analysis was performed on 213 gastric cancer patients diagnosed and surgically treated in the Central Hospital of Zibo from January 2010 to January 2013. Cancer and normal adjacent tissues were obtained from the patients to detect the expression level of CLDN6 using reverse transcription-quantitative PCR (RT-qPCR). The association between the expression level of CLDN6 and the clinical and pathological features, as well as the prognosis of gastric cancer patients was analyzed. The expression level of CLDN6 was significantly lower in gastric cancer tissues than that in adjacent tissues (t=23.350, P<0.001). The expression level of CLDN6 was associated with age, lymph node metastasis, pathological staging, and distant metastasis (P<0.05). In this study, patients were separated into CLDN6 high-expression group (≥1.42) with 107 patients and CLDN6 low-expression group (<1.42) with 106 patients, with the median expression level of CLDN6 as the boundary. The 1-, 2- and 3-year survival rates of patients in the CLDN6 low-expression group were 80.19, 60.38 and 48.11%, respectively, and those in the CLDN6 high-expression group were 87.85, 73.83 and 66.36%, respectively. The survival rate was significantly better in the CLDN6 high-expression group than that in the CLDN6 low-expression group (P=0.009). In conclusion, the expression level of CLDN6 is low in the cancer tissues of gastric cancer patients, and associated with age, lymph node metastasis, pathological staging and distant metastasis. CLDN6 low expression has a certain negative impact on the prognosis of patients, and therefore, shows potential as an important indicator for the prognosis of gastric cancer patients.

Lic regulates JNK-mediated cell death in Drosophila

Objectives

The evolutionary conserved JNK pathway plays crucial role in cell death, yet factors that modulate this signalling have not been fully disclosed. In this study, we aim to identify additional factors that regulate JNK signalling in cell death, and characterize the underlying mechanisms.

Materials and Methods

Drosophila were raised on standard media, and cross was carried out at 25°C. The Gal4/UAS system was used to express proteins or RNAi in a specific temporal and spatial pattern. Gene expression was revealed by GFP fluorescence, X‐gal staining or immunostaining of 3rd instar larval eye and wing discs. Cell death was visualized by acridine orange (AO) staining. Images of fly eyes and wings were taken by OLYMPUS microscopes.

Results

We found that licorne (lic) encoding the Drosophila MKK3 is an essential regulator of JNK‐mediated cell death. Firstly, loss of lic suppressed ectopic Egr‐triggered JNK activation and cell death in eye and wing development. Secondary, lic is necessary for loss‐of‐cell polarity‐induced, physiological JNK‐dependent cell death in wing development. Thirdly, Lic overexpression is sufficient to initiate JNK‐mediated cell death in developing eyes and wings. Furthermore, ectopic Lic activates JNK signalling by promoting JNK phosphorylation. Finally, genetic epistatic analysis confirmed that Lic acts in parallel with Hep in the Egr‐JNK pathway.

Conclusions

This study not only identified Lic as a novel component of the JNK signalling, but also disclosed the crucial roles and mechanism of Lic in cell death.

Key microRNAs in the biology of breast cancer; emerging evidence in the last decade

microRNAs (miRNAs) are a family of small noncoding RNAs that play a pivotal role in the regulation of main biological and physiological processes, including cell cycle regulation, proliferation, differentiation, apoptosis, stem cell maintenance, and organ development. Dysregulation of these tiny molecules has been related to different human diseases, such as cancer. It has been estimated that more than 50% of these noncoding RNA sequences are placed on fragile sites or cancer-associated genomic regions. After the discovery of the first specific miRNA signatures in breast cancer, many studies focused on the involvement of these small RNAs in the pathophysiology of breast tumors and their possible clinical implications as reliable prognostic biomarkers or as a new therapeutic approach. Therefore, the present review will focus on the recent findings on the involvement of miRNAs in the biology of breast cancer associated with their clinical implications.

Upregulation of miR-199 attenuates TNF-α-induced Human nucleus pulposus cell apoptosis by downregulating MAP3K5

