SRC Knockout Cell Line (HCT 116)

BACKGROUND:The scaffold protein tyrosine kinase substrate 4 (TKS4) undergoes tyrosine phosphorylation by the epidermal growth factor receptor (EGFR) pathway via Src kinase. The TKS4 deficiency in humans is responsible for the manifestation of a genetic disorder known as Frank-Ter Haar syndrome (FTHS). Based on our earlier investigation, the absence of TKS4 triggers migration, invasion, and epithelial-mesenchymal transition (EMT)-like phenomena while concurrently suppressing cell proliferation in HCT116 colorectal carcinoma cells. This indicates that TKS4 may play a unique role in the progression of cancer. In this study, we demonstrated that the enhancer of zeste homolog 2 (EZH2) and the histone methyltransferase of polycomb repressive complex 2 (PRC2) are involved in the migration, invasion, and EMT-like changes in TKS4-deficient cells (KO). EZH2 is responsible for the maintenance of the trimethylated lysine 27 on histone H3 (H3K27me3). METHODS:We performed transcriptome sequencing, chromatin immunoprecipitation, protein and RNA quantitative studies, cell mobility, invasion, and proliferation studies combined with/without the EZH2 activity inhibitor 3-deazanoplanocine (DZNep). RESULTS:We detected an elevation of global H3K27me3 levels in the TKS4 KO cells, which could be reduced with treatment with DZNep, an EZH2 inhibitor. Inhibition of EZH2 activity reversed the phenotypic effects of the knockout of TKS4, reducing the migration speed and wound healing capacity of the cells as well as decreasing the invasion capacity, while the decrease in cell proliferation became stronger. In addition, inhibition of EZH2 activity also reversed most epithelial and mesenchymal markers. We investigated the wider impact of TKS4 deletion on the gene expression profile of colorectal cancer cells using transcriptome sequencing of wild-type and TKS4 knockout cells, particularly before and after treatment with DZNep. Additionally, we observed changes in the expression of several protein-coding genes and long non-coding RNAs that showed a recovery in expression levels following EZH2 inhibition. CONCLUSIONS:Our results indicate that the removal of TKS4 causes a notable disruption in the gene expression pattern, leading to the disruption of several signal transduction pathways. Inhibiting the activity of EZH2 can restore most of these transcriptomics and phenotypic effects in colorectal carcinoma cells.

Although E-cadherin is known as a tumor suppressor via its effects on cell to cell adhesion, the effects of E-cadherin on malignant transformation have not yet been thoroughly investigated. In the present study, after malignant transformation was induced by spheroid formation in a fetal bovine serum-supplemented environment, the effects of soluble E-cadherin on the spheroidogenesis of colorectal cancer cells were investigated. E-cadherin knock-out (KO) was performed in HCT116 cells, targeting exon 3 of the CDH1 gene. A cell viability assay was performed to determine the proliferation and viability of wild type and CDH1 KO HCT116 cells after treatment with anticancer drugs. Spheroidogenesis was compared with or without exogenous E-cadherin, antibody against the ectodomain of E-cadherin (DECMA-1) and PD98059 treatment. In addition, morphometry, immunocytochemistry and western blotting were performed. Soluble E-cadherin in culture media was measured using an enzyme-linked immunosorbent assay. Firstly, CDH1 KO was confirmed by western blotting. Notably, the proliferation and viability of cells following treatment with 5-fluorouracil, epidermal growth factor receptor inhibitor and src kinase inhibitor were similar between the cell lines. Exogenous E-cadherin or DECMA-1 treatment did not affect spheroidogenesis, although long-term maintenance was slightly disturbed in CDH1 KO spheroids compared with that in wild type spheroids. In addition, E-cadherin was increased in spheroid culture as compared with that in conventional culture. Soluble E-cadherin was increased in a time-dependent manner, particularly in wild type HCT116 cells. PD98059 inhibited ERK activation and enhanced E-cadherin expression in conventional culture without affecting spheroidogenesis. These results suggested that soluble E-cadherin may be considered as a biomarker for colorectal cancer, although exogenous E-cadherin might not have a further role in malignant transformation.