Aminoimidazole Carboxamide Ribonucleotide Research Articles

ZNF695, A Potential Prognostic Biomarker, Correlates with Im mune Infiltrates in Cervical Squamous Cell Carcinoma and Endoce rvical Adenocarcinoma: Bioinformatic Analysis and Experimental Verification.

The role of Zinc Finger Protein 695 (ZNF695) is unclear in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC). The objective of this study was to conduct a comprehensive analysis and experimental validation of ZNF695 in CESC. The study investigated the expression of ZNF695 in both pan-cancer and CESC, utilizing data from The Cancer Genome Atlas (TCGA) database to assess its diagnostic value. The present study investigated the association between ZNF695 expression levels and clinical characteristics, as well as prognosis, in patients with CESC. The study explored potential regulatory networks involving ZNF695, including its association with immune infiltration, immune score, stemness index based on mRNA expression (mRNAsi), and drug sensitivity in CESC. We explored the expression of ZNF695 in CESC single cells. ZNF695 expression was validated using GSE29570. ZNF695 was found to be aberrantly expressed in pan-cancer and CESC. There was a significant correlation observed between an elevated level of ZNF695 expression in patients with CESC and histological grade (p = 0.017). Furthermore, a strong association was found between high ZNF695 expression in CESC patients and poorer overall survival (OS) (HR: 1.87; 95% CI: 1.17-3.00; p = 0.009), Progression-free Survival (PFS) (HR: 1.86; 95% CI: 1.16-2.98; p = 0.010), and Disease-specific Survival (DSS) (HR: 1.98; 95% CI: 1.15-3.42; p = 0.014). The expression of ZNF695 in CESC patients (p = 0.006) was identified as an independent prognostic determinant. ZNF695 was associated with steroid hormone biosynthesis, oxidative phosphorylation, and so on. ZNF695 expression correlated with immune infiltration, immune score, and mRNAsi in CESC. ZNF695 expression significantly and negatively correlated with AICA ribonucleotide, BIX02189, QL-XI-92, STF-62247, and SNX-2112 in CESC. ZNF695 gene was upregulated in CESC tissues and cell lines. ZNF695 was significantly upregulated in the CESC cell lines. ZNF695 may be a potential prognostic biomarker and immunotherapeutic target for CESC patients.

OR05-02 Silencing Of Adenylosuccinate Lyase Impairs Growth And Perturbs Mitochondrial Function Of Endocrine Therapy Resistant Breast Cancer Cells

Abstract Disclosure: A.K. Yadav: None. L. Jin: None. R. Clarke: None. S. Sengupta: None. The estrogen receptor positive (ER+) subtype comprises of ∼80% of all breast cancers and is the major contributor to cancer related deaths in women. While ER+ breast cancers respond to treatment with endocrine therapies (ET) such as tamoxifen, Fulvestrant and aromatase inhibitors, a major limitation is emergence of resistance to ET resulting from adaptive pathways that promote relapse and disease progression. Hence, there is an urgent need for identification and validation of new molecular targets for potential therapeutic treatment of ET resistant-ER+ breast cancer. Here, we have determined the role of adenylosuccinate lyase (ADSL), a crucial enzyme involved in the de novo purine synthesis pathway, as a potential molecular target for ER+ breast cancer cells. ADSL enzyme catalyzes two non-sequential steps in de-novo purine synthesis pathway that produces aminoimidazole carboxamide ribonucleotide (AICAR) and adenosine monophosphate (AMP); fumarate is generated as a byproduct. We observed higher protein expression of ADSL in LCC9 (endocrine therapy crossresistant cells) when compared with LCC1 or MCF-7 (antiestrogen sensitive) cells. Additionally, T47D-4HT cells (also endocrine therapy resistant) also expressed modestly higher ADSL protein level in comparison to its parental endocrine therapy sensitive T47D-A18 cells. Notably, siRNA-mediated knockdown of ADSL in both LCC9 and T47D-4HT cells leads to strong inhibition of cell proliferation, long-term colony, and spheroid formation. Furthermore, ADSL depletion in LCC9 increased the accumulation of cells in G0/G1 phase along with elevated protein expression of cyclin D1. In T47D-4HT cells, ADSL knockdown caused cells to accumulate in S-phase, with a reduction of total cyclin D1 protein levels. Further investigation revealed that ADSL knockdown decreased ATP levels and mitochondrial membrane potential in both LCC9 and T47D-4HT cells and significantly reduced the basal oxygen consumption rate (OCR) and maximal respiration capacity. Notably, addition of AICAR (100 µM) to ADSL deficient LCC9 cells partially rescued cell proliferation, colony formation, and restored the mitochondrial membrane potential. In clinical datasets higher expression of ADSL transcripts correlates with poor relapse free survival in ER+ breast cancer patients treated with endocrine therapies. Overall, our results indicate that ADSL-mediated de novo purine synthesis plays an important role in growth and proliferation of endocrine therapy resistant ER+ breast cancer cells through mitochondrial function. Therefore, targeting ADSL is a novel potential therapeutic approach for ER+ endocrine resistance breast cancer. Presentation: Thursday, June 15, 2023

Ascophyllum nodosum polysaccharide regulates gut microbiota metabolites to protect against colonic inflammation in mice.

