The role and mechanism of claudins in cancer

Clinical significance and biological role of claudin-1 in oral squamous cell carcinoma cells

OBJECTIVES

Claudin (CLD), a major component of tight junctions, is a four-transmembrane protein, and 24 subtypes have been reported in humans. CLD expression is highly tissue-specific; CLD1 has been reported to be expressed in the skin and mucosa. There have been few reports on CLD1 expression and its function in oral cancer.

MATERIALS AND METHODS

This retrospective study immunohistochemically evaluated CLD1 expression as prognostic predictors in 84 participants with oral squamous cell carcinoma (OSCC). Participants were classified as positive or negative based on staining intensity; the clinicopathologic characteristics and survival rates of the two groups were compared. To clarify the biological role of CLD1 in OSCC cells, we examined the effects of CLD1 overexpression on the invasion and proliferation of the OSCC cell line, SCCKN.

RESULTS

We observed the immunohistochemical CLD1 expression in the cell membranes of OSCC cells. The disease-free survival rate was significantly lower in patients with CLD1-positive OSCC than in patients with CLD1-negative OSCC (P < .05). In vitro studies showed that cell proliferative capacity, motility, proteolytic activity, and invasive growth were promoted in CLD1-overexpressing SCCKN cells compared to those in control SCCKN cells.

CONCLUSION

CLD1 may be a useful and potential prognostic factor for OSCC treatment.

Extrajunctional CLDN10 cooperates with LAT1 and accelerates clear cell renal cell carcinoma progression

BACKGROUND & AIMS

In addition to their adhesive properties, cell adhesion molecules such as claudins (CLDNs) exhibit signaling ability to organize diverse cellular events. Although the CLDN-adhesion signaling stimulates or inhibits cancer progression, the underlying mechanism remains poorly established. Here, we verified whether and how CLDN10 promotes intracellular signals and malignant phenotypes in clear cell renal cell carcinoma (ccRCC).

METHODS

We developed a novel monoclonal antibody that specifically recognizes CLDN10. By immunohistochemistry using this antibody, the clinicopathological significance of aberrant CLDN10 expression in 165 ccRCC patients was determined. We next generated the ccRCC cells (786-O, ACHN, and OS-RC-2) expressing CLDN10, and compared their phenotypes with those of control cells. Immunoprecipitation-mass spectrometry was used to identify a CLDN10-interacting protein, followed by evaluation of its association with CLDN10 and loss-of-functions in ccRCC cells.

RESULTS

High CLDN10 expression predicted poor outcome in ccRCC patients and represented an independent prognostic marker for cancer-specific survival. Cell surface CLDN10 promoted cell viability, proliferation, and migration of ccRCC cells, as well as their tumor growth. CLDN10 also activated mTOR signaling and expression of downstream targets, including MYC target genes. Notably, we found that CLDN10 forms a complex with an amino acid transporter, LAT1, and that CLDN10-LAT1 signaling facilitates malignant phenotypes in ccRCC cells. Structural prediction and immunoprecipitation analysis results strongly suggest an interaction between CLDN10-TM1 (transmembrane domain 1) and LAT1-TM4.

CONCLUSIONS

We conclude that CLDN10-LAT1 signaling drives ccRCC progression. Taken together with our previous findings on CLDN-Src-family kinases signaling, CLDNs propagate distinct intracellular signals depending on their association with different binding partners.

Reduction of Chemoresistance by Claudin-14-Targeting Peptide in Human Colorectal Cancer Cells

The expression of claudins (CLDNs), major components of tight junctions (TJs), is abnormal in various solid tumors. CLDN14 is highly expressed in human colorectal cancer (CRC) tissues and confers chemoresistance. CLDN14 may become a novel therapeutic target for CRC, but CLDN14-targeting drugs have not been developed. Here, we searched for a CLDN14-targeting peptide, which can suppress CLDN14 expression and chemoresistance using human CRC-derived DLD-1 and LoVo cells. Among some short peptides which mimic the second extracellular loop structure of CLDN14, PSGMK most strongly suppressed the protein expression of CLDN14. The mRNA expression of other endogenous TJ components was unchanged by PSGMK. The PSGMK-induced reduction of CLDN14 protein was inhibited by chloroquine, a lysosome inhibitor, and monodansylcadaverine, a clathrin-dependent endocytosis inhibitor, indicating that PSGMK may enhance endocytosis and lysosomal degradation of CLDN14. In a three-dimensional culture model, the oxidative stress was significantly reduced by PSGMK, whereas hypoxia stress was not. Furthermore, the expression levels of nuclear factor erythroid 2-related factor 2, an oxidative stress response factor, and its target genes were decreased by PSGMK. These results suggest that PSGMK relieves stress conditions in spheroids. The cell viability of spheroids was decreased by anticancer drugs such as doxorubicin and oxaliplatin, which was exaggerated by the cotreatment with PSGMK. Our data indicate that CLDN14-targeting peptide, PSGMK has an anti-chemoresistance effect in CRC cells.

Histone H3K9 Methylation Is Differentially Modified in Odontogenic Cyst and Tumors

OBJECTIVES

 Histone modification in odontogenic lesions is mostly unexplored. Trimethylation of histone H3 at lysine residue 9 (H3K9Me3) has been studied in various pathologic conditions and showed biological significance promising for future therapeutic application. This study aimed to investigate the level and clinical relevance of the H3K9Me3 histone modification in odontogenic cysts and tumors.

