Pharmacokinetics of a single intravenous dose of marbofloxacin in adult donkeys

Six donkeys each received 2 mg/kg marbofloxacin as a 10 per cent aqueous solution administered intravenously. Principal pharmacokinetic parameters were determined and two efficacy indices were computed by using pharmacokinetic parameters and selected mic90 values of marbofloxacin against pathogenic equine strains to predict the efficacy of the drug at this dose. The pharmacokinetics of marbofloxacin in donkeys was characterised by a large mean volume of distribution at a steady state (1.15 [0.09] l/kg) and a long mean (sd) elimination half-life of 9.24 (1.96) hours. It was also characterised by a relatively slow total body clearance of 0.10 (0.02) l/kg/hour, slower than in horses. Using mic90 values of marbofloxacin against pathogenic equine strains with a daily dose of 2 mg/kg, appropriate values of efficacy indicators were obtained only for Enterobacteriaceae. Daily intravenous doses of 0.33, 2.62 and 20 mg/kg were calculated for evaluation in clinical trials of infections due to Enterobacteriaceae, Staphylococcus aureus and Streptococci, respectively.

De-regulation of common housekeeping genes in hepatocellular carcinoma

Background

Tumorigenesis is associated with changes in gene expression and involves many pathways. Dysregulated genes include "housekeeping" genes that are often used for normalization for quantitative real-time RT-PCR (qPCR), which may lead to unreliable results. This study assessed eight stages of hepatitis C virus (HCV) induced hepatocellular carcinoma (HCC) to search for appropriate genes for normalization.

Results

Gene expression profiles using microarrays revealed differential expression of most "housekeeping" genes during the course of HCV-HCC, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta-actin (ACTB), genes frequently used for normalization. QPCR reactions confirmed the regulation of these genes. Using them for normalization had strong effects on the extent of differential expressed genes, leading to misinterpretation of the results.

Conclusion

As shown here in the case of HCV-induced HCC, the most constantly expressed gene is the arginine/serine-rich splicing factor 4 (SFRS4). The utilization of at least two genes for normalization is robust and advantageous, because they can compensate for slight differences of their expression when not co-regulated. The combination of ribosomal protein large 41 (RPL41) and SFRS4 used for normalization led to very similar results as SFRS4 alone and is a very good choice for reference in this disease as shown on four differentially expressed genes.

Genome-wide molecular profiles of HCV-induced dysplasia and hepatocellular carcinoma

Although HCC is the third-leading cause of cancer-related deaths worldwide, there is only an elemental understanding of its molecular pathogenesis. In western countries, HCV infection is the main etiology underlying this cancer's accelerating incidence. To characterize the molecular events of the hepatocarcinogenic process, and to identify new biomarkers for early HCC, the gene expression profiles of 75 tissue samples were analyzed representing the stepwise carcinogenic process from preneoplastic lesions (cirrhosis and dysplasia) to HCC, including 4 neoplastic stages (very early HCC to metastatic tumors) from patients with HCV infection. We identified gene signatures that accurately reflect the pathological progression of disease at each stage. Eight genes distinguish between control and cirrhosis, 24 between cirrhosis and dysplasia, 93 between dysplasia and early HCC, and 9 between early and advanced HCC. Using quantitative real-time reverse-transcription PCR, we validated several novel molecular tissue markers for early HCC diagnosis, specifically induction of abnormal spindle-like, microcephaly-associated protein, hyaluronan-mediated motility receptor, primase 1, erythropoietin, and neuregulin 1. In addition, pathway analysis revealed dysregulation of the Notch and Toll-like receptor pathways in cirrhosis, followed by deregulation of several components of the Jak/STAT pathway in early carcinogenesis, then upregulation of genes involved in DNA replication and repair and cell cycle in late cancerous stages.

CONCLUSION

These findings provide a comprehensive molecular portrait of genomic changes in progressive HCV-related HCC.

