Date of Award

2019-01-01

Degree Name

Doctor of Philosophy

Department

Biological Sciences

Advisor(s)

Jianying . Zhang

Second Advisor

Giulio . Francia

Abstract

The family of insulin- like growth factor 2 mRNA binding proteins (IMPs) contains three members: IMP1, p62/IMP2 and IMP3. All these proteins are oncofetal proteins, expressed during embryogenesis and lost in most tissues in adults. However, p62/IMP2 were found overexpressed in various cancers but its function in carcinogenesis remains to be investigated. Our previous studies found that p62/IMP2 was not only overexpressed in hepatocellular carcinoma (HCC) tissues, but also overexpressed in HCC cell lines. To explore the biological roles of p62/IMP2 in HCC progression, p62/IMP2 was knockout in two p62/IMP2 positive HCC cell lines (SNU449, HepG2). Due to the low expression level of p62/IMP2 in SNU449, we overexpressed p62/IMP2 in this cell line. The results from both of wound healing assay and transwell migration assay indicated that overexpressed p62/IMP2 in both cell lines could promote the cell migration significantly (p<0.05). On the contrary, the lack of p62/IMP2 expression can reduce the cell migration ability (p<0.05). After analyzing the HCC expression data from Gene Expression Omnibus (GEO), the high and low p62/IMP2 expression groups were set up based on the median expression of p62/IMP2 from GSE 14520. CTNNB1 was selected in differential gene expression analysis with a cancer-metastasis related gene profile. Subsequently, western blotting analysis was performed to explore the effect of overexpressed p62/IMP2 on Wnt/β-catenin pathway-related proteins, and we found that overexpressed p62/IMP2 can significantly enhance the expression of Wnt and β-catenin, whereas inhibiting the expression of Gsk3b and E-cadherin. A Wnt/β-catenin signaling pathway inhibitor XAV939 was used for confirming the results. Nevertheless, although β-catenin expression dramatically reduced in p62/IMP2 knockdown SNU449 cells, their colony formation ability was still enhanced by activating Wnt5-induced non-canonical Wnt signaling. In addition, we validated our results at the phosphorylation level by using Wnt pathway phosphoproteome chips. In summary, our data showed that overexpressed p62/IMP2 can enhance the migration ability of HCC cells via activating Wnt/β-catenin.

Language

en

Provenance

Received from ProQuest

File Size

109 pages

File Format

application/pdf

Rights Holder

Mengtao Xing

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