Polycyclic nitrogen heterocycles as potential thymidine phosphorylase inhibitors: synthesis, biological evaluation, and molecular docking study.

New polycyclic heterocycles were synthesised and evaluated as potential inhibitors of thymidine phosphorylase (TP). Inspired by the pharmacophoric pyrimidinedione core of the natural substrate, four series have been designed in order to interact with large empty pockets of the active site: pyrimidoquinoline-2,4-diones (series A), pyrimidinedione linked to a pyrroloquinoline-1,3-diones (series B and C), the polycyclic heterocycle has been replaced by a pyrimidopyridopyrrolidinetetraone (series D). In each series, the tricyclic nitrogen heterocyclic moiety has been synthesised by a one-pot multicomponent reaction. Compared to 7-DX used as control, 2d, 2l, 2p (series A), 28a (series D), and the open intermediate 30 showed modest to good activities. A kinetic study confirmed that the most active compounds 2d, 2p are competitive inhibitors. Molecular docking analysis confirmed the interaction of these new compounds at the active binding site of TP and highlighted a plausible specific interaction in a pocket that had not yet been explored.

Synthetic and Naturally Occurring Heterocyclic Anticancer Compounds with Multiple Biological Targets.

Cancer is a complex group of diseases initiated by abnormal cell division with the potential of spreading to other parts of the body. The advancement in the discoveries of omics and bio- and cheminformatics has led to the identification of drugs inhibiting putative targets including vascular endothelial growth factor (VEGF) family receptors, fibroblast growth factors (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), and neuropeptide Y4 (NY4), amongst others. Drug resistance, systemic toxicity, and drug ineffectiveness for various cancer chemo-treatments are widespread. Due to this, efficient therapeutic agents targeting two or more of the putative targets in different cancer cells are proposed as cutting edge treatments. Heterocyclic compounds, both synthetic and natural products, have, however, contributed immensely to chemotherapeutics for treatments of various diseases, but little is known about such compounds and their multimodal anticancer properties. A compendium of heterocyclic synthetic and natural product multitarget anticancer compounds, their IC50, and biological targets of inhibition are therefore presented in this review.

Targeting thymidine phosphorylase inhibition in human colorectal cancer xenografts.

Human thymidine phosphorylase (hTP) is overexpressed in several solid tumors and is commonly associated with aggressiveness and unfavorable prognosis. 6-(((1,3-Dihydroxypropan-2-yl)amino)methyl)-5-iodopyrimidine-2,4(1H,3H)-dione (CPBMF-223) is a noncompetitive hTP inhibitor, which has been described as a tumor angiogenesis inhibitor. The present study investigated the effects of CPBMF-223 in a xenograft tumor induced by human colorectal carcinoma cells (HCT-116). Additionally, CPBMF-223 capacity to reduce cell migration, its toxicological profile, and pharmacokinetic characteristics, were also evaluated. The intraperitoneal treatment with CPBMF-223 markedly prevented the relative tumor growth with an efficacy similar to that observed for 5-fluorouracil. Interestingly, number of vessels were significantly decreased in the treated groups. Moreover, CPBMF-223 significantly reduced the migration of cell line HCT-116. In the Ames assay and in an acute oral toxicity test, the molecule did not alter any evaluated parameter. Using the zebrafish toxicity model, cardiac and locomotor parameters were slightly changed. Regarding the pharmacokinetics profile, CPBMF-223 showed clearance of 9.42 L/h/kg after intravenous administration, oral bioavailability of 13.5%, and a half-life of 0.75 h. Our findings shed new light on the role of hTP in colorectal cancer induced by HCT-116 cell in mice, pointing out CPBMF-223 as, hopefully, a promising drug candidate.

Design, synthesis, modelling studies and biological evaluation of 1,3,4-oxadiazole derivatives as potent anticancer agents targeting thymidine phosphorylase enzyme.

