Figure 4. Co-treatment of MCL cells with bortezomib and Panobinostat induces enhanced ER stress in MCL cells.

A, JeKo-1 cells were treated with indicated doses of PS and/or BZ for 6 hours and the expression of GRP78, CHOP, NOXA, PUMA, p-eIF2α, eIF2α, and GADD34 was assessed by immunoblot analysis. B, Alternatively, the expression of CHOP, GADD34, ERO-1α, NOXA and β-actin mRNA was assessed by RT-PCR following 6 hours of exposure of JeKo-1 cells to BZ and PS. C, JeKo-1 cells were treated with PS and BZ at a 1:1 molar ratio stained for Annexin V-PI. Percentage of apoptotic cells was assessed by flow cytometry. The combination index (CI) for each treatment was determined using Calcusyn software. CI values of less than 1.0 represent synergistic interactions. D, JeKo-1 cells were infected with retroviral scrambled siRNA or CHOP siRNA and treated with PS following 48 hours of infection. Viability of cells following CHOP knockdown and 24 hours of exposure to PS was assessed by trypan blue dye exclusion assay and a hemocytometer. Values presented are an average of three independent experiments ± standard deviation. Inset shows immunoblot analysis of CHOP protein after 48 hours of infection.