Multiple myeloma regression mediated by bruceantin.

PURPOSE: Bruceantin has been shown to induce cell differentiation in a number of leukemia and lymphoma cell lines. It also down-regulated c-MYC, suggesting a correlation of down-regulation with induction of cell differentiation or cell death. In the present study, we focused on multiple myeloma, using the RPMI 8226 cell line as a model. EXPERIMENTAL DESIGN: The effects of bruceantin on c-MYC levels and apoptosis were examined by immunoblotting, 4',6-diamidino-2-phenylindole staining, evaluation of caspase-like activity, and 3,3'-dihexyloxacarbocyanine iodide staining. The potential of bruceantin to inhibit primary tumor growth was assessed with RPMI 8226 xenografts in SCID mice, and apoptosis in the tumors was evaluated by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay. RESULTS: c-MYC was strongly down-regulated in cultured RPMI 8226 cells by treatment with bruceantin for 24 h. With U266 and H929 cells, bruceantin did not regulate c-MYC in this manner. Apoptosis was induced in the three cell lines. In RPMI 8226 cells, apoptosis occurred through proteolytic processing of procaspases and degradation of poly(ADP-ribose) polymerase. The mitochondrial pathway was also involved. Because RPMI 8226 cells were the most sensitive, they were used in a xenograft model. Bruceantin treatment (2.5-5 mg/kg) resulted in a significant regression of tumors without overt toxicity. Apoptosis was significantly elevated in tumors derived from animals treated with bruceantin (37%) as compared with the control tumors (14%). CONCLUSIONS: Bruceantin interferes with the growth of RPMI 8226 cells in cell culture and xenograft models. These results suggest that bruceantin should be reinvestigated for clinical efficacy against multiple myeloma and other hematological malignancies.     

Dietary Administration of Asimina triloba. (Paw Paw) Extract Increases Tumor Latency in N.-Methyl-N.-nitrosourea–Treated Rats

Abstract

The paw paw tree, Asimina triloba. (L.) Dunal (Annonaceae), contains more than 50 bioactive components, primarily annonaceous acetogenins. Some therapeutic activities have been associated with this material, but the potential to mediate a cancer chemopreventive effect has not been reported. In this study, a standardized extract from the twigs, in which bullatacin, asimicin, and trilobacin represent the most potent and major bioactive acetogenins, was tested in the N.-methyl-N.-nitrosourea–induced mammary carcinogenesis model. With Sprague-Dawley rats given a diet containing paw paw extract (1250 and 2500 mg/kg diet; based on maximum tolerated dose studies), mammary tumor latency was increased from 55 to 66 days. However, mammary tumor incidence and multiplicity were not affected by extract consumption.     

Brusatol-induced HL-60 cell differentiation involves NF-kappaB activation

Brusatol, a quassinoid isolated from the fruit of Brucea javanica, induces cell differentiation with various leukemic cell lines in the concentration range of 5-25 ng/ml. To investigate its mechanism of action, cultured HL-60 cells were treated with brusatol (25 ng/ml) for various periods of time and qualitatively analyzed for differential gene expression using a cDNA macroarray. As suggested by these preliminary data, we investigated the effect of brusatol on the Rel/nuclear factor-kappa B (NF-kappaB) family members and their role in HL-60 cell differentiation. When cells were treated with brusatol (25 ng/ml), p100/p52, p105/p50 and p65 mRNA were found to be up-regulated with a maximum after 8 h. As determined by electrophoretic mobility shift assays (EMSA), NF-kappaB was activated, involving p50 and p65. Moreover, immunoblots showed a decrease of IkappaBalpha and generation of the phosphorylated form of IkappaBalpha in whole cell lysates. Cell differentiation induced by brusatol was inhibited by SN50, a NF-kappaB translocation inhibitor. These results strongly suggest that brusatol induces activation of NF-kappaB and the activation and translocation of NF-kappaB into the nucleus is responsible for promoting HL-60 cell differentiation.     