Ascophyllum nodosum polysaccharide (ANP) can protect against colonic inflammation but the underlying mechanism is still unclear. This study has determined the metabolites of gut microbiota regulated by ANP to reveal the mechanism of the anti-inflammation effect of ANP. Using an in vitro colonic fermentation model, the results indicate that gut microbiota could utilize a proportion of ANP to increase the concentrations of short-chain fatty acids (SCFAs) and decrease ammonia content. Metabolomics revealed that 46 differential metabolites, such as betaine, L-carnitine, and aminoimidazole carboxamide ribonucleotide (AICAR), could be altered by ANP. Metabolic pathway analysis showed that ANP mainly up-regulated the phenylalanine, tyrosine, and tryptophan biosynthesis and aminoacyl-tRNA biosynthesis, which were negatively correlated with inflammation progression. Interestingly, these metabolites associated with inflammation were also up-regulated by ANP in colitis mice, including betaine, L-carnitine, AICAR, N-acetyl-glutamine, tryptophan, and valine, which were mainly associated with amino acid metabolism and aminoacyl-tRNA biosynthesis. Furthermore, the metabolites modulated by ANP were associated with the relative abundances of Akkermansia, Bacteroides, Blautia, Coprobacillus, Enterobacter, and Klebsiella. Additionally, based on VIP values, betaine is a key metabolite after the ANP supplement in vitro and in vivo. As indicated by these findings, ANP can up-regulate the production of SCFAs, betaine, L-carnitine, and AICAR and aminoacyl-tRNA biosynthesis to protect against colonic inflammation and maintain intestinal health.

Metabolites of De Novo Purine Synthesis: Metabolic Regulators and Cytotoxic Compounds.

Cytotoxicity of de novo purine synthesis (DNPS) metabolites is critical to the pathogenesis of three known and one putative autosomal recessive disorder affecting DNPS. These rare disorders are caused by biallelic mutations in the DNPS genes phosphoribosylformylglycineamidine synthase (PFAS), phosphoribosylaminoimidazolecarboxylase/phosphoribosylaminoimidazolesuccinocarboxamide synthase (PAICS), adenylosuccinate lyase (ADSL), and aminoimidazole carboxamide ribonucleotide transformylase/inosine monophosphate cyclohydrolase (ATIC) and are clinically characterized by developmental abnormalities, psychomotor retardation, and nonspecific neurological impairment. At a biochemical level, loss of function of specific mutated enzymes results in elevated levels of DNPS ribosides in body fluids. The main pathogenic effect is attributed to the accumulation of DNPS ribosides, which are postulated to be toxic to the organism. Therefore, we decided to characterize the uptake and flux of several DNPS metabolites in HeLa cells and the impact of DNPS metabolites to viability of cancer cell lines and primary skin fibroblasts. We treated cells with DNPS metabolites and followed their flux in purine synthesis and degradation. In this study, we show for the first time the transport of formylglycinamide ribotide (FGAR), aminoimidazole ribotide (AIR), succinylaminoimidazolecarboxamide ribotide (SAICAR), and aminoimidazolecarboxamide ribotide (AICAR) into cells and their flux in DNPS and the degradation pathway. We found diminished cell viability mostly in the presence of FGAR and AIR. Our results suggest that direct cellular toxicity of DNPS metabolites may not be the primary pathogenetic mechanism in these disorders.

Insulin‐Resistant Pathways Are Associated With Disease Activity in Rheumatoid Arthritis and Are Subject to Disease Modification Through Metabolic Reprogramming: A Potential Novel Therapeutic Approach

To investigate a role for insulin-resistant pathways in inflammation and therapeutic targeting for disease modification in rheumatoid arthritis (RA). RA disease activity and cardiovascular risk factors, including insulin resistance and body mass index (BMI), were assessed in an Irish RA cohort. Glucose transporter 1 (GLUT-1) and GLUT-4 activity in RA and osteoarthritis (OA) synovial tissue was examined using immunohistochemistry. Spontaneous release of proinflammatory mediators from ex vivo RA synovial explants and primary synovial fibroblast (SF) cell culture supernatants was quantified by enzyme-linked immunosorbent assay. Phosphorylated AMP-activated protein kinase (p-AMPK) and GLUT-1 protein expression was analyzed by Western blotting. Cellular glycolytic and oxidative phosphorylation was assessed using extracellular flux analysis. Insulin resistance was independently associated with both BMI (unstandardized coefficient B 0.113 [95% confidence interval (95% CI) 0.059-0.167]; P < 0.001) (n = 61) and swollen joint count in 28 joints (SJC28) (B 0.114 [95% CI 0.032-0.197]; P = 0.008) (n = 61). Increased GLUT-1 expression in RA synovium (n = 26) versus OA synovium (n = 16) was demonstrated (P = 0.0003), with increased expression in the lining, sublining, and vascular regions. In contrast, decreased GLUT-4 expression in the RA lining layer (n = 21) versus the OA lining layer (n = 8) was observed (P = 0.0358). Decreased GLUT-1 protein expression was observed in parallel with increased p-AMPK protein expression in SFs in the presence of metformin (n = 4). Metformin increased glycolytic activity and decreased oxidative phosphorylation in RASFs (n = 7) (P < 0.05 for both). Metformin or aminoimidazole carboxamide ribonucleotide presence decreased spontaneous production of interleukin-6 (IL-6), IL-8, and monocyte chemotactic protein 1 in RA synovial explants and SFs (n = 5-7). Insulin resistance is significantly associated with BMI and synovitis in RA, suggesting distinct interplay between glucose availability and inflammation in RA. Furthermore, the effect of metformin on proinflammatory mechanisms suggests a role for AMPK-modifying compounds in the treatment of RA.

