Nephronectin induced activation of intracellular signaling pathways in breast cancer

Abstract

The aim of this project was to characterize the intracellular signaling pathways induced by extracellular matrix protein (ECM) Nephronectin (Npnt) in cell line 66cl4. Cell line 66cl4 is a cell line from a mouse mammary tumor model, and is it characterized as a weakly- metastatic cell line. A genomic study revealed that highly metastatic cell line 4T1 in this tumor model expressed elevated levels of Npnt. Npnt is a ECM protein involved in development of endocrine organs through integrin receptor α8β1 and αvβ3. Research from our group has shown that increased levels of NPNT in breast cancer patients is correlated with poor prognosis (unpublished results). To be able to understand the detailed function of the Npnt protein; four different cell lines variants were made for stable overexpression of the Npnt protein and mutated variants of the Npnt protein. These cells are denoted 66cl4- EV (empty vector), 66cl4- Npnt (wild type), 66cl4 -RGE (mutated RGD domain) and 66cl4 - RGE-AIA (mutated RGD-EIE domain). In this study we have been investigating five different signaling pathways: focal adhesion kinase (FAK), Akt, also known as Phosphoinositide 3-kinase (PI3K), extracellular signal-regulated kinase (ERK), also known as Mitogen activated protein kinase (MAPK), Src (sarcoma) and ILK (integrin- linked kinase). Activation of these signaling pathways is leading to several cellular events such as, adhesion, migration, survival, growth, differentiation and proliferation of the cell. The results from western blots revealed that Npnt may activate FAK and Akt signaling pathways, but further experiments are required to be able to conclude.