AKR1C Isoforms Represent a Novel Cellular Target for Jasmonates alongside Their Mitochondrial-Mediated Effects

Bioactivity profiling of Sanghuangporus lonicerinus: antioxidant, hypoglycaemic, and anticancer potential via in-vitro and in-silico approaches

This study investigates the mycochemical profile and biological activities of hydroethanolic (EtOH), chloroform (CHCl3), and hot water (H2O) extracts of Sanghuangporus lonicerinus from Uzbekistan. Antioxidant capacity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), NO, and FRAP assays, and in vitro hypoglycaemic effects were evaluated through α-amylase and α-glucosidase inhibition. Antiproliferative potential was explored by analysing the binding affinities of EtOH and H2O extracts to estrogen receptor α (ERα), ERβ, androgen receptor (AR), and glucocorticoid receptor (GR), with molecular docking providing structural insights. LC-MS/MS analysis revealed solvent-dependent phenolic profiles, with the EtOH extract containing the highest total phenolic content (143.15 ± 6.70 mg GAE/g d.w.) and the best antioxidant capacity. The EtOH extract showed significant hypoglycaemic effects, with 85.29 ± 5.58% inhibition of α-glucosidase and 41.21 ± 0.79% inhibition of α-amylase. Moderate ERβ binding suggests potential for estrogen-mediated cancer therapy, while strong AKR1C3 inhibition by the EtOH extract supports its therapeutic potential.

Coumarin-Based Aldo-Keto Reductase Family 1C (AKR1C) 2 and 3 Inhibitors

A series of 7-substituted coumarin derivatives have been characterized as pan-aldo-keto reductase family 1C (AKR1C) inhibitors. The AKR1C family of enzymes are overexpressed in numerous cancers where they are involved in drug resistance development. 7-hydroxy coumarin ethyl esters and their corresponding amides have high potency for AKR1C3 and AKR1C2 inhibition. Coumarin amide 3 a possessed IC50 values of 50 nM and 90 nM for AKR1C3 and AKR1C2, respectively, and exhibits 'drug-like' metabolic stability and half-life in human and mouse liver microsomes and plasma. Compound 3 a was employed as a chemical tool to determine pan-AKR1C2/3 inhibition effects both as a radiation sensitizer and as a potentiator of chemotherapy cytotoxicity. In contrast to previously reported pan-AKR1C inhibitors, 3 a demonstrated no radiation sensitization effect in a radiation-resistant prostate cancer cell line model. Pan-AKR1C inhibition also did not potentiate the in vitro cytotoxicity of ABT-737, daunorubicin or dexamethasone, in two patient-derived T-cell ALL and pre-B-cell ALL cell lines. In contrast, a highly selective AKR1C3 inhibitor, compound K90, enhanced the cytotoxicity of both ABT-737 and daunorubicin in the T-cell ALL cell line model. Thus, the inhibitory profile required to enhance chemotherapeutic cytotoxicity in leukemia may be AKR1C isoform and drug specific.

Synthesis and biological evaluation of novel D-ring fused steroidal N(2)-substituted-1,2,3-triazoles

In this study, a series of 13 new D-ring fused steroidal N(2)-substituted-1,2,3-triazoles were synthesized, characterized and evaluated for their biological activities. The relative binding affinities of the synthesized compounds for the ligand-binding domains of estrogen receptors α and β, androgen receptor and glucocorticoid receptor demonstrated that androstane derivatives 3a and 3h and estratriene derivative 4e showed highly specific and strong binding affinity for estrogen receptor β, while 3b, 3e, 4a and 4b displayed high binding affinity for the glucocorticoid receptor. The synthesized compounds were tested for their ability to inhibit aldo-keto reductases 1C3 and 1C4 in vitro by monitoring NADPH consumption using fluorescence spectroscopy. The most potent aldo-keto reductase 1C3 inhibitors were compounds 3h (71.17%) and 3f (69.9%). Moreover, a molecular docking study was carried out for compounds 3f and 3h against aldo-keto reductase 1C3 and results showed that compounds 3h and 3f could bind in the same site and orientation as EM1404. However, polar atoms in the triazole group enable additional hydrogen bonding deeper in SP1 with Tyr319, Tyr216 and the NADP+ cofactor, which are not visible in the AKR1C3-EM1404 crystal structure. The synthesized compounds were screened for their anticancer activity against four cancer cell lines. Compound 3f demonstrated moderate toxic effects across various cancer types, while displaying lower toxicity towards the healthy cell line. In summary, our findings indicate that N(2)-substituted-1,2,3-triazoles are high-affinity ligands for estrogen receptor β and glucocorticoid receptor, inhibitors of aldo-keto reductase 1C3 enzyme, and exhibit antiproliferative effects against cancer cells, suggesting that they could serve as scaffolds for anticancer drug development.

Development of new steroid-based hydrazide and (thio)semicarbazone compounds with anticancer properties

Most breast and prostate cancers are caused by abnormal production or action of steroidal hormones. Hormonal drugs based on steroid scaffolds represent a significant class of chemotherapeutics that are routinely used in chemotherapy. In this study, the synthesis of new 17a-homo lactone and 17α-(pyridine-2-ylmethyl) androstane derivatives with hydrazide and semicarbazone motifs is presented. All compounds were screened for their effect on cell viability against a panel of five cancer cell lines and one healthy cell line. Two compounds showed significant cytotoxicity against cancer cells, with low toxicity against healthy cells. The relative binding affinities of compounds for the ligand-binding domains of estrogen receptor α, estrogen receptor β, androgen receptor and glucocorticoid receptor were tested using a fluorescence screen in yeast. Potential for inhibition of aldo-keto reductase 1C3 and 1C4 activity was measured in vitro. Experimental results are analyzed in the context of molecular docking simulations. Our results could help guide design of steroid compounds with improved anticancer properties against androgen- and estrogen-dependent cancers.

AKR1C4 regulates the sensitivity of colorectal cancer cells to chemotherapy through ferroptosis modulation

PURPOSE

Colorectal cancer (CRC) remains a major global health concern, necessitating innovative therapeutic strategies to enhance treatment efficacy. In this study, we investigated the role of AKR1C4 in CRC and its impact on chemotherapy response.

METHODS

AKR1C4 stable knockout CRC cell lines were generated using CRISPR/Cas9 technology. The impact of AKR1C4 depletion on chemotherapy sensitivity was assessed using Sulforhodamine B assay. Long-term, low-dose drug induction with increasing concentrations of 5FU, irinotecan, and oxaliplatin were employed to establish acquired chemoresistant CRC cell lines. Ferroptosis induction and inhibition were examined through total iron content and lipid peroxidation measurements.

RESULTS

We found that AKR1C4 knockout enhances CRC cell sensitivity to chemotherapy, specifically by inducing ferroptosis. The enzymatic activity of AKR1C4 is crucial for regulating chemotherapy sensitivity in CRC cells, as evidenced by the inability of a Y55A mutant to reverse the sensitizing effect. Additionally, AKR1C4 inhibitors enhance chemotherapy sensitivity by inducing ferroptosis. Notably, AKR1C4 depletion resensitizes the acquired chemoresistant CRC cells to chemotherapy, suggesting its potential as a therapeutic target for overcoming acquired chemoresistance. Clinical analysis reveals that high AKR1C4 expression is associated with poor prognosis in CRC patients undergoing chemotherapy, highlighting its significance as a prognostic marker and a potential target for therapeutic intervention.