Abstract 4800: Targeting mitochondrial and cytosolic one-carbon metabolism in epithelial ovarian cancer via folate receptor alpha

Abstract Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. Even though most patients initially respond to platinum-based therapy, the likelihood of disease reoccurrence is virtually 100%. Thus, there is an urgent need for new tumor-selective therapies for EOC. One such treatment option involves targeting tumors via folate receptor alpha (FRα) which is overexpressed in up to 90% of EOCs and shows increasing expression with stage and grade of disease. Our laboratory discovered novel 5-substituted pyrrolo[3,2-d]pyrimidine analogs (AGF291, AGF320, AGF347, AGF359 and AGF362) which inhibit mitochondrial one-carbon (C1) metabolism at serine hydroxymethyltransferase (SHMT) 2, with secondary inhibitions at cytosolic enzyme targets including those in de novo purine biosynthesis and SHMT1. Potent inhibition was seen toward isogenic Chinese hamster ovary (CHO) cell lines individually expressing FRα, the reduced folate carrier (RFC, ubiquitously expressed tissue folate transporter) and the proton-coupled folate transporter (PCFT, expressed in a limited number of normal tissues and inactive at normal pH, and several solid tumors at acidic pH including EOC), and with FRα-expressing tumor cells, including KB and IGROV1, a human EOC cell line. Inhibitory potencies were in order, AGF347 &amp;gt; AGF362 &amp;gt;&amp;gt; AGF291 = AGF320 = AGF359. Drug effects were substantially reduced with excess folic acid, confirming FRα-mediated drug uptake. Toward cisplatin resistant SKOV3, TOV112D and A2780 EOC cells, inhibition in the nanomolar range was detected with all compounds. Excess folic acid abrogated drug effects to varying degrees, suggesting significant uptake by the PCFT and/or the RFC, in addition to FRα. Short-term (5 minutes) cell uptake assays with the EOC cell lines and [3H]AGF347 confirmed transport by PCFT and RFC. With sustained exposures resulting in steady state AGF347 accumulations under both physiologic (pH 7.2) and acidic (pH 6.8, approximating the tumor microenvironment) conditions, FRα uptake predominated. [3H]AGF347 treatment of IGROV1 EOC resulted in substantial drug accumulation in both cytosol and mitochondria. Inhibition of cell proliferation for all analogs was reversed by addition of both glycine and adenosine, implicating C1 metabolism in mitochondria including SHMT2 and de novo purine biosynthesis in the cytosol as the targeted pathways; protection by 5-aminoimidazole-4-carboxamide (AICA) with or without glycine was incomplete, implying direct targeting of AICA ribonucleotide formyltransferase (AICARFTase), the second folate-dependent enzyme in purine biosynthesis. Our studies describe first-in-class FRα-selective compounds targeting mitochondrial and cytosolic C1 metabolism, with potent activity against EOC, including cisplatin resistant EOC. Citation Format: Adrianne Wallace-Povirk, Carrie O’Connor, Aamod Dekhne, Zhanjun Hou, Md. Junayed Nayeen, Khushbu Shah, Aleem Gangjee, Larry Matherly. Targeting mitochondrial and cytosolic one-carbon metabolism in epithelial ovarian cancer via folate receptor alpha [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4800.

Modulation of the de novo purine nucleotide pathway as a therapeutic strategy in mitochondrial myopathy.

Mitochondrial myopathy (MM) is characterised by muscle weakness, exercise intolerance and various histopathological changes. Recently, a subset of MM has also been associated with aberrant activation of mammalian target of rapamycin complex 1 (mTORC1) in skeletal muscle. This aberrant mTORC1 activation promotes increased de novo nucleotide synthesis, which contributes to abnormal expansion and imbalance of skeletal muscle deoxyribonucleoside triphosphates (dNTP) pools. However, the exact mechanism via which mTORC1-stimulated de novo nucleotide biosynthesis ultimately disturbs muscle dNTP pools remains unclear. In this article, it is proposed that mTORC1-stimulated de novo nucleotide synthesis in skeletal muscle cells with respiratory chain dysfunction promotes an asymmetric increase of purine nucleotides, probably due to NAD+ deficiency. This in turn could disrupt purine nucleotide-dependent allosteric feedback regulatory mechanisms, ultimately leading to dNTP pools aberration. Pharmacological down-modulation of aminoimidazole carboxamide ribonucleotide transformylase/inosine monophosphate cyclohydrolase (ATIC) activity is also proposed as a potential therapeutic strategy in MM exhibiting mTORC1-driven abnormal metabolic reprogramming, including aberrant dNTPs pools.

