Type 1 iodothyronine deiodinase (DIO1) contributes to deiodination of 3,5,3',5'-tetraiodo-L-thyronine (thyroxine, T4) yielding of 3,5,3'-triiodothyronine (T3), a powerful regulator of cell differentiation, proliferation, and metabolism. Our previous work showed that loss of DIO1 enhances proliferation and migration of renal cancer cells. However, the global effects of DIO1 expression in various tissues affected by cancer remain unknown. Here, the effects of stable DIO1 re-expression were analyzed on the proteome of renal cancer cells, followed by quantitative real-time PCR validation in two renal cancer-derived cell lines. DIO1-induced changes in intracellular concentrations of thyroid hormones were quantified by L-MS/MS and correlations between expression of DIO1 and potential target genes were determined in tissue samples from renal cancer patients. Stable re-expression of DIO1, resulted in 26 downregulated proteins while 59 proteins were overexpressed in renal cancer cells. The 'downregulated' group consisted mainly of oncoproteins (e.g. STAT3, ANPEP, TGFBI, TGM2) that promote proliferation, migration and invasion. Furthermore, DIO1 re-expression enhanced concentrations of two subunits of thyroid hormone transporter (SLC7A5, SLC3A2), enzymes of key pathways of cellular energy metabolism (e.g. TKT, NAMPT, IDH2), sex steroid metabolism and anti-oxidative response (AKR1C2, AKR1B10). DIO1 expression resulted in elevated intracellular concentration of T4. Expression of DIO1-affected genes strongly correlated with DIO1 transcript levels in tissue samples from renal cancer patients as well as with their poor survival. This first study addressing effects of deiodinase re-expression on proteome of cancer cells demonstrates that induced DIO1 re-expression in renal cancer robustly downregulates oncoproteins, affects key metabolic pathways, and triggers proteins involved in anti-oxidative protection. This data supports the notion that suppressed DIO1 expression and changes in local availability of thyroid hormones might favor a shift from a differentiated to a more proliferation-prone state of cancer tissues and cell lines.

Aldose reductase (ALR2) inhibition is the most legitimate approach for the management of diabetic complications. The limited triumph in the drug development against ALR2 is mainly because of its close structural similarity with the other members of aldo-keto reductase (AKR) superfamily viz. ALR1, AKR1B10; and lipophilicity problem i.e. poor diffusion of synthetic aldose reductase inhibitors (ARIs) to target tissues. The literature evidenced that naturally occurring curcumin demonstrates relatively specific and non-competitive inhibition towards human recombinant ALR2 over ALR1 and AKR1B10; however β-diketone moiety of curcumin is a specific substrate for liver AKRs and accountable for it's rapid in vivo metabolism. In the present study, structure based comprehensive modelling studies were used to map the pharmacophoric features/spatial fingerprints of curcumin analogues responsible for their ALR2 specificity along with potency on a data set of synthetic curcumin analogues and naturally occurring curcuminoids. The data set molecules were also screened for drug-likeness or ADME parameters, and the screening data strongly support that curcumin analogues could be proposed as a good drug candidate for the development of ALR2 inhibitors with improved pharmacokinetic profile compared to curcuminoids due to the absence of β-diketone moiety in their structural framework.

