Twist: a new player in the epithelial-mesenchymal transition of the peritoneal mesothelial cells

Autophagy inhibition mediated by MCOLN1/TRPML1 suppresses cancer metastasis via regulating a ROS-driven TP53/p53 pathway

Compelling evidence has demonstrated that macroautophagy/autophagy plays an important role in regulating multiple steps of metastatic cascades; however, the precise role of autophagy in metastasis remains unclear. This study demonstrates that autophagy inhibition induced by MCOLN1/TRPML1 suppresses cancer metastasis by evoking the ROS-mediated TP53/p53 pathway. First, we found that MCOLN1-mediated autophagy inhibition not only profoundly inhibits both migration and invasion in malignant melanoma and glioma cell lines in vitro, but also suppresses melanoma metastasis in vivo. Second, our study reveals that autophagy inhibition induced by MCOLN1 leads to damaged mitochondria accumulation followed by large quantities of ROS release. Third, we demonstrate that the elevated ROS resulting from autophagy inhibition subsequently triggers TP53 activity, which in turn modulates expression of its downstream targets which are involved in a broad spectrum of the metastatic cascade to suppress metastasis including MMP members and TWIST. In summary, our findings have established a mechanism by which autophagy inhibition suppresses metastasis via the ROS-TP53 signaling pathway. More importantly, our study demonstrates that autophagy inhibition through stimulation of MCOLN1 could evidently be one of the therapeutic potentials for combating cancer metastasis.Abbreviations: 3-MA: 3-methyladenine; AA: amino acid; ATG5: autophagy related 5; ATG12: autophagy related 12; Baf-A1: bafilomycin A₁; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CQ: chloroquine; DMEM: Dulbecco's Modified Eagle Medium; EMT: epithelial-mesenchymal transition; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HEK: human embryonic kidney; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCOLN1/TRPML1: mucolipin TRP cation channel 1; MMP: matrix metallopeptidase; NC: negative control; NRK: normal rat kidney; PBS: phosphate-buffered saline; shRNA: short hairpin RNA; siRNA: short interfering RNA; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1.

EMT: Mechanisms and therapeutic implications

Metastasis, the dissemination of cancer cells from primary tumors, represents a major hurdle in the treatment of cancer. The epithelial-mesenchymal transition (EMT) has been studied in normal mammalian development for decades, and it has been proposed as a critical mechanism during cancer progression and metastasis. EMT is tightly regulated by several internal and external cues that orchestrate the shifting from an epithelial-like phenotype into a mesenchymal phenotype, relying on a delicate balance between these two stages to promote metastatic development. EMT is thought to be induced in a subset of metastatic cancer stem cells (MCSCs), bestowing this population with the ability to spread throughout the body and contributing to therapy resistance. The EMT pathway is of increasing interest as a novel therapeutic avenue in the treatment of cancer, and could be targeted to prevent tumor cell dissemination in early stage patients or to eradicate existing metastatic cells in advanced stages. In this review, we describe the sequence of events and defining mechanisms that take place during EMT, and how these interactions drive cancer cell progression into metastasis. We summarize clinical interventions focused on targeting various aspects of EMT and their contribution to preventing cancer dissemination.

Senescence-Associated MicroRNAs

Senescent cells arise as a consequence of cellular damage and can have either a detrimental or advantageous impact on tissues and organs depending on the specific cell type and metabolic state. As senescent cells accumulate in tissues with advancing age, they have been implicated in many age-related declines and diseases. The major facets of senescence include two pathways responsible for establishing and maintaining a senescence program, p53/CDKN1A(p21) and CDKN2A(p16)/RB, as well as the senescence-associated secretory phenotype. Numerous MicroRNAs influence senescence by modulating the abundance of key senescence regulatory proteins, generally by lowering the stability and/or translation of mRNAs that encode such factors. Accordingly, understanding the molecular mechanisms by which MicroRNAs influence senescence will enable diagnostic and therapeutic opportunities directed at senescent cells. Here, we review senescence-associated (SA)-MicroRNAs and discuss their implications in senescence-relevant pathologies.

Differential expression pattern of Twist1 in mouse preimplantation embryos suggests its multiple roles during early development

PURPOSE

The purpose of the present study is to understand Twist-related protein 1 (Twist1) spatiotemporal expression patterns and functions during early embryo development.

METHODS

We performed whole-mount double immunofluorescence staining and reverse transcription (RT)-PCR analysis of the Twist1 protein and gene throughout the preimplantation development in mice.

