Lysosomal dysfunction and overload of nucleosides in thymidine phosphorylase deficiency of MNGIE.

Inherited deficiency of thymidine phosphorylase (TP), encoded by TYMP, leads to a rare disease with multiple mitochondrial DNA (mtDNA) abnormalities, mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). However, the impact of TP deficiency on lysosomes remains unclear, which are important for mitochondrial quality control and nucleic acid metabolism. Muscle biopsy tissue and skin fibroblasts from MNGIE patients, patients with m.3243 A > G mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and healthy controls (HC) were collected to perform mitochondrial and lysosomal functional analyses. In addition to mtDNA abnormalities, compared to controls distinctively reduced expression of LAMP1 and increased mitochondrial content were detected in the muscle tissue of MNGIE patients. Skin fibroblasts from MNGIE patients showed decreased expression of LAMP2, lowered lysosomal acidity, reduced enzyme activity and impaired protein degradation ability. TYMP knockout or TP inhibition in cells can also induce the similar lysosomal dysfunction. Using lysosome immunoprecipitation (Lyso- IP), increased mitochondrial proteins, decreased vesicular proteins and V-ATPase enzymes, and accumulation of various nucleosides were detected in lysosomes with TP deficiency. Treatment of cells with high concentrations of dThd and dUrd also triggers lysosomal dysfunction and disruption of mitochondrial homeostasis. Therefore, the results provided evidence that TP deficiency leads to nucleoside accumulation in lysosomes and lysosomal dysfunction, revealing the widespread disruption of organelles underlying MNGIE.

Ocular manifestations of mitochondrial neurogastrointestinal encephalomyopathy: A case report and literature review.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive multisystem disorder that often presents with gastrointestinal and neurological symptoms. Here we report a 33-year-old male who presented with a 16-year history of diarrhea with black stool and progressive weight loss. He complained of progressive bilateral blurred vision, upper eyelids heaviness, ocular motility impairment, and color blindness. Peripheral neuropathy, bilateral sensorineural deafness, hyperlactatemia, diabetes mellitus, hepatic steatosis, blood coagulation dysfunction, and diffuse leukoencephalopathy were detected in the systemic evaluation. Based on the novel homozygous pathogenic variant in the TYMP gene (c.1159+1G>A), he was diagnosed with MNGIE. On ophthalmic examinations, the thickness of the inner retina and ganglion cell complex significantly decreased. ERG showed diffusely decreased amplitudes. The electronegative electroretinogram, which was first reported in MNGIE, indicated a more severe inner retina impairment. The bilateral papillomacular bundle defect and central vision loss in MNGIE are consistent with classical mitochondrial optic neuropathies' features. According to the literature, pigmentary retinopathy, optic neuropathy, and abnormal pupillary reflexes are uncommon ocular features of MNGIE. This study contributes to a better understanding of ocular manifestations in MNGIE and demonstrates that MNGIE may have dyschromatopsia and an electronegative electroretinogram.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): Position paper on diagnosis, prognosis, and treatment by the MNGIE International Network.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disease caused by TYMP mutations and thymidine phosphorylase (TP) deficiency. Thymidine and deoxyuridine accumulate impairing the mitochondrial DNA maintenance and integrity. Clinically, patients show severe and progressive gastrointestinal and neurological manifestations. The onset typically occurs in the second decade of life and mean age at death is 37 years. Signs and symptoms of MNGIE are heterogeneous and confirmatory diagnostic tests are not routinely performed by most laboratories, accounting for common misdiagnosis. Factors predictive of progression and appropriate tests for monitoring are still undefined. Several treatment options showed promising results in restoring the biochemical imbalance of MNGIE. The lack of controlled studies with appropriate follow-up accounts for the limited evidence informing diagnostic and therapeutic choices. The International Consensus Conference (ICC) on MNGIE, held in Bologna, Italy, on 30 March to 31 March 2019, aimed at an evidence-based consensus on diagnosis, prognosis, and treatment of MNGIE among experts, patients, caregivers and other stakeholders involved in caring the condition. The conference was conducted according to the National Institute of Health Consensus Conference methodology. A consensus development panel formulated a set of statements and proposed a research agenda. Specifically, the ICC produced recommendations on: (a) diagnostic pathway; (b) prognosis and the main predictors of disease progression; (c) efficacy and safety of treatments; and (f) research priorities on diagnosis, prognosis, and treatment. The Bologna ICC on diagnosis, management and treatment of MNGIE provided evidence-based guidance for clinicians incorporating patients' values and preferences.

