Febuxostat Increases Ventricular Arrhythmogenesis Through Calcium Handling Dysregulation in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Febuxostat is a xanthine oxidase inhibitor used to reduce the formation of uric acid and prevent gout attacks. Previous studies have suggested that febuxostat was associated with a higher risk of cardiovascular events, including atrial fibrillation, compared with allopurinol, another anti-hyperuricemia drug. Whereas in our clinical practice, we identified 2 cases of febuxostat-associated ventricular tachycardia (VT) events. The proarrhythmogenic effects of febuxostat on human cardiomyocytes and underlined mechanisms remain poorly understood. In this study, we employed real-time cell analysis and calcium transient to investigate the effects of febuxostat on the cytotoxicity and electrophysiology properties of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Up to 10 µM febuxostat treatment did not show toxicity to cell viability. However, 48-h febuxostat exposure generated dose-dependent increased irregular calcium transients and decreased calcium transient amplitude. Furthermore, RNA-seq analysis indicated that the MAPK signaling pathway was enriched in the febuxostat-treated group, especially the protein kinases c-Jun N-terminal kinase (JNK). Western blotting of 3 main protein kinases demonstrated that JNK activation is related to febuxostat-induced arrhythmia rather than extracellular signal regulated kinases (ERK) or p38. The dysfunctional calcium dynamics of febuxostat-treated hiPSC-CMs could be ameliorated by SP600125, the inhibitor of JNK. In conclusion, our study demonstrated that febuxostat increases the predisposition to ventricular arrhythmia by dysregulating calcium dynamics.

Adipose stem cell secretome markedly improves rodent heart and human induced pluripotent stem cell-derived cardiomyocyte recovery from cardioplegic transport solution exposure.

Heart transplantation is a life-saving therapy for end-stage organ failure. Organ deterioration during transportation limits storage to 4 hours, limiting hearts available. Approaches ameliorating organ damage could increase the number of hearts acceptable for transplantation. Prior studies show that adipose-derived stem/stromal cell secretome (ASC-S) rescues tissues from postischemic damage in vivo. This study tested whether ASC-S preserved the function of mouse hearts and human induced pluripotent stem cell-derived cardiomyocytes (iCM) exposed to organ transportation and transplantation conditions. Hearts were subjected to cold University of Wisconsin (UW) cardioplegic solution ± ASC-S for 6 hours followed by analysis using the Langendorff technique. In parallel, the effects of ASC-S on the recovery of iCM from UW solution were examined when provided either during or after cold cardioplegia. Exposure of hearts and iCM to UW deteriorated contractile activity and caused cell apoptosis, worsening in iCM as a function of exposure time; these were ameliorated by augmenting with ASC-S. Silencing of superoxide dismutase 3 and catalase expression prior to secretome generation compromised the ASC-S cardiomyocyte-protective effects. In this study, a novel in vitro iCM model was developed to complement a rodent heart model in assessing efficacy of approaches to improve cardiac preservation. ASC-S displays strong cardioprotective activity on iCM either with or following cold cardioplegia. This effect is associated with ASC-S-mediated cellular clearance of reactive oxygen species. The effect of ASC-S on the temporal recovery of iCM function supports the possibility of lengthening heart storage by augmenting cardioplegic transport solution with ASC-S, expanding the pool of hearts for transplantation.

Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Recent data suggested a causative role of uric acid (UA) in the development of renal disease, in which endothelial dysfunction is regarded as the key mechanism. Endothelial-to-mesenchymal transition (EndoMT) and shedding of the glycocalyx are early changes of endothelial dysfunction. We investigated whether UA induced EndoMT in HUVECs and an animal model of hyperuricemia fed with 2% oxonic acid for 4 wk. UA induced EndoMT in HUVECs with a generation of reactive oxygen species via the activation of membranous NADPH oxidase (from 15 min) and mitochondria (from 6 h) along with glycocalyx shedding (from 6 h), which were blocked by probenecid. GM6001, an inhibitor of matrix metalloproteinase, alleviated UA-induced glycocalyx shedding and EndoMT. Antioxidants including N-acetyl cysteine, apocynin, and mitotempo ameliorated EndoMT; however, they did not change glycocalyx shedding in HUVECs. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries (PTCs) was substantially decreased with a de novo expression of α-smooth muscle actin in PTCs. Plasma level of syndecan-1 was increased in hyperuricemic rats, which was ameliorated by allopurinol. UA caused a phenotypic transition of endothelial cells via induction of oxidative stress with glycocalyx shedding, which could be one of the mechanisms of UA-induced endothelial dysfunction and kidney disease.-Ko, J., Kang, H.-J., Kim, D.-A., Kim, M.-J., Ryu, E.-S., Lee, S., Ryu, J.-H., Roncal, C., Johnson, R. J., Kang, D.-H. Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Allopurinol-induced toxic epidermal necrolysis featuring almost 60% skin detachment.

