Loss of desmoglein-2 promotes gallbladder carcinoma progression and resistance to EGFR-targeted therapy through Src kinase activation

Serine/threonine-protein kinase D2-mediated phosphorylation of DSG2 threonine 730 promotes esophageal squamous cell carcinoma progression

Desmoglein-2 (DSG2) is a transmembrane glycoprotein belonging to the desmosomal cadherin family, which mediates cell-cell junctions; regulates cell proliferation, migration, and invasion; and promotes tumor development and metastasis. We previously showed serum DSG2 to be a potential biomarker for the diagnosis of esophageal squamous cell carcinoma (ESCC), although the significance and underlying molecular mechanisms were not identified. Here, we found that DSG2 was increased in ESCC tissues compared with adjacent tissues. In addition, we demonstrated that DSG2 promoted ESCC cell migration and invasion. Furthermore, using interactome analysis, we identified serine/threonine-protein kinase D2 (PRKD2) as a novel DSG2 kinase that mediates the phosphorylation of DSG2 at threonine 730 (T730). Functionally, DSG2 promoted ESCC cell migration and invasion dependent on DSG2-T730 phosphorylation. Mechanistically, DSG2 T730 phosphorylation activated EGFR, Src, AKT, and ERK signaling pathways. In addition, DSG2 and PRKD2 were positively correlated with each other, and the overall survival time of ESCC patients with high DSG2 and PRKD2 was shorter than that of patients with low DSG2 and PRKD2 levels. In summary, PRKD2 is a novel DSG2 kinase, and PRKD2-mediated DSG2 T730 phosphorylation promotes ESCC progression. These findings may facilitate the development of future therapeutic agents that target DSG2 and DSG2 phosphorylation. © 2024 The Pathological Society of Great Britain and Ireland.

Desmoglein 2 and desmocollin 2 depletions promote malignancy through distinct mechanisms in triple-negative and luminal breast cancer

BACKGROUND

Aberrant expressions of desmoglein 2 (Dsg2) and desmocollin 2(Dsc2), the two most widely distributed desmosomal cadherins, have been found to play various roles in cancer in a context-dependent manner. Their specific roles on breast cancer (BC) and the potential mechanisms remain unclear.

METHODS

The expressions of Dsg2 and Dsc2 in human BC tissues and cell lines were assessed by using bioinformatics analysis, immunohistochemistry and western blotting assays. Wound-healing and Transwell assays were performed to evaluate the cells' migration and invasion abilities. Plate colony-forming and MTT assays were used to examine the cells' capacity of proliferation. Mechanically, Dsg2 and Dsc2 knockdown-induced malignant behaviors were elucidated using western blotting assay as well as three inhibitors including MK2206 for AKT, PD98059 for ERK, and XAV-939 for β-catenin.

RESULTS

We found reduced expressions of Dsg2 and Dsc2 in human BC tissues and cell lines compared to normal counterparts. Furthermore, shRNA-mediated downregulation of Dsg2 and Dsc2 could significantly enhance cell proliferation, migration and invasion in triple-negative MDA-MB-231 and luminal MCF-7 BC cells. Mechanistically, EGFR activity was decreased but downstream AKT and ERK pathways were both activated maybe through other activated protein tyrosine kinases in shDsg2 and shDsc2 MDA-MB-231 cells since protein tyrosine kinases are key drivers of triple-negative BC survival. Additionally, AKT inhibitor treatment displayed much stronger capacity to abolish shDsg2 and shDsc2 induced progression compared to ERK inhibition, which was due to feedback activation of AKT pathway induced by ERK inhibition. In contrast, all of EGFR, AKT and ERK activities were attenuated, whereas β-catenin was accumulated in shDsg2 and shDsc2 MCF-7 cells. These results indicate that EGFR-targeted therapy is not a good choice for BC patients with low Dsg2 or Dsc2 expression. Comparatively, AKT inhibitors may be more helpful to triple-negative BC patients with low Dsg2 or Dsc2 expression, while therapies targeting β-catenin can be considered for luminal BC patients with low Dsg2 or Dsc2 expression.

CONCLUSION

Our finding demonstrate that single knockdown of Dsg2 or Dsc2 could promote proliferation, motility and invasion in triple-negative MDA-MB-231 and luminal MCF-7 cells. Nevertheless, the underlying mechanisms were cellular context-specific and distinct.

Desmoglein-2 as a cancer modulator: friend or foe?

Desmoglein-2 (DSG2) is a calcium-binding single pass transmembrane glycoprotein and a member of the large cadherin family. Until recently, DSG2 was thought to only function as a cell adhesion protein embedded within desmosome junctions designed to enable cells to better tolerate mechanical stress. However, additional roles for DSG2 outside of desmosomes are continuing to emerge, particularly in cancer. Herein, we review the current literature on DSG2 in cancer and detail its impact on biological functions such as cell adhesion, proliferation, migration, invasion, intracellular signaling, extracellular vesicle release and vasculogenic mimicry. An increased understanding of the diverse repertoire of the biological functions of DSG2 holds promise to exploit this cell surface protein as a potential prognostic biomarker and/or target for better patient outcomes. This review explores the canonical and non-canonical functions of DSG2, as well as the context-dependent impacts of DSG2 in the realm of cancer.