MicroRNA-199 has been reported to play a potential role in the apoptosis of Human nucleus pulposus cells. However, the effect of miR-199 in regulating Human nucleus pulposus cell injury induced by TNF-α has not been previously illustrated. This study searched to probe the effect and the molecular mechanism of miR-199 on Human nucleus pulposus cell injury induced by TNF-α. Using the TNF-α model of Human nucleus pulposus cell in vitro, we found that miR-199 was extremely decreased in Human nucleus pulposus cells after TNF-α treatment. Knockdown the expression of miR-199 by recombinant adeno-associated viral vector infection markedly promoted the apoptosis of Human nucleus pulposus cells induced by TNF-α treatment, whereas miR-199 overexpression significantly decreased Human nucleus pulposus cell apoptosis. Both Dual-luciferase reporter and western blot assay proved that MAP3K5 was a direct target gene of miR-199, and miR-199 inhibited the expression of MAP3K5 via binding to its 3'-UTR. Furthermore, we proved that overexpression of miR-199 could inhibit the expression of MAP3K5 at the transcription and translation levels, whereas the inhibition of miR-199 could upregulate the expression of MAP3K5. Moreover, MAP3K5 was highly expressed in TNF-α treated Human nucleus pulposus cells and the apoptosis rate induced by TNF-α was associated with the increase in MAP3K5 expression. Importantly, knockdown the expression of MAP3K5 apparently abrogated the inhibitory effect of miR-199 mimics on TNF-α induced Human nucleus pulposus cell apoptosis. In conclusion, these results indicate that upregulation of miR-199 could inhibit Human nucleus pulposus cells injury through downregulation of MAP3K5 expression, providing an important molecular target mechanism for Human nucleus pulposus cells injury.

Melatonin and pancreatic cancer: Current knowledge and future perspectives

Pancreatic cancer has a high mortality rate due to the absence of early symptoms and subsequent late diagnosis; additionally, pancreatic cancer has a high resistance to radio- and chemotherapy. Multiple inflammatory pathways are involved in the pathophysiology of pancreatic cancer. Melatonin an indoleamine produced in the pineal gland mediated and receptor-independent action is the pancreas and other where has both receptors. Melatonin is a potent antioxidant and tissue protector against inflammation and oxidative stress. In vivo and in vitro studies have shown that melatonin supplementation is an appropriate therapeutic approach for pancreatic cancer. Melatonin may be an effective apoptosis inducer in cancer cells through regulation of a large number of molecular pathways including oxidative stress, heat shock proteins, and vascular endothelial growth factor. Limited clinical studies, however, have evaluated the role of melatonin in pancreatic cancer. This review summarizes what is known regarding the effects of melatonin on pancreatic cancer and the mechanisms involved.

Second-generation proteasome inhibitor carfilzomib enhances doxorubicin-induced cytotoxicity and apoptosis in breast cancer cells

Proteasome inhibition is an attractive approach for anticancer therapy. Doxorubicin (DOX) is widely used for treatment in a number of cancers including breast cancer; however, the development of DOX resistance largely limits its clinical application. One of the possible mechanisms of DOX-resistance is that DOX might induce the activation of NF-κB. In this case, proteasome inhibitors could inhibit the activation of NF-κB by blocking inhibitory factor κB (IκB) degradation. Carfilzomib, a second-generation proteasome inhibitor, overcomes bortezomib resistance and lessens its side-effects. Currently, the effect of carfilzomib on breast cancer cell proliferation remains unclear. In this study, we exploited the role of carfilzomib in seven breast cancer cell lines, MCF7, T-47D, MDA-MB-361, HCC1954, MDA-MB-468, MDA-MB-231, and BT-549, representing all major molecular subtypes of breast cancer. We found that carfilzomib alone had cytotoxic effects on the breast cancer cells and it increased DOX-induced cytotoxic effects and apoptosis in combination by enhancing DOX-induced JNK phosphorylation and inhibiting DOX-induced IκBα degradation. The results suggest that carfilzomib has potent antitumor effects on breast cancer in vitro and can sensitize breast cancer cells to DOX treatment. DOX in combination with carfilzomib may be an effective and feasible therapeutic option in the clinical trials for treating breast cancer.

CLDN6 promotes chemoresistance through GSTP1 in human breast cancer

BACKGROUND

Claudin-6 (CLDN6), a member of CLDN family and a key component of tight junction, has been reported to function as a tumor suppressor in breast cancer. However, whether CLDN6 plays any role in breast cancer chemoresistance remains unclear. In this study, we investigated the role of CLDN6 in the acquisition of chemoresistance in breast cancer cells.

METHODS

We manipulated the expression of CLDN6 in MCF-7 and MCF-7/MDR cells with lv-CLDN6 and CLDN6-shRNA and investigated whether CLDN6 manipulation lead to different susceptibilities to several chemotherapeutic agents in these cells. The cytotoxicity of adriamycin (ADM), 5-fluorouracil (5-FU), and cisplatin (DDP) was tested by cck-8 assay. Cell death was determined by DAPI nuclear staining. The enzyme activity of glutanthione S-transferase-p1 (GSTP1) was detected by a GST activity kit. Then lv-GSTP1 and GSTP1-shRNA plasmids were constructed to investigate the potential of GSTP1 in regulating chemoresistance of breast cancer. The TP53-shRNA was adopted to explore the regulation mechanism of GSTP1. Finally, immunohistochemistry was used to explore the relationship between CLDN6 and GSTP1 expression in breast cancer tissues.

