--------ATIC promotes pulmonary arterial smooth muscle cell proliferation via the Ras signaling pathway.

Pulmonary arterial hypertension (PAH) is a debilitating vascular disorder characterized by abnormal pulmonary artery smooth muscle cell (PASMC) proliferation and collagen synthesis, contributing to vascular remodeling and elevated pulmonary vascular resistance. This study investigated the critical role of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC) in cell proliferation and collagen synthesis in PASMCs in PAH. Here we show that ATIC levels are significantly increased in the lungs of MCT-induced PAH rat model and hypoxia-induced PAH mouse model and PDGF-stimulated PASMCs. Inhibition of ATIC attenuated platelet-derived growth factor (PDGF)-induced cell proliferation and collagen I synthesis in PASMCs. Conversely, overexpression or knockdown of ATIC causes a significant promotion or inhibition of Ras and ERK activation, cell proliferation and collagen synthesis in PASMCs. Moreover, ATIC deficiency attenuated Ras activation in the lungs of hypoxia-induced PAH mice. Further, Ras inhibition attenuates ATIC overexpression- and PDGF-induced collagen synthesis and PASMC proliferation. Notably, we identified that transcription factor MYC, EGR1, and SP1 directly binds to promoters of Atic gene and regulate ATIC expression. These results provide the first evidence that ATIC promotes PASMC proliferation in pulmonary vascular remodeling through the Ras signaling pathway.

LncRNA ZFAS1 regulates ATIC transcription and promotes the proliferation and migration of hepatocellular carcinoma through the PI3K/AKT signaling pathway.

PURPOSE: Long noncoding RNAs (lncRNAs) exert a significant influence on various cancer-related processes through their intricate interactions with RNAs. Among these, lncRNA ZFAS1 has been implicated in oncogenic roles in multiple cancer types. Nevertheless, the intricate biological significance and underlying mechanism of ZFAS1 in the initiation and progression of hepatocellular carcinoma (HCC) remain largely unexplored. METHODS: Analysis of The Cancer Genome Atlas Program (TCGA) database revealed a notable upregulation of lncRNA ZFAS1 in HCC tissues. To explore its function, we investigated colony formation and performed CCK-8 assays to gauge cellular proliferation and wound healing, Transwell assays to assess cellular migration, and an in vivo study employing a nude mouse model to scrutinize tumor growth and metastasis. Luciferase reporter assay was used to confirm the implicated interactions. Rescue experiments were conducted to unravel the plausible mechanism underlying the activation of the PI3K/AKT pathway by lncRNAs ZFAS1 and ATIC. RESULTS: ZFAS1 and ATIC were significantly upregulated in the HCC tissues and cells. ZFAS1 knockdown inhibited cell proliferation and migration. We observed a direct interaction between the lncRNA ZFAS1 and ATIC. ATIC knockdown also suppressed cell proliferation and migration. SC79, an activator of AKT, partially restores the effects of lncRNA ZFAS1/ATIC knockdown on cell proliferation and migration. Knockdown of lncRNA ZFAS1/ATIC inhibited tumor growth and lung metastasis in vivo. CONCLUSION: Overall, lncRNA ZFAS1 regulates ATIC transcription and contributes to the growth and migration of HCC cells through the PI3K/AKT signaling pathway.

Characterization of AICAR transformylase/IMP cyclohydrolase (ATIC) bifunctional enzyme from Candidatus Liberibacer asiaticus.

