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Cancer Discovery Sep 2023Fumarate accumulation due to loss of fumarate hydratase (FH) drives cellular transformation. Germline FH alterations lead to hereditary leiomyomatosis and renal cell...
UNLABELLED
Fumarate accumulation due to loss of fumarate hydratase (FH) drives cellular transformation. Germline FH alterations lead to hereditary leiomyomatosis and renal cell cancer (HLRCC) where patients are predisposed to an aggressive form of kidney cancer. There is an unmet need to classify FH variants by cancer-associated risk. We quantified catalytic efficiencies of 74 variants of uncertain significance. Over half were enzymatically inactive, which is strong evidence of pathogenicity. We next generated a panel of HLRCC cell lines expressing FH variants with a range of catalytic activities, then correlated fumarate levels with metabolic features. We found that fumarate accumulation blocks de novo purine biosynthesis, rendering FH-deficient cells reliant on purine salvage for proliferation. Genetic or pharmacologic inhibition of the purine salvage pathway reduced HLRCC tumor growth in vivo. These findings suggest the pathogenicity of patient-associated FH variants and reveal purine salvage as a targetable vulnerability in FH-deficient tumors.
SIGNIFICANCE
This study functionally characterizes patient-associated FH variants with unknown significance for pathogenicity. This study also reveals nucleotide salvage pathways as a targetable feature of FH-deficient cancers, which are shown to be sensitive to the purine salvage pathway inhibitor 6-mercaptopurine. This presents a new rapidly translatable treatment strategy for FH-deficient cancers. This article is featured in Selected Articles from This Issue, p. 1949.
Topics: Humans; Fumarate Hydratase; Virulence; Carcinoma, Renal Cell; Kidney Neoplasms; Skin Neoplasms; Purines
PubMed: 37255402
DOI: 10.1158/2159-8290.CD-22-0874 -
Nature Communications Sep 2023Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through...
Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through less clarified mechanisms. Here, we demonstrate that TMZ-derived 5-aminoimidazole-4-carboxamide (AICA) is converted to AICA ribosyl-5-phosphate (AICAR) in GBM cells. This conversion is catalyzed by hypoxanthine phosphoribosyl transferase 1 (HPRT1), which is highly expressed in human GBMs. As the bona fide activator of AMP-activated protein kinase (AMPK), TMZ-derived AICAR activates AMPK to phosphorylate threonine 52 (T52) of RRM1, the catalytic subunit of ribonucleotide reductase (RNR), leading to RNR activation and increased production of dNTPs to fuel the repairment of TMZ-induced-DNA damage. RRM1 T52A expression, genetic interruption of HPRT1-mediated AICAR production, or administration of 6-mercaptopurine (6-MP), a clinically approved inhibitor of HPRT1, blocks TMZ-induced AMPK activation and sensitizes brain tumor cells to TMZ treatment in mice. In addition, HPRT1 expression levels are positively correlated with poor prognosis in GBM patients who received TMZ treatment. These results uncover a critical bifunctional role of TMZ in GBM treatment that leads to chemoresistance. Our findings underscore the potential of combined administration of clinically available 6-MP to overcome TMZ chemoresistance and improve GBM treatment.
Topics: Animals; Humans; Mice; AMP-Activated Protein Kinases; Drug Resistance, Neoplasm; Glioblastoma; Hypoxanthines; Mercaptopurine; Ribonucleotide Reductases; Temozolomide; Hypoxanthine Phosphoribosyltransferase
PubMed: 37737247
DOI: 10.1038/s41467-023-41663-2 -
Journal of Crohn's & Colitis Jul 2023Scepticism about the efficacy of thiopurines for ulcerative colitis [UC] is rising. This study aimed to evaluate mercaptopurine treatment for UC. (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND AND AIMS
Scepticism about the efficacy of thiopurines for ulcerative colitis [UC] is rising. This study aimed to evaluate mercaptopurine treatment for UC.
METHODS
In this prospective, randomized, double-blind, placebo-controlled trial, patients with active UC, despite treatment with 5-aminosalicylates [5-ASA], were randomized for therapeutic drug monitoring [TDM]-guided mercaptopurine treatment or placebo for 52 weeks. Corticosteroids were given in the first 8 weeks and 5-ASA was continued. Proactive metabolite-based mercaptopurine and placebo dose adjustments were applied from week 6 onwards by unblinded clinicians. The primary endpoint was corticosteroid-free clinical remission and endoscopic improvement [total Mayo score ≤2 points and no item >1] at week 52 in an intention-to-treat analysis.