A series of novel 1,3,4-oxadiazole derivatives with substituted phenyl ring were designed and synthesized with an objective of discovering newer anti-cancer agents targeting thymidine phosphorylase enzyme (TP). The 1,3,4-oxadiazole derivatives were synthesized by simple and convenient methods in the lab. Chemical structure of the all the synthesized compounds were characterized by IR, 1H NMR and mass spectral methods and evaluated for cytotoxicity by MTT method against two breast cancer cell lines (MCF-7 and MDA-MB-231). Further, results of TP assay identified that 1,3,4-oxadiazole molecules displayed anti-cancer activity partially by inhibition of phosphorylation of thymidine. The TP assay identified SB8 and SB9 as potential inhibitors with anti-cancer activity against both the cell lines. The molecular docking studies recognized the orientation and binding interaction of molecule at the active site amino acid residues of TP (PDB: 1UOU). Acute toxicity studies of compound SB8 at the dose of 5000 mg/kg has identified no signs of clinical toxicity was observed. The SARs study of synthesized derivatives revealed that the substitution of phenyl ring with electron withdrawing group at ortho position showed significant TP inhibitory activity compared to para substitution. The experimental data suggests that 1,3,4-oxadiazole with substituted phenyl can be taken as a lead for the design of efficient TP inhibitors and active compounds which can be taken up for further studies.

Mechanism of acquired 5FU resistance and strategy for overcoming 5FU resistance focusing on 5FU metabolism in colon cancer cell lines.

Fluorouracil (5FU) is converted to its active metabolite fluoro­deoxyuridine monophosphate (FdUMP) through the orotate phosphoribosyl transferase (OPRT)­ribonucleotide reductase (RR) pathway and thymidine phosphatase (TP)­thymidine kinase (TK) pathway and inhibits thymidylate synthase (TS), leading to inhibition of thymidine monophosphate (dTMP) synthesis through a de novo pathway. We investigated the mechanism of 5FU resistance and strategies to overcome it by focusing on 5FU metabolism. Colon cancer cell lines SW48 and LS174T and 5FU­resistant cell lines SW48/5FUR and LS174T/5FUR were used. FdUMP amount was measured by western blotting. The FdUMP synthetic pathway was investigated by combining TP inhibitor (tipiracil hydrochloride; TPI) or RR inhibitor (hydroxyurea; HU) with 5FU. Drug cytotoxicity was observed by crystal violet staining assay. FdUMP was synthesized through the OPRT­RR pathway in SW48 cells but was scarcely synthesized through either the OPRT­RR or TP­TK pathway in SW48/5FUR cells. FdUMP amount in SW48/5FUR cells was reduced by 87% vs. SW48 cells. Expression levels of OPRT and TP were lower in SW48/5FUR when compared with these levels in the SW48 cells, indicating decreased synthesis of FdUMP­led 5FU resistance. These results indicated that fluoro­deoxyuridine (FdU) rather than 5FU promotes FdUMP synthesis and overcomes 5FU resistance. Contrastingly, FdUMP was synthesized through the OPRT­RR and TP­TK pathways in LS174T cells but mainly through the TP­TK pathway in LS174T/5FUR cells. FdUMP amount was similar in LS174T/5FUR vs. the LS174T cells. OPRT and RR expression was lower and TK expression was higher in LS174T/5FUR vs. the LS174T cells, indicating that dTMP synthesis increased through the salvage pathway, thus leading to 5FU resistance. LS174T/5FUR cells also showed cross­resistance to FdU and TS inhibitor, suggesting that nucleoside analogs such as trifluoro­thymidine should be used to overcome 5FU resistance in these cells. 5FU metabolism and mechanisms of 5FU resistance are different in each cell line. Both synthesized FdUMP amount and FdUMP sensitivity should be considered in 5FU­resistant cells.

Three new acrylic acid derivatives from Achillea mellifolium as potential thymidine phosphorylase inhibitor: molecular docking and MD simulation studies.

