Inhibition of AKR1B10-mediated metabolism of daunorubicin as a novel off-target effect for the Bcr-Abl tyrosine kinase inhibitor dasatinib.

Bcr-Abl tyrosine kinase inhibitors significantly improved Philadelphia chromosome-positive leukaemia therapy. Apart from Bcr-Abl kinase, imatinib, dasatinib, nilotinib, bosutinib and ponatinib are known to have additional off-target effects that might contribute to their antitumoural activities. In our study, we identified aldo-keto reductase 1B10 (AKR1B10) as a novel target for dasatinib. The enzyme AKR1B10 is upregulated in several cancers and influences the metabolism of chemotherapy drugs, including anthracyclines. AKR1B10 reduces anthracyclines to alcohol metabolites that show less antineoplastic properties and tend to accumulate in cardiac tissue. In our experiments, clinically achievable concentrations of dasatinib selectively inhibited AKR1B10 both in experiments with recombinant enzyme (Ki = 0.6 µM) and in a cellular model (IC50 = 0.5 µM). Subsequently, the ability of dasatinib to attenuate AKR1B10-mediated daunorubicin (Daun) resistance was determined in AKR1B10-overexpressing cells. We have demonstrated that dasatinib can synergize with Daun in human cancer cells and enhance its therapeutic effectiveness. Taken together, our results provide new information on how dasatinib may act beyond targeting Bcr-Abl kinase, which may help to design new chemotherapy regimens, including those with anthracyclines.

Selective inhibition of aldo-keto reductase 1C3: a novel mechanism involved in midostaurin and daunorubicin synergism.

Midostaurin is an FMS-like tyrosine kinase 3 receptor (FLT3) inhibitor that provides renewed hope for treating acute myeloid leukaemia (AML). The limited efficacy of this compound as a monotherapy contrasts with that of its synergistic combination with standard cytarabine and daunorubicin (Dau), suggesting a therapeutic benefit that is not driven only by FLT3 inhibition. In an AML context, the activity of the enzyme aldo-keto reductase 1C3 (AKR1C3) is a crucial factor in chemotherapy resistance, as it mediates the intracellular transformation of anthracyclines to less active hydroxy metabolites. Here, we report that midostaurin is a potent inhibitor of Dau inactivation mediated by AKR1C3 in both its recombinant form as well as during its overexpression in a transfected cell model. Likewise, in the FLT3- AML cell line KG1a, midostaurin was able to increase the cellular accumulation of Dau and significantly decrease its metabolism by AKR1C3 simultaneously. The combination of those mechanisms increased the nuclear localization of Dau, thus synergizing its cytotoxic effects on KG1a cells. Our results provide new in vitro evidence of how the therapeutic activity of midostaurin could operate beyond targeting the FLT3 receptor.

Interactions of antileukemic drugs with daunorubicin reductases: could reductases affect the clinical efficacy of daunorubicin chemoregimens?

Although novel anticancer drugs are being developed intensively, anthracyclines remain the gold standard in the treatment of acute myeloid leukaemia (AML). The reductive conversion of daunorubicin (Dau) to less active daunorubicinol (Dau-ol) is an important mechanism that contributes to the development of pharmacokinetic anthracycline resistance. Dau is a key component in many AML regimes, in which it is combined with many drugs, including all-trans-retinoic acid (ATRA), cytarabine, cladribine and prednisolone. In the present study, we investigated the influence of these anticancer drugs on the reductive Dau metabolism mediated by the aldo-keto reductases AKR1A1, 1B10, 1C3, and 7A2 and carbonyl reductase 1 (CBR1). In incubation experiments with recombinant enzymes, cladribine and cytarabine did not significantly inhibit the activity of the tested enzymes. Prednisolone inhibited AKR1C3 with an IC50 of 41.73 µM, while ATRA decreased the activity of AKR1B10 (IC50 = 78.33 µM) and AKR1C3 (IC50 = 1.17 µM). Subsequent studies showed that AKR1C3 inhibition mediated by ATRA exhibited tight binding (Kiapp = 0.54 µM). Further, the combination of 1 µM ATRA with different concentrations of Dau demonstrated synergistic effects in HCT116 and KG1a human cells expressing AKR1C3. Our results suggest that ATRA-mediated inhibition of AKR1C3 can contribute to the mechanisms that are hidden beyond the beneficial clinical outcome of the ATRA-Dau combination.

Buparlisib is a novel inhibitor of daunorubicin reduction mediated by aldo-keto reductase 1C3.