Metoclopramide modifies oral cephalexin pharmacokinetics in dogs

The purpose of this study was to investigate whether previous administration of metoclopramide affects cephalexin pharmacokinetics after its oral administration in dogs as well as whether these changes impair its predicted clinical efficacy. Six healthy beagle dogs were included in this study. Oral 25 mg/kg cephalexin monohydrate and intravenous 0.5 mg/kg metoclopramide HCl single doses were administered. Each dog received cephalexin or cephalexin following metoclopramide, with a 2-week washout period. Plasma concentrations of cephalexin were determined by microbiological assay. Cephalexin peak plasma concentration and area under the curve from 0 to infinity significantly increased from 18.77+/-2.8 microg/mL and 82.65+/-10.4 microg.h/mL to 21.88+/-0.8 microg/mL and 113.10+/-20.9 microg.h/mL, respectively, after pretreatment with metoclopramide. No differences between treatments were found for other pharmacokinetic parameters. Pharmacokinetic/pharmacodynamic indices calculated for highly susceptible staphylococci were similar for both experiences. Metoclopramide pretreatment may have increased cephalexin absorption by affecting its delivery to the intestine, and/or enhancing intestinal transporter PEPT1 function. Neither difference in the efficacy of cephalexin nor an increase in toxicity is expected as a result of this modification. Consequently, no dose adjustment is required in cephalexin-treated patients pretreated with metoclopramide.

Combination of cytotoxic-differentiation therapy with 5-fluorouracil and phenylbutyrate in patients with advanced colorectal cancer

BACKGROUND

Phenylbutyrate (PB), a histone deacetylase inhibitor (HDACi), has been shown in laboratory studies to potentiate growth inhibition by 5-fluorouracil (FUra) of human colon carcinoma cells.

PATIENTS AND METHODS

Phase I trial of FUra (24-hour continuous intravenous infusion (CIV)) with dose escalation (2 g/m2 to 2.3 g/m2), in combination with PB (120 hour CIV at fixed dose 410 mg/kg/d x 5), repeated weekly, in patients with advanced colorectal cancer.

RESULTS

Nine patients with metastatic colorectal cancer were treated, 8 of whom were evaluable for toxicity. Toxicities were dose-dependent, reversible and included somnolence, fatigue, confusion, hearing loss, triglyceridemia and hyperuricema. Three out of 4 patients who completed at least 8 weeks of treatment had stable disease (SD) lasting 12+, 25 and 54 weeks (2 out of the 3 patients with SD have had multiple prior chemotherapy regimens).

CONCLUSION

Weekly infusions of FUra followed by PB were fairly well tolerated with disease stabilization in 3/4 (75%) of patients. This is the first report to demonstrate the feasibility of combining a cytotoxic agent with a HDACi as a cancer treatment.

The design of selective and non-selective combination therapy for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is an unique subtype of acute myeloid leukemia typically carrying a specific reciprocal chromosome translocation, t(15;17), leading to the expression of a leukemia-generating fusion protein, PML-RARalpha. APL patients are responsive to APL-selective reagents such as all-trans retinoic acid (ATRA) or arsenic trioxide and non-selective cytotoxic chemotherapy. Nearly all de novo APL patients undergo clinical remission when treated with ATRA plus chemotherapy or with the combinational selective therapy, ATRA plus As2O3. Combining ATRA with As2O3 as an induction followed by chemotherapy consolidation results in more profound clinical remissions compared to treatment with any agent alone or any of the other possible combinations. The mechanism of action of each of these agents differs. ATRA induces APL cell differentiation and PML-RARalpha proteolysis. As2O3 induces APL cell partial differentiation, PML-RARalpha proteolysis, and apoptosis. Chemotherapy, mainly using anthracyclines, induces APL cell death. The combined effects of selective APL therapy (ATRA and As2O3) and/or non-selective chemotherapy in APL cells in vitro and their mechanisms in relation to clinical protocol design are discussed.

