Bioavailability and pharmacokinetic features of etoposide in childhood acute lymphoblastic leukemia patients

The bioavailability and pharmacokinetic characteristics of etoposide were studied in 12 relapsed B-lineage acute lymphoblastic leukemia (ALL) patients after both intravenous (i.v.) infusion and oral administration. Following a 1 hour i.v. infusion of 50 mg/m2 etoposide, the elimination half-life ranged from 49.8 min to 509.4 min (mean +/- SD = 218.6 +/- 134.7 min), the MRT ranged from 71.8 to 734.9 min (mean +/- SD = 315.4 +/- 194.3 min) and the systemic clearance of etoposide ranged from 15.7 to 38.0 ml/min/m2 (mean +/- SD = 24.1 +/- 7.0 ml/min/m2). The AUC ranged from 2234.9 to 5427.0 microM.min) (mean +/- SD = 3827.8 +/- 1069.5 microM.min) and Vc ranged from 2026.9 to 13,505.2 ml/m2 (mean +/- SD = 6825.4 +/- 3278.5 ml/m2). The maximum plasma etoposide levels ranged from 6.0 to 28.4 microM (mean +/- SD = 13.6 +/- 6.3 microM). The bioavailability of oral etoposide was determined by comparing the AUC following i.v. infusion to the AUC following oral administration in the same patient. The overall bioavailability (mean +/- SD) was 60.6 +/- 22.4% (ranged from 17.6% to 91.2%). The elimination half-life following oral administration (mean +/- SD) was 209.8 +/- 196.3 min (ranged from 51.0 to 794.2 min). The time required to reach the maximum plasma etoposide concentration was 145.4 +/- 118.7 min (ranged from 23.7 to 396.9 min). To our knowledge, this is the first report concerning the bioavailability of etoposide in pediatric leukemia patients. All of the other pharmacokinetic properties of etoposide in pediatric B-lineage ALL leukemia patients reported here were similar to those described previously.

Lack of adverse effects on fertility of female CD-1 mice exposed to repetitive intravaginal gel-microemulsion formulation of a dual-function anti-HIV agent: aryl phosphate derivative of bromo-methoxy-zidovudine (compound WHI-07)

5-bromo-6-methoxy-5,6-dihydro-3(')-azidothymidine-5(')-(p-bromophenyl) methoxyalaninyl phosphate (WHI-07), a novel bromo-methoxy-substituted aryl phosphate derivative of zidovudine (ZDV), is a potent dual-function contraceptive agent with anti-HIV activity. Its potential for reproductive toxicity was assessed in a series of experiments using CD-1 mice under the conditions of its intended use as an intravaginal microbicide. Female CD-1 mice were exposed intravaginally to a gel-microemulsion formulation containing 0%, 0.5%, 1.0% or 2.0% WHI-07 for up to 13 weeks. On a molar basis, these concentrations represent 1400-5700 times its in vitro spermicidal IC(50) and 1.4-5.7(x10(6)) times its in vitro anti-HIV IC(50). We examined the effects of intravaginally administered WHI-07 on: ovulation efficiency; in vivo fertilization and early embryonic, fetal development; and reproductive outcome, including neonatal survival and pup development. Compound WHI-07 was administered intravaginally during superovulation, organogenesis and prior to mating for 5 and 10 consecutive days and for 13 weeks, respectively. Mice were evaluated for ovulation efficiency and fertilization rate and cleavage 14 and 40 h after human chorionic gonadotropin (hCG) injection, respectively. Pregnant mice were administered 2% WHI-07 intravaginally during gestation days (GD) 6-15 and measures of teratogenicity were evaluated on GD 17. For short-term toxicity study, mice were given intravaginal treatment of gel-microemulsion containing 0%, 0.5%, 1.0% and 2.0% WHI-07 for 13 weeks and then mated with untreated males to evaluate potential reproductive and developmental effects. Repeated intravaginal exposure of mice to 2% WHI-07 had no adverse effects on ovulation response, mean number of eggs recovered or the percentage of eggs fertilized or cleaved. No evidence of reproductive toxicity, fetal toxicity or teratogenicity was found following repetitive intravaginal application of 2% WHI-07 during the period of organogenesis. Furthermore, repeated intravaginal exposure of mice to 0.5-2.0% WHI-07 for 13 weeks had no adverse effect on the subsequent reproductive capability, perinatal outcome or growth and development of the offspring. Compound WHI-07 shows unique clinical potential as a safe, dual-function vaginal contraceptive for curbing mucosal and perinatal HIV transmission.

Binding interactions between the active center cleft of recombinant pokeweed antiviral protein and the alpha-sarcin/ricin stem loop of ribosomal RNA

Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein that catalytically cleaves a specific adenine base from the highly conserved alpha-sarcin/ricin loop of the large ribosomal RNA, thereby inhibiting protein synthesis at the elongation step. Recently, we discovered that alanine substitutions of the active center cleft residues significantly impair the depurinating and ribosome inhibitory activity of PAP. Here we employed site-directed mutagenesis combined with standard filter binding assays, equilibrium binding assays with Scatchard analyses, and surface plasmon resonance technology to elucidate the putative role of the PAP active center cleft in the binding of PAP to the alpha-sarcin/ricin stem loop of rRNA. Our findings presented herein provide experimental evidence that besides the catalytic site, the active center cleft also participates in the binding of PAP to the target tetraloop structure of rRNA. These results extend our recent modeling studies, which predicted that the residues of the active center cleft could, via electrostatic interactions, contribute to both the correct orientation and stable binding of the substrate RNA molecules in PAP active site pocket. The insights gained from this study also explain why and how the conserved charged and polar side chains located at the active center cleft of PAP and certain catalytic site residues, that do not directly participate in the catalytic deadenylation of ribosomal RNA, play a critical role in the catalytic removal of the adenine base from target rRNA substrates by affecting the binding interactions between PAP and rRNA.

Expression of TEL-AML1 fusion transcripts and response to induction therapy in standard risk acute lymphoblastic leukemia

We prospectively examined the frequency of the t(12;21)TEL-AML1 fusion in 504 children with newly diagnosed standard risk ALL using RT-PCR assays. Cells from 95 patients (18.8%) were TEL-AML1+. There was a significantly higher frequency of pseudodiploidy among the TEL-AML1+ cases (39.4% versus 14.1%, P = 0.001), primarily because structural abnormalities involving 12p and del(6q) occurred more frequently in the TEL-AML1+ group. TEL-AML1+ ALL was more sensitive to the induction chemotherapy than TEL-AML1- ALL. The percentage of "rapid early responders", i.e., patients who achieved an M1 (< 5% blasts) or M2 (5-25% blasts) marrow status on day 7 of induction chemotherapy, was significantly higher among TEL-AML1+ cases. The quality of remission of RT-PCR positive cases was excellent, as evidenced by the very low to absent MRD burden of their end-of-induction bone marrow specimens. TEL-AML1+ patients also had an excellent early EFS outcome. The probability of EFS at 30 months from study entry were 98.9 +/- 1.0% for the TEL-AML1+ group and 92.1 +/- 1.5% for the TEL-AML1- group (P = 0.0001). This prospective study significantly expands the knowledge gained from previous studies regarding the prognostic significance of t(12;21)TEL-AML1 fusion in pediatric ALL.

Role of a JAK3-dependent biochemical signaling pathway in platelet activation and aggregation

Here we provide experimental evidence that identifies JAK3 as one of the regulators of platelet function. Treatment of platelets with thrombin induced tyrosine phosphorylation of the JAK3 target substrates STAT1 and STAT3. Platelets from JAK3-deficient mice displayed a decrease in tyrosine phosphorylation of STAT1 and STAT3. In accordance with these data, pretreatment of human platelets with the JAK3 inhibitor WHI-P131 markedly decreased the base-line enzymatic activity of constitutively active JAK3 and abolished the thrombin-induced tyrosine phosphorylation of STAT1 and STAT3. Following thrombin stimulation, WHI-P131-treated platelets did not undergo shape changes indicative of activation such as pseudopod formation. WHI-P131 inhibited thrombin-induced degranulation/serotonin release as well as platelet aggregation. Highly effective platelet inhibitory plasma concentrations of WHI-P131 were achieved in mice without toxicity. WHI-P131 prolonged the bleeding time of mice in a dose-dependent manner and improved event-free survival in a mouse model of thromboplastin-induced generalized and invariably fatal thromboembolism. To our knowledge, WHI-P131 is the first anti-thrombotic agent that prevents platelet aggregation by inhibiting JAK3.

Biased distribution of chromosomal breakpoints involving the MLL gene in infants versus children and adults with t(4;11) ALL

Derivative chromosomes of 40 patients diagnosed with t(4;11) acute lymphoblastic leukemia (ALL) were analysed on the genomic DNA level. Chromosomal breakpoints were identified in most cases within the known breakpoint cluster regions of the involved MLL and AF4 genes. Due to our current knowledge of the primary DNA sequences of both breakpoint cluster regions, specific features were identified at the chromosomal fusion sites, including deletions, inversions and duplications of parental DNA sequences. After separation of all t(4;11) leukemia patients into two age classes (below and above 1 year of age), the analysis of chromosomal fusion sites revealed significant differences in the distribution of chromosomal breakpoints and led to the definition of two hotspot areas within the MLL breakpoint cluster region. This may point to the possibility of different age-linked mechanisms that were leading to t(4;11) chromosomal translocations.

