Zonula occludens-1 (ZO-1) redistribution is involved in the regulation of cell dissociation in pancreatic cancer cells

Sortilin regulates blood-brain barrier integrity

Brain homeostasis depends on the existence of the blood-brain barrier (BBB). Despite decades of research, the factors and signalling pathways for modulating and maintaining BBB integrity are not fully elucidated. Here, we characterise the expression and function of the multifunctional receptor, sortilin, in the cells of the BBB, in vivo and in vitro. We show that sortilin acts as an important regulatory protein of the BBB's tightness. In rats lacking sortilin, the BBB was leaky, which correlated well with relocated distribution of the localisation of zonula occludens-1, VE-cadherin and β-catenin junctional proteins. Furthermore, the absence of sortilin in brain endothelial cells resulted in decreased phosphorylation of Akt signalling protein and increased the level of phospho-ERK1/2. As a putative result of MAPK/ERK pathway activity, the junctions between the brain endothelial cells were disintegrated and the integrity of the BBB became compromised. The identified barrier differences between wild-type and Sort1-/- brain endothelial cells can pave the way for a better understanding of sortilin's role in the healthy and diseased BBB.

Expression of Tight Junction Proteins Is Altered in Bladder Cancer

Bladder cancer (BC) is one of the tumors which occur most frequently in urological system, but less is known about the expression of tight junction proteins and its clinical significance in BC. In this study, expression of claudin-4, zonula occludens-1 (ZO-1) and zonula occludens-1 nucleic acid-binding protein (ZONAB), in BC tissues, adjacent nontumor tissue (ANTT), and BC cell lines was examined by Western blotting, semiquantitative RT-PCR, and immunohistochemistry, and then, the clinical significance of these proteins was investigated. The mRNA and protein expression of ZONAB were significantly upregulated, while those of ZO-1 was significantly downregulated in some BC cell lines and tissues in comparison with nontumor urothelial cell lines and ANTT. High expression rate of ZO-1 and ZONAB had negative correlation in BC tissues and was also correlated with muscle-invasive lesions in BC tissues. In conclusion, the expression of tight junction proteins is significantly altered in BC and ZO-1, and ZONAB interaction might be involved in BC development.

Differential expression profiles of microRNAs in highly and weakly invasive/metastatic pancreatic cancer cells

Pancreatic cancer is the eighth-leading cause of cancer-associated mortality worldwide. To date, the cellular and molecular mechanisms associated with the invasion and metastasis of pancreatic cancer remain unclear. To examine these mechanisms, a microRNA (miRNA/miR) microarray with 1,965 genes was hybridized with labeled miRNA probes from invasive PC-1.0 and non-invasive PC-1 cells for molecular profiling analysis. In addition, reverse transcription quantitative-polymerase chain reaction (RT-qPCR) was utilized to validate the microarray results. Online miRNA target prediction algorithms online were used to predict the target genes of the differentially expressed miRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) term enrichment analysis were performed for the potential targets of the differentially expressed miRNAs. The results demonstrated that 54 miRNAs were differentially expressed, of which 33 were upregulated and 21 were downregulated in the PC-1.0 cell line compared with the PC-1 cell line. A total of 6 upregulated miRNAs (miR-31, -34a, -181a, -181b, -193a-3p, and -193b) and 4 downregulated miRNAs (miR-221, -222, -484, and -502-3p) were selected from these 54 miRNAs and validated by RT-qPCR. The differentially expressed miRNAs were further validated by RT-qPCR in the human pancreatic cancer cell lines AsPC-1 (highly invasive) and CAPAN-2 (less invasive). The results revealed that 2 upregulated miRNAs (miR-34a and -193a-3p) and 4 downregulated miRNAs (miR-221, -222, -484, and -502-3p) exhibited a consistent expression pattern between the PC-1.0/PC-1 and AsPC-1/CAPAN-2 pancreatic cancer cells. The GO and KEGG enrichment analysis indicated that the mRNAs potentially targeted by miRNAs were involved in a range of biological functions. These results suggest that different miRNA expression profiles occur between highly and weakly invasive and metastatic pancreatic cancer cell lines, and may affect a variety of biological functions in pancreatic cancer.

