Tolfenamic acid inhibits esophageal cancer through repression of specificity proteins and c-Met

Fenamates: Forgotten treasure for cancer treatment and prevention: Mechanisms of action, structural modification, and bright future

Fenamates as classical nonsteroidal anti-inflammatory agents are widely used for relieving pain. Preclinical studies and epidemiological data highlight their chemo-preventive and chemotherapeutic potential for cancer. However, comprehensive reviews of fenamates in cancer are limited. To accelerate the repurposing of fenamates, this review summarizes the results of fenamates alone or in combination with existing chemotherapeutic agents. This paper also explores targets of fenamates in cancer therapy, including COX, AKR family, AR, gap junction, FTO, TEAD, DHODH, TAS2R14, ion channels, and DNA. Besides, this paper discusses other mechanisms, such as regulating Wnt/β-catenin, TGF-β, p38 MAPK, and NF-κB pathway, and the regulation of the expressions of Sp, EGR-1, NAG-1, ATF-3, ErbB2, AR, as well as the modulation of the tumor immune microenvironment. Furthermore, this paper outlined the structural modifications of fenamates, highlighting their potential as promising leads for anticancer drugs.

NOS2 and COX-2 Co-Expression Promotes Cancer Progression: A Potential Target for Developing Agents to Prevent or Treat Highly Aggressive Breast Cancer

Nitric oxide (NO) and reactive nitrogen species (RNS) exert profound biological impacts dictated by their chemistry. Understanding their spatial distribution is essential for deciphering their roles in diverse biological processes. This review establishes a framework for the chemical biology of NO and RNS, exploring their dynamic reactions within the context of cancer. Concentration-dependent signaling reveals distinctive processes in cancer, with three levels of NO influencing oncogenic properties. In this context, NO plays a crucial role in cancer cell proliferation, metastasis, chemotherapy resistance, and immune suppression. Increased NOS2 expression correlates with poor survival across different tumors, including breast cancer. Additionally, NOS2 can crosstalk with the proinflammatory enzyme cyclooxygenase-2 (COX-2) to promote cancer progression. NOS2 and COX-2 co-expression establishes a positive feed-forward loop, driving immunosuppression and metastasis in estrogen receptor-negative (ER-) breast cancer. Spatial evaluation of NOS2 and COX-2 reveals orthogonal expression, suggesting the unique roles of these niches in the tumor microenvironment (TME). NOS2 and COX2 niche formation requires IFN-γ and cytokine-releasing cells. These niches contribute to poor clinical outcomes, emphasizing their role in cancer progression. Strategies to target these markers include direct inhibition, involving pan-inhibitors and selective inhibitors, as well as indirect approaches targeting their induction or downstream effectors. Compounds from cruciferous vegetables are potential candidates for NOS2 and COX-2 inhibition offering therapeutic applications. Thus, understanding the chemical biology of NO and RNS, their spatial distribution, and their implications in cancer progression provides valuable insights for developing targeted therapies and preventive strategies.

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.

Tolfenamic acid negatively regulates YAP and TAZ expression in human cancer cells

Several diseases are associated with improper regulation of the Hippo pathway, which plays an important role in cell proliferation and cancer metastasis. Overactivation of the YAP and TAZ proteins accelerates cell proliferation, invasion, and migration during tumorigenesis. Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug (NSAID) that exhibits activity against various types of cancer. In this study, we observed that TA decreased YAP and TAZ protein levels in cancer cells. TA increased the phosphorylation of YAP and TAZ, leading to the degradation of YAP and TAZ in the cytoplasm and nucleus. TA predominantly affected multiple phosphodegron sites in the YAP and TAZ and lowered 14-3-3β protein expression, causing YAP and TAZ to enter the ubiquitination pathway. Proteins that affect YAP and TAZ regulation, such as NAG-1 and several YAP/TAZ E3 ligases, were not involved in TA-mediated YAP/TAZ degradation. In summary, our results indicate that TA affects phosphodegron sites on YAP/TAZ, demonstrating a novel effect of TA in tumorigenesis.

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.

