GAS5 promotes cytarabine induced myelosuppression via inhibition of hematopoietic stem cell differentiation.

Cytarabine (Ara-C) is widely used in the induction chemotherapy for acute myeloid leukemia (AML). Association between LncRNA GAS5 genetic polymorphism and the recovery of hematopoietic function after Ara-C-based chemotherapy is observed. This study aimed to identify whether intervention of GAS5 expression and GAS5 genotype affect Ara-C-induced inhibition of hematopoietic stem cells (HSCs) differentiation. In this study, cord blood-derived CD34+ cells were cultured in vitro, and a cell model of myelosuppression was established by treatment of CD34+ cells with Ara-C. The effect of GAS5 overexpression, Ara-C treatment, and GAS5 rs55829688 genotype on the hematopoietic colony-forming ability of CD34+ cells was assessed using methylcellulose-based colony forming unit assay. GAS5 overexpression slowed down the proliferation of cord blood-derived CD34+ cells significantly (p < 0.05) and decreased their ability to form hematopoietic colonies in vitro. Ara-C significantly reduced the hematopoietic colony-forming ability of CD34+ cells in vitro (p < 0.0001), and overexpressing GAS5 further decreased the number of hematopoietic colonies. GAS5 expression was higher in CD34+ cells than in CD34- cells, and positively correlated with GATA1 mRNA expression in CD34+ cells in vitro culture. However, GAS5 genotype had no effect on the total number of hematopoietic colonies formed from cord blood-derived CD34+ cells. In conclusion, our study highlights that GAS5 inhibited the in vitro proliferation and reduced the hematopoietic colony-forming ability of cord blood-derived CD34+ cells, with the most pronounced effect observed on CFU-GEMM formation. GAS5 also enhanced the inhibitory effect of Ara-C on the in vitro hematopoietic ability of CD34+ HSCs.

Lower cardiotoxicity of CPX-351 relative to daunorubicin plus cytarabine free-drug combination in hiPSC-derived cardiomyocytes in vitro.

Liposomal formulations are hypothesized to alleviate anthracycline cardiotoxicity, although this has only been documented clinically for doxorubicin. We developed an in vitro multiparametric model using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) to assess the relative toxicity of anthracyclines across formulations. Proof of concept was established by treating hiPSC-CM with equivalent concentrations of free and liposomal doxorubicin. The study was then repeated with free daunorubicin plus cytarabine and CPX-351, a dual-drug liposomal encapsulation of daunorubicin/cytarabine. hiPSC-CM were treated with free-drug or liposomal formulations for 24 h on Days 1, 3, and 5 at equivalent concentrations ranging from 0 to 1000 ng/mL and assessed on subsequent days. Free-drug treatment resulted in concentration-dependent cumulative cytotoxicity (microscopy), more profound decrease in ATP levels, and significant time- and concentration-dependent decreases in oxygen consumption versus liposomal formulations (p < 0.01). Repeated free-drug exposure also resulted in greater release of biomarkers (cardiac troponin I, FABP3) and lactate dehydrogenase, as well as in a biphasic rhythmicity response (initial increase followed by slowing/quiescence of beating) indicating significant injury, which was not observed after repeated exposure to liposomal formulations. Overall, liposomal formulations were considerably less toxic to hiPSC-CM than their free-drug counterparts. Clinical data will be needed to confirm findings for CPX-351.

Exposure to cytarabine causes side effects on adult development and physiology and induces intestinal damage via apoptosis in Drosophila.

Cytarabine (Ara-C) is a widely used drug in acute myeloid leukemia (AML). However, it faces serious challenges in clinical application due to serious side effects such as gastrointestinal disorders and neurologic toxicities. Until now, the mechanism of Ara-C-induced damage is not clear. Here, we used Drosophila melanogaster (fruit fly) as the in vivo model to explore the side effects and mechanism of Ara-C. Our results showed that Ara-C supplementation delayed larval development, reduced lifespan, impaired locomotor capacity, and increased susceptibility to stress response in adult flies. In addition, Ara-C led to the intestinal morphological damage and ROS accumulation in the guts. Moreover, administration of Ara-C promoted gene expressions of Toll pathway, IMD pathway, and apoptotic pathway in the guts. These findings raise the prospects of using Drosophila as in vivo model to rapidly assess chemotherapy-mediated toxicity and efficiently screen the protective drugs.

