FBX8 Acts as an Invasion and Metastasis Suppressor and Correlates with Poor Survival in Hepatocellular Carcinoma

Abstract

BackgroundF-box only protein 8 (FBX8), a novel component of F-box proteins, is lost in several cancers and has been associated with invasiveness of cancer cells. However, its expression pattern and role in the progression of hepatocellular carcinoma remain unclear. This study investigated the prognostic significance of FBX8 in hepatocellular carcinoma samples and analyzed FBX8 function in hepatocellular carcinoma cells by gene manipulation.MethodologyThe expression of FBX8 was detected in 120 cases of clinical paraffin-embedded hepatocellular carcinoma tissues, 20 matched pairs of fresh tissues and five hepatocellular carcinoma cell lines by immunohistochemistry with clinicopathological analyses, real-time RT-PCR or Western blot. The correlation of FBX8 expression with cell proliferation and invasion in five HCC cell lines was analyzed. Moreover, loss of function and gain of function assays were performed to evaluate the effect of FBX8 on cell proliferation, motility, invasion in vitro and metastasis in vivo.ConclusionsWe found that FBX8 was obviously down-regulated in HCC tissues and cell lines (P<0.05). The FBX8 down-regulation correlated significantly with poor prognosis, and FBX8 status was identified as an independent significant prognostic factor. Over-expression of FBX8 decreased proliferation, migration and invasion in HepG2 and 97H cells, while knock-down of FBX8 in 7721 cells showed the opposite effect. FBX8 negatively correlated with cell proliferation and invasion in 7701, M3, HepG2 and 97H cell lines. In vivo functional assays showed FBX8 suppressed tumor growth and pulmonary metastatic potential in mice. Our results indicate that down-regulation of FBX8 significantly correlates with invasion, metastasis and poor survival in hepatocellular carcinoma patients. It may be a useful biomarker for therapeutic strategy and control in hepatocellular carcinoma treatment.

F-box protein interactions with the hallmark pathways in cancer

“…As Fbxo8 negatively regulates Arf6, which enhances cell invasiveness, it might be classed as a potential TSG. mRNA and protein expression appear to be absent in samples from lung, colon, liver and breast cancers, which is consistent with this notion (211)(212)(213).…”

The Suppressive Role and Aberrent Promoter Methylation of BTG3 in the Progression of Hepatocellular Carcinoma

“…Genomic DNAs of LO2, HepG2 and 97H cells[19-21] were obtained using GeneJET Genomic DNA purification Kit (Thermo, Salt Lake city, USA) and then bisulfite-modified using the Epitect Plus DNA Bisulfite Kit (Qiagen, Valencia, Calif). The CpG island of BTG3 gene was predicted online (http://www.urogene.org/methprimer/index1.html).…”

A CULLINary ride across the secretory pathway: more than just secretion

“…Recent work suggests that CUL3-mediated ubiquitylation may regulate trafficking along the endosomal pathway [90]. Cells devoid of CUL3 show defects in the endocytic transport of influenza A virus (IAV) and epidermal growth factor receptor (EGFR) [106].…”

“…SCF FBXO8 mediates polyubiquitylation of Arf6 (but not other Arf GTPases), and this modification interferes with the interaction between Arf6 activator and effector proteins. Down-regulation of this CRL pathway may correlate with increased tumor invasion and metastasis [88–90]. Other Arf isoforms are also ubiquitylated [29], but whether those are CRL-mediated is not known.…”