NTS/NTR1 co-expression enhances epithelial-to-mesenchymal transition and promotes tumor metastasis by activating the Wnt/β-catenin signaling pathway in hepatocellular carcinoma

Abstract

Neurotensin (NTS) is a neuropeptide distributed in central nervous and digestive systems. In this study, the significant association between ectopic NTS expression and tumor invasion was confirmed in hepatocellular carcinoma (HCC). In primary HCC tissues, the NTS and neurotensin receptor 1 (NTR1) co-expression (NTS+NTR1+) is a poor prognostic factor correlated with aggressive biological behaviors and poor clinical prognosis. Enhanced epithelial-to-mesenchymal transition (EMT) features, including decreased E-cadherin, increased β-catenin translocation and N-cadherin expression, were identified in NTS+NTR1+ HCC tissues. Varied NTS-responsible HCC cell lines were established using NTR1 genetically modified Hep3B and HepG2 cells which were used to elucidate the molecular mechanisms regulating NTS-induced EMT and tumor invasion in vitro. Results revealed that inducing exogenous NTS stimulation and enhancing NTR1 expression promoted tumor invasion rather than proliferation by accelerating EMT in HCC cells. The NTS-induced EMT was correlated with the remarkable increase in Wnt1, Wnt3, Wnt5, Axin, and p-GSK3β expression and was significantly reversed by blocking the NTS signaling via the NTR1 antagonist SR48692 or by inhibiting the activation of the Wnt/β-catenin pathway via specific inhibitors, such as TSW119 and DKK-1. SR48692 also inhibited the metastases of NTR1-overexpressing HCC xenografts in the lungs in vivo. This finding implied that NTS may be an important stimulus to promote HCC invasion and metastasis both in vitro and in vivo, and NTS signaling enhanced the tumor EMT and invasion potentials by activating the canonical Wnt/β-catenin signaling pathway. Therefore, NTS may be a valuable therapeutic target to prevent tumor progression in HCC.

A Novel Positive Feedback Loop Between NTSR1 and Wnt/β-Catenin Contributes to Tumor Growth of Glioblastoma

“…Blocking the NTSR1 signaling by the specific antagonist SR48692 inhibited the activity of Wnt/β-catenin signaling. Consistent with our observation, Ye et al found that NTS-induced epithelial-to-mesenchymal transition (EMT) was correlated with the remarkable increase in Wnt1, Wnt3, Wnt5 expression and p-GSK3β level [9]. Furthermore, NTSR1 expression in hepatocellular carcinoma (HCC) was also positively correlated with the alteration of the Wnt/β-catenin pathway [17].…”

“…2A, inhibition of NTSR1 with SR48692 or NTSR1 knockdown resulted in a significant decrease in the phosphorylation level of NF-κB and MAPK, suggesting the downstream cascades of NTS/NTSR1 signaling. Previously, it has been reported that exogenous NTS stimulation can upregulate the expression of Wnt proteins in liver cancer [9]. To test this hypothesis in glioblastoma, we detected the effects of NTS on the expression of Wnt1, Wnt3a and Wnt5a upon NF-κB and MAPK inhibition.…”

Neurotensin regulation induces overexpression and activation of EGFR in HCC and restores response to erlotinib and sorafenib

“…In our hands, the PLC/PRF5 cells were highly invasive, overexpression of NTSR1 did not markedly change these characteristics. Collectively, these data suggest that the NTS and NTSR1 promote the invasiveness and migration of HCC cells, and corroborate the data previously published for HCC [32] and breast cancer [6].…”

“…This pathway alters many different liver functions, and contributes to hepatocyte transformation by directly or indirectly regulating many genes at the transcription level including NTSR1. Interestingly, a recent study proposed that NTS/NTSR1 signaling enhanced epithelial/mesenchymal transition by activating Wnt/b-catenin signaling [32]. Together the data from these two papers suggest a feed forward regulation of the NTSR1 signaling on abnormal b-catenin signaling.…”

“…In fibrolamellar carcinomas, overexpression of NTS was correlated with advanced stages and chemotherapy response [5,8]. It was recently shown that NTS/NTSR1 stimulated the wnt/b-catenin pathway facilitating the epithelial/mesenchymal transition in HCC [32]. Earlier reports have also shown that the NTSR1 gene is a target for the Tcf/b-catenin complex, leading to abnormal expression of NTSR1 in the early stage of breast and colon cancer [24,30].…”