MATERIALS AND METHODS

 A total of 105 cases of odontogenic lesions, comprising 30 odontogenic keratocysts (OKCs), 30 adenomatoid odontogenic tumors (AOTs), 30 ameloblastomas, and 15 dental follicles, were included in the study. The paraffin-embedded tissues were immunohistochemically stained for H3K9Me3. Both the intensity and the distribution of staining were evaluated and calculated as H-score. The correlation between the H3K9Me3 expression and the clinical characteristics of each lesion was evaluated.

STATISTICAL ANALYSIS

 The Kruskal-Wallis test followed by Bonferroni's correction was performed to assess the differences in H-score among groups. In addition, Pearson's chi-squared test or Mann-Whitney U test was used to analyze potential factors that could affect protein expression.

RESULTS

 The reduced enamel epithelium of the dental follicle showed uniformly strong H3K9Me3 expression. All odontogenic cysts and tumors examined demonstrated a significantly reduced H3K9Me3 level compared with dental follicles. The AOT showed the lowest H3K9Me3 level, followed by OKC and ameloblastoma. Its immunoreactivity was mainly localized in the basal and parabasal cells of OKC and the whorled/duct-like structures of AOT. Ameloblastoma exhibited marked variation in the H3K9Me3 level among cases. Notably, the upregulated H3K9Me3 was related to multilocularity of OKC and ameloblastoma.

CONCLUSIONS

 Histone H3K9 methylation is differentially expressed in odontogenic cysts and tumors. This epigenetic modification may contribute to the pathogenesis and aggressive behavior of odontogenic lesions.

Apolipoproteins have a major role in cellular tumor dormancy in triple negative breast cancer: In-silico study

Triple-negative breast cancer (TNBC) lacks estrogen, progesterone, and human epidermal growth factor receptors and has a poor prognosis as it is resistant to chemotherapy. A new treatment option for this type of cancer may be by putting these malignant cells into dormancy. The oocyte's embryonic milieu presents a unique tumor reversion microenvironment by inducing growth arrest and changing cells' phenotypes. We conducted an in-silico study to determine the most likely oocyte extract (OE) proteins involved in inducing dormancy using HDock, CluPro, and molecular dynamic (MD) simulation. Results showed low energy scores for complexes between OE proteins and four surface markers: K1C14, CLD3, CLD4, and ITA6. Apolipoprotein A1 (APOA1) and Apolipoprotein C3 (APOC3) showed the highest stability and affinity with these four surface markers: K1C14, CLD3, CLD4, and ITA6. These proteins are involved in key tumor-related pathways such as angiogenesis, proliferation, apoptosis, and migration. This will pave the way for exploring novel therapeutic options to induce dormancy in TNBC cells.

Synthesis, preclinical evaluation and pilot clinical translation of [68Ga]Ga-PMD22, a novel nanobody PET probe targeting CLDN18.2 of gastrointestinal cancer

PURPOSE

Claudin18.2 (CLDN18.2) is a novel target for diagnosis and therapy of gastrointestinal cancer. This study aimed to evaluate the safety and feasibility of a novel CLDN18.2-targeted nanobody, PMD22, labeled with gallium-68 ([68Ga]Ga), for detecting CLDN18.2 expression in patients with gastrointestinal cancer using PET/CT imaging.

METHODS

[68Ga]Ga-PMD22 was synthesized based on the nanobody, and its cell binding properties were assayed. Preclinical pharmacokinetics were determined in CLDN18.2-positive xenografts using microPET/CT. Effective dosimetry of [68Ga]Ga-PMD22 was evaluated in 5 gastrointestinal cancer patients, and PET/CT imaging of [68Ga]Ga-PMD22 and [18F]FDG were performed head-to-head in 16 gastrointestinal cancer patients. Pathological tissues were obtained for CLDN18.2 immunohistochemical (IHC) staining and comparative analysis with PET/CT findings.

RESULTS

Cell binding assay showed that [68Ga]Ga-PMD22 had a higher binding ability to AGSCLDN18.2 and BGC823CLDN18.2 cells than to AGS and BGC823 cells (p < 0.001). MicroPET/CT images showed that [68Ga]Ga-PMD22 rapidly accumulated in AGSCLDN18.2 and BGC823CLDN18.2 tumors, and high contrast tumor to background imaging was clearly observed. In the pilot study, the effective dose of [68Ga]Ga-PMD22 was 1.68E-02 ± 1.45E-02 mSv/MBq, and the CLDN18.2 IHC staining result was highly correlated with the SUVmax/BKGstomach of [68Ga]Ga-PMD22 (rs = 0.848, p < 0.01).

CONCLUSION

A novel [68Ga]Ga-labeled nanobody probe targeting CLDN18.2, [68Ga]Ga-PMD22, was established and preliminarily proved to be safe and effective in revealing CLDN18.2-positive gastrointestinal cancer, providing a basis for the clinical translation of the agent.

CLINICAL TRIAL REGISTRATION

This study was registered on the ClinicalTrials.gov (NCT05937919).

