The claudin family of proteins in human malignancy: a clinical perspective

The role of CLDN18.2 in gastric cancer prognosis: a systematic review and meta-analysis

BACKGROUND

Gastric cancer (GC) is a major global cause of cancer mortality, with a median overall survival of just 12 months. CLDN18.2, a specific isoform of Claudin18 normally expressed in the gastric mucosa, has emerged as a potential therapeutic target and prognostic biomarker due to its exposure on the surface of tumor cells following malignant transformation. This exposure allows CLDN18.2's extracellular loops to bind monoclonal antibodies, presenting new opportunities for targeted therapy and improved prognostic assessment.

METHODS

A comprehensive search of PubMed, EMBASE, Cochrane Library, and Web of Science databases was conducted for studies that addressed the correlation of CLDN18.2 with: (1) Progression-free survival (PFS) and (2) Overall Survival (OS). Hazard ratio (HR) and odds ratio (OR) with 95% confidence intervals (CIs) were calculated using a fixed-effects model. Heterogeneity was examined with I2 statistics. P values of ≤ 0.05 were considered statistically significant. Statistical analyses were performed using RStudio, version 4.2.3.

RESULTS

A total of 15 studies encompassing a total of 4,085 patients were included. There were 2,691 (65.8%) male and 1,394 (34.2%) female patients. In the histologic GC analysis, there were 1,582 (38.7%) patients that had intestinal type and 1,280 (31.3%) with diffuse type. Patients with CLDN18.2 negative status exhibited a non-significant trend towards prolonged PFS (HR: 1.25; 95% CI: 0.98-1.61; p = 0.07; I2 = 18%) and a significant prolonged OS (HR: 1.20; 95% CI: 1.07-1.34; p < 0.01; I2 = 37%) when compared to CLDN18.2-positive patients.

CONCLUSION

Our findings establish CLDN18.2 as a robust negative prognostic indicator for overall survival in GC patients. While its impact on PFS was not statistically significant, the association with OS suggests CLDN18.2 may serve as a marker for complex biological processes underlying tumor advancement.

Claudins: from gatekeepers of epithelial integrity to potential targets in hepato-pancreato-biliary cancers

Claudins, a family of tetraspan transmembrane proteins, are critical to the integrity of tight junctions in epithelia and endothelia, influencing cellular processes such as development, differentiation, and apoptosis. Abnormal claudin expression is associated with various malignancies, particularly affecting tissue architecture and potentially facilitating tumor invasion and metastasis. In this comprehensive review, we explore the multifaceted functions of claudins: their expression, specific roles in cancer with a focus on hepato-pancreato-biliary malignancies and highlight their potential as therapeutic targets. We discuss current claudin-targeted therapies, including monoclonal antibodies, antibody-drug conjugates, bispecific T-cell engager and chimeric antigen receptor T-cell therapies. These approaches show promise in pre-clinical and clinical studies, particularly in hepato-pancreato-biliary cancers with large unmet needs. Despite these early signs of efficacy, challenges remain in effectively targeting these proteins due to their structural resemblance and overlapping functions.

Expression and Targeted Application of Claudins Family in Hepatobiliary and Pancreatic Diseases

Hepatobiliary and pancreatic diseases are becoming increasingly common worldwide and associated cancers are prone to recurrence and metastasis. For a more accurate treatment, new therapeutic strategies are urgently needed. The claudins (CLDN) family comprises a class of membrane proteins that are the main components of tight junctions, and are essential for forming intercellular barriers and maintaining cellular polarity. In mammals, the claudin family contains at least 27 transmembrane proteins and plays a major role in mediating cell adhesion and paracellular permeability. Multiple claudin proteins are altered in various cancers, including gastric cancer (GC), esophageal cancer (EC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), colorectal cancer (CRC) and breast cancer (BC). An increasing number of studies have shown that claudins are closely associated with the occurrence and development of hepatobiliary and pancreatic diseases. Interestingly, claudin proteins exhibit different effects on cancer progression in different tumor tissues, including tumor suppression and promotion. In addition, various claudin proteins are currently being studied as potential diagnostic and therapeutic targets, including claudin-3, claudin-4, claudin-18.2, etc. In this article, the functional phenotype, molecular mechanism, and targeted application of the claudin family in hepatobiliary and pancreatic diseases are reviewed, with an emphasis on claudin-1, claudin-4, claudin-7 and claudin-18.2, and the current situation and future prospects are proposed.

Progress of Clinical Studies Targeting Claudin18.2 for the Treatment of Gastric Cancer

Claudin18.2 is a tight junction protein, highly selective, generally expressed only in normal gastric mucosal epithelial cells, which can effectively maintain the polarity of epithelial and endothelial cells, thus effectively regulating the permeability and conductance of the paracellular pathway. Abnormal expression of Claudin18.2 can occur in various primary malignant tumors, especially gastrointestinal tumors, and even in metastatic foci. It regulates its expression by activating the aPKC/MAPK/AP-1 pathway, and therefore, the Claudin18.2 protein is a pan-cancer target expressed in primary and metastatic lesions in human cancer types. Zolbetuximab (IMAB362), an antibody specific for Claudin18.2, has been successfully tested in a phase III clinical trial, and the results of the study showed that combining Zolbetuximab with chemotherapy notably extends patients' survival and is expected to be a potential first-line treatment for patients with Claudin18.2(+)/HER-2(-) gastric cancer. Here, we systematically describe the biological properties and oncogenic effects of Claudin18.2, centering on its clinical-pathological aspects and the progress of drug studies in gastric cancer, which can help to further explore its clinical value.

Claudin 18.2 expression in digestive neuroendocrine neoplasms: a clinicopathological study

BACKGROUND

Claudin 18.2-targeted therapy has shown significant efficacy in treating claudin 18.2-positive cancers. However, limited systematic studies have investigated characteristics of claudin 18.2 expression in neuroendocrine neoplasms (NENs).

METHODS

Data and specimens from 403 cases of digestive NENs were retrospectively collected, and claudin 18.2 expression was detected using immunochemical staining.

RESULTS

Claudin 18.2 was positive in 19.6% (79/403) of the digestive NENs. The highest positive rate of claudin 18.2 was observed in gastric NENs (72/259, 27.8%), accounting for 91.1% (72/79) of all positive cases. The positivity rate was significantly higher in gastric NENs compared to pancreatic (2/78, 2.6%) or colorectal NENs (2/38, 5.3%; p < 0.05). For digestive NENs, claudin 18.2 positivity was significantly higher in neuroendocrine carcinomas (NECs) (37/144, 25.7%) than in neuroendocrine tumours (NETs; 14/160, 8.8%; p < 0.001), but no significant difference was found between gastric NECs (59/213, 27.7%) and gastric NETs (13/46, 28.3%; p > 0.05). The positivity was significantly higher in large-cell NECs (LCNECs; 28/79, 35.4%) and MiNEN (mixed neuroendocrine-non- neuroendocrine neoplasms)-LCNECs (23/66, 34.8%) compared to small-cell NECs (SCNECs; 9/65, 13.8%) and MiNEN-SCNECs (5/33, 15.2%; p < 0.05). Claudin 18.2 expression was more prevalent in gastric NENs than in pancreatic (12.5 ×; p = 0.001) and colorectal NENs (5.9 ×; p = 0.021). Claudin 18.2 staining was a useful method for identify the gastric origins of NETs, with a sensitivity of 28.3% and a specificity of 99.1%.

CONCLUSION

The expression characteristics of claudin 18.2 in NENs were characterized, which may provide a clinicopathological reference for targeted therapies in patients with NENs.

Efficacy and safety of Zolbetuximab plus chemotherapy for advanced CLDN18.2-positive gastric or gastro-oesophageal adenocarcinoma: a meta-analysis of randomized clinical trials

BACKGROUND

The benefit of adding Zolbetuximab to the treatment in patients with Claudin-18 isoform 2 (CLDN18.2)-positive, human epidermal growth factor receptor 2-negative, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma (GC/GEJ) is not yet fully elucidated.

METHODS

We searched PubMed, Embase and Cochrane databases for randomized controlled trials (RCTs) that investigated Zolbetuximab plus chemotherapy versus chemotherapy alone for GC or GEJ adenocarcinoma. We computed hazard-ratios (HRs) or odds-ratios (ORs) for binary endpoints, with 95% confidence intervals (CIs).

RESULTS

Three studies and 1,233 patients were included. Comparing with Zolbetuximab plus chemotherapy versus chemotherapy alone, progression-free survival (PFS) rate (HR 0.64; 95% CI 0.49-0.84; p < 0.01) and overall survival (OS) rate (HR 0.72; 95% CI 0.62-0.83; p < 0.01) were significant in favor of the Zolbetuximab group. Regarding effectiveness, the Objective Response Rate (ORR) was (OR 1.15; 95% CI 0.87-1.53; p = 0.34).

CONCLUSIONS

In this comprehensive systematic review and meta-analysis of RCTs, the incorporation of Zolbetuximab alongside chemotherapy offers a promising prospect for reshaping the established treatment paradigms for patients diagnosed with advanced CLDN18.2-positive GC/GEJ cancer.