Clinical and molecular characterization of a patient with mitochondrial Neurogastrointestinal Encephalomyopathy.

BACKGROUND: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disorder caused by mutations in TYMP gene, encoding nuclear thymidine phosphorylase (TP). MNGIE mainly presents with gastrointestinal symptoms and is mostly misdiagnosed in many patients as malabsorption syndrome, inflammatory bowel disease, anorexia nervosa, and intestinal pseudo-obstruction. Up to date, more than 80 pathogenic and likely pathogenic mutations associated with the disease have been reported in patients from a wide range of ethnicities. The objective of this study was to investigate the underlying genetic abnormalities in a 25-year-old woman affected with MNGIE. CASE PRESENTATION: The patient was a 25-year-old female referred to our center with the chief complaint of severe abdominal pain and diarrhea for 2 years that had worsened from 2 months prior to admission. The clinical and para-clinical findings were in favor of mitochondrial neurogastrointestinal encephalomyopathy syndrome. Subsequent genetic studies revealed a novel, private, homozygous nonsense mutation in TYMP gene (c. 1013 C > A, p.S338X). Sanger sequencing confirmed the new mutation in the proband. Multiple sequence alignment showed high conservation of amino acids of this protein across different species. CONCLUSION: The detected new nonsense mutation in the TYMP gene would be very important for genetic counseling and subsequent early diagnosis and initiation of proper therapy. This novel pathogenic variant would help us establish future genotype-phenotype correlations and identify different pathways related to this disorder.

Identifying TYMP as an Immune Prognostic Marker in Clear Cell Renal Cell Carcinoma.

BACKGROUND: In clear cell renal cell carcinoma (ccRCC), only some patients can benefit from immunotherapy therapy, and it is urgent to find immune-related molecular markers and targets. METHODS: Thymidine phosphorylase (TYMP) expression level and predictive value in pan-cancers were analyzed using TIMER, GEPIA2, and The Human Protein Atlas. We obtained ccRCC tissues to verify the differential expression of TYMP and confirmed the biological function in vitro. Subsequently, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) are used to explore the potential mechanism of TYMP. Finally, TIMER was used to analyze the infiltration levels and prognostic value of different immune cells. RESULTS: TYMP is upregulated in various cancers, including ccRCC, and there is a certain degree of causality between high expression and poor prognosis in ccRCC. It was confirmed that TYMP knockdown could suppress cell aggressiveness, and cause cell death. Differential analysis showed that 55 differential genes were upregulated in the high-expression groups of TYMP. KEGG and GSEA analyses suggested that TYMP was linked to immune cell invasion, fatty acid metabolism, and P53 signaling pathway. Further investigation revealed that the expression level of TYMP linked positively to T-cell follicular helper and Tregs, but negatively with mast cell activation. Finally, a Nomogram was established on the base of expression level of TYMP and the clinical characteristics of ccRCC patients to predict prognosis. CONCLUSIONS: Patient survival is poor and immune cell infiltration is abnormal when TYMP is highly expressed in ccRCC, suggesting that ccRCC patients could benefit from using TYMP as a molecular diagnostic and therapeutic target.

A Novel Mutation in an MNGIE Patient Presenting with More Prominent Neurological Symptoms than GI Symptoms.

Mitochondrial neurogastrointestinal encephalopathy (MNGIE) is an autosomal recessive disease associated with the mutation of the TYMP gene. MNGIE causes gastrointestinal and neurological symptoms, and the gastrointestinal symptoms are usually notable, which may lead to misdiagnosis. However, we herein report a 29-year-old female who presented with prominent neurological symptoms, while her gastrointestinal symptoms were mild. Brain MRI revealed prominent diffused leukoencephalopathy and peripheral neuropathy was confirmed by the nerve conduction velocity test. Biochemical tests showed elevated plasma thymidine, deoxyuridine, and lactate levels. Molecular genetic testing demonstrated a novel homozygous TYMP c. 447 dupG mutation and the patient's mother was heterozygous for the mutation but had no clinical features. MNGIE was diagnosed based on the results. Unlike other patients who had notable gastrointestinal symptoms, this patient presented with more prominent neurological symptoms than gastrointestinal symptoms, which might have been caused by the novel mutation in the TYMP gene.