Structure-based design of novel anticancer agents

Recently identified agents that interact with cytoskeletal elements such as tubulin include synthetic spiroketal pyrans (SPIKET) and monotetrahydrofuran compounds (COBRA compounds). SPIKET compounds target the spongistatin binding site of beta-tubulin and COBRA compounds target a unique binding cavity on alpha-tubulin. At nanomolar concentrations, the SPIKET compound SPIKET-P causes tubulin depolymerization and exhibits potent cytotoxic activity against cancer cells. COBRA-1 inhibits GTP-induced tubulin polymerization. Treatment of human breast cancer and brain tumor cells with COBRA-1 caused destruction of microtubule organization and apoptosis. Other studies have identified some promising protein tyrosine kinase inhibitors as anti-cancer agents. These include EGFR inhibitors such as the quinazoline derivative WHI-P97 and the leflunomide metabolite analog LFM-A12. Both LFM-A12 and WHI-P97 inhibit the in vitro invasiveness of EGFR positive human breast cancer cells at micromolar concentrations and induce apoptotic cell death. Dimethoxyquinazoline compounds WHI-P131 and WHI-P154 inhibit tyrosine kinase JAK3 in leukemia cells. Of particular interest is WHI-P131, which inhibits JAK3 but not JAK1, JAK2, SYK, BTK, LYN, or IRK at concentrations as high as 350 microM. Studies of BTK inhibitors showed that the leflunomide metabolite analog LFM-A13 inhibited BTK in leukemia and lymphoma cells. Consistent with the anti-apoptotic function of BTK, treatment of leukemic cells with LFM-A13 enhanced their sensitivity to chemotherapy-induced apoptosis.

Anticancer activity of synthetic analogues of the phorboxazoles

The phorboxazoles are recently described natural products that are extremely cytostatic towards the National Cancer Institute's panel of 60 tumor cell lines. We report here the results of preliminary structure-activity studies of synthetic analogues of the phorboxazoles against BT-20 breast cancer, NALM-6 B-lineage ALL, U373 brain tumor, and U373 glioblastoma cell lines. These data indicate the importance of several of the natural products' structural moieties for potent anticancer activity.

Chemosensitivity of TEL-AML1 fusion transcript positive acute lymphoblastic leukemia cells

The TEL-AML1 fusion which results from a cryptic t(12;21) translocation is the most frequently occurring genetic abnormality in childhood acute lymphoblastic leukemia (ALL) and has been associated with an excellent treatment outcome. In the present study, we examined the FAS/BCL-2 expression profiles and chemosensitivity of primary leukemic cells from children with newly diagnosed t(12;21)TEL-AML1 fusion transcript-positive versus t(12;21)TEL-AML1 fusion transcript-negative standard risk ALL. TEL-AML1(+) ALL cells expressed higher levels of the pro-apoptotic protein Fas and lower levels of the anti-apoptotic protein Bcl2 than TEL-AML1(-) ALL cells, as determined by confocal laser scanning microscopy. TEL-AML1(+) ALL cells were more sensitive to the apoptosis-inducing effects of serum deprivation, dexamethasone and vincristine than TEL-AML1(-) ALL cells. This study provides novel mechanistic insights regarding the chemosensitivity of TEL-AML1(+) ALL cells and provides a cogent explanation for the excellent leukemia-free survival outcome of children with TEL-AML1(+) ALL treated on contemporary chemotherapy programs.

Apoptosis inducing novel anti-leukemic agent, bis(4,7-dimethyl-1,10 phenanthroline) sulfatooxovanadium(IV) [VO(SO4)(Me2-Phen)2] depolarizes mitochondrial membranes

Bis(4,7-dimethyl-1,10 phenanthroline) sulfatooxovanadium(IV) [VO(SO(4) )(Me(2)-Phen)(2)] induces apoptosis in human NALM-6 leukemia cells. In the present report, we demonstrate that VO(SO(4) )(Me(2)-Phen)(2)-induced apoptosis is mediated through the generation of reactive oxygen species (ROS), depletion of glutathione and depolarization of mitochondrial membrane potential (DeltaPsim). Using multilaser flow cytometry methods, we further mapped out the death sequence that occurs in VO(SO(4))(Me(2)-Phen)(2)-treated leukemic cells. Triple labeling method to measure ROS, DeltaPsim and glutathione coupled with multilaser excitation flow cytometry showed that induction of ROS took place before the loss of mitochondrial permeability transition and depletion of glutathione. Correlated two parameter plots of glutathione content versus DeltaPsim showed that loss of DeltaPsim and depletion of glutathione closely follows each other. Translocation of phosphatidylserine to the outer leaflet of the cell membrane was the final step in the process before the cells became apoptotic. These results demonstrate that the mitochondrial permeability transition takes place during VO(SO(4))(Me(2)-Phen)(2)-induced apoptosis and is mediated through induction of ROS and depletion of glutathione.

GM-144, a novel lipophilic vaginal contraceptive gel-microemulsion

In a systematic effort to develop a dual-function intravaginal spermicide as well as a drug delivery vehicle against sexually transmitted pathogens, a submicron particle size (30-80 nm), lipophilic and spermicidal gel-microemulsion (viz GM-144) containing the pharmaceutical excipients propylene glycol, Captex 300, Cremophor EL, Phospholipon 90G, Rhodigel, Pluronic F-68, and sodium benzoate was formulated. GM-144 completely immobilized sperm in human or rabbit semen in less than 30 seconds. Therefore, the in vivo contraceptive potency of intravaginally applied GM-144 was compared in the standard rabbit model to those of the detergent spermicide, nonoxynol-9 (N-9)-containing formulation. Eighty-four ovulated New Zealand White rabbits in subgroups of 28 were artificially inseminated with and without intravaginal administration of GM-144 or 2% N-9 (Gynol II) formulation and allowed to complete term pregnancy. GM-144 showed remarkable contraceptive activity in the rigorous rabbit model. When compared with control, intravaginal administration of GM-144 and Gynol II resulted in 75% and 70.8% inhibition of fertility (P <.0001 versus control, Fisher's exact test), respectively. Thus, GM-144 as a vaginal contraceptive was as effective as the commercially available N-9 gel. In the rabbit vaginal irritation test, none of the 6 rabbits given daily intravaginal application of spermicidal GM-144 for 10 days developed epithelial ulceration, edema, leukocyte influx, or vascular congestion characteristic of inflammation (total score = 5). Therefore, GM-144 has the potential to become a clinically useful safe vaginal contraceptive and a vehicle for formulating lipophilic drugs used in reducing the risk of heterosexual transmission of sexually transmitted diseases.

Bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(I.V.) as a novel antileukemic agent with matrix metalloproteinase inhibitory activity

We have examined the in vitro anticancer activity of METVAN [bis(4,7-dimethyl-1,10 phenanthroline) sulfatooxovanadium(IV); VO(SO(4))(Me(2)-Phen)(2)] against acute lymphoblastic leukemia (ALL; NALM-6 and MOLT-3), acute myeloid leukemia (AML; HL-60), Hodgkin's disease (HS445), and multiple myeloma (ARH-77, U266BL, and HS-SULTAN) cell lines as well as primary leukemic cells from patients with ALL, AML, and chronic acute myeloid leukemia (CML). METVAN induced apoptosis in NALM-6, MOLT-3, and HL-60 cells in a concentration-dependent fashion with EC(50) values of 0.19 +/- 0.03 microM, 0.19 +/- 0.01 microM, and 1.1 +/- 0.2 microM, respectively. METVAN induced apoptosis at low micromolar concentrations in primary leukemic cells from patients with ALL, AML, and CML. METVAN inhibited the constitutive expression of matrix metalloproteinase (MMP)-9 protein and its gelatinolytic activity in HL-60 cells and MMP-2 as well as MMP-9 gelatinolytic activities in leukemic cells from ALL, AML, and CML patients. Furthermore, METVAN inhibited the leukemic cell adhesion to the extracellular matrix proteins laminin, type IV collagen, vitronectin, and fibronectin and the invasion through Matrigel matrix. Further preclinical development of METVAN may provide the basis for the development of more effective chemotherapy programs.

Vanadocenes as potent anti-proliferative agents disrupting mitotic spindle formation in cancer cells

We present experimental data which establish the organometallic compounds vanadocene dichloride (VDC) and vanadocene acetylacetonate (VDacac) as potent anti-proliferative agents. We first examined the effects of VDC and VDacac on the rapid embryonic cell division and development of Zebrafish. Both compounds were capable of causing cell division block at the 8-16 cell stage of embryonic development followed by total cell fusion and developmental arrest. We next examined the effect of VDC and VDacac on proliferation of human breast cancer and glioblastoma cell lines using MTT assays. VDC inhibited the proliferation of the breast cancer cell line BT-20 as well as the glioblastoma cell line U373 in a concentration-dependent fashion with IC50 values of 11.0, 14.9 and 18.6 microM, respectively. VDacac inhibited cellular proliferation with IC50 values of 9.1, 26.9 and 35.5 microM, respectively. Whereas in vehicle-treated control cancer cells mitotic spindles were organized as a bipolar microtubule array and the DNA was organized on a metaphase plate, vanadocene-treated cancer cells had aberrant monopolar mitotic structures where microtubules were detected only on one side of the chromosomes and the chromosomes were arranged in a circular pattern. In contrast to control cells which showed a single focus of gamma-tubulin at each pole of the bipolar mitotic spindle, VDC- or VDacac-treated cells had two foci of gamma-tubulin on the same side of the chromosomes resulting in a broad centrosome at one pole. All monopolar spindles examined had two foci of gamma-tubulin labeling consistent with a mechanism in which the centrosomes duplicate but do not separate properly to form a bipolar spindle. These results provide unprecedented evidence that organometallic compounds can block cell division in human cancer cells by disrupting bipolar spindle formation. In accordance with these results vanadocene treatment caused an arrest at the G2/M phase of the cell cycle. This unique mechanism of anti-mitotic function warrants further development of vanadocene complexes as anti-cancer drugs.

