Human MM lines show ERK1/2 activation after exposures to Doxorubicin (Dox). A. Two different MM lines (MO and ME-26) were treated with Dox (0-100 μM) for 24 h and cell viability was determined by the MTS assay as described in the 'Materials and Methods'. *p ≤ 0.05 as compared to control (0), N = 3-6 per group. B. Western blot analysis was performed using specific antibodies for pERK1/2 and total ERK1/2 as described in the 'Materials and Methods'. Both ERK1 and ERK2 were activated (see pERK1 and pERK2) in response to Dox; however, total ERK1 and 2 remained unchanged. *p ≤ 0.05 as compared to respective controls. N = 2 per group. HMESO MM line showed very little ERK1 and pERK1 as compared to other cell lines. C. Dox-activated ERK1/2 in different MM lines is attenuated by the MEK1/2 inhibitor U0126 (20 μM, for 1 h), whereas its inactive analog U0124 is ineffective. *p ≤ 0.05 as compared to respective untreated (0) controls. †p ≤ 0.05 as compared to Dox treated groups. N = 2 per group.