Distinctive metabolic remodeling in TYMP deficiency beyond mitochondrial dysfunction.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the TYMP gene, which encodes thymidine phosphorylase (TP). As a cytosolic metabolic enzyme, TP defects affect biological processes that are thought to not be limited to the abnormal replication of mitochondrial DNA. This study aimed to elucidate the characteristic metabolic alterations and associated homeostatic regulation caused by TYMP deficiency. The pathogenicity of novel TYMP variants was evaluated in terms of clinical features, genetic analysis, and structural instability. We analyzed plasma samples from three patients with MNGIE; three patients with m.3243A > G mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS); and four healthy controls (HC) using both targeted and untargeted metabolomics techniques. Transcriptomics analysis and bioenergetic studies were performed on skin fibroblasts from participants in these three groups. A TYMP overexpression experiment was conducted to rescue the observed changes. Compared with controls, specific alterations in nucleosides, bile acids, and steroid metabolites were identified in the plasma of MNGIE patients. Comparable mitochondrial dysfunction was present in fibroblasts from patients with TYMP deficiency and in those from patients with the m.3243A > G mutation. Distinctively decreased sterol regulatory element binding protein (SREBP) regulated cholesterol metabolism and fatty acid (FA) biosynthesis as well as reduced FA degradation were revealed in fibroblasts with TYMP deficiency. The restoration of thymidine phosphorylase activity rescued the observed changes in MNGIE fibroblasts. Our findings indicated that more widespread metabolic disturbance may be caused by TYMP deficiency in addition to mitochondrial dysfunction, which expands our knowledge of the biochemical outcome of TYMP deficiency. KEY MESSAGES: Distinct metabolic profiles in patients with TYMP deficiency compared to those with m.3243A > G mutation. TYMP deficiency leads to a global disruption of nucleoside metabolism. Cholesterol and fatty acid metabolism are inhibited in individuals with MNGIE. TYMP is functionally related to SREBP-regulated pathways. Potential metabolite biomarkers that could be valuable clinical tools to improve the diagnosis of MNGIE.

A comprehensive pan-cancer analysis on the immunological role and prognostic value of TYMP in human cancers.

Background: The TYMP gene encodes an important nucleoside metabolism enzyme which is a rate-limiting enzyme for chemotherapeutic drug metabolism. Previous studies have shown that TYMP is highly expressed in many different tumors, promoting invasiveness and progression, and that it helps to predict the response to chemotherapeutic drugs. However, the role of TYMP in tumor immunity and prognosis remains largely unclear. The purpose of this pan-cancer analysis was to acquire more data on the function of TYMP function and its clinical significance. Methods: To access the TYMP expression, we accessed datasets from The Cancer Genome Atlas (TCGA), Oncomine, Gene Expression Profiling Interactive Analysis (GEPIA), Cancer Cell Line Encyclopedia (CCLE) databases, and analyzed its differential expression between paired tumor and normal samples. We employed PrognoScan and Kaplan-Meier plotter for survival analyses. TYMP mutations were analyzed using cBioPortal. Correlations of TYMP with tumor stage, tumor mutational burden (TMB), microsatellite instability (MSI), immune checkpoint genes (ICGs), and immune cell infiltration were estimated via bioinformatics tools and methods. The CellMiner database was used to predict drug response. Gene set enrichment analysis (GSEA) was applied to explore the biological functions of TYMP in different tumors. Results: Our results indicated that TYMP was overexpressed and also significantly associated with a worse prognosis in several human cancers, such as kidney clear cell carcinoma (KIRC) and lower grade glioma (LGG). TYMP was also associated with TMB, MSI, and ICGs across a variety of malignancies. TYMP was most significantly correlated with immune cell infiltration in five tumors, namely, breast cancer (BRCA), cervical cancer (CESC), KIRC, skin cutaneous melanoma (SKCM), and stomach adenocarcinoma (STAD). Moreover, TYMP expression predicted sensitivity to chemotherapy drugs and also influenced relevant biological pathways, according to enrichment analysis. Conclusions: According to the results of this comprehensive analysis, TYMP is associated with prognosis and tumor immunology, which might make it be a potential therapeutic target for cancer treatment.

