Inhibition of pituitary tumor-transforming gene-1 in thyroid cancer cells by drugs that decrease specificity proteins

Anti-Proliferative and Anti-Migratory Activity of Licorice Extract and Glycyrrhetinic Acid on Papillary Thyroid Cancer Cell Cultures

Papillary thyroid cancer (PTC) is the 8th most common cancer among women overall. Licorice contains over 300 active compounds, many of them with anti-cancer properties. Glycyrrhetinic acid (GA) is a major component of licorice. The aim of this study was to investigate the potential anti-proliferative effects of licorice and GA on PTC cell cultures. Licorice extract (LE) was produced from the root and tested on BCPAP and K1 cell lines, as well as GA and aldosterone. We used the MTT test to investigate the anti-proliferative activity, the wound healing test for the migratory activity, and finally, we analyzed cell cycle distribution, apoptosis, and oxidative stress after LE, GA, or aldosterone incubation. Both LE and GA reduced cell viability at 48 h and cell migration at 24 h in both PTC cultures. Aldosterone reduced cell migration only in K1 cells. LE and GA induced cell cycle arrest in the G0/G1 phase in the BCPAP cell line, while LE and aldosterone induced it in the K1 culture. GA but not LE increased the apoptosis rate in both cell lines, whereas LE but not GA increased oxidative stress in both cultures. This study presents the first evidence of the in vitro anti-proliferative and anti-migratory activity of LE and GA on PTC.

Asiaticoside Down-Regulates HIF-1α to Inhibit Proliferation, Migration, and Angiogenesis in Thyroid Cancer Cells

Background

Thyroid cancer (TC), the most prevalent endocrine malignancy, has been subjected to various treatment methods. However, the efficacy of asiaticoside (AC) for treating TC remains uncertain.

Aims

To explore the impact of AC on TC and determine its potential mechanisms of action.

Study Design

In vitro and in vivo cell line study.

Methods

We evaluated the effects of AC on human TC cell lines, namely TPC-1 and FTC-133. Both in vitro and in vivo experimental validations were conducted.

Results

AC significantly diminished the viability and proliferation of TC cells based on the CCK-8 assay and Edu staining findings. Migration and invasion assays revealed that AC effectively curtailed the migration and invasiveness of TC cells. The tube formation assay demonstrated that AC substantially impeded TC cell-induced angiogenesis. Western blot assay revealed that AC significantly reduced the expression levels of TRAF6, HIF-1α, and VEGFA, indicating that AC could potentially exert its anticancer effect by inhibiting the TRAF6/HIF1α pathway. Our in vivo experiments, which involved administering AC to BALB/c nude mice injected with TPC-1 cells, demonstrated significant inhibition of tumor growth and reduction in the expression of Ki-67, TRAF6, HIF-1α, and VEGFA.

Conclusion

Our study highlights the significant inhibitory effect of AC on TC, offering fresh insights and potential drug candidates for TC treatment.

SP4 Facilitates Esophageal Squamous Cell Carcinoma Progression by Activating PHF14 Transcription and Wnt/Β-Catenin Signaling

Specificity protein 4 transcription factor (SP4), a member of the Sp/Krüppel-like family (KLF), could bind to GT and GC box promoters, and plays an essential role in transcriptional activating. Despite SP4 having been detected to be highly expressed in a variety of human tumors, its biological effect and underlying molecular mechanism in esophageal squamous cell carcinoma (ESCC) remains unclear. Our research discovered that high SP4 expression is detected in primary ESCC specimens and cell lines and is strongly associated with the ESCC tumor grade and poor prognosis. In vitro, knockdown of SP4 suppressed cell proliferation and cell-cycle progression and promoted apoptosis, whereas overexpression of SP4 did the opposite. In vivo, inhibiting SP4 expression in ESCC cells suppresses tumor growth. Subsequently, we demonstrated that SP4 acts as the transcriptional upstream of PHF14, which binds to PHF14 promoter region, thus promoting PHF14 transcription. PHF14 was also significantly expressed in patient tissues and various ESCC cell lines and its expression promoted cell proliferation and inhibited apoptosis. Moreover, knockdown of SP4 inhibited the Wnt/β-catenin signaling pathway, whereas overexpression of PHF14 eliminated the effects of SP4 knockdown in ESCC cells. These results demonstrate that SP4 activates the Wnt/β-catenin signaling pathway by driving PHF14 transcription, thereby promoting ESCC progression, which indicates that SP4 might act as a prospective prognostic indicator or therapeutic target for patients with ESCC.

IMPLICATIONS

This study identified SP4/PH14 axis as a new mechanism to promote the progression of ESCC, which may serve as a novel therapeutic target for patients with ESCC.