Intrinsic or acquired drug resistance is a major impediment to the successful treatment of women with breast cancer using chemotherapy. We have observed that MCF-7 breast tumor cells selected for resistance to doxorubicin or epirubicin (MCF-7DOX2 and MCF-7EPI cells, respectively) exhibited increased expression of several members of the aldo-keto reductase (AKR) gene family (in particular AKR1C3 and AKR1B10) relative to control MCF-7CC cells selected by propagation in the absence of drug. Normal cellular roles for the AKRs include the promotion of estrogen (E2) synthesis from estrone (E1) and the hydroxylation and detoxification of exogenous xenobiotics such as anthracycline chemotherapy drugs. While hydroxylation of anthracyclines strongly attenuates their cytotoxicity, it is unclear whether the enhanced AKR expression in the above anthracycline-resistant cells promotes E2 synthesis and/or alterations in E2 signalling pathways and whether such changes contribute to enhanced survival and anthracycline resistance. To determine the role of AKRs and E2 pathways in doxorubicin resistance, we examined changes in the expression of E2-related genes and proteins upon acquisition of doxorubicin resistance. We also assessed the effects of AKR overexpression or downregulation or the effects of activators or inhibitors of E2-dependent pathways on previously acquired resistance to doxorubicin. In this study we observed that the enhanced AKR expression upon acquisition of anthracycline resistance was, in fact, associated with enhanced E2 production. However, the expression of estrogen receptor α (ERα) was reduced by 2- to 5-fold at the gene transcript level and 2- to 20-fold at the protein level upon acquisition of anthracycline resistance. This was accompanied by an even stronger reduction in ERα phosphorylation and activity, including highly suppressed expression of two proteins under E2-dependent control (Bcl-2 and cyclin D1). The diminished Bcl-2 and cyclin D1 expression would be expected to reduce the growth rate of the cells, a hypothesis which was confirmed in subsequent cell proliferation experiments. AKR1C3 or AKR1B10 overexpression alone had no effect on doxorubicin sensitivity in MCF-7CC cells, while siRNA-mediated knockdown of AKR1C3 and/or AKR1B10 expression had no significant effect on sensitivity to doxorubicin in MCF-7DOX2 or MCF-7EPI cells. This suggested that enhanced or reduced AKR expression/activity is insufficient to confer anthracycline resistance or sensitivity to breast tumor cells, respectively. Rather, it would appear that AKR overexpression acts in concert with other proteins to confer anthracycline resistance, including reduced E2-dependent expression of both an important apoptosis inhibitor (Bcl-2) and a key protein associated with activation of cell cycle-dependent kinases (cyclin D1).

Keloid disease is a recurrent fibroproliferative cutaneous tumor of unknown pathogenesis for which clinical management remains unsatisfactory. To obtain new insights into hitherto underappreciated aspects of keloid pathobiology, we took a laser capture microdissection-based, whole-genome microarray analysis approach to identify distinct keloid disease-associated gene expression patterns within defined keloid regions. Identification of the aldo-keto reductase enzyme AKR1B10 as highly up-regulated in keloid epidermis suggested that an imbalance of retinoic acid metabolism is likely associated with keloid disease. Here, we show that AKR1B10 transfection into normal human keratinocytes reproduced the abnormal retinoic acid pathway expression pattern we had identified in keloid epidermis. Cotransfection of AKR1B10 with a luciferase reporter plasmid showed reduced retinoic acid response element activity, supporting the hypothesis of retinoic acid synthesis deficiency in keloid epidermis. Paracrine signals released by AKR1B10-overexpressing keratinocytes into conditioned medium resulted in up-regulation of transforming growth factor-β1, transforming growth factor-β2, and collagens I and III in both keloid and normal skin fibroblasts, mimicking the typical profibrotic keloid profile. Our study results suggest that insufficient retinoic acid synthesis by keloid epidermal keratinocytes may contribute to the pathogenesis of keloid disease. We refocus attention on the role of injured epithelium in keloid disease and identify AKR1B10 as a potential new target in future management of keloid disease.