Role of Exosomes in Salivary Gland Tumors and Technological Advances in Their Assessment

Backgroud: Salivary gland tumors (SGTs) are rare and diverse neoplasms, presenting significant challenges in diagnosis and management due to their rarity and complexity. Exosomes, lipid bilayer vesicles secreted by almost all cell types and present in all body fluids, have emerged as crucial intercellular communication agents. They play multifaceted roles in tumor biology, including modulating the tumor microenvironment, promoting metastasis, and influencing immune responses. Results: This review focuses on the role of exosomes in SGT, hypothesizing that novel diagnostic and therapeutic approaches can be developed by exploring the mechanisms through which exosomes influence tumor occurrence and progression. By understanding these mechanisms, we can leverage exosomes as diagnostic and prognostic biomarkers, and target them for therapeutic interventions. The exploration of exosome-mediated pathways contributing to tumor progression and metastasis could lead to more effective treatments, transforming the management of SGT and improving patient outcomes. Ongoing research aims to elucidate the specific cargo and signaling pathways involved in exosome-mediated tumorigenesis and to develop standardized techniques for exosome-based liquid biopsies in clinical settings. Conclusions: Exosome-based liquid biopsies have shown promise as non-invasive, real-time systemic profiling tools for tumor diagnostics and prognosis, offering significant potential for enhancing patient care through precision and personalized medicine. Methods like fluorescence, electrochemical, colorimetric, and surface plasmon resonance (SPR) biosensors, combined with artificial intelligence, improve exosome analysis, providing rapid, precise, and clinically valid cancer diagnostics for difficult-to-diagnose cancers.

Deciphering the role of claudins in lung cancer

Lung cancer remains a major global health challenge, characterized by aggressive malignancy and poor prognostic outcomes. This review article focuses on the pivotal role of claudins, a family of tight junction proteins, in the pathophysiology of lung cancer. Claudins are integral to maintaining epithelial barrier function and cellular polarity, yet they are intricately involved in the progression and metastasis of lung cancer. The aberrant expression of claudins has been observed across various histological subtypes of lung cancer, indicating their potential as diagnostic and prognostic biomarkers. Specifically, claudins such as claudin-1, -2, -3, -4, and -7 exhibit diverse expression patterns that correlate with tumor aggressiveness, patient survival rates, and response to therapies. Inflammation and cytokine modulation significantly influence claudin expression, affecting tumor microenvironment dynamics and cancer progression. This review also highlights the therapeutic implications of targeting claudins, particularly in cases resistant to conventional treatments. Recent advances in this area suggest that claudin-modulating agents may enhance the efficacy of existing therapies and offer new avenues for targeted interventions. By integrating the latest research, this article aims to provide a comprehensive understanding of claudin's roles in lung cancer and encourages further clinical trials to explore claudin-targeting therapies. This could pave the way for more effective management strategies, improving outcomes for lung cancer patients.

Enhancement of chemoresistance by claudin-1-mediated formation of amino acid barriers in human lung adenocarcinoma A549 cells

Claudin-1 (CLDN1) is highly expressed in human lung adenocarcinoma-derived A549 cells and is involved in the augmentation of chemoresistance. However, the mechanism of chemoresistance is not fully understood. In the tumor microenvironment, cancer cells are exposed to stress conditions such as hypoxia and malnutrition. Here, we investigated the effect of CLDN1 expression on amino acid (AA) flux and chemoresistance using A549 cells. The expression of L-type AA transporters, LAT1 and LAT3, was decreased by CLDN1 silencing in A549 spheroids. A reduction in extracellular AA concentration increased the expression of these AA transporters in two-dimensional (2D) cultured cells. The paracellular AA flux except for Ser, Thr, Tyr, Ala, and Gly was enhanced by CLDN1 silencing. These results suggest that CLDN1 forms a paracellular barrier to some AAs, leading to the elevation of LAT1/3 expression in spheroids. The production of reactive oxygen species in the mitochondria and cytosol was decreased by CLDN1 silencing in spheroids, resulting in downregulation of the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its target antioxidant genes. CLDN1 silencing enhanced the cytotoxicity of anticancer drugs including doxorubicin and cisplatin, which was blocked by sulforaphane, an inducer of Nrf2 signaling. Similarly, the anticancer-induced toxicity was enhanced by Nrf2 silencing. In 2D cultured cells, the anticancer-induced toxicity was attenuated by AA deficiency and sulforaphane. We suggest that CLDN1 forms an AA barrier in spheroids, leading to the augmentation of Nrf2-dependent chemoresistance in A549 cells.

Biophysics of claudin proteins in tight junction architecture: Three decades of progress

Tight junctions are cell-cell adhesion complexes that act as gatekeepers of the paracellular space. Formed by several transmembrane proteins, the claudin family performs the primary gate-keeping function. The claudin proteins form charge and size-selective diffusion barriers to maintain homeostasis across endothelial and epithelial tissue. Of the 27 known claudins in mammals, some are known to seal the paracellular space, while others provide selective permeability. The differences in permeability arise due to the varying expression levels of claudins in each tissue. The tight junctions are observed as strands in freeze-fracture electron monographs; however, at the molecular level, tight junction strands form when multiple claudin proteins assemble laterally (cis assembly) within a cell and head-on (trans assembly) with claudins of the adjacent cell in a zipper-like architecture, closing the gap between the neighboring cells. The disruption of tight junctions caused by changing claudin expression levels or mutations can lead to diseases. Therefore, knowledge of the molecular architecture of the tight junctions and how that is tied to tissue-specific function is critical for fighting diseases. Here, we review the current understanding of the tight junctions accrued over the last three decades from experimental and computational biophysics perspectives.

State of the art and upcoming trends in claudin-directed therapies in gastrointestinal malignancies

PURPOSE OF REVIEW

Claudins, components of tight cell junctions in epithelial and endothelial cells, have emerged as a therapeutic target in gastrointestinal (GI) malignancies, particularly claudin 18.2 (CLDN18.2).

