Receptor‑interacting serine/threonine‑protein kinase 1 (RIP‑1) is highly expressed in gallbladder cancer, and is very important in promoting tumor proliferation and invasion. The underlying mechanism in this promotion is the RIP‑1‑nuclear factor κ‑B (NF‑κB) and activator protein 1 (AP‑1)‑vascular endothelial growth factor‑C (VEGF‑C) signaling pathways. However, the precise mechanisms by which RIP‑1 regulates VEGF‑C expression are still unknown. The current study aims to clarify the detailed mechanisms by which RIP‑1 upregulates VEGF‑C expression. In the current study, the authors constructed various VEGF‑C promoter deletions, VEGF‑C promoter mutations and RIP‑1 overexpression plasmids, and silenced RIP‑1 with a small interfering RNA. Promoter analysis, an electrophoretic mobility shift assay, a chromatin immunoprecipitation assay was then performed, and an orthotopic transplantation model in nude mice was established by modified methods previously used. The authors also found that the core region for luciferase activity in the VEGF‑C promoter was ‑332 to ‑190 nt, in which there are two overlapping AP‑1 sites and an NF‑κB site. RIP‑1 was demonstrated to activate transcription factors NF‑κB and AP‑1 to combine with the core region and enhance VEGF‑C promoter activity. In conclusion, the current study illustrated the mechanisms by which RIP‑1 regulates VEGF‑C expression, by activating NF‑κB and AP‑1 to combine with the ‑332 to ‑190 nt area of the VEGF‑C promoter. By establishing an orthotopic mouse model of gallbladder cancer tumors, it was further elucidated that RIP‑1 promotes gallbladder cancer metastasis. The findings provide evidence that targeting RIP‑1 may prove to be useful in the treatment of gallbladder cancer.

Vascular endothelial growth factor (VEGF)-C is an important lymphangiogenic factor involved in the lymphangiogenesis of gallbladder carcinoma (GBC) and the lymph node metastasis of the tumor. Tumor necrosis factor (TNF)-α, a key inflammatory cytokine responding to chronic inflammation of GBC, has been reported to stimulate the expression of VEGF-C in some nonneoplastic cells. But whether TNF-α promotes the expression of VEGF-C in GBC has yet to be determined. Therefore, in the present study, the concentration of TNF-α and VEGF-C and the lymphatic vessel density (LVD) in the clinical GBC specimens were analyzed, and a linear correlation was found between the concentration of TNF-α and that of VEGF-C, the lymphatic vessel density (LVD); The transcription and protein level of VEGF-C in NOZ cell line were detected by real-time polymerase chain reaction (PCR) and enzyme linked immunosorbent assay (ELISA), and TNF-α enhanced the expression of VEGF-C in NOZ cell lines in a dose and time-dependent manner. Lymphatic tube formation in vitro was observed in a three-dimensional coculture system consisting of HDLECs and NOZ cell lines, and lymphatic vessels of GBC in nude mice model was detected by immunohistochemistry. TNF-α promoted the tube formation of lymphatic endothelial cells in vitro and the lymphangiogenesis of GBC in nude mice; The nuclear factor (NF)-κB binding site on the VEGF-C promoter was identified using Site-directed mutagenesis, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation assay (ChIP). Taken together, TNF-α can upregulate the expression of VEGF-C and promote the lymphangiogenesis of GBC via NF-κB combining with the promoter of VEGF-C.

Gallbladder cancer (GBC) is a demanding fatal disease with no ideal treatment for inoperable patients. Recent reports have determined TNF-α associated lymphatic metastasis in GBC, while its resistance to TNF-α-killing remains largely unexplored. In this assay, we first found cellular inhibitor of apoptosis (cIAP1) overexpressed in GBC tissues and the roles in promoting the proliferation and migration of GBC in vitro as its homology cIAP2 does. Then how GBC cell survives TNF-α toxicity and TNF-α-induced apoptosis first prevail as follows. The reduction in cIAP1 does not give rise to apoptosis even with the stimulation of TNF-α. Importantly, the loss of cIAP1 enhanced TNF-α/cycloheximide-induced apoptosis in higher activation statuses of Caspase-8, Caspase-3 without the induction of Complex Ⅱ. In response to TNF-α, the reduction in cIAP1 caused the suppression in nuclear factor-κB (NF-κB) pathway and inhibition of transcription of cell death regulator cellular FLICE-like Inhibitory Protein (c-FLIP) instead. To conclude, cIAP1 is an oncological protein abundant in GBC tissues, which enhances proliferation and immigration and blocks TNF-α from apoptosis through NF-κB pathway in vitro.

Several studies have produced contradictory findings about the prognostic implications for inhibitor of apoptosis proteins (IAP) in different types of cancer. Cellular inhibitor of apoptosis 2 (cIAP2/BIRC) is one of the most extensively characterized human IAP. To date, no studies have focused on the expression level of cIAP2 in human gallbladder cancer (GBC), and the mechanism of cIAP2 in GBC invasion and lymphangiogenesis remains unclear. Therefore, in the present study, cIAP2 expression in GBC was detected using quantitative real-time polymerase chain reaction and immunohistochemistry, and the relationship between cIAP2 levels in cancer tissues and the clinicopathological characteristics of patients was analyzed. The biological effect of cIAP2 in GBC cells was tested using the Cell Counting Kit-8 Assay, Transwell assays and the ability of human dermal lymphatic endothelial cells (HDLEC) to undergo tube formation. The role of cIAP2 in activating the NF-κB pathway was determined using a dual-luciferase reporter assay, immunofluorescence staining, western blotting and ELISA. Finally, an animal model was used to further confirm the role of cIAP2 in lymphangiogenesis. We showed that cIAP2 expression was elevated in human GBC tissues and correlated with a negative prognosis for patients. Moreover, cIAP2 was identified as a lymphangiogenic factor of GBC cells and, thus, promoted lymph node metastasis in GBC cells. Our study is the first to suggest that cIAP2 can promote GBC invasion and lymphangiogenesis by activating the NF-κB pathway.