Betulinic acid in the treatment of breast cancer: Application and mechanism progress

Betulinic acid (BA) is a pentacyclic triterpene compound, which can be obtained by separation, chemical synthesis and biotransformation. BA has excellent biological activities, especially its role in the treatment of breast cancer deserves attention. Its mechanisms mainly include inducing mitochondrial oxidative stress, regulating specific protein (Sp) transcription factors, inhibiting breast cancer metastasis, inhibiting glucose metabolism and NF-κB pathway. In addition, BA can also increase the sensitivity of breast cancer cells to other chemotherapy drugs such as paclitaxel and reduce its toxic side effects. This article reviews the application and possible mechanism of BA in the treatment of breast cancer.

The genetic polymorphisms in the SP4 gene and the risk of gastric cancer

Aim: Gastric cancer (GC) is the leading cause of cancer death, and is associated with host genetic factors. This study aimed to determine the impact of SP4 polymorphisms on GC. Materials & methods: Four hundred and eighty-nine GC patients and 481 healthy subjects were recruited. The association between single nucleotide polymorphisms and GC risk was investigated by logistic regression analysis. Results: It was observed that rs39302 and rs7811417 were related to a decreased GC risk. Stratified analyses showed that rs39302 decreased GC susceptibility at ages ≤60 years, in men, GC patients who had previously smoked and drank. rs7811417 had a risk-decreasing impact on the patients aged ≤60 years, in men, GC patients who were nonsmoking and nondrinking. rs35929923 decreased the GC risk of patients in grade III-IV and the lymph node metastasis subgroup. Conclusion: SP4 gene polymorphisms are associated with GC risk.

Glycyrrhetinic acid induces oxidative/nitrative stress and drives ferroptosis through activating NADPH oxidases and iNOS, and depriving glutathione in triple-negative breast cancer cells

Reactive oxygen species (ROS)/reactive nitrogen species (RNS)-mediated ferroptosis becomes a novel effective target for anti-cancer treatment. In the present study, we tested the hypothesis that 18-β-glycyrrhetinic acid (GA), an active compound from medicinal herbal Licorice, could induce the production of ROS/RNS, increase lipid peroxidation and trigger ferroptosis in MDA-MB-231 triple negative breast cancer cells. To confirm the GA's anti-cancer effects, we detected cell viability, apoptosis and ferroptosis in the MDA-MB-231 cells. To explore the effects of GA on inducing ferroptosis, we measured mitochrondrial morphology, ROS/RNS production, lipid peroxidation, ferrous ion, glutathione (GSH), System Xc^-, GPX4, glutathione peroxidases (GPX), NADPH oxidase and iNOS in the MDA-MB-231 cells. The major discoveries are included as below: (1) GA treatment selectively decreased cell viability and induced ferroptosis companied with the increased lipid peroxidation and ferrous ion in the MDA-MB-231 triple negative breast cancer cells. Iron chelator deferoxamine mesylate (DFO) and ferroptosis inhibitor Ferrostatin-1 abolished the effects of GA. (2) GA treatment up-regulated the expression and activity of NADPH oxidase and iNOS, and increased ROS/RNS productions (O₂^•-, ^•OH, NO and ONOO^-) in the MDA-MB-231 cells; (3) GA down-regulated the expression of SLC7A11 of System X_c^-, decreased glutathione (GSH) level and inhibited GPX activity. Taken together, GA could promote the productions of ROS and RNS via activating NADPH oxidases and iNOS, and decreasing GSH and GPX activity, subsequently aggravating lipid peroxidation and triggering ferroptosis in triple-negative breast cancer cells.

Sp1 Targeted PARP1 Inhibition Protects Cardiomyocytes From Myocardial Ischemia-Reperfusion Injury via Downregulation of Autophagy

Myocardial ischemia–reperfusion injury (MIRI), characterized by post-ischemic cardiomyocytes death and reperfusion myocardial damage, is a lethal yet unresolved complication in the treatment of acute myocardial infarction (AMI). Previous studies have demonstrated that poly(ADP-ribose) polymerase-1 (PARP1) participates in the progression of various cardiovascular diseases, and various reports have proved that PARP1 can be a therapeutic target in these diseases, but whether it plays a role in MIRI is still unknown. Therefore, in this study, we aimed to explore the role and mechanism of PARP1 in the development of MIRI. Firstly, we demonstrated that PARP1 was activated during MIRI-induced myocardial autophagy in vitro. Moreover, PARP1 inhibition protected cardiomyocytes from MIRI through the inhibition of autophagy. Next, we discovered that specificity protein1 (Sp1), as a transcription factor of PARP1, regulates its target gene PARP1 through binding to its target gene promoter during transcription. Furthermore, silencing Sp1 protected cardiomyocytes from MIRI via the inhibition of PARP1. Finally, the functions and mechanisms of PARP1 in the development of MIRI were also verified in vivo with SD rats model. Based on these findings, we concluded that PARP1 inhibition protects cardiomyocytes from MIRI through the inhibition of autophagy, which is targeted by Sp1 suppression. Therefore, the utilization of PARP1 exhibits great therapeutic potential for MIRI treatment in future.

