Areca nut, energy metabolism and hunger in Asian men

BACKGROUND

The nut of the Areca catechu palm has long been attributed effects on hunger and the digestive process.

OBJECTIVES

The objectives were to assess experimentally effects of areca nut on fasting and postprandial energy metabolism, substrate utilization and hunger.

SUBJECTS AND METHODS

Two randomized, placebo-controlled, double-blind studies were undertaken. In study 1, eight Indian men received bioadhesive gels delivering 0, 5, 10 or 20 mg arecoline to the buccal sulcus after an overnight fast. Resting energy expenditure and substrate utilization were determined by ventilated hood calorimetry over 6 h during which hunger was rated on five occasions. In study 2, 15 Indian men received gels delivering 0 or 10 mg arecoline after consuming a 2.5 MJ meal, and the same protocol was then applied as in study 1.

RESULTS

Fasting resting energy expenditures exceeded basal metabolic rate (BMR) by 5.4+/-0.8% (Mean+/-SE) after placebo, and 5.1+/-0.7% after 20 mg arecoline, but by 0.9+/-0.8% and 0.7+/-0.5% following 5 mg and 10 mg arecoline, respectively. Carbohydrate (CHO) utilization rates rose after areca nut compared to placebo (F(3,252)= 7.3, p< 0.001). Hunger varied across doses (chi(2) = 10.5, p < 0.02), being lowest after 10 mg and highest after 20 mg, and was influenced by interaction of dose with delta resting energy expenditure. In study 2, areca dose interacted with fat-free mass (FFM) to lower by 5.4+/-11.2% the thermic effect of a meal (F(1,28) = 4.9, p = 0.05), and retarded peak 'digestive-phase' thermogenesis by 60 min (F(1,58) = 5.7, p = 0.02). Postprandial delta CHO utilization was greater (F(1,28) = 4.5, p = 0.05), and hunger was lower (chi:(2) = 3.8, p = 0.05), after areca nut. The areca nut altered relationships of hunger to thermic effects of the meal, and to delta substrate utilization, in ways consistent with appetite suppression.

CONCLUSION

Areca nut constituents modulate metabolic signals regulating appetite in man. This concurs with customary belief.

Assessment of estrogenic activity in some common essential oil constituents

Estrogenic responses have not only been associated with endocrine function, but also with cognitive function. Several studies have indicated that estrogen replacement therapy has favourable effects on cognition, and may have potential in the prevention and treatment of Alzheimer's disease. Thus, ligands for the estrogen receptor, that have a better efficacy and adverse-effect profile than drugs currently available, require investigation. This study was undertaken to investigate the potential estrogenic activity of a number of essential oil constituents. Initially, estrogenic activity was determined by a sensitive and specific bioassay using recombinant yeast cells expressing the human estrogen receptor. At high concentrations, estrogenic activity was detected for citral (geranial and neral), geraniol, nerol and trans-anethole, while eugenol showed anti-estrogenic activity. Molecular graphics studies were undertaken to identify the possible mechanisms for the interaction of geranial, neral, geraniol, nerol and eugenol with the ligand-binding domain of the estrogen alpha-receptor, using the computer program HyperChem. Citral, geraniol, nerol and eugenol were also able to displace [(3)H]17beta-estradiol from isolated alpha- and beta-human estrogen receptors, but none of these compounds showed estrogenic or anti-estrogenic activity in the estrogen-responsive human cell line Ishikawa Var I at levels below their cytotoxic concentrations, and none showed activity in a yeast screen for androgenic and anti-androgenic activity. The potential in-vivo estrogenic effects of citral and geraniol were examined in ovariectomized mice, but neither compound showed any ability to stimulate the characteristic estrogenic responses of uterine hypertrophy or acute increase in uterine vascular permeability. These results show that very high concentrations of some commonly used essential oil constituents appear to have the potential to interact with estrogen receptors, although the biological significance of this is uncertain.

Resistance to rapamycin: a novel anticancer drug

The macrocyclic lactone rapamycin has an established place as an immune suppressive agent in organ transplantation. However, more recently it has been recognized as an inhibitor of pathways that may be activated during malignant transformation and tumor progression. Thus, increasing interest is being directed to this class of antibiotic as potential antitumor agents. Here we summarize the history, mechanism of action, and mechanisms of resistance to rapamycin.