Buparlisib is a pan-class I phosphoinositide 3-kinase (PI3K) inhibitor and is currently under clinical evaluation for the treatment of different cancers. Because PI3K signalling is related to cell proliferation and resistance to chemotherapy, new therapeutic approaches are focused on combining PI3K inhibitors with other anti-cancer therapeutics. Carbonyl-reducing enzymes catalyse metabolic detoxification of anthracyclines and reduce their cytotoxicity. In the present work, the effects of buparlisib were tested on six human recombinant carbonyl-reducing enzymes: AKR1A1, AKR1B1, AKR1B10, AKR1C3, and AKR7A2 from the aldo-keto reductase superfamily and CBR1 from the short-chain dehydrogenase/reductase superfamily, all of which participate in the metabolism of daunorubicin. Buparlisib exhibited the strongest inhibitory effect on recombinant AKR1C3, with a half-maximal inhibitory concentration (IC50) of 9.5 µM. Its inhibition constant Ki was found to be 14.0 µM, and the inhibition data best fitted a mixed-type mode with α = 0.6. The same extent of inhibition was observed at the cellular level in the human colorectal carcinoma HCT 116 cell line transfected with a plasmid encoding the AKR1C3 transcript (IC50 = 7.9 µM). Furthermore, we performed an analysis of flexible docking between buparlisib and AKR1C3 and found that buparlisib probably occupies a part of the binding site for a cofactor most likely via the trifluoromethyl group of buparlisib interacting with catalytic residue Tyr55. In conclusion, our results show a novel PI3K-independent effect of buparlisib that may improve therapeutic efficacy and safety of daunorubicin by preventing its metabolism by AKR1C3.

Roscovitine and purvalanol A effectively reverse anthracycline resistance mediated by the activity of aldo-keto reductase 1C3 (AKR1C3): A promising therapeutic target for cancer treatment.

Members of the short-chain dehydrogenase/reductase (SDR) and aldo-keto reductase (AKR) superfamilies mediate the reduction of anthracyclines to their less potent C-13 alcohol metabolites. This reductive metabolism has been recognized as one of the most important factors that trigger anthracycline resistance in cancer cells. In our study, two purine analogues, purvalanol A and roscovitine, were identified as effective inhibitors of aldo-keto reductase 1C3 (AKR1C3), an enzyme that is overexpressed in many cancer types and is also a key player in tumour cell resistance to anthracyclines. Purvalanol A and roscovitine potently inhibited human recombinant AKR1C3 (Ki = 5.5 µM and 1.4 µM, respectively) and displayed similar activity in experiments with intact cells. Ligand-protein docking calculations suggested that both inhibitors occupied a part of the cofactor-binding site. Furthermore, we demonstrated that the combination of daunorubicin with purvalanol A or roscovitine exhibited a synergistic effect in AKR1C3 overexpressing cells. Based on these findings, it is possible to presume that purvalanol A and roscovitine may have the potential to enhance the therapeutic effectiveness and safety of anthracyclines via inhibition of AKR1C3.

Aldo-keto reductase 1C3 (AKR1C3): a missing piece of the puzzle in the dinaciclib interaction profile.

Dinaciclib is a multi-specific cyclin-dependent kinase (CDK) inhibitor with significant preclinical and clinical activity. It inhibits CDK1, CDK2, CDK5, CDK9 and CDK12 in the nanomolar range and exhibits potent antiproliferative effects on various cancers in vitro and in vivo. Aldo-keto reductases (AKR) and carbonyl reductases (CBR) are enzymes involved at the biosynthesis, intermediary metabolism and detoxification processes, but can also play a significant role in cancer resistance. Here, we report that dinaciclib is a strong inhibitor of aldo-keto reductase 1C3 (AKR1C3), an enzyme that is known to be an important regulator of cell proliferation and differentiation. AKR1C3 is overexpressed in a range of cancer types and is also involved in tumour cell resistance to anthracyclines. In our study, dinaciclib displayed tight-binding inhibition of human recombinant AKR1C3 (Kiapp = 0.07 µM) and was also active at the cellular level (IC50 = 0.23 µM). Dinaciclib acts as a noncompetitive inhibitor with respect to daunorubicin and as an uncompetitive inhibitor with respect to the NADPH. In subsequent experiments, pretreatment with dinaciclib (0.1 µM) significantly sensitized AKR1C3-overexpressing anthracycline-resistant cancer cells to daunorubicin. In conclusion, our results indicate that dinaciclib may potentially increase the therapeutic efficacy and safety of anthracyclines by preventing anthracycline resistance and minimizing their adverse effects.

Tacrine-Trolox Hybrids: A Novel Class of Centrally Active, Nonhepatotoxic Multi-Target-Directed Ligands Exerting Anticholinesterase and Antioxidant Activities with Low In Vivo Toxicity.

Coupling of two distinct pharmacophores, tacrine and trolox, endowed with different biological properties, afforded 21 hybrid compounds as novel multifunctional candidates against Alzheimer's disease. Several of them showed improved inhibitory properties toward acetylcholinesterase (AChE) in relation to tacrine. These hybrids also scavenged free radicals. Molecular modeling studies in tandem with kinetic analysis exhibited that these hybrids target both catalytic active site as well as peripheral anionic site of AChE. In addition, incorporation of the moiety bearing antioxidant abilities displayed negligible toxicity on human hepatic cells. This striking effect was explained by formation of nontoxic metabolites after 1 h incubation in human liver microsomes system. Finally, tacrine-trolox hybrids exhibited low in vivo toxicity after im administration in rats and potential to penetrate across blood-brain barrier. All of these outstanding in vitro results in combination with promising in vivo outcomes highlighted derivative 7u as the lead structure worthy of further investigation.