Short-Term (13-week) toxicity study of 5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-bromophenyl) methoxyalaninyl phosphate (WHI-07), a novel anti-HIV and contraceptive agent, in B6C3F1 mice

The zidovudine derivative, WHI-07 (5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-bromophenyl) methoxyalaninyl phosphate), is a dual-function spermicidal agent with potent anti-HIV activity. In this study, groups of 20 female B6C3F1 mice were exposed intravaginally to a gel microemulsion containing 0, 0.5, 1.0, or 2.0% WHI-07, 5 days per week for 13 consecutive weeks. On a molar basis, these concentrations of WHI-07 are 1400- to 5700-times higher than its spermicidal EC(50) and 1.4 x 10(6) to 5.7 x 10(6) times higher than its in vitro anti-HIV IC(50). After 13 weeks of intravaginal treatment, mice were evaluated for toxicity. The endpoints that were used for evaluation included survival, body weight, hematologic and clinical chemistry profiles, absolute and relative organ weights, and histopathology. No effects related to WHI-07 treatments were observed on survival, mean body weight, and mean body-weight gain. Repeated intravaginal exposure of mice to WHI-07 for 13 weeks had no toxicologically significant effect on organ weights, and did not cause any adverse changes in hematology parameters or blood chemistry profiles. Extensive histopathologic examination of tissues showed no lesions of pathologic significance. Thus, intravaginal application of WHI-07, for up to 13 weeks, does not cause systemic toxicity.

X-ray structure, solution properties, and biological activity profile of vanadocene(IV) acetylacetonate complex, [VCp2(acac)](CF3SO3): a dual-function anti-cancer agent with anti-angiogenic and anti-mitotic properties

The structure of [V(eta5-C5H5)2(CH3C(O)CHC(O)CH3)](O3SCF3) (1) (=[VCp2(acac)](O3SCF3)), a dual-function anti-cancer agent with anti-angiogenic and anti-mitotic properties, was determined by single-crystal X-ray diffraction. The geometry is well described as a pseudo-tetrahedral like structure with the centroids of the cyclopentadienyl rings and the two oxygen atoms of the acetylacetonate ring in the ancillary positions of the central vanadium (IV) atom. The bisector of the V(acac) fragment deviates from the C2 axis of the ligand framework by only 4 degrees, compared to a deviation of 7 degrees for the V(acac) fragment in the tetramethylethano-bridged vanadocene acetyl acetonate complex. Crystal data for 1: space group, P2(1)/c; a=7.5544(9) A, b=14.936(2) A, c=16.193(2) A, beta=102.901(2) degrees, V= 1781.0(4) A3; Z=4; R=0.0506 for 2310 reflections with I> 2sigma(I). This report also details the electron paramagnetic resonance, UV/Vis spectroscopy, electrochemical properties and the biological activity profile of this potent anti-cancer agent.

Anti-inflammatory activity of 2,4, 6-trihydroxy-alpha-p-methoxyphenyl-acetophenone (compound D-58)

BACKGROUND

Active oxygen radicals as well as a variety of cytosolic protein tyrosine kinases play a role in the regulation of prostaglandin E(2) (PGE(2)), a key inflammatory mediator, released by skin cells in response to irradiation with ultraviolet B light (UVB). Identification of chemical compounds that can interrupt such events may provide a basis for the development of potent anti-inflammatory agents.

OBJECTIVE

To investigate the effect of a novel genistein analog, 2,4, 6-trihydroxy-alpha-p-methoxyphenylacetophenone, with antioxidant property (compound D-58), on UVB-induced inflammatory responses.

METHODS

Epidermal cell cultures were irradiated with UVB both in the presence and absence of compound D-58 and the PGE(2) released in the medium was determined by ELISA. For in vivo studies, skin inflammation was induced in mice either by carrageenan challenge of the air pouch or by an acute exposure of skin to UVB radiation. The resulting inflammatory mediator release, skin edema and the histological changes of the skin were determined both in the presence and absence of compound D-58.

RESULTS

Compound D-58 treatment effectively inhibited the development of edema and histological changes in the skin of UVB-irradiated mice as well as the release of PGE(2) in vitro as well as in vivo.

CONCLUSION

Compound D-58 (2,4,6-trihydroxy-alpha-p-methoxyphenylacetophenone) has potent anti-inflammatory properties.

Anti-HIV activity of aromatic and heterocyclic thiazolyl thiourea compounds

Several thiazolyl thiourea derivatives were designed and synthesized as non-nucleoside inhibitors (NNRTI) of HIV-1 reverse transcriptase. Six lead compounds were identified that showed subnanomolar IC50 values for the inhibition of HIV replication, were minimally toxic to human peripheral blood mononuclear cells (PBMC) with CC50 values ranging from 28 to >100 microM, and showed remarkably high selectivity indices ranging from 28,000 to >100,000. The most promising compound was N-[1-(1-furoylmethyl)]-N'-[2-(thiazolyl)]thiourea (compound 6), which showed potency against two NNRTI-resistant HIV-1 isolates (A17 and A17 variant) at nanomolar to low micromolar concentrations, exhibited much greater potency against both wild-type as well as NNRTI-resistant HIV-1 than nevirapine, delavirdine, HI-443, and HI-244, was minimally toxic to PBMC, and had a selectivity index of > 100,000. The potency and minimal cytotoxicity of these aromatic/heterocyclic thiourea compounds suggest that they may be potentially useful as anti-AIDS drugs.

Intravaginal toxicity studies of a gel-microemulsion formulation of spermicidal vanadocenes in rabbits

Bis-cyclopentadienyl complexes of vanadium(IV) or vanadocenes are rapid and potent inhibitors of human sperm motility with potential as a new class of contraceptive agents. We investigated the toxicity potential of intravaginally administered gel-microemulsion formulation of two representative vanadocenes, vanadocene acetylacetonato monotriflate (VDACAC) and vanadocene dithiocarbamate (VDDTC), in the rabbit model. New Zealand White rabbits in subgroups of three were exposed intravaginally to a gel-microemulsion with and without 0.1 or 0.25% VDACAC and VDDTC for 10 consecutive days. The doses of vanadocenes used were nearly 500- to 1250-fold and 2000- to 5000-fold higher than their respective in vitro spermicidal EC50 values. Animals were euthanized on day 11 and vaginal tissues were evaluated for local toxicity by histopathology, cell proliferating activity by immunohistochemical detection of proliferating cell nuclear antigen (PCNA), and in situ apoptosis by the terminal deoxynucleotidyl transferase-mediated FITC-deoxyuridine triphosphate nick end-labeling (TUNEL) assay and confocal laser scanning microscopy (CLSM). Blood was analyzed for clinical chemistry profiles. Vanadium content in selected organs and body fluids was determined by atomic absorption spectroscopy. None of the rabbits given 0.1% VDACAC and VDDTC intravaginally developed epithelial ulceration, edema, leukocyte influx, or vascular congestion characteristic of inflammation. Only minimal to moderate irritation was observed at 0.25% VDACAC and VDDTC. A significant decrease in epithelial and stromal PCNA expression was observed in the 0.25% dose group. However, TUNEL assay and CLSM revealed no staining in the vaginal epithelium and only minimal nonspecific staining in the stroma. Repetitive intravaginal application of 0.1 or 0.25% VDACAC and VDDTC had no adverse effects on clinical chemistry profiles. Vanadium was not incorporated into rabbit tissues and body fluids at levels above 1 microg/g. Thus, intravaginal administration of VDACAC and VDDTC at concentrations nearly 500 and 2000 times higher than their respective in vitro spermicidal EC50 values did not induce marked vaginal irritation, mucosal toxicity, or systemic absorption of vanadium in the rabbit model. The lack of significant mucosal or systemic toxicity of intravaginal vanadocenes observed may have particular clinical utility as a new class of contraceptive agents.

Induction of aerobic peroxidation of liposomal membranes by bis(cyclopentadienyl)-vanadium(IV) (acetylacetonate) complexes

The ability of bis(cyclopentadienyl)-vanadium(IV) (acetylacetonate) (1) to initiate oxygen-dependent lipid peroxidation in zwitterionic liposomal membranes was examined in detail. A comparison of the rates of the lipid peroxidation reaction demonstrated that the electron-donating capacity of the substituted acetylacetonate ligand significantly influences the rate of reaction. An increase in the rate of lipid peroxidation correlated to a decrease in the V(IV)/V(V) redox potential. Notably, lipid peroxidation initiated with 1 proceeded without the formation of radicals as shown by EPR spin trap techniques. In contrast, lipid peroxidation initiated with non-chelated bis(cyclopentadienyl)-vanadium(IV) dichloride (6) was associated with the production of radicals under similar experimental conditions. There also was a significant pH effect on the extent of peroxidation initiated with 6 versus the reaction initiated with 1. The mode of action of 1 likely involves the activation of molecular oxygen by the vanadium(IV) center followed by allylic hydrogen atom abstraction from the lipid.