RATIONALE: Toxic epidermal necrolysis (TEN) is a life-threatening, immunologically mediated, and usually drug-induced disease. Rarely, clinical pharmacists participating in finding the etiology have been reported. PATIENTS CONCERNS: A 33-year-old male presented to the emergency department with a 1-day history of fever and rash. The patient, being newly diagnosed with gout 10 days ago, received allopurinol at a dose of 250 mg by mouth daily. After 10 days' exposure to allopurinol, the patient manifested with an "influenza-like" prodromal phase (fever of 38°C, throat pains), which was treated with amoxicillin and nonsteroidal anti-inflammatory drugs of the oxicam type. The next day, he developed a worsening fever of 39.5°C, accompanied by a pruriginous rash all over his body. DIAGNOSIS: On physical examination, we observed coalescing dusky red macules over >60% of his body surface area, with blisters and detachment of large sheets of necrolytic epidermis all over his chest and face. The diagnosis of TEN was confirmed. INTERVENTIONS: The patient recovered following treatment with short-term high-dose methylprednisolone sodium succinate, immunoglobulin therapy, topical medication, and supportive therapy. OUTCOMES: He showed a slow but progressive improvement both in symptoms and cutaneous manifestations. Reepithelization of the skin was achieved after 3 weeks. LESSONS: Drug-induced-TEN is potentially fatal. This case underlines the necessity of asking medication history in detail and detecting related drug gene to correctly identify the cause of TEN.

The teratogenicity of allopurinol: A comprehensive review of animal and human studies.

Allopurinol is widely used in the management of multiple disorders including gout, kidney stones and inflammatory bowel disease. Despite of long-term experience, its safety in pregnancy has been debated due to reports on possible teratogenicity. We aimed to review the literature on the safety of allopurinol in pregnancy and offspring. In animals, allopurinol induced species-specific reproductive toxicity. In humans, a total of 53 allopurinol exposed infants were reported in the literature. Major congenital malformations were reported in two cases with a comparable pattern of multiple abnormalities. Five other infants had minor birth defects. In conclusion, the association between allopurinol and teratogenicity appears to be weak and limited to two reports with uncertain causality. However, the available data are insufficient to make a certain judgement, and as allopurinol treatment evolves, report and prospective follow-up of all exposed infants (i.e. deviant and normal cases) should be encouraged.

Xanthine oxidase inhibitors and sepsis.

Xanthine oxidase activation occurs in sepsis and results in the generation of uric acid (UrAc) and reactive oxygen species (ROS). We aimed to evaluate the effect of xanthine oxidase inhibitors (XOis) in rats stimulated with lipopolysaccharide (LPS). LPS (10 mg/kg) was administered intraperitoneally (i.p.) immediately after allopurinol (Alo, 2 mg/kg) or febuxostat (Feb, 1 mg/kg) every 24 h for 3 days. To increase UrAc levels, oxonic acid (Oxo) was administered by gavage (750 mg/kg per day) for 5 days. Animals were divided into the following 10 groups (n = 6 each): (1) Control, (2) Alo, (3) Feb, (4) LPS, (5) LPSAlo, (6) LPSFeb, (7) Oxo, (8) OxoLPS, (9) OxoLPSAlo, and (10) OxoLPSFeb. Feb with or without Oxo did not aggravate sepsis. LPS administration (with or without Oxo) significantly decreased the creatinine clearance (ClCr) in LPSAlo (60%, P < 0.01) versus LPS (44%, P < 0.05) and LPSFeb (35%, P < 0.05). Furthermore, a significant increase in mortality was observed with LPSAlo (28/34, 82%) compared to LPS treatment alone (10/16, 63%) and LPSFeb (11/17, 65%, P < 0.05). In addition, increased levels of thiobarbituric acid reactive substances (TBARS), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 were observed at 72 h compared to the groups that received LPS and LPSFeb with or without Oxo. In this study, coadministration of Alo in LPS-induced experimental sepsis aggravated septic shock, leading to mortality, renal function impairment, and high ROS and proinflammatory IL levels. In contrast, administration of Feb did not potentiate sepsis, probably because it did not interfere with other metabolic events.