RECENT FINDINGS

Zolbetuximab, a chimeric anti-CLDN18.2 monoclonal antibody (mAb), is currently under FDA review and may emerge as the first claudin targeted therapy approved. Phase 3 trials show that zolbetuximab in combination with front-line fluoropyrimidine plus oxaliplatin improves survival in advanced CLDN18.2 positive (≥75% of tumor cells) gastric adenocarcinoma (GAC) patients. Many other therapies (mAbs; CART; bispecific; ADCs) are under investigation.

SUMMARY

CLDN18.2 will be an important target in GAC. Early understanding of how to target CLDN18.2 based on the level of expression (high, moderate, low) will be the key to success in this area. Studying these as separate entities should be considered. Resistance patterns, loss of CLDN18.2 expression, role in the refractory setting, and if any role in localized disease are questions that remain. Other targets for claudin that target claudin six and four are under investigation. Their role in GI malignancies will soon be further clarified.

Gestational Fisetin Exerts Neuroprotection by Regulating Mitochondria-Directed Canonical Wnt Signaling, BBB Integrity, and Apoptosis in Prenatal VPA-Induced Rodent Model of Autism

Embryonic valproic acid (VPA) has been considered a potential risk factor for autism. Majority of studies indicated that targeting autism-associated alterations in VPA-induced autistic model could be promising in defining and designing therapeutics for autism. Numerous investigations in this field investigated the role of canonical Wnt signaling cascade in regulating the pathophysiology of autism. The impaired blood-brain barrier (BBB) permeability and mitochondrial dysfunction are some key implied features of the autistic brain. So, the current study was conducted to target canonical Wnt signaling pathway with a natural polyphenolic modulator cum antioxidant namely fisetin. A single dose of intraperitoneal VPA sodium salt (400 mg/kg) at gestational day 12.5 induced developmental delays, social behaviour impairments (tube dominance test), and anxiety-like behaviour (sucrose preference test) similar to autism. VPA induced mitochondrial damage and over-activated the canonical Wnt signaling which further increased the blood-brain barrier (BBB) disruption, apoptosis, and neuronal damage. Our findings revealed that oral administration of 10 mg/kg gestational fisetin (GD 13-till parturition) improved social and anxiety-like behaviour by modulating the ROS-regulated mitochondrial-canonical Wnt signaling. Moreover, fisetin controls BBB permeability, apoptosis, and neuronal damage in autism model proving its neuroprotective efficacy. Collectively, our findings revealed that fisetin-evoked modulation of the Wnt signaling cascade successfully relieved the associated symptoms of autism along with developmental delays in the model and indicates its potential as a bioceutical against autism.

The Different Gene Expression Profile in the Eutopic and Ectopic Endometrium Sheds New Light on the Endometrial Seed in Endometriosis

The changes in endometrial cells, both in the eutopic endometrium of patients with and without endometriosis and in lesions at ectopic sites, are frequently described and often compared to tumorigenesis. In tumorigenesis, the concept of "seed and soil" is well established. The seed refers to tumor cells with metastatic potential, and the soil is any organ or tissue that provides a suitable environment for the seed to grow. In this systematic review (PRISMA-S), we specifically compared the development of endometriosis with the "seed and soil" hypothesis. To determine changes in the endometrial seed, we re-analyzed the mRNA expression data of the eutopic and ectopic endometrium, paying special attention to the epithelial-mesenchymal transition (EMT). We found that the similarity between eutopic endometrium without and with endometriosis is extremely high (~99.1%). In contrast, the eutopic endometrium of patients with endometriosis has a similarity of only 95.3% with the ectopic endometrium. An analysis of EMT-associated genes revealed only minor differences in the mRNA expression levels of claudin family members without the loss of other cell-cell junctions that are critical for the epithelial phenotype. The array data suggest that the changes in the eutopic endometrium (=seed) are quite subtle at the beginning of the disease and that most of the differences occur after implantation into ectopic locations (=soil).

Molecular landscape of borderline ovarian tumours: A systematic review

Borderline ovarian tumours (BOTs) show intriguing characteristics distinguishing them from other ovarian tumours. The aim of the systematic review was to analyse the spectrum of molecular changes found in BOTs and discuss their significance in the context of the overall therapeutic approach. The systematic review included articles published between 2000 and 2023 in the databases: PubMed, EMBASE, and Cochrane. After a detailed analysis of the available publications, we qualified for the systematic review: 28 publications on proto-oncogenes: BRAF, KRAS, NRAS, ERBB2, and PIK3CA, 20 publications on tumour suppressor genes: BRCA1/2, ARID1A, CHEK2, PTEN, 4 on adhesion molecules: CADM1, 8 on proteins: B-catenin, claudin-1, and 5 on glycoproteins: E-Cadherin. In addition, in the further part of the systematic review, we included eight publications on microsatellite instability and three describing loss of heterozygosity in BOT. Molecular changes found in BOTs can vary on a case-by-case basis, identifying carcinogenic mutations through molecular analysis and developing targeted therapies represent significant advancements in the diagnosis and treatment of ovarian malignancies. Molecular studies have contributed significantly to our understanding of BOT pathogenesis, but substantial research is still required to elucidate the relationship between ovarian neoplasms and extraneous disease, identify accurate prognostic indicators, and develop targeted therapeutic approaches.