RESULTS
Between December 2016 and April 2021, 70 patients were screened and 59 were randomized at six centres. In the mercaptopurine group, 16/29 [55.2%] patients completed the 52-week study, compared to 13/30 [43.3%] on placebo. The primary endpoint was achieved by 14/29 [48.3%] patients on mercaptopurine and 3/30 [10%] receiving placebo (Δ = 38.3%, 95% confidence interval [CI] 17.1-59.4, p = 0.002). Adverse events occurred more frequently with mercaptopurine [808.8 per 100 patient-years] compared to placebo [501.4 per 100 patient-years]. Five serious adverse events occurred, four on mercaptopurine and one on placebo. TDM-based dose adjustments were executed in 22/29 [75.9%] patients, leading to lower mercaptopurine doses at week 52 compared to baseline.
CONCLUSIONS
Optimized mercaptopurine treatment was superior to placebo in achieving clinical, endoscopic and histological outcomes at 1 year following corticosteroid induction treatment in UC patients. More adverse events occurred in the mercaptopurine group.
Topics: Humans; Colitis, Ulcerative; Mercaptopurine; Prospective Studies; Mesalamine; Remission Induction
PubMed: 36847130
DOI: 10.1093/ecco-jcc/jjad022 -
Journal of Hepatology Apr 2024Patients with autoimmune hepatitis (AIH) almost invariably require lifelong immunosuppressive treatment. There is genuine concern about the efficacy and tolerability of... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND & AIMS
Patients with autoimmune hepatitis (AIH) almost invariably require lifelong immunosuppressive treatment. There is genuine concern about the efficacy and tolerability of the current standard combination therapy of prednisolone and azathioprine. Mycophenolate mofetil (MMF) has emerged as an alternative option. The aim of this study was to compare MMF to azathioprine as induction therapy for AIH.
METHODS
In this 24-week, prospective, randomised, open-label, multicentre superiority trial, 70 patients with treatment-naive AIH received either MMF or azathioprine, both in combination with prednisolone. The primary endpoint was biochemical remission defined as normalisation of serum levels of alanine aminotransferase and IgG after 24 weeks of treatment. Secondary endpoints included safety and tolerability.
RESULTS
Seventy patients (mean 57.9 years [SD 14.0]; 72.9% female) were randomly assigned to the MMF plus prednisolone (n = 39) or azathioprine plus prednisolone (n = 31) group. The primary endpoint was met in 56.4% and 29.0% of patients assigned to the MMF group and the azathioprine group, respectively (difference, 27.4 percentage points; 95% CI 4.0 to 46.7; p = 0.022). The MMF group exhibited higher complete biochemical response rates at 6 months (72.2% vs. 32.3%; p = 0.004). No serious adverse events occurred in patients who received MMF (0%) but serious adverse events were reported in four patients who received azathioprine (12.9%) (p = 0.034). Two patients in the MMF group (5.1%) and eight patients in the azathioprine group (25.8%) discontinued treatment owing to adverse events or serious adverse events (p = 0.018).
CONCLUSIONS
In patients with treatment-naive AIH, MMF with prednisolone led to a significantly higher rate of biochemical remission at 24 weeks compared to azathioprine combined with prednisolone. Azathioprine use was associated with more (serious) adverse events leading to cessation of treatment, suggesting superior tolerability of MMF.
IMPACT AND IMPLICATIONS
This randomised-controlled trial directly compares azathioprine and mycophenolate mofetil, both in combination with prednisolone, for the induction of biochemical remission in treatment-naive patients with autoimmune hepatitis. Achieving complete remission is desirable to prevent disease progression. Patients assigned to the mycophenolate mofetil group reached biochemical remission more often and experienced fewer adverse events. The findings in this trial may contribute to the re-evaluation of international guidelines for the standard of care in treatment-naive patients with autoimmune hepatitis.
TRIAL REGISTRATION NUMBER
#NCT02900443.
Topics: Humans; Female; Male; Azathioprine; Mycophenolic Acid; Hepatitis, Autoimmune; Prospective Studies; Treatment Outcome; Immunosuppressive Agents; Prednisolone; Remission Induction
PubMed: 38101756
DOI: 10.1016/j.jhep.2023.11.032 -
Molecular Diagnosis & Therapy Jan 2024The genetic background of inflammatory bowel disease, both Crohn's disease and ulcerative colitis, has been known for more than 2 decades. In the last 20 years,... (Review)
Review
The genetic background of inflammatory bowel disease, both Crohn's disease and ulcerative colitis, has been known for more than 2 decades. In the last 20 years, genome-wide association studies have dramatically increased our knowledge on the genetics of inflammatory bowel disease with more than 200 risk genes having been identified. Paralleling this increasing knowledge, the armamentarium of inflammatory bowel disease medications has been growing constantly. With more available therapeutic options, treatment decisions become more complex, with still many patients experiencing a debilitating disease course and a loss of response to treatment over time. With a better understanding of the disease, more effective personalized treatment strategies are looming on the horizon. Genotyping has long been considered a strategy for treatment decisions, such as the detection of thiopurine S-methyltransferase and nudix hydrolase 15 polymorphisms before the initiation of azathioprine. However, although many risk genes have been identified in inflammatory bowel disease, a substantial impact of genetic risk assessment on therapeutic strategies and disease outcome is still missing. In this review, we discuss the genetic background of inflammatory bowel disease, with a particular focus on the latest advances in the field and their potential impact on management decisions.