The purpose of this study was to investigate the origin and function of the aldo-keto reductase (AKR) superfamily as enzymes involved in the detoxification of xenobiotics. We used the cyanobacterium Synechocystis sp. PCC 6803 as a model organism and sequence alignments to find bacterial AKRs with highest identity to human enzymes. Disappearance of NADPH was monitored spectrophotometrically to calculate enzymatic activity. The molecular weight of the native protein was determined by size exclusion chromatography. Substrate docking was performed by SwissDock. Sequence alignments identified the NADPH-dependent AKR3G1 having 41.5 and 40% identity with the human enzymes AKR1B1 and AKR1B10, respectively. Highest enzymatic efficiency was observed with 4-oxonon-2-enal (4-ONE; k(cat)/K(m), 561 s(-1) mM(-1)) and 4-hydroxynonenal (k(cat)/K(m), 26.5 s(-1) mM(-1)), respectively. P74308 is the most efficient enzyme for 4-ONE discovered until now. Cooperativity of this monomeric enzyme was observed with some substrates. Enzyme inactivation or oligomerization as possible explanations for nonhyperbolic enzyme kinetics were ruled out by Selwyn's test and gel filtration. The role of the little investigated carbonyl-reducing enzymes in detoxification seems to be in fact a very old process with rarely observed nonhyperbolic enzyme kinetics as an adaptation mechanism to higher concentrations of reactive oxygen species.

AKR1B10 is a human-type aldo-keto reductase. The up-regulation of AKR1B10 has been associated with various cancers including non-small cell lung carcinoma, viral and bacterial infections, and skin diseases. However, the mechanisms underlying AKR1B10 gene regulation are not fully understood. We previously indicated the involvement of the transcription factor Nrf2 in AKR1B10 gene regulation. There are at least five potential Nrf2-responsive consensus sequences, so-called antioxidant response elements (AREs), and several ARE-like sequences in the 5'-flanking region up to -3282 bp of the AKR1B10 gene. In the present study, we attempted to identify functional AREs by luciferase reporter analyses using various mutants for each ARE. And we found that only those between -530 and -520 bp (ARE-A), which is the closest location to the translation start site, were functional among the five ARE consensus sites examined. Furthermore, ARE-A functioned co-operatively with the neighboring AP-1 site. Since the AP-1 site resembles ARE, the tandem arrangement of these two elements may be essential for augmented responsiveness to Nrf2 and plays an important role in AKR1B10 gene regulation by various Nrf2-mediating stimuli.

AKR1B10 is a member of the human aldo-keto reductase superfamily which is highly expressed in several types of cancers, and has been regarded as a promising cancer therapeutic target. In this paper, a series of polyhydroxy steroids were designed and synthesized to selectively inhibit AKR1B10 activity. The most selective compound, novel compound 6, has an IC50 of 0.83±0.07μM and a selectivity of more than 120-fold for AKR1B10/AKR1B1. Structure-activity relation analyses indicate that hydroxyl at C-19 can significantly improve the selective inhibition of AKR1B10. The binding mode of AKR1B10 and its inhibitors were studied.

Various methods for the direct reprogramming of human somatic cells have been developed. However, a therapeutic method to reprogram and eliminate human solid tumor cells has not been developed. Here we show a novel therapeutic method to reprogram and eliminate human solid tumor cells with chemicals. This therapeutic method may be applicable to various human solid tumor cells that express aldo-keto reductase family 1 member B10 (AKR1B10) and retinoid X receptors (RXRs).

The AKR1B10 (aldo-keto reductase family 1 member B10) gene has important functions in carcinogen-induced neoplasia. AKR1B10 is also expressed in type 2 reaction leprosy patients (R2). We measured the expression of AKR1B10 in the skin lesions of patients with leprosy by immunohistochemistry from biopsies that encompassed the spectrum of types of leprosy, based on the Ridley and Jopling classification [10 samples each of tuberculoid (TT), borderline tuberculoid (BT), mid-borderline (BB), and borderline lepromatous (BL) lesions; four samples of lepromatous lesions (LL)], reactional leprosy [14 samples of type 1 Reaction (R1) and 10 samples of type 2 Reaction (R2)], and biopsies from 9 healthy control (HC) subjects. In addition, 46 lepromatous lesions (BL and LL), 45 lepromatous lesions in regression, and 115 R2 lesions were included. Eight of 10 R2 samples (80%), 3 of 46 active BL and LL samples (6%), 23 of 45 BL and LL samples in regression (51%), and 107 of 115 R2 samples (93%) were positive for AKR1B10, differing significantly between all groups (p < 0.05). AKR1B10 expression was highest in the cytoplasm of macrophages. Thus, AKR1B10 is overexpressed on the lepromatous side (BL and LL) in samples that are in regression, especially type 2 reaction-associated lesions, rendering it a potential marker of type 2 reactional episodes of leprosy and a target of drugs against reactional episodes.