In vitro antiplasmodial activity of extracts of Argentinian plants

Fifteen extracts from nine selected Argentine medicinal plants were tested for their antiplasmodial activity in vitro by assessing their ability to inhibit the uptake of [3H]-hypoxanthine into the Plasmodium falciparum K1 pyrimethamine/chloroquine resistant strain. The methanol extract of Satureja parvifolia showed good antiplasmodial activity (IC(50) 3 microg/ml). Inhibition of the growth of P. falciparum was also observed with aqueous extracts of Buddleja globosa and S. parvifolia.

Antimicrobial activities of a new schizozygane indoline alkaloid from Schizozygia coffaeoides and the revised structure of isoschizogaline

Extracts from Schizozygia coffaeoides showed antimicrobial activity against fungal and bacterial species. Alkaloids isolated using bioassay-guided fractionation were isoschizogaline, schizogynine, and a new indoline alkaloid, 7,8-dehydro-19beta-hydroxyschizozygine, shown to be the most active antifungal compound. The structure of isoschizagaline, the only active antibacterial, is revised on the basis of NMR analysis.

Salvia lavandulaefolia essential oil inhibits cholinesterase in vivo

The essential oil of Salvia lavandulaefolia at two dosage levels was administered orally to rats for five days. Choline esterase activity was measured post mortem in three areas of the brain, both in the absence and presence of TEPP, a specific butylcholine esterase inhibitor, and was found to be significantly reduced in the striatum with both doses and also in the hippocampus at the higher dose. The activity of the enzyme in the cortex was not significantly reduced even at the higher dose. Thus it appears that S. lavandulaefolia oil, shown to inhibit choline esterase in vitro, also has an in vivo effect and this may help explain its traditional use for ailing memory.

Mechanisms of resistance to rapamycins

Rapamycins represent a novel family of anticancer agents, currently including rapamycin and its derivatives, CCI-779 and RAD001. Rapamycins inhibit the function of the mammalian target of rapamycin (mTOR), and potently suppress tumor cell growth by arresting cells in G1 phase or potentially inducing apoptosis of cells, in culture or in xenograft tumor models. However, recent data indicate that genetic mutations or compensatory changes in tumor cells influence the sensitivity of rapamycins. First, mutations of mTOR or FKBP12 prevent rapamycin from binding to mTOR, conferring rapamycin resistance. Second, mutations or defects of mTOR-regulated proteins, including S6K1, 4E-BP1, PP2A-related phosphatases, and p27(Kip1) also render rapamycin insensitivity. In addition, the status of ATM, p53, PTEN/Akt and 14-3-3 are also associated with rapamycin sensitivity. To better explore the role of rapamycins against tumors, this review will summarize the current knowledge of the mechanism of action of rapamycins, and progress in understanding mechanisms of acquired or intrinsic resistance.

Activity of irofulven (6-hydroxymethylacylfulvene) in the treatment of glioblastoma multiforme-derived xenografts in athymic mice

PURPOSE

This study was conducted to define the activity of irofulven in the treatment of a series of xenografts derived from human glioblastoma multiforme growing subcutaneously and intracranially in athymic nude mice.

METHODS

Athymic mice bearing subcutaneous or intracranial tumors were treated with irofulven at a 10% lethal dose with responses compared to tumor-bearing mice treated with drug vehicle.

RESULTS

Irofulven was active against all tumor lines tested with growth delays ranging from 5.6 to 81.6 days (all values statistically significant, P < or = 0.001). Irofulven also produced a statistically significant (P < or = 0.001) increase in the median survival of mice bearing D-456 intracranial xenografts with a 162% increase in median survival.

CONCLUSIONS

Irofulven is active in a spectrum of human glioblastoma multiforme-derived xenografts and evaluation in patients with this neoplasm is warranted.

