Characterization of TFPIalpha and TFPIbeta on growth, adhesion and migration in breast cancer cells

Abstract

Tissue factor pathway inhibitor (TFPI) is a plasma serine protease inhibitor which contains three Kunitz-type protease inhibitor domains. TFPI can be transcribed into two main isoforms; TFPIα and TFPIβ by alternative splicing. The main function of TFPI is to inhibit tissue factor initiated blood coagulation, however, increasing evidence has shown that TFPI may have an additional role in cancer development. Previous studies have reported that overexpression of both TFPIα and TFPIβ induces apoptosis in breast cancer cells, and that downregulation of TFPI increases tumor growth by stimulating cell motility. The effect of downregulated TFPIα in breast cancer cells has not been reported before, and only few have studied the effect of the separate isoforms in breast cancer cells. To further examine TFPI isoforms role in cancer development, siRNAs that exclusively knock down the TFPIα isoform were designed and a knockdown and an overexpression model of TFPIα and TFPIβ were made. These models were further used in functional studies to investigate how the manipulated TFPI levels affected growth, adhesion and migration of breast cancer cells.

The results provided in this thesis showed a slight decrease in adhesion to collagen I together with reduced levels of the adhesion molecule integrin α2 by upregulation of TFPIα, and a reduction in migration of both TFPIα and TFPIβ upregulated cells. A reduction of phosphorylated Src levels were also measured in the upregulated TFPIα and TFPIβ cells. This may indicate a possible anti-tumor function of both the TFPI isoforms where Src signaling may be involved. It was also identified a new breast cancer cell line (MDA-MB-436) with same characteristics as MDA-MB-231 where stable cell lines with TFPIα and TFPIβ upregulated were established. These cells may be useful in further studies of TFPI isoforms role in cancer development.