In vitro effect of Pannexin 1 channel on the invasion and migration of I-10 testicular cancer cells via ERK1/2 signaling pathway

Pannexin-1 expression in tumor cells correlates with colon cancer progression and survival

AIMS

Pannexin-1 (PANX1) is a hemichannel that releases ATP upon opening, initiating inflammation, cell proliferation, and migration. However, the role of PANX1 channels in colon cancer remains poorly understood, thus constituting the focus of this study.

MAIN METHODS

PANX1 mRNA expression was analyzed using multiple cancer databases. PANX1 protein expression and distribution were evaluated by immunohistochemistry on primary tumor tissue and non-tumor colonic mucosa from colon cancer patients. PANX1 inhibitors (probenecid or 10Panx) were used to assess colon cancer cell lines viability. To study the role of PANX1 in vivo, a subcutaneous xenograft model using HCT116 cells was performed in BALB/c NOD/SCID immunodeficient mice to evaluate tumor growth under PANX1 inhibition using probenecid.

KEY FINDINGS

PANX1 mRNA was upregulated in colon cancer tissue compared to non-tumor colonic mucosa. Elevated PANX1 mRNA expression in tumors correlated with worse disease-free survival. PANX1 protein abundance was increased on tumor cells compared to epithelial cells in paired samples, in a cancer stage-dependent manner. In vitro and in vivo experiments indicated that blocking PANX1 reduced cell viability and tumor growth.

SIGNIFICANCE

PANX1 can be used as a biomarker of colon cancer progression and blocking PANX1 channel opening could be used as a potential therapeutic strategy against this disease.

A ferroptosis-related signature predicts the clinical diagnosis and prognosis, and associates with the immune microenvironment of lung cancer

Targeting ferroptosis-related pathway is a potential strategy for treatment of lung cancer (LC). Consequently, exploration of ferroptosis-related markers is important for treating LC. We collected LC clinical data and mRNA expression profiles from TCGA and GEO database. Ferroptosis-related genes (FRGs) were obtained through FerrDB database. Expression analysis was performed to obtain differentially expressed FRGs. Diagnostic and prognostic models were constructed based on FRGs by LASSO regression, univariate, and multivariate Cox regression analysis, respectively. External verification cohorts GSE72094 and GSE157011 were used for validation. The interrelationship between prognostic risk scores based on FRGs and the tumor immune microenvironment was analyzed. Immunocytochemistry, Western blotting, and RT-qPCR detected the FRGs level. Eighteen FRGs were used for diagnostic models, 8 FRGs were used for prognostic models. The diagnostic model distinguished well between LC and normal samples in training and validation cohorts of TCGA. The prognostic models for TCGA, GSE72094, and GSE157011 cohorts significantly confirmed lower overall survival (OS) in high-risk group, which demonstrated excellent predictive properties of the survival model. Multivariate Cox regression analysis further confirmed risk score was an independent risk factor related with OS. Immunoassays revealed that in high-risk group, a significantly higher proportion of Macrophages_M0, Neutrophils, resting Natural killer cells and activated Mast cells and the level of B7H3, CD112, CD155, B7H5, and ICOSL were increased. In conclusion, diagnostic and prognostic models provided superior diagnostic and predictive power for LC and revealed a potential link between ferroptosis and TIME.

A metastasis-associated Pannexin1 mutant (Panx1 1-89 ) forms a minimalist ATP release channel

A truncated form of the ATP release channel pannexin 1 (Panx1), Panx1 1-89 , is enriched in metastatic breast cancer cells and has been proposed to mediate metastatic cell survival by increasing ATP release through mechanosensitive Panx1 channels. However, whether Panx1 1-89 on its own (without the presence of wtPanx1) mediates ATP release has not been tested. Here, we show that Panx1 1-89 by itself can form a constitutively active membrane channel, capable of releasing ATP even in the absence of wild type Panx1. Our biophysical characterization reveals that most basic structure-function features of the channel pore are conserved in the truncated Panx1 1-89 peptide. Thus, augmenting extracellular potassium ion concentrations enhances Panx1 1-89 -mediated conductance. Moreover, despite the severe truncation, Panx1 1-89 retains the sensitivity to most of wtPanx1 channel inhibitors and can thus be targeted. Therefore, Panx1 blockers have the potential to be of therapeutic value to combat metastatic cell survival. Our study not only elucidates a mechanism for ATP release from cancer cells, but it also supports that the Panx1 1-89 mutant should facilitate structure-function analysis of Panx1 channels.