OBJECTIVE

To investigate the association of AKR1B10 expression in gastric cancer tissues with clinicopathologic features and prognosis of gastric cancer patients.

METHODS

Real-time polymerase chain reaction (RT-PCR) was conducted to detect AKR1B10 mRNA expression in gastric cancer and adjacent gastric mucosa tissues (n=36). AKR1B10 protein expression was measured by immunohistochemistry in primary gastric cancer tissues (n=100) and non-tumorous gastric mucosa tissues (n=70).

RESULTS

RT-PCR results confirmed that AKR1B10 was significantly down-regulated in gastric cancer tissues compared with that in paired adjacent mucosa [8.3% (3/36) vs. 91.7% (33/36), P=0.000]. Immunohistochemistry revealed that the percentage of AKR1B10 positive specimens in gastric carcinoma was lower than that in normal specimens [33.0% (33/100) vs. 92.9% (65/70), P=0.000]. The frequencies of positive AKR1B10 in patients was significantly correlated with tumor size (P=0.000), invasive depth (P=0.004), lymph node metastasis (P=0.028), distant metastasis (P=0.031) and TNM stages (P=0.000). The 5-year survival rate of positive AKR1B10 group was significantly higher as compared to negative group (60.6% vs. 32.8%, P<0.01).

CONCLUSIONS

The down-regulation of AKR1B10 expression in gastric cancer may be associated with the progress of gastric cancer is suggestive of poor prognosis.

The aldo-keto reductase (AKR) superfamily comprises NAD(P)H-dependent enzymes that catalyze the reduction of a variety of carbonyl compounds. AKRs are classified in families and subfamilies. Humans exhibit three members of the AKR1B subfamily: AKR1B1 (aldose reductase, participates in diabetes complications), AKR1B10 (overexpressed in several cancer types), and the recently described AKR1B15. AKR1B10 and AKR1B15 share 92% sequence identity, as well as the capability of being active towards retinaldehyde. However, AKR1B10 and AKR1B15 exhibit strong differences in substrate specificity and inhibitor selectivity. Remarkably, their substrate-binding sites are the most divergent parts between them. Out of 27 residue substitutions, six are changes to Phe residues in AKR1B15. To investigate the participation of these structural changes, especially the Phe substitutions, in the functional features of each enzyme, we prepared two AKR1B10 mutants. The AKR1B10 m mutant carries a segment of six AKR1B15 residues (299-304, including three Phe residues) in the respective AKR1B10 region. An additional substitution (Val48Phe) was incorporated in the second mutant, AKR1B10mF48. This resulted in structures with smaller and more hydrophobic binding pockets, more similar to that of AKR1B15. In general, the AKR1B10 mutants mirrored well the specific functional features of AKR1B15, i.e., the different preferences towards the retinaldehyde isomers, the much higher activity with steroids and ketones, and the unique behavior with inhibitors. It can be concluded that the Phe residues of loop C (299-304) contouring the substrate-binding site, in addition to Phe at position 48, strongly contribute to a narrower and more hydrophobic site in AKR1B15, which would account for its functional uniqueness. In addition, we have investigated the AKR1B10 and AKR1B15 activity toward steroids. While AKR1B10 only exhibits residual activity, AKR1B15 is an efficient 17-ketosteroid reductase. Finally, the functional role of AKR1B15 in steroid and retinaldehyde metabolism is discussed.