Effects of Buddleja globosa leaf and its constituents relevant to wound healing

An aqueous extract of Buddleja globosa leaves, used traditionally in Chile for wound healing, was tested for the ability to stimulate growth of fibroblasts in vitro and for antioxidant activity in the same fibroblast cell system challenged with hydrogen peroxide. Low concentrations of the extract gave an increase in fibroblast growth which was not statistically significant but cytotoxicity was observed at concentrations greater than 50 microg/ml. The extract showed strong antioxidant effect and fractionation led to the isolation of three flavonoids and two caffeic acid derivatives, each of which was shown to contribute to the antioxidant effect at concentrations below 10 microg/ml. These activities would accelerate the healing of wounds.

In-vitro activity of S. lavandulaefolia (Spanish sage) relevant to treatment of Alzheimer's disease

Salvia lavandulaefolia Vahl. (Spanish sage) essential oil and individual monoterpenoid constituents have been shown to inhibit the enzyme acetylcholinesterase in-vitro and in-vivo. This activity is relevant to the treatment of Alzheimer's disease, since anticholinesterase drugs are currently the only drugs available to treat Alzheimer's disease. Other activities relevant to Alzheimer's disease include antioxidant, anti-inflammatory and estrogenic effects. Results of in-vitro tests for these activities are reported here for S. lavandulaefolia extracts, the essential oil and its major constituents. Antioxidant activity (inhibition of bovine brain liposome peroxidation) was found in the EtOH extract of the dried herb (5 mg mL(-1)) and the monoterpenoids (0.1 M) alpha- and beta-pinene and 1,8-cineole. Thujone and geraniol had lower antioxidant effects, while camphor had no antioxidant effects. Possible anti-inflammatory activity (eicosanoid inhibition in rat leucocytes) was found in the EtOH extract (50 microg mL(-1)) and was shown by the monoterpenoids alpha-pinene and geraniol (0.2 mM), but not 1,8-cineole, thujone or camphor. Possible estrogenic activity (via induction of beta-galactosidase activity in yeast cells) was found in the essential oil (0.01 mg mL(-1)) and the monoterpenoid geraniol (0.1-2 mM). 1,8-Cineole, alpha- and beta-pinene and thujone did not exhibit estrogenic activity in this analysis. These results demonstrate that S. lavandulaefolia, its essential oil and some chemical constituents have properties relevant to the treatment of Alzheimer's disease and provide further data supporting the value of carrying out clinical studies in patients with Alzheimer's disease using this plant species.

Topotecan-filgrastim combination is an effective regimen for mobilizing peripheral blood stem cells

We compared the efficacy, toxicity, and cost of topotecan-filgrastim and filgrastim alone for mobilizing peripheral blood stem cells (PBSCs) in 24 consecutive pediatric patients with newly diagnosed medulloblastoma. PBSCs were mobilized with an upfront window of topotecan-filgrastim for 11 high-risk patients (residual tumor > or =1.5 cm2 after resection; metastases limited to neuraxis) and with filgrastim alone for 13 average-risk patients. All patients subsequently underwent craniospinal irradiation and four courses of high-dose chemotherapy with stem cell rescue. Target yields of CD34+ cells (> or =8 x 10(6)/kg) were obtained with only one apheresis procedure for each of the 11 patients treated with topotecan-filgrastim, but with a mean of 2.3 apheresis procedures for only six (46%) of the 13 patients treated with filgrastim alone (P = 0.0059). The median peak and median total yield of CD34+ cells were six-fold higher for the topotecan-filgrastim group (328/microl and 21.5 x 10(6)/kg, respectively) than for the filgrastim group (54/microl and 3.7 x 10(6)/kg, respectively). Mean times to neutrophil and platelet engraftment were similar. Myelosuppression was the only grade 4 toxicity associated with topotecan-filgrastim mobilization and lasted a median of 5 days. Compared with filgrastim mobilization, topotecan-filgrastim mobilization resulted in a mean cost saving of $3966 per patient. Topotecan-filgrastim is an efficacious, minimally toxic, and cost-saving combination for PBSC mobilization.

