Cx31.1 acts as a tumour suppressor in non-small cell lung cancer (NSCLC) cell lines through inhibition of cell proliferation and metastasis

Pan-cancer analysis of GJB5 as a novel prognostic and immunological biomarker

Gap junction protein B5 (GJB5, also known as Connexin 31.1) has recently been reported to be downregulated in several cancer types, where it functions primarily as a tumor suppressor in cancers such as melanoma and non-small cell lung cancer (NSCLC). However, there no reports describing its prognostic and immunological roles in pan-cancer. This study evaluated the association of GJB5 in various cancer types by a comprehensive pan-cancer analysis. The differential GJB5 expression in tumor and adjacent tissues acquired from The Cancer Genome Atlas (TCGA) databases was compared. Furthermore, univariate Cox regression and Kaplan-Meier survival analyses were performed to assess the influence of GJB5 on the disease-specific survival (DSS), disease-free interval (DFI), clinical stage, progression-free interval (PFI), and overall survival (OS) in various cancers. Moreover, the levels of GJB5 and its activity in the tumor microenvironment were assessed via the Tumor Immune Single-cell Hub (TISCH). In addition, the biological importance of GJB5 levels in various cancers was further assessed via Gene Set Enrichment Analysis. Tumor-Immune System Interactions Database (TISIDB) and Tumor Immune Estimation Resource Database 2.0 (TIMER2.0) tools indicated that GJB5 affected the tumor's immune infiltration potential. This research also evaluated the association of GJB5 with immune features: immune modulatory genes, tumor mutational burden (TMB), and microsatellite instability (MSI). The data indicated that enhanced GJB5 level was linked to worse DFI, OS, PFI, and DSS in some cancers. Additionally, GJB5 level was positively related to immune modulatory genes, TMB, immune cell infiltration, immunological checkpoints, and MSI in malignancies. Furthermore, our study demonstrated that GJB5 was upregulated in colorectal cancer tissues compared to normal tissues. We also assessed GJB5 expression across various pancreatic cell lines. Notably, GJB5 was highly expressed in pancreatic cancer cells relative to normal pancreatic epithelial cells. Additionally, GJB5 knockdown in pancreatic cancer cells resulted in a significant reduction in cell proliferation. In summary, the findings indicated the potential of GJB5 as a prospective prognostic indicator and immunological biomarker.

Impairment of α-tubulin and F-actin interactions of GJB3 induces aneuploidy in urothelial cells and promotes bladder cancer cell invasion

BACKGROUND

We have previously identified an unsuspected role for GJB3 showing that the deficiency of this connexin protein induces aneuploidy in human and murine cells and accelerates cell transformation as well as tumor formation in xenograft models. The molecular mechanisms by which loss of GJB3 leads to aneuploidy and cancer initiation and progression remain unsolved.

METHODS

GJB3 expression levels were determined by RT-qPCR and Western blot. The consequences of GJB3 knockdown on genome instability were assessed by metaphase chromosome counting, multinucleation of cells, by micronuclei formation and by the determination of spindle orientation. Interactions of GJB3 with α-tubulin and F-actin was analyzed by immunoprecipitation and immunocytochemistry. Consequences of GJB3 deficiency on microtubule and actin dynamics were measured by live cell imaging and fluorescence recovery after photobleaching experiments, respectively. Immunohistochemistry was used to determine GJB3 levels on human and murine bladder cancer tissue sections. Bladder cancer in mice was chemically induced by BBN-treatment.

RESULTS

We find that GJB3 is highly expressed in the ureter and bladder epithelium, but it is downregulated in invasive bladder cancer cell lines and during tumor progression in both human and mouse bladder cancer. Downregulation of GJB3 expression leads to aneuploidy and genomic instability in karyotypically stable urothelial cells and experimental modulation of GJB3 levels alters the migration and invasive capacity of bladder cancer cell lines. Importantly, GJB3 interacts both with α-tubulin and F-actin. The impairment of these interactions alters the dynamics of these cytoskeletal components and leads to defective spindle orientation.

CONCLUSION

We conclude that deregulated microtubule and actin dynamics have an impact on proper chromosome separation and tumor cell invasion and migration. Consequently, these observations indicate a possible role for GJB3 in the onset and spreading of bladder cancer and demonstrate a molecular link between enhanced aneuploidy and invasive capacity cancer cells during tumor cell dissemination.

Understanding the Role of Connexins in Hepatocellular Carcinoma: Molecular and Prognostic Implications

Connexins, a family of tetraspan membrane proteins forming intercellular channels localized in gap junctions, play a pivotal role at the different stages of tumor progression presenting both pro- and anti-tumorigenic effects. Considering the potential role of connexins as tumor suppressors through multiple channel-independent mechanisms, their loss of expression may be associated with tumorigenic activity, while it is hypothesized that connexins favor the clonal expansion of tumor cells and promote cell migration, invasion, and proliferation, affecting metastasis and chemoresistance in some cases. Hepatocellular carcinoma (HCC), characterized by unfavorable prognosis and limited responsiveness to current therapeutic strategies, has been linked to gap junction proteins as tumorigenic factors with prognostic value. Notably, several members of connexins have emerged as promising markers for assessing the progression and aggressiveness of HCC, as well as the chemosensitivity and radiosensitivity of hepatocellular tumor cells. Our review sheds light on the multifaceted role of connexins in HCC pathogenesis, offering valuable insights on recent advances in determining their prognostic and therapeutic potential.

