[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.