Reactive oxygen species (ROS)-inducing anticancer agents such as phenethylisothiocyanate (PEITC) activate stress pathways for killing cancer cells. Here we demonstrate that PEITC-induced ROS decreased expression of microRNA 27a (miR-27a)/miR-20a:miR-17-5p and induced miR-regulated ZBTB10/ZBTB4 and ZBTB34 transcriptional repressors, which, in turn, downregulate specificity protein (Sp) transcription factors (TFs) Sp1, Sp3, and Sp4 in pancreatic cancer cells. Decreased expression of miR-27a/miR-20a:miR-17-5p by PEITC-induced ROS is a key step in triggering the miR-ZBTB Sp cascade leading to downregulation of Sp TFs, and this is due to ROS-dependent epigenetic effects associated with genome-wide shifts in repressor complexes, resulting in decreased expression of Myc and the Myc-regulated miRs. Knockdown of Sp1 alone by RNA interference also induced apoptosis and decreased pancreatic cancer cell growth and invasion, indicating that downregulation of Sp transcription factors is an important common mechanism of action for PEITC and other ROS-inducing anticancer agents.
ZBTB4 is a transcriptional repressor and examination of publically-available microarray data sets demonstrated an inverse relationship in the prognostic value and expression of ZBTB4 and the histone methyltransferase EZH2 in tumors from breast cancer patients. The possibility of functional interactions between EZH2 and ZBTB4 was investigated in breast cancer cells and the results showed that EZH2 is directly suppressed by ZBTB4 which in turn is regulated (suppressed) by miR-106b and other paralogues from the miR-17-92, miR-106b-25 and miR-106a-363 clusters that are highly expressed in breast and other tumors. ZBTB4 also acts a suppressor of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4, and RNA interference studies show that Sp proteins are required for EZH2 expression. The prediction analysis results from breast cancer patient array data sets confirm an association of Sp1-dependent EZH2 gene signature with decreased survival of breast cancer patients. Disruption of oncogenic miR-ZBTB4 signaling axis by anticancer agent such as betulinic acid that induce down-regulation of Sp proteins in breast cancer cells resulted in inhibition of tumor growth and colonization of breast cancer cells in a mouse model. Thus, EZH2 is reciprocally regulated by a novel signaling network consisting of Sp proteins, oncogenic miRs and ZBTB4, and modulation of this gene network is a novel therapeutic approach for treatment of breast cancer and possibly other cancers.
Sp, Specificity protein; ZBTB4, Zinc finger BTB domain protein 4; miR, microRNA; BA, Betulinic acid; EMSA, Electrophoretic mobility shift assay; Chip, Chromatin immunoprecipitation assay
Metformin is a widely used antidiabetic drug, and epidemiology studies for pancreatic and other cancers indicate that metformin exhibits both chemopreventive and chemotherapeutic activities. Several metformin-induced responses and genes are similar to those observed after knockdown of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 by RNA interference, and we hypothesized that the mechanism of action of metformin in pancreatic cancer cells was due, in part, to downregulation of Sp transcription factors. Treatment of Panc1, L3.6pL and Panc28 pancreatic cancer cells with metformin downregulated Sp1, Sp3 and Sp4 proteins and several pro-oncogenic Sp-regulated genes including bcl-2, survivin, cyclin D1, vascular endothelial growth factor and its receptor, and fatty acid synthase. Metformin induced proteasome-dependent degradation of Sps in L3.6pL and Panc28 cells, whereas in Panc1 cells metformin decreased microRNA-27a and induced the Sp repressor, ZBTB10, and disruption of miR-27a:ZBTB10 by metformin was phosphatase dependent. Metformin also inhibited pancreatic tumor growth and downregulated Sp1, Sp3 and Sp4 in tumors in an orthotopic model where L3.6pL cells were injected directly into the pancreas. The results demonstrate for the first time that the anticancer activities of metformin are also due, in part, to downregulation of Sp transcription factors and Sp-regulated genes.
Specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 are highly expressed in rhabdomyosarcoma (RMS) cells. In tissue arrays of RMS tumor cores from 71 patients, 80% of RMS patients expressed high levels of Sp1 protein, whereas low expression of Sp1 was detected in normal muscle tissue. The non-steroidal anti-inflammatory drug (NSAID) tolfenamic acid (TA) inhibited growth and migration of RD and RH30 RMS cell lines and also inhibited tumor growth in vivo using a mouse xenograft (RH30 cells) model. The effects of TA were accompanied by downregulation of Sp1, Sp3, Sp4 and Sp-regulated genes in RMS cells and tumors, and the role of Sp protein downregulation in mediating inhibition of RD and RH30 cell growth and migration was confirmed by individual and combined knockdown of Sp1, Sp3 and Sp4 proteins by RNA interference. TA treatment and Sp knockdown in RD and RH30 cells also showed that four genes that are emerging as individual drug targets for treating RMS, namely c-MET, insulin-like growth factor receptor (IGFR), PDGFRα and CXCR4, are also Sp-regulated genes. These results suggest that NSAIDs such as TA may have potential clinical efficacy in drug combinations for treating RMS patients.
Tolfenamic acid; Sp proteins; downregulation; RMS cells
Triterpenoids such as betulinic acid (BA) and synthetic analogs of oleanolic acid [2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO)] and glycyrrhetinic acid [2-cyano-3,11-dioxo-18β-oleana-1,12-dien-30-oc acid (CDODA)] are potent anticancer agents that exhibit antiproliferative, antiangiogenic, anti-inflammatory and pro-apoptotic activities. Although their effects on multiple pathways have been reported, unifying mechanisms of action have not been reported. Studies in this laboratory have now demonstrated that several triterpenoids including BA and some derivatives, celastrol, methyl ursolatee, β-boswellic acid derivatives, and the synthetic analogs CDDO, CDODA and their esters decreased expression of specificity protein (Sp) transcription factors and several pro-oncogenic Sp-regulated genes in multiple cancer cell lines. The mechanisms of this response are both compound- and cell context-dependent and include activation of both proteasome-dependent and -independent pathways. Triterpenoid-mediated induction of reactive oxygen species (ROS) has now been characterized as an important proteasome-independent pathway for downregulation of Sp transcription factors. ROS decreases expression of microRNA-27a (miR-27a) and miR-20a/miR-17-5p and this results in the induction of the transcriptional “Sp-repressors” ZBTB10 and ZBTB4, respectively, which in turn downregulate Sp and Sp-regulated genes. Triterpenoids also activate or deactive nuclear receptors and G-protein coupled receptors, and these pathways contribute to their antitumorigenic activity and may also play a role in targeting Sp1, Sp3 and Sp4 which are highly overexpressed in multiple cancers and appear to be important for maintaining the cancer phenotype.
Sp transcription factors; downregulation; reactive oxygen species
HOTAIR is a long intervening non-coding RNA (lincRNA) that associates with the Polycomb Repressive Complex 2 (PRC2) and overexpression is correlated with poor survival for breast, colon and liver cancer patients. In this study, we show that HOTAIR expression is increased in pancreatic tumors compared to non-tumor tissue and is associated with more aggressive tumors. Knockdown of HOTAIR (siHOTAIR) by RNA interference shows that HOTAIR plays an important role in pancreatic cancer cell invasion and as reported in other cancer cell lines. In contrast, HOTAIR knockdown in Panc1 and L3.6pL pancreatic cancer cells that overexpress this lincRNA decreased cell proliferation, altered cell cycle progression, and induced apoptosis, demonstrating an expanded function for HOTAIR in pancreatic cancer cells compared to other cancer cell lines. Results of gene array studies showed that there was minimal overlap between HOTAIR-regulated genes in pancreatic vs. breast cancer cells and HOTAIR uniquely suppressed several interferon-related genes and gene sets related to cell cycle progression in pancreatic cancer cells and tumors. Analysis of selected genes suppressed by HOTAIR in Panc1 and L3.6 pL cells showed by knockdown of EZH2 and chromatin immunoprecipitation assays that HOTAIR-mediated gene repression was both PRC2-dependent and -independent. HOTAIR knockdown in L3.6pL cells inhibited tumor growth in mouse xenograft model, further demonstrating the pro-oncogenic function of HOTAIR in pancreatic cancer.