Cx31.1 can selectively intermix with co-expressed connexins to facilitate its assembly into gap junctions

Connexins are channel-forming proteins that function to facilitate gap junctional intercellular communication. Here, we use dual cell voltage clamp and dye transfer studies to corroborate past findings showing that Cx31.1 (encoded by GJB5) is defective in gap junction channel formation, illustrating that Cx31.1 alone does not form functional gap junction channels in connexin-deficient mammalian cells. Rather Cx31.1 transiently localizes to the secretory pathway with a subpopulation reaching the cell surface, which is rarely seen in puncta reminiscent of gap junctions. Intracellular retained Cx31.1 was subject to degradation as Cx31.1 accumulated in the presence of proteasomal inhibition, had a faster turnover when Cx43 was present and ultimately reached lysosomes. Although intracellularly retained Cx31.1 was found to interact with Cx43, this interaction did not rescue its delivery to the cell surface. Conversely, the co-expression of Cx31 dramatically rescued the assembly of Cx31.1 into gap junctions where gap junction-mediated dye transfer was enhanced. Collectively, our results indicate that the localization and functional status of Cx31.1 is altered through selective interplay with co-expressed connexins, perhaps suggesting Cx31.1 is a key regulator of intercellular signaling in keratinocytes.

Interplay between paclitaxel, gap junctions, and kinases: unraveling mechanisms of action and resistance in cancer therapy

This comprehensive review elucidates the multifaceted roles of paclitaxel, a key chemotherapeutic agent, in cancer therapy, with a focus on its interactions with gap junctions and related kinases. Paclitaxel, with its complex diterpene structure, mediates its anticancer effects predominantly through specific interactions with β-tubulin, instigating cell cycle arrest and triggering various cell death pathways, including apoptosis, pyroptosis, ferroptosis, and necroptosis. The paper systematically delineates the chemical attributes and action mechanisms of paclitaxel and its analogs, underscoring their capacity to disrupt microtubule dynamics, thereby leading to mitotic arrest and subsequent cell death induction. It also scrutinizes the pivotal role of gap junctions, composed of connexin proteins, in the modulation of cancer cell behavior and chemoresistance, especially in the milieu of paclitaxel administration. The review articulates how gap junctions can either suppress tumors or contribute to cancer progression, thereby influencing chemotherapy outcomes. Furthermore, the paper provides an in-depth analysis of how paclitaxel modulates gap junction-associated kinases via phosphorylation, influencing the drug's therapeutic efficacy and resistance profiles. By integrating insights from numerous key studies, the review offers a comprehensive understanding of the interplay between paclitaxel, gap junctions, and kinases, shedding light on potential approaches to augment paclitaxel's anti-tumor effectiveness and counteract chemoresistance in cancer treatment.

Multi-omics analysis of expression profile and prognostic values of connexin family in LUAD

PURPOSE

Our study first explored the expression differences and prognostic significance of Cx genes in pan-cancer and then focused on LUAD. Our objectives were to conducted a comprehensive analysis of the expression profile, prognostic significance, genetic alterations, potential biological functions and drug sensitivity of the Connexin gene family in LUAD.

METHODS

We developed a comprehensive prognostic model for LUAD by combining risk scores with clinical features and created a nomogram to predict 1-, 3-, and 5-year overall survival. Using single-cell sequencing, we examined the expression and biological functions of the identified prognostic markers.

RESULTS

Our risk model revealed that GJB2-5 play a critical role in the prognosis of LUAD patients, associated with many biological processes such as cell cycle, DNA damage, EMT, hypoxia, invasion, and metastasis. Furthermore, the connexin gene family is linked to transcriptional mechanisms such as the extracellular matrix (ECM), migration, mobility, angiogenesis, and the epithelial-mesenchymal transition (EMT) genetic program.

CONCLUSION

The risk model can be used as a potential prognostic factor for LUAD patients and may provide new insights into cancer treatment from perspective of the expression of Cx genes.

Bioinformatics, RNA sequencing, and targeted bisulfite sequencing analyses identify the role of PROM2 as a diagnostic and prognostic biomarker

OBJECTIVES

Prominin 2 (PROM2) gene has been reported as a molecular biomarker of human cancers; however, its role is still controversial. This study was therefore arranged to seek the role of PROM2 in different cancers with Bioinformatics and in vitro analyses.

METHODS

A combination of bioinformatics and molecular experiments.

RESULTS

Through the utilization of Bioinformatics analysis, it was observed that in 19 out of the 24 human cancers studied, there was a significant increase in the expression of PROM2 compared to the respective control samples. Additionally, the overexpression of PROM2 was linked specifically to a decrease in overall survival (OS) among breast cancer (BRCA), lung adenocarcinoma (LUAD), and uterine corpus endometrial carcinoma (UCEC) patients. Furthermore, advanced molecular investigations were conducted, encompassing RNA sequencing (RNA-seq) as well as targeted bisulfite sequencing (bisulfite-seq) assessments of PROM2. These analyses were performed across an array of lung cancer cell lines (A549, ABC-1, EBC-1, and LK-2) and a normal control lung cell line (MRC-9). Results of these analysis revealed overexpression and reduced methylation of PROM2 within lung cancer cell lines, relative to the corresponding control cell line. This suggests that PROM2 assumes a substantial function in the advancement and course of BRCA, LUAD, and UCEC cancers. Subsequent pathway analysis revealed that genes enriched by PROM2 are actively engaged in four pivotal pathways. Additionally, intriguing associations were observed between PROM2 expression, tumor purity, infiltration of CD8+ T immune cells, and genetic modifications. Moreover, we also predicted a few MicroRNAs (miRNAs), transcription factors (TFs), and potential drugs that could help to understand and better manage these cancers via designing appropriate therapies targeting PROM2.

CONCLUSION

Via this study, we effectively revealed PROM2 overexpression as a potential diagnostic and prognostic biomarker of survival in BRCA, LUAD, and UCEC.