A novel thymidine phosphorylase mutation in a family with Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE): Molecular docking, dynamic simulation and computational investigations.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE; OMIM 603041) is a rare inherited metabolic disorder mostly caused by mutations in TYMP gene encoding thymidine phosphorylase (TP) protein that affects the mitochondrial nucleotide metabolism. TP, functionally active as a homodimer, is involved in the salvage pathway of pyrimidine nucleosides. MNGIE-like syndrome having an overlapping phenotype of MNGIE was also described and has been associated with mutations in POLG and RRM2B genes. In the present study, we report the molecular investigation of a consanguineous family including two patients with clinical features suggestive of MNGIE syndrome. Bioinformatics analyses were carried out in addition to mtDNA deletion screening and copy number quantification in the blood of the two patients. Whole exome sequencing and Sanger sequencing analyses revealed the segregation in the affected family a novel mutation c.1205T>A (p.L402Q) within the exon 9 of the TYMP gene. In addition, mtDNA analysis revealed the absence of mtDNA deletions and a decrease of the copy number in the blood of the two patients of the studied family. The p.Leu402Gln mutation was located in a conserved amino acid within the α/ß domain of the TP protein and several software supported its pathogenicity. In addition, and based on docking and molecular dynamic simulation analyses, results revealed that L402Q caused a conformational change in TP mutated structure and could therefore alter its flexibility and stability. These changes prevent also the formation of stable homodimer leading to non-functional protein with partial or complete loss of its catalytic activity.

Mitochondrial neurogastrointestinal encephalomyopathy: Clinical and biochemical impact of allogeneic stem cell transplantation in a Greek patient with one novel TYMP mutation.

We describe the case of a Greek female patient with the Classic form of the ultra- rare and fatal autosomal recessive disorder Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and the impact of allogeneic hematopoietic stem cell transplantation on the biochemical and clinical aspects of the disease. The patient presented at the age of 15 years with severe gastrointestinal symptoms, cachexia, peripheral neuropathy and diffuse leukoencephalopathy. The diagnosis of MNGIE disease was established by the increased levels of thymidine and deoxyuridine in plasma and the complete deficiency of thymidine phosphorylase activity. The novel c.[978dup] (p.Ala327Argfs*?) variant and the previously described variant c.[417 + 1G > A] were identified in TYMP. The donor for the allogeneic hematopoietic stem cell transplantation was her fully compatible sister, a carrier of the disease. The patient had a completely uneventful post- transplant period and satisfactory PB chimerism levels. A marked and rapid decrease in thymidine and deoxyuridine plasma levels and an increase of the thymidine phosphorylase activity to the levels measured in her donor sister was observed and is still present sixteen months post-transplant. Disease symptoms stabilized and some improvement was also observed both in her neurological and gastrointestinal symptoms. Follow up studies will be essential for determining the long term impact of allogeneic hematopoietic stem cell transplantation in our patient.

Targeting thymidine phosphorylase as a potential therapy for bone loss associated with periprosthetic osteolysis.

Macrophages are generally thought to play a key role in the pathogenesis of aseptic loosening through initiating periprosthetic inflammation and pathological bone resorption. The aim of this study was to identify macrophage-derived factors that promote osteoclast differentiation and periprosthetic bone destruction. To achieve this, we examined the effects of 12 macrophage-derived factors that were identified by RNA-seq analysis of stimulated macrophages on osteoclast differentiation. Surprisingly, thymidine phosphorylase (TYMP) was found to trigger significant number of osteoclasts that exhibited resorbing activities on dentine slices. Functionally, TYMP knockdown reduced the number of osteoclasts in macrophages that had been stimulated with polyethylene debris. TYMP were detected in serum and synovial tissues of patients that had been diagnosed with aseptic loosening. Moreover, the administration of TYMP onto calvariae of mice induced pathological bone resorption that was accompanied by an excessive infiltration of inflammatory cells and osteoclasts. The RNA-seq for TYMP-induced-osteoclasts was then performed in an effort to understand action mode of TYMP. TYMP stimulation appeared to activate the tyrosine kinase FYN signaling associated with osteoclast formation. Oral administration of saracatinib, a FYN kinase inhibitor, significantly suppressed formation of bone osteolytic lesions in a polyethylene debris-induced osteolysis model. Our findings highlight a novel molecular target for therapeutic intervention in periprosthetic osteolysis.