Inhalation of 9,10-phenanthrenequinone (9,10-PQ), a major quinone in diesel exhaust, exerts fatal damage against a variety of cells involved in respiratory function. Here, we show that treatment with high concentrations of 9,10-PQ evokes apoptosis of lung cancer A549 cells through production of reactive oxygen species (ROS). In contrast, 9,10-PQ at its concentrations of 2 and 5 μM elevated the potentials for proliferation, invasion, metastasis and tumorigenesis, all of which were almost completely inhibited by addition of an antioxidant N-acetyl-l-cysteine, inferring a crucial role of ROS in the overgrowth and malignant progression of lung cancer cells. Comparison of mRNA expression levels of six aldo-keto reductases (AKRs) in the 9,10-PQ-treated cells advocated up-regulation of AKR1B10 as a major cause contributing to the lung cancer malignancy. In support of this, the elevation of invasive, metastatic and tumorigenic activities in the 9,10-PQ-treated cells was significantly abolished by the addition of a selective AKR1B10 inhibitor oleanolic acid. Intriguingly, zymographic and real-time PCR analyses revealed remarkable increases in secretion and expression, respectively, of matrix metalloproteinase 2 during the 9,10-PQ treatment, and suggested that the AKR1B10 up-regulation and resultant activation of mitogen-activated protein kinase cascade are predominant mechanisms underlying the metalloproteinase induction. In addition, HPLC analysis and cytochrome c reduction assay in in vitro 9,10-PQ reduction by AKR1B10 demonstrated that the enzyme catalyzes redox-cycling of this quinone, by which ROS are produced. Collectively, these results suggest that AKR1B10 is a key regulator involved in overgrowth and malignant progression of the lung cancer cells through ROS production due to 9,10-PQ redox-cycling.

Hop-derived compounds have been subjected to numerous biomedical studies investigating their impact on a wide range of pathologies. Isomerised bitter acids (isoadhumulone, isocohumulone and isohumulone) from hops, used in the brewing process of beer, are known to inhibit members of the aldo-keto-reductase superfamily. Aldo-keto-reductase 1B10 (AKR1B10) is upregulated in various types of cancer and has been reported to promote carcinogenesis. Inhibition of AKR1B10 appears to be an attractive means to specifically treat RAS-dependent malignancies. However, the closely related reductases AKR1A1 and AKR1B1, which fulfil important roles in the detoxification of endogenous and xenobiotic carbonyl compounds oftentimes crossreact with inhibitors designed to target AKR1B10. Accordingly, there is an ongoing search for selective AKR1B10 inhibitors that do not interact with endogeneous AKR1A1 and AKR1B1-driven detoxification systems. In this study, unisomerised α-acids (adhumulone, cohumulone and n-humulone) were separated and tested for their inhibitory potential on AKR1A1, AKR1B1 and AKR1B10. Also AKR1B10-mediated farnesal reduction was effectively inhibited by α-acid congeners with Ki-values ranging from 16.79 ± 1.33 µM (adhumulone) to 3.94 ± 0.33 µM (n-humulone). Overall, α-acids showed a strong inhibition with selectivity (115⁻137 fold) for AKR1B10. The results presented herein characterise hop-derived α-acids as a promising basis for the development of novel and selective AKR1B10-inhibitors.

Aldo-keto reductase 1B10 (AKR1B10) is overexpressed in several extraintestinal cancers, particularly in non-small-cell lung cancer, where AKR1B10 is a potential diagnostic marker and therapeutic target. Selective AKR1B10 inhibitors are required because compounds should not inhibit the highly related aldose reductase that is involved in monosaccharide and prostaglandin metabolism. Currently, 7-hydroxy-2-(4-methoxyphenylimino)-2H-chromene-3-carboxylic acid benzylamide (HMPC) is known to be the most potent competitive inhibitor of AKR1B10, but it is nonselective. In this study, derivatives of HMPC were synthesized by removing the 4-methoxyphenylimino moiety and replacing the benzylamide with phenylpropylamide. Among them, 4c and 4e showed higher AKR1B10 inhibitory potency (IC50 4.2 and 3.5 nM, respectively) and selectivity than HMPC. The treatments with the two compounds significantly suppressed not only migration, proliferation, and metastasis of lung cancer A549 cells but also metastatic and invasive potentials of cisplatin-resistant A549 cells.

