The general lack of knowledge surrounding the precise function of the four mesothelioma prognostic genes (ARHGDIA, COBLL1, PKM2, TM4SF1) indicated the importance of examining a normal cell line and WI38, while not ideal, was chosen because it is of similar embryonic origin (i.e., mesoderm) to mesothelial cells lining the thoracic pleura. This evidence concerns the gene ARHGDIA and mesothelioma.