Integrating scRNA-seq and bulk RNA-seq to characterize infiltrating cells in the colorectal cancer tumor microenvironment and construct molecular risk models

Colorectal cancer (CRC) is a malignancy that is both highly lethal and heterogeneous. Although the correlation between intra-tumoral genetic and functional heterogeneity and cancer clinical prognosis is well-established, the underlying mechanism in CRC remains inadequately understood. Utilizing scRNA-seq data from GEO database, we re-isolated distinct subsets of cells, constructed a CRC tumor-related cell differentiation trajectory, and conducted cell-cell communication analysis to investigate potential interactions across cell clusters. A prognostic model was built by integrating scRNA-seq results with TCGA bulk RNA-seq data through univariate, LASSO, and multivariate Cox regression analyses. Eleven distinct cell types were identified, with Epithelial cells, Fibroblasts, and Mast cells exhibiting significant differences between CRC and healthy controls. T cells were observed to engage in extensive interactions with other cell types. Utilizing the 741 signature genes, prognostic risk score model was constructed. Patients with high-risk scores exhibited a significant correlation with unfavorable survival outcomes, high-stage tumors, metastasis, and low responsiveness to chemotherapy. The model demonstrated a strong predictive performance across five validation cohorts. Our investigation involved an analysis of the cellular composition and interactions of infiltrates within the microenvironment, and we developed a prognostic model. This model provides valuable insights into the prognosis and therapeutic evaluation of CRC.

A novel tumor microenvironment-related gene signature with immune features for prognosis of lung squamous cell carcinoma

PURPOSE

Lung squamous cell carcinoma (LUSC) is an aggressive subset of non-small-cell lung cancer (NSCLC). The tumor microenvironment (TME) plays an important role in the development of LUSC. We aim to identify potential therapeutic targets and a TME-related prognostic signature and for LUSC.

METHODS

TME-related genes were obtained from TCGA-LUSC dataset. LUSC samples were clustered by the non-negative matrix clustering algorithm (NMF). The prognostic signature was constructed through univariate Cox regression, multivariate Cox regression, and the least absolute shrinkage and selection operator (LASSO) analyses. Gene set enrichment analysis (GSEA) was carried out to explore the enrichment pathways.

RESULTS

This study constructed a prognostic signature which contained 12 genes: HHIPL2, PLK4, SLC6A4, LSM1, TSLP, P4HA1, AMH, CLDN5, NRTN, CDH2, PTGIS, and STX1A. Patients were classified into high-risk and low-risk groups according to the median risk score of this signature. Compared with low-risk group patients, patients in high-risk group patients had poorer overall survival, which demonstrated this signature was an independent prognostic factor. Besides, correlation analysis and GSEA results revealed that genes of this signature were correlated with immune cells and drug response.

CONCLUSION

Our novel signature based on 12 TME-related genes might be applied as an independent prognostic indicator. Importantly, the signature could be a promising biomarker and accurately predict the prognosis of LUSC patients.

Research progress of Claudin-low breast cancer

Claudin-low breast cancer (CLBC) is a subgroup of breast cancer discovered at the molecular level in 2007. Claudin is one of the primary proteins that make up tight junctions, and it plays crucial roles in anti-inflammatory and antitumor responses as well as the maintenance of water and electrolyte balance. Decreased expression of claudin results in the disruption of tight junction structures and the activation of downstream signaling pathways, which can lead to tumor formation. The origin of Claudin-low breast cancer is still in dispute. Claudin-low breast cancer is characterized by low expression of Claudin3, 4, 7, E-cadherin, and HER2 and high expression of Vimentin, Snai 1/2, Twist 1/2, Zeb 1/2, and ALDH1, as well as stem cell characteristics. The clinical onset of claudin-low breast cancer is at menopause age, and its histological grade is higher. This subtype of breast cancer is more likely to spread to lymph nodes than other subtypes. Claudin-low breast cancer is frequently accompanied by increased invasiveness and a poor prognosis. According to a clinical retrospective analysis, claudin-low breast cancer can achieve low pathological complete remission. At present, although several therapeutic targets of claudin-low breast cancer have been identified, the effective treatment remains in basic research stages, and no animal studies or clinical trials have been designed. The origin, molecular biological characteristics, pathological characteristics, treatment, and prognosis of CLBC are extensively discussed in this article. This will contribute to a comprehensive understanding of CLBC and serve as the foundation for the individualization of breast cancer treatment.

Differential Expression of Claudin 1 and 4 in Basal Cell Carcinoma of the Skin

Basal cell carcinoma (BCC) is the most common human malignancy. The biological behavior of this entity is remarkably indolent. Claudin plays an important role in tight junctions, regulating paracellular passage of variable substance including growth factors and maintaining the polarity of epithelia. Up- or downregulated claudin expression has been reported in many cancers. Nevertheless, claudin expression in BCC of the skin remains unclear. We therefore examined the status of claudin 1 and 4 expressions in BCC and adjacent normal skin by immunohistochemistry (IHC). Our IHC results demonstrated high claudin 1 expression and low claudin 4 expression in 33 of 34 lower-grade BCCs. In lower-grade BCC, claudin 1 was increased and claudin 4 was decreased compared with the normal skin. Claudin 1 was inclined to be highly expressed in the membrane and cytoplasm of tumour cells in the periphery of tumour nest. Conversely, almost all lower-grade BCCs (33/34) and one of two higher-grade BCC lacked or showed focal positivity for claudin 4. These results imply that the expression pattern is characteristics of lower-risk BCC. Interestingly, one of the two higher-grade BCCs demonstrated the converse expression patterns of claudins, with decreased claudin 1 and increased claudin 4. The combination of immunohistochemical claudin 1 and 4 expression may offer a useful ancillary tool for the pathological diagnosis of BCC. Furthermore, membranous and intracellular claudins may present future therapeutic targets for uncontrollable BCC.

The Role of Claudin-1 Expression in Follicular and Papillary Thyroid Neoplasm

OBJECTIVE

This study evaluated differences in Claudin-1 expression between follicular adenoma (FA), follicular thyroid carcinoma (FTC), follicular variant papillary thyroid carcinoma (FV-PTC), and papillary thyroid carcinoma (PTC).

MATERIAL AND METHODS

This study used a cross-sectional approach. Immunostaining using the polyclonal antibody Claudin-1 was performed on 75 samples divided into 20 samples for follicular adenoma, follicular thyroid carcinoma, papillary carcinoma, and 15 samples of follicular variant thyroid carcinoma, respectively.

RESULTS

Claudin-1 expression is detected on the cytoplasmic membrane of tumor cells and appears to be varied among thyroid neoplasms. The claudin-1 expression score revealed a statistically significant difference between FA against FV-PTC, FA versus (vs) PTC, and FTC vs PTC, with median values of 4 vs 6 (p = 0.016), 4 vs 8 (p = 0.001), and 5 vs 8 (p = 0.002), respectively. However, there was no statistically significant difference in scores between the FA and the FTC (4 vs 5), or between the FTC and the FV-PTC groups (5 vs 6 (p=1,000).

CONCLUSION

These results suggest that Claudin-1 may be capable of discriminating follicular adenoma from classic and follicular variant of papillary thyroid carcinoma. It can also differentiate follicular thyroid carcinoma and papillary thyroid carcinoma, especially for cases challenging to assess by hematoxylin and eosin staining. It still holds promise in providing targeted cancer therapy.

Research progress of tight junction protein claudin-3 in hepatobiliary systemic diseases

Claudin-3 is an important member of the claudin family of tight junction proteins and is the most abundant tight junction protein in the hepatobiliary system. It plays an important role in building tight junctions of hepatobiliary cells, and maintaining cellular barrier function and molecular delivery function. Dysregulation of hepatic claudin-3 expression leads to disruption of hepatobiliary system junctions, metabolic function, barrier function, proliferation capacity, and molecular delivery function, and is closely related to the development of various hepatobiliary diseases such as hepatic malignancies, cholesterol stones, and chronic liver diseases. In this paper, we review the progress in the research of claudin-3 in hepatobiliary diseases.

Evolution of predictive and prognostic biomarkers in the treatment of advanced gastric cancer

Despite new therapeutic options, advanced gastric cancer remains associated with a poor prognosis compared with other cancers. Recent gains in the treatment of gastric cancer were accompanied by the identification of novel biomarkers associated with various cellular pathways and corresponding diagnostic technologies. It is expected that the standardization of clinical workflow and technological refinements in biomarker assessment will support greater personalization and further improve treatment outcomes. In this article, we review the current state of prognostic and predictive biomarkers in gastric cancer.

Claudin18.2 is a novel molecular biomarker for tumor-targeted immunotherapy

The claudin18.2 (CLDN18.2) protein, an isoform of claudin18, a member of the tight junction protein family, is a highly selective biomarker with limited expression in normal tissues and often abnormal expression during the occurrence and development of various primary malignant tumors, such as gastric cancer/gastroesophageal junction (GC/GEJ) cancer, breast cancer, colon cancer, liver cancer, head and neck cancer, bronchial cancer and non-small-cell lung cancer. CLDN18.2 participates in the proliferation, differentiation and migration of tumor cells. Recent studies have identified CLDN18.2 expression as a potential specific marker for the diagnosis and treatment of these tumors. With its specific expression pattern, CLDN18.2 has become a unique molecule for targeted therapy in different cancers, especially in GC; for example, agents such as zolbetuximab (claudiximab, IMAB362), a monoclonal antibody (mAb) against CLDN18.2, have been developed. In this review, we outline recent advances in the development of immunotherapy strategies targeting CLDN18.2, including monoclonal antibodies (mAbs), bispecific antibodies (BsAbs), chimeric antigen receptor T (CAR-T) cells redirected to target CLDN18.2, and antibody–drug conjugates (ADCs).