The bifunctional enzyme, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase/inosine monophosphate (IMP) cyclohydrolase (ATIC) is involved in catalyzing penultimate and final steps of purine de novo biosynthetic pathway crucial for the survival of organisms. The present study reports the characterization of ATIC from Candidatus Liberibacer asiaticus (CLasATIC) along with the identification of potential inhibitor molecules and evaluation of cell proliferative activity. CLasATIC showed both the AICAR Transformylase (AICAR TFase) activity for substrates, 10-f-THF (Km, 146.6 µM and Vmax, 0.95 µmol/min/mg) and AICAR (Km, 34.81 µM and Vmax, 0.56 µmol/min/mg) and IMP cyclohydrolase (IMPCHase) activitiy (Km, 1.81 µM and Vmax, 2.87 µmol/min/mg). The optimum pH and temperature were also identified for the enzyme activity. In-silico study has been conducted to identify potential inhibitor molecules through virtual screening and MD simulations. Out of many compounds, HNBSA, diosbulbin A and lepidine D emerged as lead compounds, exhibiting higher binding energy and stability for CLasATIC than AICAR. ITC study reports higher binding affinities for HNBSA and diosbulbin A (Kd, 12.3 µM and 34.2 µM, respectively) compared to AICAR (Kd, 83.4 µM). Likewise, DSC studies showed enhanced thermal stability for CLasATIC in the presence of inhibitors. CD and Fluorescence studies revealed significant conformational changes in CLasATIC upon binding of the inhibitors. CLasATIC demonstrated potent cell proliferative, wound healing and ROS scavenging properties evaluated by cell-based bioassays using CHO cells. This study highlights CLasATIC as a promising drug target with potential inhibitors for managing CLas and its unique cell protective, wound-healing properties for future biotechnological applications.

Anaplastic large cell lymphoma with ALK::ATIC fusion mimicking a histiocytic sarcoma debuting as an anterior thoracic soft tissue tumor with exceptional clinicopathological, morphological and molecular features.

A 56-year-old woman debuted with a palpable painless mass in the anterior thorax wall at the level of the second and third right parasternal intercostal space, which progressively increased in size over 5 months accompanied by localized skin rash, mild dyspnea and chest pain when changing position. Imaging studies showed a soft tissue mass measuring 75 × 62 mm and a density of 34 Hounsfield Units that had caused the lysis of the costal arches and grew expansively towards the anterior mediastinum, without identifying mediastinal adenopathies only by this imaging method. Core biopsy was performed, which was initially diagnosed as histiocytic sarcoma (HS); however, when the diagnostic panel was expanded to include molecular and NGS studies, the final diagnosis was anaplastic large cell lymphoma with ALK::ATIC fusion. Here, we report a very rare neoplasm with unusual clinical presentation, histopathology and molecular features.

The impact of folate pathway variants on the outcome of methotrexate therapy in rheumatoid arthritis patients.

BACKGROUND: There are currently no validated criteria that entirely explain or predict response to methotrexate (MTX) treatment in rheumatoid arthritis (RA). We tried to identify the connection between three variants (RFC1 G80A (rs1051266), TYMS 2R/3R (rs34743033), and ATIC C347G (rs2372536)) in the folate pathway of MTX metabolism and the response to MTX monotherapy in a cohort of RA cases. METHODS: A prospective study on 100 RA patients on MTX monotherapy was performed. Disease activity was measured at the start of treatment and 6 months after treatment with MTX. The patients were then split into two groups: those who responded to the treatment and those who did not. The molecular genetic study for the RFC1 (G80A) variant was employed via the PCR-restriction fragment length polymorphism (PCR-RFLP) technique, the ATIC (C347G) variant was performed using TaqMan allelic discrimination real-time PCR, and the tandem repeat sequences of TYMS (2R/3R) were amplified by conventional PCR and detected by agarose gel electrophoresis. RESULTS: The genotype distribution of RFC-1 (G80A) showed significant variations among non-responders and responders in the recessive genetic model. A significant difference was found in TYMS (2R/3R) in the dominant and heterozygous genetic models. However, ATIC (C347G) genotype frequency did not exhibit substantial link with drug response in all genetic models. Furthermore, the genotype and allele rates of the analyzed variants did not show any significant association with adverse events in all genetic models. CONCLUSION: The 80AA genotype of RFC-1 G80A and the 2R/3R or 3R/3R genotypes of TYMS 2R/3R are more vulnerable to the good consequences of MTX therapy. Key Points • Current recommendations support the gold standard role of MTX as a first-line monotherapy for RA patients. However, up to 40% of RA patients do not respond or exhibit partial response to MTX. • Persistent disease activity due to treatment unresponsiveness will affect the long-term outcomes in RA patients. • We aimed, through molecular genetic study, to identify the connection between three variants in the folate pathway of MTX metabolism and the response to methotrexate monotherapy in a cohort of RA patients.