RESULTS

Silencing CLDN6 increased the cytotoxicity of ADM, 5-FU, and DDP in MCF-7/MDR cells. Whereas overexpression of CLDN6 in MCF-7, the parental cell line of MCF-7/MDR expressing low level of CLDN6, increased the resistance to the above drugs. GSTP1 was upregulated in CLDN6-overexpressed MCF-7 cells. RNAi -mediated silencing of CLDN6 downregulated both GSTP1 expression and GST enzyme activity in MCF-7/MDR cells. Overexpresssion of GSTP1 in CLDN6 silenced MCF-7/MDR cells restored chemoresistance, whereas silencing GSTP1 reduced the chemoresistance due to ectopic overexpressed of CLDN6 in MCF-7 cells. These observations were also repeated in TNBC cells Hs578t. We further confirmed that CLDN6 interacted with p53 and promoted translocation of p53 from nucleus to cytoplasm, and both the expression and enzyme activity of GSTP1 were regulated by p53. Clinicopathologic analysis revealed that GSTP1 expression was positively associated with CLDN6 in human breast cancer samples.

CONCLUSION

High expression of CLDN6 confers chemoresistance on breast cancer which is mediated by GSTP1, the activity of which is regulated by p53. Our findings provide a new insight into mechanisms and strategies to overcome chemoresistance in breast cancer.

Bioinformatic analysis reveals potential properties of human Claudin-6 regulation and functions

Claudin-6 (CLDN6) is an integral component of the tight junction proteins in polarized epithelial and endothelial cells and plays a crucial role in maintaining cell integrity. Deregulation of CLDN6 expression and distribution in tumor tissues have been widely documented and correlated with cancer progression and metastasis. However, a complete mechanistic understanding of CLDN6 regulation and function remains to be studied. Herein, we show new potential properties of CLDN6 regulation and functions from bioinformatics analysis. Using numerous algorithms to characterize the CLDN6 gene promoter elements and the CLDN6 protein structure, physio-chemical and localization properties, and its evolutionary relationships. CLDN6 is regulated by a diverse set of transcription factors (SP1, SPR, AML-1a, CdxA, CRE-BP and CREB) and associated with the levels of methylation of CpG islands in promoters. The structural properties of CLDN6 indicate that it promotes cancer cell behavior via the ASK1-p38/JNK MAPK secretory signaling pathway. In conclusion, this information from bioinformatics analysis will help future attempts to better understand CLDN6 regulation and functions.

Quercetin ameliorates ischemia/reperfusion-induced cognitive deficits by inhibiting ASK1/JNK3/caspase-3 by enhancing the Akt signaling pathway

Cerebral ischemia/reperfusion (I/R) is a major cause of severe disability and death all worldwide. However, therapeutic options to minimize the detrimental effects of cerebral I/R injury are limited. Recent research has demonstrated that quercetin mediates neuroprotective effects associated with the activation of the Akt signaling pathway in the cerebral I/R brain. Therefore, the aim of this study was to further investigate the mechanisms of cognitive deficits induced by cerebral I/R injury and the effects of quercetin on these mechanisms. First, we assessed anxiety-like behavioral and cognitive impairment using the open field test and the Morris water maze test, respectively. Next, we examined the severity of apoptosis by staining hippocampal neurons by the Cresyl violet method. Third, we used western blot analysis to investigate the expression of total and phosphorylated Akt, ASK1, JNK3, c-Jun and caspase-3 after I/R injury. Our results revealed that mice subjected to bilateral common carotid occlusion exhibited severe anxiety-like behavior, learning and memory impairment, cell damage and apoptosis. These severe effects were attenuated by administration of quercetin. Further, western blot analysis revealed that quercetin increased p-Akt expression and decreased p-ASK1, p-JNK3 and cleaved caspase-3 expression after cerebral I/R injury and led to inhibition of neuronal apoptosis. Conversely, treatment with LY294002 (a selective inhibitor of Akt1) reversed the effects of quercetin. In conclusion, these findings highlight the important role of quercetin in protecting against cognitive deficits and inhibiting neuronal apoptosis via the Akt signaling pathway. We believe that quercetin might prove to be a useful therapeutic component in treating cerebral I/R diseases in the near future.