Contraceptive efficacy and safety studies of a novel microemulsion-based lipophilic vaginal spermicide

OBJECTIVE

To investigate the in vivo contraceptive potency and safety of a novel microemulsion-based lipophilic vaginal spermicide.

DESIGN

In vitro and in vivo spermicidal activity and safety of a submicron-particle-size, lipophilic gel-microemulsion (GM-4).

SETTING

Center for Advanced Preclinical Sciences at the Parker Hughes Institute.

PATIENT(S)

Nine male volunteer sperm donors.

INTERVENTION(S)

Motile human sperm in semen and medium were exposed to eight GM-4 components or GM-4 formulation. Forty-eight ovulated NZW rabbits in subgroups of 16 with or without intravaginal administration of GM-4 or nonoxynol-9 gel (N-9; Gynol II) were artificially inseminated and allowed to complete pregnancy. Eleven rabbits were exposed to daily intravaginal application of GM-4 with and without N-9 for 10 consecutive days. Ten of 20 B(6)C(3)F(1) mice were given repetitive intravaginal application of GM-4 for 5 days/week over 13 consecutive weeks.

MAIN OUTCOME MEASURE(S)

The motility of human sperm treated with GM-4 components and GM-4. Term pregnancy in rabbits and histopathological grading of rabbit vaginal tissue for irritation. Evaluation of mice for survival, growth, hematologic parameters, blood-chemistry profiles, absolute and relative organ weights, and histopathology.

RESULT(S)

The individual components of GM-4 lacked spermicidal activity in human semen, whereas the GM-4 formulation containing all the eight pharmacological excipients exhibited potent spermicidal activity with rapid kinetics. GM-4 showed remarkable contraceptive activity in the rigorous rabbit model. None of the 16 (0%) rabbits given GM-4 intravaginally before artificial insemination became pregnant. By contrast, 15 of 16 (93.7%) control rabbits and 5 of 16 (31.2%) Gynol II-treated rabbits became pregnant and delivered newborns. Thus, GM-4 was a significantly more effective contraceptive than a commercially available N-9 gel [100% vs. 68.7% protection; P< 0.05, Fisher's exact test]. Unlike the rabbits treated with N-9, none of the rabbits that were given GM-4 intravaginally for 10 consecutive days developed epithelial ulceration, edema, leukocyte influx, or vascular congestion characteristic of inflammation. Furthermore, repeated intravaginal application of GM-4 for up to 13 weeks in mice had no adverse effects on survival, growth, metabolism, or organ function.

CONCLUSION

We conclude that the novel spermicidal GM-4 formulation is safe and significantly more effective than N-9 in preventing conception.

In vivo pharmacokinetics and anti-anaphylactic activity of the novel mast cell inhibitor 4-(4'-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P131)

WHI-P131 is a novel dimethoxyquinazoline compound that is a potent inhibitor of Janus kinase-3-(JAK3)-dependent mast cell responses. In the present study, the authors investigated the anti-anaphylactic activity and pharmacokinetics of WHI-P131 in mice. After intraperitoneal (i.p.) administration of two consecutive bolus doses of 25 mg/kg injected 30 min apart at dose level of 25 mg/kg, WHI-P131 was rapidly absorbed with an observed C(max) of 82.6 microM, which is higher than the target concentration of 30 microM, at which WHI-P131 abrogates mast cell responses in vitro and the time to reach the maximum plasma concentration (t(max)) was 10.0+/-2.9 min. At a nontoxic 50 mg/kg dose level, WHI-P131 prevented compound 48/80-induced mast cell histamine release and fatal anaphylaxis in mice. Further development of WHI-P131 may provide the basis for new and effective treatment as well as prevention programs for mast cell mediated allergic reactions in clinical settings.

Thymidine kinase-independent intracellular delivery of bioactive nucleotides by aryl phosphate derivatives of bromo-methoxy zidovudine (compounds WHI-05 and WHI-07) in normal human female genital tract epithelial cells and sperm

The compounds WHI-05 (5-bromo-6-methoxy-5, 6-dihydro-3'-azidothymidine-5'-[p-methoxyphenyl] methoxyalaninyl phosphate) and WHI-07 (5-bromo-6-methoxy-5, 6-dihydro-3'-azidothymidine-5'-[p-bromophenyl] methoxyalaninyl phosphate) are aryl phosphate derivatives of zidovudine (ZDV) with dual-function anti-human immunodeficiency virus and contraceptive activity. These drugs were rationally designed to bypass the thymidine kinase (TK) dependency of ZDV activation as well as to achieve spermicidal activity. We investigated the TK activity and intracellular metabolism of WHI-05 and WHI-07 in normal human vaginal and cervical epithelial cells as well as sperm. The time- and concentration-dependent intracellular formation of ZDV metabolites following addition of WHI-05 and WHI-07 to normal human vaginal, ectocervical, and endocervical epithelial cells as well as motile sperm was studied by analytical HPLC. Thymidine kinase activity in these cells was determined by the flow cytometric method based on intracellular phosphorylation of the fluorescent nucleoside, 5-amino-2-deoxyuridine-dansyl chloride and by the ability of cell-free extracts to convert [(3)H]thymidine to thymidine monophosphate in comparison to NALM-6, a pre-B leukemia cell line. TK activity of genital tract epithelial cells and sperm was found to be relatively low or lacking. Addition of WHI-05 and WHI-07 to vaginal and cervical epithelial cells resulted in their concentration- and time-dependent conversion to alaninyl ZDV monophosphate (Ala-ZDV-MP) and 5'-ZDV monophosphate as the major metabolites. Studies using motile human sperm also demonstrated the conversion of WHI-05 and WHI-07 to Ala-ZDV-MP. These results demonstrate that human female genital tract epithelial cells and sperm efficiently convert WHI-05 and WHI-07 to bioactive ZDV metabolites despite their TK deficiency.

Pokeweed antiviral protein: a potential nonspermicidal prophylactic antiviral agent

OBJECTIVE

To investigate the effects of pokeweed antiviral protein (PAP), a 29-kDa anti-human immunodeficiency virus (HIV) protein purified from the leaves of Phytolacca americana, on human sperm function.

DESIGN

Prospective, controlled study.

SETTING

Reproductive biology department.

PATIENT(S)

Seven sperm donors.

INTERVENTION(S)

Human sperm and female genital tract epithelial cells were exposed to PAP ranging in concentration from 1 to 1,000 microg/mL.

MAIN OUTCOME MEASURES

Effect of PAP on sperm motility, kinematics, and sperm penetration through bovine mucus, as well as binding, penetration, and fusion of zona-free hamster eggs.

RESULTS

Exposing human sperm to PAP (IC(50) p24 = 14 +/- 2 nM) did not affect sperm motility and kinematics over a dose range of 1 to 1,000 microg/mL. Treating sperm with either 100 or 1,000 microg/mL of PAP had no effect on cervical mucus penetrability, nor did it affect sperm binding, penetration, and fusion of zona-free hamster eggs. PAP was noncytotoxic to genital-tract epithelial cells.

CONCLUSIONS

The broad-spectrum antiviral agent PAP was nontoxic to human sperm and female genital tract epithelial cells even at a concentration 2,000 times higher than its IC(50) value against HIV-1. PAP has particular clinical usefulness both as a nonspermicidal intravaginal microbicide and as a prophylactic antiviral agent that can inactivate infective viruses and virus-infected cells in semen before assisted reproductive technology procedures are undertaken.

Bone marrow leukemic progenitor cell content in pediatric T-lineage acute lymphoblastic leukemia patients with an isolated extramedullary first relapse

Isolated extramedullary relapse in childhood acute lymphoblastic leukemia (ALL) is associated frequently with the T-lineage immunophenotype and may be accompanied by occult bone marrow disease. We employed highly sensitive multiparameter flow cytometry and blast colony assays to quantify the leukemic progenitor cell (LPC) burden in the pretreatment bone marrows of 15 pediatric T-lineage ALL patients with an isolated extramedullary first relapse. Sites of extramedullary relapse were CNS (11 patients), testes (3 patients), and both CNS and testes (1 patient). Bone marrow LPC were detectable in 8 patients (53%) and undetectable in 7 patients (47%) at day 0 of post-relapse induction therapy, with LPC counts ranging from 0/10(6) mononuclear cells (MNC) to 518/10(6) MNC (mean +/- SEM, 50+/-34/10(6) MNC). Five of 9 patients with an early relapse (< 18 months after achieving a first complete remission [CR1]) and 3 of 6 patients with a late relapse (> or = 18 months from CR1) had detectable bone marrow LPC at day 0. Five of 8 patients with NCI-defined poor risk ALL and 3 of 7 patients with NCI-defined standard risk ALL had detectable LPC at day 0. Following post-relapse induction chemotherapy. LPC counts were detectable in bone marrows of 4 of 6 evaluated patients. Thus, approximately half of the extramedullary relapse T-lineage ALL patients studied had substantial occult involvement of the bone marrow. These findings may partly explain the previously observed poor prognosis of T-lineage patients following a CNS relapse.