Abstract 2798: Folate receptor-targeted cancer chemotherapy with novel 6-substituted thieno[2,3-d]pyrimidine compounds with nitrogen and fluorine containing aromatic side chains as de novo purine biosynthesis inhibitors

Abstract Targeted cancer chemotherapy inhibits the growth of cancer cells by interfering with critical pathways required for tumor progression. Three major transporters are involved in membrane transport of folates into mammalian cells and include the reduced folate carrier (RFC), folate receptors (FRs) α and β, and proton-coupled folate transporter (PCFT). The clinically used agents methotrexate, pemetrexed, raltitrexed and pralatrexate are all transported by the ubiquitously expressed RFC into both tumor cells and normal tissues, and hence are non-selective. The lack of tumor selectivity results in dose-limiting toxicity. We reported 6-substituted thieno[2,3-d]pyrimidine (6TP) compounds with a phenyl side-chain and bridge lengths of 2-8 carbons as potent inhibitors that are selectively transported by FRs over RFC and inhibit proliferation of FR-expressing KB tumor cells with low nanomolar IC50s. The most potent compound (AGF50), a thieno[2,3-d]pyrimidine with a 4-carbon bridge and a phenyl side chain, showed FR selectivity over RFC and potent inhibition of de novo purine biosynthesis at least in part due to inhibition of glycinamide ribonucleotide formyltransferase (GARFTase). In this report, fluorine was strategically placed on the aryl side chain which could induce conformational restriction due to possible intramolecular fluorine-hydrogen bonding interactions. We found that fluorine substitution on the phenyl side-chain, ortho (o-) to L-glutamate (AGF304) improved potency and selectivity for FRα (4.5-fold) and FRβ (20-fold) compared to AGF50, as reflected in inhibition of proliferation of Chinese hamster ovary cells expressing human FRs. The pyridine nitrogen can also form H-bonds with NH of the L- glutamate amide, which could improve the potency and selectivity of 6TPs with pyridine side-chains. Analogs with systematic pyridine side-chain modifications, as well as ortho fluorine substitution on the pyridine ring, were designed, modeled, and synthesized. The 2',5'-pyridine analog AGF132 was ~9-fold more active toward FRα-expressing cells but approximately equipotent toward FRβ. The fluorinated 2',5'-pyridine analog AGF305 was ~5-fold less potent for FRα and was &amp;gt;50-fold more potent for FRβ compared to AGF132. AGF132, AGF304 and AGF305 inhibited growth of KB human tumor cells approximately equivalent to AGF50. Whereas adenosine completely protected cells from growth inhibition by the 6TPs, protection with 5-aminoimidazole-4-carboxamide (AICA) was incomplete, suggesting inhibition at AICA ribonucleotide formyltransferase (AICARFTase), along with GARFTase. Our 6TPs with aryl side-chain modifications are slated for further preclinical studies to identify potential clinical candidates that target the de novo purine biosynthesis pathway. Citation Format: Nian Tong, Aleem Gangjee, Adrianne W. Povrik, Carrie O. Connor, Jianjun Hou, Larry Matherly. Folate receptor-targeted cancer chemotherapy with novel 6-substituted thieno[2,3-d]pyrimidine compounds with nitrogen and fluorine containing aromatic side chains as de novo purine biosynthesis inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2798.

Abstract 3980: Dual targeting mitochondrial and cytosolic one-carbon metabolism via the proton-coupled folate transporter with novel 5-substituted pyrrolo[3,2-d]pyrimidine antifolates

Abstract Cellular one-carbon (1C) metabolism generates a host of metabolites especially critical to cancer cells. Classical 1C inhibitors often primarily target a single enzyme, commonly leading to drug resistance and necessitating the development of novel compounds targeting multiple enzymes. We synthesized several novel 5-substituted pyrrolo[3,2-d]pyrimidine compounds (AGF291, AGF320, and AGF347) with transport by the proton-coupled folate transporter (PCFT), a folate transporter with a narrow physiological niche, but commonly expressed in many solid tumors. These analogs showed substantial inhibition in proliferation assays with Chinese hamster ovary sublines engineered to individually express PCFT or the ubiquitously-expressed reduced folate carrier (the major tissue folate transporter), as well as in the PCFT-expressing human cancer cell lines H460 (large cell lung carcinoma), HCT-116 (colorectal carcinoma), and MIA PaCa-2 (pancreatic ductal adenocarcinoma). Full abrogation of inhibitory effects for all compounds required co-treatment with both adenosine and glycine, suggesting dual-targeting of cytosolic de novo purine biosynthesis and mitochondrial 1C/glycine metabolism. For cytosolic de novo purine biosynthesis, lack of protection by 5-aminoimidazole-4-carboxamide (AICA) suggested AICA ribonucleotide formyltransferase (AICARFTase), the second folate-dependent enzyme, as the likely enzyme target. AICARFTase inhibition was confirmed in intact H460 and HCT-116 cells by measuring accumulation of AICAR by targeted metabolomics. Targeting of mitochondrial enzymes in H460 and HCT-116 cells was suggested by selective inhibition of incorporation of [3-14C]serine over [14C]formate into the purine intermediate [14C]formyl glycinamide ribonucleotide. [2,3,3-2H]Serine isotope label scrambling analysis confirmed the mitochondrial target to be serine hydroxymethyltransferase2 (SHMT2). SHMT2 is a potentially promising anticancer drug target as its expression is highly correlated with the malignant phenotype across a broad spectrum of cancers beyond lung and colon, including breast, glioma, and liver. Indeed, our initial in-vivo studies with AGF291 suggest potent efficacy toward both MIA PaCa-2 and H460 xenograft mouse models. Our studies demonstrate the potential for tumor-selective dual targeting of both mitochondrial and cytosolic 1C metabolism to overcome resistance to classical 1C inhibitors. Citation Format: Aamod S. Dekhne, Gregory S. Ducker, Josephine Frühauf, Khushbu Shah, Md. Junayed Nayeen, Adrianne Wallace-Povirk, Carrie O'Connor, Zhanjun Hou, Lisa Polin, Aleem Gangjee, Joshua D. Rabinowitz, Larry H. Matherly. Dual targeting mitochondrial and cytosolic one-carbon metabolism via the proton-coupled folate transporter with novel 5-substituted pyrrolo[3,2-d]pyrimidine antifolates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3980.