Discovery of potent inhibitors of thymidine phosphorylase (TP) can offer appropriate approach in cancer treatment owing to it's over expression in various human tumors compared to normal healthy tissues. Thymidine phosphorylase alongside 2-deoxy-D-ribose are reported as promoters of unwanted angiogenesis in cancerous cells. In this study, three new acrylic acid derivatives (1-3) have been isolated from ethyl acetate fraction of Achillea mellifolium. The characterization of these compounds (1-3) was done using UV, IR, 1 D and 2 D-NMR spectroscopy (1H-NMR, 13C-NMR, HMBC, NOESY) and mass spectrometry. The structure of these acrylic acid derivatives were ethyl (E)-3-((1S,5R)-5-methoxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl)acrylate (1), methyl (E)-3-((1S,5R)-5-methoxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl)acrylate (2) and (4S,6R)-6-methoxy-3,5,5-trimethyl-4-((E)-3-oxobut-1-en-1-yl)cyclohex-2-en-1-one (3). Thymidine phosphorylase (TP) inhibition studies showed compound 3 as most active inhibitor of TP with IC50 value 57.81 ± 3.41 while compound 1 and 2 showed IC50 value as 158.9 ± 0.97 and 89.92 ± 0.37, respectively. In addition, molecular docking studies of compound (1-3) were performed to shed light on their binding interaction patterns for binding into active pocket of TP. Similarly, all compounds (1-3) were evaluated for their anti-oxidant potential showing anti-oxidant activities with IC50 value ranging from 49.73 ± 0.41 to 79.81 ± 0.39. Later, these compound-protein (1-3) complexes were further subjected to MD simulations studies (50 ns) involving root mean square deviation, root mean square fluctuation, and secondary structure analysis to explore their binding mode stability inside active pocket. Communicated by Ramaswamy H. Sarma.

Targeting Thymidine Phosphorylase With Tipiracil Hydrochloride Attenuates Thrombosis Without Increasing Risk of Bleeding in Mice.

OBJECTIVE: Current antiplatelet medications increase the risk of bleeding, which leads to a clear clinical need in developing novel mechanism-based antiplatelet drugs. TYMP (Thymidine phosphorylase), a cytoplasm protein that is highly expressed in platelets, facilitates multiple agonist-induced platelet activation, and enhances thrombosis. Tipiracil hydrochloride (TPI), a selective TYMP inhibitor, has been approved by the Food and Drug Administration for clinical use. We tested the hypothesis that TPI is a safe antithrombotic medication. Approach and Results: By coexpression of TYMP and Lyn, GST (glutathione S-transferase) tagged Lyn-SH3 domain or Lyn-SH2 domain, we showed the direct evidence that TYMP binds to Lyn through both SH3 and SH2 domains, and TPI diminished the binding. TYMP deficiency significantly inhibits thrombosis in vivo in both sexes. Pretreatment of platelets with TPI rapidly inhibited collagen- and ADP-induced platelet aggregation. Under either normal or hyperlipidemic conditions, treating wild-type mice with TPI via intraperitoneal injection, intravenous injection, or gavage feeding dramatically inhibited thrombosis without inducing significant bleeding. Even at high doses, TPI has a lower bleeding side effect compared with aspirin and clopidogrel. Intravenous delivery of TPI alone or combined with tissue plasminogen activator dramatically inhibited thrombosis. Dual administration of a very low dose of aspirin and TPI, which had no antithrombotic effects when used alone, significantly inhibited thrombosis without disturbing hemostasis. CONCLUSIONS: This study demonstrated that inhibition of TYMP, a cytoplasmic protein, attenuated multiple signaling pathways that mediate platelet activation, aggregation, and thrombosis. TPI can be used as a novel antithrombotic medication without the increase in risk of bleeding.

Combining Bevacizumab With Trifluridine/Thymidine Phosphorylase Inhibitor Improves the Survival Outcomes Regardless of the Usage History of Bevacizumab in Front-line Treatment of Patients With Metastatic Colorectal Cancer.

BACKGROUND/AIM: The efficacy of trifluridine/thymidine phosphorylase inhibitor (FTD/TPI) plus bevacizumab as later-line treatment for metastatic colorectal cancer (mCRC) has been demonstrated. However, little is known about the impact of a usage history of bevacizumab in front-line treatment on the clinical benefit of combining bevacizumab with FTD/TPI. PATIENTS AND METHODS: A total of 62 patients with mCRC treated with FTD/TPI±bevacizumab was enrolled and assessed for chemotherapeutic efficacy and adverse events. RESULTS: Regardless of the usage history of bevacizumab in front-line treatment, the FTD/TPI plus bevacizumab group had a significantly better progression-free survival rate than the FTD/TPI monotherapy group, and no significant differences in the safety profile were observed between the two groups. CONCLUSION: Combining bevacizumab with FTD/TPI improves the survival outcomes with manageable toxicity, regardless of the usage history of bevacizumab in front-line treatment, in patients with mCRC.