HOTAIR; invasion; cell cycle progression; pro-oncogenic; prognostic
Celastrol (CSL) is a naturally occurring triterpenoid acid that exhibits anticancer activity, and in KU7 and 253JB-V bladder cells, CSL induced apoptosis, inhibited growth, colony formation and migration and CSL decreased bladder tumor growth in vivo. CSL also decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and several Sp-regulated genes/proteins including vascular endothelial growth factor, survivin and cyclin D1 and fibroblast growth factor receptor-3, a potential drug target for bladder cancer therapy, has now been characterized as an Sp-regulated gene downregulated by CSL. The mechanism of Sp downregulation by CSL was cell context-dependent due to activation of proteosome-dependent (KU7) and -independent (253JB-V) pathways. In 253JB-V cells, CSL induced reactive oxygen species (ROS) and inhibitors of ROS blocked CSL-induced growth inhibition and repression of Sp1, Sp3 and Sp4. This response was due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of miR-27a and miR-20a/17-5p, respectively, which regulate expression of these transcriptional repressors. Thus, the anticancer activity of CSL in 253JB-V cells is due to induction of ROS and ROS-mediated induction of Sp repressors (ZBTB4/ZBTB10) through downregulation of miR-27a and miR-20a/17-5p.
We hypothesized that the anticancer activity of cannabinoids was linked to induction of phosphatases.
Materials and Methods
The effects of cannabidiol (CBD) and the synthetic cannabinoid WIN-55,212 (WIN) on LNCaP (prostate) and SW480 (colon) cancer cell proliferation were determined by cell counting; apoptosis was determined by cleavage of poly(ADP)ribose polymerase (PARP) and caspase-3 (Western blots); and phosphatase mRNAs were determined by real-time PCR. The role of phosphatases and cannabinoid receptors in mediating CBD- and WIN-induced apoptosis was determined by inhibition and receptor knockdown.
CBD and WIN inhibited LNCaP and SW480 cell growth and induced mRNA expression of several phosphatases, and the phosphatase inhibitor sodium orthovanadate significantly inhibited cannabinoid-induced PARP cleavage in both cell lines, whereas only CBD-induced apoptosis was CB1 and CB2 receptor-dependent.
Cannabinoid receptor agonists induce phosphatases and phosphatase-dependent apoptosis in cancer cell lines; however, the role of the CB receptor in mediating this response is ligand-dependent.
Cannabinoids; apoptosis; protein tyrosine phosphatases; dual-specificity phosphatases
Acetylsalicylic acid (aspirin) is highly effective for treating colon cancer patients postdiagnosis; however, the mechanisms of action of aspirin in colon cancer are not well defined. Aspirin and its major metabolite sodium salicylate induced apoptosis and decreased colon cancer cell growth and the sodium salt of aspirin also inhibited tumor growth in an athymic nude mouse xenograft model. Colon cancer cell growth inhibition was accompanied by downregulation of Sp1, Sp3 and Sp4 proteins and decreased expression of Sp-regulated gene products including bcl-2, survivin, VEGF, VEGFR1, cyclin D1, c-MET and p65 (NFκB). Moreover, we also showed by RNA interference that β-catenin, an important target of aspirin in some studies, is an Sp-regulated gene. Aspirin induced nuclear caspase-dependent cleavage of Sp1, Sp3 and Sp4 proteins and this response was related to sequestration of zinc ions since addition of zinc sulfate blocked aspirin-mediated apoptosis and repression of Sp proteins. The results demonstrate an important underlying mechanism of action of aspirin as an anticancer agent and, based on the rapid metabolism of aspirin to salicylate in humans and the high salicylate/aspirin ratios in serum, it is likely that the anticancer activity of aspirin is also due to the salicylate metabolite.