Targeting LRRK2 mRNA stability in Parkinson's disease.

In a recent study, Liu and colleagues demonstrated a role for the purine biosynthesis enzyme ATIC and its substrate in regulating the protein levels of the Parkinson's disease kinase LRRK2, which rescues neurodegeneration and neuroinflammation in distinct animal models. This work highlights a novel avenue to target LRRK2 protein levels as a strategy to prevent neurodegeneration in Parkinson's disease.

MicroRNA-145-5p suppresses cell proliferation, migration, and invasion in upper tract urothelial carcinoma by targeting 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase.

Upper tract urothelial carcinoma (UTUC), including renal, pelvic, and ureteral carcinoma, has a high incidence rate in Taiwan, which is different from that in Western countries. Therefore, it is imperative to elucidate the mechanisms underlying UTUC growth and metastasis. To explore the function of miR-145-5p in UTUC, we transfected the BFTC909 cell line with miR-145-5p mimics and analyzed the differences in protein levels by performing two-dimensional polyacrylamide gel electrophoresis. Real-time polymerase chain reaction and Western blot analysis were used to analyze 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inositol monophosphate cyclohydrolase (ATIC) messenger RNA and protein levels. A dual-luciferase assay was performed to identify the target of miR-145-5p in ATIC. The effects of miR-145-5p and ATIC expression by cell transfection on cell proliferation, migration, and invasion were also assessed. miR-145-5p downregulated ATIC protein expression. High ATIC expression is associated with tumor stage, metastasis, recurrence, and a poor prognosis in patients with UTUC. Cell function assays revealed that ATIC knockdown inhibited the proliferation, migration, and invasive abilities of UTUC cells. In contrast, miR-145-5p affected the proliferation, migration, and invasive abilities of UTUC cells by directly targeting the 3'-untranslated regions of ATIC. Furthermore, we used RNA sequencing and Ingenuity Pathway Analysis to identify possible downstream genes regulated by ATIC and found that miR-145-5p regulated the protein levels of fibronectin 1, Slug, cyclin A2, cyclin B1, P57, and interferon-induced transmembrane 1 via ATIC. ATIC may be a valuable predictor of prognosis and a potential therapeutic target for UTUC.

Circ_0058063 regulates cell vitality and proliferation in oesophageal squamous-cell carcinomas.

Oesophageal squamous-cell carcinoma (ESCC) is a malignant tumor of the digestive system with a poor prognosis. Recent studies have shown the promoting effect of hsa_circ_0058063 (circ_0058063) on ESCC, but the potential regulatory mechanisms of circ_0058063 in ESCC remain largely unclear. The levels of circ_0058063, microRNA-4319 (miR-4319) and mRNA of thrombospondin-1 (THBS1) were indicated by quantitative real-time polymerase chain reaction in ESCC tissues and cells. Meanwhile, the level of THBS1 was quantified by western blot analysis. In addition, the cell functions were examined by CCK8 assay, Edu assay, flow cytometry assay and transwell assay. Furthermore, the interplay between miR-4319 and circ_0058063 or THBS1 was detected by dual-luciferase reporter assay. Finally, an in vivo experiment was implemented to confirm the effect of circ_0058063. The level of circ_0058063 and THBS1 were increased, and the miR-4319 level was decreased in ESCC tissues in contrast to that in normal tissues and cells. For functional analysis, circ_0058063 deficiency inhibited cell vitality, cell proliferation, migration and invasion in ESCC cells, whereas promoted cell apoptosis. Moreover, miR-4319 was confirmed to repress the progression of ESCC cells by suppressing THBS1. In mechanism, circ_0058063 acted as a miR-4319 sponge to regulate the level of THBS1. Besides, circ_0058063 knockdown also attenuated tumour growth in vivo. Circ_0058063 facilitates the development of ESCC through increasing THBS1 expression by regulating miR-4319, which also offered an underlying targeted therapy for ESCC treatment.

Active topological defect absorption by a curvature singularity.