CONCLUSION

This study illuminates the multifaceted role of AKR1C4 in CRC, demonstrating its significance in regulating chemotherapy sensitivity, overcoming acquired resistance, and impacting clinical outcomes. The insights provided may pave the way for novel therapeutic strategies in CRC management.

Synthesis, in vitro and in silico anticancer evaluation of novel pyridin-2-yl estra-1,3,5(10)-triene derivatives

Aim: The aim of this study was the synthesis of steroid compounds with heterocyclic rings and good anticancer properties. Materials & methods: The synthesis, in silico and in vitro anticancer testing of novel pyridin-2-yl estra-1,3,5(10)-triene derivatives was performed. Results: All synthesized compounds have shown promising results for, antiproliferative activity, relative binding affinities for the ligand binding domains of estrogen receptors α, β and androgen receptor, aromatase binding potential, and inhibition of AKR1C3 enzyme. Conclusion: 3-Benzyloxy (17E)-pycolinilidene derivative 9 showed the best antitumor potential against MDA-MB-231 cell line, an activity that can be explained by its moderate inhibition of AKR1C3. Molecular docking simulation indicates that it binds to AKR1C3 in a very similar orientation and geometry as steroidal inhibitor EM1404.

AKR1C3 in carcinomas: from multifaceted roles to therapeutic strategies

Aldo-Keto Reductase Family 1 Member C3 (AKR1C3), also known as type 5 17β-hydroxysteroid dehydrogenase (17β-HSD5) or prostaglandin F (PGF) synthase, functions as a pivotal enzyme in androgen biosynthesis. It catalyzes the conversion of weak androgens, estrone (a weak estrogen), and PGD2 into potent androgens (testosterone and 5α-dihydrotestosterone), 17β-estradiol (a potent estrogen), and 11β-PGF2α, respectively. Elevated levels of AKR1C3 activate androgen receptor (AR) signaling pathway, contributing to tumor recurrence and imparting resistance to cancer therapies. The overexpression of AKR1C3 serves as an oncogenic factor, promoting carcinoma cell proliferation, invasion, and metastasis, and is correlated with unfavorable prognosis and overall survival in carcinoma patients. Inhibiting AKR1C3 has demonstrated potent efficacy in suppressing tumor progression and overcoming treatment resistance. As a result, the development and design of AKR1C3 inhibitors have garnered increasing interest among researchers, with significant progress witnessed in recent years. Novel AKR1C3 inhibitors, including natural products and analogues of existing drugs designed based on their structures and frameworks, continue to be discovered and developed in laboratories worldwide. The AKR1C3 enzyme has emerged as a key player in carcinoma progression and therapeutic resistance, posing challenges in cancer treatment. This review aims to provide a comprehensive analysis of AKR1C3's role in carcinoma development, its implications in therapeutic resistance, and recent advancements in the development of AKR1C3 inhibitors for tumor therapies.

Aldo-Keto Reductase 1C15 Characterization and Protection in Ischemic Brain Injury

Aldo-keto reductase (AKR) 1C15, a member of the AKR superfamily, was recently identified and cloned, and reported to alleviate oxidative stress in endothelial cells in rodent lungs. However, its expression and role in the brain and ischemic brain diseases have not been investigated. AKR1C15 expression was detected with real-time PCR. Mouse ischemic stroke and ischemic preconditioning (IPC) were established with middle cerebral artery occlusion (MCAO) for 1 h or 12 min, respectively. Recombinant AKR1C15 was administered intraperitoneally, and stroke outcome was evaluated with neurobehavioral tests and infarct volumes. Rat primary brain cell cultures were subjected to oxygen-glucose deprivation (OGD) to mimic ischemic injury. Cell survival or in vitro blood-brain barrier (BBB) permeability was measured, and nitric oxide (NO) release was detected. Immunostaining and Western blotting were used to evaluate oxidative-stress-related protein expression. AKR1C15 administration decreased the infarct volume and neurological deficits 2d post-stroke, and its early (1-h) administration after IPC abolished the protection of IPC against stroke. In rat primary brain cell cultures, AKR1C15 was most abundantly expressed in brain microvascular endothelial cells (BMVECs) and microglia. Its expression decreased upon OGD in most cell types except for BMVECs and microglia. In primary neuronal cultures, AKR1C15 treatment prevented OGD-induced cell death accompanied by decreased levels of 4-hydroxynonenal, 8-hydroxy-2'-deoxyguanosine, and heme oxygenase-1. In BMVEC cultures, AKR1C15 treatment protected against OGD-induced cell death and in vitro BBB leakage. In primary microglial cultures, AKR1C15 reduced the release of NO upon proinflammatory stimulation. Our results provide a characterization of the novel antioxidant AKR1C15 and demonstrate its protective role against ischemic injury, both in vivo and in vitro. AKR1C15 may be a promising agent for ischemic stroke treatment.

Development of highly potent and specific AKR1C3 inhibitors to restore the chemosensitivity of drug-resistant breast cancer

Aldo-keto reductase 1C3 (AKR1C3) is overexpressed in multiple hormone related cancers, such as breast and prostate cancer, and is correlated with tumor development and aggressiveness. As a phase I biotransformation enzyme, AKR1C3 catalyzes the metabolic processes that lead to resistance to anthracyclines, the "gold standard" for breast cancer treatment. Novel approaches to restore the chemotherapy sensitivity of breast cancer are urgently required. Herein, we developed a new class of AKR1C3 inhibitors that demonstrated potent inhibitory activity and exquisite selectivity for closely related isoforms. The best derivative 27 (S19-1035) exhibits an IC₅₀ value of 3.04 nM for AKR1C3 and >3289-fold selectivity over other isoforms. We determined the co-crystal structures of AKR1C3 with three of the inhibitors, providing a solid foundation for further structure-based drug optimization. Co-administration of these AKR1C3 inhibitors significantly reversed the doxorubicin (DOX) resistance in a resistant breast cancer cell line. Therefore, the novel AKR1C3 specific inhibitors developed in this work may serve as effective adjuvants to overcome DOX resistance in breast cancer treatment.

Immunofluorescence Detection of Plasma Membranous PTEN in Cultured Cells

PTEN is a well-known tumor suppressor with various functions that depend on its intracellular localization. Green fluorescent protein (GFP)-tagged live-cell images clarified the crucial amino acids needed to regulate the localization of PTEN in cells. However, it currently remains unknown whether GFP itself affects the intracellular localization of PTEN and its mutants, and the establishment of fixed-cell imaging is important for identifying the exact location of PTEN in cells. I herein investigated a number of immunofluorescence strategies for cell fixation, membrane permeabilization, and antigen retrieval. Permeabilization by detergents was necessary to observe nuclear and cytosolic PTEN in paraformaldehyde (PFA)-fixed cells; however, this permeabilization was not always valid. On the other hand, antigen retrieval by the pre-boiled EDTA treatment was useful for detecting plasma membranous PTEN in PFA-fixed cells in the same manner as in in vivo studies. Furthermore, methanol-fixed images of PTEN were consistent with GFP-tagged live-cell images. Two immunofluorescence methods (the PFA-fixed/pre-boiled EDTA treatment and methanol fixation) are applicable to investigations of the intracellular localization of PTEN without a GFP tag in cultured cells. In conclusion, live-cell imaging and appropriate immunofluorescence including a novel antigen retrieval treatment were both useful for detecting the cellular localization of PTEN, particularly at the plasma membrane.