Ascorbic acid (vitamin C) inhibits cancer cell growth and there is a controversy regarding the cancer chemoprotective effects of pharmacologic doses of this compound which exhibits pro-oxidant activity. We hypothesized that the anticancer activity of pharmacologic doses of ascorbic acid (< 5 mM) is due, in part, to reactive oxygen species (ROS)-dependent downregulation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and Sp-regulated genes. In this study, ascorbic acid (1 – 3 mM) decreased RKO and SW480 colon cancer cell proliferation and induced apoptosis and necrosis and this was accompanied by downregulation of Sp1, Sp3 and Sp4 proteins. In addition, ascorbic acid decreased expression of several Sp-regulated genes that are involved in cancer proliferation [hepatocyte growth factor receptor (c-Met), epidermal growth factor receptor (EGFR) and cyclin D1], survival (survivin and bcl-2), and angiogenesis [vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2)]. Other pro-oxidants such as hydrogen peroxide exhibited similar activities in colon cancer cells and cotreatment with glutathione inhibited these responses. This study demonstrates for the first time that the anticancer activities of ascorbic acid are due, in part, to ROS-dependent repression of Sp transcription factors.
Ascorbic acid; colon cancer; ROS; peroxide; Sp downregulation
Ethyl 2-((2,3-bis(nitrooxy)propyl)disulfanyl)benzoate (GT-094) is a novel NO chimera containing an NSAID and NO moieties and also a disulfide pharmacophore that in itself exhibits cancer chemopreventive activity. In this study, the effects and mechanism of action of GT-094 were investigated in RKO and SW480 colon cancer cells. GT-094 inhibited cell proliferation and induced apoptosis in both cell lines and this was accompanied by decreased mitochondrial membrane potential (MMP) and induction of reactive oxygen species (ROS), and these responses were reversed after cotreatment with the antioxidant glutathione. GT-094 also downregulated genes associated with cell growth [cyclin D1, hepatocyte growth factor receptor (c-Met), epidermal growth factor receptor (EGFR)], survival (bcl-2, survivin), and angiogenesis [vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2)]. Results of previous RNA interference studies in this laboratory has shown that these genes are regulated, in part, by specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 that are overexpressed in colon and other cancer cell lines and not surprisingly, GT-094 also decreased Sp1, Sp3 and Sp4 in colon cancer cells. GT-094-mediated repression of Sp and Sp-regulated gene products was due to downregulation of microRNA-27a (miR-27a) and induction of ZBTB10, an Sp repressor that is regulated by miR-27a in colon cancer cells. Moreover, the effects of GT-094 on Sp1, Sp3, Sp4, miR-27a and ZBTB10 were also inhibited by glutathione suggesting that the anticancer activity of GT-094 in colon cancer cells is due, in part, to activation of an ROS-miR-27a:ZBTB10-Sp transcription factor pathway.
GT-094; NO-NSAID; Sp proteins; colon cancer; miR-27a:ZBTB10
Arsenic trioxide exhibits antiproliferative, antiangiogenic and proapoptotic activity in cancer cells, and many genes associated with these responses are regulated by specificity protein (Sp) transcription factors. Treatment of cancer cells derived from urologic (bladder and prostate) and gastrointestinal (pancreas and colon) tumors with arsenic trioxide demonstrated that these cells exhibited differential responsiveness to the antiproliferative effects of this agent and this paralleled their differential repression of Sp1, Sp3 and Sp4 proteins in the same cell lines. Using arsenic trioxide responsive KU7 and non-responsive 253JB-V bladder cancer cells as models, we show that in KU7 cells, ≤ 5 μM arsenic trioxide decreased Sp1, Sp3 and Sp4 and several Sp-dependent genes and responses including cyclin D1, epidermal growth factor receptor, bcl-2, survivin and vascular endothelial growth factor, whereas at concentrations up to 15 μM, minimal effects were observed in 253JB-V cells. Arsenic trioxide also inhibited tumor growth in athymic mice bearing KU7 cells as xenografts, and expression of Sp1, Sp3 and Sp4 was significantly decreased. Inhibitors of oxidative stress such as glutathione or dithiothreitol protected KU7 cells from arsenic trioxide-induced antiproliferative activity and Sp repression, whereas glutathione depletion sensitized 253JB-V cells to arsenic trioxide. Mechanistic studies suggested that arsenic trioxide-dependent downregulation of Sp and Sp-dependent genes was due to decreased mitochondrial membrane potential and induction of reactive oxygen species, and the role of peroxides in mediating these responses was confirmed using hydrogen peroxide.