Transcriptional activation of CSTB gene expression by transcription factor Sp3

CSTB has been reported to be associated with the pathogenesis of many malignant tumors, especially hepatocellular carcinoma (HCC). However, how the expression of this gene is regulated is largely unknown. We initially cloned and analyzed the promoter region of the CSTB gene by luciferase assay and the Sp3 binding site (CCCCGCCCCGCG) was found in it. The results of electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) experiments verified that the transcription factor, Sp3 could bind to the " CCCCGCCCCGCG ″ site of the CSTB gene promoter. We showed that the overexpression of Sp3 significantly increased the endogenous mRNA and protein expression levels of CSTB, whereas knockdown of Sp3 decreased the mRNA and protein expression levels according to quantitative real-time PCR (qRT‒PCR) and western blotting. In conclusion, CSTB gene expression is closely regulated by transcription factor Sp3, which may be a potential mechanism for the dysregulation of CSTB expression in HCC.

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.

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.

Next generation sequencing and functional pathway analysis to understand the mechanism of action of copper-tolfenamic acid against pancreatic cancer cells

Anti-cancer activity of tolfenamic acid (TA) in preclinical models for pancreatic cancer (PaCa) is well established. Since the dosage for anti-cancer actions of TA is rather high, we recently demonstrated that IC₅₀ values of Copper-TA are 30-80% less than TA in 12 cancer cell lines. This study elucidates the underlying mechanisms of Copper-TA in PaCa cells. Control and Copper-TA (IC₅₀) treated PaCa cells were processed by next-generation sequencing (NGS) to determine differentially expressed genes using HTG EdgeSeq Oncology Biomarker panel. Ingenuity Pathway Analysis (IPA®) was used to identify functional significance of altered genes. The conformational studies for assessing the expression of key regulators and genes were conducted by Western blot and qPCR. IPA® identified several networks, regulators, as well as molecular and cellular functions associated with cancer. The top 5 molecular and cellular functions affected by Cu-TA treatment were cell death and survival, cellular development, cell growth and proliferation, cell cycle and cellular movement. The expression of top upstream regulators was confirmed by Western blot analysis while qPCR results of selected genes demonstrated that Copper-TA is efficacious at lower doses than TA. Results suggest that Copper-TA alters genes/key regulators associated with cancer and potentially serve as an effective anti-cancer agent.

PI3K-targeting strategy using alpelisib to enhance the antitumor effect of paclitaxel in human gastric cancer

PIK3CA mutations are frequently observed in various human cancers including gastric cancer (GC). This study was conducted to investigate the anti-tumor effects of alpelisib, a PI3K p110α-specific inhibitor, using preclinical models of GC. In addition, the combined effects of alpelisib and paclitaxel on GC were evaluated. Among the SNU1, SNU16, SNU484, SNU601, SNU638, SNU668, AGS, and MKN1 GC cells, three PIK3CA-mutant cells were predominantly sensitive to alpelisib. Alpelisib monotherapy decreased AKT and S6K1 phosphorylation and induced G₀/G₁ phase arrest regardless of PIK3CA mutational status. The alpelisib and paclitaxel combination demonstrated synergistic anti-proliferative effects, preferentially on PIK3CA-mutant cells, resulting in increased DNA damage response and apoptosis. In addition, alpelisib and paclitaxel combination potentiated anti-migratory activity in PIK3CA-mutant cells. Alpelisib partially reversed epithelial–mesenchymal transition markers in PIK3CA-mutant cells. In a xenograft model of MKN1 cells, the alpelisib and paclitaxel combination significantly enhanced anti-tumor activity by decreasing Ki-67 expression and increasing apoptosis. Moreover, this combination tended to prolong the survival of tumor-bearing mice. Our data suggest promising anti-tumor efficacy of alpelisib alone or in combination with paclitaxel in PIK3CA-mutant GC cells.

Synergistic effect of tolfenamic acid and glycyrrhizic acid on TPA-induced skin inflammation in mice

Tolfenamic acid (TA) and glycyrrhizic acid (GA) are well-known components with anti-inflammatory properties. However, their combined effects on inflammation have not been well studied. The present study aimed to investigate the in vivo anti-inflammatory effects of TA combined with GA using a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema model, as well as the underlying mechanisms thereof. The results indicated that TA combined with GA led to a stronger inhibition on TPA-induced mouse ear edema compared to the singular treatments. In addition, the combined treatment significantly alleviated subcutaneous tissue inflammation caused by TPA. Further mechanistic investigations demonstrated that TA combined with GA decreased the levels of TPA-induced interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Furthermore, the combined treatment effectively inhibited nuclear factor-κB (NF-κB), extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK), phosphor-ERK1/2 and phosphor-JNK, which was accompanied by blocking of the activation and the phosphorylation in mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways. Collectively, our findings revealed that different anti-inflammatory components used in combination lead to enhanced inhibitory effects against inflammation.