Reactive Oxygen Species (ROS)-Inducing Triterpenoid Inhibits Rhabdomyosarcoma Cell and Tumor Growth through Targeting Sp Transcription Factors

Methyl 2-trifluoromethyl-3,11-dioxo-18β-olean-1,12-dien-3-oate (CF₃DODA-Me) is derived synthetically from glycyrrhetinic acid, a major component of licorice, and this compound induced reactive oxygen species (ROS) in RD and Rh30 rhabdomyosarcoma (RMS) cells. CF₃DODA-Me also inhibited growth and invasion and induced apoptosis in RMS cells, and these responses were attenuated after cotreatment with the antioxidant glutathione, demonstrating the effective anticancer activity of ROS in RMS. CF₃DODA-Me also downregulated expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and prooncogenic Sp-regulated genes including PAX3-FOXO1 (in Rh30 cells). The mechanism of CF₃DODA-Me-induced Sp-downregulation involved ROS-dependent repression of c-Myc and cMyc-regulated miR-27a and miR-17/20a, and this resulted in induction of the miRNA-regulated Sp repressors ZBTB4, ZBTB10, and ZBTB34. The cell and tumor growth effects of CF₃DODA-Me further emphasize the sensitivity of RMS cells to ROS inducers and their potential clinical applications for treating this deadly disease. IMPLICATIONS: CF₃DODA-Me and HDAC inhibitors that induce ROS-dependent Sp downregulation could be developed for clinical applications in treating rhabdomyosarcoma.

Betulinic acid as apoptosis activator: Molecular mechanisms, mathematical modeling and chemical modifications

A natural product betulinic acid (BA) has gained a huge significance in the recent years for its strong cytotoxicity. Surprisingly, in spite of being an interesting cancer protecting agent on a variety of tumor cells, the normal cells and tissues are rarely affected by BA. Betulinic acid and analogues (BAs) generally exert through the mechanisms that provokes an event of direct cell death and bypass the resistance to normal chemotherapeutics. Although the major mechanism associated with its ability to induce direct cell death is mitochondrial apoptosis, there are several other mechanisms explored recently. Importantly, mathematical modeling of apoptosis has been an important tool to explore the precise mechanism involved in mitochondrial apoptosis. Thus, this review is an endeavor to sum up the molecular mechanisms underlying the action of BA and future directions to apply mathematical modeling technique to better understand the precise mechanism of BA-induced apoptosis. The last section of the review encompasses the plausible structural modifications and formulations to enhance the therapeutic efficacy of BA.

CF3DODA-Me induces apoptosis, degrades Sp1, and blocks the transformation phase of the blebbishield emergency program

Cancer stem cells are capable of undergoing cellular transformation after commencement of apoptosis through the blebbishield emergency program in a VEGF-VEGFR2-dependent manner. Development of therapeutics targeting the blebbishield emergency program would thus be important in cancer therapy. Specificity protein 1 (Sp1) orchestrates the transcription of both VEGF and VEGFR2; hence, Sp1 could act as a therapeutic target. Here, we demonstrate that CF3DODA-Me induced apoptosis, degraded Sp1, inhibited the expression of multiple drivers of the blebbishield emergency program such as VEGFR2, p70S6K, and N-Myc through activation of caspase-3, inhibited reactive oxygen species; and inhibited K-Ras activation to abolish transformation from blebbishields as well as transformation in soft agar. These findings confirm CF3DODA-Me as a potential therapeutic candidate that can induce apoptosis and block transformation from blebbishields.

Bardoxolone Methyl and a Related Triterpenoid Downregulate cMyc Expression in Leukemia Cells

Structurally related pentacyclic triterpenoids methyl 2-cyano-3,12-dioxoolean-1,9-dien-28-oate [bardoxolone-methyl (Bar-Me)] and methyl 2-trifluoromethyl-3,11-dioxoolean-1,12-dien-30-oate (CF3DODA-Me) contain 2-cyano-1-en-3-one and 2-trifluoromethyl-1-en-3-one moieties, respectively, in their A-rings and differ in the position of their en-one structures in ring C. Only Bar-Me forms a Michael addition adduct with glutathione (GSH) and inhibits IKKβ phosphorylation. These differences may be due to steric hindrance by the 11-keto group in CF3DODA-Me, which prevents Michael addition by the conjugated en-one in the A-ring. In contrast, both Bar-Me and CF3DODA-Me induce reactive oxygen species in HL-60 and Jurkat leukemia cells, inhibit cell growth, induce apoptosis and differentiation, and decrease expression of specificity proteins (Sp) 1, 3, and 4, and cMyc, and these effects are significantly attenuated after cotreatment with the antioxidant GSH. In contrast to solid tumor-derived cells, cMyc and Sp transcriptions are regulated independently and cMyc plays a more predominant role than Sp transcription factors in regulating HL-60 or Jurkat cell proliferation and differentiation compared with that observed in cells derived from solid tumors.