The roles of connexins and gap junctions in the progression of cancer

Gap junctions (GJs), which are composed of connexins (Cxs), provide channels for direct information exchange between cells. Cx expression has a strong spatial specificity; however, its influence on cell behavior and information exchange between cells cannot be ignored. A variety of factors in organisms can modulate Cxs and subsequently trigger a series of responses that have important effects on cellular behavior. The expression and function of Cxs and the number and function of GJs are in dynamic change. Cxs have been characterized as tumor suppressors in the past, but recent studies have highlighted the critical roles of Cxs and GJs in cancer pathogenesis. The complex mechanism underlying Cx and GJ involvement in cancer development is a major obstacle to the evolution of therapy targeting Cxs. In this paper, we review the post-translational modifications of Cxs, the interactions of Cxs with several chaperone proteins, and the effects of Cxs and GJs on cancer. Video Abstract.

GJB3 promotes pancreatic cancer liver metastasis by enhancing the polarization and survival of neutrophil

Connexins are membrane expressed proteins, which could assemble into hexamers to transfer metabolites and secondary messengers. However, its roles in pancreatic cancer metastasis remains unknown. In this study, by comparing the gene expression patterns in primary pancreatic cancer patients primary and liver metastasis specimens, we found that Gap Junction Protein Beta 3 (GJB3) significantly increased in Pancreatic ductal adenocarcinoma (PDAC) liver metastasis. Animal experiments verified that GJB3 depletion suppressed the hepatic metastasis of PDAC cancer cells. Further, GJB3 over expression increased the neutrophil infiltration. Mechanistic study revealed that GJB3 form channels between PDAC tumor cells and accumulated neutrophil, which transfer cyclic adenosine monophosphate (cAMP) from cancer to neutrophil cells, which supports the survival and polarization. Taken together, our data suggesting that GJB3 could act as a potential therapeutic target of PDAC liver metastasis.

GJB5 association with BRAF mutation and survival in cutaneous malignant melanoma

BACKGROUND

Gap junctional intercellular communication is crucial for epidermal cellular homeostasis. Inability to establish melanocyte-keratinocytes contacts and loss of intercellular junction's integrity may contribute to melanoma development. Connexins, laminins and desmocollins have been implicated in the control of melanoma growth, where their reduced expression has been reported in metastatic lesions.

OBJECTIVES

The aim of this study was to investigate Connexin 31.1 (GJB5) expression and identify any association with BRAF mutational status, melanoma patient prognosis and MAPK inhibitors (MAPKi) treatment.

MATERIAL AND METHODS

GJB5 expression was measured at RNA and protein level in melanoma clinical samples and established cell lines treated or not with BRAF and MEK inhibitors, as well as in cell lines which developed MAPK inhibitors resistance. Findings were further validated and confirmed by analysis of independent datasets.

RESULTS

Our analysis reveals significant downregulation of GJB5 expression in metastatic melanoma lesions compared to primary ones and in BRAF mutated versus BRAF wild-type melanomas. Likewise, GJB5 expression is significantly lower in BRAF^V600E compared with BRAF^WT cell lines and increases upon MAPKi treatment. MAPKi-resistant melanoma cells display a similar expression pattern compared to BRAF^WT cells, with increased GJB5 expression associated with morphological changes. Enhancement of BRAF^V600E expression in BRAF^WT melanoma cells significantly upregulates miR-335-5p expression with consequent downregulation of GJB5, one of its targets. Furthermore, overexpression of miR-335-5p in two BRAF^WT cell lines confirms specific GJB5 protein downregulation. RT-qPCR analysis also revealed upregulation of miR-335 in BRAF^V600E melanoma cells, which is significantly downregulated in cells resistant to MEK inhibitors. Our data were further validated using the TCGA-SKCM dataset, where BRAF mutations associate with increased miR-335 expression and inversely correlate with GJB5 expression. In clinical samples, GJB5 underexpression is also associated with patient overall worse survival, especially at early stages.

CONCLUSION

We identified a significant association between metastases / BRAF mutation and low GJB5 expression in melanoma. Our results identify a novel mechanism of Gap-junctional protein regulation, suggesting a prognostic role for GJB5 in cutaneous melanoma.

Differential Expression of BOC, SPOCK2, and GJD3 Is Associated with Brain Metastasis of ER-Negative Breast Cancers

Simple Summary

Brain metastasis is diagnosed in 30–50% of metastatic breast cancer patients with currently limited treatment strategies and usually short survival rates. In the present study, we aim to identify genes specifically associated with the development of brain metastasis in breast cancer. Therefore, we compared RNA expression profiles from two groups of patients with metastatic breast cancer, with and without brain involvement. Three genes BOC, SPOCK2, and GJD3 were overexpressed in the group of primary breast cancers which developed brain metastasis. Expression profiles were confirmed in an independent breast cancer cohort for both BOC and SPOCK2. In addition, differential overexpression of SPOCK2 and GJD3 mRNA levels were found to be associated with the development of brain metastasis in an external online database of 204 primary breast cancers. Verification of these genes as biomarkers for brain metastasis development in primary breast cancer is warranted.

Abstract

Background: Brain metastasis is considered one of the major causes of mortality in breast cancer patients. To invade the brain, tumor cells need to pass the blood-brain barrier by mechanisms that are partially understood. In primary ER-negative breast cancers that developed brain metastases, we found that some of the differentially expressed genes play roles in the T cell response. The present study aimed to identify genes involved in the formation of brain metastasis independently from the T cell response. Method: Previously profiled primary breast cancer samples were reanalyzed. Genes that were found to be differentially expressed were confirmed by RT-PCR and by immunohistochemistry using an independent cohort of samples. Results: BOC, SPOCK2, and GJD3 were overexpressed in the primary breast tumors that developed brain metastasis. BOC expression was successfully validated at the protein level. SPOCK2 was validated at both mRNA and protein levels. SPOCK2 and GJD3 mRNA overexpression were also found to be associated with cerebral metastasis in an external online database consisting of 204 primary breast cancers. Conclusion: The overexpression of BOC, SPOCK2, and GJD3 is associated with the invasion of breast cancer into the brain. Further studies to determine their specific function and potential value as brain metastasis biomarkers are required.