Early Activation of MAPK p44/42 Is Partially Involved in DON-Induced Disruption of the Intestinal Barrier Function and Tight Junction Network

Deoxynivalenol (DON), produced by the plant pathogens Fusarium graminearum and Fusarium culmorum, is one of the most common mycotoxins, contaminating cereal and cereal-derived products. Although worldwide contamination of food and feed poses health threats to humans and animals, pigs are particularly susceptible to this mycotoxin. DON derivatives, such as deepoxy-deoxynivalenol (DOM-1), are produced by bacterial transformation of certain intestinal bacteria, which are naturally occurring or applied as feed additives. Intestinal epithelial cells are the initial barrier against these food- and feed-borne toxins. The present study confirms DON-induced activation of MAPK p44/42 and inhibition of p44/42 by MAPK-inhibitor U0126 monoethanolate. Influence of DON and DOM-1 on transepithelial electrical resistance (TEER), viability and expression of seven tight junction proteins (TJ), as well as the potential of U0126 to counteract DON-induced effects, was assessed. While DOM-1 showed no effect, DON significantly reduced TEER of differentiated IPEC-J2 and decreased expression of claudin-1 and -3, while leaving claudin-4; ZO-1, -2, and -3 and occludin unaffected. Inhibition of p44/42 counteracted DON-induced TEER decrease and restored claudin-3, but not claudin-1 expression. Therefore, effects of DON on TEER and claudin-3 are at least partially p44/42 mediated, while effects on viability and claudin-1 are likely mediated via alternative pathways.

Oxysterol binding protein-related protein-5 is related to invasion and poor prognosis in pancreatic cancer

In previous studies, the gene expression profiles of two hamster pancreatic cancer cells with different potentials for invasion and metastasis were analyzed. In the present study, we identified that one of the genes expressed strongly in the highly metastatic cell line is hamster oxysterol binding protein-related protein (ORP)-5. The aim of the present study was to clarify the relationship between ORP5 and invasion and poor prognosis of human pancreatic cancer. Invasion assays were carried out in both hamster and human pancreatic cancer cells by suppressing the ORP5 gene with short interfering RNA or inducing its expression by introducing an expression vector. To evaluate the relationship between ORP5 and the characteristics of human pancreatic cancer, 56 pancreatic cancer tissue specimens were analyzed and the ORP5 expression in each pancreatic cancer tissue specimen was analyzed by immunohistochemistry. In both the hamster and human pancreatic cancer cells, suppression of ORP5 significantly reduced the invasion rate of the cells and induction of ORP5 significantly enhanced the invasion rate of the cells. In the clinical sample, the median survival times of the patients with ORP5-positive (n = 33) and ORP5-negative (n = 23) cancer were 8.3 and 17.2 months, respectively (P = 0.02). Also, the 1-year survival rates of patients with ORP5-positive and ORP5-negative cancer were 36.4 and 73.9%, respectively (P = 0.005). The ORP5 expression level was related to both invasion and poor prognosis in human pancreatic cancer. These findings suggest that the expression of ORP5 may induce cancer cell invasion, resulting in the poor prognosis of pancreatic cancer.

Crosstalk of tight junction components with signaling pathways

Tight junctions (TJs) regulate the passage of ions and molecules through the paracellular pathway in epithelial and endothelial cells. TJs are highly dynamic structures whose degree of sealing varies according to external stimuli, physiological and pathological conditions. In this review we analyze how the crosstalk of protein kinase C, protein kinase A, myosin light chain kinase, mitogen-activated protein kinases, phosphoinositide 3-kinase and Rho signaling pathways is involved in TJ regulation triggered by diverse stimuli. We also report how the phosphorylation of the main TJ components, claudins, occludin and ZO proteins, impacts epithelial and endothelial cell function.

Role of tight junctions in cell proliferation and cancer

The acquisition of a cancerous phenotype by epithelial cells involves the disruption of intercellular adhesions. The reorganization of the E-cadherin/beta-catenin complex in adherens junctions during cell transformation is widely recognized. Instead the implication of tight junctions (TJs) in this process is starting to be unraveled. The aim of this article is to review the role of TJ proteins in cell proliferation and cancer.