Depletion of TRF6 sensitizes cells to bortezomib by regulating PSMA1. (A) Microarray analysis was performed on TF-1 cells after knockdown of TRAF6. Shown are differential gene-expression data between shTRAF6 and vector-transduced cells for all proteasome subunit genes (see supplemental Table 1). Expression of PSMA1 (highlighted in red) was most significantly down-regulated in cells with reduced TRAF6 expression (P < .05). (B) TF-1, Bort-S THP-1, Bort-R THP-1, and MDS BM cells (MDS-02) were transduced with shRNA lentiviral vectors targeting TRAF6 or a nontargeting control (shCTL). Down-regulation of PSMA1 in cells with reduced TRAF6 expression was confirmed by quantitative PCR. (C) Bort-R cells were transduced with 2 independent shRNA lentiviral vectors (sh#70 and sh#72) targeting PSMA1 or shCTL. Knockdown of PSMA1 was confirmed by quantitative PCR (sh#70, 89.6% knockdown; sh#72, 85.6% knockdown). Cell viability of Bort-R cells transduced with shPSMA1 or control vector was determined by MTT assay after treatment with 10nM bortezomib for 24 hours. (D) Proteasome inhibition in bortezomib-treated Bort-R cells transduced with 2 independent shPSMA1 or control vector was determined by immunoblotting for ubiquitinated proteins on total cell lysates. *P < .05.