Exploring the possible mitoprotective and neuroprotective potency of thymoquinone, betanin, and vitamin D against cytarabine-induced mitochondrial impairment and neurotoxicity in rats' brain.

It has been suggested that cytarabine (Ara-C) induces toxicity via mitochondrial dysfunction and oxidative stress. Therefore, we hypothesized that mitochondrial protective agents and antioxidants can reduce cytarabine-induced neurotoxicity. For this purpose, 48 male Wistar rats were assigned into eight equal groups include control group, Ara-C (70 mg/kg, i.p.) group, Ara-C plus betanin (25 mg/kg, i.p.) group, Ara-C plus vitamin D (500 U/kg, i.p.) group, Ara-C plus thymoquinone (0.5 mg/kg, i.p.) group, betanin group, vitamin group, and thymoquinone group. The activity of acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), the concentrations of antioxidants (reduced glutathione and oxidized glutathione), oxidative stress (malondialdehyde) biomarkers, mitochondrial toxicity parameters as well as histopathological alteration in brain tissues were measured. Our results demonstrated that Ara-C exposure significantly declines the brain enzymes activity (AChE and BChE), levels of antioxidant biomarkers (GSH), and mitochondrial functions, but markedly elevate the levels of oxidative stress biomarkers (MDA) and mitochondrial toxicity. Almost all of the previously mentioned parameters (especially mitochondrial toxicity) were retrieved by betanin, vitamin D, and thymoquinone compared to Ara-C group. These findings conclusively indicate that betanin, vitamin D, and thymoquinone administration provide adequate protection against Ara-C-induced neurotoxicity through modulations of oxidative, antioxidant activities, and mitochondrial protective (mitoprotective) effects.

CD157 signaling promotes survival of acute myeloid leukemia cells and modulates sensitivity to cytarabine through regulation of anti-apoptotic Mcl-1.

CD157/BST-1 (a member of the ADP-ribosyl cyclase family) is expressed at variable levels in 97% of patients with acute myeloid leukemia (AML), and is currently under investigation as a target for antibody-based immunotherapy. We used peripheral blood and bone marrow samples from patients with AML to analyse the impact of CD157-directed antibodies in AML survival and in response to cytarabine (AraC) ex vivo. The study was extended to the U937, THP1 and OCI-AML3 AML cell lines of which we engineered CD157-low versions by shRNA knockdown. CD157-targeting antibodies enhanced survival, decreased apoptosis and reduced AraC toxicity in AML blasts and cell lines. CD157 signaling activated the PI3K/AKT/mTOR and MAPK/ERK pathways and increased expression of Mcl-1 and Bcl-XL anti-apoptotic proteins, while decreasing expression of Bax pro-apoptotic protein, thus preventing Caspase-3 activation. The primary CD157-mediated anti-apoptotic mechanism was Bak sequestration by Mcl-1. Indeed, the Mcl-1-specific inhibitor S63845 restored apoptosis by disrupting the interaction of Mcl-1 with Bim and Bak and significantly increased AraC toxicity in CD157-high but not in CD157-low AML cells. This study provides a new role for CD157 in AML cell survival, and indicates a potential role of CD157 as a predictive marker of response to therapies exploiting Mcl-1 pharmacological inhibition.

Primary mesenchymal stromal cells in co-culture with leukaemic HL-60 cells are sensitised to cytarabine-induced genotoxicity, while leukaemic cells are protected.