The possible molecular mechanisms of Nano-selenium (nano-se) in attenuating hepatocellular carcinoma (HCC) was investigated in this study. To achieve this target, the apoptotic/necrotic rate in hepatic cells was investigated morphologically by double staining with acridine orange/ethidium bromide to address the type of cell death induced by nano-Se in HCC-bearing rats. To predict the oxidative stress and DNA damage, the generation of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 2-deoxyguanosine (2-dG) was examined. Moreover, the expression of some HCC-related genes was investigated such as aldo-keto reductase 1B10 (Akr1b10), ING3 and Foxp1 genes. As well as the histopathological study of liver tissue sections was performed. The results obtained from this study revealed that (HCC+Nano Se) group shows the highest number of damaged cancerous cells. Furthermore, the necrotic/apoptotic rate was significantly higher in (nano-Se+HCC), (HCC+Doxo) and (HCC+Doxo+nano-se) compared to that in the untreated HCC group. Treatment of HCC group with nano-se decreased the ratio of 8-OHdG/2-dG generation significantly with respect to the untreated HCC group. The opposite was observed regarding the gene expression of AKr1b10 and ING3. The treatment of HCC group with nano-se elicited significant increase in the expression of Akr1b10 and ING3 genes compared with untreated HCC group. On the other hand, the expression of Foxp1 gene was significantly decreased in HCC group treated with nano-se in comparison with the untreated HCC group. The histopathological study provided a supportive evidence for the molecular genetics study. Our data shed light on the molecular mechanisms of nano-se in attenuating HCC in the experimental model.

Rabbit aldo-keto reductase (AKR) 1B19 is an ortholog of human aldose reductase-like protein (ARLP), AKR1B10, showing 86% amino acid sequence identity. AKR1B19 exhibits the highest catalytic efficiency for 4-oxo-2-nonenal, a major product of lipid peroxidation, compared to known reductases of this aldehyde. In this study, we found that the reductase activity of AKR1B19 was activated to about 5-fold immediately after the addition of 10 μM SH-reagents (p-chloromercuriphenylsulfonic acid and p-chloromercuribenzoic acid) in the absence or presence of NADPH. In addition, a maximum of 3-fold activation of AKR1B19 was induced by incubation with glutathione disulfide (GSSG) for 1h. The activated enzyme was converted into the native enzyme by further incubation with dithiothreitol and glutathione. The activation was abolished by the C299S mutation of AKR1B19, and the glutathionylated Cys299 was identified by mass spectrometry analysis. The Cys299-modified enzyme displayed different kinetic alterations depending on substrates and inhibitors. In the reduction of 4-oxo-2-nonenal, the catalytic efficiency was increased. Thus, AKR1B10 may be modulated by cellular ratio of GSSG/glutathione and more efficiently act as a detoxifying enzyme for the cytotoxic aldehyde under oxidatively stressed conditions. Furthermore, such an activity alteration by GSSG was not detected in AKR1B10 and rat ARLPs, suggesting the presence of a GSSG-binding site near Cys299 in AKR1B19.