A Novel Gemcitabine-Resistant Gallbladder Cancer Model Provides Insights into Molecular Changes Occurring during Acquired Resistance

Treatment options for advanced gallbladder cancer (GBC) are scarce and usually rely on cytotoxic chemotherapy, but the effectiveness of any regimen is limited and recurrence rates are high. Here, we investigated the molecular mechanisms of acquired resistance in GBC through the development and characterization of two gemcitabine-resistant GBC cell sublines (NOZ GemR and TGBC1 GemR). Morphological changes, cross-resistance, and migratory/invasive capabilities were evaluated. Then, microarray-based transcriptome profiling and quantitative SILAC-based phosphotyrosine proteomic analyses were performed to identify biological processes and signaling pathways dysregulated in gemcitabine-resistant GBC cells. The transcriptome profiling of parental and gemcitabine-resistant cells revealed the dysregulation of protein-coding genes that promote the enrichment of biological processes such as epithelial-to-mesenchymal transition and drug metabolism. On the other hand, the phosphoproteomics analysis of NOZ GemR identified aberrantly dysregulated signaling pathways in resistant cells as well as active kinases, such as ABL1, PDGFRA, and LYN, which could be novel therapeutic targets in GBC. Accordingly, NOZ GemR showed increased sensitivity toward the multikinase inhibitor dasatinib compared to parental cells. Our study describes transcriptome changes and altered signaling pathways occurring in gemcitabine-resistant GBC cells, which greatly expands our understanding of the underlying mechanisms of acquired drug resistance in GBC.

miR-4461 inhibits the progression of Gallbladder carcinoma via regulating EGFR/AKT signaling

Increasing evidence has demonstrated that microRNAs (miRNAs) participated in the tumorigenesis, progression and recurrence of various malignancies including Gallbladder carcinoma (GBC). miR-4461 was reported to work as a tumor suppressor gene in renal cell carcinoma. However, the role of miR-4461 in GBC remains unknown. Herein, we show that miR-4461 is downregulated in gallbladder cancer stem cells (CSCs). Forced miR-4461 expression attenuates the self-renewal, tumorigenicity of gallbladder CSCs, and inhibits proliferation and metastasis of GBC cells. Conversely, miR-4461 knockdown promotes the self-renewal of gallbladder CSCs, and facilities proliferation and metastasis of GBC cells. Mechanistically, miR-4461 inhibits GBC progression via downregulating EGFR/AKT pathway. Special EGFR siRNA or AKT overexpression virus abolishes the discrepancy of self-renewal, tumorigenesis, growth, and metastasis between miR-4461 overexpression GBC cells and their control cells. In conclusion, miR-4461 suppresses GBC cells self-renewal, tumorigenicity, proliferation, and metastasis by inactivating EGFR/AKT signaling, and may therefore prove to be a potential therapeutic target for GBC patients.

Nanoparticle-Based RNAi Therapeutics Targeting Cancer Stem Cells: Update and Prospective

Cancer stem cells (CSCs) are characterized by intrinsic self-renewal and tumorigenic properties, and play important roles in tumor initiation, progression, and resistance to diverse forms of anticancer therapy. Accordingly, targeting signaling pathways that are critical for CSC maintenance and biofunctions, including the Wnt, Notch, Hippo, and Hedgehog signaling cascades, remains a promising therapeutic strategy in multiple cancer types. Furthermore, advances in various cancer omics approaches have largely increased our knowledge of the molecular basis of CSCs, and provided numerous novel targets for anticancer therapy. However, the majority of recently identified targets remain ‘undruggable’ through small-molecule agents, whereas the implications of exogenous RNA interference (RNAi, including siRNA and miRNA) may make it possible to translate our knowledge into therapeutics in a timely manner. With the recent advances of nanomedicine, in vivo delivery of RNAi using elaborate nanoparticles can potently overcome the intrinsic limitations of RNAi alone, as it is rapidly degraded and has unpredictable off-target side effects. Herein, we present an update on the development of RNAi-delivering nanoplatforms in CSC-targeted anticancer therapy and discuss their potential implications in clinical trials.