Design, Synthesis and Cytotoxicity Evaluation of Novel Indole Derivatives Containing Benzoic Acid Group as Potential AKR1C3 Inhibitors

Castration-resistant prostate cancer (CRPC) is a fatal, metastatic form of prostate cancer, characterized by reactivation of the androgen axis. Aldo-keto reductase 1C3 (AKR1C3) converts androstenedione (AD) and 5α-androstanedione to testosterone (T) and 5α-dihydrotestosterone (DHT), respectively. In CRPC, AKR1C3 is upregulated and implicated in drug resistance and has been regarded as a potential therapeutic target. Here we examined a series of indole derivatives containing benzoic acid or phenylhydroxamic acid and found that 4-({3-[(3,4,5-trimethoxyphenyl)sulfanyl]-1H-indol-1-yl}methyl)benzoic acid (3e) and N-hydroxy-4-({3-[(3,4,5-trimethoxyphenyl)sulfanyl]-1H-indol-1-yl}methyl)benzamide (3q) inhibited 22Rv1 cell proliferation with IC₅₀ values of 6.37 μM and 2.72 μM, respectively. In enzymatic assay, compounds 3e and 3q exhibited potent inhibitory effect against AKR1C3 (IC₅₀ =0.26 and 2.39 μM, respectively). These results indicated that compounds 3e and 3q might be useful leads for further investigation of more potential AKR1C3 inhibitors used for CRPC.

Dual Inhibitory Action of a Novel AKR1C3 Inhibitor on Both Full-Length AR and the Variant AR-V7 in Enzalutamide Resistant Metastatic Castration Resistant Prostate Cancer

The expanded use of second-generation antiandrogens revolutionized the treatment landscape of progressed prostate cancer. However, resistances to these novel drugs are already the next obstacle to be solved. Various previous studies depicted an involvement of the enzyme AKR1C3 in the process of castration resistance as well as in the resistance to 2nd generation antiandrogens like enzalutamide. In our study, we examined the potential of natural AKR1C3 inhibitors in various prostate cancer cell lines and a three-dimensional co-culture spheroid model consisting of cancer cells and cancer-associated fibroblasts (CAFs) mimicking enzalutamide resistant prostate cancer. One of our compounds, named MF-15, expressed strong antineoplastic effects especially in cell culture models with significant enzalutamide resistance. Furthermore, MF-15 exhibited a strong effect on androgen receptor (AR) signaling, including significant inhibition of AR activity, downregulation of androgen-regulated genes, lower prostate specific antigen (PSA) production, and decreased AR and AKR1C3 expression, indicating a bi-functional effect. Even more important, we demonstrated a persisting inhibition of AR activity in the presence of AR-V7 and further showed that MF-15 non-competitively binds within the DNA binding domain of the AR. The data suggest MF-15 as useful drug to overcome enzalutamide resistance.

Reactive Oxygen Species Scavenging and Biodegradable Peptide Hydrogel as 3D Culture Scaffold for Cardiomyocytes

Myocardial ischemia-reperfusion produces a large amount of reactive oxygen species (ROS), which damage the myocardial tissue. Therefore, localized scavenging of ROS from the myocardial tissue would reduce its damage and avoid metabolic abnormalities caused by systemic ROS. In this study, a free radical scavenging and biodegradable supramolecular peptide (ECAFF, named as ECF-5) hydrogel was designed as a culture scaffold for cardiomyocytes. The peptide hydrogel significantly preserved the migration and proliferation of cardiomyocytes and reduced their damage from oxidative stress. In addition, the hydrogel degraded during cell growth, which implies that it may avoid thrombosis of the capillaries in practical use and provide the opportunity for the cells to attach to each other and form a functional tissue. The hydrogel can be used as a 3D culture scaffold for cardiomyocyte culture and allow cardiomyocytes to grow into tissue-like cell spheres. The excellent nature of the ECF-5 hydrogel enables it to have broad applications in the biomedical field in the future.

Overview of AKR1C3: Inhibitor Achievements and Disease Insights

Human aldo-keto reductase family 1 member C3 (AKR1C3) is known as a hormone activity regulator and prostaglandin F (PGF) synthase that regulates the occupancy of hormone receptors and cell proliferation. Because of the overexpression in metabolic diseases and various hormone-dependent and -independent carcinomas, as well as the emergence of clinical drug resistance, an increasing number of studies have investigated AKR1C3 inhibitors. Here, we briefly review the physiological and pathological function of AKR1C3 and then summarize the recent development of selective AKR1C3 inhibitors. We propose our viewpoints on the current problems associated with AKR1C3 inhibitors with the aim of providing a reference for future drug discovery and potential therapeutic perspectives on novel, potent, selective AKR1C3 inhibitors.

Potent and Highly Selective Aldo-Keto Reductase 1C3 (AKR1C3) Inhibitors Act as Chemotherapeutic Potentiators in Acute Myeloid Leukemia and T-Cell Acute Lymphoblastic Leukemia

Aldo-keto reductase 1C3 (AKR1C3) catalyzes the synthesis of 9α,11β-prostaglandin (PG) F_2α and PGF_2α prostanoids that sustain the growth of myeloid precursors in the bone marrow. The enzyme is overexpressed in acute myeloid leukemia (AML) and T-cell acute lymphoblastic leukemia (T-ALL). Moreover, AKR1C3 confers chemotherapeutic resistance to the anthracyclines: first-line agents for the treatment of leukemias. The highly homologous isoforms AKR1C1 and AKR1C2 inactivate 5α-dihydrotestosterone, and their inhibition would be undesirable. We report herein the identification of AKR1C3 inhibitors that demonstrate exquisite isoform selectivity for AKR1C3 over the other closely related isoforms to the order of >2800-fold. Biological evaluation of our isoform-selective inhibitors revealed a high degree of synergistic drug action in combination with the clinical leukemia therapeutics daunorubicin and cytarabine in in vitro cellular models of AML and primary patient-derived T-ALL cells. Our developed compounds exhibited >100-fold dose reduction index that results in complete resensitization of a daunorubicin-resistant AML cell line to the chemotherapeutic and >100-fold dose reduction of cytarabine in both AML cell lines and primary T-ALL cells.

Identification of key genes and specific pathways potentially involved in androgen-independent, mitoxantrone-resistant prostate cancer

Background

Resistance to mitoxantrone (MTX), an anthracenedione antineoplastic agent used in advanced and metastatic androgen-refractory prostate cancer (PCa), seriously limits therapeutic success.

Methods

Xenografts from two human PCa cell lines (VCaP and CWR22) were established in male severe combined immunodeficiency mice, and MTX was administered, with or without concurrent castration, three times a week until tumors relapsed. Microarray technology was used to screen for differentially expressed genes (DEGs) in androgen-independent, MTX-resistant PCa xenografts. Gene expression profiles of MTX-treatment xenografts and their respective parental cell lines were performed using an Agilent whole human genome oligonucleotide microarray and analyzed using Ingenuity Pathway Analysis software.

Results

A total of 636 genes were differentially expressed (fold change ≥1.5; P<0.05) in MTX-resistant castration-resistant prostate cancer (CRPC) xenografts. Of these, 18 were selected to be validated and showed that most of these genes exhibited a transcriptional profile similar to that seen in the microarray (Pearson’s r=0.87). Western blotting conducted with a subset of genes deregulated in MTX-resistant CRPC tumors was shown through network analysis to be involved in androgen synthesis, drug efflux, ATP synthesis, and vascularization.

