Emerging roles of transmembrane-type tight junction proteins in cancers.

Tight junctions (TJs) are the most apical components of the cell-cell adhesion machinery in epithelial and endothelial cells and they play essential roles in homeostasis. Recent studies have revealed that aberrant expression of tight junction proteins (TJPs) is frequently observed in various type of cancers. Here we review cancer-associated aberrant expression of TJPs with focus on transmembrane-type TJPs including claudins, junctional adhesion molecule-A (JAM-A), and occludin. Some transmembrane-type TJPs are upregulated at the early neoplastic stage and their expression persists during dedifferentiation. Aberrant expression of TJPs contributes to proliferation, invasion, and dysregulated signaling of cancer cells. In addition to an increase in their expression level, their localization is altered from a TJ-restricted pattern to distribution throughout the whole cell membrane, making them suitable as therapeutic targets. Extracellular domains of transmembrane-type TJPs can be approached by target drugs not only from the lumen side (apical side) but also from the extracellular matrix side (basal side), including blood vessels. Aberrantly expressed TJPs are potential useful diagnostic markers as well as therapeutic targets for cancers.

Cholangio-venous reflux of biliary contents through paracellular pathways between hepatocytes in patients with acute cholangitis.

BACKGROUND: We re-analyzed data on cholangio-venous reflux from a clinical study conducted prospectively on 22 patients in 1974. METHOD: Direct cholangiography was performed with indocyanine green (ICG) mixed into UrographinR under monitoring of intrabiliary pressure, and the participants were allocated to three groups according to whether ICG leakage into the blood, signs of infection, or both, were present. RESULTS: The intrabiliary pressure of six patients negative for both ICG leakage and signs of infection was approximately 19.5 (median, [range 18-22]) cmH2 O. In contrast, for the five patients positive for ICG leakage but negative for signs of infection, the intrabiliary pressure was higher (median 32.0 [range 27-41) cmH2 O]. The 11 patients positive for both ICG leakage and signs of infection had the highest intrabiliary pressure (median 48.0 [range 33-77] cmH2 O). Our analyses revealed that, as the intrabiliary pressure increased, the status of ICG leakage and signs of infection appeared in a stepwise fashion. CONCLUSION: Our findings suggest that the tight junctions sealing the bile canaliculi deteriorated with increasing intrabiliary pressure, resulting in reflux of the biliary contents into the vascular system via paracellular pathways between hepatocytes.

Aldolase A promotes epithelial-mesenchymal transition to increase malignant potentials of cervical adenocarcinoma.

Recent studies have revealed that metabolic reprogramming is closely associated with epithelial-mesenchymal transition (EMT) during cancer progression. Aldolase A (ALDOA) is a key glycolytic enzyme that is highly expressed in several types of cancer. In this study, we found that ALDOA is highly expressed in uterine cervical adenocarcinoma and that high ALDOA expression promotes EMT to increase malignant potentials, such as metastasis and invasiveness, in cervical adenocarcinoma cells. In human surgical specimens, ALDOA was highly expressed in cervical adenocarcinoma and high ALDOA expression was correlated with lymph node metastasis, lymphovascular infiltration, and short overall survival. Suppression of ALDOA expression significantly reduced cell growth, migration, and invasiveness of cervical cancer cells. Aldolase A expression was partially regulated by hypoxia-inducible factor-1α (HIF-1α). Shotgun proteome analysis revealed that cell-cell adhesion-related proteins were significantly increased in ALDOA-overexpressing cells. Interestingly, overexpression of ALDOA caused severe morphological changes, including a cuboidal-to-spindle shape shift and reduced microvilli formation, coincident with modulation of the expression of typical EMT-related proteins. Overexpression of ALDOA increased migration and invasion in vitro. Furthermore, overexpression of ALDOA induced HIF-1α, suggesting a positive feedback loop between ALDOA and HIF-1α. In conclusion, ALDOA is overexpressed in cervical adenocarcinoma and contributes to malignant potentials of tumor cells through modulation of HIF-1α signaling. The feedback loop between ALDOA and HIF-1α could become a therapeutic target to improve the prognosis of this malignancy.

Elevated expression of G protein-coupled receptor 30 (GPR30) is associated with poor prognosis in patients with uterine cervical adenocarcinoma.