Deep Proteomic Analysis on Biobanked Paraffine-Archived Melanoma with Prognostic/Predictive Biomarker Read-Out

The discovery of novel protein biomarkers in melanoma is crucial. Our introduction of formalin-fixed paraffin-embedded (FFPE) tumor protocol provides new opportunities to understand the progression of melanoma and open the possibility to screen thousands of FFPE samples deposited in tumor biobanks and available at hospital pathology departments. In our retrospective biobank pilot study, 90 FFPE samples from 77 patients were processed. Protein quantitation was performed by high-resolution mass spectrometry and validated by histopathologic analysis. The global protein expression formed six sample clusters. Proteins such as TRAF6 and ARMC10 were upregulated in clusters with enrichment for shorter survival, and proteins such as AIFI1 were upregulated in clusters with enrichment for longer survival. The cohort's heterogeneity was addressed by comparing primary and metastasis samples, as well comparing clinical stages. Within immunotherapy and targeted therapy subgroups, the upregulation of the VEGFA-VEGFR2 pathway, RNA splicing, increased activity of immune cells, extracellular matrix, and metabolic pathways were positively associated with patient outcome. To summarize, we were able to (i) link global protein expression profiles to survival, and they proved to be an independent prognostic indicator, as well as (ii) identify proteins that are potential predictors of a patient's response to immunotherapy and targeted therapy, suggesting new opportunities for precision medicine developments.

Long Non-Coding RNA Myosin Light Chain Kinase Antisense 1 Plays an Oncogenic Role in Gallbladder Carcinoma by Promoting Chemoresistance and Proliferation

Background

Long non-coding RNAs (lncRNAs) have been reported to play critical roles in human tumours, including gallbladder carcinoma (GBC). However, their biological functions and molecular mechanisms in tumorigenesis and progression remain largely unknown.

Methods

Quantitative polymerase chain reaction (qPCR) was used to verify the expression of lncRNA myosin light chain kinase antisense RNA 1 (MYLK-AS1) in 120 pairs of GBC tissues and paired adjacent non-tumour tissues, as well as in six different GBC cell lines (NOZ, EH-GB1, OCUG-1, GBC-SD, SGC-996 and QBC-939). Cell counting kit 8 was applied to explore cell proliferation and drug sensitivity assays. The target miRNAs (miR) of MYLK-AS1 and downstream target genes were predicted using Starbase 3.0 software and confirmed by double luciferase reporting test. The expression of proteins was assessed using Western blot assay.

Results

Here, we demonstrated that MYLK-AS1 was significantly upregulated and correlated with a poor prognosis and poor clinical characteristics in GBC. Furthermore, the forced expression of MYLK-AS1 significantly promoted GBC cell proliferation and resistance to gemcitabine in vitro. Mechanistically, MYLK-AS1 functioned as an efficient miR-217 sponge, thereby releasing the inhibition of enhancer of zeste 2 polycomb repressive complex 2 (EZH2) subunit expression. MYLK-AS1 promoted GBC cell proliferation and resistance to gemcitabine by upregulating EZH2 expression, and EZH2 was confirmed as a direct target of miR-217.

Discussion

Our results confirmed that the chemoresistant driver MYLK-AS1 might be a promising candidate as a therapeutic target for the treatment of advanced GBC.

Cell adhesion molecules' altered profile in benign and malignant salivary gland tumors. The paradigm of beta4-integrin, desmoglein-2, ICAM-1 and CD44s

Background

Alterations in intercellular and cell-extracellular matrix connections contribute to tumour development. This study investigates the expression of specific cell adhesion molecules (CAMs) in salivary gland tumors (SGTs).

Methods

Formalin–fixed, paraffin– embedded tissue specimens of different types of 34 benign and 31 malignant SGTs and normal salivary glands were studied using Envision/HRP immunohistochemical technique for Desmoglein-2 (Dsg-2), beta4-integrin, CD44s and ICAM-1. Intensity of staining was evaluated in a semi-quantitative manner. Results were analyzed using Kendall’s τ and Spearman’s ρ as correlation criteria.

Results

Dsg-2 in intercellular space, beta4-integrin in cell-basal membrane, and CD44s in both types of contacts were strongly expressed in normal acinar and ductal cells, whereas ICAM-1 was expressed only at the endothelium and sparse stromal cells and monocytes. Strong correlation was found between Dsg-2 expression in adenomas and controls and between adenocarcinomas and controls. In adenomas, a distinct cytoplasmic presence of Dsg-2 was observed in addition to the usual membranous expression, with decreased expression in comparison with normal tissue. In malignant SGTs, Dsg-2 expression was absent. In most SGTs, beta4-integrin was expressed also with a distinct pattern, involving the cytoplasm and the unpolarised membrane, while CD44 was found only on the membrane. Strong correlation between beta4-integrin expression in adenomas and controls was noted, while CD44 expression was found to be correlated significantly between adenocarcinomas and controls (p < 0.001). Regarding ICAM-1, its expression was found increased in adenomas, with non-specific distribution in malignant SGTs and strong correlation between the histological subtypes and controls (p < 0.001).

Conclusion

The different expression profile of CAMs in SGTs could possibly suggest a role on their pathogenesis, representing a model of how neoplastic cells can take advantage of normal tissue architecture and cell-extracellular matrix interactions.