The in vitro effects of a polyphenol epigallocatechin gallate on the cell viability, adhesion, and morphology of melanoma and endothelioma cells

Abstract

Adhesion molecules play a crucial role in the process of cancer cells adhering to and metastasising to secondary locations within the body. Adhesion molecules such as E-cadherin, play a crucial role in the adhesion and metastasis of cancers. A polyphenol compound known as epigallocatechin gallate (EGCG) is predominantly found in green tea and has been demonstrated to possess health benefits, including antioxidant and anti-inflammatory properties. This study focused on investigating the impact of EGCG on the adhesion of tumour cells across four distinct cell lines. These included B16F10 melanoma cells, sEnd.2 endothelioma cells, and two control cell lines, namely RAW 264.7 macrophage cells and EA.hy926 endothelial cells. The study determined the half maximal inhibitory concentrations (IC50) values for four cell lines using a crystal violet assay and examined their morphological changes post EGCG treatment using haematoxylin and eosin (H&E) staining and polarisation optical differential interference contrast (PlasDIC) imaging. The study also used flow cytometry to study intracellular proteins and conducted an adhesion assay to evaluate the adhesion of the cell lines, pre-treated with fibronectin or collagen IV, after EGCG exposure. Crystal violet assays revealed that EGCG induced cell death in the cancerous cell lines, namely B16F10 and sEnd.2, while its impact on the non-cancerous cell lines, RAW 264.7 and EA.hy926, was less pronounced. Morphological results revealed that both cancerous cell lines exhibited characteristic features of cell death (membrane blebbing, compromised cell membrane, nuclear condensation and cell swelling) following treatment with EGCG. Flow cytometry analysis provided evidence that EGCG had halted the two types of cancerous cells (B16F10 and sEnd.2) and non-cancerous cells (RAW 264.7) cell cycle in the G1 phase. Furthermore, EGCG had enhanced the expression of E-cadherin in the B16F10 and RAW 264.7 cell lines, but E-cadherin expression in the sEnd.2 cell line was not as substantial. EGCG exposure on B16F10 cells pre-treated with fibronectin did not have the ability to reduce the adhesive ability on the B16F10 cells. However, EGCG exposure on B-16F10 cells pre-treated with collagen IV significantly reduced the adhesive ability of the B-16F10 cells. In contrast, sEnd.2 cells exposed to EGCG coated with either fibronectin or collagen IV, significantly reduced adhesion ability of the sEnd.2 cells. RAW 264.7 cells, responded differently: cells pre-treated with fibronectin showed a decrease in adhesion at the higher EGCG concentration compared to the control group. While cells pre-treated with collagen IV showed a general decrease in adhesion, irrespective of EGCG concentration. Page 11 of 125 EGCG demonstrated the ability to induce cell death in cancerous cells. However, the exact biological pathways and mechanisms that EGCG utilises to induce cell death are not yet fully understood and may vary between different types of cancerous cells. Therefore, further understanding of these mechanisms could have significant implications for cancer research.