Pharmacokinetics of erythromycin in nonlactating and lactating goats after intravenous and intramuscular administration

The objectives of this work were to compare the pharmacokinetics of erythromycin administered by the intramuscular (i.m.) and intravenous (i.v.) routes between nonlactating and lactating goats and to determine the passage of the drug from blood into milk. Six nonpregnant, nonlactating and six lactating goats received erythromycin by the i.m. (15 mg/kg) and the i.v. (10 mg/kg) routes of administration. Milk and blood samples were collected at predetermined times. Erythromycin concentrations were determined by microbiological assay. Results are reported as mean +/- SD. Comparison of the pharmacokinetic profiles between nonlactating and lactating animals after i.v. administration indicated that significant differences were found in the mean body clearance (8.38 +/- 1.45 vs. 3.77 +/- 0.83 mL/kg x h respectively), mean residence time (0.96 +/- 0.20 vs. 3.18 +/- 1.32 h respectively), area under curve from 0 to 12 h (AUC(0-12)) (1.22 +/- 0.22 vs. 2.76 +/- 0.58 microg x h/mL respectively) and elimination half-life (1.41 +/- 1.20 vs. 3.32 +/- 1.34 h); however, only AUC(0-12) showed significant differences after the i.m. administration. Passage of erythromycin in milk was high (peak milk concentration/peak serum concentration, 2.06 +/- 0.36 and AUC(0-12milk)/AUC(0-12serum),6.9 +/- 1.05 and 2.37 +/- 0.61 after i.v. and i.m. administrations respectively). We, therefore, conclude that lactation affects erythromycin pharmacokinetics in goats.

Targeted degradation of the AML1/MDS1/EVI1 oncoprotein by arsenic trioxide

Arsenic trioxide (ATO) has been found to be an effective treatment for acute promyelocytic leukemia patients and is being tested for treating other hematologic malignancies. We have previously shown that AML1/MDS1/EVI1 (AME), a fusion gene generated by a t(3;21)(q26;q22) translocation found in patients with chronic myelogenous leukemia during blast phase, myelodysplastic syndrome, or acute myelogenous leukemia (AML), impairs hematopoiesis and eventually induces an AML in mice. Both fusion partners of AME, AML1 and MDS1/EVI1, encode transcription factors and are also targets of a variety of genetic abnormalities in human hematologic malignancies. In addition, aberrant expression of ectopic viral integration site 1 (EVI1) has also been found in solid tumors, such as ovarian and colon cancers. In this study, we examined whether ATO could target AME and related oncoproteins. We found that ATO used at therapeutic levels degrades AME. The ATO treatment induces differentiation and apoptosis in AME leukemic cells in vitro as well as reduces tumor load and increases the survival of mice transplanted with these cells. We further found that ATO targets AME via both myelodysplastic syndrome 1 (MDS1) and EVI1 moieties and degrades EVI1 via the ubiquitin-proteasome pathway and MDS1 in a proteasome-independent manner. Our results suggest that ATO could be used as a part of targeted therapy for AME-, AML1/MDS1-, MDS1/EVI1-, and EVI1-positive human cancers.

Buthionine sulfoximine enhancement of arsenic trioxide-induced apoptosis in leukemia and lymphoma cells is mediated via activation of c-Jun NH2-terminal kinase and up-regulation of death receptors

The mechanism of apoptosis induced by treatment with As(2)O(3) alone or in combination with buthionine sulfoximine (BSO) was studied in NB4, U937, Namalwa, and Jurkat cells. As(2)O(3) at concentrations <2 micromol/L induced apoptosis in NB4 cells and Namalwa cells but not in U937 and Jurkat cells. As(2)O(3)-induced apoptosis in NB4 cells and Namalwa cells correlated with increase of H(2)O(2) and caspase activation without activation of c-Jun NH(2)-terminal kinase (JNK). BSO (10 micromol/L) depleted the reduced form of intracellular glutathione without inducing apoptosis but synergized with 1 micromol/L As(2)O(3) to induce apoptosis in all four cell lines. This synergy correlated with JNK activation. Treatment with As(2)O(3) plus BSO, but not with As(2)O(3) alone, increased the levels of death receptor (DR) 5 protein and caspase-8 cleavage. The JNK inhibitor SP600125 inhibited the increase in DR5 protein and attenuated apoptosis induced by treatment with As(2)O(3) plus BSO. These observations suggest that a DR-mediated pathway activated by JNK is involved in apoptosis induced by treatment with As(2)O(3) plus BSO.