RESULTS

We determined that after compaction, the expression of Twist1 becomes developmentally differentiated and targeted in the inner cells of embryos. In blastocysts at E4.5, uniform staining of the inner cell mass was apparent, and it had been gradually translocated to the nucleus of hatched embryonic cells at E4.75. Furthermore, the effect of potential regulators of Twist on its expression level during blastocyst development was also sought. Accordingly, Twist1 expression appeared to be upregulated in both mRNA and protein level following culture of embryos in the presence of high glucose.

CONCLUSIONS

Our study revealed the dynamic Twist localization within the early stage of embryo. The results are discussed in terms of potential roles of Twist1 in the processes of lineage segregation, hatching, and implantation in post-compaction embryos and in blastocysts.

Animal Models of Peritoneal Dialysis: Thirty Years of Our Own Experience

Experimental animal models improve our understanding of technical problems in peritoneal dialysis PD, and such studies contribute to solving crucial clinical problems. We established an acute and chronic PD model in nonuremic and uremic rats. We observed that kinetics of PD in rats change as the animals are aging, and this effect is due not only to an increasing peritoneal surface area, but also to changes in the permeability of the peritoneum. Changes of the peritoneal permeability seen during chronic PD in rats are comparable to results obtained in humans treated with PD. Effluent dialysate can be drained repeatedly to measure concentration of various bioactive molecules and to correlate the results with the peritoneal permeability. Additionally we can study in in vitro conditions properties of the effluent dialysate on cultured peritoneal mesothelial cells or fibroblasts. We can evaluate acute and chronic effect of various additives to the dialysis fluid on function and permeability of the peritoneum. Results from such study are even more relevant to the clinical scenario when experiments are performed in uremic rats. Our experimental animal PD model not only helps to understand the pathophysiology of PD but also can be used for testing biocompatibility of new PD fluids.

A cross sectional study of p504s, CD133, and Twist expression in the esophageal metaplasia dysplasia adenocarcinoma sequence

The incidence of esophageal adenocarcinoma has increased dramatically over recent years and Barrett's esophagus is considered the most established risk factor for its development. Endoscopic surveillance of Barrett's esophagus is therefore recommended but hinges on histological interpretation of randomly taken biopsies which is poorly reproducible. The use of biomarkers presents an opportunity to improve our ability to risk-stratify these patients.We examined three biomarkers namely p504s, CD133, and Twist in the setting of Barrett's esophagus, low-grade dysplasia, and esophageal adenocarcinoma to evaluate differential expression between benign, dysplastic, and malignant Barrett's tissue in an exploratory cross-sectional study. Twenty-five cases each of Barrett's esophagus, low-grade dysplasia, and esophageal adenocarcinoma were included along-with 25 cases of esophagectomy resections for Barrett's adenocarcinoma. The biomarkers were immunostained on automated Ventana(®) immunostainer. The biopsies were assessed for biomarker expression by two independent observers. Granular cytoplasmic staining of p504s was observed in dysplastic Barrett's biopsies and esophageal adenocarcinoma but not in Barrett's esophagus. Apical and membranous CD133 expression was also observed in dysplastic Barrett's and esophageal adenocarcinoma. Nuclear Twist expression was seen predominantly in stromal cells. There was increased p504s expression in dysplastic Barrett's esophagus and esophageal adenocarcinoma compared with controls. CD133 expression was detected for the first time in esophageal adenocarcinoma and dysplastic Barrett's esophagus. Twist expression was not convincing enough to be labeled as Barrett's biomarker. p504s and CD133 have the potential to differentiate benign from malignant Barrett's tissue in this exploratory study. Their validity should be established in prospective longitudinal studies.