Treatment of allergic asthma by targeting janus kinase 3-dependent leukotriene synthesis in mast cells with 4-(3', 5'-dibromo-4'-hydroxyphenyl)amino-6,7-dimethoxyquinazoline (WHI-P97)

4-(3',5'-Dibromo-4'-hydroxyphenyl)amino-6,7-dimethoxyquinazoline (WHI-P97) is a rationally designed potent inhibitor of Janus kinase (JAK)-3. Treatment of mast cells with WHI-P97 inhibited the translocation of 5-lipoxygenase (5-LO) from the nucleoplasm to the nuclear membrane and consequently 5-LO-dependent leukotriene (LT) synthesis after IgE receptor/FcepsilonRI crosslinking by >90% at low micromolar concentrations. WHI-P97 did not directly inhibit the enzymatic activity of 5-LO, but prevented its translocation to the nuclear membrane without affecting the requisite calcium signal. WHI-P97 was very well tolerated in mice, with no signs of toxicity at dose levels ranging from 5 microg/kg to 50 mg/kg, and LD(10) was not reached at a 50 mg/kg dose level when administered as a single i. p. or i.v. bolus dose. Therapeutic WHI-P97 concentrations, which inhibit mast cell leukotriene synthesis in vitro, could easily be achieved in vivo after the i.v. or i.p. administration of a single nontoxic 40 mg/kg bolus dose of WHI-P97. Notably, WHI-P97 showed promising biological activity in a mouse model of allergic asthma at nontoxic dose levels. Treatment of ovalbumin-sensitized mice with WHI-P97 prevented the development of airway hyper-responsiveness to methacholine in a dose-dependent fashion. Furthermore, WHI-P97 inhibited the eosinophil recruitment to the airway lumen after the ovalbumin challenge in a dose-dependent fashion. Further development of WHI-P97 may therefore provide the basis for new and effective treatment as well as prevention programs for allergic asthma in clinical settings.

Abnormalities of chromosome bands 13q12 to 13q14 in childhood acute lymphoblastic leukemia

PURPOSE

Little is known about nonrandom deletions of chromosome bands 13q12 to 13q14 (13q12-14) in acute lymphoblastic leukemia (ALL). We determined the prognostic significance of cytogenetically identified breakpoints in 13q12-14 in children with newly diagnosed ALL treated on Children's Cancer Group protocols from 1988 to 1995.

PATIENTS AND METHODS

Breakpoints in 13q12-14 were identified in 36 (2%) of the 1,946 cases with accepted cytogenetic data. Outcome analysis used standard life-table methods.

RESULTS

Seventeen patients (47%) with an abnormal 13q12-14 were classified, according to the National Cancer Institute (NCI), as poor risk, and 15 patients (42%) were standard risk; four (11%) were infants less than 12 months of age. Eight cases had balanced rearrangements of 13q12-14, 27 patients had a partial loss of 13q, and one had both a partial gain and a partial loss. The most frequent additional abnormalities among these patients were an abnormal 12p, a del(6q), a del(9p), a 14q11 breakpoint, and an 11q23 breakpoint. Nineteen patients were pseudodiploid, 10 were hyperdiploid, and seven were hypodiploid. Patients with an abnormal 13q12-14 had significantly worse event-free survival than patients lacking such an abnormality, with estimates at 6 years of 61% (SD = 14%) and 74% (SD = 1%), respectively (P =.04; relative risk = 1.74). Overall survival, however, was similar for the two groups (P =.25). The prognostic effect of an abnormal 13q was attenuated in a multivariate analysis adjusted for NCI risk status and ploidy (P =.72).

CONCLUSION

Aberrations of 13q12-14 may contribute to leukemogenesis of childhood ALL and confer increased risk of treatment failure but are associated with other poor-risk features.

Apoptosis-inducing oxovanadium(IV) complexes of 1,10-phenanthroline against human ovarian cancer

In a systematic effort to identify a potent anticancer agent against human ovarian cancer, we synthesized 15 oxovanadium(IV) complexes, and examined their cytotoxic activity against human ovarian cancer cell lines PA-1, SKOV-3, ES-2 and OVCAR-3 using a MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyletetrazolium bromide]-based assay. The apoptosis-inducing ability of the oxovanadium compounds was evaluated by the two-color flow cytometric terminal deoxynucleotidyl transferase-based assay that labels 3'-hydroxyl ends of fragmented DNA (TUNEL) assay and confocal laser scanning microscopy. Notably, all eight oxovanadium complexes of 1,10 phenanthroline exhibited significant cytotoxicity and induced apoptosis within 24 h. The mono-chelated, VO(NO2-phen) and bis-chelated, VO(Me2-phen)2, VO(Cl-phen)2 and VO(NO2-phen)2 complexes were the most potent oxovanadium compounds, and killed target cancer cells at low micromolar concentrations. The marked differences in the cytotoxic activity of oxovanadium(IV) complexes containing different heterocyclic ancillary ligands suggest that the cytotoxic activity of these compounds is determined by the identity of the five-member bidentate ligands, as well as the nature of the substituents on the heterocyclic aromatic rings. Our results presented herein provide experimental evidence that oxovanadium compounds induce apoptosis in human ovarian cancer cells. The lead compounds, VO(Me2-phen)2 and VO(NO2-phen)2, may be useful in the treatment of ovarian cancer.

Structure-based drug design of non-nucleoside inhibitors for wild-type and drug-resistant HIV reverse transcriptase

The generation of anti-HIV agents using structure-based drug design methods has yielded a number of promising non-nucleoside inhibitors (NNIs) of HIV reverse transcriptase (RT). Recent successes in identifying potent NNIs are reviewed with an emphasis on the recent trend of utilizing a computer model of HIV RT to identify space in the NNI binding pocket that can be exploited by carefully chosen functional groups predicted to interact favorably with binding pocket residues. The NNI binding pocket model was used to design potent NNIs against both wild-type RT and drug-resistant RT mutants. Molecular modeling and score functions were used to analyze how drug-resistant mutations would change the RT binding pocket shape, volume, and chemical make-up, and how these changes could affect inhibitor binding. Modeling studies revealed that for an NNI of HIV RT to be active against RT mutants such as the especially problematic Y181C RT mutant, the following features are required: (a) the inhibitor should be highly potent against wild-type RT and therefore capable of tolerating a considerable activity loss against RT mutants (i.e. a picomolar-level inhibitor against wild-type RT may still be effective against RT mutants at nanomolar concentrations), (b) the inhibitor should maximize the occupancy in the Wing 2 region of the NNI binding site of RT, and (c) the inhibitor should contain functional groups that provide favorable chemical interactions with Wing 2 residues of wild-type as well as mutant RT. Our rationally designed NNI compounds HI-236, HI-240, HI-244, HI-253, HI-443, and HI-445 combine these three features and outperform other anti-HIV agents examined.

Three leflunomide metabolite analogs

The title compounds, 1-cyano-2-hydroxy-N-[4-(methylsulfonyl)phenyl]but-2-enamide, C(12)H(12)N(2)O(4)S, PHI492, 1-cyano-2-hydroxy-N-[3-(methylsulfonyl)phenyl]but-2-enamide, C(12)H(12)N(2)O(4)S, PHI493, and N-[3-bromo-4-(trifluoromethoxy)phenyl]-1-cyano-2-hydroxybut-2-e namide , C(12)H(8)BrF(3)N(2)O(3), PHI495, are potent inhibitors of Bruton's tyrosine kinase (BTK). The molecular structures of these compounds are similar and they display similar hydrogen-bonding networks and crystal packing. Examination of the crystal-packing interaction in the three compounds reveals an alternating direction of adjacent molecules in the crystalline lattice due to intermolecular cyano-amide hydrogen bonding. PHI492, a positional isomer of PHI493, does not form intermolecular O-H.O hydrogen bonds between molecules and crystallizes in a space group different from that of PHI493 and PHI495. The aromatic ring and the amide group of each molecule form a conjugated pi-system which ensures planarity, with further stabilization gained from intramolecular O-H.O hydrogen bonds.

SPIKET and COBRA compounds as novel tubulin modulators with potent anticancer activity

Agents that either promote or inhibit tubulin polymerization exhibit anticancer activity by disrupting normal mitotic spindle assembly and cell division as well as inducing apoptosis. Recently identified novel agents that target tubulin include synthetic spiroketal pyrans (SPIKET), targeting the spongistatin binding site of beta-tubulin, and COBRA compounds, targeting a unique binding cavity on alpha-tubulin. At nanomolar concentrations, the SPIKET compound SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells. Molecular modeling studies predicted a high-affinity interaction of the first COBRA compounds, COBRA-0 and COBRA-1, with a unique hydrophobic binding site on alpha-tubulin located between the GTP/GDP binding site and the M-loop. Further studies showed that COBRA-1 inhibited GTP-induced tubulin polymerization in cell-free tubulin turbidity assays. Treatment of human breast cancer and brain tumor (glioblastoma) cells with COBRA-1 caused destruction of microtubule organization and apoptosis. COBRA-1 activated the pro-apoptotic c-Jun N-terminal kinase (JNK) signal transduction pathway. COBRA and SPIKET compounds represent two new classes of tubulin targeting agents that show promise as anticancer drugs.

An inhibitor of Janus kinase 3:4-(4-hydroxyphenylamino)-6, 7-dimethoxyquinazolin-1-ium chloride methanol solvate

The crystal structure of the title compound, C(16)H(16)N(3)O(3)(+). Cl(-).CH(4)O (WHI-P131, an inhibitor of Janus kinase 3), contains four hydrogen bonds. There are two hydrogen bonds within the asymmetric unit, i.e. interactions between WHI-P131 OH and Cl(-), and between methanol and Cl(-). There is a third interaction between WHI-P131 NH and Cl(-) (related by a 2(1) screw) and a fourth between WHI-P131 NH and methanol (related by an n-glide). The hydrogen-bond pattern for these interactions can be described by the first-level hydrogen-bond graph-set notation D(1)(1)(2)D(1)(1)(2)D(1)(1)(2)D(1)(1)(2). The second-level graph-set notation (for combinations of two hydrogen bonds) was determined to be D(1)(2)(3)D(1)(2)(3)D(2)(2)(4)D(2)(2)(9)D(2)(2)(14)C(1)(2)(9).