Effect of Selected Nonsteroidal Anti-inflammatory Drugs on the Viability of Canine Osteosarcoma Cells of the D-17 Line: In Vitro Studies

Introduction

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in veterinary medicine. They are used in pain control and in anti-inflammatory and antipyretic therapies. Some NSAIDs, e.g piroxicam, also have a documented anticancer effect. The objective of this study was to evaluate which of the commonly used NSAIDs (etodolac, flunixin, tolfenamic acid, carprofen, and ketoprofen) are cytotoxic to the D-17 cell line of canine osteosarcoma.

Material and Methods

The viability of the cells was evaluated using the MTT assay. Four independent repetitions were performed and the results are given as the average of these values; EC₅₀ values (half maximal effective concentration) were also calculated.

Results

The analysis of results showed that carprofen and tolfenamic acid displayed the highest cytotoxicity. Other drugs either did not provide such effects or they were very poor. For carprofen, it was possible to determine an EC₅₀ which fell within the limits of concentrations obtainable in canine serum after the administration of routinely used doses.

Conclusion

The results are promising but further studies should be conducted to confirm them, since this study is only preliminary. The possibility of introducing carprofen and tolfenamic acid into the routine treatment of osteosarcoma in dogs should be considered.

Inhibitor of growth 4 affects hypoxia-induced migration and angiogenesis regulation in retinal pigment epithelial cells

Inhibitor of growth 4 (ING4), a potential tumor suppressor, is implicated in cell migration and angiogenesis. However, its effects on diabetic retinopathy (DR) have not been elucidated. In this study, we aimed to evaluate ING4 expression in normal and diabetic rats and clarify its effects on hypoxia-induced dysfunction in human retinal pigment epithelial (ARPE-19) cells. A Type 1 diabetic model was generated by injecting rats intraperitoneally with streptozotocin and then killed them 4, 8, or 12 weeks later. ING4 expression in retinal tissue was detected using western blot analysis, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), and immunohistochemistry assays. After transfection with an ING4 overexpression lentiviral vector or small interfering RNA (siRNA), ARPE-19 migration under hypoxia was tested using wound healing and transwell assays. The angiogenic effect of conditioned medium (CM) from ARPE-19 cells was examined by assessing human retinal endothelial cell (HREC) capillary tube formation. Additionally, western blot analysis and RT-qPCR were performed to investigate the signaling pathways in which ING4, specificity protein 1 (Sp1), matrix metalloproteinase 2 (MMP-2), MMP-9, and vascular endothelial growth factor A (VEGF-A) were involved. Here, we found that ING4 expression was significantly reduced in the diabetic rats' retinal tissue. Silencing ING4 aggravated hypoxia-induced ARPE-19 cell migration. CM collected from ING4 siRNA-transfected ARPE-19 cells under hypoxia promoted HREC angiogenesis. These effects were reversed by ING4 overexpression. Furthermore, ING4 suppressed MMP-2, MMP-9, and VEGF-A expression in an Sp1-dependent manner in hypoxia-conditioned ARPE-19 cells. Overall, our results provide valuable mechanistic insights into the protective effects of ING4 on hypoxia-induced migration and angiogenesis regulation in ARPE-19 cells. Restoring ING4 may be a novel strategy for treating DR.

The involvement of lipid raft pathway in suppression of TGFβ-mediated metastasis by tolfenamic acid in hepatocellular carcinoma cells

TGFβ signaling plays an important role in orchestrating a favorable microenvironment for tumor cell growth and promoting epithelial-mesenchymal transition. As a conventional nonsteroidal anti-inflammation drugs, tolfenamic acid (TA) has been previously reported to exhibit anti-cancer activity. Herein, we investigated the effect of TA on TGFβ-mediated pro-metastatic activity and the underlying mechanisms in hepatocellular carcinoma (HCC). As a result, TA suppresses TGFβ-induced migration and glycolysis in HCC cells, which is accompanied with reduced Smad phosphorylation and subsequent nuclear transcription activity. Mechanistically, TA promotes lipid raft-caveolar internalization pathway of TGFβ receptor, therefore leading to its rapid turnover. Consistently, TA inhibits constitutively active TGFβ type I receptor induced Smad phosphorylation and EMT markers, whereas ectopic expression of TGFβ type II receptor could partially rescue TGFβ-mediated Smad2 phosphorylation and downstream genes expression in the presence of TA. Furthermore, TA inhibited HCC cells invasion in nude mice, associated with the alteration of characteristics related with EMT and glycolysis of cancer cells. Our study suggests TA could activate lipid raft pathway and modulate TGFβ mediated metastasis, implicating the potential application of TA as a modulator of tumor microenvironment in HCC.