Tumour microenvironments are hallmarked in many cancer types. In haematological malignancies, bone marrow (BM) mesenchymal stromal cells (MSC) protect malignant cells from drug-induced cytotoxicity. However, less is known about malignant impact on supportive stroma. Notably, it is unknown whether these interactions alter long-term genotoxic damage in either direction. The nucleoside analogue cytarabine (ara-C), common in haematological therapies, remains the most effective agent for acute myeloid leukaemia, yet one-third of patients develop resistance. This study aimed to evaluate the bidirectional effect of MSC and malignant cell co-culture on ara-C genotoxicity modulation. Primary MSC, isolated from patient BM aspirates for haematological investigations, and malignant haematopoietic cells (leukaemic HL-60) were co-cultured using trans-well inserts, prior to treatment with physiological dose ara-C. Co-culture genotoxic effects were assessed by micronucleus and alkaline comet assays. Patient BM cells from chemotherapy-treated patients had reduced ex vivo survival (P = 0.0049) and increased genotoxicity (P = 0.3172) than untreated patients. It was shown for the first time that HL-60 were protected by MSC from ara-C-induced genotoxicity, with reduced MN incidence in co-culture as compared to mono-culture (P = 0.0068). Comet tail intensity also significantly increased in ara-C-treated MSC with HL-60 influence (P = 0.0308). MSC sensitisation to ara-C genotoxicity was also demonstrated following co-culture with HL60 (P = 0.0116), which showed significantly greater sensitisation when MSC-HL-60 co-cultures were exposed to ara-C (P = 0.0409). This study shows for the first time that malignant HSC and MSC bidirectionally modulate genotoxicity, providing grounding for future research identifying mechanisms of altered genotoxicity in leukaemic microenvironments. MSC retain long-term genotoxic and functional damage following chemotherapy exposure. Understanding the interactions perpetuating such damage may inform modifications to reduce therapy-related complications, such as secondary malignancies and BM failure.

Cytosine arabinoside induces phosphorylation of histone H2AX in hippocampal neurons via a noncanonical pathway.

Cytosine arabinoside (Ara-C), an anticancer drug, is known to inhibit DNA replication in mitotic cells. Ara-C is also considered to induce DNA damage, leading to neuronal cell death. To identify the mechanism by which Ara-C kills neurons, we assessed the levels of phosphorylated histone H2AX (γ-H2AX), a marker for DNA double-strand breaks (DSBs), in hippocampal neurons cultured for 48 h with Ara-C. There was a time-dependent increase in the percentage of cells accumulating γ-H2AX, but TUNEL staining did not indicate the formation of DSBs. The nuclear spread of γ-H2AX remained after Ara-C was withdrawn. These features of Ara-C-induced γ-H2AX formation were quite distinct from those observed in proliferating pheochromocytoma cells. Furthermore, Ara-C-induced γ-H2AX formation appeared to utilize cyclin-dependent kinase 7, but not ataxia telangiectasia mutated (ATM) or ATM and Rad3 related, which are well-known kinases in γ-H2AX formation. Taken together, our findings indicated that Ara-C stimulated γ-H2AX formation in neurons without DSB formation and utilization of canonical kinases, leading to neuronal cell death.

Alpha-lipoic acid ameliorates cytarabine-induced developmental anomalies in rat fetus.

Cytarabine (Ara-C) is a nucleoside analogue used in the treatment of cancers and viral infections. It has teratogenic potential and causes a variety of birth defects in fetuses. Alpha-lipoic acid (ALA) is a natural antioxidant offers protection against the developmental toxicity induced by drug- or toxicant-exposure or pathological conditions. This study was aimed at evaluating the protective effect of ALA against Ara-C induced developmental toxicity in rat fetus. Pregnant rats divided into five groups and received normal saline, ALA200 mg/kg, Ara-C12.5 mg/kg, Ara-C25 mg/kg and, Ara-C25 mg/kg plus ALA200 mg/kg respectively from gestational day (GD) 8 to GD14 and sacrificed on GD21. Ara-C treatment led to a significant and dose-dependent decrease in food intake, weight gain, placental weight, and an increase in oxidative stress in pregnant rats. Further, the in-utero exposure to Ara-C led to an increase in fetal mortality, resorptions, oxidative stress, external morphological anomalies and limb abnormalities, and impaired ossification. Co-administration of ALA resulted in amelioration of the footprints of Ara-C induced toxicity in pregnant rats as well as the fetus. These findings indicate that the ALA supplementation offers protection against developmental toxicity caused by Ara-C prenatal exposure in rats.