Claudins and Gastric Cancer: An Overview

Simple Summary

Gastric cancer (GC) is one of the most common cancers and the third leading cause of cancer deaths worldwide, with a high frequency of recurrence and metastasis, and a poor prognosis. This review presents novel biological and clinical significance of claudin (CLDN) expression in GC, especially CLDN18, and clinical trials centered around CLDN18.2. It also presents new findings for other CLDNs.

Abstract

Despite recent improvements in diagnostic ability and treatment strategies, advanced gastric cancer (GC) has a high frequency of recurrence and metastasis, with poor prognosis. To improve the treatment results of GC, the search for new treatment targets from proteins related to epithelial–mesenchymal transition (EMT) and cell–cell adhesion is currently being conducted. EMT plays an important role in cancer metastasis and is initiated by the loss of cell–cell adhesion, such as tight junctions (TJs), adherens junctions, desmosomes, and gap junctions. Among these, claudins (CLDNs) are highly expressed in some cancers, including GC. Abnormal expression of CLDN1, CLDN2, CLDN3, CLDN4, CLDN6, CLDN7, CLDN10, CLDN11, CLDN14, CLDN17, CLDN18, and CLDN23 have been reported. Among these, CLDN18 is of particular interest. In The Cancer Genome Atlas, GC was classified into four new molecular subtypes, and CLDN18–ARHGAP fusion was observed in the genomically stable type. An anti-CLDN18.2 antibody drug was recently developed as a therapeutic drug for GC, and the results of clinical trials are highly predictable. Thus, CLDNs are highly expressed in GC as TJs and are expected targets for new antibody drugs. Herein, we review the literature on CLDNs, focusing on CLDN18 in GC.

Immunoexpression of E-cadherin, CD44 and Claudin 7 in gastric adenocarcinomas

Gastric adenocarcinomas represent frequent malignant tumors in the digestive tract, with a high and constant mortality rate in last decades. The disturbance of the adhesion molecules expression, which normally is essential in maintaining epithelial homeostasis, has a critical role in the initiation and progression of tumors. In this study, we analyzed the immunoexpression of E-cadherin, cluster of differentiation 44 (CD44), and Claudin 7 in 58 cases of gastric adenocarcinomas, in relation to the histopathological parameters of the lesions' aggressiveness. Increased E-cadherin immunoexpression was observed in tubular adenocarcinomas, those of low grade and in stages I-III. CD44 presented high scores in discohesive, hepatoid, tubular, and tubulopapillary adenocarcinomas, those of high grade and in advanced stages. Claudin 7 associated increased scores for tubular, tubulopapillary and micropapillary tumors, those of low grade and mainly in stage I. The markers used in the study can be useful for assessing the aggressiveness of gastric adenocarcinomas, in the context of specific adapted therapy.

Role of Barrier Integrity and Dysfunctions in Maintaining the Healthy Gut and Their Health Outcomes

Mucosal surface layers are the critical borders throughout epithelial membranes. These epithelial cells segregate luminal material from external environments. However, mucosal linings are also accountable for absorbing nutrients and requiring specific barrier permeability. These functional acts positioned the mucosal epithelium at the epicenter of communications concerning the mucosal immune coordination and foreign materials, such as dietary antigens and microbial metabolites. Current innovations have revealed that external stimuli can trigger several mechanisms regulated by intestinal mucosal barrier system. Crucial constituents of this epithelial boundary are physical intercellular structures known as tight junctions (TJs). TJs are composed of different types transmembrane proteins linked with cytoplasmic adaptors which helps in attachment to the adjacent cells. Disruption of this barrier has direct influence on healthy or diseased condition, as barrier dysfunctions have been interrelated with the initiation of inflammation, and pathogenic effects following metabolic complications. In this review we focus and overview the TJs structure, function and the diseases which are able to influence TJs during onset of disease. We also highlighted and discuss the role of phytochemicals evidenced to enhance the membrane permeability and integrity through restoring TJs levels.

Effective Oncoleaking Treatment of Pancreatic Cancer by Claudin-Targeted Suicide Gene Therapy with Clostridium perfringens Enterotoxin (CPE)

Simple Summary

Current therapies for pancreas carcinoma (PC) are of limited efficacy due to tumor aggressiveness and therapy resistance. Bacterial toxins with pore-forming (oncoleaking) potential are promising tools in cancer therapy. We have developed a novel, suicide gene therapy treatment, based on Clostridium perfringens enterotoxin (CPE)-mediated oncoleaking. This is achieved by CPE suicide gene therapy to treat PC, which overexpresses the claudin-3 and -4 (Cldn3/4) tight junction proteins, which are targets of CPE action. This targeted gene therapy causes rapid eradication of Cldn3/4 overexpressing PC cells via oncoleaking and initiation of apoptotic/necrotic signaling. We demonstrate efficacy of this approach in vitro and after nonviral in vivo gene transfer in cell lines and in patient derived xenograft PC models. This therapy approach has translational potential for treatment of pancreas carcinomas and could also be translated into new combination settings with conventional chemotherapy.

Abstract

Pancreatic cancer (PC) is one of the most lethal cancers worldwide, associated with poor prognosis and restricted therapeutic options. Clostridium perfringens enterotoxin (CPE), is a pore-forming (oncoleaking) toxin, which binds to claudin-3 and -4 (Cldn3/4) causing selective cytotoxicity. Cldn3/4 are highly upregulated in PC and represent an effective target for oncoleaking therapy. We utilized a translation-optimized CPE vector (optCPE) for new suicide approach of PC in vitro and in cell lines (CDX) and patient-derived pancreatic cancer xenografts (PDX) in vivo. The study demonstrates selective toxicity in Cldn3/4 overexpressing PC cells by optCPE gene transfer, mediated by pore formation, activation of apoptotic/necrotic signaling in vitro, induction of necrosis and of bystander tumor cell killing in vivo. The optCPE non-viral intratumoral in vivo jet-injection gene therapy shows targeted antitumoral efficacy in different CDX and PDX PC models, leading to reduced tumor viability and induction of tumor necrosis, which is further enhanced if combined with chemotherapy. This selective oncoleaking suicide gene therapy improves therapeutic efficacy in pancreas carcinoma and will be of value for better local control, particularly of unresectable or therapy refractory PC.

Beyond Chemotherapy, PD-1, and HER-2: Novel Targets for Gastric and Esophageal Cancer

Together, gastric cancer and esophageal cancer (EC) possess two of the highest incidence rates amongst all cancers. They exhibit poor prognoses in which the 5-year survival rate is dismal. In addition to cytotoxic chemotherapy, treatment efforts have been geared toward targeting human epidermal growth factor receptor 2 (HER-2), vascular endothelial growth factor (VEGF), and programmed death ligand-1 (PD-1). Although ample success has been recorded with these agents, gastric and esophageal cancer remain lethal, and further research into potential treatment alternatives is needed. In this article, we will review some of the targets at the forefront of investigation such as claudin, Dickkopf-related protein 1 (DKK-1), fibroblast growth factor receptor (FGFR), and matrix metalloproteinases (MMPs). These innovative target pathways are in the midst of clinical trials to be implemented in the treatment algorithm for this patient population. Ultimately, exploiting the oncogenic tendencies of these potential biomarkers creates an opportunity for precise treatment and improved prognosis for these cancers. Lastly, research aimed toward reversing PD-1 antibodies resistance by combining it with other novel agents or other treatment modalities is underway in order to expand existing treatment options for this patient population.

Microbiome in human cancers

A microbiome is defined as the aggregate of all microbiota that reside in human digestive system and other tissues. This microbiota includes viruses, bacteria, fungi that live in various human organs and tissues like stomach, guts, oesophagus, mouth cavity, urinary tract, vagina, lungs, and skin. Almost 20 % of malignant cancers worldwide are related to microbial infections including bacteria, parasites, and viruses. The human body is constantly being attacked by microbes during its lifetime and microbial pathogens that have tumorigenic effects in 15-20 % of reported cancer cases. Recent scientific advances and the discovery of the effect of microbes on cancer as a pathogen or as a drug have significantly contributed to our understanding of the complex relationship between microbiome and cancer. The aim of this study is to overview some microbiomes that reside in the human body and their roles in cancer.

Context-Dependent Roles of Claudins in Tumorigenesis

The barrier and fence functions of the claudin protein family are fundamental to tissue integrity and human health. Increasing evidence has linked claudins to signal transduction and tumorigenesis. The expression of claudins is frequently dysregulated in the context of neoplastic transformation. Studies have uncovered that claudins engage in nearly all aspects of tumor biology and steps of tumor development, suggesting their promise as targets for treatment or biomarkers for diagnosis and prognosis. However, claudins can be either tumor promoters or tumor suppressors depending on the context, which emphasizes the importance of taking various factors, including organ type, environmental context and genetic confounders, into account when studying the biological functions and targeting of claudins in cancer. This review discusses the complicated roles and intrinsic and extrinsic determinants of the context-specific effects of claudins in cancer.

