There is evidence that specificity proteins (Sp), such as Sp1, Sp3, and Sp4, are overexpressed in tumors and contribute to the proliferative and angiogenic phenotype associated with cancer cells. Sp1, Sp3, and Sp4 are expressed in a panel of estrogen receptor (ER)-positive and ER-negative breast cancer cell lines, and we hypothesized that regulation of their expression may be due to microRNA-27a (miR-27a), which is also expressed in these cell lines and has been reported to regulate the zinc finger ZBTB10 gene, a putative Sp repressor. Transfection of ER-negative MDA-MB-231 breast cancer cells with antisense miR-27a (as-miR-27a) resulted in increased expression of ZBTB10 mRNA and decreased expression of Sp1, Sp3, and Sp4 at the mRNA and protein levels and also decreased activity in cells transfected with constructs containing Sp1 and Sp3 promoter inserts. In addition, these responses were accompanied by decreased expression of Spdependent survival and angiogenic genes, including survivin, vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1). Moreover, similar results were observed in MDA-MB-231 cells transfected with ZBTB10 expression plasmid. Both as-miR-27a and ZBTB10 overexpression decreased the percentage of MDA-MB-231 cells in S phase of the cell cycle; however, ZBTB10 increased the percentage of cells in G 0 -G 1 , whereas as-miR-27a increased the percentage in G 2 -M. This latter response was associated with induction of Myt-1 (another miR-27a target gene), which inhibits G 2 -M through enhanced phosphorylation and inactivation of cdc2. Thus, the oncogenic activity of miR-27a in MDA-MB-231 cells is due, in part, to suppression of ZBTB10 and Myt-1. [Cancer Res 2007;67(22):11001-11]

Betulinic acid is a pentacyclic triterpene natural product initially identified as a melanoma-specific cytotoxic agent that exhibits low toxicity in animal models. Subsequent studies show that betulinic acid induces apoptosis and antiangiogenic responses in tumors derived from multiple tissues; however, the underlying mechanism of action is unknown. Using LNCaP prostate cancer cells as a model, we now show that betulinic acid decreases expression of vascular endothelial growth (VEGF) and the antiapoptotic protein survivin. The mechanism of these betulinic acid-induced antiangiogenic and proapoptotic responses in both LNCaP cells and in tumors is due to activation of selective proteasome-dependent degradation of the transcription factors specificity protein 1 (Sp1), Sp3, and Sp4, which regulate VEGF and survivin expression. Thus, betulinic acid acts as a novel anticancer agent through targeted degradation of Sp proteins that are highly overexpressed in tumors. [Cancer Res 2007;67(6):2816-23]

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related deaths globally due, in part, to the majority of patients being diagnosed with intermediate or advanced stage disease. Our increased understanding of the heterogeneous molecular pathogenesis of HCC has led to significant developments in novel targeted therapies. Despite these advances, there remains a high unmet need for new treatment options. HCC is a complex disease with multiple pathogenic mechanisms caused by a variety of risk factors, making it difficult to characterize with a single biomarker.In fact, numerous biomarkers have been studied in HCC, but alpha-fetoprotein (AFP) remains the most widely used and accepted serum marker since its discovery over 60 years ago. This review summarizes the most relevant studies associated with the regulation of AFP at the gene and protein levels; the pathophysiology of AFP as a pro-proliferative protein; and the correlation of AFP with molecular HCC subclasses, the vascular endothelial growth factor pathway and angiogenesis. Also described are | 2215 GALLE Et AL.

Activation of the orphan nuclear receptor TR3/Nur77 (NR4A1) promotes apoptosis and inhibits pancreatic tumor growth, but its endogenous function and the effects of its inactivation have yet to be determined. TR3 was overexpressed in human pancreatic tumors compared with nontumor tissue. Small interfering RNA-mediated knockdown of TR3 or cell treatment with the TR3 antagonist 1,1-bis(3′-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) decreased proliferation, induced apoptosis, and decreased expression of antiapoptotic genes including Bcl-2 and survivin in pancreatic cancer cells. Survivin suppression was mediated by formation of a TR3-Sp1-p300 DNA binding complex on the proximal GC-rich region of the survivin promoter. When administered in vivo, DIM-C-pPhOH induced apoptosis and inhibited tumor growth in an orthotopic model of pancreatic cancer, associated with inhibition of the same antiapoptotic markers observed in vitro. Our results offer preclinical validation of TR3 as a drug target for pancreatic cancer chemotherapy, based on the ability of TR3 inhibitors to block the growth of pancreatic tumors.