CDODA-Me decreases specificity protein transcription factors and induces apoptosis in bladder cancer cells through induction of reactive oxygen species

OBJECTIVE

The objective is to determine whether methyl 2-cyano-3,11-dioxo-18b-olean-1,12-dien-30-oate (CDODA-Me) has therapeutic potential in bladder cancer. We investigated the effects of CDODA-Me on the growth and survival of bladder cancer cells, and expression of specificity protein (Sp) transcription factors that regulate genes associated with cancer cell proliferation and survival.

METHODS

J82, RT4P, and 253JB-V bladder cancer cell lines were treated with vehicle alone or with CDODA-Me with or without the antioxidant l-glutathione. Cell viability and DNA fragmentation were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and propidium iodide-fluorescence-activated cell sorting (FACS) analysis, respectively. Intracellular reactive oxygen species (ROS) were measured by 2',7'-dichlorofluorescin diacetate-FACS analysis. We assessed CDODA's effects on the levels of Sp and Sp-regulated proteins and induction of apoptosis in bladder cancer cells by Western blotting. We also assessed the anticancer effects of CDODA-Me in nude mice bearing RT4v6 bladder cancer.

RESULTS

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and FACS analysis revealed that CDODA-Me inhibited the proliferation and survival of the 3 bladder cancer cell lines in a dose-dependent manner. FACS analysis also indicated that CDODA-Me-induced intracellular ROS, and Western blot analysis indicated that CDODA-Me decreased levels of Sp and Sp-regulated proteins and induced apoptosis in a dose-dependent and time-dependent manner. l-Glutathione attenuated CDODA-Me's down-regulation of Sp and Sp-regulated proteins. Compared with the control treatment, CDODA-Me substantially inhibited tumor growth in vivo.

CONCLUSIONS

CDODA-Me has antineoplastic activity in bladder cancer cells by inducing ROS, which down-regulate Sp and Sp-regulated proteins. Thus, CDODA-Me has therapeutic potential in bladder cancer, and additional studies of the agent's efficacy and mode of action are warranted.

Induction of miR-137 by Isorhapontigenin (ISO) Directly Targets Sp1 Protein Translation and Mediates Its Anticancer Activity Both In Vitro and In Vivo

Our recent studies found that isorhapontigenin (ISO) showed a significant inhibitory effect on human bladder cancer cell growth, accompanied with cell-cycle G0-G1 arrest as well as downregulation of Cyclin D1 expression at transcriptional level via inhibition of Sp1 transactivation in bladder cancer cells. In the current study, the potential ISO inhibition of bladder tumor formation has been explored in a xenograft nude mouse model, and the molecular mechanisms underlying ISO inhibition of Sp1 expression and anticancer activities have been elucidated both in vitro and in vivo. Moreover, the studies demonstrated that ISO treatment induced the expression of miR-137, which in turn suppressed Sp1 protein translation by directly targeting Sp1 mRNA 3'-untranslated region (UTR). Similar to ISO treatment, ectopic expression of miR-137 alone led to G0-G1 cell growth arrest and inhibition of anchorage-independent growth in human bladder cancer cells, which could be completely reversed by overexpression of GFP-Sp1. The inhibition of miR-137 expression attenuated ISO-induced inhibition of Sp1/Cyclin D1 expression, induction of G0-G1 cell growth arrest, and suppression of cell anchorage-independent growth. Taken together, our studies have demonstrated that miR-137 induction by ISO targets Sp1 mRNA 3'-UTR and inhibits Sp1 protein translation, which consequently results in reduction of Cyclin D1 expression, induction of G0-G1 growth arrest, and inhibition of anchorage-independent growth in vitro and in vivo. Our results have provided novel insights into understanding the anticancer activity of ISO in the therapy of human bladder cancer.

Sp1 transcription factor: A long-standing target in cancer chemotherapy

Sp1 (specificity protein 1) is a well-known member of a family of transcription factors that also includes Sp2, Sp3 and Sp4, which are implicated in an ample variety of essential biological processes and have been proven important in cell growth, differentiation, apoptosis and carcinogenesis. Sp1 activates the transcription of many cellular genes that contain putative CG-rich Sp-binding sites in their promoters. Sp1 and Sp3 proteins bind to similar, if not the same, DNA tracts and compete for binding, thus they can enhance or repress gene expression. Evidences exist that the Sp-family of proteins regulates the expression of genes that play pivotal roles in cell proliferation and metastasis of various tumors. In patients with a variety of cancers, high levels of Sp1 protein are considered a negative prognostic factor. A plethora of compounds can interfere with the trans-activating activities of Sp1 and other Sp proteins on gene expression. Several pathways are involved in the down-regulation of Sp proteins by compounds with different mechanisms of action, which include not only the direct interference with the binding of Sp proteins to their putative DNA binding sites, but also promoting the degradation of Sp protein factors. Down-regulation of Sp transcription factors and Sp1-regulated genes is drug-dependent and it is determined by the cell context. The acknowledgment that several of those compounds are safe enough might accelerate their introduction into clinical usage in patients with tumors that over-express Sp1.