BMP4 and PHLDA1 are plausible drug-targetable candidate genes for KRAS G12A-, G12D-, and G12V-driven colorectal cancer

Despite the frequent detection of KRAS driver mutations in patients with colorectal cancer (CRC), no effective treatments that target mutant KRAS proteins have been introduced into clinical practice. In this study, we identified potential effector molecules, based on differences in gene expression between CRC patients carrying wild-type KRAS (n = 390) and those carrying KRAS mutations in codon 12 (n = 240). CRC patients with wild-type KRAS harboring mutations in HRAS, NRAS, PIK3CA, PIK3CD, PIK3CG, RALGDS, BRAF, or ARAF were excluded from the analysis. At least 11 promising candidate molecules showed greater than two-fold change between the KRAS G12 mutant and wild-type and had a Benjamini-Hochberg-adjusted P value of less than 1E-08, evidence of significantly differential expression between these two groups. Among these 11 genes examined in cell lines transfected with KRAS G12 mutants, BMP4, PHLDA1, and GJB5 showed significantly higher expression level in KRAS G12A, G12D, and G12V transfected cells than in the wild-type transfected cells. We expect that this study will lead to the development of novel treatments that target signaling molecules functioning with KRAS G12-driven CRC.

Connexins in Lung Cancer and Brain Metastasis

Connexins (Cxs) are involved in the brain metastasis of lung cancer cells. Thus, it is necessary to determine whether gap junction-forming Cxs are involved in the communication between lung cancer cells and the host cells, such as endothelial cells, forming the brain-blood-barrier, and cells in the central nervous system. Data from multiple studies support that Cxs function as tumor suppressors during lung cancer occurrence. However, recent evidence suggests that during metastasis to the brain, cancer cells establish communication with the host. This review discusses junctional or non-junctional hemichannel studies in lung cancer development and brain metastasis, highlighting important unanswered questions and controversies.

Insight into the Role and Regulation of Gap Junction Genes in Lung Cancer and Identification of Nuclear Cx43 as a Putative Biomarker of Poor Prognosis

Direct intercellular communication, mediated by gap junctions formed by the connexin transmembrane protein family, is frequently dysregulated in cancer. Connexins have been described as tumour suppressors, but emerging evidence suggests that they can also act as tumour promoters. This feature is connexin- and tissue-specific and may be mediated by complex signalling pathways through gap junctions or hemichannels or by completely junction-independent events. Lung cancer is the number one cancer in terms of mortality worldwide, and novel biomarkers and therapeutic targets are urgently needed. Our objective was to gain a better understanding of connexins in this setting. We used several in silico tools to analyse TCGA data in order to compare connexin mRNA expression between healthy lung tissue and lung tumours and correlated these results with gene methylation patterns. Using Kaplan-Meier plotter tools, we analysed a microarray dataset and an RNA-seq dataset of non-small cell lung tumours in order to correlate connexin expression with patient prognosis. We found that connexin mRNA expression is frequently either upregulated or downregulated in lung tumours. This correlated with both good and poor prognosis (overall survival) in a clear connexin isoform-dependent manner. These associations were strongly influenced by the histological subtype (adenocarcinoma versus squamous cell carcinoma). We present an overview of all connexins but particularly focus on four isoforms implicated in lung cancer: Cx26, Cx30.3, Cx32 and Cx43. We further analysed the protein expression and localization of Cx43 in a series of 73 human lung tumours. We identified a subset of tumours that exhibited a unique strong nuclear Cx43 expression pattern that predicted worse overall survival (p = 0.014). Upon sub-stratification, the prognostic value remained highly significant in the adenocarcinoma subtype (p = 0.002) but not in the squamous carcinoma subtype (p = 0.578). This finding highlights the importance of analysis of connexin expression at the protein level, particularly the subcellular localization. Elucidation of the underlying pathways regulating Cx43 localization may provide for novel therapeutic opportunities.

Connexin43 Suppresses Lung Cancer Stem Cells

Alterations in gap junctions and their protein components, connexins, have been associated with neoplastic transformation and drug resistance, and more recently have been shown to play important roles in cancer stem cells (CSCs). However, there is less knowledge of connexins and gap junctions in lung CSCs. To address this, Connexin43 (Cx43), the major human lung epithelial gap junction protein, was expressed ectopically in poorly expressing National Cancer Institute-125 (NCI-H125) metastatic human lung adenocarcinoma cells, and phenotypic characteristics of malignant cells and abundance of CSCs were evaluated. The ectopic expression of Cx43 resulted in the formation of functional gap junctions; a more epithelial morphology; reduced proliferation, invasion, colony formation, tumorsphere formation, pluripotency marker expression, and percentage of aldehyde dehydrogenase (ALDH)-positive cells; and increased cisplatin sensitivity. Similarly, in NCI-H522 (human lung adenocarcinoma) and NCI-H661 (human lung large cell carcinoma) cell lines, which express Cx43 and functional gap junctions endogenously, the Cx43 content was lower in tumorspheres and ALDH-positive cells than in bulk cells. These results demonstrate that Cx43 can reverse several neoplastic characteristics and reduce the abundance of human lung CSCs.