Biochemical correlates of mTOR inhibition by the rapamycin ester CCI-779 and tumor growth inhibition

The rapamycin ester, CCI-779, potently inhibits cell growth in vitro, inhibits tumor growth in vivo, and is currently in Phase I clinical trials. To further understand the relationship between plasma systemic exposure and inhibition of the target Ser/Thr kinase, mTOR/FRAP, two assays have been developed. The first assay involves determination of the 4E suppressor protein (4E-BP1) bound to eukaryotic initiation factor 4E (eIF4E), and the second is direct Western analysis of phosphorylation of residue Thr(70) of 4E-BP1. Under normal growth conditions in vitro, rapamycin caused rapid association of 4E-BP1 with eIF4E within 1 h in Rh30 and GC(3) human tumor cells. Association was persistent up to 16 h. In mice, administration of rapamycin (5 or 20 mg/kg) caused rapid association of 4E-BP1 with eIF4E within 4 h in both human colon adenocarcinoma GC(3) and rhabdomyosarcoma Rh30 xenografts. Using phospho-specific antibody against Thr(70) of 4E-BP1, rapid and persistent dephosphorylation within 30 min of exposure to rapamycin was detected in Rh18 rhabdomyosarcoma cells. Evaluation of CCI-779 against Rh18 xenografts showed this tumor to be growth inhibited at daily dose levels of > or =8.7 mg/kg. Because immunoblotting may be more suitable for assaying tumor biopsy tissue, a "blinded" comparison between the effect of CCI-779 on Thr(70) phosphorylation and growth inhibition of human tumor xenografts was undertaken. Mice were treated daily for 5 days with CCI-779 (20 mg/kg/day) or with drug vehicle, and tumor diameters were measured. Tumors were excised 1 h after the final administration and frozen, and phospho Thr(70) was determined by Western blot analysis. The correlation coefficient for decreases in Thr(70) phosphorylation and growth inhibition was high (r(2), 0.99). The results indicate that an assay of decreases in phosphorylation of Thr(70) of 4E-BP1 may be a useful surrogate for determining the inhibition of mTOR activity in tumor specimens.

Antimicrobial activity of Newtonia hildebrandtii

Successive petroleum ether, dichloromethane and methanol extracts of Newtonia hildebrandtii stem bark were tested in vitro for their antifungal and antibacterial activity. The methanol extract was found to be the most effective against the tested pathogens.

p53/p21(CIP1) cooperate in enforcing rapamycin-induced G(1) arrest and determine the cellular response to rapamycin

The relationship between G(1) checkpoint function and rapamycininduced apoptosis was examined using two human rhabdomyosarcoma cell lines, Rh1 and Rh30, that express mutated p53 alleles. Serum-starved tumor cells became apoptotic when exposed to rapamycin, but were completely protected by expression of a rapamycin-resistant mutant mTOR. Exposure to rapamycin (100 ng/ml) for 24 h significantly increased the proportion of Rh1 and Rh30 cells in G(1) phase, although there were no significant changes in expression of cyclins D1, E, or A in drug-treated cells. To determine whether apoptosis was associated with continued slow progression through G(1) to S phase, cells were exposed to rapamycin for 24 h, then labeled with bromodeoxyuridine (BrdUrd). Histochemical analysis showed that >90% of cells with morphological signs of apoptosis had incorporated BRDURD: To determine whether restoration of G(1) arrest could protect cells from rapamycin-induced apoptosis, cells were infected with replication-defective adenovirus expressing either p53 or p21(CIP1). Infection of Rh30 cells with either Ad-p53 or Ad-p21, but not control virus (Ad-beta-gal), induced G(1) accumulation, up-regulation of p21(CIP1), and complete protection of cells from rapamycin-induced apoptosis. Within 24 h of infection of Rh1 cells with Ad-p21, expression of cyclin A was reduced by >90%. Similar results were obtained after Ad-p53 infection of Rh30 cells. Consistent with these data, incorporation of [(3)H]thymidine or BrdUrd into DNA was significantly inhibited, as was cyclin-dependent kinase 2 activity. These data indicate that rapamycin-induced apoptosis in tumor cells is a consequence of continued G(1) progression during mTOR inhibition and that arresting cells in G(1) phase, by overexpression of p53 or p21(CIP1), protects against apoptosis. The response to rapamycin was next examined in wild-type or murine embryo fibroblasts nullizygous for p53or p21(CIP1). Under serum-free conditions, rapamycin-treated wild-type MEFs showed no increase in apoptosis compared to controls. In contrast, rapamycin significantly induced apoptosis in cells deficient in p53 ( approximately 2.4-fold) or p21(CIP1) ( approximately 5.5-fold). Infection of p53(-/-) MEFs with Ad-p53 or Ad-p21 completely protected against rapamycin-induced apoptosis. Under serum-containing conditions, rapamycin inhibited incorporation of BrdUrd significantly more in wild-type murine embryo fibroblasts (MEFs) than in those lacking p53 or p21(CIP1). When BrdUrd was added 24 h after rapamycin, almost 90% and 70% of cells lacking p53 or p21(CIP1), respectively, incorporated nucleoside. In contrast, only 19% of wild-type cells incorporated BrdUrd in the presence of rapamycin. Western blot analysis of cyclin levels showed that rapamycin had little effect on levels of cyclins D1 or E in any MEF strain. However, cyclin A was reduced to very low levels by rapamycin in wild-type cells, but remained high in cells lacking p53 or p21(CIP1). Taken together, the data suggest that p53 cooperates in enforcing G(1) cell cycle arrest, leading to a cytostatic response to rapamycin. In contrast, in tumor cells, or MEFs, having deficient p53 function the response to this agent may be cell cycle progression and apoptosis.