Expression of Fibroblast Growth Factor 4 in a Rat Model of Polydactyly of the Thumb Induced by Cytarabine.

BACKGROUND The aim of this study was to assess the expression and mechanisms of fibroblast growth factor 4 in polydactyly of the thumb induced by cytarabine. MATERIAL AND METHODS Rats were intraperitoneally injected with cytarabine at different gestation periods (12.5 days, 13.5 days, and 14.5 days) to establish a polydactyly of the thumb model. Then, the expression of FGF4 in polydactyly was studied by whole-mount in situ hybridization. We used hematoxylin & eosin stain and cartilage stain to investigate the development of the skeleton and tissues in the embryo. Pictures were taken to determine the general shape of the deformity, then X-rays were taken to detect bone distortion of the rats born with a congenital malformation. RESULTS In the experimental group (11.5 days, 12.5 days, 13.5 days, and 14.5 days), whole-mount in situ hybridization showed that the FGF4 expression at the tip of the embryonic limb bud was significantly increased compared with the control group and FGF4 was distributed in a wider range and lasted longer than in the control group (P<0.01). HE staining and cartilage staining showed that there was an extra metacarpal bone and a phalanx in the rats with polydactyly of the thumb (P<0.01). Images of the deformed limbs showed polydactyly and syndactyly of the thumb in the rats. Further X-ray examination revealed 1 extra metacarpal bone and 1 extra phalanx. CONCLUSIONS Cytarabine can induce polydactyly and syndactyly of the thumb in rats. In this process, cytarabine can induce the expression of FGF4 on the tip of the embryonic limb bud, which further leads to abnormal development of the embryonic limb bud and eventually causes a congenital deformity.

Trifluoperazine an Antipsychotic Drug and Inhibitor of Mitochondrial Permeability Transition Protects Cytarabine and Ifosfamide-Induced Neurotoxicity.

The link between Ca2+ dysregulation, mitochondria damages, oxidative stress and cellular derangement is particularly evident in neurotoxicity induced by chemotherapeutic agents. In the current study, we investigated effects of trifluoperazine (TFP) as an inhibitor of calmodulin against the cytotoxicity induced by cytarabine (Ara-C) and Ifosfamide (IFOS) on isolated rat neurons and also the mechanisms involved in this toxicity. Isolated rat neurons were pretreated with TFP (100 µM) for 5 min at 37°C, then Ara-C (226 µM) and IFOS (290 µM) were added in separate experiments. After 3 h, the cytotoxicity, reactive oxygen species (ROS), lysosomal membrane destabilization, mitochondrial membrane potential (MMP), lipid peroxidation (LP), glutathione (GSH) and glutathione disulfide (GSSG) levels were measured. Ara-C and IFOS treatments caused a significant decrease in cellular viability, which was accompanied by ROS generation, GSSG/GSH ratio, lipid peroxidation and lysosomal and mitochondrial damages. On the other hand, TFP (100 µM) pre-treatment attenuated Ara-C and IFOS -induced decrease in cell viability. In addition, TFP (100 µM) pre-treatment significantly protected against Ara-C and IFOS -induced increase in ROS generation, lysosomal and mitochondrial damages, lipid peroxidation levels and decrease in GSH/GSSG ratio. Our data provided insights into the mechanism of protection by TFP against Ara-C and IFOS neurotoxicity, which is related, to neuronal ROS formation and mitochondrial damages.

The impact of overweight on renal toxicity in patients treated with dexamethasone, high-dose cytarabine, and cisplatin.