Conclusion

The present data provide insight into the genetic alterations underlying MTX resistance in androgen-independent PCa and highlight potential targets to improve therapeutic outcomes.

Methyl jasmonate enhances the radiation sensitivity of esophageal carcinoma cells by inhibiting the 11-ketoprostaglandin reductase activity of AKR1C3

Purpose

In our previous study, we found that AKR1C3 was a radioresistance gene in KY170R cells. Downregulating the expression of AKR1C3 could enhance the radiosensitivity of esophageal carcinoma cells. In this study, we investigated whether methyl jasmonate (MeJ), an inhibitor of Aldo-keto reductase family1 member C3 (AKR1C3), could overcome radiation resistance in AKR1C3 highly expressed cells.

Patients and methods

We used clone formation assays to detect radiosensitivity effects. Flow cytometry assays were used to detect reactive oxygen species (ROS) accumulation and apoptosis. Enzyme linked immunosorbent assays (ELISAs) were used to detect the concentrations of prostaglandin F2 (PGF2) and prostaglandin D2 (PGD2) in the cells after incubation with MeJ. Western blotting was used to detect AKR1C3 and peroxisome proliferator-activated receptor gamma (PPARγ) expression.

Results

We found that AKR1C3 was highly expressed in radioresistant esophageal carcinoma cells. MeJ inhibited the expression of AKR1C3 and enhanced the radiation sensitivity of esophageal carcinoma cells expressing high levels of AKR1C3 (P<0.05). MeJ could inhibit the 11-ketoprostaglandin reductase activity of AKR1C3 in a dose-dependent manner in KY170R cells. Incubation of KY170R cells with 200 µmol/L of MeJ for 24 h reduced the expression of PGF2 by roughly 30% (P<0.05). The PPAR pathway inhibitor GW9662 prevented the radiation sensitivity enhancement imparted by MeJ. After adding GW9662, there were no significant differences between the radiation sensitivities of MeJ-treated and -untreated KY170R cells (P>0.05). The radiation sensitivity effect of MeJ also depended upon the generation of ROS in KY170R cells; 48 h after irradiation, ROS levels in the MeJ group was twofold higher than in the untreated KY170R cells (P<0.05). The ROS scavenger, N-acetyl cysteine, could reverse the radiosensitivity effects of MeJ (P>0.05).

Conclusion

Our results indicate that MeJ can increase the radiation sensitivity of AKR1C3-overexpressing KY170R cells by inhibiting the 11-ketoprostaglandin reductase activity of AKR1C3 and increasing cellular ROS levels.

AKR1C3 Inhibitor KV-37 Exhibits Antineoplastic Effects and Potentiates Enzalutamide in Combination Therapy in Prostate Adenocarcinoma Cells

Aldo-keto reductase 1C3 (AKR1C3), also known as type 5 17 β-hydroxysteroid dehydrogenase, is responsible for intratumoral androgen biosynthesis, contributing to the development of castration-resistant prostate cancer (CRPC) and eventual chemotherapeutic failure. Significant upregulation of AKR1C3 is observed in CRPC patient samples and derived CRPC cell lines. As AKR1C3 is a downstream steroidogenic enzyme synthesizing intratumoral testosterone (T) and 5α-dihydrotestosterone (DHT), the enzyme represents a promising therapeutic target to manage CRPC and combat the emergence of resistance to clinically employed androgen deprivation therapy. Herein, we demonstrate the antineoplastic activity of a potent, isoform-selective and hydrolytically stable AKR1C3 inhibitor (E)-3-(4-(3-methylbut-2-en-1-yl)-3-(3-phenylpropanamido)phenyl)acrylic acid (KV-37), which reduces prostate cancer cell growth in vitro and in vivo and sensitizes CRPC cell lines (22Rv1 and LNCaP1C3) toward the antitumor effects of enzalutamide. Crucially, KV-37 does not induce toxicity in nonmalignant WPMY-1 prostate cells nor does it induce weight loss in mouse xenografts. Moreover, KV-37 reduces androgen receptor (AR) transactivation and prostate-specific antigen expression levels in CRPC cell lines indicative of a therapeutic effect in prostate cancer. Combination studies of KV-37 with enzalutamide reveal a very high degree of synergistic drug interaction that induces significant reduction in prostate cancer cell viability via apoptosis, resulting in >200-fold potentiation of enzalutamide action in drug-resistant 22Rv1 cells. These results demonstrate a promising therapeutic strategy for the treatment of drug-resistant CRPC that invariably develops in prostate cancer patients following initial treatment with AR antagonists such as enzalutamide. Mol Cancer Ther; 17(9); 1833-45. ©2018 AACR.

Evaluation of A-ring fused pyridine d-modified androstane derivatives for antiproliferative and aldo-keto reductase 1C3 inhibitory activity

New A-ring pyridine fused androstanes in 17a-homo-17-oxa (d-homo lactone), 17α-picolyl or 17(E)-picolinylidene series were synthesized and validated by X-ray crystallography, HRMS, IR and NMR spectroscopy. Novel compounds 3, 5, 8 and 12 were prepared by treatment of 4-en-3-one or 4-ene-3,6-dione d-modified androstane derivatives with propargylamine catalyzed by Cu(ii), and evaluated for potential anticancer activity in vitro using human cancer cell lines and recombinant targets of steroidal anti-cancer drugs. Pyridine fusion to position 3,4 of the A-ring may dramatically enhance affinity of 17α-picolyl compounds for CYP17 while conferring selective antiproliferative activity against PC-3 cells. Similarly, pyridine fusion to the A-ring of steroidal d-homo lactones led to identification of new inhibitors of aldo-keto reductase 1C3, an enzyme targeted in acute myeloid leukemia, breast and prostate cancers. One A-pyridine d-lactone steroid 5 also has selective submicromolar antiproliferative activity against HT-29 colon cancer cells. None of the new derivatives have affinity for estrogen or androgen receptors in a yeast screen, suggesting negligible estrogenicity and androgenicity. Combined, our results suggest that A-ring pyridine fusions have potential in modulating the anticancer activity of steroidal compounds.

AKR1C enzymes sustain therapy resistance in paediatric T-ALL

Background

Despite chemotherapy intensification, a subgroup of high-risk paediatric T-cell acute lymphoblastic leukemia (T-ALL) patients still experience treatment failure. In this context, we hypothesised that therapy resistance in T-ALL might involve aldo-keto reductase 1C (AKR1C) enzymes as previously reported for solid tumors.

Methods

Expression of NRF2-AKR1C signaling components has been analysed in paediatric T-ALL samples endowed with different treatment outcomes as well as in patient-derived xenografts of T-ALL. The effects of AKR1C enzyme modulation has been investigated in T-ALL cell lines and primary cultures by combining AKR1C inhibition, overexpression, and gene silencing approaches.

Results

We show that T-ALL cells overexpress AKR1C1-3 enzymes in therapy-resistant patients. We report that AKR1C1-3 enzymes play a role in the response to vincristine (VCR) treatment, also ex vivo in patient-derived xenografts. Moreover, we demonstrate that the modulation of AKR1C1-3 levels is sufficient to sensitise T-ALL cells to VCR. Finally, we show that T-ALL chemotherapeutics induce overactivation of AKR1C enzymes independent of therapy resistance, thus establishing a potential resistance loop during T-ALL combination treatment.