Curcumin is the active component of tumeric, and this polyphenolic compound has been extensively investigated as an anticancer drug that modulates multiple pathways and genes. In this study, 10 to 25 Mmol/L curcumin inhibited 253JB-V and KU7 bladder cancer cell growth, and this was accompanied by induction of apoptosis and decreased expression of the proapoptotic protein survivin and the angiogenic proteins vascular endothelial growth factor (VEGF) and VEGF receptor 1 (VEGFR1). Because expression of survivin, VEGF, and VEGFR1 are dependent on specificity protein (Sp) transcription factors, we also investigated the effects of curcumin on Sp protein expression as an underlying mechanism for the apoptotic and antiangiogenic activity of this compound. The results show that curcumin induced proteasome-dependent down-regulation of Sp1, Sp3, and Sp4 in 253JB-V and KU7 cells. Moreover, using RNA interference with small inhibitory RNAs for Sp1, Sp3, and Sp4, we observed that curcumin-dependent inhibition of nuclear factor KB (NF-KB)-dependent genes, such as bcl-2, survivin, and cyclin D1, was also due, in part, to loss of Sp proteins. Curcumin also decreased bladder tumor growth in athymic nude mice bearing KU7 cells as xenografts and this was accompanied by decreased Sp1, Sp3, and Sp4 protein levels in tumors. These results show for the first time that one of the underlying mechanisms of action of curcumin as a cancer chemotherapeutic agent is due, in part, to decreased expression of Sp transcription factors in bladder cancer cells. [Cancer Res 2008;68(13):5345-54]

The nuclear receptor superfamily of eukaryotic transcription factors encompasses steroid hormone and other nuclear receptors for which ligands have been identified and orphan receptors with no known ligands (1-7). Nuclear receptors share common structural features that include an N-terminal A/B domain, containing activation function-1 (AF-1),1 and a C-terminal E domain, which contains AF-2 and the ligand binding domain (LBD). Nuclear receptors also have a DNA binding domain (C domain), a variable hinge (D domain), and C-terminal F regions. Ligand activation of class 1 steroid hormone receptors induces homo-or heterodimer formations, which interact with consensus or nonconsensus palindromic response elements. In contrast, class 2 receptors form heterodimers with the retinoic X receptor as a common partner, whereas class 3 and 4 orphan receptors act as homodimers or monomers and bind to direct response element repeats or single sites, respectively. The DNA binding domains of nuclear receptors all contain two zinc finger motifs that interact with similar half-site motifs; however, these interactions vary with the number of half-sites (1 or 2), their orientation, and spacing. Differences in nuclear receptor action are also determined by their other domains, which dictate differences in ligand binding, receptor dimerization, and interaction with other nuclear cofactors. Most orphan receptors were initially cloned and identified as members of the nuclear receptor family based on their domain structure and endogenous or exogenous ligands have subsequently been identified for many of these proteins (5-7).