Chimeric Claudins: A New Tool to Study Tight Junction Structure and Function

The tight junction (TJ) is a structure composed of multiple proteins, both cytosolic and membranal, responsible for cell–cell adhesion in polarized endothelium and epithelium. The TJ is intimately connected to the cytoskeleton and plays a role in development and homeostasis. Among the TJ’s membrane proteins, claudins (CLDNs) are key to establishing blood–tissue barriers that protect organismal physiology. Recently, several crystal structures have been reported for detergent extracted recombinant CLDNs. These structural advances lack direct evidence to support quaternary structure of CLDNs. In this article, we have employed protein-engineering principles to create detergent-independent chimeric CLDNs, a combination of a 4-helix bundle soluble monomeric protein (PDB ID: 2jua) and the apical—50% of human CLDN1, the extracellular domain that is responsible for cell–cell adhesion. Maltose-binding protein-fused chimeric CLDNs (MBP-CCs) used in this study are soluble proteins that retain structural and functional aspects of native CLDNs. Here, we report the biophysical characterization of the structure and function of MBP-CCs. MBP-fused epithelial cadherin (MBP-eCAD) is used as a control and point of comparison of a well-characterized cell-adhesion molecule. Our synthetic strategy may benefit other families of 4-α-helix membrane proteins, including tetraspanins, connexins, pannexins, innexins, and more.

Loss of Claudin-3 Impairs Hepatic Metabolism, Biliary Barrier Function, and Cell Proliferation in the Murine Liver

BACKGROUND & AIMS

Tight junctions in the liver are essential to maintain the blood-biliary barrier, however, the functional contribution of individual tight junction proteins to barrier and metabolic homeostasis remains largely unexplored. Here, we describe the cell type-specific expression of tight junction genes in the murine liver, and explore the regulation and functional importance of the transmembrane protein claudin-3 in liver metabolism, barrier function, and cell proliferation.

METHODS

The cell type-specific expression of hepatic tight junction genes is described using our mouse liver single-cell sequencing data set. Differential gene expression in Cldn3-/- and Cldn3+/+ livers was assessed in young and aged mice by RNA sequencing (RNA-seq), and hepatic tissue was analyzed for lipid content and bile acid composition. A surgical model of partial hepatectomy was used to induce liver cell proliferation.

RESULTS

Claudin-3 is a highly expressed tight junction protein found in the liver and is expressed predominantly in hepatocytes and cholangiocytes. The histology of Cldn3-/- livers showed no overt phenotype, and the canalicular tight junctions appeared intact. Nevertheless, by RNA-seq we detected a down-regulation of metabolic pathways in the livers of Cldn3-/- young and aged mice, as well as a decrease in lipid content and a weakened biliary barrier for primary bile acids, such as taurocholic acid, taurochenodeoxycholic acid, and taurine-conjugated muricholic acid. Coinciding with defects in the biliary barrier and lower lipid metabolism, there was a diminished hepatocyte proliferative response in Cldn3-/- mice after partial hepatectomy.

CONCLUSIONS

Our data show that, in the liver, claudin-3 is necessary to maintain metabolic homeostasis, retention of bile acids, and optimal hepatocyte proliferation during liver regeneration. The RNA-seq data set can be accessed at: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE159914.

Strong impact of pathological node-negative on long-term overall survival of patients with triple-negative breast cancer receiving neoadjuvant chemotherapy

Triple-negative breast cancer (TNBC) has a high pathological complete response (pCR) rate; however patients without a high pCR are reported to have a poor prognosis. The current study investigated the long-term overall survival of patients with TNBC who received neoadjuvant chemotherapy (NAC) and analyzed various prognostic factors including basal marker and claudin expressions. Between November 2005 and March 2012, the current study retrospectively reviewed the records of 323 patients with breast cancer who received anthracycline followed by taxane as NAC at the Jikei University Hospital Basal marker and claudin expression was determined via immunohistochemistry. The median age of the patients was 53.0 years. Of the 323 patients, 26 (8%) achieved a pCR, including 13 patients (19.7%) with TNBC and 13 (5.1%) with non-TNBC (P<0.001). Of the 66 patients with TNBC, 13 (19.7%) demonstrated recurrence and 8 (12.1%) died after a median follow-up time of 111.5 months [10-year disease-free survival (DFS), 80.3%; 95% confidence interval (CI), 0.68-0.88; 10-year overall survival (OS), 84.8%; 95% CI, 0.72-0.92]. Of the 257 patients with non-TNBC, 45 (17.5%) patients demonstrated recurrence and 26 (10.1%) died (10-year DFS, 82.1%; 95% CI, 0.76-0.87; 10-year OS, 88.6%; 95% CI, 0.83-0.92). There was no statistical difference between the patients with and without TNBC. In the TNBC group, patients with pathological node-negative status survived without distant recurrence. Additionally, negative lymphovascular infiltration was another favorable prognostic factor. Patients with TNBC who received NAC demonstrated comparably high prognoses to non-TNBC patients. Overall, pathological node status after NAC had a strong impact on the prognosis of patients with TNBC.

Molecular engineering of antibodies for site-specific conjugation to lipid polydopamine hybrid nanoparticles

Conjugation of antibodies to nanoparticles allows specific cancer targeting, but conventional conjugation methods generate heterogeneous conjugations that cannot guarantee the optimal orientation and functionality of the conjugated antibody. Here, a molecular engineering technique was used for site-specific conjugation of antibodies to nanoparticles. We designed an anti-claudin 3 (CLDN3) antibody containing a single cysteine residue, h4G3cys, then linked it to the maleimide group of lipid polydopamine hybrid nanoparticles (LPNs). Because of their negatively charged lipid coating, LPNs showed high colloidal stability and provided a functional surface for site-specific conjugation of h4G3cys. The activity of h4G3cys was tested by measuring the binding of h4G3cys-conjugated LPNs (C-LPNs) to CLDN3-positive tumor cells and assessing its subsequent photothermal effects. C-LPNsspecifically recognized CLDN3-overexpressing T47D breast cancer cells but not CLDN3-negative Hs578T breast cancer cells. High binding of C-LPNs to CLDN3-overexpressing T47D cells resulted in significantly higher temperature generation upon NIR irradiation and potent anticancer photothermal efficacy. Consistent with this, intravenous injection of C-LPNsin a T47D xenograft mouse model followed by NIR irradiation caused remarkable tumor ablation compared with other treatments through high temperature increases. Our results establish an accurate antibody-linking method and demonstrate the possibility of developing therapeutics using antibody-guided nanoparticles.

The p53-inducible CLDN7 regulates colorectal tumorigenesis and has prognostic significance

Most colorectal cancer (CRC) are characterized by allele loss of the genes located on the short arm of chromosome 17 (17p13.1), including the tumor suppressor p53 gene. Although important, p53 is not the only driver of chromosome 17p loss. In this study, we explored the biological and prognostic significance of genes around p53 on 17p13.1 in CRC. The Cancer Genome Atlas (TCGA) were used to identify differentially expressed genes located between 1000 kb upstream and downstream of p53 gene. The function of CLDN7 was evaluated by both in vitro and in vivo experiments. Quantitative real-time PCR, western blot, and promoter luciferase activity, immunohistochemistry were used to explore the molecular drivers responsible for the development and progression of CRC. The results showed that CLDN7, located between 1000 kb upstream and downstream of p53 gene, were remarkably differentially expressed in tumor and normal tissues. CLDN7 expression also positively associated with p53 level in different stages of the adenoma-carcinoma sequence. Both in vitro and in vivo assays showed that CLDN7 inhibited cell proliferation in p53 wild type CRC cells, but had no effects on p53 mutant CRC cells. Mechanistically, p53 could bind to CLDN7 promoter region and regulate its expression. Clinically, high CLDN7 expression was negatively correlated with tumor size, invasion depth, lymphatic metastasis and AJCC III/IV stage, but was positively associated with favorable prognosis of CRC patients. Collectively, our work uncovers the tumor suppressive function for CLDN7 in a p53-dependent manner, which may mediate colorectal tumorigenesis induced by p53 deletion or mutation.

Increase in Toxicity of Anticancer Drugs by PMTPV, a Claudin-1-Binding Peptide, Mediated via Down-Regulation of Claudin-1 in Human Lung Adenocarcinoma A549 Cells

Claudin-1 (CLDN1), a tight junctional protein, is highly expressed in lung cancer cells and may contribute to chemoresistance. A drug which decreases CLDN1 expression could be a chemosensitizer for enhancing the efficacy of anticancer drugs, but there is no such drug known. We found that PMTPV, a short peptide, which mimics the structure of second extracellular loop (ECL2) of CLDN1, can reduce the protein level of CLDN1 without affecting the mRNA level in A549 cells derived from human lung adenocarcinoma. The PMTPV-induced decrease in CLDN1 expression was inhibited by monodansylcadaverine, a clathrin-mediated endocytosis inhibitor, and chloroquine, a lysosome inhibitor. Quartz crystal microbalance assay showed that PMTPV can directly bind to the ECL2 of CLDN1. In transwell assay, PMTPV increased fluxes of Lucifer yellow (LY), a paracellular flux marker, and doxorubicin (DXR), an anthracycline anticancer drug, without affecting transepithelial electrical resistance. In three-dimensional spheroid culture, the size and cell viability were unchanged by short peptides, but the fluorescence intensity of hypoxia probe LOX-1 was decreased by PMTPV. PMTPV elevated the accumulation and cytotoxicity of DXR in the spheroids. Similar results were observed by knockdown of CLDN1. Furthermore, the sensitivities to cisplatin (CDDP), docetaxel, and gefitinib were enhanced by PMTPV. The level of CLDN1 expression in CDDP-resistant cells was higher than that in parental A549 cells, which was reduced by PMTPV. PMTPV restored the toxicity to DXR in the CDDP-resistant cells. Our data suggest that PMTPV may become a novel chemosensitizer for lung adenocarcinoma.