Electrophilic carbonyl compounds are highly cytotoxic and genotoxic. Aldo-keto reductase 1B10 (AKR1B10) is an enzyme catalyzing reduction of carbonyl compounds to less toxic alcoholic forms. This study presents novel evidence that AKR1B10 protects colon cells from DNA damage induced by electrophilic carbonyl compounds. AKR1B10 is specifically expressed in epithelial cells of the human colon, but this study found that AKR1B10 expression was lost or markedly diminished in colorectal cancer, precancerous tissues, and a notable portion of normal adjacent tissues (NAT). SiRNA-mediated silencing of AKR1B10 in colon cancer cells HCT-8 enhanced cytotoxicity of acrolein and HNE, whereas ectopic expression of AKR1B10 in colon cancer cells RKO prevented the host cells against carbonyl cytotoxicity. Furthermore, siRNA-mediated AKR1B10 silencing led to DNA breaks and activation of γ-H2AX protein, a marker of DNA double strand breaks, particularly in the exposure of HNE (10 μM). In the AKR1B10 silenced HCT-8 cells, hypoxanthine-guanine phosphoribosyl transferase (HPRT) mutant frequency increased by 26.8 times at basal level and by 33.5 times in the presence of 10 μM HNE when compared to vector control cells. In these cells, the cyclic acrolein-deoxyguanosine adducts levels were increased by over 10 times. These findings were confirmed by pharmacological inhibition of AKR1B10 activity by Epalrestat. Taken together, these data suggest that AKR1B10 is a critical protein that protects host cells from DNA damage induced by electrophilic carbonyl compounds. AKR1B10 deficiency in the colon may be an important pathogenic factor in disease progression and carcinogenesis. © 2016 Wiley Periodicals, Inc.

Smoking women are probably at a higher risk to develop lung cancer than men. Different explanations exist for these findings, a gender-specific impairment of tobacco carcinogen metabolism being one of them. In this study, we examined the inhibition of NNK reduction to NNAL, the first and most important detoxication step of this tobacco-specific carcinogen. It is mediated by different carbonyl reductases of the SDR (CBR1 and 11βHSD1) and AKR (AKR1B10, AKR1C1, AKR1C2 and AKR1C4) superfamilies. Inhibition constants of NNK reduction were determined with male (testosterone) and female (estradiol, progesterone) sex hormones and the contraceptives ethinylestradiol and drospirenone in A549 cells and with purified enzymes. Female sex hormones turned out to be stronger inhibitors than testosterone. The gestagen progesterone and its synthetic derivative drospirenone are the strongest inhibitors with Ki-values similar to hormone levels in pregnant women or women using hormonal contraceptives. Therefore, pregnancy or hormonal contraception may commit these women as high risk groups. The results of this study support the hypothesis that women bear a higher lung cancer risk when smoking because of female sex hormones acting as inhibitors of NNK detoxication.

Objective: To investigate the inhibitory effect of AKR1B10 inhibitor combined with sorafenib on hepatocellular carcinoma (HCC) xenograft growth. Methods: HepG2 xenograft model was established in nude mice. The mice were then randomly divided into four groups: control group, epalrestat monotherapy group, sorafenib monotherapy group and combination treatment group. Tumor volume, tumor weight, T/C ratio and the change in body weight of nude mice in each group were compared to evaluate the curative effect. Immunohistochemistry staining was used to detect the expression of Ki-67 in tumor tissues to evaluate the proliferation status of tumor cells. One-way analysis of variance was used to compare the differences between the groups. Student's t-test was used to test means of two groups and chi-square test was used for multiple samples. Results: The differences of the grafted tumor volume before and after treatment between the control group, epalrestat group, sorafenib group and combined therapy group was 238.940 ± 39.813, 124.991 ± 84.670, -26.111 ± 11.518, and -54.072 ± 17.673(mm(3)), respectively, (F = 37.048, P < 0.001). The tumor mass were 0.273 ± 0.140, 0.158 ± 0.078, 0.079 ± 0.054, 0.045 ± 0.024 (g), (F = 16.594, P < 0.001); T/C ratio were 100%, 57.9%, 28.9%, 16.5%, and Ki-67 positive rate were 23.295 ± 6.218, 13.503 ± 3.392, 7.325 ± 2.257, 4.664 ± 1.189 (%), (χ(2) = 822.203, P < 0.001) . The tumor volume (t = -3.579, P = 0.002) and Ki-67 positive rate (t = -10.003, P < 0.001) in epalrestat monotherapy group were significantly lower than control group. The tumor volume (t = 2.056, P = 0.025), tumor mass (t = 2.101, P = 0.043), and Ki-67 positive rate (t = -2.850, P = 0.005) in combination treatment group were significantly lower than sorafenib monotherapy group. Compared with the control group, the body weight of nude mice in the treatment group decreased to a certain extent, but there was no statistically significant difference between epalrestat monotherapy group and control group (t = -1.599, P = 0.262), and combined therapy and sorafenib monotherapy group (t = -0.051, P = 0.96). Conclusion: AKR1B10 inhibitor enhanced the inhibitory effect of sorafenib on hepatocellular carcinoma xenograft.

