Chemoprevention: an essential approach to controlling cancer.

Mortality that results from the common forms of cancer is still unacceptably high. Despite immense advances in the understanding of the mechanisms of carcinogenesis, in bringing potent new drugs to the clinic and in treating several relatively rare forms of cancer, overall mortality statistics are unlikely to change in a fundamental way until there has been a re-orientation of emphasis in cancer research that will direct greater resources towards prevention of new disease, rather than treatment of end-stage disease.

An inducible pathway for degradation of FLIP protein sensitizes tumor cells to TRAIL-induced apoptosis.

TRAIL (Apo2 ligand) is a member of the tumor necrosis factor (TNF) family of cytokines that induces apoptosis. Because TRAIL preferentially kills tumor cells, sparing normal tissues, interest has emerged in applying this biological factor for cancer therapy in humans. However, not all tumors respond to TRAIL, raising questions about resistance mechanisms.

A novel dicyanotriterpenoid, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-onitrile, active at picomolar concentrations for inhibition of nitric oxide production.

New oleanane triterpenoids with various substituents at the C-17 position of 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) and methyl 2-carboxy-3,12-dioxooleana-1,9(11)-dien-28-oate were synthesized. Among them, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-onitrile shows extremely high inhibitory activity (IC(50)=1 pM level) against production of nitric oxide induced by interferon-gamma in mouse macrophages. This potency is about 100 times and 30 times more potent than CDDO and dexamethasone, respectively.

The novel triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) potently enhances apoptosis induced by tumor necrosis factor in human leukemia cells.

Tumor necrosis factor (TNF) is a potent activator of the nuclear factor-kappaB (NF-kappaB) pathway that leads to up-regulation of anti-apoptotic proteins. Hence, TNF induces apoptosis in the presence of inhibitors of protein or RNA synthesis. We report that a novel triterpenoid, 2-cyano-3,12-dioxooleana-1,9,-dien-28-oic acid (CDDO) inhibits NF-kappaB-mediated gene expression at a step after translocation of activated NF-kappaB to the nucleus.

Novel triterpenoid CDDO-Me is a potent inducer of apoptosis and differentiation in acute myelogenous leukemia.

It has been shown that the novel synthetic triterpenoid CDDO inhibits proliferation and induces differentiation and apoptosis in myeloid leukemia cells. In the current study the effects of the C-28 methyl ester of CDDO, CDDO-Me, were analyzed on cell growth and apoptosis of leukemic cell lines and primary acute myelogenous leukemia (AML). CDDO-Me decreased the viability of leukemic cell lines, including multidrug resistant (MDR)-1-overexpressing, p53(null) HL-60-Dox and of primary AML cells, and it was 3- to 5-fold more active than CDDO.

Arzoxifene, a new selective estrogen receptor modulator for chemoprevention of experimental breast cancer.

Arzoxifene ([6-hydroxy-3-[4-[2-(1-piperidinyl)-ethoxy]phenoxy]-2-(4-methoxyphenyl)]benzo[b]thiophene) is a selective estrogen receptor modulator (SERM) that is a potent estrogen antagonist in mammary and uterine tissue while acting as an estrogen agonist to maintain bone density and lower serum cholesterol. Arzoxifene is a highly effective agent for prevention of mammary cancer induced in the rat by the carcinogen nitrosomethylurea and is significantly more potent than raloxifene in this regard. Arzoxifene is devoid of the uterotrophic effects of tamoxifen, suggesting that, in contrast to tamoxifen, it is unlikely that the clinical use of arzoxifene will increase the risk of developing endometrial carcinoma.

Prospects for prevention and treatment of cancer with selective PPARgamma modulators (SPARMs).

Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor and transcription factor that regulates the expression of many genes relevant to carcinogenesis, is now an important target for development of new drugs for the prevention and treatment of cancer. Deficient expression of PPARgamma can be a significant risk factor for carcinogenesis, although in some cases overexpression enhances carcinogenesis. Ligands for PPARgamma suppress breast carcinogenesis in experimental models and induce differentiation of human liposarcoma cells.