Tolfenamic Acid

Tolfenamic acid (TA) is a nonsteroidal antiinflammatory drug and belongs to the group of fenamates. It is used as a potent pain reliever in the treatment of acute migraine attacks, and disorders like dysmenorrhea, rheumatoid, and osteoarthritis. TA has shown excellent in vitro antibacterial activity against certain ATCC strains of bacteria when complexed with bismuth(III). It has also been reported to block pathological processes associated with Alzheimer's disease. In the recent past, TA has also been used as a novel anticancer agent for the treatment of various cancers. In view of the clinical importance of TA, a comprehensive review of the physical and pharmaceutical properties and details of the various analytical methods used for the assay of the drug in pharmaceutical and biological systems has been made. The methods reviewed include identification tests and titrimetric, spectrophotometric, chromatographic, electrochemical, thermal, microscopic, enzymatic, and solid-state techniques. Along with the analytical profile, the stability and degradation of TA, its pharmacology and pharmacokinetics, dosage forms and dose, adverse effects and toxicity, and interactions have been discussed.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Targeting specificity protein 1 transcription factor and survivin using tolfenamic acid for inhibiting Ewing sarcoma cell growth

Transcription factor Specificity protein 1 (Sp1) and its downstream target survivin (inhibitor of apoptosis protein), play major roles in the pathogenesis of various cancers. Ewing Sarcoma (ES) is a common soft tissue/bone tumor in adolescent and young adults. Overexpression of survivin is also linked to the aggressiveness and poor prognosis of ES. Small molecule Tolfenamic acid (TA) inhibits Sp1 and survivin in cancer cells. In this investigation, we demonstrate a strategy to target Sp1 and survivin using TA and positive control Mithramycin A (Mit) to inhibit ES cell growth. Knock down of Sp1 using small interfering RNA (siRNA) resulted in significant (p < 0.05) inhibition of CHLA-9 and TC-32 cell growth as assessed by CellTiter-Glo assay kit. TA or Mit treatment caused dose/time-dependent inhibition of cell viability, and this inhibition was correlated with a decrease in Sp1 and survivin protein levels in ES cells. Quantitative PCR results showed that Mit treatment decreased the mRNA expression of both survivin and Sp1, whereas TA diminished only survivin but not Sp1. Proteasome inhibitor restored TA-induced inhibition of Sp1 protein expression suggesting that TA might cause proteasome-dependent degradation. Gel shift assay using ES cell nuclear extract and biotinylated Sp1 consensus oligonucleotides confirmed that both TA and Mit decreased DNA-binding activity of Sp1. These results demonstrate that both Mit and TA reduce expression of Sp1 and survivin, disrupt Sp1 DNA-binding and inhibit ES cell proliferation. This investigation suggests that targeting Sp1 and survivin could be an effective strategy for inhibiting ES cell growth.

Betulinic acid and the pharmacological effects of tumor suppression (Review)

Betulinic acid (BA), a lupane-type pentacyclic triterpenoid saponin from tree bark, has the potential to induce the apoptosis of cancer cells without toxicity towards normal cells in vitro and in vivo. The antitumor pharmacological effects of BA consist of triggering apoptosis via the mitochondrial pathway, regulating the cell cycle and the angiogenic pathway via factors, including specificity protein transcription factors, cyclin D1 and epidermal growth factor receptor, inhibiting the signal transducer and activator of transcription 3 and nuclear factor‑κB signaling pathways, preventing the invasion and metastasis of tumor cells, and affecting the expression of topoisomerase I, p53 and lamin B1. In previous years, several studies have shown its antitumor effect, initially applied to malignant melanoma, however, it also has broad efficacies against most solid types of tumor from different regions of the body. There have been few investigations in hematological malignancies, however, this direction may offer potential in such a novel field of research. In this review, the primary pharmacological effects of BA in tumors, particularly in hematological malignancies are discussed.