Developing theragnostics for Alzheimer's disease: Insights from cancer treatment

The prevalence of Alzheimer's disease (AD) and its associated economic and societal burdens are on the rise, but there are no curative treatments for AD. Interestingly, this neurodegenerative disease shares several biological and pathophysiological features with cancer, including cell-cycle dysregulation, angiogenesis, mitochondrial dysfunction, protein misfolding, and DNA damage. However, the genetic factors contributing to the overlap in biological processes between cancer and AD have not been actively studied. In this review, we discuss the shared biological features of cancer and AD, the molecular targets of anticancer drugs, and therapeutic approaches. First, we outline the common biological features of cancer and AD. Second, we describe several anticancer drugs, their molecular targets, and their effects on AD pathology. Finally, we discuss how protein-protein interactions (PPIs), receptor inhibition, immunotherapy, and gene therapy can be exploited for the cure and management of both cancer and AD. Collectively, this review provides insights for the development of AD theragnostics based on cancer drugs and molecular targets.

Comprehensive landscape of junctional genes and their association with overall survival of patients with lung adenocarcinoma

Objectives

Junctional proteins are involved in tumorigenesis. Therefore, this study aimed to investigate the association between junctional genes and the prognosis of patients with lung adenocarcinoma (LUAD).

Methods

Transcriptome, mutation, and clinical data were retrieved from The Cancer Genome Atlas (TCGA). "Limma" was used to screen differentially expressed genes. Moreover, Kaplan-Meier survival analysis was used to identify junctional genes associated with LUAD prognosis. The junctional gene-related risk score (JGRS) was generated based on multivariate Cox regression analysis. An overall survival (OS) prediction model combining the JGRS and clinicopathological properties was proposed using a nomogram and further validated in the Gene Expression Omnibus (GEO) LUAD cohort.

Results

To our knowledge, this study is the first to demonstrate the correlation between the mRNA levels of 14 junctional genes (CDH15, CDH17, CDH24, CLDN6, CLDN12, CLDN18, CTNND2, DSG2, ITGA2, ITGA8, ITGA11, ITGAL, ITGB4, and PKP3) and clinical outcomes of patients with LUAD. The JGRS was generated based on these 14 genes, and a higher JGRS was associated with older age, higher stage levels, and lower immune scores. Thus, a prognostic prediction nomogram was proposed based on the JGRS. Internal and external validation showed the good performance of the prediction model. Mechanistically, JGRS was associated with cell proliferation and immune regulatory pathways. Mutational analysis revealed that more somatic mutations occurred in the high-JGRS group than in the low-JGRS group.

Conclusion

The association between junctional genes and OS in patients with LUAD demonstrated by our "TCGA filtrating and GEO validating" model revealed a new function of junctional genes.

Diversity of Intercellular Communication Modes: A Cancer Biology Perspective

From the moment a cell is on the path to malignant transformation, its interaction with other cells from the microenvironment becomes altered. The flow of molecular information is at the heart of the cellular and systemic fate in tumors, and various processes participate in conveying key molecular information from or to certain cancer cells. For instance, the loss of tight junction molecules is part of the signal sent to cancer cells so that they are no longer bound to the primary tumors and are thus free to travel and metastasize. Upon the targeting of a single cell by a therapeutic drug, gap junctions are able to communicate death information to by-standing cells. The discovery of the importance of novel modes of cell-cell communication such as different types of extracellular vesicles or tunneling nanotubes is changing the way scientists look at these processes. However, are they all actively involved in different contexts at the same time or are they recruited to fulfill specific tasks? What does the multiplicity of modes mean for the overall progression of the disease? Here, we extend an open invitation to think about the overall significance of these questions, rather than engage in an elusive attempt at a systematic repertory of the mechanisms at play.

Antibody-mediated targeting of Claudins in cancer

Tight junctions (TJs) are large intercellular adhesion complexes that maintain cell polarity in normal epithelia and endothelia. Claudins are critical components of TJs, forming homo- and heteromeric interaction between adjacent cells, which have emerged as key functional modulators of carcinogenesis and metastasis. Numerous epithelial-derived cancers display altered claudin expression patterns, and these aberrantly expressed claudins have been shown to regulate cancer cell proliferation/growth, metabolism, metastasis and cell stemness. Certain claudins can now be used as biomarkers to predict patient prognosis in a variety of solid cancers. Our understanding of the distinct roles played by claudins during the cancer progression has progressed significantly over the last decade and claudins are now being investigated as possible diagnostic markers and therapeutic targets. In this review, we will summarize recent progress in the use of antibody-based or related strategies for targeting claudins in cancer treatment. We first describe pre-clinical studies that have facilitated the development of neutralizing antibodies and antibody-drug-conjugates targeting Claudins (Claudins-1, -3, -4, -6 and 18.2). Next, we summarize clinical trials assessing the efficacy of antibodies targeting Claudin-6 or Claudin-18.2. Finally, emerging strategies for targeting Claudins, including Chimeric Antigen Receptor (CAR)-T cell therapy and Bi-specific T cell engagers (BiTEs), are also discussed.