Cathepsin inhibition induces apoptotic death in human leukemia and lymphoma cells

We examined the effects of cathepsin inhibitor 1 (CATI-1), a selective inhibitor of cysteine cathepsins, on human leukemia and lymphoma cells. CATI-1 induced apoptosis in all 12 cell lines tested. Apoptosis of CATI-1-treated leukemia/lymphoma cells was caspase-independent, p53-independent, BAX-independent as well as MAP kinase-independent. Our findings provide unprecedented experimental evidence that cathepsins play a pivotal role for the survival of human leukemia/lymphoma cells. Therefore, cathepsin inhibitors may provide the basis for new treatment programs against leukemia and lymphoma.

Stereochemistry of halopyridyl and thiazolyl thiourea compounds is a major determinant of their potency as nonnucleoside inhibitors of HIV-1 reverse transcriptase

Chiral derivatives of two cyclohexylethyl halopyridyl thiourea compounds (HI-509 and HI-510), two alpha-methyl benzyl halopyridyl compounds (HI-511 and HI-512), and a cyclohexyl ethyl thiazolyl thiourea compound (HI-513) were synthesized as nonnucleoside inhibitors (NNI) of human immunodeficiency virus (HIV) reverse transcriptase (RT). The R stereoisomers of all five compounds inhibited the recombinant RT in vitro with 100-fold lower IC50 values. HI-509R, HI-510R, HI-511R, HI-512R and HI-513R were active anti-HIV agents and inhibited HIV-1 replication in human peripheral blood mononuclear cells at nanomolar concentrations, whereas their enantiomers were inactive. Each of these five compounds was also active against NNI-resistant HIV-1 strains, with HI-511R being the most active agent. When tested against the NNI-resistant HIV-1 strain A17 with a Y181C mutation in RT, HI-511R was found to be 10,000-times more active than nevirapine, 5000-times more active than delavirdine, and 50-times more active than trovirdine. HI-511 R inhibited the HIV-strain A17 variant, containing RT mutations Y181C plus K103N, with an IC50 value of 2.7 microM, whereas the IC50 values of nevirapine, delavirdine, and trovirdine against this highly NNI-resistant HIV-1 strain were >100 microM.

Piperidinylethyl, phenoxyethyl and fluoroethyl bromopyridyl thiourea compounds with potent anti-HIV activity

Derivatives of piperidinylethyl, phenoxyethyl and fluoroethyl bromopyridyl thioureas were designed and synthesized as non-nucleoside reverse transcriptase inhibitors (NNRTIs) of HIV-1 reverse transcriptase (RT). The anti-HIV activity of these compounds was examined by determining their ability to inhibit the replication of the HIV-1 strain HTLV(IIIB) in human peripheral blood mononuclear cells. The unsubstituted parent pyridyl thiourea compound N-[2-(1-piperidine)ethyl]-N'-[2-(pyridyl)] thiourea (1) exhibited no anti-HIV activity, even at 100 microM. However, the thiourea derivatives that contain a bromo- or chloro-substituted pyridyl group, compounds 2 and 5, inhibited HIV-1 replication at nanomolar concentrations. The addition of a methyl group onto the piperidine ring significantly altered the potency of these compounds; while methyl substitution at the 3-position of the piperidine ring reduced the activity, methyl substitution at the 2-position enhanced the anti-HIV activity. The IC50 value of the lead piperidinyl compound, N-[2-(2-methylpiperidinylethyl)]-N'-[2-(5-bromopyridyl)] thiourea (4) was <0.001 microM. All three phenoxyethyl derivatives, including the unsubstituted parent phenoxyethyl pyridyl thiourea compound N-[2-(phenoxy)ethyl]-N'-[2-(pyridyl)]thiourea (8) and the bromo-/chloro-substituted phenoxyethyl halopyridyl thiourea compounds N-[2-(phenoxy)ethyl]-N'-[2-(5-chloropyridyl)]thiourea (9) and N-[2-(phenoxy)ethyl]-N'-[2-(5-bromopyridyl)]thiourea (10) exhibited potent anti-HIV activity with nanomolar IC values. The corresponding fluoroethyl halopyridyl thiourea compounds beta-fluoro[2-phenethyl]-N'[2-(5-chloropyridyl)]thiourea (11) and beta-fluoro[2-phenethyl]-N'[2-(5-bromopyridyl)]thiourea (12) inhibited HIV-1 replication in PBMC with subnanomolar IC50 values and selectivity indices >30000. Compared to the corresponding phenoxyethyl thiourea compounds 9 and 10, these compounds were >4-5-fold more active as anti-HIV agents. Notably, the lead fluorothiourea compounds 11 and 12 were both substantially more active against the NNRTI-resistant HIV strains RT-MDR (V106A) and A17 (Y181C) than nevirapine or delavirdine. Taken together, our results provide additional experimental evidence that the structural features of the 'linker unit' between the pyridyl and phenyl moieties and changes in the phenyl group of PETT-related thiourea compounds significantly affects their biological activity as NNRTIs of HIV-1 RT.

X-ray crystallographic analysis of pokeweed antiviral protein-II after reductive methylation of lysine residues

Pokeweed antiviral protein II (PAP-II) is a naturally occurring protein isolated from early summer leaves of the pokeweed plant (Phytolacca americana). PAP-II belongs to a family of ribosome-inactivating proteins which catalytically deadenylate ribosomal and viral RNA. The chemical modification of PAP-II by reductive methylation of its lysine residues significantly improved the crystal quality for X-ray diffraction studies. Hexagonal crystals of the modified PAP-II, with unit cell parameters a = b = 92.51 A, c = 79.05 A, were obtained using 1.8 M Na/K phosphate as the precipitant. These crystals contained one enzyme molecule per asymmetric unit and diffracted up to 2.4 A, when exposed to a synchroton source.

Residual bone marrow leukemic progenitor cell burden after induction chemotherapy in pediatric patients with acute lymphoblastic leukemia

We used highly sensitive multiparameter flow cytometry and blast colony assays to quantify the leukemic progenitor cell (LPC) burden of postinduction chemotherapy bone marrows from newly diagnosed and relapsed pediatric patients with acute lymphoblastic leukemia (ALL). Of 890 newly diagnosed patients, 243 (27%) had detectable LPC in the postinduction bone marrow samples with an average (mean +/- SE) LPC content of 22+/-9 LPC/10(6) mononuclear cell (MNC; range, 0-7199/10(6) MNC; median, 0/10(6) MNC). By comparison, 24 of 50 (48%) patients with relapsed ALL had detectable LPC in their postinduction bone marrow specimens (P = 0.003), and their average LPC content was 202+/-139 LPC/10(6) MNC. Fewer patients with B-lineage ALL (170 of 786; 22%) than patients with T-lineage ALL (73 of 104; 70%) harbored residual LPC in their postinduction bone marrow specimens (P < 0.0001). This correlation with immunophenotype was independent of the National Cancer Institute risk classification. Similarly, 19 of 44 (43%) patients with relapsed B-lineage ALL versus 5 of 6 (83%) patients with relapsed T-lineage ALL harbored residual LPC in their postinduction bone marrow specimens (P = 0.09). Among newly diagnosed patients, those with high-risk ALL seemed to have larger numbers of residual LPC in their bone marrow after induction chemotherapy than those with standard risk ALL (53+/-26, n = 286 versus 7+/-1, n = 604, P = 0.04). LPC of patients with standard risk ALL who had a slow early marrow response at day 7 seemed to be more resistant to the three-drug induction chemotherapy than patients who had a rapid early marrow response. Overall, the order of chemosensitivity of LPC was: newly diagnosed standard risk B-lineage > newly diagnosed higher risk B-lineage > newly diagnosed standard risk T-lineage > newly diagnosed higher risk T-lineage > relapsed B-lineage > relapsed T-lineage. Notably, LPC- patients whose end-of-induction remission bone marrow specimens had zero LPC had an excellent early event-free survival outcome. Within the standard and high-risk subsets, LPC- patients had a 2.6-fold lower and 2.4-fold lower incidence of events, respectively, than LPC+ patients. At 6 months, 12 months, as well as 24 months, the ranking order for better event-free survival was: standard risk, LPC- > high risk, LPC- > standard risk, LPC+ > high risk, and LPC+.

Role of PRKCM (PKCmu) in radiation-induced increase of JUN proto-oncogene mRNA levels in B-lineage lymphoid cells

Exposure of cells to ionizing radiation results in both activation of protein kinase C (PRKC, also known as PKC) and induction of transcription of the JUN proto-oncogene. PRKC plays a pivotal role in radiation-induced JUN expression, since inhibition of PRKC abrogates the JUN signal. However, the specific PRKC isoforms involved in radiation-induced elevation of JUN mRNA levels have not been identified. Here we demonstrate that in DT40 B-lineage lymphoid cells, the mu isoform of PRKC (PRKCM) is critical for the response of JUN to ionizing radiation. The zinc chelator, 1, 10-phenanthroline, abrogated induction of JUN after exposure to ionizing radiation, indicating that this PRKCM-mediated response is also dependent on zinc.