The disposition of lidocaine during a 12-hour intravenous infusion to postoperative horses

Lidocaine is administered as an intravenous infusion to horses for a variety of reasons, but no study has assessed plasma lidocaine concentrations during a 12-h infusion to horses. The purpose of this study was to evaluate the plasma concentrations and pharmacokinetics of lidocaine during a 12-h infusion to postoperative horses. A second purpose of the study was to evaluate the in vitro plasma protein binding of lidocaine in equine plasma. Lidocaine hydrochloride was administered as a loading dose, 1.3 mg/kg over 15 min, then by a constant rate IV infusion, 50 microg/kg/min to six postoperative horses. Lidocaine plasma concentrations were measured by a validated high-pressure liquid chromatography method. One horse experienced tremors and collapsed 5.5 h into the study. The range of plasma concentrations during the infusion was 1.21-3.13 microg/mL. Lidocaine plasma concentrations were significantly increased at 0.5, 4, 6, 8, 10 and 12 h compared with 1, 2 and 3 h. The in vitro protein binding of lidocaine in equine plasma at 2 microg/mL was 53.06+/-10.28% and decreased to 27.33+/-9.72% and 29.52+/-6.44% when in combination with ceftiofur or the combination of ceftiofur and flunixin, respectively. In conclusion, a lower lidocaine infusion rate may need to be administered to horses on long-term lidocaine infusions. The in vitro protein binding of lidocaine is moderate in equine plasma, but highly protein bound drugs may displace lidocaine increasing unbound concentrations and the risk of lidocaine toxicity.

A molecular signature to discriminate dysplastic nodules from early hepatocellular carcinoma in HCV cirrhosis

BACKGROUND & AIMS

Small liver nodules approximately 2 cm are difficult to characterize by radiologic or pathologic examination. Our aim was to identify a molecular signature to diagnose early hepatocellular carcinoma (HCC).

METHODS

The transcriptional profiles of 55 candidate genes were assessed by quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) in 17 dysplastic nodules (diameter, 10 mm) and 20 early HCC (diameter, 18 mm) from HCV cirrhotic patients undergoing resection/transplantation and 10 nontumoral cirrhotic tissues and 10 normal liver tissues. Candidate genes were confirmed by quantitative RT-PCR in 20 advanced HCCs and by immunohistochemistry in 75 samples and validated in an independent set of 29 samples (dysplastic nodules [10] and small HCC [19; diameter, 20 mm]).

RESULTS

Twelve genes were significantly, differentially expressed in early HCCs compared with dysplastic nodules (>2-fold change; area under the receiver operating characteristic curve > or =0.8): this included TERT, GPC3, gankyrin, survivin, TOP2A, LYVE1, E-cadherin, IGFBP3, PDGFRA, TGFA, cyclin D1, and HGF. Logistic regression analysis identified a 3-gene set including GPC3 (18-fold increase in HCC, P = .01), LYVE1 (12-fold decrease in HCC, P = .0001), and survivin (2.2-fold increase in HCC, P = .02), which had a discriminative accuracy of 94%. The validity of the gene signature was confirmed in a prospective testing set. GPC3 immunostaining was positive in all HCCs and negative in dysplastic nodules (22/22 vs 0/14, respectively, P < .001). Nuclear staining for survivin was positive in 12 of 13 advanced HCC cases and in 1 of 9 early tumors.

CONCLUSIONS

Molecular data based on gene transcriptional profiles of a 3-gene set allow a reliable diagnosis of early HCC. Immunostaining of GPC3 confirms the diagnosis of HCC.

Cyclin D1 Overexpression and Response to Bortezomib Treatment in a Breast Cancer Model

BACKGROUND

Cyclin D1 is frequently overexpressed in breast cancer, and its overexpression is, surprisingly, associated with improved survival. One potential mechanism for this association involves signal transducer and activator of transcription 3 (STAT3).

METHODS

Cyclin D1 and STAT3 expression were assessed in human tumors using microarray analysis and in breast cancer cell lines HBL100, T47D, MCF7, MDA-MB-453, and BT20 and in HBL100 and T47D cells stably overexpressing cyclin D1 using immunoblot analysis. Cyclin D1 protein was stabilized by treatment with the proteasome inhibitor bortezomib, and the effects on STAT3 expression in vitro was determined by using immunoblotting and on xenograft tumor growth and apoptosis in vivo was determined by using terminal deoxyuridine nick-end labeling assays. All statistical tests were two-sided.