Uterine cervical adenocarcinoma has a worse prognosis than that of squamous cell carcinoma and useful diagnostic and prognostic markers are needed. Estrogen is one of the key regulators of several cancers, however, the estrogen signaling has not been focused on in cervical adenocarcinoma. Here, we shows expression profile of classical estrogen receptor (ER) and a novel membrane type estrogen receptor, G protein-coupled receptor 30 (GPR30), in surgical specimens (n=53). GPR30 was strongly expressed on the cell membrane and in the cytoplasm in adenocarcinoma in situ (AIS) and adenocarcinoma, and its expression was especially strong at the invasion front in most of the cases of GPR30-positive adenocarcinoma. Nuclear staining of ER was strong in non-neoplastic glands, whereas it was almost absent in most of the AIS and adenocarcinoma cases. There was a weak but statistically significant negative correlation between immunoreactivity of GPR30 and that of ER in cervical AIS and adenocarcinoma lesions (Spearman's correlation, r=-0.324, p=0.017). ROC curve analysis revealed that immunoreactivity of GPR30 successfully distinguished neoplasms from non-neoplastic glands with high specificity (100%) and sensitivity (75.5%). GPR30 positivity was significantly correlated with histological type (p=0.009), tumor diameter (p=0.003), tumor size (p<0.001), lymphovascular infiltration (p=0.005) and UICC stage (p<0.001). ER expression was correlated only with tumor factor (p=0.047). GPR30-high patients had poor prognosis with a significantly shorter overall survival (OS) period (p=0.0309). GPR30 expression is a potential diagnostic and prognostic marker.

Cell adhesion signals regulate the nuclear receptor activity.

Cell adhesion is essential for proper tissue architecture and function in multicellular organisms. Cell adhesion molecules not only maintain tissue integrity but also possess signaling properties that contribute to diverse cellular events such as cell growth, survival, differentiation, polarity, and migration; however, the underlying molecular basis remains poorly defined. Here we identify that the cell adhesion signal initiated by the tight-junction protein claudin-6 (CLDN6) regulates nuclear receptor activity. We show that CLDN6 recruits and activates Src-family kinases (SFKs) in second extracellular domain-dependent and Y196/200-dependent manners, and SFKs in turn phosphorylate CLDN6 at Y196/200. We demonstrate that the CLDN6/SFK/PI3K/AKT axis targets the AKT phosphorylation sites in the retinoic acid receptor γ (RARγ) and the estrogen receptor α (ERα) and stimulates their activities. Interestingly, these phosphorylation motifs are conserved in 14 of 48 members of human nuclear receptors. We propose that a similar link between diverse cell adhesion and nuclear receptor signalings coordinates a wide variety of physiological and pathological processes.

Identification of Coiled-Coil Domain-Containing Protein 180 and Leucine-Rich Repeat-Containing Protein 4 as Potential Immunohistochemical Markers for Liposarcoma Based on Proteomic Analysis Using Formalin-Fixed, Paraffin-Embedded Tissue.

Recent technical improvements in both mass spectrometry and protein extraction have made it possible to use formalin-fixed, paraffin-embedded (FFPE) tissues for proteome analysis. In this study, comparable proteome analysis of FFPE tissues revealed multiple candidate marker molecules for differentiating atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) from lipoma. A total of 181 unique proteins were identified for ALT/WDL. Of the identified proteins, coiled-coil domain-containing protein 180 (CCDC180) and leucine-rich repeat-containing protein 4 (LRRC4) were studied as candidate markers of ALT/WDL. CCDC180 and LRRC4 immunohistochemistry clearly stained tumor cells of ALT/WDL and dedifferentiated liposarcoma and could differentiate them from lipoma with high accuracy. Cell biological methods were used to further examine the expression of the candidate marker molecules in liposarcoma cells. In liposarcoma cells, knockdown of CCDC180 and LRRC4 inhibited cell proliferation. CCDC180 inhibited cell migration, invasion, and apoptosis resistance in WDL cells. Adipogenic differentiation suppressed the expression of CCDC180 and LRRC4 in WDL cells. These results indicated that LRRC4 and CCDC180 are novel immunohistochemical markers for differentiating ALT/WDLs. Their expression was associated with adipocyte differentiation and contributed to malignant potentials of WDL cells. Proteome analysis using a standard stock of FFPE tissues can reveal novel biomarkers for various diseases, which contributes to the progress of molecular pathology.