Topics: Humans; Genome-Wide Association Study; Inflammatory Bowel Diseases; Colitis, Ulcerative; Crohn Disease; Azathioprine
PubMed: 37847439
DOI: 10.1007/s40291-023-00678-7 -
Cell Reports. Medicine Aug 2023Azathioprine (AZA) therapy failure, though not the primary cause, contributes to disease relapse and progression in inflammatory bowel disease (IBD). However, the role...
Azathioprine (AZA) therapy failure, though not the primary cause, contributes to disease relapse and progression in inflammatory bowel disease (IBD). However, the role of gut microbiota in AZA therapy failure remains poorly understood. We found a high prevalence of Blautia wexlerae in patients with IBD with AZA therapy failure, associated with shorter disease flare survival time. Colonization of B. wexlerae increased inflammatory macrophages and compromised AZA's therapeutic efficacy in mice with intestinal colitis. B. wexlerae colonization reduced 6-mercaptopurine (6-MP) bioavailability by enhancing selenium-dependent xanthine dehydrogenase (sd-XDH) activity. The enzyme sd-XDH converts 6-MP into its inactive metabolite, 6-thioxanthine (6-TX), thereby impairing its ability to inhibit inflammation in mice. Supplementation with Bacillus (B.) subtilis enriched in hypoxanthine phosphoribosyltransferase (HPRT) effectively mitigated B. wexlerae-induced AZA treatment failure in mice with intestinal colitis. These findings emphasize the need for tailored management strategies based on B. wexlerae levels in patients with IBD.
Topics: Animals; Mice; Mercaptopurine; Azathioprine; Immunosuppressive Agents; Biological Availability; Inflammatory Bowel Diseases; Colitis; Bacteria
PubMed: 37586320
DOI: 10.1016/j.xcrm.2023.101153 -
Current Rheumatology Reports Oct 2023Discuss the prognostic significance of kidney flares in patients with lupus nephritis, associated risk factors, and possible preventative strategies. (Review)
Review
PURPOSE OF REVIEW
Discuss the prognostic significance of kidney flares in patients with lupus nephritis, associated risk factors, and possible preventative strategies.
RECENT FINDINGS
Recently performed clinical trials and observational cohort studies underscore the high frequency of relapses of kidney disease, following initial response, in patients with proliferative and/or membranous lupus nephritis. Analysis of hard disease outcomes such as progression to chronic kidney disease or end-stage kidney disease, coupled with histological findings from repeat kidney biopsy studies, have drawn attention to the importance of renal function preservation that should be pursued as early as lupus nephritis is diagnosed. In this respect, non-randomized and randomized evidence have suggested a number of factors associated with reduced risk of renal flares such as attaining a very low level of proteinuria (< 700-800 mg/24 h by 12 months), using mycophenolate over azathioprine, adding belimumab to standard therapy, maintaining immunosuppressive/biological treatment for at least 3 to 5 years, and using hydroxychloroquine. Other factors that warrant further clarification include serological activity and the use of repeat kidney biopsy to guide the intensity and duration of treatment in selected cases. The results from ongoing innovative studies integrating kidney histological and clinical outcomes, together with an expanding spectrum of therapies in lupus nephritis, are expected to facilitate individual medical care and long-term disease and patient prognosis.
Topics: Humans; Lupus Nephritis; Immunosuppressive Agents; Azathioprine; Kidney; Risk Factors
PubMed: 37452914
DOI: 10.1007/s11926-023-01109-6 -
Journal of Clinical Medicine Oct 2023This study focuses on the use of thiopurines for treating inflammatory bowel diseases (IBD). These drugs undergo enzymatic changes within the body, resulting in active... (Review)
Review
This study focuses on the use of thiopurines for treating inflammatory bowel diseases (IBD). These drugs undergo enzymatic changes within the body, resulting in active and inactive metabolites that influence their therapeutic effects. The research examines the role of genetic polymorphisms in the enzyme thiopurine S-methyltransferase (TPMT) in predicting the therapeutic response and adverse effects of thiopurine treatment. The TPMT genotype variations impact the individual responses to thiopurines. Patients with reduced TPMT activity are more susceptible to adverse reactions (AEs), such leukopenia, hepatotoxicity, pancreatitis, and nausea, which are common adverse effects of thiopurine therapy. The therapeutic monitoring of the metabolites 6-thioguanine nucleotides (6-TGN) and 6-methyl mercaptopurine (6-MMP) is proposed to optimize treatment and minimize AEs. Patients with higher 6-TGN levels tend to have better clinical responses, while elevated 6-MMP levels are linked to hepatotoxicity. Genotyping for TPMT before or during treatment initiation is suggested to tailor dosing strategies and enhance treatment efficacy while reducing the risk of myelosuppression. In conclusion, this study highlights the importance of considering genetic variations and metabolite levels in optimizing thiopurine therapy for IBD patients, focusing on balance therapeutic efficacy with the prevention of adverse effects and contributing to personalized treatment and better patient outcomes.
