A) Crocidolite asbestos (5 μg/cm2) increased ERK5 phosphorylation at 4 h after addition to human mesothelial cells (LP9). Glass beads (GB, a non-fibrous negative control) at the same surface area concentration had no effect on ERK5 activation, and epidermal growth factor (EGF) (5 ng/ml for 1h) significantly activated ERK5 several fold. B) Different human MM lines showed constitutive activation of ERK5 as compared to the LP9 cells. *p≤0.05 as compared to LP9. C) Effect of EGFR (AG1478, 20μM, 24 h) or HGFR/c-MET inhibitor (10 μM, 24 h) on constitutive pERK5 levels in 4 MM cell lines. *p≤0.05 as compared to DMSO (0) treated solvent controls. Each graph represents an independent experiment with its own control group.