Immunoreactivity patterns of tight junction proteins are useful for differential diagnosis of human salivary gland tumors.

The expression pattern of tight junction proteins (TJPs) varies among organs and tumor types. In this study, we examined the immunoreactivity of claudin (CLDN)-1, -4, and -7, and JAM-A in salivary gland tumors (SGTs) by histological types and cell types to estimate their usefulness as differential diagnostic markers. Immunoreactivity of CLDN1 was higher in ductal epithelium cells of SGTs than in non-tumor tissues. Conversely, immunoreactivity of CLDN1 was significantly decreased in basal/myoepithelium cells of SGTs compared with that in non-tumor tissues. There was no significant difference between the immunoreactivity of CLDN1 in benign tumors and that in malignant tumors. Immunoreactivity of CLDN4, CLDN7, and JAM-A in ductal epithelium cells was higher in many SGTs than in non-tumor tissues. There was a difference depending on the histological type of SGT in immunoreactivity of CLDN4, CLDN7, and JAM-A in basaloid/myoepithelial cells. It was possible to classify SGTs by a hierarchical clustering using immunoreactivity of TJPs. The results suggest that an immunohistochemical marker panel including these TJPs may be useful for differential diagnosis of SGTs and that CLDN1 is associated with tumorigenesis of SGTs.

Estrogen/GPR30 Signaling Contributes to the Malignant Potentials of ER-Negative Cervical Adenocarcinoma via Regulation of Claudin-1 Expression.

Cervical adenocarcinomas are believed to lose estrogen response on the basis of no expression of a nuclear estrogen receptor such as ERα in clinical pathology. Here, we demonstrated that cervical adenocarcinoma cells respond to a physiological concentration of estrogen to upregulate claudin-1, a cell surface molecule highly expressed in cervical adenocarcinomas. Knockout of claudin-1 induced apoptosis and significantly inhibited proliferation, migration, and invasion of cervical adenocarcinoma cells and tumorigenicity in vivo. Importantly, all of the cervical adenocarcinoma cell lines examined expressed a membrane-bound type estrogen receptor, G protein-coupled receptor 30 (GPR30/GPER1), but not ERα. Estrogen-dependent induction of claudin-1 expression was mediated by GPR30 via ERK and/or Akt signaling. In surgical specimens, there was a positive correlation between claudin-1 expression and GPR30 expression. Double high expression of claudin-1 and GPR30 predicts poor prognosis in patients with cervical adenocarcinomas. Mechanism-based targeting of estrogen/GPR30 signaling and claudin-1 may be effective for cervical adenocarcinoma therapy.

Cytotoxicity of Clostridium perfringens enterotoxin depends on the conditions of claudin-4 in ovarian carcinoma cells.

Currently, Clostridium perfringens enterotoxin (CPE) is being investigated as an anti-cancer drug for tumors expressing the tight junction (TJ) transmembrane proteins claudin-3 and/or claudin-4. However, the optimal conditions for CPE cytotoxicity are still unclear. Our objectives were to determine the optimal conditions for CPE as an anti-cancer drug for treating ovarian cancer in vitro and in vivo. In our experiments, cells at low culture density showed higher sensitivity to CPE, suggesting that claudins at TJs were poorly accessible to CPE compared with those at the edge of cell colonies. Ovarian cancer cells cultured under calcium-depleted pretreatment conditions to disrupt TJs and to knock-down TJ proteins and E-cadherin production altered CPE cytotoxicity, which was mainly dependent on claudin-4 expression. These results suggest that the condition of claudin-4 at the cell surface is important for CPE cytotoxicity. Our in vivo experiments showed that a high dose of CPE is required for the effective treatment of peritoneal dissemination of ovarian cancer cells. Here, we suggest that the accessibility of CPE to claudins is important for its cytotoxicity and depends on the conditions of claudin-4 in vitro. In addition, E-cadherin expression in ovarian cancer cells affects the efficiency of CPE in vivo.

Retinoic acid-metabolizing enzyme cytochrome P450 26A1 promotes skin carcinogenesis induced by 7,12-dimethylbenz[a]anthracene.