Emerging roles of gap junction proteins connexins in cancer metastasis, chemoresistance and clinical application

Connexin, a four-pass transmembrane protein, contributes to assembly of gap junctions among neighboring cells and thus facilitates gap junctional intercellular communication (GJIC). Traditionally, the roles of connexins were thought to mediate formation of hemichannels and GJIC assembly for transportation of ions and small molecules. Many studies have observed loss of GJIC, due to reduced expression or altered cytoplasmic localization of connexins, in primary tumor cells. Connexins are generally considered tumor-suppressive. However, recent studies of clinical samples suggested a different role of connexins in that expression levels and membrane localization of connexins, including Connexin 43 (Cx43, GJA1) and Connexin 26 (Cx26, GJB2), were found to be enhanced in metastatic lesions of cancer patients. Cx43- and Cx26-mediated GJIC was found to promote cancer cell migration and adhesion to the pulmonary endothelium. Regulatory circuits involved in the induction of connexins and their functional effects have also been reported in various types of cancer. Connexins expressed in stromal cells were correlated with metastasis and were implicated in regulating metastatic behaviors of cancer cells. Recent studies have revealed that connexins can contribute to cellular phenotypes via multiple ways, namely 1) GJIC, 2) C-terminal tail-mediated signaling, and 3) cell-cell adhesion during gap junction formation. Both expression levels and the subcellular localization could participate determining the functional roles of connexins in cancer. Compounds targeting connexins were thus tested as potential therapeutics intervening metastasis or chemoresistance. This review focuses on the recent findings in the correlation between the expression of connexins and patients’ prognosis, their roles in metastasis and chemoresistance, as well as the implications and concerns of using connexin-targeting drugs as anti-metastatic therapeutics. Overall, connexins may serve as biomarkers for cancer prognosis and as therapeutic targets for intervening metastasis and chemoresistance.

Down regulation of RNA binding motif, single-stranded interacting protein 3, along with up regulation of nuclear HIF1A correlates with poor prognosis in patients with gastric cancer

Frequent loss of multiple regions in short arm of chromosome 3 is found in various tumors including gastric cancer (GC). RNA binding motif, single-stranded interacting protein 3 (RBMS3) is a tumor suppressor gene located in this region and mediates cancer angiogenesis. However, the role of RBMS3 in GC remains unclear.

To evaluate whether RBMS3, together with HIF1A, another key regulator of angiogenesis, predicts GC prognosis, the levels of RBMS3 and HIF1A were first examined by quantitative PCR (qPCR) and western blot from 27 fresh frozen GC and paired normal gastric tissues and then tested by immunohistochemistry (IHC) from 191 GC and 46 normal controls. Moreover, uni- and multivariate analysis were employed to assess the correlations between their levels and microvessel density (MVD) and clinical prognosis. To further identify RBMS3 function in vitro, cell proliferation assay, clonogenic assay, flow cytometry analysis and endothelial cell tube formation assay were employed.

We found that RBMS3 level was decreased, whereas HIF1A was elevated in GC. Furthermore, we demonstrated that RBMS3 was an independent prognostic factor and the levels of RBMS3 and HIF1A were associated with GC angiogenesis and histopathological differentiation: patients with lower RBMS3 level and higher nuclear HIF1A expression had poorer prognosis. Besides, gain- and loss-of-function study revealed RBMS3 regulation on G1/S progression, cell proliferation and the tube formation of human umbilical vein endothelial cells (HUVECs) in vitro. These findings implicated that RBMS3 and nuclear HIF1A could act as prognostic biomarkers and therapeutic targets for GC.

Ginsenoside improves papillary thyroid cancer cell malignancies partially through upregulating connexin 31

Connexin 31 (Cx31) is considered a suppressor for many tumors. Ginsenoside (Rg1) is a traditional Chinese herb that is widely acknowledged due to its anti-tumor characteristics. However, limited studies have focused on the role of Rg1 in papillary thyroid cancer (PTC) cells. In the current study, we found that the expression of Cx31 in thyroid cancer tissues and thyroid cancer cell lines was significantly lower than that in normal thyroid epithelial tissues and cell lines. Overexpression of Cx31 reduced thyroid cancer cell proliferation, migration and invasion. Furthermore, we found that Rg1 significantly enhanced the expression of Cx31. Moreover, the proliferation and migration of IHH-4 and BCPAP cells were significantly reduced by Rg1 treatment. In contrast, the silencing of Cx31 enhanced the expression of Ki67 and proliferating cell nuclear antigen (PCNA). Meanwhile, treatment with Rg1 significantly decreased the protein levels of Ki67 and PCNA, but these effects could be abolished by transfection with si-Cx31. In summary, we provide novel evidence that the expression of Cx31 was decreased in thyroid cancer cells, but Rg1 treatment could significantly enhance the expression of Cx31 thereby suppressing thyroid cancer cell proliferation and migration.

CSF-1R regulates non-small cell lung cancer cells dissemination through Wnt3a signaling

Therapeutic antibodies targeting colony stimulating factor 1 receptor (CSF-1R) to block colony stimulating factor-1/colony stimulating factor 1 receptor (CSF-1/CSF-R) signaling axis have exhibit remarkable efficacy in the treatment of malignant tumor. Yet, little is known about the effects of intrinsic CSF-1R in human non-small-cell carcinoma (NSCLC). Here we demonstrated that NSCLC cell-intrinsic CSF-1R promoted cells growth and metastasis both in vitro and in vivo. CSF-1R knocked-down by transfecting with shRNA target CSF-1R suppressed NSCLC cells proliferation and tumor growth in nude mice. Conversely, ectopic expression of CSF-1R promoted cells proliferation and accelerated tumor growth. Mechanistically, the NSCLC CSF-1R modulated downstream effectors of phosphatidylinositol 3-kinase (PI3K) signaling. In addition, CSF-1R overexpression significantly enhanced NSCLC cells mobility, invasion and epithelial-mesenchymal transition (EMT) process, whereas silencing CSF-1R inhibits these phenotypes. Microarray analysis suggested that Wnt family member 3a (Wnt3a) function as a downstream factor of CSF-1R. On account of this, we future identified CSF-1R/Wnt3a a signaling pathway sustained NSCLC cells metastasis. Finally, in patients, CSF-1R and Wnt3a expression positively correlated with the of NSCLC patients. Our results identify NSCLC cell intrinsic functions of CSF-1R/Wnt3a axis in dissemination of NSCLC.