Allopurinol suppresses expression of the regulatory T-cell migration factors TARC/CCL17 and MDC/CCL22 in HaCaT keratinocytes via restriction of nuclear factor-κB activation.

Recent studies have shown that sparse distribution of regulatory T cells (Tregs) in the skin might be involved in the onset of severe cutaneous adverse drug reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. Treg migration toward epithelial cells is regulated by certain chemokines, including TARC/CCL17 and MDC/CCL22. In this study, we analyzed the effect of allopurinol (APN), a drug known to cause severe adverse reactions, on the expression of factors affecting Treg migration and the mechanisms involved. APN inhibited the tumor necrosis factor (TNF)-α- and interferon (IFN)-γ-associated expression of TARC/CCL17 and MDC/CCL22 mRNA in HaCaT cells in a dose-dependent manner. Consistent with this, APN also suppressed TNF-α- and IFN-γ-induced production of TARC/CCL17 and MDC/CCL22 proteins and the migration of C-C chemokine receptor type 4-positive cells. Activity of the transcription factors NF-κB and STAT1, which are involved in TARC/CCL17 and MDC/CCL22 expression, was also investigated. APN inhibited activation of NF-κB, but not that of STAT1. Furthermore, it restricted p38 MAPK phosphorylation. These results suggest that APN inhibits TNF-α- and IFN-γ-induced TARC/CCL17 and MDC/CCL22 production through downregulation of p38 MAPK and NF-κB signaling, resulting in the sparse distribution of Tregs in the skin of patients with APN-associated Stevens-Johnson syndrome/toxic epidermal necrolysis.

Allopurinol induces innate immune responses through mitogen-activated protein kinase signaling pathways in HL-60 cells.

Allopurinol, an inhibitor of xanthine oxidase, is a frequent cause of severe cutaneous adverse reactions (SCARs) in humans, including drug rash with eosinophilia and systemic symptoms, Stevens-Johnson syndrome and toxic epidermal necrolysis. Although SCARs have been suspected to be immune-mediated, the mechanisms of allopurinol-induced SCARs remain unclear. In this study, we examined whether allopurinol has the ability to induce innate immune responses in vitro using human dendritic cell (DC)-like cell lines, including HL-60, THP-1 and K562, and a human keratinocyte cell line, HaCaT. In this study, we demonstrate that treatment of HL-60 cells with allopurinol significantly increased the mRNA expression levels of interleukin-8, monocyte chemotactic protein-1 and tumor necrosis factor α in a time- and concentration-dependent manner. Furthermore, allopurinol induced the phosphorylation of mitogen-activated protein kinases (MAPK), such as c-Jun N-terminal kinase and extracellular signal-regulated kinase, which regulate cytokine production in DC. In addition, allopurinol-induced increases in cytokine expression were inhibited by co-treatment with the MAPK inhibitors. Collectively, these results suggest that allopurinol has the ability to induce innate immune responses in a DC-like cell line through activation of the MAPK signaling pathways. These results indicate that innate immune responses induced by allopurinol might be involved in the development of allopurinol-induced SCARs. Copyright © 2015 John Wiley & Sons, Ltd.

Long-term effects of prenatal allopurinol treatment on brain plasticity markers in low and normal birth weight piglets.

In this study, we investigated the effect of antenatal allopurinol (ALLO) treatment on levels and expression of plasticity markers in the dorsal hippocampus of low (LBW) and normal (NBW) birth weight piglets. ALLO treatment given daily in the last trimester to pregnant sows had a protective effect on neuronal plasticity markers in their piglets. ALLO increases protein levels of BDNF and the postsynaptic marker PSD95 in LBW and NBW piglets. ALLO treatment increases the pCREB/CREB ratio in LBW piglets to a similar level as that found in untreated NBW piglets. In conclusion, antioxidant treatment administered in the last trimester might be a promising treatment for LBW neonates.

3,4-Dihydroxy-5-nitrobenzaldehyde (DHNB) is a potent inhibitor of xanthine oxidase: a potential therapeutic agent for treatment of hyperuricemia and gout.