Conclusions

Here, we demonstrate that expression and activity of AKR1C enzymes correlate with response to chemotherapeutics in T-ALL, posing AKR1C1-3 as potential targets for combination treatments during T-ALL therapy.

Modulation of microglial functions by methyl jasmonate

Neuroinflammation contributes to the neurodegenerative processes in Alzheimer’s disease (AD); therefore, characterization of novel drug candidates aimed at combatting inflammation in the central nervous system is one of the potential avenues for the development of effective AD treatment and prevention strategies. Non-neuronal microglial cells orchestrate neuroinflammatory reactions, and their adverse activation has been linked to AD pathogenesis. Methyl jasmonate (MJ) has anti-cancer properties and has also been shown to reduce peripheral inflammation in pre-clinical models. Recently, anti-neuroinflammatory activity of MJ was demonstrated in mice, but the exact cellular and molecular mechanisms responsible for this beneficial effect are unknown. We hypothesized that MJ can regulate select microglial functions, and used two different in vitro models of microglia to test this hypothesis. MJ inhibited the production of damaging reactive oxygen species by differentiated human HL-60 promyelocytic leukemia cells without reducing their viability. MJ also selectively upregulated phagocytic activity of murine BV-2 microglia, but had no effect on nitric oxide secretion by these cells. Since microglial phagocytosis can be beneficial for clearance of amyloid β aggregates in AD, the observed upregulation of phagocytic activity by MJ, combined with its inhibitory effect on reactive oxygen species production, supports continued studies of MJ as a candidate drug for managing adverse neuroinflammation in AD.

Elevated expression of AKR1C3 increases resistance of cancer cells to ionizing radiation via modulation of oxidative stress

With the aim to elucidate the etiology of radioresistance, we explored the genetic alterations in non-radioresistant vs. resistant esophageal cancer cells acquired by long-term fractionated radiation. We found AKR1C3, an aldo-keto reductase expressed seldom in most human tissues, expressed higher in radioresistance-acquired cells. Suppression of AKR1C3 via RNAi or its chemical inhibitors restored the sensitivity of the acquired tumor cells and xenograft BALB/c nude mice to ionizing radiation (IR). Cellular monitoring of the oxidative stress in the AKR1C3-elevated cells indicated that IR-induced ROS accumulation and the concomitant DNA damage was significantly alleviated, and such protective consequence disappeared upon AKR1C3 knockdown. These findings uncover the potential involvement of AKR1C3 in removal of cellular ROS and explain, at least partially, the acquired radioresistance by AKR1C3 overexpression. A retrospective analysis of esophageal carcinomas also indicated a significant expression of AKR1C3 in radio-resistant but not radio-sensitive surgical samples. Our study may provide a potential biomarker for predicting prognosis of radiotherapy and even direct a targeted therapy for esophageal cancer and other tumors.

Selective AKR1C3 inhibitors do not recapitulate the anti-leukaemic activities of the pan-AKR1C inhibitor medroxyprogesterone acetate

Background:

We and others have identified the aldo-keto reductase AKR1C3 as a potential drug target in prostate cancer, breast cancer and leukaemia. As a consequence, significant effort is being invested in the development of AKR1C3-selective inhibitors.

Methods:

We report the screening of an in-house drug library to identify known drugs that selectively inhibit AKR1C3 over the closely related isoforms AKR1C1, 1C2 and 1C4. This screen initially identified tetracycline as a potential AKR1C3-selective inhibitor. However, mass spectrometry and nuclear magnetic resonance studies identified that the active agent was a novel breakdown product (4-methyl(de-dimethylamine)-tetracycline (4-MDDT)).

Results:

We demonstrate that, although 4-MDDT enters AML cells and inhibits their AKR1C3 activity, it does not recapitulate the anti-leukaemic actions of the pan-AKR1C inhibitor medroxyprogesterone acetate (MPA). Screens of the NCI diversity set and an independently curated small-molecule library identified several additional AKR1C3-selective inhibitors, none of which had the expected anti-leukaemic activity. However, a pan AKR1C, also identified in the NCI diversity set faithfully recapitulated the actions of MPA.

Conclusions:

In summary, we have identified a novel tetracycline-derived product that provides an excellent lead structure with proven drug-like qualities for the development of AKR1C3 inhibitors. However, our findings suggest that, at least in leukaemia, selective inhibition of AKR1C3 is insufficient to elicit an anticancer effect and that multiple AKR1C inhibition may be required.

Methyl jasmonate: putative mechanisms of action on cancer cells cycle, metabolism, and apoptosis

Methyl jasmonate (MJ), an oxylipid that induces defense-related mechanisms in plants, has been shown to be active against cancer cells both in vitro and in vivo, without affecting normal cells. Here we review most of the described MJ activities in an attempt to get an integrated view and better understanding of its multifaceted modes of action. MJ (1) arrests cell cycle, inhibiting cell growth and proliferation, (2) causes cell death through the intrinsic/extrinsic proapoptotic, p53-independent apoptotic, and nonapoptotic (necrosis) pathways, (3) detaches hexokinase from the voltage-dependent anion channel, dissociating glycolytic and mitochondrial functions, decreasing the mitochondrial membrane potential, favoring cytochrome c release and ATP depletion, activating pro-apoptotic, and inactivating antiapoptotic proteins, (4) induces reactive oxygen species mediated responses, (5) stimulates MAPK-stress signaling and redifferentiation in leukemia cells, (6) inhibits overexpressed proinflammatory enzymes in cancer cells such as aldo-keto reductase 1 and 5-lipoxygenase, and (7) inhibits cell migration and shows antiangiogenic and antimetastatic activities. Finally, MJ may act as a chemosensitizer to some chemotherapics helping to overcome drug resistant. The complete lack of toxicity to normal cells and the rapidity by which MJ causes damage to cancer cells turn MJ into a promising anticancer agent that can be used alone or in combination with other agents.

Clinical implications of aldo-keto reductase family 1 member C3 and its relationship with lipocalin 2 in cancer of the uterine cervix

OBJECTIVE

Over-expression of the aldo-keto reductase family 1 member C3 (AKR1C3) has been demonstrated in many human cancers. Lipocalin 2 (LCN2) is reported to inhibit cervical cancer metastasis but little is known regarding its relationship with AKR1C3 in the development and progression of uterine cervical cancer. This study aimed to investigate the involvement of AKR1C3 and its relationship with LCN2 in cervical cancer.

METHODS

The roles of AKR1C3 and LCN2 were investigated using the lentivirus shRNA system in SiHa and Caski cervical cancer cells. LCN2 and matrix metalloproteinase-2 (MMP-2) promoters were constructed to demonstrate transcriptional regulation by shAKR1C3 and shLCN2, respectively. The influences of metastatic phenotypes were analyzed by wound healing, Boyden chamber, and immunofluorescence assays. The activity of MMP-2 was determined by zymography assay. The impacts of AKR1C3 and LCN2 on patient prognosis were evaluated using tissue microarrays by Cox regression and Kaplan-Meier models.