Claudin expression profile in flat wart and cutaneous squamous cell carcinoma in epidermodysplasia verruciformis

Epidermodysplasia verruciformis (EV) is a genodermatosis related to human beta-papillomavirus (beta-HPV), with a high risk of cutaneous squamous cell carcinoma (cSCC). Claudins are transmembrane proteins expressed in epithelia and may be altered during carcinogenesis. For a better understanding of the role of beta-HPV in cutaneous carcinogenesis, this claudin expression study was conducted on lesions of patients with and without EV. In this study, claudins-1, -2, -3, -4, -5, -7 and -11 expressions were analyzed by applying the immunohistochemistry technique, in samples of 108 normal skin, 39 flat warts and 174 cSCC. The cSCC samples were organized in tissue microarrays. We found that claudin-1 and claudin-3 focal expressions were associated with cSCC (p < 0.001), and claudin-2 focal or negative expression with flat wart (p < 0.001), in EV and NEV (non-EV) groups. For claudin-5, EV group showed a lower chance of focal and negative expression (p < 0.001), and its negative expression was associated with flat wart (p < 0.001) and lower mean age (p < 0.001). Claudins-4, -7 and -11 showed a diffuse expression in almost all studied samples. Our findings suggest that claudin-5 increased expression observed on normal skin, flat wart and cSCC showed association with EV. Claudin-1 and -3 down expression were also observed, but they could not be related to beta-HPV infection.

Kaempferide Enhances Chemosensitivity of Human Lung Adenocarcinoma A549 Cells Mediated by the Decrease in Phosphorylation of Akt and Claudin-2 Expression

Claudins (CLDNs) play crucial roles in the formation of tight junctions. We have reported that abnormal expression of CLDN2 confers chemoresistance in the spheroids of human lung adenocarcinoma A549 cells. A food composition, which can reduce CLDN2 expression, may function to prevent the malignant progression. Here, we found that ethanol extract of Brazilian green propolis (EBGP) and kaempferide, a major component of EBGP, decrease CLDN2 expression. In the two-dimensional culture model, EBGP decreased the tight junctional localization of CLDN2 without affecting that of zonula occludens-1, an adaptor protein, and enhanced paracellular permeability to doxorubicin, a cytotoxic anticancer drug. EBGP reduced hypoxic stress, and enhanced the accumulation and sensitivity of doxorubicin in the spheroid of A549 cells. Kaempferide dose-dependently decreased CLDN2 expression, although dihydrokaempferide and pinocembrin did not. The phosphorylation of Akt, a regulatory factor of CLDN2 expression, was inhibited by kaempferide but not by dihydrokaempferide. The 2,3-double bond in the C ring may be important to inhibit Akt. Kaempferide decreased the mRNA level and promoter activity of CLDN2, indicating that it inhibits the transcription of CLDN2. In accordance with EBGP, kaempferide decreased the tight junctional localization of CLDN2 and increased a paracellular permeability to doxorubicin, suggesting that it diminished the paracellular barrier to small molecules. In addition, kaempferide reduced hypoxic stress, and enhanced the accumulation and sensitivity of doxorubicin in the spheroids. In contrast, dihydrokaempferide did not improve the sensitivity to doxorubicin. Further study is needed using an animal model, but we suggest that natural foods abundantly containing kaempferide are candidates for the prevention of the chemoresistance of lung adenocarcinoma.

The bacterial instrument as a promising therapy for colon cancer

OBJECTIVE

Colon cancer is a great health concern worldwide, as it is the second leading cause of cancer-related death. Conventional treatment of cancer such as surgery, radiotherapy, and chemotherapy are faced with limitations and side effects. Therefore, strategies for the treatment of cancer need to be modified or new strategies replacing the old one.

AIMS

The aim of this study is to review the role of bacteria or their products (such as peptides, bacteriocins, and toxins) as a therapeutic agent for colon cancer.

RESULTS AND CONCLUSION

Recently, the therapeutic role of bacteria and their products in colon cancer treatment holds promise as emerging novel anti-cancer agents. Unlike the conventional treatments, targeted therapy based on the use of bacteria that are able to directly target tumor cells without affecting normal cells is evolving as an alternative strategy. Moreover, several bacterial species were used in live, attenuated or genetically modified that are able to multiply selectively in tumors and inhibiting their growth.

Integrative Gene Expression Profiling Analysis to Investigate Potential Prognostic Biomarkers for Colorectal Cancer

BACKGROUND Despite noteworthy advancements in the multidisciplinary treatment of colorectal cancer (CRC) and deeper understanding in the molecular mechanisms of CRC, many of CRC patients with histologically identical tumors present different treatment response and prognosis. Thus, more evidence on novel predictive and prognostic biomarkers for CRC remains urgently needed. This study aims to identify potential prognostic biomarkers for CRC with integrative gene expression profiling analysis. MATERIAL AND METHODS Differential expression analysis of paired CRC and adjacent normal tissue samples in 6 microarray datasets was independently performed, and the 6 datasets were integrated by the robust rank aggregation method to detect consistent differentially expressed genes (DEGs). Aberrant expression patterns of these genes were further validated in RNA sequencing data. Then, gene set enrichment analysis (GSEA) was performed to investigate significantly dysregulated biological functions in CRC. Finally, univariate, LASSO and multivariate Cox regression models were built to identify key prognostic genes in CRC patients. RESULTS A total of 990 DEGs (495 downregulated and 495 upregulated genes) were acquired after integratedly analyzing the 6 microarray datasets, and 4131 DEGs (2050 downregulated and 2081 upregulated genes) were obtained from the RNA sequencing dataset. Subsequently, these DEGs were intersected and 885 consistent DEGs were finally identified, including 458 downregulated and 427 upregulated genes. Two risky prognostic genes (TIMP1 and LZTS3) and 5 protective prognostic genes (AXIN2, CXCL1, ITLN1, CPT2 and CLDN23) were identified, which were significantly associated with the prognosis of CRC. CONCLUSIONS The 7 genes that we identified would provide more evidence for further applying novel diagnostic and prognostic biomarkers in clinical practice to facilitate personalized treatment of CRC.

Sox2 maintains epithelial cell proliferation in the successional dental lamina

OBJECTIVES

The successional dental lamina is the distinctive structure on the lingual side of the vertebrate tooth germ. The aim of this study was to investigate the relationship among Sox2, Claudin10 and laminin5 and the role of Sox2 in successional dental lamina proliferation during vertebrate tooth development.

MATERIALS AND METHODS

To understand the successional dental lamina, two types of successional tooth formation, that in geckos (with multiple rounds of tooth generation) and that in mice (with only one round of tooth generation), were analysed.

RESULTS

Unique coexpression patterns of Sox2 and Claudin10 expression were compared in the successional dental lamina from the cap stage to the late bell stage in the mouse tooth germ and in juvenile gecko teeth to support continuous tooth replacement. Furthermore, Laminin5 expression was shown in the cap stage and decreased after the bell stage. Upon comparing the epithelial cell cycles and cell proliferation in successional dental lamina regions between mouse and gecko molars using BrdU and IdU staining and pulse-chase methods, distinctive patterns of continuous expression were revealed. Moreover, Sox2 overexpression with a lentiviral system resulted in hyperplastic dental epithelium in mouse molars.

CONCLUSIONS

Our findings indicate that the regulation of Sox2 in dental lamina proliferation is fundamental to the successional dental lamina in both species.

Development of Human Monoclonal Antibody for Claudin-3 Overexpressing Carcinoma Targeting

Most malignant tumors originate from epithelial tissues in which tight junctions mediate cell-cell interactions. Tight junction proteins, especially claudin-3 (CLDN3), are overexpressed in various cancers. Claudin-3 is exposed externally during tumorigenesis making it a potential biomarker and therapeutic target. However, the development of antibodies against specific CLDN proteins is difficult, because CLDNs are four-transmembrane domain proteins with high homology among CLDN family members and species. Here, we developed a human IgG1 monoclonal antibody (h4G3) against CLDN3 through scFv phage display using CLDN3-overexpressing stable cells and CLDN3-embedded lipoparticles as antigens. The h4G3 recognized the native conformation of human and mouse CLDN3 without cross-reactivity to other CLDNs. The binding kinetics of h4G3 demonstrated a sub-nanomolar affinity for CLDN3 expressed on the cell surface. The h4G3 showed antibody-dependent cellular cytotoxicity (ADCC) according to CLDN3 expression levels in various cancer cells by the activation of FcγRIIIa (CD16a). The biodistribution of h4G3 was analyzed by intravenous injection of fluorescence-conjugated h4G3 which showed that it localized to the tumor site in xenograft mice bearing CLDN3-expressing tumors. These results indicate that h4G3 recognizes CLDN3 specifically, suggesting its value for cancer diagnosis, antibody-drug conjugates, and potentially as a chimeric antigen receptor (CAR) for CLDN3-expressing pan-carcinoma.