Hyperuricemia, excess of uric acid in the blood, is a clinical problem that causes gout and is also considered a risk factor for cardiovascular disease. The enzyme xanthine oxidase (XO) produces uric acid during the purine metabolism; therefore, discovering novel XO inhibitors is an important strategy to develop an effective therapy for hyperuricemia and gout. We found that 3,4-dihydroxy-5-nitrobenzaldehyde (DHNB), a derivative of the natural substance protocatechuic aldehyde, potently inhibited XO activity with an IC50 value of 3 µM. DHNB inhibited XO activity in a time-dependent manner, which was similar to that of allopurinol, a clinical XO inhibitory drug. DHNB displayed potent mixed-type inhibition of the activity of XO, and showed an additive effect with allopurinol at the low concentration. Structure-activity relationship studies of DHNB indicated that the aldehyde moiety, the catechol moiety, and nitration at C-5 were required for XO inhibition. DHNB interacted with the molybdenum center of XO and was slowly converted to its carboxylic acid at a rate of 10⁻¹° mol/L/s. In addition, DHNB directly scavenged free radical DPPH and ROS, including ONOO⁻ and HOCl. DHNB effectively reduced serum uric acid levels in allantoxanamide-induced hyperuricemic mice. Furthermore, mice orally given a large dose (500 mg/kg) of DHNB did not show any side effects, while 42% of allopurinol (500 mg/kg)-treated mice died and their offspring lost their fur. Thus, DHNB could be an outstanding candidate for a novel XO inhibitory drug that has potent activity and low toxicity, as well as antioxidant activity and a distinct chemical structure from allopurinol.

Role of hydroxyethyl starch in ischemia-reperfusion injury in rat intestinal transplantation.

OBJECTIVE: This study was designed to evaluate the role of 0%, 3%, 6% hydroxyethyl starch (HES) and University of Wisconsin (UW) perfusion and preservation solutions on ischemia-reperfusion injury (IRI) of rat intestinal transplantations, solutions, respectively. MATERIALS AND METHODS: Rats underwent orthotopic intestinal transplantation (Lewis to Lewis) after using perfusion and preservation saline (group l), 3% HES (group 2), 6% HES (group 3), or UW (group 4) solutions. The change in weight was recorded from preoperative to postoperative day (POD) 30. At 30 minutes after reperfusion, we harvested intestinal juice preoperatively as well as at 30 minutes after reperfusion and on POD 1 and 3 when recipients underwent open surgery for maltose absorption tests and sampling. The Park' scores of IRI were evaluated by light microscopy after hematoxylin and eosin (H&E) staining. RESULTS: An increased weight was more evident in group 2 than the other groups, particularly the on POD 1 and POD 3 (P < .05). It was significantly greater than groups 1 and 3 on POD 7 (P < .05). Compared with the other groups, the 30-minute post-reperfusion. Park score and intestinal juice content in group 2 was decreased significantly (P < .01), while in group 3 the Park score was increased, and the maltose absorption level decreased significantly (P < .05). CONCLUSION: Three percent HES solution attenuated IRI in rat intestinal transplantation. High-concentration HES solutions were unfit for intestinal preservation. Thus the adverse effects of UW solution may be attribute at least in part to its high HES, concentration.

Protein kinase C inhibition ameliorates posttransplantation preservation injury in rat renal transplants.

BACKGROUND: Prolonged cold preservation frequently causes delayed renal graft function resulting from tubular epithelial injury. Inhibition of signal transduction downstream from protein kinase C (PKC) may reduce renal ischemia-reperfusion injury and confer renal graft protection. We therefore evaluated the effect of sotrastaurin, a small-molecule inhibitor of Ca²âº-dependent and Ca²âº-independent PKC isoforms, in comparison with mycophenolic acid (MPA) on rat renal transplants with prolonged cold preservation. METHODS: Donor kidneys from male Lewis rats were cold stored in University of Wisconsin solution for 24 hr before syngeneic grafting. Recipients received sotrastaurin (30 mg/kg twice daily), MPA (20 mg/kg/day), or vehicle through gavage starting 1 hr after surgery. Renal function was evaluated by serum creatinine and histology on day 2 (acute injury) and day 7 (repair phase) after transplantation. Postreperfusion inflammation was determined by real-time polymerase chain reaction of proinflammatory genes and histology. Signaling mechanisms were studied by Western blotting and immunohistochemistry. RESULTS: Sotrastaurin enhanced immediate transplant function, attenuated epithelial injury, and accelerated renal function recovery compared with MPA. Despite the stronger anti-inflammatory capacity of MPA, only sotrastaurin treatment achieved significant cellular protection with persisting reduced apoptosis of tubular epithelial cells. Decreased phosphorylation of extracellular signal-regulated protein kinase and p66Shc adaptor protein, both involved in cellular stress and apoptosis, were likely the responsible mechanism of action. CONCLUSIONS: The PKC inhibitor sotrastaurin effectively ameliorated ischemia-reperfusion organ damage and promoted cytoprotection in a clinically relevant model of extended renal cold preservation followed by transplantation. Pharmacologic targeting of PKC may be beneficial for recipients receiving renal transplants at risk for delayed graft function.