PubMed: 37959208
DOI: 10.3390/jcm12216742 -
Cell Reports Aug 2023Small cell lung cancer (SCLC) is one of the deadliest human cancers, with a 5-year survival rate of ∼7%. Here, we performed a targeted proteomics analysis of human...
Small cell lung cancer (SCLC) is one of the deadliest human cancers, with a 5-year survival rate of ∼7%. Here, we performed a targeted proteomics analysis of human SCLC samples and thereby identified hypoxanthine phosphoribosyltransferase 1 (HPRT1) in the salvage purine synthesis pathway as a factor that contributes to SCLC malignancy by promoting cell survival in a glutamine-starved environment. Inhibition of HPRT1 by 6-mercaptopurine (6-MP) in combination with methotrexate (MTX), which blocks the de novo purine synthesis pathway, attenuated the growth of SCLC in mouse xenograft models. Moreover, modulation of host glutamine anabolism with the glutamine synthetase inhibitor methionine sulfoximine (MSO) in combination with 6-MP and MTX treatment resulted in marked tumor suppression and prolongation of host survival. Our results thus suggest that modulation of host glutamine anabolism combined with simultaneous inhibition of the de novo and salvage purine synthesis pathways may be of therapeutic benefit for SCLC.
PubMed: 37531252
DOI: 10.1016/j.celrep.2023.112899 -
Frontiers in Immunology 2023Various immunosuppressive regimens have been developed for the treatment of lupus nephritis (LN). This study aimed to compare the efficacy and safety of... (Meta-Analysis)
Meta-Analysis
INTRODUCTION
Various immunosuppressive regimens have been developed for the treatment of lupus nephritis (LN). This study aimed to compare the efficacy and safety of immunosuppressive regimens in adults with LN.
METHODS
We systematically searched the PubMed, Embase, and Cochrane Central Register of Controlled Trials databases, including conference proceedings, trial registries, and reference lists, from inception until July 10, 2022. The effects of treatment were compared and ranked using the surface under the cumulative ranking curve (SUCRA). The primary endpoint was total remission. The secondary endpoints were complete remission, systemic lupus erythematosus disease activity index (SLEDAI), relapse, all-cause mortality, end-stage renal disease (ESRD), infection, herpes zoster, ovarian failure, myelosuppression, and cancer.
RESULTS
Sixty-two trials reported in 172 studies involving 6,936 patients were included in the network meta-analysis. The combination of tacrolimus (TAC), mycophenolate mofetil (MMF), and glucocorticoid (GC) provided the best result for the total remission rate (SUCRA, 86.63%) and SLEDAI (SUCRA, 91.00%), while the combination of voclosporin (VCS) , MMF and GC gave the best improvement in the complete remission rate (SUCRA, 90.71%). The combination of cyclophosphamide (CYC), MMF and GC was associated with the lowest risk of relapse (SUCRA, 85.57%) and cancer (SUCRA, 85.14%), while the combination of obinutuzumab (OTB), MMF and GC was associated with the lowest risk of all-cause mortality (SUCRA, 84.07%). Rituximab (RTX) plus MMF plus GC was associated with the lowest risk of ESRD (SUCRA, 83.11%), while the risk of infection was lowest in patients treated with azathioprine (AZA) plus CYC plus GC (SUCRA, 68.59%). TAC plus GC was associated with the lowest risk of herpes zoster (SUCRA, 87.67%) and ovarian failure (SUCRA, 73.60%). Cyclosporine (CsA) plus GC was associated with the lowest risk of myelosuppression (SUCRA, 79.50%), while AZA plus GC was associated with the highest risk of myelosuppression (SUCRA, 16.25%).
DISCUSSION
This study showed that a combination of TAC, MMF and GC was the best regimen for improving the total remission rate. The optimal regimen for specific outcomes should be highlighted for high-risk patients.
Topics: Humans; Adult; Immunosuppressive Agents; Lupus Nephritis; Network Meta-Analysis; Treatment Outcome; Cyclophosphamide; Tacrolimus; Azathioprine; Mycophenolic Acid; Glucocorticoids; Bone Marrow Diseases; Kidney Failure, Chronic; Recurrence; Herpes Zoster; Neoplasms
PubMed: 37901212
DOI: 10.3389/fimmu.2023.1232244