Showing papers by "Michael B. Sporn published in 2000"

Chemoprevention of Cancer

Abstract: 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.

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

Abstract: 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-γ 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. Among them, we have found that methyl 2-cyano-3, 12-dioxooleana-1,9(11)-dien-28-oate (25), 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) (26), and methyl 2-carboxy-3,12-dioxooleana-1,9(11)-dien-28-oate (29) have extremely high potency (IC50 = 0.1 nM level). Their potency is similar to that of dexamethasone although they do not act t...

A Synthetic Triterpenoid, 2-Cyano-3,12-dioxooleana-1,9-dien-28-oic Acid (CDDO), Is a Ligand for the Peroxisome Proliferator-Activated Receptor γ

Abstract: 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. In transactivation assays, CDDO is a partial agonist for PPARgamma. The methyl ester of CDDO, CDDO-Me, binds to PPARgamma with similar affinity, but is an antagonist. Like other PPARgamma ligands, CDDO synergizes with a retinoid X receptor (RXR)-specific ligand to induce 3T3-L1 differentiation, while CDDO-Me is an antagonist in this assay. The partial agonism of CDDO and the antagonism of CDDO-Me reflect the differences in their capacity to recruit or displace cofactors of transcriptional regulation; CDDO and rosiglitazone both release the nuclear receptor corepressor, NCoR, from PPARgamma, while CDDO-Me does not. The differences between CDDO and rosiglitazone as either partial or full agonists, respectively, are seen in the weaker ability of CDDO to recruit the coactivator CREB-binding protein, CBP, to PPARgamma. Our results establish the triterpenoid CDDO as a member of a new class of PPARgamma ligands.

The novel triterpenoid 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid induces apoptosis of human myeloid leukemia cells by a caspase-8-dependent mechanism.

Abstract: The oleanane triterpenoid 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) is a multifunctional molecule that induces growth inhibition and differentiation of human myeloid leukemia cells. The present studies demonstrate that CDDO treatment results in apoptosis of U-937 and HL-60 myeloid leukemia cells. Similar to 1-beta-D-arabinofuranosylcytosine (ara-C), another agent that inhibits growth and induces apoptosis of these cells, CDDO induced the release of mitochondrial cytochrome c and activation of caspase-3. Overexpression of Bcl-X(L) blocked cytochrome c release, caspase-3 activation, and apoptosis in ara-C-treated cells. By contrast, CDDO-induced release of cytochrome c, and activation of caspase-3 were diminished only in part by Bcl-X(L). In concert with these findings, we demonstrate that CDDO, but not ara-C, activates caspase-8 and thereby caspase-3 by a cytochrome c-independent mechanism. The results also show that CDDO-induced cytochrome c release is mediated by caspase-8-dependent cleavage of Bid. These findings demonstrate that CDDO induces apoptosis of myeloid leukemia cells and that this novel agent activates an apoptotic signaling cascade distinct from that induced by the cytotoxic agent ara-C.

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

Abstract: 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-γ in mouse macrophages revealed that 3-oxooleana-1,12-dien-28-oic acid (B-15) showed significant activity (IC50 = 5.6 μM). On the basis of the structure of B-15, 19 novel olean- and urs-12-ene triterpenoids with a 1-en-3-one functionality having a substituent at C-2 in ring A have been designed and synthesized. Among them, 3-oxooleana-1,12-diene derivatives with carboxyl, methoxycarbonyl, and nitrile groups at C-2 showed higher activity than the lead compound B-15. In particular, 2-carboxy-3-oxooleana-1,12-dien-28-oic acid (3) had the highest activity (IC50 = 0.07 μM) in this group of triterpenoids. The potency of 3 was similar to that of hydrocortisone (IC50 = 0.01 μM), although 3 does not act through the glucocorticoid receptor. Interesting structure−acti...

Novel Synthetic Oleanane and Ursane Triterpenoids with Various Enone Functionalities in Ring A as Inhibitors of Nitric Oxide Production in Mouse Macrophages.

Abstract: 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-γ in mouse macrophages revealed that 3-oxooleana-1,12-dien-28-oic acid (B-15) showed significant activity (IC50 = 5.6 μM). On the basis of the structure of B-15, 19 novel olean- and urs-12-ene triterpenoids with a 1-en-3-one functionality having a substituent at C-2 in ring A have been designed and synthesized. Among them, 3-oxooleana-1,12-diene derivatives with carboxyl, methoxycarbonyl, and nitrile groups at C-2 showed higher activity than the lead compound B-15. In particular, 2-carboxy-3-oxooleana-1,12-dien-28-oic acid (3) had the highest activity (IC50 = 0.07 μM) in this group of triterpenoids. The potency of 3 was similar to that of hydrocortisone (IC50 = 0.01 μM), although 3 does not act through the glucocorticoid receptor. Interesting structure−acti...

Dietary 4-HPR suppresses the development of bone metastasis in vivo in a mouse model of prostate cancer progression.

Abstract: The effects of the synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR) on prostate cancer metastasis in vivo were evaluated in the mouse prostate reconstitution (MPR) model. MPRs were produced by infection of either heterozygous (+/−) or nullizygous (−/−) p53-mutant fetal prostatic epithelial cells with the recombinant retrovirus Zipras/myc 9. Previous studies have documented that loss of p53 function potentiates metastasis in this model system. MPRs were grafted into homozygous (+/+) p53 male mice, fed a 4-HPR containing diet or a control diet and maintained until the status of tumor progression dictated sacrifice. Under these experimental conditions, treatment with 4-HPR did not have a significant effect on primary tumor wet weight for either p53 +/− or p53 −/− MPRs. For, p53 +/− MPRs the animals fed the 4-HPR diet had a slight improvement in survival and a significant reduction in the number of mesenteric metastases (P=0.0477, t-test). Notably, in p53 +/− MPRs the incidence of metastasis to lumbar spine and sternum was 92% in the control animals compared to 54% in the 4-HPR treated animals (P=0.035, χ2-test). In p53 −/− MPRs there was a trend toward a reduction in the number of soft tissue metastases to lung and liver in the 4-HPR group relative to the control diet group and a statistically significant reduction in the incidence of metastasis to bone was demonstrated in that 50% of control animals versus 30% of 4-HPR treated p53 −/− animals harbored bone metastases (P=0<0.05, χ2-test). Cell lines were established from portions of the primary tumor and from selected metastatic deposits in each experimental group. Clonal analysis, by retroviral integration pattern, indicated increased clonal diversity in both the primary tumors and metastasis-derived cell lines from 4-HPR treated animals relative to the control animals. In vitro treatment with 4-HPR did not reveal discriminating differences between cell lines derived from primary tumors and bone metastases or control and treatment groups in regard to growth arrest or apoptotic responses. Overall these studies indicate limited anti-tumor and anti-metastatic activity in this highly aggressive in vivo mouse model of prostate cancer, yet 4-HPR treatment significantly suppressed the development of bone metastases in p53 +/− and p53 −/− MPRs revealing a novel and potentially clinically useful activity of this retinoid.

Novel Synthetic Oleanane Triterpenoids: A Series of Highly Active Inhibitors of Nitric Oxide Production in Mouse Macrophages.

Abstract: 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.