Histone Deacetylase Inhibitors Inhibit Rhabdomyosarcoma by Reactive Oxygen Species-Dependent Targeting of Specificity Protein Transcription Factors

The two major types of rhabdomyosarcoma (RMS) are predominantly diagnosed in children, namely embryonal (ERMS) and alveolar (ARMS) RMS, and patients are treated with cytotoxic drugs, which results in multiple toxic side effects later in life. Therefore, development of innovative chemotherapeutic strategies is imperative, and a recent genomic analysis suggested the potential efficacy of reactive oxygen species (ROS)-inducing agents. Here, we demonstrate the efficacy of the potent histone deacetylase (HDAC) inhibitors, panobinostat and vorinostat, as agents that inhibit RMS tumor growth in vivo, induce apoptosis, and inhibit invasion of RD and Rh30 RMS cell lines. These effects are due to epigenetic repression of cMyc, which leads to decreased expression of cMyc-regulated miRs-17, -20a, and -27a; upregulation of ZBTB4, ZBTB10, and ZBTB34; and subsequent downregulation of Sp transcription factors. We also show that inhibition of RMS cell growth, survival and invasion, and repression of Sp transcription factors by the HDAC inhibitors are independent of histone acetylation but reversible after cotreatment with the antioxidant glutathione. These results show a novel ROS-dependent mechanism of antineoplastic activity for panobinostat and vorinostat that lies outside of their canonical HDAC-inhibitory activity and demonstrates the potential clinical utility for treating RMS patients with ROS-inducing agents.

MicroRNA-Specificity Protein (Sp) Transcription Factor Interactions and Significance in Carcinogenesis

Specificity protein (Sp) transcription factors (TFs) such as Sp1, Sp3 and Sp4 are overexpressed in tumors and Sp1 is a negative prognostic factor for multiple tumor types. Sp TFs regulate expression of pro-oncogenic factors important for cell proliferation, survival, angiogenesis, migration/invasion and inflammation and the high expression of Sp TFs in tumors is primarily due to miRNAs. For example, expression of tumor-suppressor-like miRNAs such as miR-200b/c, miR-335, miR-22, miR-149 and others that inactivate Sp1 expression is low in many tumor types. Research in our laboratory has also demonstrated that high expression of Sp TFs is also due to miRNA-dependent inhibition of the transcriptional repressors ZBTB10 and ZBTB4 by miR-27a and miR-20a/miR-17p, respectively. Thus, miRNAs play a critical role in maintaining high levels of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes in tumors and cancer cells, and there is ample evidence that anticancer agents targeting the miRNASp TF axis can be highly effective for cancer chemotherapy.

Multicenter study on adult growth hormone level in postoperative pituitary tumor patients

The objective of this study is to observe the adult growth hormone level in postoperative pituitary tumor patients of multi-centers, and explore the change of hypophyseal hormones in postoperative pituitary tumor patients. Sixty patients with pituitary tumor admitted during March, 2011-March, 2012 were selected. Postoperative hypophyseal hormone deficiency and the change of preoperative, intraoperative, and postoperative growth hormone levels were recorded. Growth hormone hypofunction was the most common hormonal hypofunction, which took up to 85.0 %. Adrenocortical hormone hypofunction was next to it and accounted for 58.33 %. GH + ACTH + TSH + Gn deficiency was the most common in postoperative hormone deficiency, which took up to 40.00 %, and GH + ACTH + TSH + Gn + AVP and GH deficiencies were next to it and accounted for 23.33 and 16.67 %, respectively. The hormone levels in patients after total pituitary tumor resection were significantly lower than those after partial pituitary tumor resection, and the difference was statistically significant; growth hormone and serum prolactin levels after surgery in two groups were decreased, and the difference was statistically significant. The incidence rate of growth hormone deficiency in postoperative pituitary tumor patients is high, which is usually complicated with deficiency of various hypophyseal hormones. In clinical, we should pay attention to the levels of the hypopnyseal hormones, and take timely measures to avoid postoperative complications.

Diindolylmethane analogs bind NR4A1 and are NR4A1 antagonists in colon cancer cells

1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methane (C-DIM) compounds exhibit antineoplastic activity in multiple cancer cell lines and the p-hydroxyphenyl analog (DIM-C-pPhOH) inactivates nuclear receptor 4A1 (NR4A1) in lung and pancreatic cancer cell lines. Using a series of 14 different p-substituted phenyl C-DIMs, we show that several compounds including DIM-C-pPhOH directly interacted with the ligand binding domain of NR4A1. Computational-based molecular modeling studies showed high-affinity interactions of DIM-C-pPhOH and related compounds within the ligand binding pocket of NR4A1, and these same compounds decreased NR4A1-dependent transactivation in colon cancer cells transfected with a construct containing 3 tandem Nur77 binding response elements linked to a luciferase reporter gene. Moreover, we also show that knockdown of NR4A1 by RNA interference (small interfering NR4A1) or treatment with DIM-C-pPhOH and related compounds decreased colon cancer cell growth, induced apoptosis, decreased expression of survivin and other Sp-regulated genes, and inhibited mammalian target of rapamycin signaling. Thus, C-DIMs such as DIM-C-pPhOH directly bind NR4A1 and are NR4A1 antagonists in colon cancer cells, and their antineoplastic activity is due, in part, to their interactions with nuclear NR4A1.