Baicalin inhibited PANX-1/P2Y6 signaling pathway activation in porcine aortic vascular endothelial cells infected by Glaesserella parasuis

Glaesserella parasuis can induce endothelial barrier damage in piglets, although the mechanism by which this pathogen triggers inflammatory damage remains unclear. Baicalin possesses anti-inflammatory and anti-oxidant activities. However, whether baicalin can relieve endothelial barrier damage caused by Glaesserella parasuis infection has not yet been studied. Hence, we evaluated the ability of baicalin to counteract the changes induced by Glaesserella parasuis in porcine aortic vascular endothelial cells. The results showed that Glaesserella parasuis could upregulate the expression of pannexin 1 channel protein and promote the release of adenosine triphosphate, adenosine diphosphate, adenosine 3'-monophosphate, uridine triphosphate, uridine diphosphate, and uridine monophosphate in porcine aortic vascular endothelial cells. The expression level of purinergic receptor P2Y6 was upregulated in porcine aortic vascular endothelial cells triggered by Glaesserella parasuis. In addition, Glaesserella parasuis could activate phospholipase C-protein kinase C and myosin light chain kinase-myosin light chain signaling pathways in porcine aortic vascular endothelial cells. Baicalin could inhibit pannexin 1 channel protein expression, reduce adenosine triphosphate, adenosine diphosphate, adenosine 3'-monophosphate, uridine triphosphate, uridine diphosphate, and uridine monophosphate release, and attenuate the expression level of P2Y6 in porcine aortic vascular endothelial cells induced by Glaesserella parasuis. Baicalin could also reduce the activation of phospholipase C-protein kinase C and myosin light chain kinase-myosin light chain signaling pathways in porcine aortic vascular endothelial cells triggered by Glaesserella parasuis. Our study report that Glaesserella parasuis could promote pannexin 1 channel protein expression, induce nucleosides substance release, and P2Y6 expression in porcine aortic vascular endothelial cells and baicalin could inhibit the expression levels of pannexin 1, nucleosides substance, and P2Y6 in the porcine aortic vascular endothelial cells induced by Glaesserella parasuis, which might be served as some targets for treatment of inflammation disease caused by Glaesserella parasuis.

FZKA reverses gefitinib resistance by regulating EZH2/Snail/EGFR signaling pathway in lung adenocarcinoma

ETHNOPHARMACOLOGICAL RELEVANCE

Fuzheng Kang-Ai (FZKA) decoction is mainly composed of 12 components with different types of herbs. In the last decade, FZKA has been used as an adjuvant treatment for lung cancer in clinical practice. Our previous studies have confirmed that FZKA shows a strong anti-cancer activity, significantly increases the clinical efficacy of gefitinib and reverses gefitinib resistance in non-small cell lung cancer (NSCLC). However, the molecular mechanism still needs to be further elucidated.

AIM OF THE STUDY

The aim of this study was to investigate the role and mechanism by which FZKA inhibited the cell growth, proliferation and invasion of lung adenocarcinoma(LUAD) and reversed the acquired resistance of gefitinib for the therapy in LUAD.

MATERIALS AND METHODS

Cell viability assay and EDU assay were used for detecting of cell viability and cell proliferation. Transwell assay was performed to measure cell invasion. Western Blot and qRT-PCR were used for protein and gene expression test. The gene promoter activity was determined by dul-luciferase reporter assay. The in situ expression of protein was measured by cell immunofluorescence. Stabilized cell lines were established for stable overexpression of EZH2. Transient transfection assay was used for gene silence and overexpression. Xenograft tumors and bioluminescent imaging were used for in vivo experiments.

RESULTS

FZKA significantly inhibited the cell viability, proliferation and cell invasion of LUAD, the combination of FZKA and gefitinib had a great synergy on the above processes. Moreover, FZKA significantly decreased EZH2 mRNA and protein expression, FZKA reversed the resistance of gefitinib by down-regulation of EZH2 protein. ERK1/2 kinase mediated the down-regulation of EZH2 reduced by FZKA. In addition, FZKA decreased the expression of Snail and EGFR by decreasing EZH2. Overexpression of Snail and EGFR significantly reversed the effect of FZKA-inhibited cell invasion and cell proliferation. More important, the combination of FZKA and gefitinib enhanced the inhibitory effect on EZH2, Snail and EGFR proteins. Furthermore, the growth inhibition and reversal of gefitinib resistance induced by FZKA were further validated in vivo. Finally, the expression and clinical correlation of EZH2,EGFR and Snail in cancer patients were further validated using bioinformatics analysis.

