Intrinsically bortezomib-resistant MCL cell lines show plasmacytic features. (A) Dose response of bortezomib (Bzm) in JEKO, HBL2, MINO, and REC1 PT cell lines at 48 hours. The MTT assay was used as readout of viability. (B) Expression of the plasma-cell surface markers CD38 and CD138 measured by flow cytometry. (C) IRF4 expression assessed by Western blot in nuclear fractions using TBP as loading control, and by flow cytometry using the same antibody conjugated to Alexa 647. (D) Analysis of XBP1 mRNA expression by RT-PCR. The active, spliced form (XBP-1s) is shorter and runs faster on the gel than the inactive, unspliced form (XBP-1u). JEKO cells treated with thapsigargin (2μM) for 6 hours were used as the positive control (+) and glyceraldehyde-3-phosphate dehydrogenase (GADPH) for the loading control. (E) Detection of κ and λ immunoglobulins by sandwich ELISA in media containing 50 ng/mL of polyclonal human immunoglobulin G and in supernatants of MCL cell lines cultured for 24 hours at 1 × 106 cells/mL. The absorbance at 450 nm is shown for triplicates ± SD.