Influence of gap junction intercellular communication composed of connexin 43 on the antineoplastic effect of adriamycin in breast cancer cells

Gap junctions (GJs) serve the principal role in the antineoplastic (cytotoxicity and induced apoptosis) effect of chemical drugs. The aim of the present study was to determine the effect of GJ intercellular communication (GJIC) composed of connexin 43 (Cx43) on adriamycin cytotoxicity in breast cancer cells. Four cell lines (Hs578T, MCF-7, MDA-MB-231 and SK-BR-3) with different degree of malignancy were used in the study. The results of western blotting and immunofluorescence revealed that, in Hs578T and MCF-7 cells, which have a low degree of malignancy, the expression levels of Cx43 and GJIC were higher than those in MDA-MB-231 and SK-BR-3 cells (which have a high degree of malignancy). In Hs578T and MCF-7 cells, where GJ could be formed, the function of GJ was modulated by a pharmacological potentiators [retinoid acid (RA)]/inhibitors [oleamide and 18-α-glycyrrhetinic acid (18-α-GA)] and small interfering RNA (siRNA). In high-density cells (where GJ was formed), enhancement of GJ function by RA increased the cytotoxicity of adriamycin, while inhibition of GJ function by oleamide/18-α-GA and siRNA decreased the cytotoxicity caused by adriamycin. Notably, the modulation of GJ did not affect the survival of cells treated with adriamycin when cells were in low density (no GJ was formed). The present study illustrated the association between GJIC and the antitumor effect of adriamycin in breast cancer cells. The cytotoxicity of adriamycin on breast cancer cells was increased when the function of gap junctions was enhanced.

Microenvironmental Interaction Between Hypoxia and Endothelial Cells Controls the Migration Ability of Placenta-Derived Mesenchymal Stem Cells via α4 Integrin and Rho Signaling

Mesenchymal stem cells (MSCs) are a powerful source for cell therapy in degenerative diseases. The migration ability of MSCs is an important factor that enhances the therapeutic effect of the cells when they are transplanted into target tissues or organs. Hypoxia and the endothelial barrier, which are representative migration microenvironmental factors, are known to be regulated by the integrin-mediated pathway in several cancers. However, their regulatory mechanisms in MSCs remain unclear. Here, the objectives of the study were to compare the expression of markers related to integrin-mediated signaling in placenta-derived MSCs (PDMSCs) dependent on hypoxia and co-cultured with human umbilical vein endothelial cells (HUVECs) and to evaluate their correlations between migration ability and microenvironmetal factors including hypoxia and endothelial cells. The migration abilities of PDMSCs exposed to hypoxic conditions were significantly increased compared with normal fibroblasts (WI-38) and control (P < 0.05). Interestingly, decreased integrin α4 in PDMSCs under hypoxia induce to increase migration abilities of PDMSCs. Also, Rho family-related markers were significantly increased in PDMSCs under hypoxic conditions compared with normoxia (P < 0.05). Furthermore, the migration ability of PDMSCs was decreased by Rho kinase inhibitor treatment (Y-27632) and co-culturing with HUVECs in an ex vivo system. ROCK activity was increased by inhibiting integrin α4 with HUVECs and hypoxia compared with the absence of HUVECs and under normoxia. The findings suggest microenvironment event by hypoxia and the interaction with endothelial cells may be useful as a regulator of MSC migration and provide insight into the migratory mechanism of MSCs in stem cell-based therapy.

The Association Between VEGF +936C/T and -634G/C Polymorphisms and Breast Cancer Susceptibility, Tumor Growth, and Metastases: Evidence From 20,728 Subjects

The relation between the polymorphisms of vascular endothelial growth factor (VEGF) and breast cancer remains inconclusive. In our meta-analysis based on 10,340 breast cancer patients and 10,388 controls, we found breast cancer susceptibility was elevated in individuals carrying the VEGF +936C allele, especially in Asians, and the +936CC increases tumor growth. The G allele of -634G/C polymorphism reduces breast cancer susceptibility in Asians, and breast cancer patients of -634GG genotype has decreased tumor growth. These results suggest that both the VEGF +936C/T and -634G/C polymorphisms influence breast cancer susceptibility and tumor growth, instead of metastasis.

Brown D, Calaf GM, Castellino RC, Cohen-Solal KA, Colacci A, Cruickshanks N, Dent P, Di Fiore R, Forte S, Goldberg GS, Hamid RA, Krishnan H, Laird DW, Lasfar A, Marignani PA, Memeo L, Mondello C, Naus CC, Ponce-Cusi R, Raju J, Roy D, Roy R, P. Ryan E, Salem HK, Scovassi AI, Singh N, Vaccari M, Vento R, Vondráček J, Wade M, Woodrick J, Bisson WH. Mechanisms of environmental chemicals that enable the cancer hallmark of evasion of growth suppression

As part of the Halifax Project, this review brings attention to the potential effects of environmental chemicals on important molecular and cellular regulators of the cancer hallmark of evading growth suppression. Specifically, we review the mechanisms by which cancer cells escape the growth-inhibitory signals of p53, retinoblastoma protein, transforming growth factor-beta, gap junctions and contact inhibition. We discuss the effects of selected environmental chemicals on these mechanisms of growth inhibition and cross-reference the effects of these chemicals in other classical cancer hallmarks.