In silico dissection of miRNA targetome polymorphisms and their role in regulating miRNA-mediated gene expression in esophageal cancer

Esophageal cancer is the eighth most common cancer worldwide. Also middle-aged obese adults with higher body mass index during childhood have a greater risk to develop esophageal cancer. The contribution of microRNAs to esophageal cancer has been extensively studied and it became clear that these noncoding RNAs may play crucial roles in pathogenesis, diagnosis and prognosis of the disease. Increasing evidences have suggested that polymorphisms perturbing microRNA targetome (i.e., the compendium of all microRNA target sites) are associated with cancers including esophageal cancer. However, the extent to which such variants contribute to esophageal cancer is still unclear. In this study, we applied an in silico approach to systematically identify polymorphisms perturbing microRNA targetome in esophageal cancer and performed various analyses to predict the functional consequences of the occurrence of these variants. The computational results were integrated to provide a prioritized list of the most potentially disrupting esophageal cancer-implicated microRNA targetome polymorphisms along with the in silico insight into the mechanisms with which such variations may modulate microRNA-mediated regulation. The results of this study will be valuable for future functional experiments aimed at dissecting the roles of microRNA targetome polymorphisms in the onset and progression of esophageal cancer.

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.

Combination of 13 cis-retinoic acid and tolfenamic acid induces apoptosis and effectively inhibits high-risk neuroblastoma cell proliferation

Chemotherapeutic regimens used for the treatment of Neuroblastoma (NB) cause long-term side effects in pediatric patients. NB arises in immature sympathetic nerve cells and primarily affects infants and children. A high rate of relapse in high-risk neuroblastoma (HRNB) necessitates the development of alternative strategies for effective treatment. This study investigated the efficacy of a small molecule, tolfenamic acid (TA), for enhancing the anti-proliferative effect of 13 cis-retinoic acid (RA) in HRNB cell lines. LA1-55n and SH-SY5Y cells were treated with TA (30μM) or RA (20μM) or both (optimized doses, derived from dose curves) for 48h and tested the effect on cell viability, apoptosis and selected molecular markers (Sp1, survivin, AKT and ERK1/2). Cell viability and caspase activity were measured using the CellTiter-Glo and Caspase-Glo kits. The apoptotic cell population was determined by flow cytometry with Annexin-V staining. The expression of Sp1, survivin, AKT, ERK1/2 and c-PARP was evaluated by Western blots. The combination therapy of TA and RA resulted in significant inhibition of cell viability (p<0.0001) when compared to individual agents. The anti-proliferative effect is accompanied by a decrease in Sp1 and survivin expression and an increase in apoptotic markers, Annexin-V positive cells, caspase 3/7 activity and c-PARP levels. Notably, TA+RA combination also caused down regulation of AKT and ERK1/2 suggesting a distinct impact on survival and proliferation pathways via signaling cascades. This study demonstrates that the TA mediated inhibition of Sp1 in combination with RA provides a novel therapeutic strategy for the effective treatment of HRNB in children.

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.

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.

Role of Brg1 in progression of esophageal squamous cell carcinoma

OBJECTIVES

Epigenetic regulation of gene expression can be carried out through chromatin remodeling enzymes such as SWI/SNF. Brg1 also known as SMARCA4 is a catalytic subunit of SWI/SNF, which is necessary for MMPs expression. Matrix metalloproteinases (MMPs) are known as important player enzymes during tumor progression and metastasis. Aberrant epigenetic modification of chromatin should be precisely clarified to reveal probable unknown pathways in ESCC progression. Probable role of Brg1 in ESCC tumorigenesis and metastasis was studied through the assessment of Brg1 mRNA expression in KYSE30, and further evaluation about the biology of Brg1 was performed through the Brg1 silencing.

MATERIALS AND METHODS

Level of Brg1 mRNA expression in KYSE30 was compared to normal tissues using the real time polymerase chain reaction (PCR). Moreover, KYSE30 cells were transfected with Brg1-siRNA to silence the Brg1.

RESULTS

Our results showed for the first time that Brg1 mRNA expression was increased in KYSE30 cell line (ESCC cell line) compared with normal esophageal tissue of ESCC patients. Rate of transfection in KYSE30 was also between 40 to 50%, using the pSilencer-Brg1shRNA (1:1 ratio).

CONCLUSION

Our data indicated that chromatin remodeling machinery is a novel aspect in tumor biology of ESCC, and overexpression of Brg1 as an important member of SWI/SNF might be involved in the migration and invasion of ESCC tumoral cells.

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.

Alteration of gene expression profile in hepatocellular carcinoma HepG2 cells with Sp3 downregulation

AIM: To analyze the alteration of gene expression profile in hepatocellular carcinoma cell line HepG2 with Sp3 downregulation.