Impact of chemotherapy on the expression of claudins and cadherins in invasive breast cancer

The importance of the expression profile of claudins in the molecular classification of breast cancer (BC) is currently under investigation. Claudins, together with cadherins, serve an important role in the epithelial-mesenchymal transition and influence the chemosensitivity of cancer cells. Adjuvant chemotherapy is administered following surgical resection in selected cases of BC. Previous neoadjuvant chemotherapy may change the molecular profile of a tumour and subsequently also its chemosensitivity. In the current study, the expression of claudin-1, −3 and −4, E- and N-cadherin and the standard BC biomarkers [oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and marker of proliferation Ki-67 (Ki-67)] in formalin-fixed, paraffin-embedded sections from 62 patients with invasive BC was analysed using immunohistochemistry prior to and following neoadjuvant chemotherapy. The results revealed increased expression of claudin-1 (P=0.03) and decreased expression of claudin-3 (P=0.005), PR (P<0.001) and Ki-67 (P=0.01) following the neoadjuvant therapy. No significant changes in the expression of ER, claudin-4 or E- and N-cadherin were observed following therapy. Furthermore, an association between the expression of claudin-1 and the standard BC markers (P<0.05) was identified. A high expression of claudin-1 was more frequently observed in the triple-negative BC cohort than in the cohort with positive ER, PR and/or HER2 before (P=0.04) and after chemotherapy (P=0.02). The expression of N-cadherin was associated with the expression of ER, PR, HER2 and tumour grade (P<0.05). A positive association between the expression of claudin-3 and E-cadherin (P=0.005) was observed. No association was found between the expression of E- and N-cadherin. In conclusion, significant changes in the expression of claudin-1 and −3 but not in the expression of claudin-4, E- and N-cadherin were observed in samples taken from patients with BC following chemotherapy. These findings indicate that claudins-1 and −3 serve a role in the response of BC to chemotherapy.

Association of Cytokeratin 5 and Claudin 3 expression with BRCA1 and BRCA2 germline mutations in women with early breast cancer

BACKGROUND

It is important to identify biomarkers associated with BRCA mutation in women with early breast cancer (BC) to improve early identification of mutation carriers. Thus, in this study, we examined the protein expression of claudin (CLDN) 3, CLDN4, CLDN7, and E-cadherin. Moreover, we analyzed additional histopathological variables and their associations in familial BC.

METHODS

Immunohistochemical analysis for CLDNs and E-cadherin was performed on 237 BC cases of three different subsets of BC tumors: 62 from BRCA1 mutation carriers, 59 from BRCA2 mutation carriers, and 116 tumors from patients with BRCA wild type (WT) as controls. Histopathological data were also analyzed in the different subgroups. Logistic regression and receiver operation characteristic (ROC) curve were conducted to investigate factors associated with BRCA tumors.

RESULTS

Expression of CLDN3 positively correlated with BRCA-mutated BC. CLDN3 was expressed in 58% of BRCA1-mutated tumors compared to only 7% in BRCA2-mutated tumors (p < 0.001) and 1% in WT tumors (p < 0.001). CK5 and CK14 expression were also more likely to arise in BRCA1 tumors (44 and 16%, respectively) than in the control group (8 and 4%) (p < 0.001, p = 0.012, respectively). We also found a significantly higher proportion of CK5+ among BRCA1 tumors (44%) in comparison with BRCA2-related BC (8%) (p < 0.001). In addition, there was a significant difference between both groups regarding CK14: positive expression in 16 and 5%, respectively (p = 0.030). CK5 and CK14 did not differ between the BRCA2 group and the WT tumors significantly. In a multivariate regression model, expression of CK5 (Odds ratio (OR): 6.46; 95% confidence interval (CI): 1.52-27.43; p = 0.011), and CLDN3 (OR: 200.48; 95% CI: 21.52-1867.61; p < 0.001) were associated with BRCA1 mutation status.

CONCLUSIONS

Our data suggests that CLDN3, CK5, and CK14 in combination with ER, PR and HER2 are associated with BRCA1 mutation status.

Claudin-7 gene knockout causes destruction of intestinal structure and animal death in mice

BACKGROUND

Claudin-7, one of the important components of cellular tight junctions, is currently considered to be expressed abnormally in colorectal inflammation and colorectal cancer. However, there is currently no effective animal model to study its specific mechanism. Therefore, we constructed three lines of Claudin-7 knockout mice using the Cre/LoxP system.

AIM

To determine the function of the tumor suppressor gene Claudin-7 by generating three lines of Claudin-7 gene knockout mice.

METHODS

We crossed Claudin-7-floxed mice with CMV-Cre, vil1-Cre, and villin-CreERT2 transgenic mice, and the offspring were self-crossed to obtain conventional Claudin-7 knockout mice, conditional (intestinal specific) Claudin-7 knockout mice, and inducible conditional Claudin-7 knockout mice. Intraperitoneal injection of tamoxifen into the inducible conditional Claudin-7 knockout mice can induce the knockout of Claudin-7. PCR and agarose gel electrophoresis were used to identify mouse genotypes, and Western blot was used to confirm the knockout of Claudin-7. The mental state, body length, and survival time of these mice were observed. The dying mice were sacrificed, and hematoxylin-eosin (HE) staining and immunohistochemical staining were performed to observe changes in intestinal structure and proliferation markers.

RESULTS

We generated Claudin-7-floxed mice and three lines of Claudin-7 gene knockout mice using the Cre/LoxP system successfully. Conventional and intestinal specific Claudin-7 knockout mice were stunted and died during the perinatal period, and intestinal HE staining in these mice revealed mucosal gland structure disappearance and connective tissue hyperplasia with extensive inflammatory cell infiltration. The inducible conditional Claudin-7 knockout mice had a normal phenotype at birth, but after the induction with tamoxifen, they exhibited a dying state. Intestinal HE staining showed significant inflammatory cell infiltration, and atypical hyperplasia and adenoma were also observed. Intestinal immunohistochemistry analysis showed abnormal expression and distribution of Ki67, and the normal intestinal proliferation balance was disrupted. The intestinal crypt size in inducible conditional Claudin-7 knockout mice was increased compared with control mice (small intestine: 54.1 ± 2.96 vs 38.4 ± 1.63; large intestine: 44.7 ± 1.93 vs 27.4 ± 0.60; P < 0.001).

CONCLUSION

The knockout of Claudin-7 in vivo causes extensive inflammation, atypical hyperplasia, and adenoma in intestinal tissue as well as animal death in mice. Claudin-7 may act as a tumor suppressor gene in the development of colorectal cancer.

Anti-claudin-4 extracellular domain antibody enhances the antitumoral effects of chemotherapeutic and antibody drugs in colorectal cancer

Claudin-4 (CLDN4) is a major epithelial tight junction protein overexpressed in many cancers to maintain the tumor environment. In this report, we aimed to determine the efficacy of targeting CLDN4 in colorectal cancer (CRC) using an anti-CLDN4 extracellular domain antibody, 4D3. CLDN4 was upregulated in CRC metastatic foci. CLDN4 expression in CRC cells was reduced by upregulation of TNFα, which was induced by Clostridium perfringens enterotoxin produced by gut flora. In a nude mouse liver metastasis model, inhibition of metastasis was increased by combination treatment with 5-fluorouracil (FU) and 4D3 compared to that with 5-FU alone. Moreover, combination treatment with 4D3 and anti-epithelial growth factor receptor (EGFR) antibody C225 resulted in more pronounced inhibition of in vitro sphere formation and tumor growth in nude mice compared to that observed with C225 alone. Moreover, the time interval between the administration of 4D3 and that of C225 was important for maximizing the C225-induced inhibition of EGFR phosphorylation. In a nude mouse model, sequential treatment with 4D3 and C225 with a 6-h time interval resulted in more pronounced inhibition of tumor growth than concurrent treatment. These findings suggest that the targeting of CLDN4 enhances the antitumoral effects of chemotherapeutic agents and molecular targeting antibodies when used in combination.

Functionalization of gold-nanoparticles by the Clostridium perfringens enterotoxin C-terminus for tumor cell ablation using the gold nanoparticle-mediated laser perforation technique

A recombinant produced C-terminus of the C. perfringens enterotoxin (C-CPE) was conjugated to gold nanoparticles (AuNPs) to produce a C-CPE-AuNP complex (C-CPE-AuNP). By binding to claudins, the C- CPE should allow to target the AuNPs onto the claudin expressing tumor cells for a subsequent cell killing by application of the gold nanoparticle-mediated laser perforation (GNOME-LP) technique. Using qPCR and immunocytochemistry, we identified the human Caco-2, MCF-7 and OE-33 as well as the canine TiHoDMglCarc1305 as tumor cells expressing claudin-3, -4 and -7. Transepithelial electrical resistance (TEER) measurements of Caco-2 cell monolayer showed that the recombinant C-CPE bound to the claudins. GNOME-LP at a laser fluence of 60 mJ/cm² and a scanning speed of 0.5 cm/s specifically eliminated more than 75% of claudin expressing human and canine cells treated with C-CPE-AuNP. The same laser fluence did not affect the cells when non-functionalized AuNPs were used. Furthermore, most of the claudin non-expressing cells treated with C-CPE-AuNP were not killed by GNOME-LP. Additionally, application of C-CPE-AuNP to spheroids formed by MCF-7 and OE-33 cells grown in Matrigel reduced spheroid area. The results demonstrate that specific ablation of claudin expressing tumor cells is efficiently increased by activated C-CPE functionalized AuNPs using optical methods.