Transcription factor Sp1, also known as specificity protein 1 as a therapeutic target

INTRODUCTION

Specificity protein (Sp) transcription factors (TFs) are members of the Sp/Kruppel-like factor family, and Sp proteins play an important role in embryonic and early postnatal development. Sp1 has been the most extensively investigated member of this family, and expression of this protein decreases with age, whereas Sp1 and other family members (Sp3 and Sp4) are highly expressed in tumors and cancer cell lines.

AREA COVERED

The prognostic significance of Sp1 in cancer patients and the functional pro-oncogenic activities of Sp1, Sp3 and Sp4 in cancer cell lines are summarized. Several different approaches have been used to target downregulation of Sp TFs and Sp-regulated genes, and this includes identification of different structural classes of antineoplastic agents including NSAIDs, natural products and their synthetic analogs and several well-characterized drugs including arsenic trioxide, aspirin and metformin. The multiple pathways involved in drug-induced Sp downregulation are also discussed.

EXPERT OPINION

The recognition by the scientific and clinical community that experimental and clinically used antineoplastic agents downregulate Sp1, Sp3 and Sp4, and pro-oncogenic Sp-regulated genes will facilitate future clinical applications for individual drug and drug combination therapies that take advantage of their unusual effects.

Sp1 transcriptionally regulates BRK1 expression in non-small cell lung cancer cells

Following a previous study reporting that BRK1 is upregulated in non-small cell lung cancer (NSCLC), the present study sought to clarify the role of specificity protein 1 (Sp1) in the transcriptional regulation of the BRK1 gene. Therefore, a construct, named F8, consisting of the -1341 to -1 nt sequence upstream of the start codon of the BRK1 gene inserted into pGL4.26 was made. A series of truncated fragments was then constructed based on F8. Segment S831, which contained the -84 to -1 nt region, displayed the highest transcriptional activity in the A549, H1299 and H520 NSCLC cell lines. Bioinformatic analysis showed a potential Sp1-binding element at -73 to -64 nt, and a mutation in this region suppressed the transcriptional activity of S831. Then the RNAi assays of Sp1 and its coworkers Sp3 and Sp4 were performed, and suppression of Sp1 by siRNA inhibited the mRNA expression of BRK1. Both an electrophoretic mobility shift assay (EMSA) and a chromatin immunoprecipitation (ChIP) assay demonstrated that Sp1 bound to the promoter area of the BRK1 gene. Our data identified a functional and positive Sp1 regulatory element from -73 to -64 nt in the BRK1 promoter, which may likely explain the overexpression of BRK1 in NSCLC.

The cannabinoid WIN 55,212-2 decreases specificity protein transcription factors and the oncogenic cap protein eIF4E in colon cancer cells

2,3-Dihydro-5-methyl-3-([morpholinyl]methyl)pyrollo(1,2,3-de)-1,4-benzoxazinyl]-[1-naphthaleny]methanone [WIN 55,212-2, (WIN)] is a synthetic cannabinoid that inhibits RKO, HT-29, and SW480 cell growth, induced apoptosis, and downregulated expression of survivin, cyclin D1, EGF receptor (EGFR), VEGF, and its receptor (VEGFR1). WIN also decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, and this is consistent with the observed downregulation of the aforementioned Sp-regulated genes. In addition, we also observed by RNA interference (RNAi) that the oncogenic cap protein eIF4E was an Sp-regulated gene also downregulated by WIN in colon cancer cells. WIN-mediated repression of Sp proteins was not affected by cannabinoid receptor antagonists or by knockdown of the receptor but was attenuated by the phosphatase inhibitor sodium orthovanadate or by knockdown of protein phosphatase 2A (PP2A). WIN-mediated repression of Sp1, Sp3, and Sp4 was due to PP2A-dependent downregulation of microRNA-27a (miR-27a) and induction of miR-27a-regulated ZBTB10, which has previously been characterized as an "Sp repressor." The results show that the anticancer activity of WIN is due, in part, to PP2A-dependent disruption of miR-27a:ZBTB10 and ZBTB10-mediated repression of Sp transcription factors and Sp-regulated genes, including eIF4E.

