Here, we test the applicability and efficiency of the system in its constitutively active and doxycyclin-inducible forms by collectively knocking down the four components of the MEK/MAPK module (the proteins MAP2K1 (MEK1), MAP2K2 (MEK2), MAPK3 (ERK1), and MAPK1 (ERK2)) in transient and stable transfections of multiple myeloma cell lines. This evidence concerns the gene MAPK3 and AL amyloidosis.