Vanadocene-mediated in vivo male germ cell apoptosis

Vanadocenes are potent apoptosis-inducing cytotoxic agents against human testicular cancer cells in vitro. The present study investigated the ability of four vanadocenes-vanadocene diazide (VDA), vanadocene dicyanate (VDCN), vanadocene dioxycyanate (VDOCN), and vanadocene monochloro oxycyanate (VDCO)-to induce male germ cell apoptosis in vivo in mouse testes by repetitive intratesticular injection of vanadocenes (7.5 mg/kg/testis) for 28 days. Germ cell loss in vivo was measured by epididymal sperm count, testes weights, and histologic evaluation of the testes. Repetitive intratesticular injection of vanadocenes led to decreased sperm counts and reduced testicular weights. Histopathological examination revealed seminiferous tubular atrophy, inhibition of spermatogenesis, and the preferential loss of maturing and elongated spermatids. In situ evaluation by the terminal deoxynucleotidyl transferase-mediated FITC-deoxyuridine triphosphate nick-end labeling (TUNEL) of seminiferous tubule cross sections and laser confocal microscopy showed characteristic apoptotic cells identified primarily as pachytene spermatocytes delineating the periphery of the seminiferous tubules. The ability of vanadocenes to induce germ cell apoptosis in vivo may have potential utility in the treatment of testicular seminomas in humans.

Highly sensitive liquid chromatography-electrospray mass spectrometry (LC-MS) method for the determination of etoposide levels in human serum and plasma

Etoposide is one of the most commonly used antineoplastic agents. A highly sensitive liquid chromatography-electrospray mass spectrometry (LC-MS) method was developed for the determination of etoposide in human serum and plasma. Etoposide was extracted with chloroform and extracts were reconstituted in acetonitrile followed by the evaporation of chloroform with nitrogen gas. Etoposide was separated using Lichospher 100 RP-18 (5 microm) column (250 mmx4 mm) with the mobile phase of acetonitrile-water containing 0.1% acetic acid (45/55, v/v) at flow-rate of 0.5 ml/min. Selected-ion monitoring (SIM) mode was performed on m/z 589 (positive ion mode) using a fragmentor of 75 V. Good linearity (r>0.9965) was observed between concentrations of 0.0125-5 microM in 200 microl serum and 0.01-10 microM in 100 microl plasma. Intra- and inter-assay variabilities were less than 7% and the lowest detection limit of etoposide was 0.005 microM in both serum and plasma at a signal-to-noise ratio of approximately 4. The etoposide concentrations in four cancer patients treated with etoposide are also presented to demonstrate the clinical utility of this new method, which should aid the pharmacokinetically guided use of etoposide in clinical settings.

Novel thiourea compounds as dual-function microbicides

Sexually active women represent the fastest growing human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome risk group. In an effort to develop a vaginal microbicidal contraceptive potentially capable of preventing HIV transmission as well as providing fertility control, we previously reported the synthesis of novel nonnucleoside inhibitors (NNIs) of HIV-1 reverse transcriptase with sperm-immobilizing activity (SIA). To gain further insight into the structure-function relationship controlling these two properties of NNIs, we have rationally designed and synthesized 30 novel thiourea compounds and examined them for dual-function, anti-HIV and spermicidal activity. Twelve of the 30 thiourea compounds exhibited potent anti-HIV activity in the nanomolar range (IC(50) = <1-9 nM). Nine of the 30 thiourea derivatives exhibited both anti-HIV and spermicidal activity. Among the phenyl ring-containing thioureas, the 2-fluoro (HI-240) -substituted and 2-chloro (HI-253) -substituted derivatives exhibited potent anti-HIV activity (IC(50) = <1 nM) with SIA (EC(50) = 70 microM and 147 microM). Among the alicyclic ring-containing thioureas, the 5-bromo (HI-346) and 5-chloro (HI-445) functionalized cyclohexenyl ring-substituted thioureas were the most potent dual-function spermicides (EC(50) = 42 and 57 microM), with anti-HIV activity at nanomolar range (IC(50) = 3 nM). Unlike nonoxynol-9 (N-9), none of the potent dual-function thiourea compounds were cytotoxic to normal human vaginal, ectocervical, and endocervical epithelial cells at spermicidal concentrations. We conclude that as potent anti-HIV agents with SIA and reduced cytotoxicity when compared with N-9, the phenyl-substituted and cyclohexenyl-substituted thiourea derivatives, especially compounds HI-253 (N-[2-(2-chlorophenethyl)]-N'-[2-(5-bromopyridyl)-thiourea), HI-346 (N-[2-(5-bromopyridinyl)]-N'-[2-(1-cyclohexenyl)ethyl-thiourea), and HI-445 (N-[2-(5-chloropyridinyl)]-N'-[2-(1-cyclohexenyl)ethyl-thiourea) show unique clinical potential to become the active ingredients of a vaginal contraceptive for women who are at high risk for acquiring HIV by heterosexual vaginal transmission.

Evaluation of subchronic (13-week) and reproductive toxicity potential of intravaginal gel-microemulsion formulation of a dual-function phenyl phosphate derivative of bromo-methoxy zidovudine (compound whi-07) in B(6)C(3)F(1) mice

Heterosexual transmission of human immunodeficiency virus (HIV) accounts for 90% of all new infections worldwide and significantly contributes to new acquired immunodeficiency syndrome (AIDS) cases in the USA. In a systematic effort to develop a microbicidal contraceptive capable of preventing HIV transmission as well as providing fertility control, we previously identified novel phenyl phosphate derivatives of 3'-azido-3'-deoxythymidine (zidovudine) that exhibit potent anti-HIV and spermicidal activities. This study reports the preclinical studies of our lead compound WHI-07, 5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-bromophenyl) methoxyalaninyl phosphate, for use as a dual-function topical microbicide. In vivo toxicity studies in non-human primates and rodents given WHI-07 (20 mg kg(-1)) intravenously and intraperitonealy, respectively, had no detectable adverse effects on hematological and clinical chemistry profiles. The 13-week subchronic and reproductive toxicity potential of an intravaginal gel-microemulsion formulation of WHI-07 was studied in mice to support its further development as a dual-function microbicide. Groups of ten female B(6)C(3)F(1) mice were exposed intravaginally to a gel-microemulsion formulation containing 0, 0.5, 1.0 or 2.0% WHI-07, 5 days a week, for 13 consecutive weeks. On a molar basis, these concentrations represent 1400-5700 times their in vitro spermicidal potency EC(50)) and 1.4 x 10(6)-5.7 x 10(6) times their in vitro anti-HIV activity(50)). After 13 weeks of intravaginal treatment, half of the treated mice were evaluated for toxicity and the other half were mated with untreated males to evaluate potential reproductive and developmental effects. The endpoints that were evaluated included survival, body weight gain, hematological and clinical chemistries, absolute and relative organ weights and histopathology. The WHI-07 applications did not cause weight loss, morbidity, mortality or specific tissue lesions detectable by histopathology. Repeated intravaginal exposure of mice to WHI-05 for 13 weeks had no adverse effects on subsequent reproductive performance (100% fertile), neonatal survival (>95%) or pup development. These findings collectively show that the experimental dual-function anti-HIV and contraceptive agent WHI-07 did not cause significant acute or subchronic toxicity.

COBRA-1, a rationally-designed epoxy-THF containing compound with potent tubulin depolymerizing activity as a novel anticancer agent

A novel mono-THF containing synthetic anticancer drug, COBRA-1, was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of alpha-tubulin. COBRA-1 inhibited GTP-induced tubulin polymerization in cell-free tubulin turbidity assays. Treatment of human breast cancer and brain tumor (glioblastoma) cells with COBRA-1 caused destruction of microtubule organization and apoptosis. Like other microtubule-interfering agents, COBRA-1 activated the proapoptotic c-Jun N-terminal kinase (JNK) signal transduction pathway, as evidenced by rapid induction of c-jun expression.

Calpain inhibitor II induces caspase-dependent apoptosis in human acute lymphoblastic leukemia and non-Hodgkin's lymphoma cells as well as some solid tumor cells

Calpain is a calcium-dependent cysteine protease that is implicated in calcium-dependent cell death, and calpain inhibitors are generally considered as inhibitors of apoptosis. To the contrary, in the present study, we found that calpain inhibitor II (CPI-2) triggers rapid apoptosis in acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL) cells. All target cell lines were killed by CPI-2, including: ALL-1, a multidrug-resistant BCR-ABL fusion transcript-positive t(9;22) pro-B ALL cell line; RS4;11, a highly radiation-resistant MLL-AF4 fusion transcript-positive t(4;11) pre-pre B ALL cell line; RAMOS, a highly radiation-resistant and p53-deficient Burkitt's lymphoma cell line; DAUDI, a Burkitt's leukemia/lymphoma cell line; NALM-6, a pre-B ALL cell line; and JURKAT and MOLT-3, two T-lineage ALL/NHL cell lines. CPI-2-induced apoptosis in LYN-deficient and BTK-deficient subclones of the DT-40 lymphoma B cell line as effectively as it did in wild-type DT-40 cells. Thus, CPI-2-induced apoptosis is not dependent on the protein tyrosine kinases LYN or BTK. Notably, caspase inhibitor I effectively inhibited CPI-2-induced apoptosis, suggesting that the inhibition of a CPI-2-susceptible protease results in caspase activation, leading to apoptosis in ALL/NHL cells. Unlike the high calpain-expressing ALL/NHL cell lines, myeloid leukemia cell lines HL-60/AML, K562/CML, and U937/AMML, or solid tumor cell lines BT-20/breast cancer, PC-3/prostate cancer, U373/glioblastoma, and HeLa/epitheloid cancer, were not susceptible to the cytotoxicity of CPI-2. Taken together, our results identify calpain as a new molecular target for the treatment of ALL and NHL. CPI-2 and its analogues represent a promising new class of antileukemia/lymphoma agents that deserves further development.

