[The role and molecular mechanism of transcription factor EB and its target genes in multiple myeloma treatment with bortezomib].

Objective: To investigate the role and molecular mechanisms of transcription factor EB (TFEB) and its target genes in the treatment of multiple myeloma (MM) with bortezomib. Methods: TFEB target genes were predicted using the GTRD database (http://gtrd.biouml.org/), identifying Ptch1 gene for further study. Expression changes of Ptch1 in RPMI8226 and U266 MM cell lines after bortezomib treatment were assessed by real time fluorogenic quantitative PCR (RT-qPCR) and Western blot. RPMI8226 and U266 cell lines were transfected with siRNA-TFEB, and mRNA and protein levels of key factors (Ptch1, Gli1) in the Ptch1/Hedgehog signaling pathway were measured by RT-qPCR and Western blot. Furthermore, Ptch1 was overexpressed in MM cell lines via lentiviral transduction. Autophagy was evaluated by acridine orange staining, and protein levels of LC3B, Beclin-1, and Lamp-1 were measured by Western blot. Lysosomal quantity changes were assessed by lysosomal fluorescent probes. Results: Bortezomib (6.0×10(-6) mmol/L, 24 h) significantly reduced Ptch1 mRNA and protein levels in both cell lines compared with blank control group (all P<0.05). siRNA-TFEB transfection reversed bortezomib's inhibition of Hedgehog pathway key factors Ptch1 and Gli. Ptch1 overexpression in bortezomib-treated RPMI8226 and U266 cells significantly reduced the relative expression of autophagy-related proteins LC3B, Beclin-1, and Lamp-1 (all P=0.001). Acridine orange staining showed fewer acidic vesicular organelles within two cell lines (all P=0.001). The relative fluorescence expressions of lysosomal probes reflecting the number of lysosomes were also decreased (P values of RPMI8226 and U266 cell lines were 0.001 and 0.007, respectively) . Conclusion: The knockdown of TFEB can specifically promote the expression of the Ptch1/Hedgehog signaling pathway, thereby reducing bortezomib-induced autophagy in MM cells and reversing the inhibitory effect of bortezomib on the proliferation of MM cell lines.