CONCLUSIONS

FZKA significantly suppressed tumor progression and reversed gefitinib resistance by regulating the p-ERK1/2-EZH2-Snail/EGFR signaling pathway in LUAD.

Action mechanism of snake venom l-amino acid oxidase and its double-edged sword effect on cancer treatment: Role of pannexin 1-mediated interleukin-6 expression

Snake venom l-amino acid oxidases (svLAAOs) have been recognized as promising candidates for anticancer therapeutics. However, multiple aspects of their catalytic mechanism and the overall responses of cancer cells to these redox enzymes remain ambiguous. Here, we present an analysis of the phylogenetic relationships and active site-related residues among svLAAOs and reveal that the previously proposed critical catalytic residue His 223 is highly conserved in the viperid but not the elapid svLAAO clade. To gain further insight into the action mechanism of the elapid svLAAOs, we purify and characterize the structural, biochemical, and anticancer therapeutic potentials of the Thailand elapid snake Naja kaouthia LAAO (NK-LAAO). We find that NK-LAAO, with Ser 223, exhibits high catalytic activity toward hydrophobic l-amino acid substrates. Moreover, NK-LAAO induces substantial oxidative stress-mediated cytotoxicity with the magnitude relying on both the levels of extracellular hydrogen peroxide (H₂O₂) and intracellular reactive oxygen species (ROS) generated during the enzymatic redox reactions, but not being influenced by the N-linked glycans on its surface. Unexpectedly, we discover a tolerant mechanism deployed by cancer cells to dampen the anticancer activities of NK-LAAO. NK-LAAO treatment amplifies interleukin (IL)-6 expression via the pannexin 1 (Panx1)-directed intracellular calcium (iCa²⁺) signaling pathway to confer adaptive and aggressive phenotypes on cancer cells. Accordingly, IL-6 silencing renders cancer cells vulnerable to NK-LAAO-induced oxidative stress together with abrogating NK-LAAO-stimulated metastatic acquisition. Collectively, our study urges caution when using svLAAOs in cancer treatment and identifies the Panx1/iCa²⁺/IL-6 axis as a therapeutic target for improving the effectiveness of svLAAOs-based anticancer therapies.

Mesoscopic structural analysis via deep learning processing, with a special reference to in vitro alteration in collagen fibre induced by a gap junction inhibitor

Dense connective tissue, including the ligament, tendon, fascia and cornea, is formed by regularly arranged collagen fibres synthesized by fibroblasts (Fbs). The mechanism by which fibre orientation is determined remains unclear. Periodontal ligament Fbs consistently communicate with their surroundings via gap junctions (GJs), leading to the formation of a wide cellular network. A method to culture Fb-synthesized collagen fibres was previously reported by Schafer et al. ('Ascorbic acid deficiency in cultured human fibroblasts'. J. Cell Biol. 34: 83-95, 1967). This method has been applied to investigate the ability and activity of Fb collagen synthesis/phagocytosis using conventional electron microscopy (EM). However, the three-dimensional mesoscopic architecture of collagen fibres and the influence of GJ inhibitors on collagen fibre formation in vitro are poorly understood. In this study, three-dimensional mesoscopic analysis was used to elucidate the mechanism of directional fibre formation. We investigated the influence of GJ inhibitors on collagen formation driven by periodontal ligament Fbs in vitro, histomorphometrically, and the structural properties of in vitro collagen fibre on a mesoscale quantitatively, using correlative light and EM optimized for picrosirius red staining and focused ion beam-scanning EM tomography. Our results indicate that under culture conditions, in the presence of a GJ inhibitor, the orientation of collagen fibres becomes more disordered than that in the control group. This suggests that the GJ might be involved in determining fibre orientation during collagen fibre formation. Elucidation of this mechanism may help develop novel treatment strategies for connective tissue orientation disorders. Graphical Abstract.