Synthesis, 18F-labelling and radiopharmacological characterisation of the C-terminal 30mer of Clostridium perfringens enterotoxin as a potential claudin-targeting peptide

The cell surface receptor claudin-4 (Cld-4) is upregulated in various tumours and represents an important emerging target for both diagnosis and treatment of solid tumours of epithelial origin. The C-terminal fragment of the Clostridium perfringens enterotoxin cCPE_290-319 appears as a suitable ligand for targeting Cld-4. The synthesis of this 30mer peptide was attempted via several approaches, which has revealed sequential SPPS using three pseudoproline dipeptide building blocks to be the most efficient one. Labelling with fluorine-18 was achieved on solid phase using N-succinimidyl 4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) and 4-[¹⁸F]fluorobenzoyl chloride as ¹⁸F-acylating agents, which was the most advantageous when [¹⁸F]SFB was reacted with the resin-bound 30mer containing an N-terminal 6-aminohexanoic spacer. Binding to Cld-4 was demonstrated via surface plasmon resonance using a protein construct containing both extracellular loops of Cld-4. In addition, cell binding experiments were performed for ¹⁸F-labelled cCPE_290-319 with the Cld-4 expressing tumour cell lines HT-29 and A431 that were complemented by fluorescence microscopy studies using the corresponding fluorescein isothiocyanate-conjugated peptide. The 30mer peptide proved to be sufficiently stable in blood plasma. Studying the in vivo behaviour of ¹⁸F-labelled cCPE_290-319 in healthy mice and rats by dynamic PET imaging and radiometabolite analyses has revealed that the peptide is subject to substantial liver uptake and rapid metabolic degradation in vivo, which limits its suitability as imaging probe for tumour-associated Cld-4.

Emerging clinical significance of claudin-7 in colorectal cancer: a review

Tight junctions (TJs) play an important role in maintaining cell polarity and regulating cell permeability. In recent years, many studies have shown that TJ proteins, especially claudin-7, are closely related to inflammation and the development of various malignant tumors. Claudin-7 plays a significant role in maintaining the physiological functions and pathological conditions of the TJ barrier. The dysregulation of claudin-7 plays a tumor suppressor role or conversely has carcinogenic effects in different target tissues or cells, but the exact underlying mechanism is still unclear. In this review, we will summarize the expression pattern of claudin-7 in tumors, focusing on the expression and regulation of claudin-7 in colorectal cancer and discussing the correlation between claudin-7 and invasion, metastasis and epithelial–mesenchymal transition (EMT) in colorectal cancer. The construction of Cldn7^−/− mice and conventional claudin-7 knockout mouse models has helped determine the mechanisms by which claudin-7 promotes tumorigenesis. Elucidation of the expression and subcellular localization of claudin-7 under pathological conditions will help develop claudin-7 as a useful biomarker for detecting and diagnosing cancer, and thus may help combat the occurrence, development, and invasion of cancers.

Frequent loss of claudin-4 expression in dedifferentiated and undifferentiated endometrial carcinomas

AIMS

Dedifferentiated endometrial carcinomas (DDECs)/undifferentiated endometrial carcinomas (UECs) are aggressive endometrial cancers with frequent genomic inactivation of core components of switch/sucrose non-fermentable (SWI/SNF) complex proteins. Claudin-4, an epithelial intercellular tight junction protein, was recently found to be expressed in SWI/SNF-deficient undifferentiated carcinomas but not in SWI/SNF-deficient sarcomas. The aim of this study was to examine claudin-4 expression in UECs/DDECs and other high-grade uterine carcinomas.

METHODS AND RESULTS

We examined claudin-4 expression by immunohistochemistry (clone 3E2C1) on tissue microarrays that contained 44 UECs/DDECs (24 SWI/SNF-deficient), 50 carcinosarcomas, 164 grade 3 endometrioid carcinomas, 57 serous carcinomas, and 20 clear cell carcinomas. Tumours with <5% claudin-4 expression were considered to be negative. Nearly all SWI/SNF-deficient, and most SWI/SNF-proficient, UECs/DDECs showed a complete absence of claudin-4 expression in the undifferentiated component, whereas the differentiated component in DDECs showed consistent and diffuse claudin-4 expression. Only one SWI/SNF-deficient DDEC showed focal expression of claudin-4 in the undifferentiated component, as compared with diffuse expression in the corresponding differentiated component. Claudin-4 expression was consistently absent in the sarcomatous component of carcinosarcoma, and it was absent in 24% of grade 3 endometrioid carcinomas and serous carcinomas.

CONCLUSION

Claudin-4 expression can be absent or very focal in a subset of high-grade endometrial carcinomas, and is almost always absent in the undifferentiated components of SWI/SNF-deficient UECs/DDECs, despite the apparent epithelial origin in the case of DDECs. Therefore, claudin-4 expression cannot be used to infer mesenchymal or epithelial tumour origin in the endometrium. The consistent loss or down-regulation of claudin-4, a tight junction protein, in SWI/SNF-deficient UECs/DDECs further supports the undifferentiated nature of these tumours.

Low expression of occludin: a predictor of poor prognosis in esophageal squamous cell carcinoma

Occludin is transmembrane protein and a key constituent of tight junction, and might participate in barrier function and fence function of epithelia and endothelia. It has been shown to be aberrantly expressed in malignant tumors and plays a role in carcinogenesis and tumor progression. The prognostic significance of Occludin expression has been implicated in various human cancers. However, the prognostic significance of Occludin expression in esophageal squamous cell carcinoma (ESCC) has not been established. In this study, we screened the tight junction genes aberrantly expressed based on two published gene microarray datasets (GSE20347 and GSE23400), and examined 95 esophageal cancer cases to assess immunohistochemical expression patterns of Occludin based on tissue array. Down-regulation of Occludin expression was shown in ESCC as compared with adjacent non-neoplastic specimens (P = 0.003). Decreased expression of Occludin was correlated with high histological grade (P = 0.017). Decreased expression of Occludin was also correlated with short overall survival (P = 0.014). The results indicated Loss of Occludin expression was associated with poor prognosis in ESCC, and Occludin expression was potentially a good predictor of prognosis in ESCC.

Time- and dose-dependent claudin contribution to biological functions: Lessons from claudin-1 in skin

There are many types of biologic compartments in the body. Tight junctions (TJs) function to create a dynamic paracellular barrier to separate these compartments and maintain homeostasis. The TJ component claudin-1 is the major transmembrane protein responsible for forming the paracellular barrier in the epidermis; other claudins in the epidermis include claudin-3, -4, -12, -23 and -25. Accumulating evidence points to a relationship between claudin-1 and skin diseases; for example, a decrease in claudin-1 is reported in human atopic dermatitis. However, how claudin-1 directly or indirectly contributes to disease in the context of the paracellular barrier is poorly understood. We recently established several mouse lines in which the claudin-1 expression was systematically regulated, and showed that claudin-1 time- and dose-dependently regulates epidermis function and disease in vivo. In this commentary, we will discuss recent progress on this topic, including our latest findings, and remaining or newly arisen issues.

Kaempherol and Luteolin Decrease Claudin-2 Expression Mediated by Inhibition of STAT3 in Lung Adenocarcinoma A549 Cells

Claudin-2 is highly expressed in human lung adenocarcinoma tissues and may be a novel target for cancer chemotherapy because knockdown of claudin-2 decreases cell proliferation. We found that flavonoids including kaempferol, chrysin, and luteolin concentration-dependently decrease claudin-2 expression in lung adenocarcinoma A549 cells. Claudin-2 expression is up-regulated by mitogen-activated protein kinase kinase (MEK)/ extracellular signal-regulated kinase (ERK)/c-Fos and phosphoinositide 3-kinase (PI3K)/Akt/nuclear factor-κB (NF-κB) pathways, but these activities were not inhibited by kaempferol, chrysin, and luteolin. Promoter deletion assay using luciferase reporter vector showed that kaempferol and luteolin inhibit the function of transcriptional factor that binds to the region between −395 and −144 of claudin-2 promoter. The decrease in promoter activity was suppressed by mutation in signal transducers and activators of transcription (STAT)-binding site, which is located between −395 and −144. The phosphorylation level of STAT3 was not decreased, but the binding of STAT3 on the promoter region is suppressed by kaempferol and luteolin in chromatin immunoprecipitation assay. The inhibition of cell proliferation caused by kaempferol and luteolin was partially recovered by ectopic claudin-2 expression. Taken together, kaempferol and luteolin decreased claudin-2 expression and proliferation in A549 cells mediated by the inhibition of binding of STAT3 on the promoter region of claudin-2. The intake of foods and nutrients rich in these flavonoids may prevent lung adenocarcinoma development.

Antiangiogenic effects of oridonin

Background

Oridonin, the major terpene found in Rabdosia rubescens (Henmsl.) Hara, is widely used as a dietary supplement and therapeutic drug. Oridonin has been proven to possess good anti-tumour activity, but little is known about its effect on angiogenesis. The aim of this study was to investigate the antiangiogenic effects of oridonin in vivo and in vitro and prove that oridonin anti-tumour activity is based on suppressing angiogenesis.

Methods

In vitro, the antiangiogenesis effect was studied by proliferation, apoptosis, migration, invasion, and tube formation experiments on human umbilical vascular endothelial cells (HUVECs). In vivo, using the Tg (fli1: GFP) zebrafish model, the embryonic vasculogenesis and postnatal regeneration were evaluated. The vascular endothelial growth factor (VEGF) signalling pathway gene expressions were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the inhibition effects on tumour growth and metastasis were observed using a xenograft zebrafish tumour model and xenograft nude mouse tumour model. Angiogenesis was assayed by immunostaining with cluster of differentiation 31. Importantly, the proteins were identified as being differentially expressed in an in vivo model by two-dimensional electrophoresis-mass spectrometry (2D–MS) and western blot (WB).