Synthetic oleanane and ursane triterpenoids with modified rings A and C: a series of highly active inhibitors of nitric oxide production in mouse macrophages.

We have designed and synthesized 16 new olean- and urs-1-en-3-one triterpenoids with various modified rings C as potential antiinflammatory and cancer chemopreventive agents and evaluated their inhibitory activities against production of nitric oxide induced by interferon-gamma in mouse macrophages. This investigation revealed that 9(11)-en-12-one and 12-en-11-one functionalities in ring C increase the potency by about 2-10 times compared with the original 12-ene. Subsequently, we have designed and synthesized novel olean- and urs-1-en-3-one derivatives with nitrile and carboxyl groups at C-2 in ring A and with 9(11)-en-12-one and 12-en-11-one functionalities in ring C.

A synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), is a ligand for the peroxisome proliferator-activated receptor gamma.

A novel synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), previously reported to have potent differentiating, antiproliferative, and antiinflammatory activities, has been identified as a ligand for the peroxisome proliferator-activated receptor gamma (PPARgamma). CDDO induces adipocytic differentiation in 3T3-L1 cells, although it is not as potent as the full agonist of PPARgamma, rosiglitazone. Binding studies of CDDO to PPARgamma using a scintillation proximity assay give a Ki between 10(-8) to 10(-7) M.

Novel synthetic oleanane and ursane triterpenoids with various enone functionalities in ring A as inhibitors of nitric oxide production in mouse macrophages.

We initially randomly synthesized about 60 oleanane and ursane triterpenoids as potential anti-inflammatory and cancer chemopreventive agents. Preliminary screening of these derivatives for inhibition of production of nitric oxide induced by interferon-gamma in mouse macrophages revealed that 3-oxooleana-1, 12-dien-28-oic acid (B-15) showed significant activity (IC(50) = 5.6 microM).

Chemoprevention of cancer.

In this short article, we review the conceptual basis for chemoprevention of cancer, the proven clinical efficacy of this concept, and current trends to develop new chemopreventive agents based on understanding of their mechanisms of action. Four classes of new agents, namely selective inhibitors of cyclooxygenase-2, selective estrogen receptor modulators, rexinoids (retinoids that bind selectively to the receptors known as RXRs) and ligands for the peroxisome proliferator-activated receptor-gamma are discussed in detail. The importance of developing totally new classes of chemopreventive agents is stressed, with particular emphasis on the potential usefulness of new synthetic triterpenoids derived from naturally occurring molecules.

Novel synthetic oleanane triterpenoids: a series of highly active inhibitors of nitric oxide production in mouse macrophages.

Novel oleanane triterpenoids with modified rings A and C were designed and synthesized. Among them, methyl 2-carboxy-3,12-dioxooleana-1,9-dien-28-oate showed similar high inhibitory activity (IC50 = 0.8 nM) to 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), which we have synthesized previously, against production of nitric oxide induced by interferon-gamma in mouse macrophages.

A new ligand for the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), GW7845, inhibits rat mammary carcinogenesis.

We have tested a new ligand for peroxisome proliferator-activated receptor-gamma, GW7845, as an inhibitor of experimental mammary carcinogenesis, using the classic rat model with nitrosomethylurea as carcinogen. Rats were first treated with a single dose of nitrosomethylurea (50 mg/kg body weight, i.p.

A novel synthetic oleanane triterpenoid, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid, with potent differentiating, antiproliferative, and anti-inflammatory activity.

The new synthetic oleanane triterpenoid 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) is a potent, multifunctional molecule. It induces monocytic differentiation of human myeloid leukemia cells and adipogenic differentiation of mouse 3T3-L1 fibroblasts and enhances the neuronal differentiation of rat PC12 pheochromocytoma cells caused by nerve growth factor. CDDO inhibits proliferation of many human tumor cell lines, including those derived from estrogen receptor-positive and -negative breast carcinomas, myeloid leukemias, and several carcinomas bearing a Smad4 mutation.

Design and synthesis of 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid, a novel and highly active inhibitor of nitric oxide production in mouse macrophages.