Human enzyme aldo-keto reductase family member 1B10 (AKR1B10) has evolved as a tumor marker and promising antineoplastic target. It shares high structural similarity with the diabetes target enzyme aldose reductase (AR). Starting from the potent AR inhibitor IDD388, we have synthesized a series of derivatives bearing the same halophenoxyacetic acid moiety with an increasing number of bromine (Br) atoms on its aryl moiety. Next, by means of IC50 measurements, X-ray crystallography, WaterMap analysis, and advanced binding free energy calculations with a quantum-mechanical (QM) approach, we have studied their structure-activity relationship (SAR) against both enzymes. The introduction of Br substituents decreases AR inhibition potency but improves it in the case of AKR1B10. Indeed, the Br atoms in ortho position may impede these drugs to fit into the AR prototypical specificity pocket. For AKR1B10, the smaller aryl moieties of MK181 and IDD388 can bind into the external loop A subpocket. Instead, the bulkier MK184, MK319, and MK204 open an inner specificity pocket in AKR1B10 characterized by a π-π stacking interaction of their aryl moieties and Trp112 side chain in the native conformation (not possible in AR). Among the three compounds, only MK204 can make a strong halogen bond with the protein (-4.4 kcal/mol, using QM calculations), while presenting the lowest desolvation cost among all the series, translated into the most selective and inhibitory potency AKR1B10 (IC50 = 80 nM). Overall, SAR of these IDD388 polyhalogenated derivatives have unveiled several distinctive AKR1B10 features (shape, flexibility, hydration) that can be exploited to design novel types of AKR1B10 selective drugs.

AKR1B10 is a member of human aldo-keto reductase superfamily, and a promising anti-cancer therapeutic target. In this paper, androst-5-ene-3β-ol, dehydroepiandrosterone, pregnenolone and cholesterol were used as reactants, sixteen products were obtained through Jones reaction and reduction reaction using NaBH4. Their inhibitory activities against AKR1B10 and AKR1B1 were measured. The most active compound (3a) has the IC50 of 0.50μM for AKR1B10, and the most AKR1B10 selective compound (2a) has the IC50 of 0.81μM with AKR1B1/AKR1B10 selectivity of 195. In addition, the binding modes of 2a and 3a in the active site of human AKR1B10 were identified by docking.

Here, we report animal experimental data associated with the article entitled "AKR1B10-inhibitory Selaginella tamariscina extract and amentoflavone decrease the growth of A549 human lung cancer cells in vitro and in vivo" (Jung et al., 2017) [1]. We tested the synergistic anti-tumor effects of Selaginella tamariscina extract and amentoflavone combined with doxorubicin hydrochloride in a nude mouse xenograft model of A549 human lung cancer cells. In our experiment, Selaginella tamariscina extract and amentoflavone were administered orally; and doxorubicin hydrochloride was injected intraperitoneally. We expect our preliminary data will be helpful to the development of the anticancer agent using Selaginella tamariscina extract or amentoflavone.