StarD7 deficiency hinders cell motility through p-ERK1/2/Cx43 reduction

StarD7 belongs to START protein family involved in lipid traffic, metabolism, and signaling events. Its precursor, StarD7.I which is important for mitochondrial homeostasis, is processed to the StarD7.II isoform that lacks the mitochondrial targeting sequence and is mainly released to the cytosol. StarD7 knockdown interferes with cell migration by an unknown mechanism. Here, we demonstrate that StarD7 silencing decreased connexin 43 (Cx43), integrin β1, and p-ERK1/2 expression in the non-tumoral migratory HTR-8/SVneo cells. StarD7-deficient cells exhibited Golgi disruption and reduced competence to reorient the microtubule-organizing center. The migratory capacity of StarD7-silenced cells was reestablished when Cx43 level was resettled, while p-ERK1/2 expression remained low. Importantly, ectopic expression of the StarD7.II isoform not only restored cell migration but also ERK1/2, Cx43, and integrin β1 expression. Thus, StarD7 is implicated in cell migration through an ERK1/2/Cx43 dependent mechanism but independent of the StarD7.I function in the mitochondria.

Potential Implications of Exercise Training on Pannexin Expression and Function

Pannexins (PANX1, 2, 3) are channel-forming glycoproteins that are expressed throughout the cardiovascular and musculoskeletal system. The canonical function of these proteins is to release nucleotides that act as purinergic signalling at the cell membrane or Ca2+ channels at the endoplasmic reticulum membrane. These two forms of signalling are essential for autocrine and paracrine signalling in health, and alterations in this signalling have been implicated in the pathogenesis of many diseases. Many musculoskeletal and cardiovascular diseases are largely the result of a lack of physical activity which causes altered gene expression. Considering exercise training has been shown to alter a wide array of gene expression in musculoskeletal tissues, understanding the interaction between exercise training, gene function and expression in relevant diseases is warranted. With regards to pannexins, multiple publications have shown that exercise training can influence pannexin expression and may influence the significance of its function in certain diseases. This review further discusses the potential interaction between exercise training and pannexin biology in relevant tissues and disease models. We propose that exercise training in relevant animal and human models will provide a more comprehensive understanding of the implications of pannexin biology in disease.

High PANX1 Expression Leads to Neutrophil Recruitment and the Formation of a High Adenosine Immunosuppressive Tumor Microenvironment in Basal-like Breast Cancer

Background: A high adenosine level is an important characteristic of the tumor microenvironment (TME) in breast cancer. Pannexin 1 (PANX1) can release intracellular ATP to the extracellular space and elevate extracellular ATP (exATP) levels under physiological conditions. Methods: We performed public database bioinformatics analysis, surgical specimen histological validation, RNA sequencing, and exATP/extracellular adenosine (exADO) assays to reveal the role of PANX1 in regulating the immune microenvironment of basal-like breast cancer. Results: Our results revealed that PANX1 acted as a poor prognostic factor for breast cancer and had high expression in basal-like breast cancer. PANX1 expression was positively correlated with exATP and exADO levels in basal-like breast cancer TME. PANX1 expression was also positively correlated with tumor-associated neutrophil (TAN) infiltration in breast cancer TME and TANs highly expressed ENTPD1 (CD39)/NT5E (CD73). Conclusions: This study suggests that high PANX1 expression is associated with high TAN infiltration and adenosine production to induce local immunosuppression in basal-like breast cancer TME.

Pannexin1 inhibits autophagy of cisplatin-resistant testicular cancer cells by mediating ATP release

Pannexin1 (Panx-1) is a gap junction channel protein that mediates the release of intracellular ATP during autophagy, and thus plays an important role in tumor cell apoptosis and chemo-resistance. However, the role of Panx-1 in cisplatin-resistance of testicular cancer cells remains unclear. We found that cisplatin-resistant I-10 testicular cancer cell lines (I-10/CDDP) autophagy-associated proteins (p62, p-mTOR, mTOR and LC3) exhibited high levels of autophagy in their expression, while LC3-II expression was more significantly in the presence of lysosomal degradation blocked by chloroquine (CQ). Xenograft models using I-10/CDDP cells with knockdown ATG5 and ATG7 were established in mouse models and showed blockade of autophagic flux and inhibition of tumor growth. In addition, inhibition of Panx-1 by carbenoxolone (CBX) and probenecid (PBN), as well as shRNA-mediated knockdown promoted autophagy in the I-10/CDDP cells, which was accompanied by a decrease in the levels of extracellular ATP. In contrast, overexpression of Panx-1 decreased autophagy of I-10/CDDP cells and increased extracellular ATP levels. To further determine the effect of panx-1-mediated ATP release on the autophagy of I-10/CDDP cells, apyrase was used to hydrolyze the extracellular ATP. Apyrase promoted autophagy in I-10/CDDP cells city by decreasing extracellular ATP, regardless of Panx-1 expression. This study demonstrated for the first time that Panx-1-mediated ATP release inhibits autophagy of I-10/CDDP cells, which provides a potential therapeutic strategy for cisplatin-resistant testicular cancer.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