Novel Mutations of the TYMP Gene in Mitochondrial Neurogastrointestinal Encephalomyopathy: Case Series and Literature Review.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a multi-system disorder caused by several homozygous or compound heterozygous mutations, mostly in the nuclear gene of TYMP. Our current knowledge on the underlying pathology of the disease is derived through the study of about 200 cases of different ethnicities. Clinical presentations include severe cachexia, weakness, ptosis, diplopia, abdominal cramps or digestive tract disorders, hearing impairment, and paresthesia.Herein, we aim to present five novel mutations of the nuclear gene of TYMP in six Iranian patients diagnosed with MNGIE. In our population, age at the time of diagnosis was 18 to 49 years, while the onset of the symptoms varied from 13 to 20 years. We detected two pathogenic non-frameshift nonsense premature stop codon mutations (c.1013C > A, and c.130C > T), one variant of uncertain significance (VUS) non-frameshift missense mutation (c.345G > T), one likely pathogenic frameshift insertion (c.801_802insCGCG), and one likely benign homozygous non-frameshift deletion (c.1176_1187del) from two siblings. Our findings also confirm the autosomal recessive inheritance pattern of MNGIE in the Iranian population. The lack of knowledge in the area of nuclear gene-modifier genes shadows the genotype-phenotype relationships of MNGIE.

Chemotherapy-induced CDA expression renders resistant non-small cell lung cancer cells sensitive to 5'-deoxy-5-fluorocytidine (5'-DFCR).

BACKGROUND: Pemetrexed (MTA) plus cisplatin combination therapy is considered the standard of care for patients with advanced non-small-cell lung cancer (NSCLC). However, in advanced NSCLC, the 5-year survival rate is below 10%, mainly due to resistance to therapy. We have previously shown that the fraction of mesenchymal-like, chemotherapy-resistant paraclone cells increased after MTA and cisplatin combination therapy in the NSCLC cell line A549. Cytidine deaminase (CDA) and thymidine phosphorylase (TYMP) are key enzymes of the pyrimidine salvage pathway. 5'-deoxy-5-fluorocytidine (5'-DFCR) is a cytidine analogue (metabolite of capecitabine), which is converted by CDA and subsequently by TYMP into 5-fluorouracil, a chemotherapeutic agent frequently used to treat solid tumors. The aim of this study was to identify and exploit chemotherapy-induced metabolic adaptations to target resistant cancer cells. METHODS: Cell viability and colony formation assays were used to quantify the efficacy of MTA and cisplatin treatment in combination with schedule-dependent addition of 5'-DFCR on growth and survival of A549 paraclone cells and NSCLC cell lines. CDA and TYMP protein expression were monitored by Western blot. Finally, flow cytometry was used to analyze the EMT phenotype, DNA damage response activation and cell cycle distribution over time after treatment. CDA expression was measured by immunohistochemistry in tumor tissues of patients before and after neoadjuvant chemotherapy. RESULTS: We performed a small-scale screen of mitochondrial metabolism inhibitors, which revealed that 5'-DFCR selectively targets chemotherapy-resistant A549 paraclone cells characterized by high CDA and TYMP expression. In the cell line A549, CDA and TYMP expression was further increased by chemotherapy in a time-dependent manner, which was also observed in the KRAS-addicted NSCLC cell lines H358 and H411. The addition of 5'-DFCR on the second day after MTA and cisplatin combination therapy was the most efficient treatment to eradicate chemotherapy-resistant NSCLC cells. Moreover, recovery from treatment-induced DNA damage was delayed and accompanied by senescence induction and acquisition of a hybrid-EMT phenotype. In a subset of patient tumors, CDA expression was also increased after treatment with neoadjuvant chemotherapy. CONCLUSIONS: Chemotherapy increases CDA and TYMP expression thereby rendering resistant lung cancer cells susceptible to subsequent 5'-DFCR treatment.

Preclinical investigation of potential use of thymidine phosphorylase-targeting tracer for diagnosis of nonalcoholic steatohepatitis.