Arsenic trioxide; anticancer activity; Sp repression; ROS
The epidermal growth factor receptor (EGFR) is an important chemotherapeutic target for tyrosine kinase inhibitors and antibodies that block the extracellular domain of EGFR. Betulinic acid (BA) and curcumin inhibited bladder cancer cell growth and downregulated specificity protein (Sp) transcription factors, and this was accompanied by decreased expression of EGFR mRNA and protein levels. EGFR, a putative Sp-regulated gene, was also decreased in cells transfected with a cocktail (iSp) containing small inhibitory RNAs for Sp1, Sp3 and Sp4, and RNA interference with individual Sp knockdown indicated that EGFR expression was primarily regulated by Sp1 and Sp3. BA, curcumin and iSp also decreased phosphorylation of Akt in these cells and downregulation of EGFR by BA, curcumin and iSp was accompanied by induction of LC3 and autophagy which is consistent with recent studies showing that EGFR suppresses autophagic cell death. The results show that EGFR is an Sp-regulated gene in bladder cancer, and drugs such as BA and curcumin that repress Sp proteins also ablate EGFR expression. Thus, compounds such as curcumin and BA that downregulate Sp transcription factors represent a novel class of anticancer drugs that target EGFR in bladder cancer cells and tumors by inhibiting receptor expression.
EGFR suppression; Sp transcription factors; curcumin; betulinic acid
A novel series of methylene-substituted DIMs (C-DIMs), namely 1,1-bis(3'-indolyl)-1-(p-substituted phenyl)methanes containing t-butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC6H5) groups inhibit proliferation of invasive estrogen receptor-negative MDA-MB-231 and MDA-MB-453 human breast cancer cell lines with IC50 values between 1-5 uM. The main purpose of this study was to investigate the pathways of C-DIM-induced cell death.
The effects of the C-DIMs on apoptotic, necrotic and autophagic cell death were determined using caspase inhibitors, measurement of lactate dehydrogenase release, and several markers of autophagy including Beclin and light chain associated protein 3 expression (LC3).
The C-DIM compounds did not induce apoptosis and only DIM-C-pPhCF3 exhibited necrotic effects. However, treatment of MDA-MB-231 and MDA-MB-453 cells with C-DIMs resulted in accumulation of LC3-II compared to LC3-I protein, a characteristic marker of autophagy, and transient transfection of green fluorescent protein-LC3 also revealed that treatment with C-DIMs induced a redistribution of LC3 to autophagosomes after C-DIM treatment. In addition, the autofluorescent drug monodansylcadaverine (MDC), a specific autophagolysosome marker, accumulated in vacuoles after C-DIM treatment, and western blot analysis of lysates from cells treated with C-DIMs showed that the Beclin 1/Bcl-2 protein ratio increased.
The results suggest that C-DIM compounds may represent a new mechanism-based agent for treating drug-resistant ER-negative breast tumors through induction of autophagy.