The combination of dexamethasone, high-dose cytarabine, and cisplatin (DHAP) is used as salvage chemotherapy for relapsed or refractory lymphoma. It includes the administration of cisplatin in a single dose of 100 mg/m2, and renal toxicity is a common adverse event. In this study, we retrospectively analyzed the risk factors for renal toxicity (≥ grade 2) in 74 patients who received DHAP as salvage chemotherapy. Regarding maximal renal toxicities, 38 (51.4%), 6 (8.1%), and 1 (1.4%) patients had grade 2, 3, and 4 toxicities, respectively. Multivariate analyses revealed that overweight (body mass index ≥ 25) was an independent predictive factor for renal toxicity of ≥ grade 2 (odds ratio [OR] 4.08, P = 0.032). A subgroup analysis for patients with diffuse large B cell lymphoma treated with DHAP as second-line therapy (n = 44) confirmed that overweight was an independent risk factor (OR 5.28, P = 0.049). In conclusion, we demonstrated that overweight was an independent risk factor for renal toxicity of ≥ grade 2 in patients who received DHAP. Further clinical studies will be needed to identify a method to decrease renal toxicities after the administration of cisplatin.

Early glioma is associated with abnormal electrical events in cortical cultures.

The prodromal stages of some neurological diseases have a distinct electrical profile which can potentially be leveraged for early diagnosis, predicting disease recurrence, monitoring of disease progression, and better understanding of the disease pathology. Gliomas are tumors that originate from glial cells present in the brain and spinal cord. Healthy glial cells support normal neuronal function and play an important role in modulating the regular electrical activity of neurons. However, gliomas can disrupt the normal electrical dynamics of the brain. Though experimental and clinical studies suggest that glioma and injury to glial cells disrupt electrical dynamics of the brain, whether these disruptions are present during the earliest stages of glioma and glial injury are unclear. The primary aim of this study is to investigate the effect of early in vitro glial pathology (glioma and glial injury in specific) on neuronal electrical activity. In particular, we investigated the effect of glial pathology on neural synchronization: an important phenomenon that underlies several central neurophysiological processes (ScienceDirect, 2018 ). We used two in vitro disease samples: (a) a sample in which cortical cultures were treated with anti-mitotic agents that deplete glial cells and (b) a glioma sample in which healthy cortical cells were cultured with CRL-2303 (an aggressive glioma cell line). Healthy cortical culture samples were used as controls. Cultures were established over a glass dish embedded with microelectrodes that permits simultaneous measurement of extracellular electrical activity from multiple sites of the culture. We observed that healthy cortical cultures produce spontaneous and synchronized oscillations which were attenuated in the absence of glial cells. The presence of glioma was associated with the emergence of two types of "abnormal electrical activity" each with distinct amplitude and frequency profile. Our results indicate that even early stages of glioma and glial injury are associated with distinct changes in neuronal electrical activity. Graphical abstract.

Evaluation of the impact of single-nucleotide polymorphisms on treatment response, survival and toxicity with cytarabine and anthracyclines in patients with acute myeloid leukaemia: a systematic review protocol.

INTRODUCTION: Acute myeloid leukaemia is the most common type of acute leukaemia in the world. Thus, the study of genetic alterations, such as single-nucleotide polymorphisms (SNPs), has contributed to a better understanding of the mechanisms underlying leukaemogenesis, to improve the prognosis and to increase the survival of these patients. However, there is no synthesis of evidence in the literature evaluating the quality of evidence and the risk of bias in the studies such that the results can be translated. Thus, this systematic review protocol aims to assess the impact of SNPs on genes involved in the metabolism of cytarabine and anthracyclines with respect to survival, treatment response and toxicity in patients with AML. METHODS: This systematic review protocol is based on PRISMA guidelines and includes searches in six electronic databases, contact with authors, repositories of clinical trials, and cancer research. Studies published in peer-reviewed journals will be included if they meet the eligibility criteria: (a) samples composed of individuals of any age, of both sexes, with a diagnosis of AML, regardless of the time of diagnosis of disease; (b) participants who have undergone or are undergoing cytarabine- and anthracycline-associated chemotherapy or cytarabine-only chemotherapy; and (c) in vivo studies. Studies that include patients with promyelocytic leukaemia (Fab type 3) will be excluded because this disease has different treatment. The process of study selection, data extraction, and evaluation/synthesis will be performed in duplicate. Assessment of methodological quality and risk of bias will be performed using the Cochrane Risk of Bias Tool for randomized clinical studies and the Downs-Black Checklist for cohort and case-control studies. The synthesis of evidence will include the level of evidence based on the GRADE protocol. A meta-analysis of the association between SNPs and outcomes may be performed based on Cochrane guidelines. DISCUSSION: It is expected that clinical decisions for AML patients will consider evidence-based practices to contribute to better patient management. In this way, we will be able to define how to treat patients with AML to improve their survival and quality of life. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018100750.