RESULTS

Tumors with high cyclin D1 expression (n = 17) had low STAT3 expression (mean = 274 arbitrary units), and those with low cyclin D1 expression (n = 31) had high STAT3 expression (mean = 882 arbitrary units) (P<.001). In HBL100 and T47D parental and cyclin D1-overexpressing cells, cyclin D1 overexpression was also inversely associated with STAT3 expression, and cyclin D1 directly reduced the expression of STAT3. Stabilization of cyclin D1 protein by bortezomib treatment further amplified the cyclin D1-dependent repression of STAT3 in vitro and slowed tumor growth in vivo (week 7: untreated mean = 185.7 mm3 versus treated mean = 136.2 mm3, difference = 49.5 mm3, 95% confidence interval [CI] = 18 to 81 mm3, P = .007; week 8: untreated mean = 240.2 mm3 versus treated mean = 157.3 mm3, difference = 82.9 mm3, 95% CI = 9.1 to 156.7 mm3, P = .0014; and week 9: untreated mean = 256.4 mm3 versus treated mean = 170.2 mm3, difference = 86.2 mm3, 95% CI = 22.8 to 149.6 mm3, P = .006) and increased apoptosis (untreated mean = 19% versus treated mean = 54%, difference = 35%, 95% CI = 24.7% to 45.4%; P = .013) of xenograft tumors.

CONCLUSIONS

Cyclin D1 repression of STAT3 expression may explain the association between cyclin D1 overexpression and improved outcome in breast cancer. In addition, bortezomib can amplify the proapoptotic function of cyclin D1, raising the possibility that cyclin D1 levels may be a marker for predicting the response to this novel drug.

Targeting inhibition of K-ras enhances Ad.mda-7-induced growth suppression and apoptosis in mutant K-ras colorectal cancer cells

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a cancer-specific, growth-suppressing and apoptosis-inducing gene with broad-spectrum antitumor activity. However, when administered by means of a replication-incompetent adenovirus, Ad.mda-7, several colorectal carcinoma cell lines are resistant to its antiproliferative and antisurvival effects. We have presently endeavored to determine if K-ras mutations, present in approximately 40-50% of colorectal cancers and which may mediate resistance to chemotherapy and radiotherapy, represent a predisposing genetic factor mitigating reduced sensitivity to Ad.mda-7. To suppress ras expression, three structurally different replication-incompetent adenoviral vectors were engineered that express (1) an intracellular, neutralizing single-chain antibody (scAb) to p21 ras (Ad.K-ras scAb), (2) an antisense (AS) K-ras gene (Ad.K-ras AS) or (3) both mda-7/IL-24 and a K-ras AS gene in a single bipartite virus (Ad.m7.KAS). Simultaneous inhibition of K-ras and expression of mda-7/IL-24 enhanced killing of colorectal carcinoma cells with mutated K-ras, but not with wild-type K-ras. The extent of killing depended on the degree of K-ras downregulation, with Ad.K-ras AS being generally more efficient than Ad.K-ras scAb in combination with Ad.mda-7. These findings support an effective dual-combinatorial approach for the therapy of colorectal cancers that employs a unique cancer-specific suppressor gene (mda-7/IL-24) with targeted inhibition of oncogene (ras) expression.

Upregulation of Bfl-1/A1 in leukemia cells undergoing differentiation by all-trans retinoic acid treatment attenuates chemotherapeutic agent-induced apoptosis