RESULTS

Silencing of the AKR1C3 gene increased the expression of LCN2 and decreased the migratory and invasive abilities and changed the cytoskeleton of cervical cancer cells. When AKR1C3 was over-expressed, it decreased LCN2 promoter activity and LCN2 expression and increased cell migration. The mRNA level and enzyme activity of MMP-2 increased in silenced LCN2 cells. Positive AKR1C3 and negative LCN2 were correlated with higher recurrence and poorer survival of cervical cancer patients.

CONCLUSIONS

Silencing of AKR1C3 increases LCN2 expression and inhibits metastasis in cervical cancer. Both AKR1C3 and LCN2 serve as molecular targets for cancer therapy to improve the clinical outcome of cervical cancer patients.

AKR1C3 as a target in castrate resistant prostate cancer

Aberrant androgen receptor (AR) activation is the major driver of castrate resistant prostate cancer (CRPC). CRPC is ultimately fatal and more therapeutic agents are needed to treat this disease. Compounds that target the androgen axis by inhibiting androgen biosynthesis and or AR signaling are potential candidates for use in CRPC treatment and are currently being pursued aggressively. Aldo-keto reductase 1C3 (AKR1C3) plays a pivotal role in androgen biosynthesis within the prostate. It catalyzes the 17-ketoreduction of weak androgen precursors to give testosterone and 5α-dihydrotestosterone. AKR1C3 expression and activity has been implicated in the development of CRPC, making it a rational target. Selective inhibition of AKR1C3 will be important, however, due to the presence of closely related isoforms, AKR1C1 and AKR1C2 that are also involved in androgen inactivation. We examine the evidence that supports the vital role of AKR1C3 in CRPC and recent developments in the discovery of potent and selective AKR1C3 inhibitors. This article is part of a Special Issue entitled 'CSR 2013'.

2,3-Diarylpropenoic acids as selective non-steroidal inhibitors of type-5 17β-hydroxysteroid dehydrogenase (AKR1C3)

The aldo-keto reductase AKR1C3 is an important target for the development of new drugs. Selective inhibitors of this enzyme are needed because they should not inhibit other, structurally closely related AKR1C isoforms. A comprehensive series of 2,3-diarylpropenoic acids was synthesized and evaluated for the inhibition of AKR1C1-AKR1C3. We found that the 4-methylsulfonylphenyl substituent at position 2 of these acids is required to exhibit the selective inhibition of AKR1C3. The best results were obtained for the compounds that fulfill the above requirement and possess a 4-bromophenyl, 4-methylthiophenyl, 4-methylphenyl or 4-ethylphenyl substituent at position 3 of the substituted propenoic acids (i.e., acids 28, 29, 37, and 39, respectively). These compounds represent an important step toward the development of drug candidates for a treatment of the hormone-dependent and hormone-independent forms of prostate and breast cancers.

The anti-cancer activities of jasmonates

Jasmonates, plant stress hormones protecting the plant from microbial pathogens and environmental stresses, were also discovered to have toxic activities toward mammalian cancer cells. Methyl jasmonate (MJ) was found to be the most active anti-cancer derivate among natural jasmonates, exhibiting a specific cell death-induction effect toward several cancer cells. Since that discovery of jasmonates-inducing cancer cell death, the molecular mechanism of action of jasmonates leading to cell death was deciphered. Moreover, in addition to the direct effects of MJ on cancer cell death, it was found to deregulate several genes and affect various intracellular factors and cellular processes, such as sensitization of apoptotic cell death induced by TRAIL, cancer cell migration attenuation, cell cycle arrest, and differentiation. This mini-review summarizes over a decade of research of jasmonates as anti-cancer agents.

Differential response of macrophages to core-shell Fe3O4@Au nanoparticles and nanostars

Murine RAW 264.7 cells were exposed to spheroidal core-shell Fe(3)O(4)@Au nanoparticles (SCS-NPs, ca. 34 nm) or nanostars (NSTs, ca. 100 nm) in the presence of bovine serum albumin, with variable effects observed after macrophagocytosis. Uptake of SCS-NPs caused macrophages to adopt a rounded, amoeboid form, accompanied by an increase in surface detachment. In contrast, the uptake of multibranched NSTs did not induce gross changes in macrophage shape or adhesion, but correlated instead with cell enlargement and signatures of macrophage activation such as TNF-α and ROS. MTT assays indicate a low cytotoxic response to either SCS-NPs or NSTs despite differences in macrophage behavior. These observations show that differences in NP size and shape are sufficient to produce diverse responses in macrophages following uptake.

Methyljasmonate displays in vitro and in vivo activity against multiple myeloma cells

Jasmonates, plant stress hormones, have been demonstrated to be effective in killing various types of cancer cells. We therefore tested if methyljasmonate (MJ) has activity against multiple myeloma (MM) in vitro and in vivo. MM cell lines and primary MM tumour cells responded to MJ in vitro at concentrations that did not significantly affect normal haematopoietic cells, without stroma-mediated resistance. Brief MJ exposures of MM cells caused release of Hexokinase 2 (HK2) from mitochondria, rapid ATP depletion, perturbation of major intracellular signalling pathways, and ensuing mainly apoptotic cell death. Sensitivity to MJ correlated with lower cellular glucose consumption and lactate production, as well as lower intracellular protein levels of HK2, phosphorylated Voltage-dependent anion channel 2/3 (pVDAC2/3) and Aldo-keto reductase family 1 member C1 (AKR1C1), which represent potential biomarkers of responsiveness to MJ treatment, especially as AKR1C1 transcript levels also correlate with clinical outcome in bortezomib- or dexamethasone-treated MM patients. Interestingly, MJ synergized with bortezomib in vitro and prolonged survival of immunocompromised mice harbouring diffuse lesions of MM.1S cells compared to vehicle-treated mice (P = 0·0046). These studies indicate that jasmonates represent a new, promising strategy to treat MM.

3-(3,4-Dihydroisoquinolin-2(1H)-ylsulfonyl)benzoic Acids: highly potent and selective inhibitors of the type 5 17-β-hydroxysteroid dehydrogenase AKR1C3

A high-throughput screen identified 3-(3,4-dihydroisoquinolin-2(1H)-ylsulfonyl)benzoic acid as a novel, highly potent (low nM), and isoform-selective (1500-fold) inhibitor of aldo-keto reductase AKR1C3: a target of interest in both breast and prostate cancer. Crystal structure studies showed that the carboxylate group occupies the oxyanion hole in the enzyme, while the sulfonamide provides the correct twist to allow the dihydroisoquinoline to bind in an adjacent hydrophobic pocket. SAR studies around this lead showed that the positioning of the carboxylate was critical, although it could be substituted by acid isosteres and amides. Small substituents on the dihydroisoquinoline gave improvements in potency. A set of "reverse sulfonamides" showed a 12-fold preference for the R stereoisomer. The compounds showed good cellular potency, as measured by inhibition of AKR1C3 metabolism of a known dinitrobenzamide substrate, with a broad rank order between enzymic and cellular activity, but amide analogues were more effective than predicted by the cellular assay.