Tolfenamic acid inhibits colon cancer cell and tumor growth and induces degradation of specificity protein (Sp) transcription factors

Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug (NSAID) that inhibits lung, esophageal, breast and pancreatic cancer cell and tumor growth, and this study investigated the anticancer activity of TA in colon cancer. TA inhibited growth and induced apoptosis in RKO, SW480, HT-29, and HCT-116 colon cancer cells, and TA (50 mg/kg/d) also inhibited tumor growth in athymic nude mice bearing RKO cells as xenografts. TA downregulated expression of Sp proteins (Sp1, Sp3, and Sp4) in colon cancer cells and this was accompanied by decreased expression of several Sp-regulated growth promoting (cyclin D1, hepatocyte growth factor receptor), angiogenic (vascular endothelial growth factor (VEGF) and its receptor 1), survival (survivin and bcl-2), and inflammatory (NFκBp65/p50) gene products. The mechanism of TA-mediated effects on Sp proteins was due to activation of caspases. These results now extend the number of NSAIDs that may have clinical potential for colon cancer chemotherapy and show that the anticancer activity of TA is due, in part, to targeting Sp transcription factors.

Telomerase reverse transcriptase (TERT) is a therapeutic target of oleanane triterpenoid CDDO-Me in prostate cancer

Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is an synthetic oleanane triterpenoid with strong antiprolifertive and proapoptotic activities in cancer cells. However, the effect of CDDO-Me on human telomerase reverse transcriptase (hTERT) and its telomerase activity in prostate cancer cells has not been studied. We investigated the role of hTERT in mediating the anticancer activity of CDDO-Me in prostate cancer cells in vitro and in vivo. The inhibition of cell proliferation and induction of apoptosis by CDDO-Me in LNCaP and PC-3 prostate cancer cell lines was associated with the inhibition of hTERT gene expression, hTERT telomerase activity and a number of proteins that regulate hTERT transcriptionally and post-translationally. Furthermore, ablation of hTERT protein increased the sensitivity of cancer cells to CDDO-Me, whereas its overexpression rendered them resistant to CDDO-Me. In addition, inhibition of progression of preneoplastic lesions (i.e., low and high-grade prostate intraepithelial neoplasms, PINs) to adenocarcinoma of the prostate by CDDO-Me in TRAMP mice was associated with significant decrease in TERT and its regulatory proteins in the prostate gland. These data provide evidence that telomerase is a potential target of CDDO-Me for the prevention and treatment of prostate cancer.

Curcumin and synthetic analogs induce reactive oxygen species and decreases specificity protein (Sp) transcription factors by targeting microRNAs

Background

Curcumin inhibits growth of several cancer cell lines, and studies in this laboratory in bladder and pancreatic cancer cells show that curcumin downregulates specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and pro-oncogenic Sp-regulated genes. In this study, we investigated the anticancer activity of curcumin and several synthetic cyclohexanone and piperidine analogs in colon cancer cells.

Methods

The effects of curcumin and synthetic analogs on colon cancer cell proliferation and apoptosis were determined using standardized assays. The changes in Sp proteins and Sp-regulated gene products were analysed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a), miR-20a, miR-17-5p and ZBTB10 and ZBTB4 mRNA expression.

Results

The IC₅₀ (half-maximal) values for growth inhibition (24 hr) of colon cancer cells by curcumin and synthetic cyclohexanone and piperidine analogs of curcumin varied from 10 μM for curcumin to 0.7 μM for the most active synthetic piperidine analog RL197, which was used along with curcumin as model agents in this study. Curcumin and RL197 inhibited RKO and SW480 colon cancer cell growth and induced apoptosis, and this was accompanied by downregulation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and Sp-regulated genes including the epidermal growth factor receptor (EGFR), hepatocyte growth factor receptor (c-MET), survivin, bcl-2, cyclin D1 and NFκB (p65 and p50). Curcumin and RL197 also induced reactive oxygen species (ROS), and cotreatment with the antioxidant glutathione significantly attenuated curcumin- and RL197-induced growth inhibition and downregulation of Sp1, Sp3, Sp4 and Sp-regulated genes. The mechanism of curcumin-/RL197-induced repression of Sp transcription factors was ROS-dependent and due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of microRNAs (miR)-27a, miR-20a and miR-17-5p that regulate these repressors.

Conclusions

These results identify a new and highly potent curcumin derivative and demonstrate that in cells where curcumin and RL197 induce ROS, an important underlying mechanism of action involves perturbation of miR-ZBTB10/ZBTB4, resulting in the induction of these repressors which downregulate Sp transcription factors and Sp-regulated genes.