Results

The results indicated that oridonin inhibited HUVEC proliferation, migration, invasion, and tube formation and induced cell apoptosis. Oridonin inhibited zebrafish angiogenesis during embryonic development and tail fin regeneration. RT-PCR showed that oridonin decreased the VEGFA, VEGFR2, and VEGFR3 expressions in zebrafish, while the TP53 expression increased. Moreover, oridonin had strong effects on tumour growth and metastasis in vivo. 2D–MS identified a total of 50 proteins differentially expressed (17 up-expressed, 28 down-expressed). Lastly, WB showed that Claudin 1, Claudin 4, and Claudin 7 were closely related to tumour growth and metastasis.

Conclusion

This study demonstrated that oridonin could inhibit tumour growth and metastasis, which mainly based on oridonin antiangiogenic effects. Claudin 1, Claudin 4, and Claudin 7 were the main contributors to the mechanism.

Rapid eradication of colon carcinoma by Clostridium perfringens Enterotoxin suicidal gene therapy

Background

Bacterial toxins have evolved to an effective therapeutic option for cancer therapy. The Clostridium perfringens enterotoxin (CPE) is a pore-forming toxin with selective cytotoxicity. The transmembrane tight junction proteins claudin-3 and -4 are known high affinity CPE receptors. Their expression is highly upregulated in human cancers, including breast, ovarian and colon carcinoma. CPE binding to claudins triggers membrane pore complex formation, which leads to rapid cell death. Previous studies demonstrated the anti-tumoral effect of treatment with recombinant CPE-protein. Our approach aimed at evaluation of a selective and targeted cancer gene therapy of claudin-3- and/or claudin-4- expressing colon carcinoma in vitro and in vivo by using translation optimized CPE expressing vector.

Methods

In this study the recombinant CPE and a translation optimized CPE expressing vector (optCPE) was used for targeted gene therapy of claudin-3 and/or -4 overexpressing colon cancer cell lines. All experiments were performed in the human SW480, SW620, HCT116, CaCo-2 and HT-29 colon cancer and the isogenic Sk-Mel5 and Sk-Mel5 Cldn-3-YFP melanoma cell lines. Claudin expression analysis was done at protein and mRNA level, which was confirmed by immunohistochemistry. The CPE induced cytotoxicity was analyzed by the MTT cytotoxicity assay. In addition patient derived colon carcinoma xenografts (PDX) were characterized and used for the intratumoral in vivo gene transfer of the optCPE expressing vector in PDX bearing nude mice.

Results

Claudin-3 and -4 overexpressing colon carcinoma lines showed high sensitivity towards both recCPE application and optCPE gene transfer. The positive correlation between CPE cytotoxicity and level of claudin expression was demonstrated. Transfection of optCPE led to targeted, rapid cytotoxic effects such as membrane disruption and necrosis in claudin overexpressing cells. The intratumoral optCPE in vivo gene transfer led to tumor growth inhibition in colon carcinoma PDX bearing mice in association with massive necrosis due to the intratumoral optCPE expression.

Conclusions

This novel approach demonstrates that optCPE gene transfer represents a promising and efficient therapeutic option for a targeted suicide gene therapy of claudin-3 and/or claudin-4 overexpressing colon carcinomas, leading to rapid and effective tumor cell killing in vitro and in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3123-x) contains supplementary material, which is available to authorized users.

Claudin-4 activity in ovarian tumor cell apoptosis resistance and migration

Background

Claudin-4 is a transmembrane protein expressed at high levels in the majority of epithelial ovarian tumors, irrespective of subtype, and has been associated with tumor cells that are both chemoresistant and highly mobile. The objective of this study was to determine the functional role that claudin-4 plays in apoptosis resistance and migration as well as the therapeutic utility of targeting claudin-4 activity with a small mimic peptide.

Methods

We examined claudin-4 activity in human ovarian tumor cell lines (SKOV3, OVCAR3, PEO4) using in vitro caspase and scratch assays as well as an in vivo mouse model of ovarian cancer. Claudin-4 activity was disrupted by treating cells with a small peptide that mimics the DFYNP sequence in the second extracellular loop of claudin-4. Claudin-4 expression was also altered using shRNA-mediated gene silencing.

Results

Both the disruption of claudin-4 activity and the loss of claudin-4 expression significantly increased tumor cell caspase-3 activation (4 to 10-fold, respectively) in response to the apoptotic inducer staurosporine and reduced tumor cell migration by 50 %. The mimic peptide had no effect on cells that lacked claudin-4 expression. Female athymic nude mice bearing ZsGreen-PEO4 ovarian tumors showed a significant decrease in ovarian tumor burden, due to increased apoptosis, after treatment with intraperitoneal injections of 4 mg/kg mimic peptide every 48 h for three weeks, compared to control peptide treated mice.

Conclusion

Claudin-4 functionally contributes to both ovarian tumor cell apoptosis resistance and migration and targeting extracellular loop interactions of claudin-4 may have therapeutic implications for reducing ovarian tumor burden.

Efficacy and safety evaluation of claudin-4-targeted antitumor therapy using a human and mouse cross-reactive monoclonal antibody

Claudin‐4 (CLDN‐4), a tight‐junction protein, is overexpressed in various malignant tumors, including gastric, colorectal, pancreatic, and breast cancers. However, CLDN‐4 is also expressed in normal tissues, including the liver, pancreas, kidney, and small intestine. Whether CLDN‐4 is an effective and safe target for cancer therapy has been unclear owing to the lack of a binder with both CLDN‐4 specificity and cross‐reactivity to human and murine cells. In this study, we successfully generated a rat anti‐CLDN‐4 monoclonal antibody (5D12) that was specific to, and cross‐reactive with, human and mouse CLDN‐4. 5D12 recognized the second extracellular domain of human CLDN‐4 in a conformation‐dependent manner. A human–rat chimeric IgG1 of 5D12 (xi‐5D12) activated the FcγIIIa receptor, indicating the activation of antibody‐dependent cellular cytotoxicity in CLDN‐4‐expressing cells. Moreover, xi‐5D12 significantly suppressed tumor growth in mice bearing human colorectal and gastric tumors without apparent adverse effects, such as weight loss or liver and kidney damage. These results suggest that CLDN‐4 is a potent target for cancer therapy and that an anti‐CLDN‐4 antibody is a promising candidate anticancer agent.

Nuclear localization of tricellulin promotes the oncogenic property of pancreatic cancer

Accumulating evidence has shown that dysregulation of tight junctions (TJs) is involved in tumor development and progression. In this study, we investigated the expression and subcellular distribution of tricellulin, which constitutes tricellular TJs, using human pancreatic adenocarcinomas. In well-differentiated pancreatic adenocarcinoma tissues, tricellulin immunostaining was prominent in the cytoplasm and the plasma membrane. In contrast, in poorly differentiated tissues, its immunostaining was predominantly observed in the nuclei and was almost absent in the plasma membrane. The distinct immunostaining of tricellulin successfully distinguished poorly differentiated adenocarcinoma from moderately and well-differentiated adenocarcinomas with high levels of sensitivity and specificity. Nuclear tricellulin expression significantly correlated with lymph node metastasis, lymphatic invasion and poor survival. In pancreatic cancer cell lines, tricellulin localization shifted from the membrane to nucleus with decreasing differentiation status. Nuclear localization of tricellulin promoted cell proliferation and invasiveness possibly in association with MAPK and PKC pathways in pancreatic cancers. Our results provide new insights into the function of tricellulin, and its nuclear localization may become a new prognostic factor for pancreatic cancers.

Diagnostic Usefulness of Claudin-3 and Claudin-4 for Immunocytochemical Differentiation between Metastatic Adenocarcinoma Cells and Reactive Mesothelial Cells in Effusion Cell Blocks

OBJECTIVE

Claudin-3 and claudin-4 have recently been reported as promising targets for the detection and diagnosis of cancer. This study was designed to evaluate the diagnostic value of claudin-3 and claudin-4 immunoreactivity to distinguish metastatic adenocarcinoma cells (MAC) from reactive mesothelial cells (RMC) in effusions.

STUDY DESIGN

Claudin-3 and claudin-4 immunocytochemical staining was performed on 234 cell block specimens, including 194 malignant effusions with MAC and 40 benign effusions with RMC. Any degree of membranous staining was considered positive.

RESULTS

Claudin-3 was positive in 190 (97.9%) out of 194 cases with MAC and in 3 (7.5%) out of 40 cases with RMC. Claudin-4 immunoreactivity was seen in all 194 (100%) cases with MAC and in 11 (27.5%) out of 40 cases with RMC. In all claudin-3- or claudin-4-positive RMC samples, the area of positive staining was <25% of the cells. Claudin-3 and claudin-4 efficiently discriminated between MAC and RMC (p < 0.001 for both), and claudin-3 was more specific than claudin-4 in differentiating between MAC and RMC (p < 0.05).

CONCLUSION

These results suggest that claudin-3 and claudin-4 are good candidates to be included as MAC markers in the panel of antibodies to distinguish MAC from RMC in effusion specimens.