Bioactive chemical constituents from Alchornea laxiflora (benth) pax and hoffman

Quercetin-7,4'-disulphate (1) quercetin (2) quercetin-3',4'-disulphate (3) quercetin-3,4'-diacetate (4) rutin (5) and quercetrin (6) were isolated from the ethyl acetate soluble fraction (ESM) of the crude methanolic leaf extract of Alchornea laxiflora. Purification of these compounds was carried out by column chromatography utilising sephadex LH 20 and various mixtures of water, methanol, ethanol and toluene as eluents. Structural elucidation was by UV, IR, (1)HNMR and (13)CNMR spectroscopy as well as by FAB-MS. Antimicrobial activity of isolated compounds was detected in Gram-positive, Gram-negative and fungal organisms.

Development, characterization and therapy of a disseminated model of childhood neuroblastoma in SCID mice

PURPOSE

To develop a highly reproducible model of disseminated childhood neuroblastoma in mice to allow secondary evaluation of therapeutics against microscopic disseminated disease.

METHODS

CB17/Icr SCID were injected i.v. with 10(3) to 5 x 10(6) human NB-1691 neuroblastoma cells. NB-1691 cells were detected by PCR for synaptophysin and tyrosine hydroxylase in peripheral blood, and bone marrow. Therapeutic studies evaluated topotecan and vincristine as single agents or in combination. Topotecan was administered i.v. daily for 5 days on two consecutive weeks. Courses were repeated every 21 days for three cycles. Vincristine (1 mg/kg) was administered i.v. every 7 days for nine consecutive weeks. Treatment started 11-21 days after tumor cell inoculation.

RESULTS

Following injection of > or = 1 x 10(5) cells 100% of mice developed disease. Mice inoculated with 10(7) cells survived a median of 42 days. Survival time was a linear function of the cell inoculum. At autopsy, gross tumor was routinely detected in many organs in particular liver, ovaries, kidneys and adrenals. NB-1691 cells were detected by PCR in peripheral blood, and bone marrow. Immunohistochemical staining showed that lesions were strongly positive for synaptophysin, chromogranin A and negative for leukocyte common antigen. Topotecan (0.6 mg/kg) alone extended median survival from 44 days (controls) to 95 days. When treatment was started 21 days after inoculation of NB-1691 cells, topotecan extended median survival from 39 days (controls) to 91 and 99 days at dose levels of 0.3 and 0.6 mg/kg, respectively. Vincristine (1 mg/kg) extended survival by a median of 9.5 days. In combination with vincristine (1 mg/kg), median survival was increased to 141 days (topotecan 0.6 mg/kg) and 159 days (topotecan 1.0 mg/kg).

