Development and evaluation of a novel series of Nitroxoline-derived BET inhibitors with antitumor activity in renal cell carcinoma

Abstract

Small molecular inhibitors targeting BRD4 family proteins are emerging as promising therapies in many types of human malignancies. However, whether BRD4, as well as other BET family members, may serve as therapeutic targets in renal cell carcinoma (RCC) remains unknown. In this study, we found that both BRD2 and BRD4 were over-expressed in RCC tissues, knock-down both of which achieved potent anti-proliferative effects in RCC cells. A novel category of BET inhibitors, originated from an approved drug Nitroxoline, were synthesized and evaluated with biochemical and cellular assays, as well as the method of crystallography. The complex crystal structures of several compounds in this category with the first bromodomain of BRD4 (BRD4-BD1) were solved, revealing the binding mechanism and facilitating further structural optimizations. Among them, compound BDF-1253 showed an approximately four-fold improvement in BRD4 inhibition compared with the prototype Nitroxoline and had good selectivity for BET proteins against other bromodomain proteins or epi-enzymes in biochemical assays. Compound BDF-1253 efficiently suppressed the expression of BET downstream genes, impaired RCC cells viability via inducing cell cycle arrest and apoptosis, and decreased tumor growth in RCC xenografts. In summary, these results suggest that inhibition of BET family members has great therapeutic potentials in the treatment of RCC, and the novel series of BET inhibitors reported here are promising to become RCC drug candidates.

Integrative proteomic and functional analyses provide novel insights into the action of the repurposed drug candidate nitroxoline in AsPC-1 cells

“…In that study, nitroxoline was found to affect viability, to drastically reduce clonogenic activity, to hamper cell cycle and to promote apoptosis in pancreatic cancer cell lines, both as a single agent and in combinations with other drugs 7 . In addition to pancreatic cancer, this drug affects viability and growth of cell lines representative of other tumors, including neuroblastoma, glioma, myeloma, prostate, lung, kidney and bladder cancers [8][9][10][11][12][13][14][15][16][17][18][19] . Remarkably, this antibiotic is also effective in several cancer xenograft and genetically engineered mice models [8][9][10]12,14,15,18 .…”

“…Nitroxoline is an antibiotic widely used in several countries from 1960s and is able to chelate divalent metal ions such as Mg 2+ and Mn 2+ , an activity which is considered as a possible mechanism for its antibacterial action 3 . To analyze mechanisms by which this antibacterial exerts its anticancer activity, several studies screened for specific candidate targets and molecular pathways known to play an important role in cancer biology [7][8][9][10][11][12][13][14][15][16][17][18][19] . Using this approach, disparate targets have been proposed to be responsible for nitroxoline anticancer effects.…”

Nitroxoline: repurposing its antimicrobial to antitumor application

“…The compound was, therefore, evaluated further for its antitumor activity (Sosič et al, 2013;Mitrović et al, 2017). It showed higher activity than did nitroxoline for inhibition of tumor cell invasion and migration in vitro on cell lines in both two-dimensional and three dimensional models as well as in in vivo on tumor mice model compound 17 showed improved inhibition of (Sosič et al, 2013), compound 48 (Bhat et al, 2012) and compound BDF-1253 (Chen et al, 2018).…”

“…In addition a novel series of nitroxoline derivatives with improved potency of inhibition of BET proteins and that bound competitively to the BRD4-BD1, were prepared (Chen et al, 2018;Xing et al, 2019). Structural modifications of nitroxoline derivatives effective as BET inhibitors (Chen et al, 2018;Xing et al, 2019) differed from those reported for cathepsin B inhibition (Mirković et al, 2011;Sosič et al, 2013Sosič et al, , 2018Mitrović et al, 2017). Preparation of the first nitroxoline derivatives for BET inhibition showed that, here, introduction of additional hydroxyl group to the nitroxoline ring had a favorable effect.…”

“…Treatment with the compound BDF-1253 resulted in reduced tumor size and c-Myc expression in vivo on an RCC xenograft mice model. The new derivative also induced cell cycle arrest and apoptosis of RCC cell lines, as well as decreased mRNA levels of downstream effectors of BRD4 which are associated with cancer development, including c-Myc, Bcl-2 and CDK6 (Chen et al, 2018). In another study, a BRD4specific score based virtual screening protocol named BRD4LGR was used to analyze the structure-activity relationship (SAR) and derivative optimization of a series of nitroxoline derivatives with improved permeability and physiochemical properties (Xing et al, 2019).…”