γ-Synuclein confers both pro-invasive and doxorubicin-mediated pro-apoptotic properties to the colon adenocarcinoma LS 174T cell line

Abstract

γ-synuclein, a neuronal protein of the synuclein family, is involved in carcinogenesis. To investigate its role in colorectal cancer carcinogenesis, we overexpressed γ-synuclein in LS 174T colon adenocarcinoma cell line (termed LS 174T-γsyn). When compared with untransfected/mock transfectants, LS 174T-γsyn had higher mobility in scratch wound assay, tend to scatter more in cell-scattering assay, and had enhanced lamellipodia and filopodia formation in cell-spreading assay. Enhanced adhesion of LS 174T-γsyn to fibronectin and collagen and significantly higher proliferation rate showed that γ-synuclein was able to increase extracellular matrix interaction and promoted proliferation of LS 174T. Higher invasiveness of LS 174T-γsyn was evidenced by enhanced invasion to the bottom of the basement membrane in Boyden chamber assay. However, LS 174T-γsyn were significantly more vulnerable to doxorubicin, vincristine and hydrogen peroxide insults, via apoptotic cell death. LS 174T-γsyn also had reduced anchorage-independent growth as shown by reduced colony formation and reduced anoikis resistance. We found that overexpression of γ-synuclein confers both pro-invasive and doxorubicin-mediated pro-apoptotic properties to LS 174T, where the former was mediated through enhanced cyclic adenosine monophosphate response element binding protein (CREB) phosphorylation, while the latter involved hepatocyte growth factor (HGF) downregulation and subsequent downstream signalling pathways possibly involving extracellular signal-regulated kinases (ERK)1/2, p38α, c-Jun N-terminal kinase (JNK) pan and Signal Transducers and Activators of Transcription (STATs). This unexpected contrasting finding as compared to other similar studies on colon cancer cell lines might be correlated with the degree of tumour advancement from which the cell lines were derived from.

Keywords: Apoptosis; Colon cancer; Invasion; Metastasis; Synuclein-gamma.