2-Deoxy-glucose ameliorates the peritoneal mesothelial and endothelial barrier function perturbation occurring due to Peritoneal Dialysis fluids exposure

Peritoneal dialysis (PD) and prolonged exposure to PD fluids (PDF) induce peritoneal membrane (PM) fibrosis and hypervascularity, leading to functional PM degeneration. 2-deoxy-glucose (2-DG) has shown potential as PM antifibrotic by inhibiting hyper-glycolysis induced mesothelial-to-mesenchymal transition (MMT). We investigated whether administration of 2-DG with several PDF affects the permeability of mesothelial and endothelial barrier of the PM. The antifibrotic effect of 2-DG was confirmed by the gel contraction assay with embedded mesothelial (MeT-5A) or endothelial (EA.hy926) cells cultured in Dianeal® 2.5 % (CPDF), BicaVera® 2.3 % (BPDF), Balance® 2.3 % (LPDF) with/without 2-DG addition (0.2 mM), and qPCR for αSMA, CDH2 genes. Moreover, 2-DG effect was tested on the permeability of monolayers of mesothelial and endothelial cells by monitoring the transmembrane resistance (RTM), FITC-dextran (10, 70 kDa) diffusion and mRNA expression levels of CLDN-1 to -5, ZO1, SGLT1, and SGLT2 genes. Contractility of MeT-5A cells in CPDF/2-DG was decreased, accompanied by αSMA (0.17 ± 0.03) and CDH2 (2.92 ± 0.29) gene expression fold changes. Changes in αSMA, CDH2 were found in EA.hy926 cells, though αSMA also decreased under LPDF/2-DG incubation (0.42 ± 0.02). Overall, 2-DG mitigated the PDF-induced alterations in mesothelial and endothelial barrier function as shown by RTM, dextran transport and expression levels of the CLDN-1 to -5, ZO1, and SGLT2. Thus, supplementation of PDF with 2-DG not only reduces MMT but also improves functional permeability characteristics of the PM mesothelial and endothelial barrier.

Plasma-activated medium ameliorates the chemoresistance of human lung adenocarcinoma cells mediated via downregulation of claudin-2 expression

Plasma-activated medium (PAM) has various biological activities including anticancer and antimicrobial. However, the effect on chemoresistance in cancer cells has not been clarified in detail. Solid cancer cells form a microenvironment in the body and acquire resistance against anticancer drugs. So far, we reported that claudin-2 (CLDN2), a component of tight junctions, suppresses the anticancer drug-induced cytotoxicity of spheroids that mimic in vivo tumors. Here, we found that the protein level of CLDN2 is downregulated by the sublethal concentration of PAM in human lung adenocarcinoma-derived A549 and PC-3 cells. A cycloheximide pulse-chase assay showed that PAM accelerates the degradation of CLDN2 protein. The PAM-induced reduction of CLDN2 protein was inhibited by a lysosome inhibitor, indicating PAM may enhance the lysosomal degradation of CLDN2. The paracellular permeability to doxorubicin (DXR), an anthracycline antitumor drug, was enhanced by PAM. In the spheroids, the accumulation and toxicity of DXR were enhanced by PAM. In addition, oxidative stress and the expression of nuclear factor erythroid 2-related factor 2, one of the key factors for the acquisition of chemoresistance, were attenuated by PAM. The improvement effect of PAM on chemoresistance was suppressed by the exogenous CLDN2 overexpression. These results indicate that PAM has the ability to downregulate CLDN2 expression and may become an adjuvant drug against lung adenocarcinoma.

Urolithin A conjugation with NSAIDs inhibits its glucuronidation and maintains improvement of Caco-2 monolayers' barrier function

Urolithin A (UA) is an ellagitannin-derived postbiotic metabolite which emerged as a promising health-boosting agent, promoting mitophagy, improving skeletal muscle function, and suppressing the inflammatory response. However, phase II intestinal metabolism severely limits its biopotency, leading to the formation of nonactive glucuronides. To address this constraint, a set of new UA derivatives (UADs), conjugated with nonsteroidal anti-inflammatory drugs (NSAIDs), was synthesized. The bioavailability and inhibitory activity of UADs against UA-glucuronidation were evaluated using differentiated Caco-2 cell monolayers. Parallelly, after the administration of tested substances, the transepithelial electrical resistance (TEER) of the cell monolayers was continuously monitored using the CellZscope device. Though investigated UADs did not penetrate Caco-2 monolayers, all of them significantly suppressed the glucuronidation rate of UA, while conjugates with diclofenac increased the concentration of free molecule on the basolateral side. Moreover, esters of UA with diclofenac (DicloUA) and aspirin (AspUA) positively influenced cell membrane integrity. Western blot analysis revealed that some UADs, including DicloUA, increased the expression of pore-sealing tight junction proteins and decreased the level of pore-forming claudin-2, which may contribute to their beneficial activity towards the barrier function. To provide comprehensive insight into the mechanism of action of DicloUA, Caco-2 cells were subjected to transcriptomic analysis. Next-generation sequencing (NGS) uncovered substantial changes in the expression of genes involved, for instance, in multivesicular body organization and zinc ion homeostasis. The results presented in this study offer new perspectives on the beneficial effects of modifying UA's structure on its intestinal metabolism and bioactivity in vitro.

The tight junction protein claudin 6 is a potential target for patient-individualized treatment in esophageal and gastric adenocarcinoma and is associated with poor prognosis

BACKGROUND

The prognosis of esophageal adenocarcinoma (EAC) and gastric adenocarcinoma (GAC) remains poor, and new therapeutic approaches are urgently needed. Claudin 6 (CLDN6) is an oncofetal antigen that is largely absent in healthy tissues and upregulated in several cancers, making it a promising therapeutical target. In this study, the expression of CLDN6 was assessed in an large Caucasian EAC and GAC cohort.