Toward Predicting Acute Myeloid Leukemia Patient Response to 7 + 3 Induction Chemotherapy via Diagnostic Microdosing.

Acute myeloid leukemia (AML) is a rare yet deadly cancer of the blood and bone marrow. Presently, induction chemotherapy with the DNA damaging drugs cytarabine (ARA-C) and idarubicin (IDA), known as 7 + 3, is the standard of care for most AML patients. However, 7 + 3 is a relatively ineffective therapy, particularly in older patients, and has serious therapy-related toxicities. Therefore, a diagnostic test to predict which patients will respond to 7 + 3 is a critical unmet medical need. We hypothesize that a threshold level of therapy-induced 7 + 3 drug-DNA adducts determines cytotoxicity and clinical response. We further hypothesize that in vitro exposure of AML cells to nontoxic diagnostic microdoses enables prediction of the ability of AML cells to achieve that threshold during treatment. Our test involves dosing cells with very low levels of 14C-labeled drug followed by DNA isolation and quantification of drug-DNA adducts via accelerator mass spectrometry. Here, we have shown proof of principle by correlating ARA-C- and DOX-DNA adduct levels with cellular IC50 values of paired sensitive and resistant cancer cell lines and AML cell lines. Moreover, we have completed a pilot retrospective trial of diagnostic microdosing for 10 viably cryopreserved primary AML samples and observed higher ARA-C- and DOX-DNA adducts in the 7 + 3 responders than nonresponders. These initial results suggest that diagnostic microdosing may be a feasible and useful test for predicting patient response to 7 + 3 induction chemotherapy, leading to improved outcomes for AML patients and reduced treatment-related morbidity and mortality.

Protective effect of ß-D-glucan and glutamine on the genomic instability induced by Cytarabine/Ara-C in BALB/c mice.

Prophylactic antibiotics and growth promoters have been substituted, mainly for livestock, by immunomodulators and intestinal health promoters - such as ß-D-glucans and glutamine. The aim of this study was to verify the beneficial effects of ß-D-glucans and glutamine against Cytarabine/Ara-C, evaluating the DNA damage in leukocytes, the leukogram, and the mitotic index of intestinal crypts cells. Balb/C mice received treatment with ß-D-glucan (80 mg/Kg), glutamine (150 mg/Kg), or both, for 21 days. On the last two days of this period, Ara-C was administered (1.8 mg/animal) by intraperitoneal injection every 12 h. The animals submitted to the treatment with Ara-C presented the highest genotoxic index, a significant leukopenia, and a decrease in the mitotic index of the intestinal crypts cells. Treatment with ß-D-glucan protected the leukocytes against DNA fragmentation induced by Ara-C. Glutamine alone promoted maintenance of the mitotic index and, in association with ß-Dglucan, reduced leukopenia. Thus, the use of ß-D-glucan and glutamine proved to be beneficial to intestinal tropism. This can happen once the damage to the genetic material, prevented by the treatments with ß-D-glucan and glutamine, can result in genotoxicity. Not only this, but it might be capable of turning into a mutagenesis, with consequential physiopathological alterations.

Neurotoxicity of cytarabine (Ara-C) in dorsal root ganglion neurons originates from impediment of mtDNA synthesis and compromise of mitochondrial function.

