Molecular Characterization of the Extracellular Matrix Protein TINAGL1 in Breast Cancer

Abstract

Previous work in this group using Mass Spectrometry (MS) analysis of extracellular matrix (ECM) from breast tumor samples at different tumor stages, had reported that TINAGL1 is highly expressed during breast carcinogenesis with increasing levels correlated with tumor progression. TINAGL1 is a novel matricellular protein in the ECM. It is known from the literature that TINAGL1 is a positive regulator of angiogenesis and by promoting invasion, function during embryo implantation in mice.

In this project, expression levels of TINAGL1 protein and mRNA were investigated by histological analysis in a transgenic mouse model of breast cancer. Based on results from immunohistochemistry, TINAGL1 protein was found to be located in the most of the tumors with higher levels at the invasive tumor fronts. To verify this finding, in situ hybridization was performed. According to this analysis, TINAGL1 mRNA was also found to be accumulated around the tumor edges and the total amount of TINAGL1 is increasing with increasing tumor grade. In the next stage, to characterize the molecular function of this protein, adhesion, proliferation and migration assays were performed using xCELLigence assays. Mouse tumor epithelial cells, the 4T1 cell line, with stable knockdown of TINAGL1 were used in these experiments. The results from these assays were not completely unambiguous and we were not able to conclude any specific function for TINAGL1.

In conclusion, we trust our results from histological analysis as they were in vivo experiments. Considering the presence of TINAGL1 in invasive front of tumors and also previous findings that suggest a role of TINAGL1 in invasion, we assume that TINAGL1 may play a role in invasion processes in breast carcinogenesis. To demonstrate TINAGL1’s function we used a 2D in vitro assay. As TINAGL1 is suggested to play a role in invasion processes we suggest that 3D-assays may be more suitable to characterize the specific function of TINAGL1 in breast cancer progression.