Sapacitabine is an orally bioavailable prodrug of the nucleoside analog 2'-C-cyano-2'-deoxy-1-β-D-arabino-pentofuranosylcytosine (CNDAC). Both the prodrug and active metabolite are in clinical trials for hematologic malignancies and/or solid tumors. CNDAC has a unique mechanism of action: after incorporation into DNA, it induces single-strand breaks (SSBs) that are converted into double-strand breaks (DSBs) when cells go through a second S phase. In our previous studies, we demonstrated that CNDAC-induced SSBs can be repaired by the transcription-coupled nucleotide excision repair pathway, whereas lethal DSBs are mainly repaired through homologous recombination. In the current work, we used clonogenic assays to compare the DNA damage repair mechanism of CNDAC with two other deoxycytidine analogs: cytarabine, which is used in hematologic malignacies, and gemcitabine, which shows activity in solid tumors. Deficiency in two Rad51 paralogs, Rad51D and XRCC3, greatly sensitized cells to CNDAC, but not to cytarabine or gemcitabine, indicating that homologous recombination is not a major mechanism for repairing damage caused by the latter two analogs. This study further suggests clinical activity and application of sapacitabine that is distinct from that of cytarabine or gemcitabine.
Animals ; Antimetabolites, Antineoplastic ; pharmacology ; Arabinonucleosides ; pharmacology ; CHO Cells ; Cricetinae ; Cricetulus ; Cytarabine ; analogs & derivatives ; pharmacology ; Cytosine ; analogs & derivatives ; pharmacology ; DNA Breaks, Double-Stranded ; drug effects ; DNA Repair ; drug effects ; DNA-Binding Proteins ; deficiency ; Deoxycytidine ; analogs & derivatives ; pharmacology ; Homologous Recombination ; genetics ; Inhibitory Concentration 50 ; Prodrugs

To explore the mechanism of autophagic death of acute myelocytic leukemia cell U937 induced by clofarabine, the MTT bioassay was used to analyze the growth inhibitory effect and half inhibition concentration on U937 incubated in vitro with different concentrations of clofarabine for 24 and 48 hours, and the flow cytometry was used to detect the autophagy rate of U937. The expression of Beclin 1 in U937 treated by clofarabine for 48h was measured by Western blot. The results indicated that when U937 cells were treated with 0.01 µmol/L and 0.15 µmol/L clofarabine for 48 hours, the proliferation inhibition rate was 46.92% ± 4.24% and 86.10% ± 1.16%, and the half inhibition concentration of clofarabine was 0.022 µmol/L. With 0.01 µmol/L and 0.1 µmol/L clofarabine on U937 for 48 hours, the autophagy rate was 11.0033% ± 1.4387% and 59.4133% ± 3.5409%, and increased in dose-dependent manner (r = 0.99). Meanwhile the Beclin 1 was upregulated along with increase of clofarabine concentration, as compared with control group, the difference was statistically significant (P < 0.05). It is concluded that the different concentrations of clofarabine can significantly inhibit the proliferation of U937 in dose-dependent manner, and the mechanism of autophagic cell death in U937 may be associated with the upregulation of Beclin 1 expression.
Adenine Nucleotides ; pharmacology ; Apoptosis ; drug effects ; Apoptosis Regulatory Proteins ; metabolism ; Arabinonucleosides ; pharmacology ; Autophagy ; drug effects ; Beclin-1 ; Cell Proliferation ; drug effects ; Humans ; Membrane Proteins ; metabolism ; U937 Cells

The aim of this study was to observe the effect of clofarabine on proliferation of NB4 cells and its possible mechanism. MTT method was used to detect proliferation of NB4 cells treated with clofarabine 0.01 - 0.1 µmol/L for 48 h. The treated with clofarabine 0.01 - 0.1 µmol/L for 24 h, apoptosis rate and Bcl-2 expression of NB4 cells were measured by flow cytometry and Western blot respectively. The results showed that clofarabine inhibited proliferation of NB4 cells in a concentration-depended manner (r = 0.78). After treated with clofarabine for 24 h, apoptosis rate of NB4 cells increased and Bcl-2 expression in NB4 cells decreased obviously (P < 0.05). It is concluded that clofarabine inhibits proliferation of NB4 cells, which may be related with the down-regulation of Bcl-2 and induction of apoptosis.
Adenine Nucleotides ; pharmacology ; Apoptosis ; drug effects ; Arabinonucleosides ; pharmacology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Down-Regulation ; Humans ; Leukemia, Promyelocytic, Acute ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism

OBJECTIVETo explore the efficacy and adverse effects of clofarabine for relapsed/refractory acute lymphoblastic leukemia in children.