Analysis of substrate binding in individual active sites of bifunctional human ATIC

Aminoimidazolecarboxamide ribonucleotide formyl transferase (AICARFT): Inosine monophosphate cyclohydrolase (IMPCH, collectively called ATIC) is a bifunctional enzyme that catalyses the penultimate and final steps in the purine de novo biosynthesis pathway. The bifunctional protein is dimeric and each monomer contains two different active sites both of which are capable of binding nucleotide substrates, this means to a potential total of four distinct binding events might be observed. Within this work we used a combination of site-directed and truncation mutants of ATIC to independently investigate the binding at these two sites using calorimetry. A single S10W mutation is sufficient to block the IMPCH active site allowing investigation of the effects of mutation on ligand binding in the AICARFT active site. The majority of nucleotide ligands bind selectively at one of the two active sites with the exception of xanthosine monophosphate, XMP, which, in addition to binding in both AICARFT and IMPCH active sites, shows evidence for cooperative binding with communication between symmetrically-related active sites in the two IMPCH domains. The AICARFT site is capable of independently binding both nucleotide and folate substrates with high affinity however no evidence for positive cooperativity in binding could be detected using the model ligands employed in this study.

Beneficial effect of methotrexate on a case of Nakajo-Nishimura syndrome

Nakajo-Nishimura syndrome (NNS) is a very rare autosomal recessively-inherited autoinflammatory disorder that onsets in infancy with pernio-like rashes and gradually develops into partial lipodystrophy, accompanied with remittent fever and nodular skin eruptions. This disease is caused by a unique mutation of the PSMB8 gene, which not only impairs an enzymatic activity of the encoding beta5i subunit, but also disturbs formation of the immunoproteasome complex. As the pathogenesis for NNS, cellular accumulation of ubiquitinated and oxidized proteins due to immunoproteasome deficiency is considered to cause MAP kinase activation with nuclear accumulation of phosphorylated p38 and following IL-6 production. The treatment for Nakajo-Nishimura syndrome has not been established. Inflammatory attacks can temporarily respond to the oral administration of high-dose corticosteroid, but they easily recur by tapering the dose of corticosteroid. Furthermore, the high-dose corticosteroid therapy has various side effects such as growth failure in infancy. In our child case of NNS (Kunimoto et al, Dermatology 2013), additional administration of methotrexate (MTX) significantly decreased a frequency of febrile attacks, in comparison to the treatment with oral corticosteroid alone. Notably, effectiveness of MTX was previously described on some infant cases of CANDLE syndrome, another PSMB8-mutated proteasome-associated autoinflammatory syndrome (PRAAS). MTX is known to execute anti-inflammatory effects through inhibition of folic acid-dependent enzymes, including dihydrofolate reductase (DHFR) and aminoimidazole carboxamide ribonucleotide transformylase (ATIC). ATIC inhibition causes accumulation of intracellular aminoimidazole carboxamide ribonucleotide and inhibits AMP deaminase, to increase the production of adenosine. Adenosine can inhibit superoxide production of neutrophils and their attachment to endothelial cells. As preliminary results, increased ROS production has been observed in primary neutrophils of NNS patients, suggesting one of the points that MTX affects.

Abstract 4481: Tumor-targeting with novel 6-substituted thienoyl[2,3-d]pyrimidine antifolates via cellular uptake by folate receptor α, and inhibition of de novo purine nucleotide biosynthesis