New derivatives with electron-withdrawing substituents at the C-2 position of 3-oxoolean-1-en-28-oic acid were synthesized. Among them, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) was 400 times more potent than previous compounds we have made as an inhibitor of production of nitric oxide induced by interferon-gamma in mouse macrophages (IC50, 0.4 nM).

Novel triterpenoids suppress inducible nitric oxide synthase (iNOS) and inducible cyclooxygenase (COX-2) in mouse macrophages.

We have synthesized more than 80 novel triterpenoids, all derivatives of oleanolic and ursolic acid, as potential anti-inflammatory and chemopreventive agents. These triterpenoids have been tested for their ability to suppress the de novo formation of two enzymes, inducible nitric oxide synthase (iNOS) and inducible cyclooxygenase (COX-2), using IFN-gamma-stimulated primary mouse macrophages or lipopolysaccharide (LPS)-activated RAW 264.7 macrophages as assay systems.

A lignan and four terpenoids from Brucea javanica that induce differentiation with cultured HL-60 promyelocytic leukemia cells.

A novel lignan, guaiacylglycerol-beta-O-6'-(2-methoxy)cinnamyl alcohol either, three known simaroubolides, brusatol, dehydrobrusatol, yadanziolide C, and the known terpenoid, blumenol A, were obtained as active compounds from an ethyl acetate-soluble extract of Brucea javanica, using a bioassay based on the induction of cell differentiation with human promyelocytic leukemia (HL-60) cells. Also obtained were the known coumarinolignan, cleomiscosin A, and the known quassinoid glycoside, bruceoside B, which were inactive in the HL-60 cell test system. The structure of the new lignan was determined by a combination of 1D and 2D NMR techniques.

Novel approach to fabricate porous sponges of poly(D,L-lactic-co-glycolic acid) without the use of organic solvents.

A novel method was developed to produce highly porous sponges for potential use in tissue engineering, without the use of organic solvents. Highly porous sponges of biodegradable polymers are frequently utilized in tissue engineering both to transplant cells or growth factors, and to serve as a template for tissue regeneration. The processes utilized to fabricate sponges typically use organic solvents, but organic residues remaining in the sponges may be harmful to adherent cells, protein growth factors or nearby tissues.

Discovery of natural product chemopreventive agents utilizing HL-60 cell differentiation as a model.

Terminal differentiation of human promyelocytic leukemia (HL-60) cells can be induced by a variety of chemical agents and this process can be monitored readily by the generation of morphologically, histochemically, and functionally mature granulocytes and monocytes/macrophages. The availability of this model has heightened interest in the possible therapeutic role of inducers of myeloid differentiation for the treatment of leukemia and other neoplasms. In addition, however, potent cancer chemopreventive agents induce HL-60 cell differentiation at very low dose levels.

Rotenoids mediate potent cancer chemopreventive activity through transcriptional regulation of ornithine decarboxylase.

For the discovery of new cancer chemopreventive agents, we have studied the potential of plant extracts to inhibit phorbol ester-induced ornithine decarboxylase (ODC) activity in cell culture. Four active rotenoids were obtained from the African plant Mundulea sericea (Leguminosae). These isolates were highly potent when evaluated for inhibition of chemically induced preneoplastic lesions in mammary organ culture and inhibition of papillomas in the two-stage mouse skin model, and they appear to function by a unique mechanism at the level of ODC messenger RNA expression.

Pharmacokinetic study of an iridoid glucoside: aucubin.

Aucubin, a promising hepatoprotecting iridoid glucoside, was given intravenously (iv), orally (po), intraperitoneally (ip), and hepatoportally (pv) to rats. A linear pharmacokinetic behavior was obtained after iv administation of 400-400 mg/kg of aucubin. The half-life of aucubin in the postdistributive phase (t1/2, beta), total-body plasma clearance (CLt), and volume of distribution (Vdss) were 42.

Cross-reactivity with mouse antigens in the ferritin immunogenetic (IR-gene) system.

Structural similarity between antigens and self molecules could be responsible for low antibody responses in different immunogenetic (IR-gene) systems. B10.M and B10.