METHODSTwenty-six pediatric patients with relapsed/refractory acute lymphoblastic leukemia were treated with clofarabine. There were 22 males and 4 females, with a mean age of 9.5 years (ranging from 4 to 17 years). They received clofarabine 52 mg/m2 intravenously over 2 hours daily for 5 days. Thirteen patients received two cycles and one patient received three cycles.

RESULTSIn the first cycle of clofarabine, complete remission was obtained in 11 children (42%) and partial remission was obtained in 7 children (27%). Eight children (31%) were considered unresponsive. In the second cycle, 11 (85%) of the 13 children obtained complete remission, 1 (8%) partial remission and 1 (8%) was unresponsive. One child received three cycles and obtained complete remission in each cycle. The common adverse events were myelosuppression, infection, liver dysfunction and gastrointestinal adverse reactions. There were no chemotherapy-related deaths.

CONCLUSIONSClofarabine is effective in the treatment of children with relapsed/refractory acute lymphoblastic leukemia and its adverse effects can be tolerated. Clofarabine could be a promising new treatment for relapsed/refractory acute lymphoblastic leukemia.

Adenine Nucleotides ; adverse effects ; therapeutic use ; Adolescent ; Antineoplastic Agents ; adverse effects ; therapeutic use ; Arabinonucleosides ; adverse effects ; therapeutic use ; Child ; Child, Preschool ; Female ; Follow-Up Studies ; Humans ; Infant ; Male ; Precursor Cell Lymphoblastic Leukemia-Lymphoma ; drug therapy ; Recurrence

Mcl-1 and Bcl-xL, key anti-apoptotic proteins of the Bcl-2 family, have attracted attention as important molecules in the cell survival and drug resistance. In this study, we investigated whether inhibition of Bcl-xL influences cell growth and apoptosis against simultaneous treatment of resveratrol and clofarabine in the human malignant mesothelioma H-2452 cells. Resveratrol and clofarabine decreased Mcl-1 protein levels but had little effect on Bcl-xL levels. In the presence of two compounds, any detectable change in the Mcl-1 mRNA levels was not observed in RT-PCR analysis, whereas pretreatment with the proteasome inhibitor MG132 led to its accumulation to levels far above basal levels. The knockdown of Bcl-xL inhibited cell proliferation with cell accumulation at G2/M phase and the appearance of sub-G0/G1 peak in DNA flow cytometric assay. The suppression of cell growth was accompanied by an increase in the caspase-3/7 activity with the resultant cleavages of procaspase-3 and its substrate poly (ADP-ribose) polymerase, and increased percentage of apoptotic propensities in annexin V binding assay. Collectively, our data represent that the efficacy of resveratrol and clofarabine for apoptosis induction was substantially enhanced by Bcl-xL-lowering strategy in which the simultaneous targeting of Mcl-1 and Bcl-xL could be a more effective strategy for treating malignant mesothelioma.
Adenine Nucleotides/*pharmacology ; Antimetabolites, Antineoplastic/*pharmacology ; Apoptosis/*drug effects ; Arabinonucleosides/*pharmacology ; Caspase 3/metabolism ; Caspase 7/metabolism ; Cell Line, Tumor ; Cell Proliferation/drug effects ; G2 Phase Cell Cycle Checkpoints/drug effects ; Gene Knockdown Techniques ; Humans ; Leupeptins/pharmacology ; Lung Neoplasms/metabolism/pathology ; M Phase Cell Cycle Checkpoints/drug effects ; Mesothelioma/metabolism/pathology ; Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors/genetics/metabolism ; RNA Interference ; RNA, Messenger/metabolism ; RNA, Small Interfering/metabolism ; Stilbenes/*pharmacology ; bcl-X Protein/antagonists & inhibitors/*genetics/*metabolism

BACKGROUND/AIMS: The clinical effects of clevudine have been reported in patients with chronic hepatitis B virus infections (CHIs). In this investigation, we assessed whether clevudine induced biochemical and virological improvements in hepatocellular carcinoma (HCC) patients with CHI. METHODS: Fifty-four patients who received 30 mg clevudine for more than 24 weeks between 2007 and 2009 at the National Cancer Center Hospital, Korea, were enrolled. Among these cases, 39 had HCC (CHI/HCC group) and 15 did not (CHI group). RESULTS: In relation to the CHI group, the CHI/HCC group was older (55.5 years.) and had a higher liver cirrhosis rate (79.5%) (p<0.05). Median changes in serum hepatitis B virus (HBV) DNA levels from baseline at weeks 12, 24, and 36 of treatment in the CHI/HCC group were not significantly different from those of the CHI group (-2.3, -2.7, -2.6 vs -1.7, -1.8, -2.4, respectively). HBV DNA <2,000 copies/mL was achieved in 76.5% of the CHI/HCC group at 24 weeks. Rates of ALT normalization in the CHI/HCC and CHI groups were 62.5% and 66.7%, respectively (p>0.05). Liver function was preserved with clevudine treatment in patients displaying response or stable disease under anti-cancer therapy. Four patients (7.4%) developed viral resistance during clevudine therapy. Among these, one was naive, and three had previously received antiviral therapy. One CHI/HCC patient (1.9%) discontinued clevudine treatment due to symptomatic myopathy. CONCLUSIONS: Our findings clearly indicate that clevudine has comparable antiviral and biochemical effects in patients with CHI and with CHI/HCC and preserves the underlying liver function in HBV-related HCC patients.
Arabinofuranosyluracil ; Carcinoma, Hepatocellular ; DNA ; Hepatitis B virus ; Hepatitis B, Chronic ; Hepatitis, Chronic ; Humans ; Korea ; Liver ; Liver Cirrhosis ; Viruses

