Conclusion
In non-GCB DLBCL cells, NF-κB downregulates PRDM1 and thereby promotes MDR1 transcription by terminating PRDM1-induced transcriptional inhibition of MDR1. Such a mechanism may explain the reason for disease recurrence in non-GCB DLBCL after R-CHOP or combined CHOP with bortezomib treatment. Our findings may provide a potential therapeutic strategy for reducing drug resistance in patients with DLBCL.
Methods
Doxorubicin (DOX)-resistant OCI-Ly3 cells were generated through long-term incubation of cells in a medium with gradually increasing DOX concentrations. The expression levels of genes related to drug metabolism were determined using a functional gene grouping polymerase chain reaction (PCR) array. Drug-resistant proteins were identified using bioinformatics, and molecular association networks were subsequently generated. The association and mechanism of key genes were determined using a dual-luciferase reporter assay System and chromatin immunoprecipitation (ChIP). The expression of drug-resistant genes and target genes was then measured using Western blotting and immunohistochemistry. The correlation between gene expressions was analyzed using Spearman's rank correlation coefficient.
Results
Using the PCR array, MDR1 was identified as the key gene that regulates DOX resistance in OCI-Ly3/DOX-A100, a non-GCB DLBCL cell line. The dual-luciferase reporter assay system demonstrated that MDR1 transcription could be inhibited by PRDM1. ChIP results showed that PRDM1 had the ability to bind to the promoter region (-1,132 to -996) of MDR1. In OCI-Ly3/DOX cells, NF-κB activity and PRDM1 expression decreased with an increase in drug-resistant index, whereas MDR1 expression increased with enhanced drug resistance. Immunohistochemical analysis revealed that relative MDR1 expression was higher than that of PRDM1 in human DLBCL tissue samples. A negative correlation was observed between MDR1 and PRDM1.