Role of purinergic system and vitamin D in the anti-cancer immune response

For several years, scientists have recognized that vitamin D plays an important role in mineral and bone homeostasis. It was mostly used to treat osteoporosis and rickets in the past decades. Vitamin D has also been discovered to be modulator of the immune system and may play a role in a variety of diseases, including autoimmune diseases, in recent years. Vitamin D interaction with the vitamin D receptor (VDR), which has transcriptional imparts and is displayed on a variety of cell types, including those of the immune system, appears to be accountable for the immune-modulating effects. The action of tumor cells and vitamin D were the first to be investigated, but the spotlight is now on immunologic and purinergic systems. We conducted a systematic search in Pub Med as well as Google scholar for studies written in English. Vitamin D, cancer, purinergic signaling, and immune response were among the search words. Vitamin D has the potential to be a useful coadjuvant in cancer therapy and the purinergic system may be a potential treatment target to cancer therapy, according to our findings.

Inhibiting of circ-TLK1 inhibits the progression of glioma through down-regulating PANX1 via targeting miR-17-5p

Glioma remains the most common malignant tumors in the central nervous system and often has poor prognosis. In recent years, it has been gradually revealed that non-coding RNA effects glioma progression. In this study, we aimed to investigate the significance of circular RNA TLK1 (Circ-TLK1) in predicting the survival of glioma patients as well as its role in glioma development via both in-vitro and in-vivo experiments. We found that Circ-TLK1 was conspicuously up-regulated in glioma tissues compared with adjacent normal tissues, and the up-regulated Circ-TLK1 was significantly correlated with glioma patients' larger tumor volume and higher grades. Functionally, Circ-TLK1 over-expression facilitated glioma growth, migration and invasion, inhibited cell apoptosis, and accelerated PANX1/MAPK/ERK expression, while Circ-TLK1 low expression had the opposite effects. In addition, bioinformatics analysis showed that miR-17-5p was a potential target of Circ-TLK1 and targeted at PANX1. Furthermore, through dual luciferase viability assay, Circ-TLK1 acted as a competing endogenous RNA by sponging miR-17-5p, which targeted and inhibited PANX1/MAPK/ERK expression. MiR-17-5p overexpression mitigated glioma progression, which was significantly inhibited with Circ-TLK1 upregulation. In conclusion, this study confirmed a novel axis of Circ-TLK1-miR-17-5p-PANX1 in modulating glioma development, providing more references for glioma diagnosis and targeted therapy.

Pannexin biology and emerging linkages to cancer

Pannexins are a family of glycoproteins that comprises three members, PANX1, PANX2, and PANX3. The widely expressed and interrogated PANX1 forms heptameric membrane channels that primarily serve to connect the cytoplasm to the extracellular milieu by being selectively permeable to small signaling molecules when activated. Apart from notable exceptions, PANX1 in many tumor cells appears to facilitate tumor growth and metastasis, suggesting that pannexin-blocking therapeutics may have utility in cancer. Attenuation of PANX1 function must also consider the fact that PANX1 is found in stromal cells of the tumor microenvironment (TME), including immune cells. This review highlights the key discoveries of the past 5 years that suggest pannexins facilitate, or in some cases inhibit, tumor cell growth and metastasis via direct protein interactions and through the regulated efflux of signaling molecules.