BACKGROUND: Clevudine (Revovir(R)) is a recently introduced antiviral drug, and clinical trials have demonstrated its potent, sustained antiviral activity without specific adverse events. However, several studies have found severe myopathy during clevudine therapy. Our study aimed to summarize the clinical and pathological features of clevudine-induced myopathy. METHODS: We analyzed the demographic data, clinical features, and pathologic findings of 18 consecutive hepatitis-B patients who developed skeletal myopathy during clevudine therapy. RESULTS: The 18 patients comprised 11 women and 7 men aged 48.2+/-14.0 years (mean+/-standard deviation; range 28-74 years). Each of the 18 patients was treated with clevudine for at least 5 months (range 5-20 months) before the development of symptoms. In all patients the main symptom was proximal muscular weakness that progressed slowly over several months. Elevated creatine kinase and myopathic patterns on electromyography were found. Muscle biopsies revealed severe myonecrosis associated with numerous ragged red fibers and cytochrome-c-oxidase-negative fibers, mitochondrial proliferation, and predominant type-II fiber atrophy. The muscle weakness gradually improved within 20 weeks after discontinuation of clevudine. CONCLUSIONS: Clevudine therapy can induce myopathy associated with mitochondrial toxicity. Careful clinical and laboratory monitoring of the skeletal muscle dysfunction is required in patients receiving clevudine therapy.
Aged ; Arabinofuranosyluracil ; Atrophy ; Biopsy ; Creatine Kinase ; Electromyography ; Female ; Hepatitis ; Humans ; Male ; Muscle Weakness ; Muscle, Skeletal ; Muscles ; Muscular Diseases

Several studies have documented that various agents can induce diabetes mellitus, such as steroids, thiazides, anti-psychotic agents, and anti-viral agents. Many antiviral agents are also reported to impair insulin resistance and induce diabetes mellitus in patients infected with human immunodeficiency virus (HIV). However, there are no reports of diabetes mellitus induced by clevudine, one of the antiviral agents used to treat chronic hepatitis B virus (HBV) infection. We report a case of diabetes mellitus induced by clevudine in a patient with chronic hepatitis B.
Antiviral Agents ; Arabinofuranosyluracil ; Diabetes Mellitus ; Hepatitis B, Chronic ; Hepatitis, Chronic ; HIV ; Humans ; Insulin Resistance ; Steroids ; Thiazides ; Viruses

Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Cytarabine ; therapeutic use ; Granulocyte Colony-Stimulating Factor ; therapeutic use ; Humans ; Leukemia, Myeloid, Acute ; pathology ; therapy ; Vidarabine ; analogs & derivatives ; therapeutic use

The aim of study was to evaluate the clinical efficacy and toxicity of fludarabine combined with cytarabine (FA) regimen in the treatment of patients with refractory and/or relapsed acute myeloid leukemia (AML). Nineteen cases with refractory/relapsed AML were treated with FA regimen in which fludarabine phosphate 25 mg/(m(2) x d), d1-5; cytarabine (Ara-C) 2 g/(m(2) x d), d1-5. Another 20 cases were treated with salvage chemotherapy (MAE regimen: mitoxantrone, Ara-C and etoposide or DAE regimen: daunorubicin, Ara-C and etoposide). All patients received at least 2 cycles chemotherapy. The results showed that 9 patients (47%) in FA regimen group achieved complete remission (CR), 8 cases (42%) obtained partial remission (PR), the clinical efficacy was superior to that of the MAE or DAE regimens (p < 0.05). Major toxicity of FA regimen was myelosuppression. Grade IV hematologic toxicity occurred in all patients received FA regimen. Nonhematologic complications consisted of gastrointestinal side effects, mucositis, liver toxicity, which were mild to moderate and could be alleviated with supportive therapy. In conclusion, FA regimen is an effective regimen for treatment of refractory and relapsed AML.
Adult ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Cytarabine ; administration & dosage ; Female ; Humans ; Leukemia, Myeloid, Acute ; drug therapy ; Male ; Middle Aged ; Recurrence ; Vidarabine ; administration & dosage ; analogs & derivatives