Elevated expression of the retinoic acid-metabolizing enzyme cytochrome P450 26A1 (CYP26A1) has been demonstrated to have an oncogenic function in carcinogenesis. In order to address the oncogenic capacity of CYP26A1 in vivo, transgenic mice that ubiquitously overexpressed CYP26A1 driven by the cytomegalovirus promoter were generated in the present study. Since the growth of these animals was normal for ≤15 months and they presented no evident abnormalities, a two-stage skin carcinogenesis analysis was performed. In the CYP26A1 transgenic mice, papilloma formation was observed within 7 weeks after administration of the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Development of papillomas in these animals was significantly accelerated when compared with that observed in the control mice following treatment with DMBA in combination with the chemical tumor promoter 12-O-tetradecanoylphorbol-13-acetate. In addition, constitutive expression of CYP26A1 increased the susceptibility of these mice to the generation of squamous cell carcinomas caused by treatment with the carcinogen alone. It is thus concluded that CYP26A1 expression promotes skin carcinogenesis initiated by DMBA.

Occludin induces microvillus formation via phosphorylation of ezrin in a mouse hepatic cell line.

Apical and basolateral cell membranes are separated by tight junctions (TJs). Microvilli are limited to the apical cell membrane. TJs and microvilli are the landmarks for epithelial cell polarity. However, the direct relationship between TJ proteins (TJPs) and the components of microvilli remains unclear. In this study, we investigated whether occludin, which is considered to be a functional TJP, is involved in microvillus formation. In occludin knockout mouse hepatic cells (OcKO cells), the microvillus density was less than that in wild-type (WT) cells and the length of microvilli was short. Immunoreactivity of ezrin was decreased in OcKO cells compared with that in WT cells. Although there was no change in the expression level of ezrin, phosphorylation of ezrin was decreased in OcKO cells. The microvillus density and the length of microvilli were increased in OcKO cells by transfection of full-length mouse occludin and COOH-terminal domains of occludin. These results suggested that occludin induced microvillus formation via phosphorylation of ezrin and that the COOH-terminal domain of occludin, which is localized in non-TJ areas, might be able to induce microvilli formation. Our results provide new insights into the function of occludin.

Epigenetic silencing of SMOC1 in traditional serrated adenoma and colorectal cancer.

Colorectal sessile serrated adenoma/polyps (SSA/Ps) are well-known precursors of colorectal cancer (CRC) characterized by BRAF mutation and microsatellite instability. By contrast, the molecular characteristics of traditional serrated adenoma (TSAs) are not fully understood. We analyzed genome-wide DNA methylation in TSAs having both protruding and flat components. We identified 11 genes, including SMOC1, methylation of which progressively increased during the development of TSAs. SMOC1 was prevalently methylated in TSAs, but was rarely methylated in SSA/Ps (p < 0.001). RT-PCR and immunohistochemistry revealed that SMOC1 was expressed in normal colon and SSA/Ps, but its expression was decreased in TSAs. Ectopic expression of SMOC1 suppressed proliferation, colony formation and in vivo tumor formation by CRC cells. Analysis of colorectal lesions (n = 847) revealed that SMOC1 is frequently methylated in TSAs, high-grade adenomas and CRCs. Among these, SMOC1 methylation was strongly associated with KRAS mutation and CpG island methylator phenotype (CIMP)-low. These results demonstrate that epigenetic silencing of SMOC1 is associated with TSA development but is rarely observed in SSA/Ps. SMOC1 expression could thus be a diagnostic marker of serrated lesions, and SMOC1 methylation could play a role in neoplastic pathways in TSAs and conventional adenomas.

Prognostic significance of the co-expression of EGFR and HER2 in adenocarcinoma of the uterine cervix.

