To determine whether ERK1 and/or ERK2 involved in LPS-induced G-CSF expression, ERK expression in THP-1 human acute monocytic leukemia cells was knocked down using shRNA clones ERK1a and ERK1b carrying two different ERK1 sequences or shRNAs ERK2a and ERK2b carrying two different ERK2 sequences. The gene discussed is MAPK3; the disease is acute monocytic leukemia.