Figure 6.

Enhanced ER stress loading by combined treatment with BTZ and RCS in CAL27 cells. (A) Immunoblotting with GRP78 mAb and CHOP mAb of cell lysates of CAL27 cells obtained following culture under the complete culture condition with/without BTZ (5 nM) in the presence or absence of RCS (5 µM) for 12, 24, 36 and 48 h. Treatment with thapsigargin at 300 nM for 24 h was performed as a positive control for ER stress loading. Immunoblotting with anti-β-actin mAb was used as an internal control. Numbers indicate the ratios of the GRP78 to β-actin and the CHOP to β-actin in each lane. (B) CAL27-XBP1-Venus cells were treated with BTZ (10 nM) and with/without RCS (10 µM). ER stress loading was quantitatively monitored during a 48-h exposure to these drugs. RCS, ricolinostat; BTZ, bortezomib; mAb, monoclonal antibody; ER, endoplasmic reticulum.