Abstract Recent interest has focused on folate receptor (FR) α in delivering folate-based therapeutics to solid tumors, as FRα is expressed in human tumors, notably ovarian and non-small cell lung cancers. While FRα is present in normal epithelial tissues, this occurs at apical membranes where it is inaccessible to the circulation. Selectivity of FR-targeted agents would be enhanced if these were poor substrates for the ubiquitous reduced folate carrier (RFC). We previously described 6-substituted thieno[2,3-d]pyrimidine benzoyl antifolates with varying bridge lengths (n = 2-8 carbons) as potent and selective inhibitors of tumor cells that express FRs. The most potent compound (AGF50) included a 4-carbon bridge and showed FRα selectivity and inhibition of de novo purine biosynthesis. To investigate the role of the side-chain aromatic ring in transport and pathway inhibition, we synthesized AGF50 analogs with a variety of aryl side-chain modifications (AGF102, AGF103, AGF55, AGF65, and AGF132). The various 6-substituted thienoyl[2,3-d]pyrimidine antifolates were tested in proliferation assays with isogenic Chinese hamster ovary (CHO) sublines expressing RFC, proton-coupled folate transporter (PCFT), or FRα, and with KB tumor cells. The analogs were inert toward RFC- and PCFT-expressing cells. Toward FRα-expressing CHO and KB cells, inhibitory potencies were in the order, AGF102 = AGF132 = AGF103 &amp;gt; AGF50 &amp;gt; AGF64 &amp;gt;&amp;gt; AGF55, with IC50s ranging from ∼ 1 nM to 182 nM. Drug effects were abolished with excess folic acid, confirming FR uptake. Inhibition of cell proliferation was reflected in binding affinities to FRα, measured by competition with [3H]folic acid. While PCFT-targeted activity was nominal, all drugs still bound to PCFT, as reflected in inhibition of [3H]methotrexate uptake at pH 5.5 and 6.8. By protection experiments with thymidine or adenosine, de novo purine biosynthesis was confirmed as the principal targeted pathway for the active analogs. While protection by 5-aminoimidazole-4-carboxamide (AICA) was complete with AGF64 (suggesting glycinamide ribonucleotide formyltransferase (GARFTase) as the primary target), for AGF50, AGF102, AGF103 and AGF132, protection was incomplete, implying a dual targeting of GARFTase and AICA ribonucleotide formyltransferase (AICARFTase). Our studies establish an important structure-activity relationship for FRα-targeted antifolates, involving modifications of the side-chain aromatic group that are well tolerated for FRα binding and transport. 6-Substituted thienoyl[2,3-d]pyrimidine analogs were all inhibitors of de novo purine biosynthesis, although relative targeting of GARFTase versus AICARFTase varied with the nature of the aromatic side-chain. Citation Format: Larry H. Matherly, Xin Zhang, Adrianne Wallace, Zhanjun Hou, Christina George, Xilin Zhou, Aleem Gangjee. Tumor-targeting with novel 6-substituted thienoyl[2,3-d]pyrimidine antifolates via cellular uptake by folate receptor α, and inhibition of de novo purine nucleotide biosynthesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4481. doi:10.1158/1538-7445.AM2015-4481

LKB1 and AMPKα1 are required in pancreatic alpha cells for the normal regulation of glucagon secretion and responses to hypoglycemia.

Glucagon release from pancreatic alpha cells is required for normal glucose homoeostasis and is dysregulated in both Type 1 and Type 2 diabetes. The tumour suppressor LKB1 (STK11) and the downstream kinase AMP-activated protein kinase (AMPK), modulate cellular metabolism and growth, and AMPK is an important target of the anti-hyperglycaemic agent metformin. While LKB1 and AMPK have emerged recently as regulators of beta cell mass and insulin secretion, the role of these enzymes in the control of glucagon production invivo is unclear. Here, we ablated LKB1 (αLKB1KO), or the catalytic alpha subunits of AMPK (αAMPKdKO, -α1KO, -α2KO), selectively in ∼45% of alpha cells in mice by deleting the corresponding flox'd alleles with a preproglucagon promoter (PPG) Cre. Blood glucose levels in male αLKB1KO mice were lower during intraperitoneal glucose, aminoimidazole carboxamide ribonucleotide (AICAR) or arginine tolerance tests, and glucose infusion rates were increased in hypoglycemic clamps (p<0.01). αLKB1KO mice also displayed impaired hypoglycemia-induced glucagon release. Glucose infusion rates were also elevated (p<0.001) in αAMPKα1 null mice, and hypoglycemia-induced plasma glucagon increases tended to be lower (p=0.06). Glucagon secretion from isolated islets was sensitized to the inhibitory action of glucose in αLKB1KO, αAMPKdKO, and -α1KO, but not -α2KO islets. An LKB1-dependent signalling cassette, involving but not restricted to AMPKα1, is required in pancreatic alpha cells for the control of glucagon release by glucose.

Synthesis and antitumor activity of a novel series of 6-substituted pyrrolo[2,3-d]pyrimidines as potential nonclassical antifolates targeting both thymidylate and purine nucleotide biosynthesis

A novel series of 2-amino-4-oxo-6-substituted pyrrolo[2,3-d]pyrimidines were designed and synthesized as potential nonclassical antifolates targeting both thymidylate and purine nucleotide biosynthesis. Condensation of 2,4-diamino-6-hydroxypyrimidine with ethyl-4-chloroacetoacetate and subsequent hydrolysis afforded the key intermediate, 2-amino-4-oxo-pyrrolo[2,3-d]pyrimidin-6-yl-acetic acid. Coupling with various amino acid methyl esters followed by saponification and condensation with 3-(aminomethyl)pyridine provided target compounds 1–9. The new compounds exhibited micromolar to submicromolar antiproliferative potencies against a panel of tumor cell lines including KB, A549 and HepG2. Growth inhibition of compound 2 toward KB cells resulted in cytotoxicity and G1/G2-phase accumulation, and was partially protected by excess thymidine and adenosine, but was completely reversed in the combination of thymidine and adenosine, indicating both thymidylate and de novo purine nucleotide synthesis as the targeted pathway. However, 5-aminoimidazole-4-carboxamide (AICA) protection was incomplete, suggesting inhibition of both glycinamide ribonucleotide formyltransferase (GARFTase) and AICA ribonucleotide formyltransferase (AICARFTase). The results of the docking studies show that 2 could bind and inhibit both thymidylate synthase (TS) and the two folate-dependent purine biosynthetic enzymes (GARFTase and AICARFTase), which is consistent with the results of in vitro metabolic assays. Our studies establish that compound 2 is an excellent lead analog as a multitargeted antifolate for further structure optimization.