We leverage the Born-Oppenheimer approximation to present a general description of topological defects dynamics inp-atic materials on curved surfaces. Focusing on the case of an active nematic, we find that activity induces a geometric contribution to the motility of the+1/2defect. Moreover, in the case of a cone, the simplest example of a geometry with curvature singularity, we find that the motility depends on the deficit angle of the cone and changes sign when the deficit angle is greater thanπ, leading to the change in active behavior from contractile (extensile) to extensile (contractile) behavior. Using our analytical framework, we then identify for positively charged defects the basin of attraction to the cone apex and present closed-form predictions for defect trajectories near the apex. The analytical results are quantitatively corroborated against full numerical simulations, with excellent agreement when the capture radius is small compared to the cone size.

Purine synthesis suppression reduces the development and progression of pulmonary hypertension in rodent models.

AIMS: Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of pulmonary hypertension (PH). Proliferative cells utilize purine bases from the de novo purine synthesis (DNPS) pathways for nucleotide synthesis; however, it is unclear whether DNPS plays a critical role in VSMC proliferation during development of PH. The last two steps of DNPS are catalysed by the enzyme 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC). This study investigated whether ATIC-driven DNPS affects the proliferation of pulmonary artery smooth muscle cells (PASMCs) and the development of PH. METHODS AND RESULTS: Metabolites of DNPS in proliferative PASMCs were measured by liquid chromatography-tandem mass spectrometry. ATIC expression was assessed in platelet-derived growth factor-treated PASMCs and in the lungs of PH rodents and patients with pulmonary arterial hypertension. Mice with global and VSMC-specific knockout of Atic were utilized to investigate the role of ATIC in both hypoxia- and lung interleukin-6/hypoxia-induced murine PH. ATIC-mediated DNPS at the mRNA, protein, and enzymatic activity levels were increased in platelet-derived growth factor-treated PASMCs or PASMCs from PH rodents and patients with pulmonary arterial hypertension. In cultured PASMCs, ATIC knockdown decreased DNPS and nucleic acid DNA/RNA synthesis, and reduced cell proliferation. Global or VSMC-specific knockout of Atic attenuated vascular remodelling and inhibited the development and progression of both hypoxia- and lung IL-6/hypoxia-induced PH in mice. CONCLUSION: Targeting ATIC-mediated DNPS compromises the availability of purine nucleotides for incorporation into DNA/RNA, reducing PASMC proliferation and pulmonary vascular remodelling and ameliorating the development and progression of PH.

Circ-ATIC regulates esophageal squamous cell carcinoma growth and metastasis through miR-1294/PBX3 pathway.

Esophageal squamous cell carcinoma (ESCC) is a digestive tract malignancy associated with poor clinical outcome. Growing evidence have elucidated that circular RNAs (circRNAs) play important roles in the pathological process of ESCC. However, the detailed mechanisms how circRNAs modulate the development of ESCC remain largely unknown. Our study aimed to decipher the role and mechanism of circ-ATIC (also termed as circRNA_0058063) in regulating the progression of ESCC. We found that circ-ATIC and its host gene ATIC were significantly increased in ESCC tissues and cells compared with the adjacent noncancerous tissues or normal esophagus epithelial cell. Circ-ATIC knockdown substantially reduced proliferation and the number of invaded ESCC cells and retarded EMT process, reflecting by the decreased N-cadherin and elevated E-cadherin. However, the level of host gene ATIC was not changed under circ-ATIC suppression. It was predicted that circ-ATIC could bind to miR-1294 and serve as a sponge RNA. The luciferase reporter assay and RNA immunoprecipitation (RIP) assay confirmed their relations. MiR-1294 was decreased in ESCC tissues and cells, which was reversely correlated with circ-ATIC level. Furthermore, PBX3 was predicted and proved to be a downstream direct target of miR-1294. PBX3 mRNA and protein were obviously upregulated in ESCC tumor tissues and cells. PBX3 overexpression could reverse the suppressive roles of miR-1294 mimics on ESCC proliferation and invasion. In an xenograft nude mice model, stable transfection of sh-circ-ATIC significantly retarded the growth of tumor and suppressed VEGF and Ki67. Collectively, circ-ATIC promoted ESCC proliferation and invasion by regulating miR-1294/PBX3 axis.

Promoter methylation levels of RASSF1 and ATIC genes are associated with lung cancer in Iranian patients.