Prognostic factors and therapeutic targets are needed for the patients with cervical adenocarcinoma because they have a poor prognosis. Recently, co-expression of multiple receptor tyrosine kinases (RTKs) has been found to be associated with aggressive biological behavior and poor prognosis of several types of malignancy. To evaluate the significance of the expression of multiple RTKs in uterine cervical cancers, we examined the expression profile of RTKs (EGFR, HER2 and c-Met) and the correlation of their expression with clinicopathological features and prognosis of patients with cervical adenocarcinomas. AIS and adenocarcinoma showed strong expression of a single RTK (EGFR, HER2 or c-Met) on the cell membrane in 41 (77.4%) of 53 cases. Twenty (46%) of the 43 adenocarcinoma cases were positive for double or triple RTKs (P = 0.034). Positivity for EGFR and double positivity for EGFR and HER2 (EGFR+/HER2+/c-Met+ and EGFR+/HER2+/c-Met-) were significantly correlated with lymph node metastasis (P = 0.010 for single and P = 0.013 for double) and UICC stage (P = 0.021 for single and P = 0.007 for double). Positivity for HER2 was significantly correlated with tumor size (P = 0.029). Relapse-free survival (RFS) was significantly shorter in patients who were double positive for EGFR and HER2. Our results suggest that EGFR and HER2 are potential therapeutic targets and that their co-expression is a prognostic factor for cervical adenocarcinoma.

Elevated expression of JAM-A promotes neoplastic properties of lung adenocarcinoma.

A cell-cell adhesion protein, junctional adhesion molecule-A (JAM-A), has been shown to be involved in neoplasia of various organs. However, the fundamental role of JAM-A in tumorigenesis is still under debate because dysregulated expression of this protein has distinct effects, playing opposite roles in carcinogenesis depending on the target tissues. In the present study, we found elevated levels of JAM-A expression in lung adenocarcinoma and its preinvasive lesions, including atypical adenomatous hyperplasia and adenocarcinoma in situ by immunohistochemistry. We also showed that suppression of constitutive JAM-A expression conferred target cells with increased susceptibility to apoptosis in lung adenocarcinoma cells. Consequently, inhibition of JAM-A activity decreased colony-forming capability in vitro and tumorigenicity in vivo. The transformed phenotype following suppression of JAM-A expression was sufficient to reduce motile and invasive capacities. Importantly, knockout of JAM-A had striking effects on cells. Our observations suggest that increased expression of JAM-A promotes neoplasia of lung adenocarcinoma. In addition, an anti-JAM-A antibody efficiently reduced cell proliferation and provoked apoptosis, indicating the potential feasibility of JAM-A-inhibitory cancer therapy.

Claudin-18 coupled with EGFR/ERK signaling contributes to the malignant potentials of bile duct cancer.

Our recent work revealed that elevated expression of claudin-18 is involved in bile duct neoplasia. In the present study, we found that wound generation of a cell sheet de novo induced claudin-18 expression in its leading edge, coincident with high mitotic activity. We also found that the suppression of claudin-18 expression significantly reduced cell growth and invasiveness of bile duct cancer cell lines and tumorigenicity in vivo. In addition, an antibody specific to an extracellular loop of claudin-18 showed similar effects on the cells such as cell proliferation. Interestingly, treatment with epidermal growth factor (EGF) and overexpression of RAS oncogene induced claudin-18 expression by activation of extracellular signal-related kinase (ERK)1/2. Furthermore, enhanced claudin-18 expression activated ERK1/2. These findings provide evidence for an oncogenic property of claudin-18 in bile duct carcinoma cells via modulation of EGFR/ERK signaling, indicating that claudin-18 is a possible therapeutic target for this malignancy.

Surfactant Protein A Inhibits Growth and Adherence of Uropathogenic Escherichia coli To Protect the Bladder from Infection.

Surfactant protein A (SP-A) is a multifunctional host defense collectin that was first identified as a component of pulmonary surfactant. Although SP-A is also expressed in various tissues, including the urinary tract, its innate immune functions in nonpulmonary tissues are poorly understood. In this study, we demonstrated that adherence of uropathogenic Escherichia coli (UPEC) to the bladder was enhanced in SP-A-deficient mice, which suggests that SP-A plays an important role in innate immunity against UPEC. To understand the innate immune functions of SP-A in detail, we performed in vitro experiments. SP-A directly bound to UPEC in a Ca2+-dependent manner, but it did not agglutinate UPEC. Our results suggest that a bouquet-like arrangement seems unsuitable to agglutinate UPEC. Meanwhile, SP-A inhibited growth of UPEC in human urine. Furthermore, the binding of SP-A to UPEC decreased the adherence of bacteria to urothelial cells. These results indicate that direct action of SP-A on UPEC is important in host defense against UPEC. Additionally, adhesion of UPEC to urothelial cells was decreased when the cells were preincubated with SP-A. Adhesion of UPEC to urothelial cells is achieved via interaction between FimH, an adhesin located at bacterial pili, and uroplakin Ia, a glycoprotein expressed on the urothelium. SP-A directly bound to uroplakin Ia and competed with FimH for uroplakin Ia binding. These results lead us to conclude that SP-A plays important roles in host defense against UPEC.