Nerve growth factor-induced BA (NGFI-BA, Nur77) is an orphan nuclear receptor with no known endogenous ligands; however, recent studies on a series of methylene-substituted diindolylmethanes (C-DIM) have identified 1,1-bis(3 ¶-indolyl)-1-(phenyl)methane (DIM-C-Ph) and 1,1-bis(3 ¶-indolyl)-1-(p-anisyl)methane (DIM-C-pPhOCH 3 ) as Nur77 agonists. Nur77 is expressed in several colon cancer cell lines (RKO, SW480, HCT-116, HT-29, and HCT-15), and we also observed by immunostaining that Nur77 was overexpressed in colon tumors compared with normal colon tissue. DIM-C-Ph and DIM-C-pPhOCH 3 decreased survival and induced apoptosis in RKO colon cancer cells, and this was accompanied by induction of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein. The induction of apoptosis and TRAIL by DIM-C-pPhOCH 3 was significantly inhibited by a small inhibitory RNA for Nur77 (iNur77); however, it was evident from RNA interference studies that DIM-C-pPhOCH 3 also induced Nur77-independent apoptosis. Analysis of DIM-C-pPhOCH 3 -induced gene expression using microarrays identified several proapoptotic genes, and analysis by reverse transcription-PCR in the presence or absence of iNur77 showed that induction of programmed cell death gene 1 was Nur77 dependent, whereas induction of cystathionase and activating transcription factor 3 was Nur77 independent. DIM-C-pPhOCH 3 (25 mg/kg/d) also inhibited tumor growth in athymic nude mice bearing RKO cell xenografts. These results show that Nur77-active C-DIM compounds represent a new class of anti-colon cancer drugs that act through receptordependent and receptor-independent pathways. [Cancer Res 2007;67(2):674-83]

Methyl 2-cyano-3,11-dioxo-18b-olean-1,12-dien-30-oate (CDODAMe) is a synthetic derivative of glycyrrhetinic acid, a triterpenoid phytochemical found in licorice extracts. CDODA-Me inhibited growth of RKO and SW480 colon cancer cells and this was accompanied by decreased expression of Sp1, Sp3 and Sp4 protein and mRNA and several Sp-dependent genes including survivin, vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1 or Flt-1). CDODA-Me also induced apoptosis, arrested RKO and SW480 cells at G 2 /M, and inhibited tumor growth in athymic nude mice bearing RKO cells as xenografts. CDODA-Me decreased expression of microRNA-27a (miR-27a), and this was accompanied by increased expression of 2 miR-27a-regulated mRNAs, namely ZBTB10 (an Sp repressor) and Myt-1 which catalyzes phosphorylation of cdc2 to inhibit progression of cells through G 2 /M. Both CDODA-Me and antisense miR-27a induced comparable responses in RKO and SW480 cells, suggesting that the potent anticarcinogenic activity of CDODA-Me is due to repression of oncogenic miR-27a. ' UICCKey words: CDODA-Me; anticarcinogenicity; miR-27a; colon cancer; cell cycle MicroRNAs (miRNAs) are 20-25 bp oligonucleotides that interact with complementary binding sites in 3 0 -untranslated regions of target mRNAs to inhibit their expression by blocking translation or by decreasing mRNA stability.1,2 miRNA interactions with mRNA requires the overlap of 6-8 base pairs and, due to this relatively low stringency, computational studies show that miRNAs can potentially interact with several hundred mRNAs.Despite this lack of specificity, miRNAs have a profound effect on gene expression and cellular homeostasis and, in cancer cells, expression of several critical oncogenes and tumor suppressor genes are regulated by miRNA expression.3-6 miR-221 and miR-222 target the cyclin-dependent kinase inhibitor p27 6 and miR-21 decreases expression of several mRNAs including the tumor suppressor gene tropomyosin 1. 3 Recent studies in this laboratory showed that miR-27a targets ZBTB10 mRNA, a putative zinc finger protein that suppresses specificity protein (Sp) transcription factors and Sp-dependent gene expression. 7 The Sp transcription factors Sp1, Sp3 and Sp4 are highly expressed in cancer cell lines, and results of RNA interference studies show that Sp proteins regulate expression of angiogenic genes such as vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGFR1, Flt-1), VEGFR2 (KDR) and the antiapoptotic gene survivin. 8-14Betulinic acid and the nonsteroidal anti-inflammatory drug tolfenamic acid inhibit prostate and pancreatic cell and tumor growth through activation of proteasome-dependent degradation of Sp1, Sp3 and Sp4 proteins. 13,14 In our study, we show that methyl 2-cyano-3,11-dioxo-18b-olean-1,12-dien-30-oate (CDODA-Me) is highly cytotoxic to colon cancer cells and also decreases Sp and Sp-dependent genes and proteins. However, these effects are proteasome-independent. We now show for the first time that CDODA-Me acts through downregulation of...