Telomerase abrogates aneuploidy-induced telomere replication stress, senescence and cell depletion

The causal role of aneuploidy in cancer initiation remains under debate since mutations of euploidy-controlling genes reduce cell fitness but aneuploidy strongly associates with human cancers. Telomerase activation allows immortal growth by stabilizing telomere length, but its role in aneuploidy survival has not been characterized. Here, we analyze the response of primary human cells and murine hematopoietic stem cells (HSCs) to aneuploidy induction and the role of telomeres and the telomerase in this process. The study shows that aneuploidy induces replication stress at telomeres leading to telomeric DNA damage and p53 activation. This results in p53/Rb-dependent, premature senescence of human fibroblast, and in the depletion of hematopoietic cells in telomerase-deficient mice. Endogenous telomerase expression in HSCs and enforced expression of telomerase in human fibroblasts are sufficient to abrogate aneuploidy-induced replication stress at telomeres and the consequent induction of premature senescence and hematopoietic cell depletion. Together, these results identify telomerase as an aneuploidy survival factor in mammalian cells based on its capacity to alleviate telomere replication stress in response to aneuploidy induction.

MiR-29a suppresses prostate cell proliferation and induces apoptosis via KDM5B protein regulation

Small regulatory RNAs, known as microRNAs, regulate gene expression at the post-transcriptional level; such as protein translation inhibition or mRNA degradation. Altered miRNA expressions have been implicated in various cancers. In present studies, it was demonstrated that microRNA-29a (miR-29a) expressions were significantly lower in prostate cancer (PCa) patient samples, but the role of microRNA-29s in PCa remains unclear. KDM5B was highly expressed in PCa cancer cells. Bioinformatics analysis revealed a conserved target site for miR-29a in the 3-untranslated region (UTR) of KDM5B. Gain-of-function studies using mature miR-29a were performed to investigate cell proliferation and apoptosis in two PCa cell lines (LNCaP and PC-3). We utilized gene expression analysis and in silico database analysis to identify miR-29a-mediated molecular pathways and targets. We showed that miR-29a significantly suppressed the activity of a lucifarice reporter containing KDM5B-3'UTR, which was not observed in cells transfected with mutated KDM5B-3'UTR. Gene expression data demonstrated that KDM5B expression was lower in noncancerous prostatic cell WPMY-1 than in the four PCa cell lines (LNCaP, 22RV1, PC-3 and DU145). Moreover, the enforced expression of miR-29a in PC-3 and LNCaP cells inhibited proliferation, and induced apoptosis by repressing the expression of KDM5B. This study revealed that the aberrant expression of miR-29a in PCa cells regulated KDM5B expression levels associated with tumor dissemination. These findings may be utilized in developing novel therapeutic tools for PCa.

Connexins: junctional and non-junctional modulators of proliferation

Mounting evidence indicates that dysregulation of gap junctions and their structural subunits-connexins-often occurs in, and sometimes causes, a variety of proliferative disorders, including cancer. Connexin-mediated regulation of cell proliferation is complex and may involve modulation of gap junction intercellular communication (GJIC), hemichannel signalling, or gap junction-independent paths. However, the exact mechanisms linking connexins to proliferation remain poorly defined and a number of contradictory studies report both pro- and anti-proliferative effects, effects that often depend on the cell or tissue type or the microenvironment. The present review covers junctional and non-junctional regulation of proliferation by connexins, with a particular emphasis on their association with cancer.

Connexin 31.1 degradation requires the Clathrin-mediated autophagy in NSCLC cell H1299

Connexins have relative short half-lives. Connexin 31.1 (Cx31.1) was newly reported to be down-regulated in non-small cell lung cancer cell lines, and displayed tumour-suppressive properties. However, no reports describing how a cell regulates Cx31.1 level were found. In this study, Cx31.1 was suggested to be degraded through both ubiquitin-proteasome system (UPS) and autophagy. Blockage of UPS with MG-132 increased Cx31.1 level, but could not inhibit the degradation of Cx31.1 completely. In H1299 cells stably expressing Cx31.1, Cx31.1 reduced when autophagy was induced through starvation or Brefeldin A treatment. Knockdown of autophagy-related protein ATG5 could increase the cellular level of Cx31.1 both under normal growth condition and starvation-induced autophagy. Colocalization of Cx31.1 and autophagy marker light chain 3 (LC3) was revealed by immunofluorescence analysis. Coimmunoprecipitation and immunofluorescence showed that Cx31.1 might interact with clathrin heavy chain which was newly reported to regulate autophagic lysosome reformation (ALR) and controls lysosome homoeostasis. When clathrin expression was knockdown by siRNA treatment, the level of Cx31.1 increased prominently both under normal growth condition and starvation-induced autophagy. Under starvation-induced autophagy, LC3-II levels were slightly accumulated with siCla. treatment compared to that of siNC, which could be ascribed to that clathrin knockdown impaired the late stage of autophagy, ALR. Taken together, we found autophagy contributed to Cx31.1 degradation, and clathrin might be involved in the autophagy of Cx31.1.

Connexins in colorectal cancer pathogenesis

The connexins constitute a family of integral membrane proteins that form channels between adjacent cells. These channels are assembled in plasma membrane domains known as gap junctions and enable cells to directly exchange ions and small molecules. Intercellular communication via gap junctions plays important roles in regulating cell growth and differentiation and in maintaining tissue homeostasis. This type of cell communication is often impaired during cancer development, and several members of the connexin protein family have been shown to act as tumor suppressors. Emerging evidence suggests that the connexin protein family has important roles in colorectal cancer development. In the normal colonic epithelial tissue, three connexin isoforms, connexin 26 (Cx26), Cx32 and Cx43, have been shown to be expressed at the protein level. Colorectal cancer development is associated with loss of connexin expression or relocalization of connexins from the plasma membrane to intracellular compartments. Downregulation of connexins in colorectal carcinomas at the transcriptional level involves cancer-specific promoter hypermethylation. Recent studies suggest that Cx43 may constrain growth of colon cancer cells by interfering with the Wnt/β-catenin pathway. There is also increasing evidence that the connexins may have potential as prognostic markers in colorectal cancer. This review discusses the role of connexins in colorectal cancer pathogenesis, as well as their potential as prognostic markers and targets in the prevention and treatment of the disease.

