Proteomic analysis of TGF beta-induced A549 secretome identifies putative regulators of epithelial-mesenchymal transition

Imparting epithelial to mesenchymal transition (EMT) during cellular transformation, a major driving force behind tumor progression, is one of the notorious oncogenic activities of transforming growth factor beta (TGF beta); however, the secretary factors released during TGF beta-induced EMT that may have role in potentiating EMT and tumor progression are poorly known. This study was undertaken to identify such secreted protein factors from TGF beta-induced A549 cells cultured in serum-free chemically defined medium (Freestyle(TM)) using Matrix Assisted Laser Desorption Ionization-Time of flight/Time of flight (MALDI-TOF/TOF) mass spectrometry. We identified some of the potential factors such as ESR, ANXA2, ALDH1A, TGF beta-induced protein ig-h3, and PAI-1 that were not only secreted but some were also elevated in TGF beta-induced A549 cells. Interestingly, these factors are widely reported to play crucial role in EMT induction and progression, which not only validates our findings but also opens avenues for further investigation, if upon secretion they act exogenously through certain receptors to potentiate cellular signaling involved in EMT induction and tumor progression.