1,1-Bis(3′-indolyl)-1-(p-bromophenyl)methane (DIM-C-pPhBr) and the 2,2′-dimethyl analog (2,2′-diMeDIM-C-pPhBr) inhibit proliferation and induce apoptosis in SW480 colon and Panc28 pancreatic cancer cells. In this study, treatment with 10–20 μM concentrations of these compounds for 24 hr induced cleaved PARP and decreased survivin protein and mRNA expression in both cell lines. However, results of time course studies show that DIM-C-pPhBr and 2,2′-diMeDIM-C-pPhBr decrease survivin protein within 2 hr after treatment, whereas survivin mRNA levels were decreased only at later time points indicating activation of transcription-independent and -dependent pathways for downregulation of survivin. In addition, we also observed that γ-radiation inhibited pancreatic and colon cancer cell growth and this was associated with enhanced expression of survivin after 24 (SW480) or 24 and 48 (Panc28) hr and correlated with previous studies on the role of survivin in radiation-resistance. However, in cells cotreated with γ-radiation plus DIM-C-pPhBr or 2,2′-diMeDIM-C-pPhBr, induction of survivin by γ-radiation was inhibited after cotreatment with both compounds, suggesting applications for these drugs in combination cancer chemotherapy with γ-radiation.
DIM analogs; survivin downregulation; gamma-radiation-induced survivin
Methyl 2-cyano-3,11-dioxo-18β-olean-1,12-dien-30-oate (CDODA-Me) 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 G2/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 two miR-27a-regulated mRNAs, namely ZBTB10 (an Sp repressor) and Myt-1 which catalyzes phosphorylation of cdc2 to inhibit progression of cells through G2/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.
CDODA-Me; anticarcinogenicity; miR-27a; colon cancer; cell cycle
Methyl 2-cyano-3,11-dioxo-18β-olean-1,12-dien-30-oate (CDODA-Me) is a synthetic triterpenoid derived from glycyrrhetinic acid, a bioactive phytochemical in licorice, CDODA-Me inhibits growth of Panc1 and Panc28 pancreatic cancer cell lines and activates peroxisome proliferator-activated receptor γ (PPARγ)-dependent transactivation in these cells. CDODA-Me also induced p21 and p27 protein expression and downregulates cyclin D1; however, these responses were receptor-independent. CDODA-Me induced apoptosis in Panc1 and Panc28 cells, and this was accompanied by receptor-independent induction of the proapoptotic proteins early growth response-1 (Egr-1), nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), and activating transcription factor-3 (ATF3). Induction of NAG-1 and Egr-1 by CDODA-Me was dependent on activation of phosphatidylinositol-3-kinase (PI3-K) and/or p42 and p38 mitogen-activated protein kinase (MAPK) pathways but there were differences between Panc28 and Panc1 cells. Induction of NAG-1 in Panc28 cells was p38-MAPK- and PI3-K-dependent but Egr-1-independent, whereas induction in Panc1 cells was associated with activation of p38-MAPK, PI3-K and p42-MAPK and was only partially Egr-1-dependent. This is the first report of the induction of the proapoptotic protein NAG-1 in pancreatic cancer cells.
CDODA-Me; pancreatic cancer; apoptosis
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 – 25 µM 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). Since 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 downregulation 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 κB (NFκB)-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 demonstrate 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.
curcumin; Sp proteins; survivin; VEGF; VEGFR1; bladder cancer; inhibition
Derivatives of oleanolic acid, ursolic acid and glycyrrhetinic acid substituted with electron withdrawing groups at the 2-position in the A-ring which also contains a 1-en-3-one structure are potent inhibitors of cancer cell growth. In this study, we have compared the effects of several 2-substituted analogs of triterpenoid acid methyl esters derived from ursolic and glycyrrhetinic acid on proliferation of KU7 and 253JB-V bladder and Panc-1 and Panc-28 pancreatic cancer cells. The results show that the 2-cyano and 2-trifluoromethyl derivatives were the most active compounds. The glycyrrhetinic acid derivatives with the rearranged C-ring containing the 9(11)-en-12-one structure were generally more active than the corresponding 12-en-11-one isomers. However, differences in growth inhibitory IC50 values were highly variable and dependent on the 2- substitutent (CN vs. CF3) and cancer cell context.
glycyrrhetinate analogs; growth inhibition; bladder cancer; pancreatic cancer