All-trans retinoic acid (ATRA) induces differentiation of NB4 and HL-60 leukemia cells, but not R4 and HL-60/Res cells. Three agents used in cancer therapy, doxorubicin (Dox), arsenic trioxide (As(2)O(3)) and paclitaxel, induce apoptosis, but not differentiation, in all of these cell lines. The induction of apoptosis by these agents is decreased in ATRA-pretreated NB4 and HL-60 cells, but not in ATRA-pretreated R4 and HL-60/Res cells. The level of Bcl-2 protein is decreased by ATRA treatment in NB4, HL-60 and HL-60/Res cells. The level of Mcl-1 protein is increased by ATRA treatment in NB4 and R4 cells, but not in HL-60 and HL-60/Res cells. Bfl-1/A1 mRNA is not expressed in these cell lines, however, its expression is markedly induced by ATRA treatment in NB4 and HL-60 cells, but not in R4 or HL-60/Res cells, which correlates with inhibition of apoptosis. Inhibiting Bfl-1/A1 mRNA upregulation in ATRA-pretreated NB4 cells using small interfering RNA (siRNA) partly recovers cell sensitivity to Dox-induced apoptosis. These data demonstrate that ATRA induction of Bfl-1/A1 in differentiated NB4 and HL-60 cells contributes to a loss of sensitivity to chemotherapy-induced apoptosis.

Clinical translation of epigenetics in cancer: eN-CORe—a report on the second workshop

Recent advances in understanding the role that epigenetics plays in cancer pathogenesis and understanding the mechanisms through which these processes regulate gene expression have stimulated considerable interest in developing clinically viable antineoplastic agents that target enzymatic components of transcriptional regulatory complexes responsible for the establishment of pathologic epigenetic modifications that lead to deregulated gene expression in cancer. In January 2003, a workshop was held in Baltimore to discuss the therapeutic potential of several agents that can modify chromatin structure. A follow-up meeting on "Clinical Translation of Epigenetics in Cancer" was held in Charleston, SC, in January 2005. The aim of this workshop was to assess the progress that has been made over the past 2 years in bringing effective therapeutic protocols that use agents capable of reverting pathologic epigenetic changes into the clinic. The meeting was attended by approximately 70 investigators and included formal presentations, panel group discussions, and two break-out sessions that addressed targeted therapies in hematologic and solid tumors. The aim of this article is to summarize topics discussed at this workshop and highlight conclusions as to the immediate and long-term future of epigenetic therapy in cancer.

Pharmacokinetics of two once-daily parenteral cephalexin formulations in dogs

The aims of this study were to describe and compare the pharmacokinetic profiles and T(>MIC90) of two commercially available once-daily recommended cephalexin formulations in healthy adult dogs administered by the intramuscular (i.m.) route. Six beagle dogs received a 10 mg/kg dose of an 18% parenteral suspension of cephalexin of laboratory A (formulation A) and laboratory B (formulation B) 3 weeks apart. Blood samples were collected in predetermined times after drug administration. The main pharmacokinetic parameters were (mean +/- SD): AUC((0-infinity)), 72.44 +/- 15.9 and 60.83 +/- 13.2 microg.h/mL; C(max), 10.11 +/- 1.5 and 8.50 +/- 1.9 microg/mL; terminal half-life, 3.56 +/- 1.5 and 2.57 +/- 0.72 h and MRT((0-infinity)), 5.86 +/- 1.5 and 5.36 +/- 1.2 h for formulations A and B, respectively. T(>MIC90) was 63.1 +/- 14.7 and 62.1 +/- 14.7% of the dosing interval for formulations A and B, respectively. Median (range) for t(max) was 2.0 (2.0-3.0) h and 3.0 (2.0-4.0) for formulations A and B, respectively. Geometric mean ratios of natural log-transformed AUC((0-infinity)) and C(max) and their 90% confidence intervals (CI) were 0.84 (0.72-0.98) and 0.83 (0.64-1.07), respectively. The plasma profiles of cephalexin following the administration of both formulations were similar. No statistical differences between pharmacokinetic parameters or T(>MIC90) were observed, however, bioequivalence between both formulations could not be demonstrated, as lower 90% CI failed to fell within the selected range of 80-125% for bioequivalence.