Peripheral Nervous System (PNS) neurotoxicity caused by cancer drugs hinders attainment of chemotherapy goals. Due to leakiness of the blood nerve barrier, circulating chemotherapeutic drugs reach PNS neurons and adversely affect their function. Chemotherapeutic drugs are designed to target dividing cancer cells and mechanisms underlying their toxicity in postmitotic neurons remain to be fully clarified. The objective of this work was to elucidate progression of events triggered by antimitotic drugs in postmitotic neurons. For proof of mechanism study, we chose cytarabine (ara-C), an antimetabolite used in treatment of hematological cancers. Ara-C is a cytosine analog that terminates DNA synthesis. To investigate how ara-C affects postmitotic neurons, which replicate mitochondrial but not genomic DNA, we adapted a model of Dorsal Root Ganglion (DRG) neurons. We showed that DNA polymerase γ, which is responsible for mtDNA synthesis, is inhibited by ara-C and that sublethal ara-C exposure of DRG neurons leads to reduction in mtDNA content, ROS generation, oxidative mtDNA damage formation, compromised mitochondrial respiration and diminution of NADPH and GSH stores, as well as, activation of the DNA damage response. Hence, it is plausible that in ara-C exposed DRG neurons, ROS amplified by the high mitochondrial content shifts from physiologic to pathologic levels signaling stress to the nucleus. Combined, the findings suggest that ara-C neurotoxicity in DRG neurons originates in mitochondria and that continuous mtDNA synthesis and reliance on oxidative phosphorylation for energy needs sensitize the highly metabolic neurons to injury by mtDNA synthesis terminating cancer drugs.

CDA as a predictive marker for life-threatening toxicities in patients with AML treated with cytarabine.

Cytarabine (Ara-C) is the backbone of acute myeloid leukemia (AML) chemotherapy. Little is known about possible risk factors predictive for the frequent (ie, up to 16%) life-threatening or lethal toxicities caused by Ara-C. Ara-C is detoxified in the liver by a single enzyme, cytidine deaminase (CDA), coded by a gene known to be highly polymorphic. In this proof-of-concept study, we particularly investigated the role of the CDA poor metabolizer (PM) phenotype in Ara-C toxicities. CDA phenotyping (measurement of CDA residual activity in serum) and genotyping (search for the CDA*2 allelic variant) were performed in 58 adult patients with AML treated with the standard 7+3 (Ara-C + anthracyclines) protocol. Statistically significantly lower CDA activity was observed in patients experiencing severe/lethal toxicities as compared with patients who did not (1.5 ± 0.7 U/mg vs 3.95 ± 3.1 U/mg; Student t test P < .001). Subsequent receiver operating characteristic analysis identified a threshold in CDA activity (ie, 2 U/mg) associated with PM syndrome and increased risk of developing severe toxicities. Five percent of patients experienced lethal toxicities, all displaying CDA PM status (1.3 ± 0.5 U/mg). In terms of efficacy, a trend toward higher response rates and longer progression-free survival and overall survival were observed in patients with low CDA activity. Taken together, the results of this study strongly suggest that CDA is a predictive marker of life-threatening toxicities in patients with AML receiving induction therapy with standard Ara-C.

Liposomal Cytarabine Induces Less Neurocognitive Dysfunction Than Intrathecal Methotrexate in an Animal Model.

Liposomal cytarabine is currently being tested clinically as an alternative to intrathecal (IT) methotrexate (MTX) for preventing relapse within the central nervous system among patients with acute lymphoblastic leukemia. To compare the toxicity and cognitive deficits caused by IT MTX versus liposomal cytarabine, juvenile Long Evans rats were treated with IT injections of MTX 1 mg/kg×4 doses over 8 days, or liposomal cytarabine 0.8 mg once. Mean concentrations of free cytarabine in cerebrospinal fluid remained above the cytotoxic threshold of 0.4 µM for 2 weeks after dosing. Animals treated with liposomal cytarabine exhibited normal recognition and spatial memory 4 weeks after injection. In contrast, exposure to IT MTX led to impaired cognitive function. In addition, mean hematocrit on day 11 was significantly lower in the MTX-treated animals (30.8%; 95% confidence interval, 27.0%-34.7%; n=6) compared with that in the liposomal cytarabine-treated animals (39.5%; 95% confidence interval, 38.4%-40.6%; n=6; P<0.0001). Our data suggest that liposomal cytarabine induces fewer neurocognitive deficits and less acute hematologic toxicity compared with IT MTX. Liposomal cytarabine may therefore have therapeutic advantages over IT MTX, if it is equally effective in preventing relapse.