Synthesis, evaluation of thymidine phosphorylase and angiogenic inhibitory potential of ciprofloxacin analogues: Repositioning of ciprofloxacin from antibiotic to future anticancer drugs.

Over expression of thymidine phosphorylase (TP) in various human tumors compared to normal healthy tissue is associated with progression of cancer and proliferation. The 2-deoxy-d-ribose is the final product of thymidine phosphorylase (TP) catalyzed reaction. Both TP and 2-deoxy-d-ribose are known to promote unwanted angiogenesis in cancerous cells. Discovery of potent inhibitors of thymidine phosphorylase (TP) can offer appropriate approach in cancer treatment. A series of ciprofloxacin 2, 3a-3c, 4a-4d, 5a-5b, 6 and 7 has been synthesized and characterized using spectroscopic techniques. Afterwards, inhibitory potential of synthesized ciprofloxacin 2, 3a-3c, 4a-4d, 5a-5b, 6 and 7 against thymidine phosphorylase enzyme was assessed. Out of these twelve analogs of ciprofloxacin nine analogues 3a-3c, 4a-4c, 5a-5b and 6 showed good inhibitory activity against thymidine phosphorylase. Inhibitory activity as presented by their IC50 values was found in the range of 39.71 ± 1.13 to 161.89 ± 0.95 µM. The 7-deazaxanthine was used as a standard inhibitor with IC50 = 37.82 ± 0.93 µM. Furthermore, the chick chorionic allantoic membrane (CAM) assay was used to investigate anti-angiogenic activity of the most active ciprofloxacin-based inhibitor 3b. To enlighten the important binding interactions of ciprofloxacin derivatives with target enzyme, the structure activity relationship and molecular docking studies of chosen ciprofloxacin analogues was discussed. Docking studies revealed key π-π stacking, π-cation and hydrogen bonding interactions of ciprofloxacin analogues with active site residues of thymidine phosphorylase enzyme.

Synthesis of indole based acetohydrazide analogs: Their in vitro and in silico thymidine phosphorylase studies.

In this study, a series of indole based acetohydrazide derivatives (1-22) were synthesized and characterized by 13C NMR, 1H NMR and HREI-MS. The resulted derivatives were tested for thymidine phosphorylase inhibitory potential. These derivatives inhibited thymidine phosphorylase at different concentration ranging from 1.10 ± 0.10 to 41.10 ± 1.10 µM when compared with the standard 7-Deazaxanthine (IC50 value 38.68 ± 1.12 µM). The compound 8 having OH group at 2, 4 and 6 position was found the most potent among the series with IC50 1.10 ± 0.10 µM. The structure activity relationships (SAR) has been established for all compounds keeping in the view the role of substitution and the effect of functional group which significantly affect thymidine phosphorylase activity. The nature of binding interactions of the most potent compounds and active sites of the enzymes was confirmed through molecular docking study.

5-Nitrouracil stabilizes the plasma concentration values of 5-FU in colorectal cancer patients receiving capecitabine.

Capecitabine is selectively converted from 5'-DFUR to 5-fluorouracil (5-FU) in tumours by thymidine phosphorylase (TP). We investigated the addition of 5-nitrouracil (5-NU), a TP inhibitor, into blood samples for precise measurements of plasma 5-FU concentrations. The plasma concentration of 5-FU was measured after capecitabine administration. Two samples were obtained at 1 or 2 h after capecitabine administration and 5-NU was added to one of each pair. Samples were stored at room temperature or 4 °C and 5-FU concentrations were measured immediately or 1.5 or 3 h later. The mean plasma 5-FU concentration was significantly higher at room temperature than at 4 °C (p < 0.001). The 5-FU concentration was significantly increased in the absence of 5-NU than in the presence of 5-NU (p < 0.001). The 5-FU change in concentration was greater in the absence of 5-NU, and reached 190% of the maximum compared with baseline. A significant interaction was found between temperature and 5-NU conditions (p < 0.001). Differences between the presence or absence of 5-NU were greater at room temperature than under refrigerated conditions. 5-FU plasma concentrations after capecitabine administration varied with time, temperature, and the presence or absence of 5-NU. This indicates that plasma concentrations of 5-FU change dependent on storage conditions after blood collection.

