TGFA and mucoepidermoid carcinoma: Since activation of ADAM17 and ADAM17-mediated shedding can be induced via PKC stimulation [26,42], we tried to enhance the shedding of TGFα by exposing NHBE cells to phorbol-12-myristate 13-acetate (PMA), a known activator of PKC and well-characterized inducer of TGFα ectodomain shedding [43], at a concentration shown previously to enhance TGFα shedding in a pulmonary mucoepidermoid carcinoma cell line (NCI-H292) [30].