CONCLUSION

This model of disseminated neuroblastoma is highly reproducible. As this model may more closely simulate childhood disease it may be a valuable adjunct in developing new approaches to advanced stage, poor prognosis neuroblastoma.

Schedule-dependent activity of irinotecan plus BCNU against malignant glioma xenografts

PURPOSE

To further evaluate the activity of irinotecan (CPT-11) plus 1,3-bis-(chloroethyl)-1-nitrosourea (BCNU) in the treatment of central nervous system tumor-derived xenografts in athymic nude mice.

METHODS

We report studies evaluating the schedule-dependence of this regimen in the treatment of the malignant glioma xenograft D-54 MG.

RESULTS

The combination of BCNU and CPT-11 showed the highest enhancement index (2.0-3.3) when BCNU was given on day 1 and CPT-11 was given on days 1-5 and 8-12. Delay of CPT-11 administration to day 3 or day 5 substantially decreased activity with enhancement indices of 1.6-1.8 and 0.6-1.0, respectively. Delay of BCNU administration to day 8 also reduced the CPT-11 activity with enhancement indices of 1.2-1.4.

CONCLUSIONS

These results suggest that the presence of a BCNU-induced adduct or possibly crosslink prior to administration of CPT-11 is critical for enhanced activity. Although the mechanism of this enhancement is not currently known, a phase I trial of CPT-11 plus BCNU for adults with recurrent malignant glioma based on these results is in progress.

Downregulation of Bim, a proapoptotic relative of Bcl-2, is a pivotal step in cytokine-initiated survival signaling in murine hematopoietic progenitors

Two distinct signaling pathways regulate the survival of interleukin-3 (IL-3)-dependent hematopoietic progenitors. One originates from the membrane-proximal portion of the cytoplasmic domain of the IL-3 receptor (betac chain), which is shared by IL-3 and granulocyte-macrophage colony-stimulating factor and is involved in the regulation of Bcl-x(L) through activation of STAT5. The other pathway emanates from the distal region of the betac chain and overlaps with downstream signals from constitutively active Ras proteins. Although the latter pathway is indispensable for cell survival, its downstream targets remain largely undefined. Here we show that the expression of Bim, a member of the BH3-only subfamily of cell death activators, is downregulated by IL-3 signaling through either of two major Ras pathways: Raf/mitogen-activated protein kinase and the phosphatidylinositol 3-kinase/mammalian target of rapamycin. Akt/phosphokinase B does not appear to play a significant role in this regulatory cascade. Bim downregulation has important implications for cell survival, since enforced expression of this death activator at levels equivalent to those induced by cytokine withdrawal led to apoptosis even in the presence of IL-3. We conclude that Bim is a pivotal molecule in cytokine regulation of hematopoietic cell survival.

Relation between 9-aminocamptothecin systemic exposure and tumor response in human solid tumor xenografts

9-Aminocamptothecin (9-AC) is a topoisomerase I inhibitor with activity against xenografts from childhood solid tumors; however, clinical trials with this compound have been disappointing, resulting in discontinuation of further development. The objectives of this study were to evaluate the antitumor activity of 9-AC in a panel of pediatric solid tumor xenografts and to relate the 9-AC lactone systemic exposure, defined as area under the concentration time curve (AUC), to the antitumor dose associated with tumor regression in the xenograft model. We evaluated protracted administration of i.v. and oral therapies (daily times 5) for 1, 2, or 3 weeks and for 1 or 3 cycles. The minimum effective dose of 9-AC causing objective regression of advanced tumors was determined for each schedule. 9-AC lactone plasma concentration-time profiles associated with the lowest dose achieving complete and partial responses for each xenograft were then determined for each regimen. Tumors were highly sensitive to 9-AC therapy, but the systemic exposure required for antitumor effect is in excess of that achievable in patients.