Thymidine phosphorylase and prostrate cancer cell proliferation inhibitory activities of synthetic 4-hydroxybenzohydrazides: In vitro, kinetic, and in silico studies.

Over-expression of thymidine phosphorylase (TP) plays a key role in many pathological complications, including angiogenesis which leads to cancer cells proliferation. Thus in search of new anticancer agents, a series of 4-hydroxybenzohydrazides (1-29) was synthesized, and evaluated for in vitro thymidine phosphorylase inhibitory activity. Twenty compounds 1-3, 6-14, 16, 19, 22-24, and 27-29 showed potent to weak TP inhibitory activities with IC50 values in the range of 6.8 to 229.5 µM, in comparison to the standards i.e. tipiracil (IC50 = 0.014 ± 0.002 µM) and 7-deazaxanthine (IC50 = 41.0 ± 1.63 µM). Kinetic studies on selected inhibitors 3, 9, 14, 22, 27, and 29 revealed uncompetitive and non-competitive modes of inhibition. Molecular docking studies of these inhibitors indicated that they were able to interact with the amino acid residues present in allosteric site of TP, including Asp391, Arg388, and Leu389. Antiproliferative (cytotoxic) activities of active compounds were also evaluated against mouse fibroblast (3T3) and prostate cancer (PC3) cell lines. Compounds 1, 2, 19, and 22-24 exhibited anti-proliferative activities against PC3 cells with IC50 values between 6.5 to 10.5 µM, while they were largely non-cytotoxic to 3T3 (mouse fibroblast) cells proliferation. Present study thus identifies a new class of dual inhibitors of TP and cancer cell proliferation, which deserves to be further investigated for anti-cancer drug development.

CORRELATION OF SUBRETINAL HYPERREFLECTIVE MATERIAL MORPHOLOGY AND VISUAL ACUITY IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION.

PURPOSE: To evaluate the association of subretinal hyperreflective material (SHRM) morphological features with visual acuity in eyes with neovascular age-related macular degeneration. METHODS: Retrospective analysis of treatment-naïve patients with neovascular age-related macular degeneration enrolled in randomized anti-vascular endothelial growth factor (VEGF) and anti-platelet-derived growth factor clinical trials. Standardized spectral domain optical coherence tomography images were graded at baseline, 12-week, and 24-week follow-up visits. Masked readers evaluated the morphology of SHRM (reflectivity, shape, anterior, and posterior boundaries) and measured SHRM height, width, and area at the fovea, within the center 1 mm, and outside the center 1 mm. RESULTS: Baseline SHRM characteristics that correlated with worse visual acuity at 12 and 24 weeks included layered appearance (P = 0.006, 0.001), hyperreflective spots in SHRM (P = 0.001, 0.011), and separation between SHRM and outer retina (P = 0.03, 0.019). The disappearance of SHRM correlated with better visual acuity at Weeks 12 and 24 (P < 0.001). Layered appearance of SHRM at baseline was significantly associated with increased reflectivity at Weeks 12 and 24 (P = 0.009, 0.003). Decreasing reflectivity of SHRM lesion at Weeks 12 and 24 correlated with better visual acuity (P < 0.01, 0.01). Increased width and area of baseline SHRM at the foveal center correlated with worse visual acuity at 12 (P < 0.001, <0.001) and 24 weeks (<0.001, <0.001). CONCLUSION: Several attributes of SHRM including, layered appearance, increased reflectivity, larger size, and hyperreflective spots correlated with worse visual acuity at 12- and 24-week follow-ups. Baseline SHRM characteristics can help practitioners predict visual and morphological prognosis and guide therapy.

Natural compounds as angiogenic enzyme thymidine phosphorylase inhibitors: In vitro biochemical inhibition, mechanistic, and in silico modeling studies.