METHODS

RNA-Seq data from 89 EACs and 371 GACs were obtained from The Cancer Genome Atlas project and EAC/GAC cases were stratified by CLDN6 mRNA expression based on a survival-associated cutoff. For groups with CLDN6 expression above or below this cutoff, differential gene expression analyses were performed using DESeq, and dysregulated biological pathways were identified using the Enrichr tool. Additionally, CLDN6 protein expression was assessed in more than 800 EACs and almost 600 GACs using a CLDN6-specific immunohistochemical antibody (clone 58-4B-2) that is currently used in Phase I/II trials to identify patients with CLDN6-positive tumors (NCT05262530; NCT04503278). The expression of CLDN6 was also correlated with histopathological parameters and overall survival (OS).

RESULTS

EACs and GACs with high CLDN6 mRNA levels displayed an overexpression of pathways regulating the cell cycle, DNA replication, and receptor / extracellular matrix interactions. CLDN6 protein expression was associated with shorter OS in EAC and GAC, both in treatment-naïve subgroups and cohorts receiving neoadjuvant therapy. In multivariate analysis, CLDN6 protein expression was an independent adverse prognostic factor in EAC associated with a shorter OS (HR: 1.75; p = 0.01) and GAC (HR: 2.74; p = 0.028).

CONCLUSIONS

High expression of CLDN6 mRNA is associated with the dysregulation of distinct biological pathways regulating cell growth, proliferation, and cell-matrix interactions. Clinically, the expression of CLDN6 protein is a valuable adverse prognostic marker in EAC and GAC.

Claudin expression in pulmonary adenoid cystic carcinoma and mucoepidermoid carcinoma

Background: Although the expression of tight junction protein claudins (CLDNs) is well known in common histological subtypes of lung cancer, it has not been investigated in rare lung cancers. The aim of our study was to examine the expression of different CLDNs in pulmonary salivary gland tumors. Methods: 35 rare lung cancers including pathologically confirmed 12 adenoid cystic carcinomas (ACCs) and 23 mucoepidermoid carcinomas (MECs) were collected retrospectively. Immunohistochemical (IHC) staining was performed on formalin fixed paraffin embedded (FFPE) tumor tissues, and CLDN1, -2, -3, -4, -5, -7, and -18 protein expressions were analyzed. The levels of immunopositivity were determined with H-score. Certain pathological characteristics of ACC and MEC samples (tumor grade, presence of necrosis, presence of blood vessel infiltration, and degree of lymphoid infiltration) were also analyzed. Results: CLDN overexpression was observed in both tumor types, especially in CLDN2, -7, and -18 IHC. Markedly different patterns of CLDN expression were found for ACC and MEC tumors, especially for CLDN1, -2, -4, and -7, although none of these trends remained significant after correction for multiple testing. Positive correlations between expressions of CLDN2 and -5, CLDN3 and -4, and CLDN5 and -18 were also demonstrated. Tumors of never-smokers presented lower levels of CLDN18 than tumors of current smokers (p-value: 0.003). Conclusion: This is the first study to comprehensively describe the expression of different CLDNs in lung ACC and MEC. Overexpression of certain CLDNs may pave the way for targeted anti-claudin therapy in these rare histological subtypes of lung cancer.

DoxoDB: A Database for the Expression Analysis of Doxorubicin-Induced lncRNA Genes

Cancer and cardiovascular disease are the leading causes of death worldwide. Recent evidence suggests that these two life-threatening diseases share several features in disease progression, such as angiogenesis, fibrosis, and immune responses. This has led to the emergence of a new field called cardio-oncology. Doxorubicin is a chemotherapy drug widely used to treat cancer, such as bladder and breast cancer. However, this drug causes serious side effects, including acute ventricular dysfunction, cardiomyopathy, and heart failure. Based on this evidence, we hypothesize that comparing the expression profiles of cells and tissues treated with doxorubicin may yield new insights into the adverse effects of the drug on cellular activities. To test this hypothesis, we analyzed published RNA sequencing (RNA-seq) data from doxorubicin-treated cells to identify commonly differentially expressed genes, including long non-coding RNAs (lncRNAs) as they are known to be dysregulated in diseased tissues and cells. From our systematic analysis, we identified several doxorubicin-induced genes. To confirm these findings, we treated human cardiac fibroblasts with doxorubicin to record expression changes in the selected doxorubicin-induced genes and performed a loss-of-function experiment of the lncRNA MAP3K4-AS1. To further disseminate the analyzed data, we built the web database DoxoDB.

Downregulation of Claudin5 promotes malignant progression and radioresistance through Beclin1-mediated autophagy in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a highly prevalent and aggressive cancer with poor treatment outcomes. Despite the critical role of tight junction proteins in tumorigenesis, the involvement of Claudin5 in ESCC remains poorly understood. Thus, this study aimed to investigate the role of Claudin5 in ESCC malignant progression and radioresistance, as well as the underlying regulatory mechanisms.

METHODS

The expression of Claudin5 was evaluated in esophageal cancer tissue using both public databases and 123 clinical samples. CCK-8, transwell invasion, wound healing and clonogenic survival assays were used to examine the proliferation, invasion, migration and radiosensitivity of ESCC cells in vitro. Xenograft and animal lung metastasis experiments were conducted to examine the impact of Claudin5 on tumor growth and lung metastasis in vivo. The effect of Claudin5 on autophagy was detected via transmission electron microscopy, western blotting and autophagy flux. Immunohistochemical staining was used to detect Claudin5 expression in ESCC patient samples. The statistical difference was assessed with Student t test or one-way ANOVA. The correlation between Claudin5 expression and radiotherapy response rate was performed by the Chi-square test. The significance of Kaplan-Meier curves was evaluated by the Logrank test.