Characterization of ghrelin-sensitive neurons in the lumbosacral defecation center in rats.

Ghrelin is involved in the regulation of somatic growth, feeding behavior and energy homeostasis. Ghrelin stimulates neuropeptide Y (NPY) neurons and activates intracellular AMP-activated protein kinase (AMPK) in the hypothalamus. These NPY neurons also express the leptin receptor and leptin inhibits ghrelin-induced activation of NPY neurons. In the spinal cord, we have demonstrated colokinetic action of ghrelin. However, the precise characteristics of the ghrelin-sensitive neurons remain to be clarified. The aim of this study was firstly to confirm that the action of ghrelin is mediated via a neurogenic pathway in the spinal cord, and secondly to characterize the ghrelin-sensitive neurons by comparing with hypothalamic ghrelin-sensitive neurons. Rats were anesthetised with alpha-chloralose and ketamine, and colorectal intraluminal pressure and expelled volume were recorded in vivo. Drugs were applied intrathecally. Ghrelin caused enhancement of propulsive contractions. Tetrodotoxin completely blocked the colokinetic effect of ghrelin. An AMPK activator, aminoimidazole carboxamide ribonucleotide, failed to mimic the ghrelin effect. Leptin had no effect on the spontaneous contractions and did not exert a suppressive effect on the ghrelin-enhanced colorectal motility. An NPY Y1 receptor antagonist did not affect the action of ghrelin. NPY had no effect on the colorectal motility. This study showed that intrathecal injection of ghrelin stimulates colorectal motility by acting on ghrelin-sensitive neurons in the lumbosacral defecation center. The characteristics of ghrelin-sensitive neurons in the spinal cord are quite different from those of ghrelin-sensitive neurons in the hypothalamus.

ASSA14-03-12 Protective effect and mechanism of metformin on cardiosphere-derived cells

Background Recent studies have shown that metformin activates AMP-activated protein kinase (AMPK) and has a potentcardioprotective effect against ischemia/reperfusion injury. Previous studies have focused on the protective effects of metformin on cardiomyocytes,and the mechanisms by which metforminexerts these cardioprotective effects remain unclear. our study aimed to investigate if metformin has beneficial effects on damaged cardiosphere-derived cellsby H 2 O 2 , and reveal the potential mechanism of action of cardioprotective effect of metformin. Methods And Result Cardiosphere-derived cells were cultured from the ventricles of one-day-old Sprague Dawley rats, and these cells were incubated in the presence of 50 µmol/l H 2 O 2 for 24 h. Cardiosphere-derived cellswere pretreated with metformin at different concentrations and time and with aminoimidazole carboxamide ribonucleotide (AICAR) (400 µmol/l), an adenosine monophophate (AMP)-activated protein kinase (AMPK) agonist for 60 min before the addition of H 2 O 2 . Other cells were preincubated with compound C (an AMPK antagonist, 20 μmol/l) for 4 h. The viability and apoptosis of cells were analysed by CCK8,flowcytometry,and TUNEl. AMPK and endothelial nitric oxide synthase (eNOS) were analysed using immunblotting. Metformin had antagonistic effects on the influences of H 2 O 2 on cell viability and attenuated oxidative stress-induced apoptosis. Metformin also increased phosphorylation of AMPK and eNOS. Conclusions Metformin attenuated oxidative stress–induced cardiosphere-derived cells apoptosis, The protectiveeffects of metformin were associated withactivation of the AMPK-eNOS pathway.

(4-[6-(4-isopropoxyphenyl)pyrazolo [1,5-a]pyrimidin-3-yl] quinoline) is a novel inhibitor of autophagy.

Autophagy is an important intracellular degradation system, which is related to various diseases. In preliminary experiments we found that D4-[6-(4-isopropoxyphenyl)pyrazolo [1,5-a]pyrimidin-3-yl] quinoline (DMH1) inhibited autophagy responses. However DMH1 also inhibits the signalling pathway activated by bone morphogenetic protein-4 (BMP4). The aim of the present study was to elucidate the inhibitory effects of DMH1 on autophagy and the underlying mechanisms. The effects of DMH1 on autophagy responses were evaluated in cultures of different cell types and with different stimuli to induce autophagy, using Western blots, transmission electron microscopy and fluorescent microscopy. DMH1 inhibited starvation-induced autophagy in cardiomyocytes, HeLa and MCF-7 cells, without involving the signalling pathway of BMP4. DMH1 inhibited aminoimidazole carboxamide ribonucleotide (AICAR)- and rapamycin-induced autophagy in HeLa and MCF-7 cells. DMH1 reversed starvation- and AICAR-induced inhibition of Akt, mammalian target of rapamycin (mTOR) and p70S6 kinase (S6K), and reversed rapamycin-induced inhibition of mTOR and S6K. DMH1 reversed starvation-induced decrease of the phosphorylated form of glycogen synthase kinase-3 in MCF-7 and HT29 cells. Activation of Akt and inhibition of autophagy induced by DMH1 were antagonized by an Akt specific inhibitor or by small interfering RNA for Akt in HeLa cells. DMH1 inhibited cellular autophagy responses in a range of cell types and the underlying mechanisms include activation of the Akt pathway.

MicroRNA modulation induced by AICA ribonucleotide in J1 mouse ES cells.