In vitro cytotoxicity of norviburtinal and isopinnatal from Kigelia pinnata against cancer cell lines

Crude dichloromethane extracts of Kigelia pinnata stem bark and fruit showed cytotoxic activity in vitro against cultured melanoma and other cancer cell lines using the Sulphorhodamine B assay, which was used for bioassay-guided fractionation. Thin layer chromatography (TLC) examination of the most active fractions of both stem bark and fruits showed the presence of the same major components which were found to be norviburtinal and beta-sitosterol. Norviburtinal was found to be the most active compound but had little selectivity for melanoma cell lines whilst isopinnatal also showed some cytotoxic activity. beta-Sitosterol was found to be comparatively inactive. HPLC analysis of the crude extract showed that the amount of norviburtinal present in the plant material did not account for all of the activity of the total extracts.

Schedule-dependent activity of temozolomide plus CPT-11 against a human central nervous system tumor-derived xenograft

Temozolomide, an imidazole tetrazinone, and CPT-11, a camptothecin derivative, have previously been shown to have anti-central nervous system tumor activity in laboratory and clinical studies. The current experiments were designed to evaluate the activity of temozolomide plus CPT-11 against a malignant glioma-derived xenograft, D-54 MG, growing s.c. in athymic nude mice. The initial schedule of i.p. drug administration was temozolomide at 0.1 LD10 on day 1 and CPT-11 at 0.1 LD10 on days 1-5 and 8-14. The combination of these two agents produced greater than additive activity against D-54 MG. This enhanced activity was maintained when the initial administration of CPT-11 was delayed to day 3 or day 5. However, when CPT-11 was administered first on day 1 using 0.5 LD10 (for the single dose schedule) followed by temozolomide (0.1 LD10) 5 h, 3 days, or 5 days later, the enhancement of activity was substantially reduced. These results demonstrate that the combination of temozolomide plus CPT-11 displays a schedule-dependent enhancement of antitumor activity, suggest a mechanistic explanation for the enhanced activity, and provide the rationale for a Phase I trial of this regimen.

Antitumor activity of temozolomide combined with irinotecan is partly independent of O6-methylguanine-DNA methyltransferase and mismatch repair phenotypes in xenograft models

The activity of temozolomide combined with irinotecan (CPT-11) was evaluated against eight independent xenografts (four neuroblastomas, three rhabdomyosarcomas, and one glioblastoma). In all studies, temozolomide was administered p.o. daily for 5 consecutive days/cycle, found in preliminary studies to be the optimal schedule for administration. Irinotecan was administered i.v. for 5 days for 2 consecutive weeks/cycle. Treatment cycles were repeated every 21 days for a total of three cycles over 8 weeks. In combination, temozolomide and CPT-11 induced complete responses in four neuroblastomas, two rhabdomyosarcomas, and the glioblastoma line. The activity of the combination was significantly greater than the activity of either agent administered alone in four tumor lines. Of interest, the interaction appeared independent of tumor MGMT or mismatch repair phenotype, suggesting that the mechanism of synergy may be independent of O6-methylation by temozolomide. Pharmacokinetic studies indicated no detectable interaction between these two agents. Further, coadministration of CPT-11 appeared to reduce the toxicity of temozolomide in tumor-bearing mice.

Clinical use of topoisomerase I inhibitors in anticancer treatment

The camptothecin analogs topotecan and irinotecan have shown to be among the most effective anticancer agents and, as S-phase specific agents, their antitumor effect is maximized when they are administered in protracted schedules. The documented activity as single agents in many adult and pediatric malignancies has been followed by their use in combination with other anticancer agents. These studies have shown promising results, and have placed topotecan and irinotecan in the first line treatment for some malignancies. However, studies to better determine the optimal schedules and sequence of combinations are needed.

Activity of extracts and isolated naphthoquinones from Kigelia pinnata against Plasmodium falciparum

Four naphthoquinoids from Kigelia pinnata rootbark were assessed in vitro against chloroquine-sensitive (T9-96) and -resistant (K1) Plasmodium falciparum strains and for cytotoxicity using KB cells. 2-(1-Hydroxyethyl)naphtho[2,3-b]furan-4,9-dione possessed good activity against both strains [IC(50) values 627 nM (K1), 718 nM (T9-96)]. Isopinnatal, kigelinol, and isokigelinol exhibited lower activity against both strains.