Expression and the clinical significance of hPTTG1 in gastric cancer

The aim of this study was to investigate the expression and clinical significance of hPTTG1 in gastric cancer. Immunohistochemistry was performed to determine the expression of hPTTG1 in gastric cancer tissues. Results showed that the positive expression of hPTTG1 in gastric cancer tissues was 60.00%, while in adjacent normal tissues it was 17.78%. The expression of hPTTG1 was correlated with differentiation levels, clinical classification and lymph node metastasis, but did not correlate with gender, age or pathological types. hPTTG1 was, therefore, overexpressed in gastric cancer tissues. The progression of gastric cancer was found to be correlated with the upregulation of the expression of hPTTG1. hPTTG1 detection may be helpful in evaluating the ability of the clinical classification and lymph node metastasis in gastric cancer to predict outcomes. These factors act as indicators of the biological behavior of gastric cancer and are fairly good markers for prognosis and therapy.

Induction of the transcriptional repressor ZBTB4 in prostate cancer cells by drug-induced targeting of microRNA-17-92/106b-25 clusters

Androgen-insensitive DU145 and PC3 human prostate cancer cells express high levels of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, and treatment of cells with methyl 2-cyano-3,11-dioxo-18β-olean-1,12-dien-30-oate (CDODA-Me) inhibited cell growth and downregulated Sp1, Sp3, and Sp4 expression. CDODA-Me (15 mg/kg/d) was a potent inhibitor of tumor growth in a mouse xenograft model (PC3 cells) and also decreased expression of Sp transcription factors in tumors. CDODA-Me-mediated downregulation of Sp1, Sp3, and Sp4 was due to induction of the transcriptional repressor ZBTB4, which competitively binds and displaces Sp transcription factors from GC-rich sites in Sp1-, Sp3-, Sp4-, and Sp-regulated gene promoters. ZBTB4 levels are relatively low in DU145 and PC3 cells due to suppression by miR paralogs that are members of the miR-17-92 (miR-20a/17-5p) and miR-106b-25 (miR-106b/93) clusters. Examination of publically available prostate cancer patient array data showed an inverse relationship between ZBTB4 and miRs-20a/17-5p/106b/93 expression, and increased ZBTB4 in patients with prostate cancer was a prognostic factor for increased survival. CDODA-Me induces ZBTB4 in prostate cancer cells through disruption of miR-ZBTB4 interactions, and this results in downregulation of pro-oncogenic Sp transcription factors and Sp-regulated genes.

The pituitary tumor transforming gene in thyroid cancer

The pituitary tumor transforming gene (PTTG) is a multifunctional proto-oncogene that is over-expressed in various tumors including thyroid carcinomas, where it is a prognostic indicator of tumor recurrence. PTTG has potent transforming capabilities in vitro and in vivo, and many studies have investigated the potential mechanisms by which PTTG contributes to tumorigenesis. As the human securin, PTTG is involved in critical mechanisms of cell cycle regulation, whereby aberrant expression induces aneuploidy. PTTG may further contribute to tumorigenesis through its role in DNA damage response pathways and via complex interactions with hormones and growth factors. Furthermore, PTTG over-expression negatively impacts upon the efficacy of radioiodine therapy in thyroid cancer, through repression of expression and function of the sodium iodide symporter. Given its various roles at all disease stages, PTTG appears to be an important oncogene in thyroid cancer. This review discusses the current knowledge of PTTG with particular focus on its role in thyroid cancer.

Betulinic acid inhibits colon cancer cell and tumor growth and induces proteasome-dependent and -independent downregulation of specificity proteins (Sp) transcription factors

Background

Betulinic acid (BA) inhibits growth of several cancer cell lines and tumors and the effects of BA have been attributed to its mitochondriotoxicity and inhibition of multiple pro-oncogenic factors. Previous studies show that BA induces proteasome-dependent degradation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 in prostate cancer cells and this study focused on the mechanism of action of BA in colon cancer cells.

Methods

The effects of BA on colon cancer cell proliferation and apoptosis and tumor growth in vivo were determined using standardized assays. The effects of BA on Sp proteins and Sp-regulated gene products were analyzed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a) and ZBTB10 mRNA expression.

Results

BA inhibited growth and induced apoptosis in RKO and SW480 colon cancer cells and inhibited tumor growth in athymic nude mice bearing RKO cells as xenograft. BA also decreased expression of Sp1, Sp3 and Sp4 transcription factors which are overexpressed in colon cancer cells and decreased levels of several Sp-regulated genes including survivin, vascular endothelial growth factor, p65 sub-unit of NFκB, epidermal growth factor receptor, cyclin D1, and pituitary tumor transforming gene-1. The mechanism of action of BA was dependent on cell context, since BA induced proteasome-dependent and proteasome-independent downregulation of Sp1, Sp3 and Sp4 in SW480 and RKO cells, respectively. In RKO cells, the mechanism of BA-induced repression of Sp1, Sp3 and Sp4 was due to induction of reactive oxygen species (ROS), ROS-mediated repression of microRNA-27a, and induction of the Sp repressor gene ZBTB10.

Conclusions

These results suggest that the anticancer activity of BA in colon cancer cells is due, in part, to downregulation of Sp1, Sp3 and Sp4 transcription factors; however, the mechanism of this response is cell context-dependent.