OBJECTIVES: Epigenetic alterations like methylation of tumor suppressor genes or oncogenes, in respiratory epithelium have been associated with lung cancer. Hypermethylation of genes promoter is an epigenetic event, and is responsible to tumor suppressor genes inactivation as well as oncogenes activation. This study aimed to assess the role of methylation status in promoter of RASSF1 and ATIC genes their potential implication in the pathogenesis of lung tumor in Iranian patients. METHODS: In this study, we collected 100 tissue samples (50 lung cancer tissues and 50 adjacent non-cancerous lung tissues) from Iranian lung cancer patients. The genomic DNA was extracted, and methylation status of both RASSF1 and ATIC genes was investigated by methylation-sensitive high-resolution melting (MS-HRM) assay technique and Real-Time PCR. Cancer Genome Atlas (TCGA) dataset was also analyzed for further validation of the gene's methylation. RESULTS: Methylation of RASSF1 gene promoter was significantly higher in lung tumor tissues. However, promoter methylation levels of ATIC gene was significantly lower in lung tumor tissues. These results were additionally confirmed by TCGA analysis. Promoter methylation of both RASSF1 and ATIC genes was significantly associated with lymph node metastasis, and clinical stage of lung cancer. The receiver operating characteristic (ROC) curve analysis indicated a high accuracy of promoter methylation in these genes as a diagnostic biomarker for lung cancer. CONCLUSIONS: Methylation levels of both RASSF1 and ATIC genes promoters were associated with lung cancer pathogenesis in Iranian population, and may be a suitable biomarker for diagnosis and prognosis of lung cancer in early stage of tumorigenesis.

Expanding the spectrum of clinical severity of AICA-ribosiduria: Report of two siblings with mild phenotype caused by a novel pathogenic variant in ATIC gene.

5-Amino-4-imidazolecarboxamide-ribosiduria (AICA-ribosiduria) is an extremely rare inborn error of purine biosynthesis metabolism caused by pathogenic variants in ATIC gene that encodes a protein catalyzing the last steps of the de novo purine biosynthesis. To date, only six cases have been reported presenting a severe phenotype characterized by coarse facies and variable dysmorphic features, intrauterine and postnatal growth retardation, severe and early neurodevelopment delay, profound congenital visual deficit, scoliosis and, less frequently, epilepsy, aortic coarctation, chronic hepatic cytolysis, nephrocalcinosis and mild genitalia malformation. In this article, we report two new cases of AICA-ribosiduria carrying new pathogenic variants in ATIC (c.421C>T;p.Arg141Ter and c.1753A>G p.Thr585Ala) associated to a milder phenotype compared to previously reported patients. Particularly, the children showed few dysmorphic features (bulging forehead, depressed nasal bridge, and flat nasal tip), postnatal growth impairment, psychomotor delay since the second year of life, reduction of visual acuity (from mild impairment to low vision from the age of 5 years and to partial blindness from the age of 7 years) and mild hepatic dysfunctions. Scoliosis as well as epilepsy, renal involvement, or genitalia malformation were not detected. According to literature data, we found an abnormal accumulation of intermediates of de novo purine biosynthesis in the urine of both siblings. This report expands the spectrum of phenotypic severity associated to ATIC biallelic pathogenic variants and prompts the need to investigate ultra-rare causes of metabolic disorders such as AICA-ribosiduria in subjects with early neurological and sensory involvement of uncertain etiology.

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.

ATIC-Associated De Novo Purine Synthesis Is Critically Involved in Proliferative Arterial Disease.