ES cells can propagate indefinitely, maintain self-renewal, and differentiate into almost any cell type of the body. These properties make them valuable in the research of embryonic development, regenerative medicine, and organ transplantation. MicroRNAs (miRNAs) are considered to have essential functions in the maintenance and differentiation of embryonic stem cells (ES cells). It was reported that, strong external stimuli, such as a transient low-pH and hypoxia stress, were conducive to the formation of induced pluripotent stem cells (iPS cells). AICA ribonucleotide (AICAR) is an AMP-activated protein kinase activator, which can let cells in the state of energy stress. We have demonstrated that AICAR can maintain the pluripotency of J1 mouse ES cells through modulating protein expression in our previous research, but its effects on ES cell miRNA expression remain unknown. In this study, we conducted small RNA high-throughput sequencing to investigate AICAR influence on J1 mouse ES cells by comparing the miRNA expression patterns of the AICAR-treated cells and those without treatment. The result showed that AICAR can significantly modulate the expression of multiple miRNAs, including those have crucial functions in ES cell development. Some differentially expressed miRNAs were selected and confirmed by real-time PCR. For the differently expressed miRNAs identified, further study was conducted regarding the pluripotency and differentiation associated miRNAs with their targets. Moreover, miR-134 was significantly down-regulated after AICAR treatment, and this was suggested to be directly associated with the up-regulated pluripotency markers, Nanog and Sox2. Lastly, Myc was significantly down-regulated after AICAR treatment; therefore, we predicted miRNAs that may target Myc and identified that AICAR induced up-regulation of miR-34a, 34b, and 34c can repress Myc expression in J1 mouse ES cells. Taken together, our study provide a new mechanism for AICAR in ES cells pluripotency maintenance and give insight for its usage in iPS cells generation.

Uveal melanoma cell growth is inhibited by aminoimidazole carboxamide ribonucleotide (AICAR) partially through activation of AMP-dependent kinase.

To evaluate the effects and mechanism of aminoimidazole carboxamide ribonucleotide (AICAR), an AMP-dependent kinase (AMPK) activator, on the growth of uveal melanoma cell lines. Four different cell lines were treated with AICAR (1-4 mM). Cell growth was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. Cell cycle analysis was conducted by flow cytometry; additionally, expression of cell-cycle control proteins, cell growth transcription factors, and downstream effectors of AMPK were determined by RT-PCR and Western blot. Aminoimidazole carboxamide ribonucleotide inhibited cell growth, induced S-phase arrest, and led to AMPK activation. Aminoimidazole carboxamide ribonucleotide treatment was associated with inhibition of eukaryotic translation initiation factor 4E-BP1 phosphorylation, a marker of mammalian target of rapamycin (mTOR) pathway activity. Aminoimidazole carboxamide ribonucleotide treatment was also associated with downregulation of cyclins A and D, but had minimal effects on the phosphorylation of ribosomal protein S6 or levels of the macroautophagy marker LC3B. The effects of AICAR were abolished by treatment with dipyridamole, an adenosine transporter inhibitor that blocks the entry of AICAR into cells. Treatment with adenosine kinase inhibitor 5-iodotubericidin, which inhibits the conversion of AICAR to its 5'-phosphorylated ribotide 5-aminoimidazole-4-carboxamide-1-D-ribofuranosyl-5'-monophosphate (ZMP; the direct activator of AMPK), reversed most of the growth-inhibitory effects, indicating that some of AICAR's antiproliferative effects are mediated at least partially through AMPK activation. Aminoimidazole carboxamide ribonucleotide inhibited uveal melanoma cell proliferation partially through activation of the AMPK pathway and downregulation of cyclins A1 and D1.

Discovery of 5-Substituted Pyrrolo[2,3-d]pyrimidine Antifolates as Dual-Acting Inhibitors of Glycinamide Ribonucleotide Formyltransferase and 5-Aminoimidazole-4-carboxamide Ribonucleotide Formyltransferase in De Novo Purine Nucleotide Biosynthesis: Implications of Inhibiting 5-Aminoimidazole-4-carboxamide Ribonucleotide Formyltransferase to AMPK Activation and Antitumor Activity

We synthesized 5-substituted pyrrolo[2,3-d]pyrimidine antifolates (compounds 5-10) with one-to-six bridge carbons and a benozyl ring in the side chain as antitumor agents. Compound 8 with a 4-carbon bridge was the most active analogue and potently inhibited proliferation of folate receptor (FR) α-expressing Chinese hamster ovary and KB human tumor cells. Growth inhibition was reversed completely or in part by excess folic acid, indicating that FRα is involved in cellular uptake, and resulted in S-phase accumulation and apoptosis. Antiproliferative effects of compound 8 toward KB cells were protected by excess adenosine but not thymidine, establishing de novo purine nucleotide biosynthesis as the targeted pathway. However, 5-aminoimidazole-4-carboxamide (AICA) protection was incomplete, suggesting inhibition of both AICA ribonucleotide formyltransferase (AICARFTase) and glycinamide ribonucleotide formyltransferase (GARFTase). Inhibition of GARFTase and AICARFTase by compound 8 was confirmed by cellular metabolic assays and resulted in ATP pool depletion. To our knowledge, this is the first example of an antifolate that acts as a dual inhibitor of GARFTase and AICARFTase as its principal mechanism of action.