Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein expressed in epithelial tissues. EpCAM forms intercellular, homophilic adhesions, modulates epithelial junctional protein complex formation, and promotes epithelial tissue homeostasis. EpCAM is a target of molecular therapies and plays a prominent role in tumor biology. In this review, we focus on the dynamic regulation of EpCAM expression during epithelial-to-mesenchymal transition (EMT) and the functional implications of EpCAM expression on the regulation of EMT. EpCAM is frequently and highly expressed in epithelial cancers, while silenced in mesenchymal cancers. During EMT, EpCAM expression is downregulated by extracellular signal-regulated kinases (ERK) and EMT transcription factors, as well as by regulated intramembrane proteolysis (RIP). The functional impact of EpCAM expression on tumor biology is frequently dependent on the cancer type and predominant oncogenic signaling pathways, suggesting that the role of EpCAM in tumor biology and EMT is multifunctional. Membrane EpCAM is cleaved in cancers and its intracellular domain (EpICD) is transported into the nucleus and binds β-catenin, FHL2, and LEF1. This stimulates gene transcription that promotes growth, cancer stem cell properties, and EMT. EpCAM is also regulated by epidermal growth factor receptor (EGFR) signaling and the EpCAM ectoderm (EpEX) is an EGFR ligand that affects EMT. EpCAM is expressed on circulating tumor and cancer stem cells undergoing EMT and modulates metastases and cancer treatment responses. Future research exploring EpCAM’s role in EMT may reveal additional therapeutic opportunities.

Introduction: EpCAM is a cell-surface glycoprotein that is overexpressed in the majority of epithelial carcinomas. However, the functional role of EpCAM in regulating cancer invasion remains controversial, and the mechanism(s) underlying EpCAM-mediated regulation of breast cancer invasion remain to be defined. Methods: EpCAM expression was manipulated in breast cancer cell lines using RNA interference and cDNA expression constructs. Recombinant EpCAM was used to rescue EpCAM signaling following specific ablation of EpCAM. Protein and gene expression, invasion, transcription factor activity, and protein phosphorylation were measured using standard molecular biology techniques. Results: In loss-of-function, and gain-of-function experiments we demonstrate that EpCAM expression is associated with increased breast cancer invasion in vitro and in vivo. We demonstrate further that specific ablation of EpCAM expression is associated with decreased activator protein-1 (AP-1) transcription factor activity. Phosphoprotein analyses confirm that specific ablation of EpCAM is associated with decreased phosphorylation of the AP-1 subunit c-Jun. Recombinant soluble extracellular EpCAM (rEpCAM) is able to rescue invasion, AP-1 transcription factor activity, and c-Jun phosphorylation in a dose-dependent fashion. Pharmacologic inhibitors, and constitutively active constructs of the c-Jun N-terminal kinase (JNK) signal transduction pathway, suggest that the impact of EpCAM expression on AP-1 transcription factor activity is mediated through the JNK pathway. In functional rescue experiments, forced expression of c-Jun rescues invasion in breast cancer cells following specific ablation of EpCAM. Conclusions: These data demonstrate for the first time that EpCAM expression can influence the JNK/AP-1 signal transduction pathway, and suggest that modulation of AP-1 transcription factor activity contributes to EpCAM-dependent breast cancer invasion. These data have important implications for the design and application of molecular therapies targeting EpCAM.

Background: EpCAM (Epithelial cell adhesion molecule) is often dysregulated in epithelial cancers. Prior studies implicate EpCAM in the regulation of oncogenic signaling pathways and epithelial-to-mesenchymal transition. It was recently demonstrated that EpCAM contains a thyroglobulin type-1 (TY-1) domain. Multiple proteins with TY-1 domains are known to inhibit cathepsin-L (CTSL), a cysteine protease that promotes tumor cell invasion and metastasis. Analysis of human cancer sequencing studies reveals that somatic EpCAM mutations are present in up to 5.1% of tested tumors. Methods: The Catalogue of Somatic Mutations in Cancer (COSMIC) database was queried to tabulate the position and amino acid changes of cancer associated EpCAM mutations. To determine how EpCAM mutations affect cancer biology we studied C66Y, a damaging TY-1 domain mutation identified in liver cancer, as well as 13 other cancer-associated EpCAM mutations. In vitro and in vivo models were used to determine the effect of wild type (WT) and mutant EpCAM on CTSL activity and invasion. Immunoprecipitation and localization studies tested EpCAM and CTSL protein binding and determined compartmental expression patterns of EpCAM mutants. Results: We demonstrate that WT EpCAM, but not C66Y EpCAM, inhibits CTSL activity in vitro, and the TY-1 domain of EpCAM is responsible for this inhibition. WT EpCAM, but not C66Y EpCAM, inhibits tumor cell invasion in vitro and lung metastases in vivo. In an extended panel of human cancer cell lines, EpCAM expression is inversely correlated with CTSL activity. Previous studies have demonstrated that EpCAM germline mutations can prevent EpCAM from being expressed at the cell surface. We demonstrate that C66Y and multiple other EpCAM cancer-associated mutations prevent surface expression of EpCAM. Cancer-associated mutations that prevent EpCAM cell surface expression abrogate the ability of EpCAM to inhibit CTSL activity and tumor cell invasion. Conclusions: These studies reveal a novel role for EpCAM as a CTSL inhibitor, confirm the functional relevance of multiple cancer-associated EpCAM mutations, and suggest a therapeutic vulnerability in cancers harboring EpCAM mutations.

