CLDN3 inhibits cancer aggressiveness via Wnt-EMT signaling and is a potential prognostic biomarker for hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is one of the most common fatal malignancies but the molecular genetic basis of this disease remains unclear. By using genome-wide methylation profiling analysis, we identified CLDN3 as an epigenetically regulated gene in cancer. Here, we investigated its function and clinical relevance in human HCC. CLDN3 downregulation occurred in 87/114 (76.3%) of primary HCCs, where it was correlated significantly with shorter survival of HCC patients (P=0.021). Moreover, multivariate cyclooxygenase regression analysis showed that CLDN3 was an independent prognostic factor for overall survival (P=0.014). Absent expression of CLDN3 was also detected in 67% of HCC cell lines, which was significantly associated with its promoter hypermethylation. Ectopic expression of CLDN3 in HCC cells could inhibit cell motility, cell invasiveness, and tumor formation in nude mice. Mechanistic investigations suggested through downregulation of GSK3B, CTNNB1, SNAI2, and CDH2, CLDN3 could significantly suppress metastasis by inactivating the Wnt/β-catenin-epithelial mesenchymal transition (EMT) axis in HCC cells. Collectively, our findings demonstrated that CLDN3 is an epigenetically silenced metastasis suppressor gene in HCC. A better understanding of the molecular mechanism of CLDN3 in inhibiting liver cancer cell metastasis may lead to a more effective management of HCC patients with the inactivation of CLDN3.

Tight junction proteins in gastrointestinal and liver disease

“…Many studies have shown different expression levels of the individual CLDNs and OCLN and CLDN1 are being investigated as biomarkers for liver disease progression 103 122 147–151. From these studies, it appears that the expression of CLDNs is associated with more severe disease and/or bad prognosis in patients with HCC (table 2): epigenetic silencing of CLDN14 was significantly associated with advanced tumour state and tumour aggressiveness152; CLDN11 downregulation by miR-99 has been associated with metastasis of HCC153; and CLDN3 downregulation has been suggested to promote EMT via Wnt-β-catenin signalling 154. However, more data are needed to decipher the role of these TJ proteins in the pathogenesis of HCC.…”

Claudin proteins, outside-in signaling, and carcinogenesis

“…In this regard, recent studies have demonstrated novel protein-protein interactions involving claudin proteins including with proteins expressed in lateral and basal domains of the cells, and its influence on cellular signaling cascade/s. Moreover, genetic changes in claudin proteins, in vitro and in vivo, are now demonstrated to modulate multitude of cellular functions including cell proliferation, migration, and by altering key signaling processes including the Notch signaling, the Wnt/β-catenin signaling, and JAK/STAT-3 signaling [26, 39, 47, 48]. …”

“…However, these associations are not always linear and highly increased expression of claudin-3 and −4 in prostate and ovarian cancers, in correlation with cancer aggressiveness, is reported [57]. Interestingly, tumor suppressor role of claudins-3 and −4 has been also reported [26, 35]. They affect the E-cadherin expression and suppress β-catenin signaling, increase in vitro cell migration, invasion, and corresponding metastasis in vivo [26, 55, 56].…”

“…Interestingly, tumor suppressor role of claudins-3 and −4 has been also reported [26, 35]. They affect the E-cadherin expression and suppress β-catenin signaling, increase in vitro cell migration, invasion, and corresponding metastasis in vivo [26, 55, 56]. However, downregulation of claudin-3 or claudin-4 in ovarian cancer promotes tumor growth and metastatic behavior in vivo [55].…”

MSX1 inhibits cell migration and invasion through regulating the Wnt/β-catenin pathway in glioblastoma

“…Nuclear β-catenin accumulation in the invasive fronts of primary tumors has been shown to lead to increased tumor metastasis [19,20]. Molecules targeting Wnt/β-catenin signaling can significantly inhibit tumor growth and EMT in many cancer types [21,22]. MSX1 is a homeobox transcription factor that plays important roles in craniofacial [23] and cardiac [24] development.…”