INTRODUCTION: Although liver biopsy is the gold standard for the diagnosis of nonalcoholic steatohepatitis (NASH), it has several problems including high invasiveness and sampling errors. Therefore, the development of alternative methods to overcome these disadvantages is strongly required. In this study, we evaluated the potential use of our tracer targeting thymidine phosphorylase (TYMP), 5-[123I]iodo-6-[(2-iminoimidazolidinyl)methyl]uracil ([123I]IIMU) for the diagnosis of NASH. METHODS: The mice used as the NASH model (hereafter, NASH mice) were prepared by feeding a methionine- and choline-deficient diet for 4 weeks. A control group was similarly given a control diet. The expression levels of the TYMP gene and protein in the liver were examined by real-time reverse-transcription polymerase chain reaction and western blot analyses. The localizations of [125I]IIMU and the TYMP protein in the liver were examined by autoradiography and immunohistochemical staining, respectively. Finally, the mice were injected with [123I]IIMU and single-photon emission tomography (SPECT) imaging was conducted. RESULTS: The hepatic expression levels of TYMP were significantly lower in the NASH mice than in the control mice at both mRNA and protein levels, suggesting that a decrease in TYMP level could be an indicator of NASH. [125I]IIMU was uniformly distributed in the liver of the control mice, whereas it showed a patchy distribution in that of the NASH mice. The localization of [125I]IIMU was visually consistent with that of the TYMP protein in the liver of the control and NASH mice. SPECT analysis indicated that the hepatic accumulation of [123I]IIMU in the NASH mice was significantly lower than that in the control mice [SUV (g/ml): 4.14 ± 0.87 (Control) vs 2.31 ± 0.29 (NASH)]. CONCLUSIONS: [123I]IIMU may provide a noninvasive means for imaging TYMP expression in the liver and may be applicable to the diagnosis of NASH.

TYMP Variants Result in Late-Onset Mitochondrial Myopathy With Altered Muscle Mitochondrial DNA Homeostasis.

Biallelic TYMP variants result in the mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), a juvenile-onset disorder with progressive course and fatal outcome. Milder late-onset (>40 years) form has been rarely described. Gene panel sequencing in a cohort of 60 patients featuring muscle accumulation of mitochondrial DNA (mtDNA) deletions detected TYMP defects in three subjects (5%), two of them with symptom onset in the fifth decade. One of the patients only displayed ptosis and ophthalmoparesis. Biochemical and molecular studies supported the diagnosis. Screening of TYMP is recommended in adult patients with muscle mtDNA instability, even in the absence of cardinal MNGIE features.

Mitochondrial neurogastrointestinal encephalomyopathy: approaches to diagnosis and treatment.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare disease caused by mutations in TYMP, the gene encoding for the enzyme thymidine phosphorylase. The resulting enzyme deficiency leads to a systemic accumulation of thymidine and 2'-deoxyuridine and ultimately mitochondrial failure due to a progressive acquisition of secondary mitochondrial DNA (mtDNA) mutations and mtDNA depletion. MNGIE is characterised by gastrointestinal dysmotility, cachexia, peripheral neuropathy, ophthalmoplegia, ptosis and leukoencephalopathy. The disease is progressively degenerative and leads to death at an average age of 37.6 years. Patients invariably encounter misdiagnoses, diagnostic delays, and non-specific clinical management. Despite its rarity, MNGIE has invoked much interest in the development of therapeutic strategies, mainly because it is one of the few mitochondrial disorders where the molecular abnormality is metabolically and physically accessible to manipulation. This review provides a resume of the current diagnosis and treatment approaches and aims to increase the clinical awareness of MNGIE and thereby facilitate early diagnosis and timely access to treatments, before the development of untreatable and irreversible organ damage.

Mitochondrial Neurogastrointestinal Encephalomyopathy Disease in Three Siblings from Pakistan with a Novel Mutation.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare multisystem autosomal recessive disorder. The disease is clinically heterogeneous with gastrointestinal symptoms of intestinal dysmotility and cachexia as well as neurological symptoms of ophthalmoplegia, neuropathy, sensorineural hearing impairment, and diffuse leukoencephalopathy being most prominent. MNGIE is caused by mutations in TYMP , a gene that encodes thymidine phosphorylase (TP)-a cytosolic enzyme. Mutations in TYMP lead to very low TP catalytic activity, resulting in dramatically increased thymidine and deoxyuridine in plasma. We describe the clinical, biochemical, and neuroimaging findings of three boys with MNGIE from a Pakistani family with a novel homozygous mutation, c.798_801dupCGCG p. (Ala268Argfs*?), in exon 7 of TYMP .