BACKGROUND: Proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of arterial diseases, especially in arterial restenosis after angioplasty or stent placement. VSMCs reprogram their metabolism to meet the increased requirements of lipids, proteins, and nucleotides for their proliferation. De novo purine synthesis is one of critical pathways for nucleotide synthesis. However, its role in proliferation of VSMCs in these arterial diseases has not been defined. METHODS: De novo purine synthesis in proliferative VSMCs was evaluated by liquid chromatography-tandem mass spectrometry. The expression of ATIC (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase), the critical bifunctional enzyme in the last 2 steps of the de novo purine synthesis pathway, was assessed in VSMCs of proliferative arterial neointima. Global and VSMC-specific knockout of Atic mice were generated and used for examining the role of ATIC-associated purine metabolism in the formation of arterial neointima and atherosclerotic lesions. RESULTS: In this study, we found that de novo purine synthesis was increased in proliferative VSMCs. Upregulated purine synthesis genes, including ATIC, were observed in the neointima of the injured vessels and atherosclerotic lesions both in mice and humans. Global or specific knockout of Atic in VSMCs inhibited cell proliferation, attenuating the arterial neointima in models of mouse atherosclerosis and arterial restenosis. CONCLUSIONS: These results reveal that de novo purine synthesis plays an important role in VSMC proliferation in arterial disease. These findings suggest that targeting ATIC is a promising therapeutic approach to combat arterial diseases.

Pharmacogenomics of Methotrexate Pathway in Rheumatoid Arthritis Patients: Approach toward Personalized Medicine.

Background: Methotrexate (MTX) is one of the most common medications used for rheumatoid arthritis (RA) treatment. Single-nucleotide polymorphisms (SNPs) could potentially predict variability in therapeutic outcomes. Aim: This study aims to assess the impact of SNPs in genes encoding for the MTX pathway for predicting clinical and therapeutic responses to MTX in a cohort of Egyptian patients with RA. Subjects and Methods: Data from 107 Egyptian RA patients (aged 44.4 ± 11.4 years) treated with MTX monotherapy, for a duration of 3.7 ± 3.3 years, were collected. Genotypes of 10 SNPs from four different genes were analyzed using the allelic discrimination PCR technique. Results: The ATIC rs3821353 G/T (p = 0.034) and the C/T and C/C of SLC19A1 rs7279445 (p = 0.0018) were associated with a non-response to MTX, while DHFR rs10072026 C/T and C/C were associated with a good response (p < 0.001). Carriers of the ATIC rs382135 3 G (p = 0.001) and ATIC rs4673990 G (p < 0.001) alleles were more likely to develop RA, while the SLC19A1 rs11702425 T (p < 0.001) and GGH rs12681874 T (p = 0.003) allele carriers were more likely to be protected against RA. Carriers of the ATIC rs4673990 A/G genotype (p < 0.001) were at risk of developing RA, while carriers of the following genotypes were mostly protected against RA: ATIC rs3821353 T/T (p < 0.001), ATIC rs3821353 G/G (p = 0.004), SLC19A1 rs11702425 T/T (p = 0.001), SLC19A1 rs11702425 C/T (p = 0.003), GGH rs12681874 C/T (p = 0.004) and GGH rs12681874 T/T (0.002). Conclusion: The genotyping of genes involved in the MTX pathway may be helpful to predict which RA patients will/will not benefit from MTX, and thus, may help to apply a personalized medicine approach in RA.

Case report of a rare purine synthesis disorder due to 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase (AICAR) deficiency.

BACKGROUND: AICA (5-aminoimidazole-4-carboxamide) ribosiduria is an inborn error in purine biosynthesis caused due to biallelic pathogenic variants in the 5-aminoimidazole-4-carboxamide ribonucleotide-formyltransferase/imp cyclohydrolase (ATIC) gene located on chromosome 2q35. ATIC codes for a bifunctional enzyme, AICAR transformylase and inosine monophosphate (IMP) cyclohydrolase, which catalyse the last two steps of de novo purine synthesis. This disorder has been previously reported in only 4 cases worldwide, and herein, we report the first from India. CASE REPORT: The proband presented with global developmental delay, developmental hip dysplasia (DDH), acyanotic heart disease and nystagmoid eye movements. Whole exome sequencing (WES) identified compound heterozygous pathogenic variants in the ATIC. A novel splice site variant; c.1321-2A > G and a previously reported missense variant; c.1277A > G (p.Lys426Arg) were identified. Segregation analysis of parents showed the father to be a heterozygous carrier for the splice site variant and the mother, a heterozygous carrier for the missense variant. CONCLUSION: This case of a rare genetic disorder of purine biosynthesis of ATIC deficiency is the first case reported from India. Early diagnosis lead to early interventional therapy and genetic counselling.

