N‑glycosylation and receptor tyrosine kinase signaling affect claudin‑3 levels in colorectal cancer cells

SARS-CoV-2, periodontal pathogens, and host factors: The trinity of oral post-acute sequelae of COVID-19

COVID-19 as a pan-epidemic is waning but there it is imperative to understand virus interaction with oral tissues and oral inflammatory diseases. We review periodontal disease (PD), a common inflammatory oral disease, as a driver of COVID-19 and oral post-acute-sequelae conditions (PASC). Oral PASC identifies with PD, loss of teeth, dysgeusia, xerostomia, sialolitis-sialolith, and mucositis. We contend that PD-associated oral microbial dysbiosis involving higher burden of periodontopathic bacteria provide an optimal microenvironment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These pathogens interact with oral epithelial cells activate molecular or biochemical pathways that promote viral adherence, entry, and persistence in the oral cavity. A repertoire of diverse molecules identifies this relationship including lipids, carbohydrates and enzymes. The S protein of SARS-CoV-2 binds to the ACE2 receptor and is activated by protease activity of host furin or TRMPSS2 that cleave S protein subunits to promote viral entry. However, PD pathogens provide additional enzymatic assistance mimicking furin and augment SARS-CoV-2 adherence by inducing viral entry receptors ACE2/TRMPSS, which are poorly expressed on oral epithelial cells. We discuss the mechanisms involving periodontopathogens and host factors that facilitate SARS-CoV-2 infection and immune resistance resulting in incomplete clearance and risk for 'long-haul' oral health issues characterising PASC. Finally, we suggest potential diagnostic markers and treatment avenues to mitigate oral PASC.

Analyzing aberrant DNA methylation in colorectal cancer uncovered intangible heterogeneity of gene effects in the survival time of patients

Colorectal cancer (CRC) involves epigenetic alterations. Irregular gene-methylation alteration causes and advances CRC tumor growth. Detecting differentially methylated genes (DMGs) in CRC and patient survival time paves the way to early cancer detection and prognosis. However, CRC data including survival times are heterogeneous. Almost all studies tend to ignore the heterogeneity of DMG effects on survival. To this end, we utilized a sparse estimation method in the finite mixture of accelerated failure time (AFT) regression models to capture such heterogeneity. We analyzed a dataset of CRC and normal colon tissues and identified 3406 DMGs. Analysis of overlapped DMGs with several Gene Expression Omnibus datasets led to 917 hypo- and 654 hyper-methylated DMGs. CRC pathways were revealed via gene ontology enrichment. Hub genes were selected based on Protein-Protein-Interaction network including SEMA7A, GATA4, LHX2, SOST, and CTLA4, regulating the Wnt signaling pathway. The relationship between identified DMGs/hub genes and patient survival time uncovered a two-component mixture of AFT regression model. The genes NMNAT2, ZFP42, NPAS2, MYLK3, NUDT13, KIRREL3, and FKBP6 and hub genes SOST, NFATC1, and TLE4 were associated with survival time in the most aggressive form of the disease that can serve as potential diagnostic targets for early CRC detection.

Aberrant protein glycosylation: Implications on diagnosis and Immunotherapy

Glycosylation-mediated post-translational modification is critical for regulating many fundamental processes like cell division, differentiation, immune response, and cell-to-cell interaction. Alterations in the N-linked or O-linked glycosylation pattern of regulatory proteins like transcription factors or cellular receptors lead to many diseases, including cancer. These alterations give rise to micro- and macro-heterogeneity in tumor cells. Here, we review the role of O- and N-linked glycosylation and its regulatory function in autoimmunity and aberrant glycosylation in cancer. The change in cellular glycome could result from a change in the expression of glycosidases or glycosyltransferases like N-acetyl-glucosaminyl transferase V, FUT8, ST6Gal-I, DPAGT1, etc., impact the glycosylation of target proteins leading to transformation. Moreover, the mutations in glycogenes affect glycosylation patterns on immune cells leading to other related manifestations like pro- or anti-inflammatory effects. In recent years, understanding the glycome to cancer indicates that it can be utilized for both diagnosis/prognosis as well as immunotherapy. Studies involving mass spectrometry of proteome, site- and structure-specific glycoproteomics, or transcriptomics/genomics of patient samples and cancer models revealed the importance of glycosylation homeostasis in cancer biology. The development of emerging technologies, such as the lectin microarray, has facilitated research on the structure and function of glycans and glycosylation. Newly developed devices allow for high-throughput, high-speed, and precise research on aberrant glycosylation. This paper also discusses emerging technologies and clinical applications of glycosylation.