Erythrocyte Encapsulated Thymidine Phosphorylase for the Treatment of Patients with Mitochondrial Neurogastrointestinal Encephalomyopathy: Study Protocol for a Multi-Centre, Multiple Dose, Open Label Trial.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder which primarily affects the gastrointestinal and nervous systems. This disease is caused by mutations in the nuclear TYMP gene, which encodes for thymidine phosphorylase, an enzyme required for the normal metabolism of deoxynucleosides, thymidine, and deoxyuridine. The subsequent elevated systemic concentrations of deoxynucleosides lead to increased intracellular concentrations of their corresponding triphosphates, and ultimately mitochondrial failure due to progressive accumulation of mitochondrial DNA (mtDNA) defects and mtDNA depletion. Currently, there are no treatments for MNGIE where effectiveness has been evidenced in clinical trials. This Phase 2, multi-centre, multiple dose, open label trial without a control will investigate the application of erythrocyte-encapsulated thymidine phosphorylase (EE-TP) as an enzyme replacement therapy for MNGIE. Three EE-TP dose levels are planned with patients receiving the dose level that achieves metabolic correction. The study duration is 31 months, comprising 28 days of screening, 90 days of run-in, 24 months of treatment and 90 days of post-dose follow-up. The primary objectives are to determine the safety, tolerability, pharmacodynamics, and efficacy of multiple doses of EE-TP. The secondary objectives are to assess EE-TP immunogenicity after multiple dose administrations and changes in clinical assessments, and the pharmacodynamics effect of EE-TP on clinical assessments.

Safety and Efficacy of Erythrocyte Encapsulated Thymidine Phosphorylase in Mitochondrial Neurogastrointestinal Encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare autosomal recessive disorder of nucleoside metabolism that is caused by mutations in the nuclear thymidine phosphorylase gene (TYMP) gene, encoding for the enzyme thymidine phosphorylase. There are currently no approved treatments for MNGIE. The aim of this study was to investigate the safety, tolerability, and efficacy of an enzyme replacement therapy for the treatment of MNGIE. In this single centre study, three adult patients with MNGIE received intravenous escalating doses of erythrocyte encapsulated thymidine phosphorylase (EE-TP; dose range: 4 to 108 U/kg/4 weeks). EE-TP was well tolerated and reductions in the disease-associated plasma metabolites, thymidine, and deoxyuridine were observed in all three patients. Clinical improvements, including weight gain and improved disease scores, were observed in two patients, suggesting that EE-TP is able to reverse some aspects of the disease pathology. Transient, non-serious adverse events were observed in two of the three patients; these did not lead to therapy discontinuation and they were managed with pre-medication prior to infusion of EE-TP. To conclude, enzyme replacement therapy with EE-TP demonstrated biochemical and clinical therapeutic efficacy with an acceptable clinical safety profile.

Immune-related Genes to Dominate Neutrophil-lymphocyte Ratio (NLR) Associated With Survival of Cetuximab Treatment in Metastatic Colorectal Cancer.

BACKGROUND: Few clinical studies have investigated the association between neutrophil-lymphocyte ratio (NLR) and treatment with cetuximab-based chemotherapy in metastatic colorectal cancer (mCRC). The NLR may reflect immune cells modulating specific cytokine signals in the tumor microenvironment; however, which immune-related genes affect the NLR remain unclear. PATIENTS AND METHODS: In 77 patients with KRAS exon2 wild-type mCRC from prospective trials of first-line chemotherapy with cetuximab, expression levels of 354 immune-related genes were measured in tissue samples obtained from all patients by the HTG EdgeSeq Oncology Biomarker Panel. The association between the NLR and clinical outcomes was evaluated using the Spearman rank correlation coefficient. In addition, 2-sample t tests were performed to investigate which genes among the top 100 genes associated with survival had significantly different expression levels between the NLR-low and NLR-high groups among all measured genes. RESULTS: NLR data were available for 71 patients. The NLR was associated with progression-free survival and overall survival (r = -0.24; P = .040 and r = -0.29; P = .010, respectively). When stratified by the median value of the NLR, the Kaplan-Meier curve of NLR-low versus NLR-high differed significantly for both progression-free survival (median, 11.8 vs. 9.1 months; P = .036) and overall survival (median, 42.8 vs. 26.7 months; P = .029). The 2-sample t test revealed that the expression levels of the LYZ, TYMP, and CD68 genes differed significantly between the NLR-low and NLR-high groups (t test P-value < .005; false discovery rate P-value < .15). CONCLUSION: NLR is significantly associated with survival in patients with mCRC treated with first-line chemotherapy with cetuximab. Genes encoding for activities on macrophages may affect the NLR.