MAPK3 and lung cancer: A number of studies have reported that in vitro or in vivo pharmacologic inhibition of ERK1/2 using a selective MEK1/2 inhibitor can cause decrease in pERK1/2 and cell proliferation, and treatment of MEK inhibitor lead lung tumor regression and a decrease in pERK1/2 in KRAS mutant mouse lung cancer model 24, 29.