Identification of a Novel Immune Landscape Signature for Predicting Prognosis and Response of Endometrial Carcinoma to Immunotherapy and Chemotherapy

Uterine Corpus Endometrial Carcinoma (UCEC) is the most common gynecological cancer. Here, we have investigated the significance of immune-related genes in predicting the prognosis and response of UCEC patients to immunotherapy and chemotherapy. Based on the Cancer Genome Atlas (TCGA) database, the single-sample gene-set enrichment analysis (ssGSEA) scores was utilized to obtain enrichment of 29 immune signatures. Univariate, multivariate Cox regression and least absolute shrinkage and selection operator (LASSO) regression analyses were performed to generate an immune-related prognostic signature (IRPS). The biological functions of IRPS-associated genes were evaluated using GSEA, Tumor Immune Estimation Resource (TIMER) Database analysis, Mutation analysis, Immunophenoscore (IPS) analysis, Gene Expression Profiling Interactive Analysis (GEPIA), Genomics of Drug Sensitivity in Cancer (GDSC) and Immune Cell Abundance Identifier (ImmuCellAI). Potential small molecule drugs for UCEC were predicted using the connectivity map (Cmap). The mRNA and protein expression levels of IRPS-associated genes were tested via quantitative real-time PCR (qPCR) and immunohistology. Two immune-related genes (CCL13 and KLRC1) were identified to construct the IRPS. Both genes were related to the prognosis of UCEC patients (P < 0.05). The IRPS could distinguish patients with different prognosis and was closely associated with the infiltration of several types of immune cells. Our findings showed that patients with low IRPS benefited more from immunotherapy and developed stronger response to several chemotherapies, which was also confirmed by the results of ImmuCellAI. Finally, we identified three small molecular drugs that might improve the prognosis of patients with high IRPS. IRPS can be utilized to predict the prognosis of UCEC patients and provide valuable information about their therapeutic response to immunotherapy and chemotherapy.

Pannexin 1 Mediates Gastric Cancer Cell Epithelial-Mesenchymal Transition via Aquaporin 5

Pannexin 1 (PANX1) has been implicated in cancer emergence and progression. However, its roles in gastric cancer remain unclear. In the present study, the function and molecular mechanisms of PANX1 in gastric cancer were investigated in vitro. Two gastric cancer cell lines exhibiting low and high PANX1 expression (SNU-16 and HCG-27, respectively) were transfected using a PANX1-containing plasmid or PANX1 transcript-targeting short hairpin (sh)RNA. In addition, HCG-27 cells and PANX1-overexpressing SNU-16 cells were subjected to short interfering (si)RNA-mediated aquaporin 5 (AQP5) knockdown. In vitro cell migration (scratch) and transwell invasion assays were performed to evaluate the cell migratory and invasive abilities. Real-time fluorescence quantitative PCR was used to detect transcripts encoding epithelial-mesenchymal transition markers. Immunofluorescence and Western blotting were conducted to quantify corresponding proteins. In SNU-16 cells, PANX1 overexpression induced conversion from round (cobblestone-like) to elongated (spindle-like) morphologies and enhanced the cell migratory and invasive abilities. PANX1 knockdown had the opposite effect in HGC-27 cells. In PANX1-overexpressing SNU-16 cells, expression of SLUG, vimentin, and AQP5 was significantly upregulated, whereas expression of E-cadherin was downregulated. In HGC-27 cells, PANX1 knockdown showed the opposite effect. In both PANX1-overexpressing SNU-16 cells and untransfected HGC-27 cells, silencing of AQP5 expression significantly inhibited PANX1-induced upregulation of SLUG and vimentin expression, as well as downregulation of E-cadherin expression and enhanced migratory and invasive abilities. In summary, elevated PANX1 expression induces gastric cancer cell epithelial-mesenchymal transition and the associated promotion of migratory and invasive abilities by inducing expression of AQP5, which facilitates SLUG-mediated regulation of vimentin and E-cadherin expression.

Pleiotropic effects of probenecid on three-dimensional cultures of prostate cancer cells

AIMS

Chemoresistance remains a persistent challenge in advanced prostate cancer therapy. Probenecid reportedly inhibits multiple drug-efflux transporters; hence, it can be employed as a potential sensitizer for chemotherapy. In the present study, we evaluated the effects of probenecid on three-dimensional (3D)-cultures of prostate cancer cells.

MAIN METHODS

Prostate cancer cell lines, 22Rv1 and PC-3 were cultured as multicellular tumor spheroids. The effects of probenecid were evaluated using the MTT assay for viability, microscopy for spheroid size, and soft agar colony formation assay for anchorage-independent growth.