Evaluation of the Prognostic Relevance of Differential Claudin Gene Expression Highlights Claudin-4 as Being Suppressed by TGFβ1 Inhibitor in Colorectal Cancer

Background: Claudins (CLDNs) are a family of closely related transmembrane proteins that have been linked to oncogenic transformation and metastasis across a range of cancers, suggesting that they may be valuable diagnostic and/or prognostic biomarkers that can be used to evaluate patient outcomes. However, CLDN expression patterns associated with colorectal cancer (CRC) remain to be defined.

Methods: The mRNA levels of 21 different CLDN family genes were assessed across 20 tumor types using the Oncomine database. Correlations between these genes and patient clinical outcomes, immune cell infiltration, clinicopathological staging, lymph node metastasis, and mutational status were analyzed using the GEPIA, UALCAN, Human Protein Atlas, Tumor Immune Estimation Resource, STRING, Genenetwork, cBioportal, and DAVID databases in an effort to clarify the potential functional roles of different CLDN protein in CRC. Molecular docking analyses were used to probe potential interactions between CLDN4 and TGFβ1. Levels of CLDN4 and CLDN11 mRNA expression in clinical CRC patient samples and in the HT29 and HCT116 cell lines were assessed via qPCR. CLDN4 expression levels in these 2 cell lines were additionally assessed following TGFβ1 inhibitor treatment.

Results: These analyses revealed that COAD and READ tissues exhibited the upregulation of CLDN1, CLDN2, CLDN3, CLDN4, CLDN7, and CLDN12 as well as the downregulation of CLDN5 and CLDN11 relative to control tissues. Higher CLDN11 and CLDN14 expression as well as lower CLDN23 mRNA levels were associated with poorer overall survival (OS) outcomes. Moreover, CLDN2 and CLDN3 or CLDN11 mRNA levels were significantly associated with lymph node metastatic progression in COAD or READ lower in COAD and READ tissues. A positive correlation between the expression of CLDN11 and predicted macrophage, dendritic cell, and CD4+ T cell infiltration was identified in CRC, with CLDN12 expression further being positively correlated with CD4+ T cell infiltration whereas a negative correlation was observed between such infiltration and the expression of CLDN3 and CLDN15. A positive correlation between CLDN1, CLDN16, and neutrophil infiltration was additionally detected, whereas neutrophil levels were negatively correlated with the expression of CLDN3 and CLDN15. Molecular docking suggested that CLDN4 was able to directly bind via hydrogen bond with TGFβ1. Relative to paracancerous tissues, clinical CRC tumor tissue samples exhibited CLDN4 and CLDN11 upregulation and downregulation, respectively. LY364947 was able to suppress the expression of CLDN4 in both the HT29 and HCT116 cell lines.

Conclusion: Together, these results suggest that the expression of different CLDN family genes is closely associated with CRC tumor clinicopathological staging and immune cell infiltration. Moreover, CLDN4 expression is closely associated with TGFβ1 in CRC, suggesting that it and other CLDN family members may represent viable targets for antitumor therapeutic intervention.

C1GALT1 expression predicts a favorable prognosis and suppresses malignant phenotypes via TrkA signaling in neuroblastoma