Benzodithiophenes Potentiate Differentiation of Acute Promyelocytic Leukemia Cells by Lowering the Threshold for Ligand-Mediated Corepressor/Coactivator Exchange with Retinoic Acid Receptor α and Enhancing Changes in all-trans-Retinoic Acid–Regulated Gene Expression

Differentiation induction is an effective therapy for acute promyelocytic leukemia (APL), which dramatically responds to all-trans-retinoic acid (ATRA). Recent studies have indicated that combinatorial use of retinoid and nonretinoid compounds, such as histone deacetylase inhibitors, arsenics, and PKA agonists, has higher therapeutic value in this disease and potentially in other malignancies. In a screen of 370 compounds, we identified benzodithiophene analogues as potent enhancers of ATRA-induced APL cell differentiation. These effects were not associated with changes in global histone acetylation and, for the most potent compounds, were exerted at very low nanomolar concentrations, and were paralleled by enhancement of some, but not all, ATRA-modulated gene expressions. Investigating the mechanism underlying the effects of these drugs on ATRA-induced APL cell differentiation, we have shown that benzodithiophenes enhance ATRA-mediated dissociation and association of corepressor N-CoR and coactivator p300 acetyltransferase, respectively, with retinoic acid receptor (RAR) alpha proteins. These data suggest that benzodithiophenes act at the level of receptor activation, possibly by affecting posttranslational modification of the receptor (and/or coregulators), thus leading to an enhancement in ATRA-mediated effects on gene expression and APL cell differentiation. Given the specificities of these low benzodithiophene concentrations for PML-RARalpha and RARalpha, these drugs may be useful for combinatorial differentiation therapy of APL and possibly other acute myelogenous leukemia subtypes in which the overall ATRA signaling is suppressed.

Benzodithiophenes Induce Differentiation and Apoptosis in Human Leukemia Cells

All-trans retinoic acid (ATRA) induces clinical remission in patients with t(15;17) acute promyelocytic leukemia (APL) carrying leukemogenic promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha) fusion protein by overcoming PML-RARalpha transcriptional repression and inducing myeloid differentiation. To identify more potent chemical differentiation inducers, a screening assay was developed utilizing an ATRA-insensitive NB4 cell line (NB4-c) in which differentiation could be measured after 48 hours when primed with ATRA followed by other potential inducers. Over 300 cytostatic agents selected from the National Cancer Institute library were screened using this established method. Three compounds, NSC656243, NSC625748, and NSC144168, were identified to amplify ATRA-induced differentiation with acceptable cytotoxicity in NB4-c cells. In the absence of ATRA, these compounds also induced HL-60 and murine erythroleukemia cells to undergo partial differentiation. NSC656243, a benzodithiophene compound, was selected for further studies to examine the underlying mechanism of action. The differentiation effect of NSC656243 was associated with enhanced ATRA-mediated up-regulation of cell cycle regulatory proteins p21waf1 and p27kip1, retinoblastoma dephosphorylation, expression of RIG-E and RIG-G, and myelomonocytic differentiation-specific down-regulation of the myeloperoxidase (MPO) gene. Moreover, at 2- to 3-fold higher concentrations than those used to synergize with ATRA, NSC656243 induced apoptosis in NB4-c cells by reactive oxygen species-mediated pathways. The dual effects of benzodithiophenes (i.e., differentiation and apoptosis induction) support further development of these compounds as therapeutic agents for leukemia.

Boswellic acid acetate induces apoptosis through caspase-mediated pathways in myeloid leukemia cells

The mechanism of the cytotoxic effect of boswellic acid acetate, a 1:1 mixture of alpha-boswellic acid acetate and beta-boswellic acid acetate, isolated from Boswellia carterri Birdw on myeloid leukemia cells was investigated in six human myeloid leukemia cell lines (NB4, SKNO-1, K562, U937, ML-1, and HL-60 cells). Morphologic and DNA fragmentation assays indicated that the cytotoxic effect of boswellic acid acetate was mediated by induction of apoptosis. More than 50% of the cells underwent apoptosis after treatment with 20 mug/mL boswellic acid for 24 hours. This apoptotic process was p53 independent. The levels of apoptosis-related proteins Bcl-2, Bax, and Bcl-XL were not modulated by boswellic acid acetate. Boswellic acid acetate induced Bid cleavage and decreased mitochondrial membrane potential without production of hydrogen peroxide. A general caspase inhibitor (Z-VAD-FMK) and a specific caspase-8 inhibitor II (Z-IETD-FMK) blocked boswellic acid acetate-induced apoptosis. The mRNAs of death receptors 4 and 5 (DR4 and DR5) were induced in leukemia cells undergoing apoptosis after boswellic acid acetate treatment. These data taken together suggest that boswellic acid acetate induces myeloid leukemia cell apoptosis through activation of caspase-8 by induced expression of DR4 and DR5, and that the activated caspase-8 either directly activates caspase-3 by cleavage or indirectly by cleaving Bid, which in turn decreases mitochondria membrane potential.