HLA-B*58:01 allele is associated with augmented risk for both mild and severe cutaneous adverse reactions induced by allopurinol in Han Chinese.

AIM: Allopurinol is widely used as an effective urate-lowering drug and is one of the most frequent causes of cutaneous adverse drug reactions (cADRs). Recently, a strong association of HLA-B*58:01 with allopurinol-induced severe cADRs was identified. This study investigated the predisposition to different types of allopurinol-cADRs conferred by HLA-B*5801 in a Han population from mainland China. PATIENTS & METHODS: HLA-B genotyping was performed on 38 Chinese patients with different types of allopurinol-cADRs from 2008 to 2011. RESULTS: All the allopurinol-cADR patients carried HLA-B*58:01, in contrast with only 11.11% (7/63) in the allopurinol-tolerant patients (odds ratio [OR] = 580.07; p < 0.0001) and 13.99% (80/572) in a Han Chinese population from the human MHC database (dbMHC; OR: 471.09; p < 0.0001) carried the genotype. Each type of allopurinol cADRs revealed a statistically significant association with HLA-B*58:01. In particular, the risk of allopurinol-induced maculopapular eruption was significantly higher in patients with HLA-B*58:01 (OR: 339.00; p < 0.0001). CONCLUSION: The strong association of both the mild and severe types of allopurinol cADRs with the HLA-B*58:01 allele were observed. The results indicated that the prospective use of a genetic test of HLA-B*58:01 might reduce the prevalence of allopurinol-induced cADRs. Original submitted 7 March 2012; Revision submitted 21 May 2012.

[Allopurinol-induced hypersensitivity syndrome resulting in death]. / Allopurinolinduziertes Hypersensitivitätssyndrom mit Todesfolge.

The present report describes the case of a 67-year-old patient who developed an allopurinol-induced hypersensitivity syndrome (AHS) with toxic epidermal necrolysis and subsequently died of septic multiorgan failure. Considering the increasing prescription rate of allopurinol, the present case report intends to demonstrate the underestimated threat of AHS.

Basic measures and systemic medical treatment of patients with toxic epidermal necrolysis.

BACKGROUND: With an incidence of 1.5-1.8/1 million inhabitants per year, toxic epidermal necrolysis is a rare but life threatening disease. It is almost always drug-induced and its lethality is pronounced with up to 50 %. Several therapeutic options are described in literature; however, there is still lack of a universally accepted and specific therapy of toxic epidermal necrolysis. METHODS: This survey considers 8 cases of toxic epidermal necrolysis diagnosed and treated in our clinic from 2003 to 2007. The epidermal sloughing was > 30 % of the body surface in each case. RESULTS: After immediately discontinuing the drug suspected of being responsible for toxic epidermal necrolysis, we treated with systemic corticosteroids in an initial dose of up to 1.5 mg/kg. Moreover, special emphasis was put on basic measures such as control of vital parameters. With this treatment we reached good results; none of the patients died. conclusions: Immediate beginning of therapy is essential for a successful treatment of toxic epidermal necrolysis. Besides systemic therapy with corticosteroids, certain basic measures such as isolation of patients at adequate room temperature to prevent hypothermia, strict control of circulation, temperature and laboratory parameters, daily smears of skin and mucous membranes and a diet rich in calories due to the catabolic metabolic status are very important for successful outcome.

Inherent toxicity of organ preservation solutions to cultured hepatocytes.