Identification of miR-133b and RB1CC1 as independent predictors for biochemical recurrence and potential therapeutic targets for prostate cancer

OBJECTIVE

We aimed to investigate the contribution of microRNA-133b (miR-133b) in prostate cancer cell proliferation, cell cycle, and apoptosis. We also examined expression of miR-133b in prostate cancer tissues, and evaluated the prognostic significance of miR-133b, as well as its target gene RB1CC1 in patients with prostate cancer after radical prostatectomy.

EXPERIMENTAL DESIGN

miR-133b mimics (miR-133bm) and anti-miR-133b were transfected into LNCaP and PC-3 cells. CCK-8 was used to look at cell proliferation, flow cytometric analysis was carried out to study cell cycle, and apoptosis was determined by caspase-3 activity. miR-133b expression was assessed by real-time reverse transcription PCR and in situ hybridization in prostatic cell lines and 178 prostate tissue samples, respectively. The protein level of RB1CC1 was examined by Western blot and immunohistochemistry in prostatic cell lines and prostate tissue samples, respectively.

RESULTS

Overexpression of miR-133b in LNCaP cells boosted cell proliferation and cell-cycle progression, but inhibited apoptosis; in contrast, miR-133bm promoted cell apoptosis, but suppressed cell proliferation and cell-cycle progression in PC-3 cells. In LNCaP cells, silencing of RB1CC1, a target of miR-133b, inhibited cell apoptosis, and promoted cell-cycle progression. Moreover, miR-133b expression was significantly inversely correlated with RB1CC1 expression in prostate cancer tissues. Multivariate Cox analysis indicated that miR-133b and RB1CC1 might be two independent prognostic factors of biochemical recurrence.

CONCLUSIONS

miR-133b might enhance tumor-promoting properties in less aggressive LNCaP cells, whereas this miR may act as a tumor suppressor in more aggressive PC-3 cells. miR-133b and RB1CC1 were independent prognostic indicators for prostate cancer.

Connexins, gap junctions and tissue invasion

Formation of metastases negatively impacts the survival prognosis of cancer patients. Globally, if the various steps involved in their formation are relatively well identified, the molecular mechanisms responsible for the emergence of invasive cancer cells are still incompletely resolved. Elucidating what are the mechanisms that allow cancer cells to evade from the tumor is a crucial point since it is the first step of the metastatic potential of a solid tumor. In order to be invasive, cancer cells have to undergo transformations such as down-regulation of cell-cell adhesions, modification of cell-matrix adhesions and acquisition of proteolytic properties. These transformations are accompanied by the capacity to "activate" stromal cells, which may favor the motility of the invasive cells through the extracellular matrix. Since modulation of gap junctional intercellular communication is known to be involved in cancer, we were interested to consider whether these different transformations necessary for the acquisition of invasive phenotype are related with gap junctions and their structural proteins, the connexins. In this review, emerging roles of connexins and gap junctions in the process of tissue invasion are proposed.

Gap junction and hemichannel-independent actions of connexins on cell and tissue functions--an update

Connexins, a family of transmembrane proteins, are components of both gap junction channels and hemichannels, which mediate the exchange of ions and small molecules between adjacent cells, and between the inside and outside of the cell, respectively. Substantial advancements have been made in the comprehension of the role of gap junctions and hemichannels in coordinating cellular events. In recent years, a plethora of studies demonstrate a role of connexin proteins in the regulation of tissue homeostasis that occurs independently of their channel activities. This is shown in the context of cell growth, adhesion, migration, apoptosis, and signaling. The major mechanisms of these channel-independent activities still remain to be discovered. In this review, we provide an updated overview on the current knowledge of gap junction- and hemichannel-independent functions of connexins, in particular, their effects on tumorigenesis, neurogenesis and disease development.

The association between TP53 Arg72Pro polymorphism and lung cancer susceptibility: evidence from 30,038 subjects

BACKGROUND

The TP53 codon 72 polymorphism has been associated with the individual susceptibility to lung cancer. However, the association remains uncertain and varies with ethnicity, smoking status, cancer histology, and stage.

METHODS

We performed a meta-analysis to evaluate the relationship between TP53 Arg72Pro polymorphism and lung cancer susceptibility basing on 15,647 lung cancer patients and 14,391 controls from 36 published literatures. We also performed stratified analysis in populations of different ethnicities, smoking statuses, lung cancer stages, and histological types.

RESULTS

The analysis showed a significantly increased lung cancer susceptibility among Pro allele carriers (P < 0.001, odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.1-1.19), especially for smokers (P < 0.001, OR = 1.29, 95% CI = 1.12-1.47). Stratified analysis indicated that Pro72 elevates lung cancer susceptibility in Asians, while it has no effect on lung cancer risk of Caucasians. Moreover, Pro carriers present an increased risk of developing squamous cell carcinoma and adenocarcinoma, instead of large cell carcinoma and small cell carcinoma. Interestingly, patients with the Pro allele seemed to be diagnosed with lung cancer at the early stages (stage I-II, P = 0.008, OR = 1.2, 95% CI = 1.05-1.37).

CONCLUSIONS

Our results suggest that the Pro allele acts as a risk factor for development of lung cancer, especially for smokers and Asians.