Selective inhibition of human type-5 17β-hydroxysteroid dehydrogenase (AKR1C3) by baccharin, a component of Brazilian propolis

The human aldo-keto reductase (AKR) 1C3, also known as type-5 17β-hydroxysteroid dehydrogenase and prostaglandin F synthase, has been suggested as a therapeutic target in the treatment of prostate and breast cancers. In this study, AKR1C3 inhibition was examined by Brazilian propolis-derived cinnamic acid derivatives that show potential antitumor activity, and it was found that baccharin (1) is a potent competitive inhibitor (K(i) 56 nM) with high selectivity, showing no significant inhibition toward other AKR1C isoforms (AKR1C1, AKR1C2, and AKR1C4). Molecular docking and site-directed mutagenesis studies suggested that the nonconserved residues Ser118, Met120, and Phe311 in AKR1C3 are important for determining the inhibitory potency and selectivity of 1. The AKR1C3-mediated metabolism of 17-ketosteroid and farnesal in cancer cells was inhibited by 1, which was effective from 0.2 μM with an IC(50) value of about 30 μM. Additionally, 1 suppressed the proliferation of PC3 prostatic cancer cells stimulated by AKR1C3 overexpression. This study is the first demonstration that 1 is a highly selective inhibitor of AKR1C3.

Methyl jasmonate reduces the survival of cervical cancer cells and downregulates HPV E6 and E7, and survivin

The present study further investigated the mode of action of methyl jasmonate (MJ) in different cervical cancer cell lines. We show that in addition to the short term cytotoxicity, MJ effectively reduced the survival of cervical cancer cells (clonogenicity assays). MJ induced apoptosis in all cervical cancer cells. In some cell lines, MJ caused elevation of the mitochondrial superoxide anion, notably, in HeLa and CaSki. Changes in the expression of p53 and bax were variable, yet, downregulation of survivin was common to all cervical cancer cells. MJ significantly reduced the levels of the human papillomavirus (HPV) E6 and E7 proteins without alteration of the mRNA levels. Moreover, ectopic expression of E6, E7 or both in cervical cancer cells that lack HPV (C33A), did not alter significantly their response to MJ. Our studies point to MJ as an effective anticancer agent against a variety of cervical cancer cells acting through shared and different pathways to induce cell death regardless of the presence of HPV.

Human metabolic individuality in biomedical and pharmaceutical research

Genome-wide association studies (GWAS) have identified many risk loci for complex diseases, but effect sizes are typically small and information on the underlying biological processes is often lacking. Associations with metabolic traits as functional intermediates can overcome these problems and potentially inform individualized therapy. Here we report a comprehensive analysis of genotype-dependent metabolic phenotypes using a GWAS with non-targeted metabolomics. We identified 37 genetic loci associated with blood metabolite concentrations, of which 25 show effect sizes that are unusually high for GWAS and account for 10-60% differences in metabolite levels per allele copy. Our associations provide new functional insights for many disease-related associations that have been reported in previous studies, including those for cardiovascular and kidney disorders, type 2 diabetes, cancer, gout, venous thromboembolism and Crohn's disease. The study advances our knowledge of the genetic basis of metabolic individuality in humans and generates many new hypotheses for biomedical and pharmaceutical research.

Dasatinib, imatinib and staurosporine capture compounds - Complementary tools for the profiling of kinases by Capture Compound Mass Spectrometry (CCMS)

Capture Compound Mass Spectrometry (CCMS) is a platform technology for the functional isolation of subproteomes. Here we report the synthesis of two new kinase Capture Compounds (CCs) based on the tyrosine-kinase specific inhibitors dasatinib and imatinib and compare their interaction profiles to that of our previously reported staurosporine-CCs. CCs are tri-functional molecules: they comprise a sorting function (e.g. the small molecule or drug of interest) which interacts with target proteins, a photo-activatable reactivity function to covalently trap the interacting proteins, and a sorting function to isolate the CC-protein conjugates from complex biological samples for protein identification by liquid chromatography/mass spectrometry (LC-MS/MS). We present data of CCMS experiments from human HepG2 cells and compare the profiles of the kinases isolated with dasatinib, imatinib and staurosporine CC, respectively. Dasatinib and imatinib have a more selective kinase binding profile than staurosporine. Moreover, the new CCs allow isolation and identification of additional kinases, complementing the staurosporine CC. The family of kinase CCs will be a valuable tool for the proteomic profiling of this important protein class. Besides sets of expected kinases we identified additional specific interactors; these off-targets may be of relevance in the view of the pharmacological profile of dasatinib and imatinib.

Inhibitors of type 5 17β-hydroxysteroid dehydrogenase (AKR1C3): overview and structural insights

There is considerable interest in the development of an inhibitor of aldo-keto reductase (AKR) 1C3 (type 5 17β-hydroxysteroid dehydrogenase and prostaglandin F synthase) as a potential therapeutic for both hormone-dependent and hormone-independent cancers. AKR1C3 catalyzes the reduction of 4-androstene-3,17-dione to testosterone and estrone to 17β-estradiol in target tissues, which will promote the proliferation of hormone dependent prostate and breast cancers, respectively. AKR1C3 also catalyzes the reduction of prostaglandin (PG) H(2) to PGF(2α) and PGD(2) to 9α,11β-PGF(2), which will limit the formation of anti-proliferative prostaglandins, including 15-deoxy-Δ(12,14)-PGJ(2), and contribute to proliferative signaling. AKR1C3 is overexpressed in a wide variety of cancers, including breast and prostate cancer. An inhibitor of AKR1C3 should not inhibit the closely related isoforms AKR1C1 and AKR1C2, as they are involved in other key steroid hormone biotransformations in target tissues. Several structural leads have been explored as inhibitors of AKR1C3, including non-steroidal anti-inflammatory drugs, steroid hormone analogues, flavonoids, cyclopentanes, and benzodiazepines. Inspection of the available crystal structures of AKR1C3 with multiple ligands bound, along with the crystal structures of the other AKR1C isoforms, provides a structural basis for the rational design of isoform specific inhibitors of AKR1C3. We find that there are subpockets involved in ligand binding that are considerably different in AKR1C3 relative to the closely related AKR1C1 or AKR1C2 isoforms. These pockets can be used to further improve the binding affinity and selectivity of the currently available AKR1C3 inhibitors. Article from the special issue on Targeted Inhibitors.

Identification of chemically diverse, novel inhibitors of 17β-hydroxysteroid dehydrogenase type 3 and 5 by pharmacophore-based virtual screening

17β-Hydroxysteroid dehydrogenase type 3 and 5 (17β-HSD3 and 17β-HSD5) catalyze testosterone biosynthesis and thereby constitute therapeutic targets for androgen-related diseases or endocrine-disrupting chemicals. As a fast and efficient tool to identify potential ligands for 17βHSD3/5, ligand- and structure-based pharmacophore models for both enzymes were developed. The models were evaluated first by in silico screening of commercial compound databases and further experimentally validated by enzymatic efficacy tests of selected virtual hits. Among the 35 tested compounds, 11 novel inhibitors with distinct chemical scaffolds, e.g. sulfonamides and triazoles, and with different selectivity properties were discovered. Thereby, we provide several potential starting points for further 17β-HSD3 and 17β-HSD5 inhibitor development. Article from the Special issue on Targeted Inhibitors.

Isolation and identification of a distinct side population cancer cells in the human epidermal squamous cancer cell line A431

Side population (SP) cells have been suggested to be multipotent cancer stem cells. To address whether SP cells exist in epidermal squamous cancer cell line A431, A431 cells dyed with Hoechst 33342 were sorted through flow cytometry. The SP cells were then analyzed by colony-forming and cell proliferation assay. Further, tumorigenicity and microarray analysis were used to compare biological difference between SP and non-SP (NSP) cells. Our results showed that SP cells existed in the A431 cell line, showing higher proliferating and colony-forming ability than NSP cells. Tumors generated from SP cells were larger than those from the NSP cells in NOD/SCID mice. The mRNA microarray profiling revealed that five cancer marker gene expressions were up-regulated and one tumor suppressor gene expression was down-regulated. These findings suggest that SP cells in A431 could contribute to self-renewal, neoplastic transformation, and cancer metastasis of human epidermal squamous cell carcinoma.