RESULTS

Claudin5 expression was downregulated in ESCC tissues. Downregulation of Claudin5 promoted ESCC cell proliferation, invasion, and migration both in vitro and in vivo. Downregulation of Claudin5 decreased the radiosensitivity of ESCC cells. Moreover, downregulation of Claudin5 promoted autophagy and the expression of Beclin1. Beclin1 knockdown reversed the effect of Claudin5 downregulation on autophagy induction and the promotion of ESCC cell malignant progression and radioresistance. Additionally, low expression of Claudin5 in ESCC cancer tissues was associated with poor radiotherapy response and prognosis.

CONCLUSIONS

In summary, these findings suggest that downregulation of Claudin5 promotes ESCC malignant progression and radioresistance via Beclin1-autophagy activation and may serve as a promising biomarker for predicting radiotherapy response and patient outcome in ESCC.

Anti-Claudin Treatments in Gastroesophageal Adenocarcinoma: Mainstream and Upcoming Strategies

Claudins (CLDNs) are a multigene family of proteins and the principal components of tight junctions (TJs), which normally mediate cell-cell adhesion and selectively allow the paracellular flux of ions and small molecules between cells. Downregulation of claudin proteins increases the paracellular permeability of nutrients and growth stimuli to malignant cells, which aids the epithelial transition. Claudin 18.2 (CLDN18.2) was identified as a promising target for the treatment of advanced gastroesophageal adenocarcinoma (GEAC), with high levels found in almost 30% of metastatic cases. CLDN18.2 aberrations, enriched in the genomically stable subgroup of GEAC and the diffuse histological subtype, are ideal candidates for monoclonal antibodies and CAR-T cells. Zolbetuximab, a highly specific anti-CLDN18.2 monoclonal antibody, demonstrated efficacy in phase II studies and, more recently, in the phase III SPOTLIGHT trial, with improvements in both PFS and OS with respect to standard chemotherapy. Anti-CLDN18.2 chimeric antigen receptor (CAR)-T cells showed a safety profile with a prevalence of hematologic toxicity in early phase clinical trials. The aim of this review is to present new findings in the treatment of CLDN18.2-positive GEAC, with a particular focus on the monoclonal antibody zolbetuximab and on the use of engineered anti-CLDN18.2 CAR-T cells.

Detection of Increased Expression of Claudin-1 in Triple-Negative Breast Cancer: Analysis and Clinical-Pathological Correlation

Background Triple-negative breast cancer (TNBC) is a highly aggressive disease that lacks therapeutic targets and prognostic biomarkers. Claudin-1 is a well-described tight junction protein with prognostic value in many human cancers. Aims The need for the discovery of biomarkers of TNBC disease was a major reason for this study. Claudin-1 is a tight junction protein that has shown promising results in the prognosis and management of cancer in general. In the breast, claudin-1 expression and significance have shown variable results, especially in TNBC patients. Our study assessed expression of claudin-1 in a group of TNBC patients, and correlated this expression with clinical-pathological parameters, and with the expression of β-catenin. Materials and methods Tissues from a group of 52 TNBC patients were retrieved from the archives of the community hospital. All related information including demographical, pathologic and clinical data were retrieved. Immunohistochemistry assays of a rabbit polyclonal antibody anti-human claudin-1 were applied using the avidin-biotin peroxidase methodology. Results A statistically significant majority of TNBC cases positively expressed claudin-1 (81%, χ2=13.705; p<0.001). Most TNBC cases had grade 2 β-catenin expression (77.5%; p<0.001), and positive expression for claudin-1 correlated with that of β-catenin (χ2= 23.757; p<0.001). Claudin-1 and β-catenin expressions within tumour cells shared several features including absent or weakness of membranous expression, and redistribution of both proteins to the cytoplasm of tumour cells, and in some cases to the nuclei of these cells. Claudin-1 expression also correlates with adverse survival outcomes, where only four of 20 claudin-1-positive patients who received neo-adjuvant chemotherapy (NAC) achieved pathological complete response (pCR). Conclusions The above presents a complex role of claudin-1 in TNBC patients. In this study, claudin-1 expression was associated with poor prognostic features including invasion, metastases and adverse clinical outcomes. Claudin-1 expression in TNBC correlated with the expression of β-catenin, an important oncogene and a major contributor to the epithelial mesenchymal transition (EMT) phenomenon. Overall, the above results may serve as an impetus for further mechanistic studies to assess the exact role of claudin-1 in TNBC and its possible use in the management of this subset of breast cancer.

Immunoexpression of Claudin 4 in Gastric Adenocarcinomas

Disturbance of the intercellular adhesion system represents a basic biomolecular mechanism in gastric carcinogenesis. Claudin 4 is member of a protein family involved in maintaining homeostasis and epithelial integrity. In this study, we analyzed the immunoexpression of Claudin 4 in 58 cases of gastric adenocarcinomas, in relation to the main histopathological parameters of aggressiveness, the reactions obtained being evaluated through the intensity of the reactions and the number of positive cells. Positive membranous reactions of Claudin 4 were observed in all cases, in tumor cells and some stromal elements, but in some high grade gastric adenocarcinomas also cytoplasmic immunostaining was present. Claudin 4 high scores were associated with tubular, tubulopapillary and hepatoid adenocarcinomas, of low grade and in early stages, aspects that suggest the usefulness of the marker in evaluating the aggressiveness of gastric epithelial tumors.