Gelatinase B/MMP-9 in Tumour Pathogenesis and Progression

Since its original identification as a leukocyte gelatinase/type V collagenase and tumour type IV collagenase, gelatinase B/matrix metalloproteinase (MMP)-9 is now recognised as playing a central role in many aspects of tumour progression. In this review, we relate current concepts concerning the many ways in which gelatinase B/MMP-9 influences tumour biology. Following a brief outline of the gelatinase B/MMP-9 gene and protein, we analyse the role(s) of gelatinase B/MMP-9 in different phases of the tumorigenic process, and compare the importance of gelatinase B/MMP-9 source in the carcinogenic process. What becomes apparent is the importance of inflammatory cell-derived gelatinase B/MMP-9 in tumour promotion, early progression and triggering of the "angiogenic switch", the integral relationship between inflammatory, stromal and tumour components with respect to gelatinase B/MMP-9 production and activation, and the fundamental role for gelatinase B/MMP-9 in the formation and maintenance of tumour stem cell and metastatic niches. It is also apparent that gelatinase B/MMP-9 plays important tumour suppressing functions, producing endogenous angiogenesis inhibitors, promoting inflammatory anti-tumour activity, and inducing apoptosis. The fundamental roles of gelatinase B/MMP-9 in cancer biology underpins the need for specific therapeutic inhibitors of gelatinase B/MMP-9 function, the use of which must take into account and substitute for tumour-suppressing gelatinase B/MMP-9 activity and also limit inhibition of physiological gelatinase B/MMP-9 function.

Paracrine effects of transplanted mesothelial cells isolated from temperature-sensitive SV40 large T-antigen gene transgenic rats during peritoneal repair

BACKGROUND

The prevention and restoration of peritoneal damage is a critical mission in peritoneal dialysis (PD). Transplantation of mesothelial cells has been suggested to suppress peritoneal injury during PD. Few studies have examined the efficacy and safety of cell transplantation. We evaluated the paracrine effects of mesothelial transplantation during peritoneal repair using immortalized temperature-sensitive mesothelial cells (TSMCs) in chlorhexidine gluconate (CG)-induced peritoneal fibrosis rats.

METHODS

Continuous-infusion pumps containing 8% CG were placed into the abdominal cavity for 21 days. After the removal of the pumps, the TSMCs were injected into the peritoneal cavity at Day 22 (Tx-1 group) or 29 (Tx-2 group). Morphological findings and mRNA expressions of regeneration-related factors were examined at Days 22, 29 and 35.

RESULTS

Peritoneal thickness was aggravated in the Tx-1 group. Levels of transforming growth factor (TGF)-β, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-2 mRNA in the Tx-1 group at Day 35 were comparable with those at Day 22. The levels of Snail, B-Raf and ERK-1, markers of epithelial to mesenchymal transition and of the RAS/MAPK pathway in the Tx-1 group, were significantly higher than those in the Tx-2 group. TGF-β and VEGF were produced from the transplanted mesothelial cells and the surrounding cells in the Tx-1 group.

CONCLUSION

It appears that the paracrine effect of transplanted mesothelial cells during peritoneal repair is associated with its surrounding condition. It is important to determine the most appropriate time for developing peritoneal repair through mesothelial transplantation.

Transcriptional patterns in peritoneal tissue of encapsulating peritoneal sclerosis, a complication of chronic peritoneal dialysis

Encapsulating peritoneal sclerosis (EPS) is a devastating complication of peritoneal dialysis (PD), characterized by marked inflammation and severe fibrosis of the peritoneum, and associated with high morbidity and mortality. EPS can occur years after termination of PD and, in severe cases, leads to intestinal obstruction and ileus requiring surgical intervention. Despite ongoing research, the pathogenesis of EPS remains unclear. We performed a global transcriptome analysis of peritoneal tissue specimens from EPS patients, PD patients without EPS, and uremic patients without history of PD or EPS (Uremic). Unsupervised and supervised bioinformatics analysis revealed distinct transcriptional patterns that discriminated these three clinical groups. The analysis identified a signature of 219 genes expressed differentially in EPS as compared to PD and Uremic groups. Canonical pathway analysis of differentially expressed genes showed enrichment in several pathways, including antigen presentation, dendritic cell maturation, B cell development, chemokine signaling and humoral and cellular immunity (P value<0.05). Further interactive network analysis depicted effects of EPS-associated genes on networks linked to inflammation, immunological response, and cell proliferation. Gene expression changes were confirmed by qRT-PCR for a subset of the differentially expressed genes. EPS patient tissues exhibited elevated expression of genes encoding sulfatase1, thrombospondin 1, fibronectin 1 and alpha smooth muscle actin, among many others, while in EPS and PD tissues mRNAs encoding leptin and retinol-binding protein 4 were markedly down-regulated, compared to Uremic group patients. Immunolocalization of Collagen 1 alpha 1 revealed that Col1a1 protein was predominantly expressed in the submesothelial compact zone of EPS patient peritoneal samples, whereas PD patient peritoneal samples exhibited homogenous Col1a1 staining throughout the tissue samples. The results are compatible with the hypothesis that encapsulating peritoneal sclerosis is a distinct pathological process from the simple peritoneal fibrosis that accompanies all PD treatment.