KEY FINDINGS

The 3D-cultured 22Rv1 cells were less sensitive to cisplatin and doxorubicin than two-dimensional (2D) cell culture. Co-administration of probenecid at a low (100 or 300 μM), but not high (500 μM), concentration increased the sensitivity to cisplatin or doxorubicin in 22Rv1 spheroids. Probenecid increased the expression of ABCG2, a multidrug resistance transporter, in a dose-dependent manner. Furthermore, treatment with probenecid alone reduced the growth of 22Rv1 spheroids. Conversely, probenecid inhibited spheroid compaction rather than growth inhibition in 3D-cultured PC-3 cells. Moreover, probenecid inhibited colony formation of 22Rv1 and PC-3 cells in soft agar, as well as downregulated focal adhesion kinase (FAK), a crucial factor in anchorage-independent growth.

SIGNIFICANCE

In 3D-cultured prostate cancer cells, probenecid demonstrated pleiotropic effects such as chemosensitization, growth suppression, inhibition of spheroid compaction, and suppression of anchorage-independent growth. Elucidating the detailed mechanism underlying these probenecid actions could result in the identification of novel therapeutic targets toward the advanced prostate cancer.

PANX2 and brain lower grade glioma genesis: A bioinformatic analysis

PANX2 forms large-pore channels mediating ATP release in response to physiological and pathological stimuli. Although PANX2 shows involvements in glioma genesis, the underlying mechanism remains unclear. PANX2 mRNA expression was analyzed via Oncomine and was confirmed via Gene Expression Profiling Interactive Analysis (GEPIA). The influence of PANX2 on overall survival (OS) of glioma was evaluated using LinkedOmics and further assessed through Cox regression analysis. The correlated genes with PANX2 acquired from LinkedOmics were validated through GEPIA and cBioPortal. Protein-protein interaction (PPI) of these genes was then obtained using Search Tool for the Retrieval of Interacting Genes (STRING) and Cytoscape with MCODE plug-in. All the PANX2-related genes underwent Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. The correlation between PANX2 and cancer immune infiltrates was evaluated via Tumor Immune Estimation Resource (TIMER). A higher expression of PANX2 only revealed a better OS in brain low grade glioma (LGG). PANX2-related genes in LGG functionally enriched in neuroactive ligand-receptor interaction, synaptic vesicle cycle, and calcium signaling. The hub genes from highest module of PPI were mainly linked to chemical synaptic transmission, plasma membrane, neuropeptide, and the pathway of neuroactive ligand-receptor interaction. Besides, PANX2 expression was negatively associated with infiltrating levels of macrophage, dendritic cells, and CD4+ T cells. This study demonstrated that PANX2 likely participated in LGG pathogenesis by affecting multiple molecular pathways and immune-related processes. PANX2 was associated with LGG prognosis and might become a promising therapeutic target of LGG.

Identification of pannexin 1-regulated genes, interactome, and pathways in rhabdomyosarcoma and its tumor inhibitory interaction with AHNAK

Rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children, is an aggressive cancer with a poor prognosis. Despite current management, the 5-year survival rate for patients with metastatic RMS is ∼30%; underscoring the need to develop better treatment strategies. We have recently reported that pannexin 1 (PANX1) levels are downregulated in RMS and that restoring its expression inhibits RMS progression. Here, we have surveyed and characterized the molecular changes induced by PANX1 re-expression in RMS. We cataloged transcriptomic changes in this context by RNA sequencing. At the protein level, we unveiled PANX1 interactors using BioID, complemented by co-immunoprecipitation coupled to high-performance liquid chromatography/electrospray ionization tandem mass spectrometry performed in PANX1-enriched fractions. Using these data, we generated searchable public databases for the PANX1 interactome and changes to the RMS transcriptome occurring when PANX1 expression is restored. STRING network analyses revealed a PANX1 interactome involving plasma membrane and cytoskeleton-associated proteins including the previously undescribed interactor AHNAK. Indeed, AHNAK knockdown abrogated the PANX1-mediated reduction in RMS cell viability and migration. Using these unbiased approaches, we bring insight to the mechanisms by which PANX1 inhibits RMS progression, identifying the cell migration protein AHNAK as a key modifier of PANX1-mediated changes in RMS malignant properties.