Natural flora is the richest source of novel therapeutic agents due to their immense chemical diversity and novel biological properties. In this regard, eighteen natural products belonging to different chemical classes were evaluated for their thymidine phosphorylase (TP) inhibitory activity. TP shares identity with an angiogenic protein platelet derived endothelial cell growth factor (PD-ECGF). It assists tumor angiogenesis and is a key player in cancer progression, thus an ideal target to develop anti-angiogenic drugs. Eleven compounds 1-2, 5-10, 11, 15, and 18 showed a good to weak TP inhibitory activity (IC50 values between 44.0 to 420.3 µM), as compared to standards i.e. tipiracil (IC50 = 0.014 ± 0.002 µM) and 7-deazaxanthine (IC50 = 41.0 ± 1.63 µM). Kinetic studies were also performed on active compounds, in order to deduce the mechanism of ligand binding to enzyme. To get further insight into receptor protein (enzyme) and ligand interaction at atomic level, in- sillico studies were also performed. Active compounds were finally evaluated for cytotoxicity test against mouse fibroblast (3T3) cell line. Compound 18 (Masoprocol) showed a significant TP inhibitory activity (IC50 = 44.0 ± 0.5 µM). Kinetic studies showed that it inhibits the enzyme in a competitive manner (Ki = 25.6 ± 0.008 µM), while it adopts a binding pose different than the substrate thymidine. It is further found to be non-toxic in MTT cytotoxicity assay. This is the first report on TP inhibitory activity of several natural compounds, some of which may serve as leads for further research towards drug the development.

The safety and efficacy of trifluridine-tipiracil for metastatic colorectal cancer: A pharmacy perspective.

PURPOSE: The pharmacology, pharmacokinetics, clinical efficacy, safety, dosing, and place in therapy of trifluridine-tipiracil are reviewed. SUMMARY: Trifluridine-tipiracil is an oral antineoplastic agent consisting of trifluridine (a trifluorothymidine, a thymidine-based nucleoside analog) and tipiracil (a thymidine phosphorylase inhibitor), at a molar ratio of 1:0.5. Tipiracil blocks the degradation of trifluridine by thymidine phosphorylase, which improves the bioavailability of trifluridine and allows for oral administration. A Phase III study comparing trifluridine-tipiracil versus placebo in metastatic colorectal cancer (mCRC) patients refractory to or intolerant of standard therapy (n = 800) showed a benefit in overall survival (the primary endpoint) and progression-free survival compared with placebo. The most common grade ≥ 3 adverse events in trifluridine-tipiracil groups in Phase II and III trials were neutropenia, anemia, and leukopenia. The recommended dose of trifluridine-tipiracil is 35 mg/m2 twice a day after meals in a 28-day cycle comprising 2 weeks of 5 days of treatment and 2 days of rest (days 1-5 and 8-12 [every] 28 days), followed by 2 weeks of rest. Trifluridine-tipiracil is approved for the treatment of patients with mCRC previously treated with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy, an antivascular endothelial growth factor biological therapy and, if RAS wild-type, an antiepidermal growth factor receptor therapy. CONCLUSION: Trifluridine-tipiracil is a new treatment option for patients with mCRC who have received at least 2 prior lines of standard chemotherapy (including fluoropyrimidine, oxaliplatin, irinotecan, bevacizumab, and an antiepidermal growth factor receptor antibody in patients with KRAS wild-type tumors). Ongoing trials are investigating trifluridine/tipiracil in combination with other anticancer agents for mCRC and its use in other malignancies, such as metastatic gastric cancer.

Synthesis, thymidine phosphorylase, angiogenic inhibition and molecular docking study of isoquinoline derivatives.

Isoquinoline analogues (KA-1 to 16) have been synthesized and evaluated for their E. coli thymidine phosphorylase inhibitory activity. Except compound 11, all other analogs showed outstanding thymidine inhibitory potential ranging in between 4.40 ±â€¯0.20 to 69.30 ±â€¯1.80 µM when compared with standard drug 7-Deazaxanthine (IC50 = 38.68 ±â€¯4.42 µM). Structure Activity Relationships has been established for all compounds, mainly based on substitution pattern on phenyl ring. All analogs were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR and EI-MS. The binding interactions of isoquinoline analogues with the active site of TP enzyme, the molecular docking studies were performed. Furthermore, the angiogenic inhibitory potentials of isoquinoline analogues (KA-1-9, 14, 12 and 16) were determined in the presence of standard drug Dexamethasone based on percentage inhibitions at various concentrations. Herein this work analogue KA-12, 14 and 16 emerged with most potent angiogenic inhibitory potentials among the synthesized analogues.

Synthesis of Thymidine Phosphorylase Inhibitor Based on Quinoxaline Derivatives and Their Molecular Docking Study.