Natural inhibitors of carcinogenesis

Previous collaborative work by our group has led to the discovery of several plant isolates and derivatives with activities in in vivo models of cancer chemoprevention, including deguelin, resveratrol, bruceantin, brassinin, 4'-bromoflavone, and oxomate. Using a panel of in vitro bioassays to monitor chromatographic fractionation, a diverse group of plant secondary metabolites has been identified as potential cancer chemopreventive agents from mainly edible plants. Nearly 50 new compounds have been isolated as bioactive principles in one or more in vitro bioassays in work performed over the last five years. Included among these new active compounds are alkaloids, flavonoids, stilbenoids, and withanolides, as well as a novel stilbenolignan and the first representatives of the norwithanolides, which have a 27-carbon atom skeleton. In addition, over 100 active compounds of previously known structure have been obtained. Based on this large pool of potential cancer chemopreventive compounds, structure-activity relationships are discussed in terms of the quinone reductase induction ability of flavonoids and withanolides and the cyclooxygenase-1 and -2 inhibitory activities of flavanones, flavones and stilbenoids. Several of the bioactive compounds were found to be active when evaluated in a mouse mammary organ culture assay, when used as a secondary discriminator in our work. The compounds (2 S)-abyssinone II, (2 S)-2',4'-dihydroxy-2"-(1-hydroxy-1-methylethyl)dihydrofuro[2,3- h]-flavanone, 3'-[gamma-hydroxymethyl-( E)-gamma-methylallyl]-2,4,2',4'-tetrahydroxychalcone 11'- O-coumarate, isolicoflavonol, isoliquiritigenin, and ixocarpalactone A are regarded as promising leads as potential cancer chemopreventive agents.     

Two new stilbene dimer glucosides from grape (Vitis vinifera) cell cultures

Two new stilbene dimer glucosides, resveratrol (E)-dehydrodimer 11-O-beta-D-glucopyranoside (1) and resveratrol (E)-dehydrodimer 11'-O-beta-D-glucopyranoside (2), were isolated together with the known resveratrol (E)-dehydrodimer (3) and pallidol (4) from Vitis vinifera cell cultures. The structures and stereochemistry of the new compounds were determined on the basis of spectroscopic data analysis. Compounds 1 and 2 are dimers that belong to a new type of oligostilbene formed from a resveratrol unit and a resveratrol glucoside unit. Compounds 1 and 3 exhibited nonspecific inhibitory activity against cyclooxygenase-1 and -2, with IC(50) values in the range of 5 microM, whereas compound 4 was approximately 10-fold less active.     

Synthesis and cancer chemopreventive activity of zapotin, a natural product from Casimiroa edulis

An efficient method has been developed to synthesize zapotin (5,6,2',6'-tetramethoxyflavone), a component of the edible fruit Casimiroa edulis, on a multigram scale. The synthesis utilizes a regioselective C-acylation of a dilithium dianion derived from a substituted o-hydroxyactophenone to afford a beta-diketone intermediate that can be cyclized to zapotin in good overall yield, thus avoiding the inefficient Baker-Venkataraman rearrangement pathway. Zapotin was found to induce both cell differentiation and apoptosis with cultured human promyelocytic leukemia cells (HL-60 cells). In addition, the compound inhibits 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity with human bladder carcinoma cells (T24 cells), and TPA-induced nuclear factor-kappa B (NF-kappaB) activity with human hepatocellular liver carcinoma cells (HepG2 cells). These data suggest that zapotin merits further investigation as a potential cancer chemopreventive agent.     

Multiple intestinal atresias and encephalomalacia in the survivor after in-utero death of a monozygous co-twin

A twin infant who survived the death of his monochorionic co-twin in utero and was born with multiple jejunoileal atresias and severe cerebral damage is reported. The pathogenesis of these defects is discussed in the light of previously reported similar cases. The incidence of severe brain damage in twins born alive after the intrauterine death of a monochorionic co-twin is high, suggesting brain destruction by embolization of thromboplastin-rich material from the dead fetus via placental vascular anastomoses. A similar mechanism could be evoked in the present case to account for the intestinal atresias, which likely occurred after the 22nd gestational week, i.e. after the normal permeabilization of the embryonic gut. In the light of this observation and similar ones made by others, it is clear that surgical management of congenital defects during the neonatal period should be influenced by the knowledge of in-utero death of a monochorionic co-twin during the second half of gestation.     

Binding of amitriptyline to alpha 1-acid glycoprotein and its variants

Binding studies have been performed between amitriptyline and i) native alpha 1-acid glycoprotein (AAG); ii) its desialylated form; iii) its two variants, S-AAG and F-AAG; and iv) a mixture of S-AAG and F-AAG. Scatchard analysis revealed the presence of two classes of binding sites on AAG. For native AAG, the first class (of high affinity) has an association constant (Ka1) of 1.5 x 10(6) L mol-1 and a number of binding sites per mole of protein (n1) of 0.25, while the second class (of low affinity) has a Ka2 of 3.2 x 10(4) L mol-1 and a n2 of 0.94. Similar data were found for desialylated AAG. S-AAG and F-AAG do not differ in their association constants measured with amitriptyline, but in their number of binding sites per mole of protein (n): S-AAG: n1 = 0.56, n2 = 0.52; F-AAG: n1 = 0.17, n2 = 0.71. These results confirm those of a previous study, in which a higher affinity of S-AAG towards various basic drugs in comparison with F-AAG has been found.