Neuroblastoma (NB) is a childhood tumor derived from the sympathoadrenal lineage of the neural crest progenitor cells. Core 1 β1,3-galactosyltransferase (C1GALT1) controls the crucial step of GalNAc-type O-glycosylation, and its altered expression affects cancer behaviors. However, the role of C1GALT1 in NB tumors remains unclear. Our data showed that C1GALT1 expression was significantly associated with differentiated tumor histology, correlated with TrkA expression, and predicted good prognosis independently in NB. Downregulation of C1GALT1 promotes malignant behaviors of NB cells in vitro and in vivo. Mechanistic investigation showed that knockdown of C1GALT1 in NB cells increased TrkA pulled down through Vicia villosa agglutinin beads, indicating the modulation of O-glycans on TrkA by C1GALT1, and silencing C1GALT1 suppressed the TrkA expression on the NB cell surface. Overexpression of C1GALT1 increased the protein levels of TrkA and promoted the differentiation of NB cells, whereas knockdown of TrkA inhibited C1GALT1-induced neuronal differentiation. Moreover, the inhibitory effects of migration and invasion in C1GALT1-overexpressing NB cells were blocked by TrkA downregulation. C1GALT1 knockdown enhanced AKT phosphorylation but attenuated ERK phosphorylation, and these properties were consistent in C1GALT1-overexpressing NB cells with TrkA knockdown. Taken together, our data provided the first evidence for the existence of GalNAc-type O-glycans on TrkA and altered O-glycan structures by C1GALT1 can regulate TrkA signaling in NB cells. This study sheds light on the novel prognostic role of C1GALT1 in NB and provides new information of C1GALT1 and TrkA on the pathogenesis of NB.

Abnormal sialylation and fucosylation of saliva glycoproteins: Characteristics of lung cancer-specific biomarkers

Dysregulated surface glycoproteins play an important role in tumor cell proliferation and progression. Abnormal glycosylation of these glycoproteins may activate tumor signal transduction and lead to tumor development. The tumor microenvironment alters its molecular composition, some of which regulate protein glycosylation biosynthesis. The glycosylation of saliva proteins in lung cancer patients is different from healthy controls, in which the glycans of cancer patients are highly sialylated and hyperfucosylated. Most studies have shown that O-glycans from cancer are truncated O-glycans, while N-glycans contain fucoses and sialic acids. Because glycosylation analysis is challenging, there are few reports on how glycosylation of saliva proteins is related to the occurrence or progression of lung cancer. In this review, we discussed glycoenzymes involved in protein glycosylation, their changes in tumor microenvironment, potential tumor biomarkers present in body fluids, and abnormal glycosylation of saliva or lung glycoproteins. We further explored the effect of glycosylation changes on tumor signal transduction, and emphasized the role of receptor tyrosine kinases in tumorigenesis and metastasis.

Effects of 1,2-Dimethylhydrazine on Barrier Properties of Rat Large Intestine and IPEC-J2 Cells

Colon cancer is accompanied by a decrease of epithelial barrier properties, which are determined by tight junction (TJ) proteins between adjacent epithelial cells. The aim of the current study was to analyze the expression of TJ proteins in a rat model of 1,2-dimethylhydrazine (DMH)-induced colorectal cancer, as well as the barrier properties and TJ protein expression of IPEC-J2 cell monolayers after incubation with DMH. Transepithelial electrical resistance and paracellular permeability for sodium fluorescein of IPEC-J2 were examined by an epithelial volt/ohm meter and spectrophotometry. The expression and localization of TJ proteins were analyzed by immunoblotting and immunohistochemistry. In the colonic tumors of rats with DMH-induced carcinogenesis, the expression of claudin-3 and -4 was significantly increased compared to controls. The transepithelial electrical resistance of IPEC-J2 cells increased, while paracellular permeability for sodium fluorescein decreased, accompanied by an increased expression of claudin-4. The increase of claudin-4 in rat colon after chronic DMH exposure was consistent with the acute effect of DMH on IPEC-J2 cells, which may indicate an essential role of this protein in colorectal cancer development.

Target specific tight junction modulators

Intercellular tight junctions represent a formidable barrier against paracellular drug absorption at epithelia (e.g., nasal, intestinal) and the endothelium (e.g., blood-brain barrier). In order to enhance paracellular transport of drugs and increase their bioavailability and organ deposition, active excipients modulating tight junctions have been applied. First-generation of permeation enhancers (PEs) acted by unspecific interactions, while recently developed PEs address specific physiological mechanisms. Such target specific tight junction modulators (TJMs) have the advantage of a defined specific mechanism of action. To date, merely a few of these novel active excipients has entered into clinical trials, as their lack in safety and efficiency in vivo often impedes their commercialisation. A stronger focus on the development of such active excipients would result in an economic and therapeutic improvement of current and future drugs.