In the realm of biomedical advancement, extracellular vesicles (EVs) are revolutionizing our capacity to diagnose, monitor, and predict disease progression. However, the comprehensive exploration and clinical application of EVs face significant limitations due to the current isolation techniques. The size exclusion chromatography, commercial precipitation reagents, and ultracentrifugation are frequently employed, necessitating skilled operators and entailing challenges related to consistency, reproducibility, quality, and yields. Notably, the formidable challenge of extracellular vesicle isolation persists when dealing with clinical samples of limited availability. This study addresses these challenges by aiming to devise a rapid, user-friendly, and high-recovery EVs isolation technique tailored for blood samples. The NTI-EXO precipitation method demonstrated a 5-fold increase in the recovery of serum EVs compared to current methodologies. Importantly, we illustrate that a mere two drops of blood (∼100 µL) suffice for the recovery of enriched EVs. The integrity and quality of these isolated EVs were rigorously assessed for the size, purity, and contaminants. This method was validated through the successful isolation of EVs from organ transplant recipients to detect disease-specific exosomal markers, including LKB1, SARS-CoV-2 spike protein, and PD-L1. In conclusion, NTI-EXO method can be used for small clinical samples, thereby advancing discoveries in the EV-centric domain and propelling the frontiers of biomedical research and clinical applications.

EpCAM (epithelial cell adhesion molecule) is a key regulator of epithelial cell–cell adhesion, signal transduction, tissue regeneration, and serves as a stem cell marker. It is frequently overexpressed in epithelial cancers and is linked to tumor progression, survival, and metastasis. However, the functional impact of EpCAM mutations in cancer remains poorly understood. To investigate the role of EpCAM mutations, we performed a comprehensive analysis of cancer cohorts from multiple genomic datasets, identifying novel somatic EpCAM mutations across diverse epithelial cancers. Using bioinformatics tools (SIFT, PolyPhen-2, Mutation Assessor) and molecular modeling, we assessed the potential impact of these mutations. Further, homology modeling and all-atom molecular dynamics (MD) simulations were conducted to evaluate structural changes. From an analysis of 300 studies comprising 300,300 cancer samples, we identified 160 recurrent somatic mutations across epithelial cancers. Of these, seven mutations most frequently associated with lung cancer were further validated through molecular dynamics simulations, evaluation of ERK signaling activity, and assessment of sensitivity to the MEK inhibitor Trametinib. Our findings revealed that cancer-associated mutations, particularly in the TY-1 and RCD regions, induce structural instability in EpCAM, leading to altered functional properties. Patient cohort analyses indicated that EpCAM mutations correlate with reduced survival rates in colon and hepatocellular carcinoma and contribute to early tumor progression in lung cancer. Moreover, introducing these mutations into lung cancer cells enhanced their sensitivity to MEK inhibitors, suggesting a potential therapeutic vulnerability. This study provides novel insights into the structural and functional consequences of EpCAM mutations in cancer, demonstrating their association with reduced survival, tumor progression, and drug sensitivity. These findings highlight EpCAM as a promising therapeutic target in epithelial cancers.

Next generation sequencing of human cancer mutations has identified novel therapeutic targets. Activating Ras oncogene mutations play a central role in oncogenesis, and Ras-driven tumorigenesis upregulates an array of genes and signaling cascades that can transform normal cells into tumor cells. In this study, we investigated the role of altered localization of epithelial cell adhesion molecule (EpCAM) in Ras-expressing cells. Analysis of microarray data demonstrated that Ras expression induced EpCAM expression in normal breast epithelial cells. Fluorescent and confocal microscopy showed that H-Ras mediated transformation also promoted epithelial-to-mesenchymal transition (EMT) together with EpCAM. To consistently localize EpCAM in the cytosol, we generated a cancer-associated EpCAM mutant (EpCAM-L240A) that is retained in the cytosol compartment. Normal MCF-10A cells were transduced with H-Ras together with EpCAM wild-type (WT) or EpCAM-L240A. WT-EpCAM marginally effected invasion, proliferation, and soft agar growth. EpCAM-L240A, however, markedly altered cells and transformed to mesenchymal phenotype. Ras-EpCAM-L240A expression also promoted expression of EMT factors FRA1, ZEB1 with inflammatory cytokines IL-6, IL-8, and IL1. This altered morphology was reversed using MEK-specific inhibitors and to some extent JNK inhibition. Furthermore, these transformed cells were sensitized to apoptosis using paclitaxel and quercetin, but not other therapies. For the first time, we have demonstrated that EpCAM mutations can cooperate with H-Ras and promote EMT. Collectively, our results highlight future therapeutic opportunities in EpCAM and Ras mutated cancers.