Organ preservation solutions have been designed to protect grafts against the injury inflicted by cold ischemia. However, toxicity of University of Wisconsin (UW) solution during rewarming has been reported. Therefore, we here assessed the toxicity of UW, histidine-tryptophan-ketoglutarate (HTK), Euro-Collins, histidine-lactobionate (HL), sodium-lactobionate-sucrose and Celsior solutions in cultured hepatocytes under hypothermic (4 degrees C), intermediate (21 degrees C) and physiological (37 degrees C) conditions. Marked toxicity of UW, HTK, HL and Euro-Collins solutions was observed at both 37 and 21 degrees C. With the exception of UW solution, these solutions also increased cell injury during cold incubation (LDH release after 18 h at 4 degrees C: HTK 76+/-2%, Euro-Collins 78+/-17%, HL 81+/-15%; control: Krebs-Henseleit buffer 20+/-6%). Testing of individual components using modified Krebs-Henseleit buffers suggested that histidine and phosphate are responsible for (part of) this toxicity. These potential toxicities should be taken into account in the development of future preservation solutions.

Purine nucleobase transport in amastigotes of Leishmania mexicana: involvement in allopurinol uptake.

Nucleobase and nucleoside transporters play central roles in the biochemistry of parasitic protozoa, as they lack the ability to synthesize purines de novo and are absolutely reliant upon purine salvage from their hosts. Furthermore, such transporters are potentially critical to the pharmacology of these important human pathogens, because they mediate the uptake of purine analogues, as well as some nonpurine drugs, that can be selectively cytotoxic to the parasites. We here report the first identification and characterization of a purine nucleobase transporter in Leishmania amastigotes. Uptake of [3H]hypoxanthine by Leishmania mexicana amastigotes was mediated by a single high-affinity transporter, LmexNBT1, with a Km of 1.6 +/- 0.4 microM and high affinity for adenine, guanine, and xanthine but low affinity for nucleosides and pyrimidine nucleobases. Allopurinol, an antileishmanial hypoxanthine analogue, was apparently taken up by the same transporter. Using [3H]allopurinol, a Km value of 33.6 +/- 6.0 microM was obtained. All evidence was compatible with a model of a single purine nucleobase transporter being expressed in amastigotes. Using various purine nucleobase analogues, a model for the interactions between hypoxanthine and the transporter's permeant binding site was constructed. The binding interactions were compared with those of the LmajNBT1 transporter in Leishmania major promastigotes and found to be very similar.

[Life-threatening adverse effects of pharmacologic antihyperuricemic therapy]. / Lebensbedrohliche Nebenwirkungen der Gichtbehandlung.

Minor hypersensitivity reactions to allopurinol presenting as skin rash occur in approximately 2% of patients. A more severe, albeit rare, hypersensitivity reaction with fever, eosinophilia, dermatitis, renal failure, vasculitis and hepatic dysfunction carries a mortality of up to 20%. The incidence of this severe reaction can probably be reduced by adjusting the dose of allopurinol in patients with impaired renal function. Azathioprine and mercaptopurine are metabolised by xanthine oxidase, the enzyme that is inhibited by allopurinol. Concomitant administration can result in life-threatening neutropenia unless the dose of allopurinol is reduced by approximately 75%. The uricosuric agent benzbromarone has recently been withdrawn from the market because of several cases of fulminant hepatic failure with subsequent death of the patient or liver transplantation.

A novel parasite-derived suicide gene for cancer gene therapy with specificity for lung cancer cells.

The enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) expressed by the parasite Trypanosoma brucei (Tb) can convert allopurinol, a purine analogue, to corresponding nucleotides with greater efficiency than its human homologue. We have developed a retroviral system that expresses the parasitic enzyme and tested its capacity to activate the prodrug allopurinol to a cytotoxic metabolite. Cytotoxicity assays demonstrated that five non-small cell lung carcinoma cell lines transduced with the construct were sensitized to the prodrug by 2.1- to 7.6-fold compared with control values. This selectivity was not observed in seven other cell lines also expressing the construct, such as breast carcinoma. Assays indicated that enhanced cytotoxicity to allopurinol correlated with induction of apoptosis in lung cancer cells. The selectivity of this suicide gene was not explained either by the TbHGPRT expression or by the allopurinol accumulation. Our study shows that this novel system may represent a therapeutic tool for gene prodrug targeting of lung cancer, considering the fact that allopurinol is well tolerated in humans.