We have synthesized quinoxaline analogs (1⁻25), characterized by ¹H-NMR and HREI-MS and evaluated for thymidine phosphorylase inhibition. Among the series, nineteen analogs showed better inhibition when compared with the standard inhibitor 7-Deazaxanthine (IC50 = 38.68 ± 4.42 µM). The most potent compound among the series is analog 25 with IC50 value 3.20 ± 0.10 µM. Sixteen analogs 1, 2, 3, 4, 5, 6, 7, 12, 13, 14, 15, 16, 17, 18, 21 and 24 showed outstanding inhibition which is many folds better than the standard 7-Deazaxanthine. Two analogs 8 and 9 showed moderate inhibition. A structure-activity relationship has been established mainly based upon the substitution pattern on the phenyl ring. The binding interactions of the active compounds were confirmed through molecular docking studies.

Kinetics mechanism and regulation of native human hepatic thymidine phosphorylase.

Thymidine phosphorylase (TP; EC 2.4.2.4) catalyzes the reversible phosphorolysis of thymidine, deoxyuridine, and their analogues to their respective nucleobases and 2-deoxy-α-d-ribose-1-phosphate (dRib-1-P). TP is a key enzyme in the pyrimidine salvage pathways. Activity of the enzyme is crucial in angiogenesis, cancer chemotherapy, radiotherapy, and tumor imaging, Nevertheless, a complete set of kinetic parameters has never been reported for any human TP. This study describes the kinetic mechanism and regulation of native human hepatic TP. The liver is a main site of pyrimidine metabolism and contains high levels of TP. Initial velocity and product inhibition studies demonstrated that the basic mechanism of this enzyme is a sequential random bi-bi mechanism. Initial velocity studies showed an intersecting pattern, consistent with substrate-enzyme-co-substrate complex formation, and a binding pattern indicating that the binding of the substrate interferes with the binding of the co-substrate and vice versa. Estimated kinetic parameters were KThymidine = 284 ± 55, KPi = 5.8 ± 1.9, KThymine = 244 ± 69, and KdRib-1-P = 90 ± 33 µM. Thymine was a product activator, but becomes a substrate inhibitor at concentrations eight times higher than its Km. dRib-1-P was a non-competitive product inhibitor of the forward reaction. It bounded better to the Enzyme●Pi complex than the free enzyme, but had better affinity to the free enzyme than the Enzyme●Thymidine complex. In the reverse reaction, dRib-1-P enhanced the binding of thymine. The enhancement of the thymine binding along with the fact that dRib-1-P was a non-competitive product inhibitor suggests the presence of another binding site for dRib-1-P on the enzyme.

Inhibition of thymidine phosphorylase expression by Hsp90 inhibitor potentiates the cytotoxic effect of salinomycin in human non-small-cell lung cancer cells.

Salinomycin is a polyether ionophore antibiotic having anti-tumorigenic property in various types of cancer. Elevated thymidine phosphorylase (TP) levels, a key enzyme in the pyrimidine nucleoside salvage pathway, are associated with an aggressive disease phenotype and poor prognoses. Heat shock protein 90 (Hsp90) is a ubiquitous molecular chaperone that is responsible for the stabilization and maturation of many oncogenic proteins. In this study, we report whether Hsp90 inhibitor 17-AAG could enhance salinomycin-induced cytotoxicity in NSCLC cells through modulating TP expression in two non-small-cell lung cancer (NSCLC) cell lines, A549 and H1975. We found that salinomycin increased TP expression in a MKK3/6-p38 MAPK activation manner. Knockdown of TP using siRNA or inactivation of p38 MAPK by pharmacological inhibitor SB203580 enhanced the cytotoxic and growth inhibition effects of salinomycin. In contrast, enforced expression of MKK6E (a constitutively active form of MKK6) reduced the cytotoxicity and cell growth inhibition of salinomycin. Moreover, Hsp90 inhibitor 17-AAG enhanced cytotoxicity and cell growth inhibition of salinomycin in NSCLC cells, which were associated with down-regulation of TP expression and inactivation of p38 MAPK. Together, the Hsp90 inhibition induced TP down-regulation involved in enhancing the salinomycin-induced cytotoxicity in A549 and H1975 cells.