Roles of Farnesyl-Diphosphate Farnesyltransferase 1 in Tumour and Tumour Microenvironments

Farnesyl-diphosphate farnesyltransferase 1 (FDFT1, squalene synthase), a membrane-associated enzyme, synthesizes squalene via condensation of two molecules of farnesyl pyrophosphate. Accumulating evidence has noted that FDFT1 plays a critical role in cancer, particularly in metabolic reprogramming, cell proliferation, and invasion. Based on these advances in our knowledge, FDFT1 could be a potential target for cancer treatment. This review focuses on the contribution of FDFT1 to the hallmarks of cancer, and further, we discuss the applicability of FDFT1 as a cancer prognostic marker and target for anticancer therapy.

Development and validation of a six-RNA binding proteins prognostic signature and candidate drugs for prostate cancer

The dysregulation of RNA binding proteins (RBPs) regulates the progression of several cancers. However, information on the overall functions of RBPs in prostate cancer (PCa) remains largely understudied. Therefore, based on the TCGA dataset, this study identified 144 differentially expressed RBPs in tumors compared to normal tissues. Subsequently, through univariate, LASSO and multivariate Cox regression analysis, 6 RBP genes among them, MSI1, MBNL2, LENG9, REXO2, RNASE1, and PABPC1L were screened as prognostic hub genes and prognostic signature was further identified. Further analysis indicated that the high-risk group was significantly associated with poor RFS, which was validated in the MSKCC cohort. Besides, patients in the high-risk group were closely associated with dysregulation of DNA damage repair pathway, copy number alteration, tumor burden mutation, and low-response to cisplatin (P < 0.001), and bicalutamide (P < 0.001). Using the Connectivity Map, we finally predicted 3 drugs including, ribavirin, carmustine, and carbenoxolone. In summary, we identified six-RBP gene signature and 3 potential drugs against PCa, which might promote the individualized treatment strategies and further improve the quality of life among PCa patients.

Purinergic Signaling in the Hallmarks of Cancer

Cancer is a complex expression of an altered state of cellular differentiation associated with severe clinical repercussions. The effort to characterize this pathological entity to understand its underlying mechanisms and visualize potential therapeutic strategies has been constant. In this context, some cellular (enhanced duplication, immunological evasion), metabolic (aerobic glycolysis, failure in DNA repair mechanisms) and physiological (circadian disruption) parameters have been considered as cancer hallmarks. The list of these hallmarks has been growing in recent years, since it has been demonstrated that various physiological systems misfunction in well-characterized ways upon the onset and establishment of the carcinogenic process. This is the case with the purinergic system, a signaling pathway formed by nucleotides/nucleosides (mainly adenosine triphosphate (ATP), adenosine (ADO) and uridine triphosphate (UTP)) with their corresponding membrane receptors and defined transduction mechanisms. The dynamic equilibrium between ATP and ADO, which is accomplished by the presence and regulation of a set of ectonucleotidases, defines the pro-carcinogenic or anti-cancerous final outline in tumors and cancer cell lines. So far, the purinergic system has been recognized as a potential therapeutic target in cancerous and tumoral ailments.

Pannexin1 Is Associated with Enhanced Epithelial-To-Mesenchymal Transition in Human Patient Breast Cancer Tissues and in Breast Cancer Cell Lines

Loss of connexin-mediated cell-cell communication is a hallmark of breast cancer progression. Pannexin1 (PANX1), a glycoprotein that shares structural and functional features with connexins and engages in cell communication with its environment, is highly expressed in breast cancer metastatic foci; however, PANX1 contribution to metastatic progression is still obscure. Here we report elevated expression of PANX1 in different breast cancer (BRCA) subtypes using RNA-seq data from The Cancer Genome Atlas (TCGA). The elevated PANX1 expression correlated with poorer outcomes in TCGA BRCA patients. In addition, gene set enrichment analysis (GSEA) revealed that epithelial-to-mesenchymal transition (EMT) pathway genes correlated positively with PANX1 expression. Pharmacological inhibition of PANX1, in MDA-MB-231 and MCF-7 breast cancer cells, or genetic ablation of PANX1, in MDA-MB-231 cells, reverted the EMT phenotype, as evidenced by decreased expression of EMT markers. In addition, PANX1 inhibition or genetic ablation decreased the invasiveness of MDA-MB-231 cells. Our results suggest PANX1 overexpression in breast cancer is associated with a shift towards an EMT phenotype, in silico and in vitro, attributing to it a tumor-promoting effect, with poorer clinical outcomes in breast cancer patients. This association offers a novel target for breast cancer therapy.