5-Amino-4-Imidazolecarboxamide Ribonucleotide Transformylase/IMP Cyclohydrolase Polymorphisms Affect the Susceptibility to Multiple Myeloma.

OBJECTIVE: The upregulation of 5-amino-4-imidazolecarboxamide ribonucleotide transformylase/IMP cyclohydrolase (ATIC) may affect tumorigenesis and multiple myeloma (MM) development. MATERIALS AND METHODS: A total of 97 patients with MM and 102 healthy control patients were included in the study. The SNaPshot technique was used to detect the ATIC gene polymorphisms. Linkage disequilibrium (LD) and haplotype analyses were conducted using SHEsis software. RESULTS: The genotype distribution or allele frequency of rs3772078 and rs16853834 was significantly different between the patients with MM and the healthy control patients (all P < .05). The rs16853834 A allele, rs3772078 CT genotype, and C allele were associated with a decreased risk of MM (all P < .05). Five single-nucleotide polymorphism combinations showed strong LD. Three haplotypes were associated with MM risk (all P < .05). We found that ATIC rs7604984 was significantly associated with serum lactate dehydrogenase levels (P = .050). CONCLUSION: We determined that the rs3772078 and rs16853834 polymorphisms are associated with a decreased risk of MM.

Impact of Variants in the ATIC and ARID5B Genes on Therapeutic Failure with Imatinib in Patients with Chronic Myeloid Leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm derived from the balanced reciprocal translocation of chromosomes 9 and 22 t (9q34 and 22q11), which leads to the formation of the Philadelphia chromosome and fusion of the BCR-ABL genes. The first-line treatment for CML is imatinib, a tyrosine kinase inhibitor that acts on the BCR-ABL protein. However, even though it is a target-specific drug, about 25% of patients do not respond to this treatment. The resistance mechanisms involved in this process have been investigated and studies have shown that germinal alterations can influence this mechanism. The aim of this work was to investigate 32 polymorphisms in 24 genes of carcinogenic pathway to verify the influence of these genetic variants on the response to treatment with imatinib. Our results demonstrated that individuals with the recessive GG genotype for the rs2372536 variant in the ATIC gene are approximately three times more likely to experience treatment failure with imatinib (p = 0.045, HR = 2.726, 95% CI = 0.9986-7.441), as well as individuals with the TT genotype for the rs10821936 variant in the ARID5B gene, who also have a higher risk for treatment failure with imatinib over time (p = 0.02, HR = 0.4053, IC 95% = 0.1802-0.911). In conclusion, we show that variants in the ATIC and ARIDB5 gene, never screened in previous studies, could potentially influence the therapeutic response to imatinib in patients treated for CML.

Disorders of purine biosynthesis metabolism.

Purines are essential molecules that are components of vital biomolecules, such as nucleic acids, coenzymes, signaling molecules, as well as energy transfer molecules. The de novo biosynthesis pathway starts from phosphoribosylpyrophosphate (PRPP) and eventually leads to the synthesis of inosine monophosphate (IMP) by means of 10 sequential steps catalyzed by six different enzymes, three of which are bi-or tri-functional in nature. IMP is then converted into guanosine monophosphate (GMP) or adenosine monophosphate (AMP), which are further phosphorylated into nucleoside di- or tri-phosphates, such as GDP, GTP, ADP and ATP. This review provides an overview of inborn errors of metabolism pertaining to purine synthesis in humans, including either phosphoribosylpyrophosphate synthetase (PRS) overactivity or deficiency, as well as adenylosuccinate lyase (ADSL), 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC), phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS), and adenylosuccinate synthetase (ADSS) deficiencies. ITPase deficiency is being described as well. The clinical spectrum of these disorders is broad, including neurological impairment, such as psychomotor retardation, epilepsy, hypotonia, or microcephaly; sensory involvement, such as deafness and visual disturbances; multiple malformations, as well as muscle presentations or consequences of hyperuricemia, such as gouty arthritis or kidney stones. Clinical signs are often nonspecific and, thus, overlooked. It is to be hoped that this is likely to be gradually overcome by using sensitive biochemical investigations and next-generation sequencing technologies.