Surfactant protein A (SP-A) and SP-A-derived peptide attenuate chemotaxis of mast cells induced by human ß-defensin 3.

Human ß-defensin 3 (hBD3) is known to be involved in mast cell activation. However, molecular mechanisms underlying the regulation of hBD3-induced mast cell activation have been poorly understood. We previously reported that SP-A and SP-A-derived peptide 01 (SAP01) regulate the function of hBD3. In this study, we focused on the effects of SP-A and SAP01 on the activation of mast cells induced by hBD3. SAP01 directly bound to hBD3. Mast cell-mediated vascular permeability and edema in hBD3 administered rat ears were decreased when injected with SP-A or SAP01. Compatible with the results in rat ear model, both SP-A and SAP01 inhibited hBD3-induced chemotaxis of mast cells in vitro. Direct interaction between SP-A or SAP01 and hBD3 seemed to be responsible for the inhibitory effects on chemotaxis. Furthermore, SAP01 attenuated hBD3-induced accumulation of mast cells and eosinophils in tracheas of the OVA-sensitized inflammatory model. SP-A might contribute to the regulation of inflammatory responses mediated by mast cells during infection.

Cytological findings of langerhans cell sarcoma in a case of quintuple cancer.

Langerhans cell sarcoma (LCS) and quintuple cancers are extremely rare. In this report, a case of quintuple cancers including LCS was described. An 80-year-old man had squamous cell carcinoma of the nasal skin, colon and rectum adenocarcinomas, and T-cell/histiocyte-rich large B-cell lymphoma. As swelling of multiple submental lymph nodes was observed, fine-needle aspiration was carried out. Many large cells with high-grade nuclear atypia and abundant cytoplasm were observed. Lymphocytes and eosinophils were observed in the background. Although a malignant tumor was suspected, a definite diagnosis could not be made. In a biopsy sample, the tumor cells were positive for vimentin, CD68, S-100, CD1a, and CD163 and negative for epithelial, lymphocyte, and melanoma markers in immunohistochemistry. A diagnosis of LCS was made from the immunohistochemical findings and high mitotic rate with atypical forms. The patient died about 2 months after the first medical examination. Metastasis of LCS was confirmed in many organs by autopsy. LCS has a poor prognosis. In cases with the above-described cytological findings, LCS should be added to the list of differential diagnosis. The cytological findings presented here may be useful for determining appropriate clinical management such as staging of the disease and follow-up of the neoplasm. Diagn. Cytopathol. 2017;45:441-445. © 2017 The Authors Diagnostic Cytopathology Published by Wiley Periodicals, Inc.

Claudins in cancer: bench to bedside.

The claudin family, in mammals, encoded by at least 27 members of a single ancestral gene, CLDN, is the main constituent as integral membrane proteins of tight junctions. It has been shown that the expression levels of claudins are often decreased or that their expressions are absent in human neoplasias. These findings are consistent with the well-accepted concept that carcinogenesis is accompanied by the disruption or loss of functional tight junctions. In contrast, accumulating data have showed elevated or aberrant expression of claudins in various cancers, indicating specific roles of claudins in tumorigenesis. Importantly, dysregulated claudins play an oncogenic role or conversely have a tumor-suppressive effect depending on target tissues or cell types, and thus, they contribute to tumor development and progression. Although tight junctions are intercellular structures in epithelial cells, specific roles of claudins in cancer are supported by the evidence that TJs are not simple static constituents for establishing cell adhesion structures but are also cell signaling components that have functions in receiving environmental cues and transmitting signals inside cells. Since the expression profile of claudins is associated with patients' outcome and prognosis in several cancer types, an understanding of the expression pattern and subcellular localization of claudins in various pathologies will lead to the establishment of claudins as useful biomarkers for the detection and diagnosis of cancers.

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.