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T. Lewis et al.
gene transcription with a smaller subset of genes showing increased transcription following exposure to the drug. In unsupervised hierarchical clustering, the samples clustered according to treatment condition (Figure 5A). Strikingly, 4,040/5,077 (80%) of the genes altered by exposure to the drugs were common to both PBD compounds (Figure 5B) suggesting that their structural similarity resulted in the inhibition of a conserved set of genes. Furthermore, gene set enrichment analysis, using WebGestalt (WEB-based GEne SeT AnaLysis Toolkit),25 confirmed that NF-κB-regu- lated genes were significantly over-represented in the downregulated gene list, with a normalized enrichment score of -1.7750 (Figure 5C, D). These data suggest that
inhibition of NF-κB target genes may contribute to the cytotoxicity of the PBD compounds.
A
B
CD
Synergy between DC-1-192 in combination with borte- zomib or ibrutinib
Overexpression of NF-κB is associated with chemother- apeutic drug resistance in both CLL and multiple myelo- ma.26,27 Having established that DC-1-192 inhibited nuclear NF-κB DNA binding and downregulated NF-κB target genes, we set out to determine whether these inhibitory properties could enhance the killing effect of bortezomib and ibrutinib in the JJN3 myeloma cell line and primary CLL cells, respectively. To investigate syner-
EF
Figure 3. DC-1-192 was highly cytotoxic in primary chronic lym- phocytic leukemia cells and showed preferential effects in BIRC3 and NOTCH1 mutated samples. (A) All 46 samples test- ed showed low nanomolar LD
50 values when treated with DC-1- 192. (B-D) Analysis of prognostic subsets revealed that DC-1-192 was equipotent in IGHV mutated and unmutated samples (B), CD38-positive and CD38-negative samples (C) and samples with
- microglobulin (D). (E) In contrast, BIRC3 and NOTCH1 mutated sam- ples showed significantly increased sensitivity to DC-1-192. (F) There was an inverse relation- ship between nuclear DNA bind- ing of the canonical NF-κB sub-
high or low concentrations of β 2
unit, p65, and DC-1-192 LD ues.
50
val-
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haematologica | 2021; 106(4)