Long-term in vitro treatment of human glioblastoma cells with temozolomide increases resistance in vivo through up-regulation of GLUT transporter and aldo-keto reductase enzyme AKR1C expression

Glioblastoma (GBM) is the most frequent malignant glioma. Treatment of GBM patients is multimodal with maximum surgical resection, followed by concurrent radiation and chemotherapy with the alkylating drug temozolomide (TMZ). The present study aims to identify genes implicated in the acquired resistance of two human GBM cells of astrocytic origin, T98G and U373, to TMZ. Resistance to TMZ was induced by culturing these cells in vitro for months with incremental TMZ concentrations up to 1 mM. Only partial resistance to TMZ has been achieved and was demonstrated in vivo in immunocompromised mice bearing orthotopic U373 and T98G xenografts. Our data show that long-term treatment of human astroglioma cells with TMZ induces increased expression of facilitative glucose transporter/solute carrier GLUT/SLC2A family members, mainly GLUT-3, and of the AKR1C family of proteins. The latter proteins are phase 1 drug-metabolizing enzymes involved in the maintenance of steroid homeostasis, prostaglandin metabolism, and metabolic activation of polycyclic aromatic hydrocarbons. GLUT-3 has been previously suggested to exert roles in GBM neovascularization processes, and TMZ was found to exert antiangiogenic effects in experimental gliomas. AKR1C1 was previously shown to be associated with oncogenic potential, with proproliferative effects similar to AKR1C3 in the latter case. Both AKR1C1 and AKR1C2 proteins are involved in cancer pro-proliferative cell chemoresistance. Selective targeting of GLUT-3 in GBM and/or AKR1C proteins (by means of jasmonates, for example) could thus delay the acquisition of resistance to TMZ of astroglioma cells in the context of prolonged treatment with this drug.

Discovery of substituted 3-(phenylamino)benzoic acids as potent and selective inhibitors of type 5 17β-hydroxysteroid dehydrogenase (AKR1C3)

Aldo-keto reductase 1C3 (AKR1C3) also known as type 5 17β-hydroxysteroid dehydrogenase has been implicated as one of the key enzymes driving the elevated intratumoral androgen levels observed in castrate resistant prostate cancer (CRPC). AKR1C3 inhibition therefore presents a rational approach to managing CRPC. Inhibitors should be selective for AKR1C3 over other AKR1C enzymes involved in androgen metabolism. We have synthesized 2-, 3-, and 4-(phenylamino)benzoic acids and identified 3-(phenylamino)benzoic acids that have nanomolar affinity and exhibit over 200-fold selectivity for AKR1C3 versus other AKR1C isoforms. The AKR1C3 inhibitory potency of the 4'-substituted 3-(phenylamino)benzoic acids shows a linear correlation with both electronic effects of substituents and the pK(a) of the carboxylic acid and secondary amine groups, which are interdependent. These compounds may be useful in treatment and/or prevention of CRPC as well as understanding the role of AKR1C3 in endocrinology.

Lycorine sensitizes CD40 ligand-protected chronic lymphocytic leukemia cells to bezafibrate- and medroxyprogesterone acetate-induced apoptosis but dasatanib does not overcome reported CD40-mediated drug resistance

BACKGROUND

Tumor cells in chronic lymphocytic leukemia accumulate in the periphery through the proliferation of a minority of cells in lymph nodes. The proliferative and survival signals in these proliferation centers include interactions with T lymphocytes expressing CD40 ligand. We have demonstrated that the low toxicity combination of bezafibrate and medroxyprogesterone acetate induces mitochondrial superoxide-mediated apoptosis of non-CD40-liganded cells but not of cells exposed to CD40 ligand. Here, we assessed the ability of dasatinib and lycorine to restore bezafibrate- and medroxyprogesterone acetate- induced apoptosis in cells exposed to CD40 ligand. In parallel experiments we compared the ability of dasatinib to induce apoptosis of cells co-treated with fludarabine.

DESIGN AND METHODS

Primary chronic lymphocytic leukemia and peripheral blood mononuclear cells were exposed to drug combinations for 72 hours on control and CD40 ligand-expressing fibroblast monolayers. Cells were harvested and analyzed for apoptosis and levels of mitochondrial superoxide using flow cytometry. In some experiments cells were removed from CD40 ligand at 48 hours, retreated and analyzed after a further 24 hours. The effect of CD40 ligand and drug treatments on mitochondrial superoxide levels were assessed.

RESULTS

As previously described, dasatinib rendered cells sensitive to fludarabine but only when CD40 ligand was removed for the last 24 hours of culture. In contrast, lycorine restored the bezafibrate- and medroxyprogesterone acetate-induced apoptosis associated with mitochondrial superoxide even during continuous exposure to CD40 ligand. Furthermore, combined bezafibrate, medroxyprogesterone acetate and lycorine had little effect against normal peripheral blood mononuclear cells, whereas dasatinib with fludarabine induced high levels of apoptosis.

CONCLUSIONS

Our data indicate the potential of bezafibrate, medroxyprogesterone acetate and lycorine as novel therapy in chronic lymphocytic leukemia and have important implications for the reported potential of c-abl kinase inhibitors in this disease.

Lack of functional and expression homology between human and mouse aldo-keto reductase 1C enzymes: implications for modelling human cancers

Background

Over recent years, enzymes of the aldo-keto reductase (AKR) 1C subfamily have been implicated in the progression of prostate, breast, endometrial and leukemic cancers. This is due to the ability of AKR1C enzymes to modify androgens, estrogens, progesterone and prostaglandins (PGs) in a tissue-specific manner, regulating the activity of nuclear receptors and other downstream effects. Evidence supporting a role for AKR1C enzymes in cancer derives mostly from studies with isolated primary cells from patients or immortalized cell lines. Mice are ideal organisms for in vivo studies, using knock-out or over-expression strains. However, the functional conservation of AKR1C enzymes between human and mice has yet to be described.

Results

In this study, we have characterized and compared the four human (AKR1C1,-1C2, -1C3 and -1C4) and the eight murine (AKR1C6, -1C12, -1C13, -1C14, -1C18, -1C19, -1C20 and -1C21) isoforms in their phylogeny, substrate preference and tissue distribution. We have found divergent evolution between human and murine AKR1C enzymes that was reflected by differing substrate preference. Murine enzymes did not perform the 11β-ketoreduction of prostaglandin (PG) D₂, an activity specific to human AKR1C3 and important in promoting leukemic cell survival. Instead, murine AKR1C6 was able to perform the 9-ketoreduction of PGE₂, an activity absent amongst human isoforms. Nevertheless, reduction of the key steroids androstenedione, 5α-dihydrotestosterone, progesterone and estrone was found in murine isoforms. However, unlike humans, no AKR1C isoforms were detected in murine prostate, testes, uterus and haemopoietic progenitors.

Conclusions

This study exposes significant lack of phylogenetic and functional homology between human and murine AKR1C enzymes. Therefore, we conclude that mice are not suitable to model the role of AKR1C in human cancers and leukemia.