Boswellic acid acetate induces apoptosis through caspase-mediated pathways in myeloid leukemia cells

The mechanism of the cytotoxic effect of boswellic acid acetate, a 1:1 mixture of alpha-boswellic acid acetate and beta-boswellic acid acetate, isolated from Boswellia carterri Birdw on myeloid leukemia cells was investigated in six human myeloid leukemia cell lines (NB4, SKNO-1, K562, U937, ML-1, and HL-60 cells). Morphologic and DNA fragmentation assays indicated that the cytotoxic effect of boswellic acid acetate was mediated by induction of apoptosis. More than 50% of the cells underwent apoptosis after treatment with 20 mug/mL boswellic acid for 24 hours. This apoptotic process was p53 independent. The levels of apoptosis-related proteins Bcl-2, Bax, and Bcl-XL were not modulated by boswellic acid acetate. Boswellic acid acetate induced Bid cleavage and decreased mitochondrial membrane potential without production of hydrogen peroxide. A general caspase inhibitor (Z-VAD-FMK) and a specific caspase-8 inhibitor II (Z-IETD-FMK) blocked boswellic acid acetate-induced apoptosis. The mRNAs of death receptors 4 and 5 (DR4 and DR5) were induced in leukemia cells undergoing apoptosis after boswellic acid acetate treatment. These data taken together suggest that boswellic acid acetate induces myeloid leukemia cell apoptosis through activation of caspase-8 by induced expression of DR4 and DR5, and that the activated caspase-8 either directly activates caspase-3 by cleavage or indirectly by cleaving Bid, which in turn decreases mitochondria membrane potential.

Systems analysis of transcriptome and proteome in retinoic acid/arsenic trioxide-induced cell differentiation/apoptosis of promyelocytic leukemia

Understanding the complexity and dynamics of cancer cells in response to effective therapy requires hypothesis-driven, quantitative, and high-throughput measurement of genes and proteins at both spatial and temporal levels. This study was designed to gain insights into molecular networks underlying the clinical synergy between retinoic acid (RA) and arsenic trioxide (ATO) in acute promyelocytic leukemia (APL), which results in a high-quality disease-free survival in most patients after consolidation with conventional chemotherapy. We have applied an approach integrating cDNA microarray, 2D gel electrophoresis with MS, and methods of computational biology to study the effects on APL cell line NB4 treated with RA, ATO, and the combination of the two agents and collected in a time series. Numerous features were revealed that indicated the coordinated regulation of molecular networks from various aspects of granulocytic differentiation and apoptosis at the transcriptome and proteome levels. These features include an array of transcription factors and cofactors, activation of calcium signaling, stimulation of the IFN pathway, activation of the proteasome system, degradation of the PML-RARalpha oncoprotein, restoration of the nuclear body, cell-cycle arrest, and gain of apoptotic potential. Hence, this investigation has provided not only a detailed understanding of the combined therapeutic effects of RA/ATO in APL but also a road map to approach hematopoietic malignancies at the systems level.

Molecular target-based treatment of human cancer: summary of the 10th international conference on differentiation therapy

The 10th International Conference on Differentiation Therapy was held between April 29 and May 3, 2004, in Shanghai, China. In the tradition of previous conferences from this series, which have been held biannually since the first meeting organized 20 years ago by Samuel Waxman and Giovanni Rossi in Sardinia, the organizers of the 10th International Conference on Differentiation Therapy aimed to gather basic and clinical cancer investigators in a setting of plenary sessions, workshops, and poster presentations to maximize the effective exchange of information and foster the establishment of collaborative interactions. Approximately 300 scientists attended the meeting with a mission to discuss targeted approaches to cancer treatment, which stem from our understanding of basic biological processes and the mechanisms of their deregulation during tumorigenesis.