A rationally designed anticancer drug targeting a unique binding cavity of tubulin

A novel mono-THF containing synthetic anticancer drug (WHI-261) was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of tubulin. The anti-cancer activity of WHI-261 was confirmed using MTT assays. The structure-based design, synthesis, and biological activity of WHI-261 are reported.

Prognostic impact of trisomies of chromosomes 10, 17, and 5 among children with acute lymphoblastic leukemia and high hyperdiploidy (> 50 chromosomes)

PURPOSE

Children with acute lymphoblastic leukemia (ALL) and high hyperdiploidy (> 50 chromosomes) have improved outcome compared with other ALL patients. We sought to identify cytogenetic features that would predict differences in outcome within this low-risk subset of ALL patients.

MATERIALS AND METHODS

High-hyperdiploid ALL patients (N = 480) were enrolled between 1988 and 1995 on Children's Cancer Group (CCG) trials. Karyotypes were determined by conventional banding. Treatment outcome was analyzed by life-table methods.

RESULTS

Patients with 54 to 58 chromosomes had better outcome than patients with 51 to 53 or 59 to 68 chromosomes (P = .0002). Patients with a trisomy of chromosome 10 (P<.0001), chromosome 17 (P = .0002), or chromosome 18 (P = .004) had significantly improved outcome compared with their counterparts who lacked the given trisomy. Patients with a trisomy of chromosome 5 had worse outcome than patients lacking this trisomy (P = .02). Patients with trisomies of both chromosomes 10 and 17 had better outcome than those with a trisomy of chromosome 10 (P = .09), a trisomy of chromosome 17 (P =.01), or neither trisomy (P<.0001). Multivariate analysis indicated that trisomy of chromosome 10 (P = .001) was the most significant prognostic factor for high-hyperdiploid patients, yet trisomy of chromosome 17 (P =.02) or chromosome 5 (P = .01) and modal chromosome number (P = .02) also had significant multivariate effects.

CONCLUSION

Trisomy of chromosomes 10 and 17 as well as modal chromosome number 54 to 58 identify subgroups of patients with high-hyperdiploid ALL who have a better outcome than high-hyperdiploid patients who lack these cytogenetic features. Trisomy of chromosome 5 confers poorer outcome among high-hyperdiploid patients.

Z-Phe-Gly-NHO-Bz, an inhibitor of cysteine cathepsins, induces apoptosis in human cancer cells

An increasing number of studies indicate that cysteine cathepsins contribute to cancer progression, invasion, and metastasis. Here we provide experimental evidence that the cathepsin inhibitor Z-Phe-Gly-NHO-Bz induces rapid apoptotic death in human cancer cell lines. Notably, the Z-Phe-Gly-NHO-Bz-induced apoptosis exhibited independence of p53, caspases, and mitogen-activated protein (MAP) kinases. Taken together, our results prompt the hypothesis that cysteine cathepsin(s) is a universal survival factor for cancer cells, and its inhibition leads to cancer cell apoptosis. The exquisite sensitivity of human cancer cells to CATI-1 indicates that this compound and its derivatives may provide the basis for new treatment programs against a broad spectrum of malignancies.

Evaluation of boar sperm as a model system to study the mechanism of spermicidal activity of vanadocenes

bis-cyclopentadienyl [Cp] complexes of vanadium(IV) or vanadocenes are rapid and potent inhibitors of human sperm motility with potential as a new class of contraceptive agents. We investigated the utility of boar sperm as a model system to study the mechanisms of drug action because boar sperm lacks phosphocreatine and creatine kinase activity, the essential components of the "phosphagen shuttle" system for human sperm motility. Two representative vanadocenes, vanadocene dichloride [VDC] and bis[pentamethylcyclopentadienyl] vanadium dichloride [VPMDC], in which the bis-Cp rings were substituted with five electron-donating methyl groups were evaluated. The concentration-dependent effects of VDC and VPMDC on spermicidal activity, axonemal dynein adenosine triphosphatase (ATPase) activity, and tyrosine phosphorylation of global sperm proteins were assessed by computer-assisted sperm analysis, spectrophotometry, and immunoblotting, respectively. Both the unsubstituted and the pentamethyl-substituted vanadocene induced rapid sperm immobilization (T(1/2) < 15 s). Substitution of the bis-Cp rings by five methyl groups augmented the SIA of VDC threefold. The EC(50) values for VDC and VPMDC were 2.1 and 0.76 microM, respectively. Spermicidal activity of vanadocenes was not associated with the inhibition of dynein ATPase(s) or increase in tyrosine phosphorylation of sperm proteins. These results suggest that the potent spermicidal activity of vanadocenes against boar sperm is mediated by a unique mechanism that is independent of dynein ATPase activity, phosphatase activity, and phosphocreatine/creatine kinase system. Therefore, boar sperm is a suitable model for further investigating the molecular mechanism of spermicidal action of vanadocenes.

Prognostic significance of cytogenetic abnormalities of chromosome arm 12p in childhood acute lymphoblastic leukemia: a report from the Children's Cancer Group

BACKGROUND

The authors have determined the prognostic significance of cytogenetically detectable 12p abnormalities, which are frequent in children with acute lymphoblastic leukemia (ALL), in a large cohort of patients treated on risk-adjusted protocols of the Children's Cancer Group (CCG).

METHODS

The presence of an abnormal 12p was identified among 1880 children with newly diagnosed ALL; outcome was assessed by standard life table methods.

RESULTS

A total of 174 cases (9%) had cytogenetically detectable 12p abnormalities; the majority of cases had a balanced translocation, a del(12p), or an add(12p). In the overall cohort, event free survival (EFS) at 6 years was similar for patients with or without a 12p abnormality (76%, SD = 6%, vs. 75%, SD = 2%, respectively; P = 0.60). Among patients with pseudodiploidy, an abnormal 12p conferred improved outcome (P = 0.008; relative risk = 0.51; 95% confidence interval [CI], 0.31-0.85). There was a trend for improved EFS for those with abnormalities in both chromosome 12 homologues (P = 0.16; relative risk = 0.39; 95% CI, 0.10-1.55) and those with low hyperdiploidy (P = 0.07; relative risk = 0.44; 95% CI, 0.18-1.09). Among T-lineage ALL patients, there was a trend for worse outcome for abnormal versus normal 12p (P = 0.14; relative risk = 1.97; 95% CI, 0.78-4.93). There was no difference in EFS for the 12 patients with a dic(9;12) compared with patients lacking an abnormal 12p.

CONCLUSIONS

These data suggest that although a cytogenetically detectable 12p aberration is a favorable risk factor for children with ALL and pseudodiploidy, it is not prognostic for the overall group of pediatric ALL patients treated with contemporary therapies of the CCG.

Bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(IV) as a novel apoptosis-inducing anticancer agent

In a systematic effort to identify a potent anticancer agent, we synthesized 15 oxovanadium(IV) complexes and examined their cytotoxic activity against 14 different human cancer cell lines. The oxovanadium compounds included mono and bis ancillary ligands of 1,10-phenanthroline (phen) [VO(phen), VO(phen)2, VO(Me2-phen), VO (Me2-phen)2, VO(Cl-phen), VO(Cl-phen)2, VO(NO2-phen), VO(NO2-phen)2], 2,2'-bipyridyl (bipy) [VO(bipy), VO(bipy)2, VO(Me2-bipy), VO(Me2-bipy)2], and 2-2'-bipyrimidine(bipym) [VO(bipym) and VO-(bipym)2], linked via nitrogen atoms, and 5'-bromo-2'-hydroxyacetophenone (acph) [VO(acph)2], linked via oxygen donor atom. The mono-chelated [VO(Me2-phen), compound 3] and bis-chelated-phen[VO(Me2-phen)2, compound 4] complexes were the most potent oxovanadium compounds and killed target cancer cells at low micromolar concentrations. Notably, the dimethyl substitution of the phenanthroline rings was essential for the anticancer activity of both compound 4 [VO(Me2-phen)2] and compound 3 [VO(Me2-phen)] because unsubstituted bis-chelated and mono-chelated phen oxovanadium(IV) complexes [VO(phen), compound 1, or VO(phen)2, compound 2] were less active. Addition of a chloro or nitro group to the phen complexes did not significantly improve the cytotoxic activity of the unsubstituted oxovanadium(IV) complexes. Irrespective of the ligands, bis-chelated phenanthroline containing compounds showed better activity than the mono-chelated phenanthroline containing complexes. The marked differences in the cytotoxic activity of oxovanadium(IV) complexes containing different heterocyclic ancillary ligands suggest that the cytotoxic activity of these compounds is determined by the identity of the five-member bidentate ligands, as well as the nature of the substitutents on the heterocyclic aromatic rings. Our results presented herein provide experimental evidence that oxovanadium compounds induce apoptosis in human cancer cells. Oxovanadium compounds, especially the lead compound VO(Me2-phen)2, may be useful in the treatment of cancer.