Date Published: January 26, 2017
Publisher: Public Library of Science
Author(s): Mengbin Qin, Jinxiu Zhang, Chunyan Xu, Peng Peng, Lin Tan, Shiquan Liu, Jiean Huang, Javier S. Castresana.
Despite the identification of many signaling pathways involved in colorectal cancer (CRC) tumorigenesis, metastatic CRC still remains one of the major causes of cancer related death. NIK and IKKβ-binding protein (NIBP) is one of the key regulators of the NF-κB signaling pathway, which has been implicated in CRC metastasis. The aim of this study was to investigate the possible role of NIBP in CRC metastasis through its regulation of NF-κΒ and extracellular regulated kinase/c-Janus kinase (ERK/JNK) signaling pathways.
In this study NIBP, phosphorylated (p)-p65, p-ERK1/2, and p-JNK1/2 expression was examined in 130 CRC, and 25 adenoma tissue samples were studied by immunohistochemistry. NIBP shRNA knockdown was performed in HCT116 cells, and NF-κB and ERK/JNK pathway activity was measured after TNF-α stimulation in vitro and in vivo.
We found that NIBP, p-p65, p-ERK1/2, and p-JNK1/2 expression was higher in late stages of CRC compared to early stages or adenomas. Expression of p-p65, p-IκBα, p-IκBβ, p-ERK1/2, and p-JNK1/2 was inhibited in TNF-α stimulated HCT116 cells following NIBP knockdown. Nevertheless, p-ERK1/2 expression in un-transfected and NIBP knockdown HCT116 cells remained the same in the absence of TNF-α stimulation. Furthermore, cell motility and invasion were reduced in HCT116 cells following NIBP knockdown even after TNF-α treatment. Finally, primary tumor weight and liver metastasis were reduced in nude mice with orthotopically transplanted NIBP knockdown of HCT116 cells.
In conclusion, we demonstrated that NIBP knockdown reduces colorectal cancer metastasis through down-regulation of canonical NF-κΒ signaling and suppression of ERK and JNK signaling.
Colorectal cancer (CRC) is one of the most common types of cancer with over 130,000 newly diagnosed cases in the United States annually. The treatment options for metastatic colorectal cancer (mCRC) are limited, making mCRC a significant clinical challenge. Many signaling pathways and molecules involved in the development and progression of CRC have been identified; however, which molecules are specifically involved in regulating metastasis still remain to be clarified. Therefore, research examining the molecular processes that govern CRC metastasis may provide new targets for the treatment of mCRC.
Colorectal cancer is a major public health issue with regards to malignant diseases. Despite the current knowledge about the molecular pathology of CRC, the 5-year relative survival rate of patients, especially those in late stage mCRC, is still low [16–18]. The role of NF-κB signaling in CRC has been explored in recent years and several mechanisms have been proposed to explain the regulation of persistent NF-κB activation in tumorigenesis. In brief, it has been shown that NF-κB promotes CRC invasiveness by increasing vascular endothelial growth factor (VEGF), intracellular cell adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM), and MMP expression. Jeong et. al., showed that the ERK pathway was activated by reactive oxygen species (ROS) generation, and the NF-κB pathway reduced apoptosis in human colorectal cancer cells. In addition, TNF-α activated both the canonical NF-κB and JNK pathways and increased expression of pro-inflammatory factors. In our previous study we showed that HT-29 cell invasiveness was enhanced via activation of ERK1/2 and MMP-2/9. In this study phosphorylation of p65, ERK1/2, and JNK1/2 was increased in patients with late CRC TNM stages. Furthermore, phosphorylation of p65, IκBα, IκBβ, ERK1/2, and JNK1/2, was increased in HCT116 cells treated with TNF-α. Moreover, cell motility and invasion properties were enhanced in TNF-α treated HCT116. Based on these findings, it can be concluded that both the canonical NF-κB and the ERK and JNK pathways increase with CRC progression and play important roles in cancer metastasis. This is not surprising since, in addition to the known activation of NF-κB signaling, activation of the ERK and JNK mediated pathways has also been reported in the pathogenesis, progression, and oncogenic behavior of human colorectal cancer[18, 19].