METHODS: RNA interference was performed to downregulate Sp3 mRNA in HepG2 cells and NimbleGen Human Gene Expression Microarray was used for gene expression profile analysis. Real-time quantitative PCR was employed to confirm the expression of several differentially expressed genes. The cell cycle was analyzed by flow cytometry.

RESULTS: A total of 1789 genes was found to be differentially expressed in HepG2 cells with Sp3 downregulation, including 1007 up-regulated and 782 down-regulated ones. These genes were involved in many cellular biological process such as proliferation, differentiation, programmed death, adhesion, and metabolic process. Real-time quantitative PCR confirmed the alteration of several cell cycle related genes (CCND1, CCNE2, TGFB1, and CDKN2A). Flow cytometry analysis showed that the percentage of cells in G₁ phase increased significantly after Sp3 downregulation.

CONCLUSION: Gene expression profile alters in HepG2 with Sp3 downregulation. Sp3 knockdown induces cell cycle arrest in G₀/G₁ phase in HepG2 cells. Sp3 may play an essential role in the pathogenesis of hepatocellular carcinoma as a transcription factor via regulating cell cycle progression.

RNAi-mediated silencing of Sp3 expression reduces invasion of HepG2 cells in a xenogeneic graft mouse model

AIM: To observe the influence of specificity protein 3 (Sp3) silencing on invasion of HepG2 cells in a xenogeneic graft mouse model, and to explore the possible mechanisms involved.

METHODS: A shRNA-Sp3 or non-relevant shRNA was transfected into HepG2 cells using a lentiviral vector. Non-transfected HepG2 cells were used as controls. The three groups of cells were injected into nude mice. Tumor formation rate was determined, and the pathological morphology of cells in three groups was observed. The mRNA and protein expression of Sp3, β-catenin, E-cadherin and matrix metallopeptidase 9 (MMP-9) was detected by real-time PCR and immunohistochemistry.

RESULTS: The tumor formation rate was lower in the shRNA-Sp3 group than in the non-relevant group and control group (60% vs 100%, 100%). The ability of invasion was weaker in the shRNA-Sp3 group. The expression of Sp3, β-catenin and MMP-9 mRNAs in the shRNA-Sp3 group was significantly lower than that in the non-relevant group and control group (F = 29.692, 21.894, 109.414; P = 0.001, 0.002, < 0.001). The expression of E-cadherin mRNA was significantly higher in the shRNA-Sp3 group than in the other two groups (F = 66.983, P < 0.001). The expression levels of Sp3 (30 ± 5.69), β-catenin (28 ± 5.13) and MMP-9 proteins (97 ± 10.41) were significantly lower than those in the non-relevant group and control group (P = 0.000 for all). The expression of E-cadherin protein (132 ± 4.36) was significantly higher in the shRNA-Sp3 group than in the other two groups (P = 0.000).

CONCLUSION: Sp3 may influence the invasion of HepG2 cells in vivo by up-regulating the expression of β-catenin and MMP-9 and down-regulating the expression of E-cadherin.

Anti-tumor effects of an oncolytic adenovirus expressing hemagglutinin-neuraminidase of Newcastle disease virus in vitro and in vivo

Oncolytic virotherapy has been an attractive drug platform for targeted therapy of cancer over the past few years. Viral vectors can be used to target and lyse cancer cells, but achieving good efficacy and specificity with this treatment approach is a major challenge. Here, we assessed the ability of a novel dual-specific anti-tumor oncolytic adenovirus, expressing the hemagglutinin-neuraminidase (HN) gene from the Newcastle disease virus under the human telomerase reverse transcriptase (hTERT) promoter (Ad-hTERTp-E1a-HN), to inhibit esophageal cancer EC-109 cells in culture and to reduce tumor burden in xenografted BALB/c nude mice. In vitro, infection with Ad-hTERT-E1a-HN could inhibit the growth of EC-109 cells significantly and also protect normal human liver cell line L02 from growth suppression in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Ad-hTERT-E1a-HN also effectively and selectively decreased the sialic acid level on EC-109 cells, but not on L02 cells. Furthermore, Ad-hTERT-E1a-HN was shown to induce the apoptosis pathway via acridine orange and ethidium bromide staining (AO/EB staining), increase reactive oxygen species (ROS), reduce mitochondrial membrane potential and release cytochrome c. In vivo, xenografted BALB/c nude mice were treated via intratumoral or intravenous injections of Ad-hTERT-E1a-HN. Although both treatments showed an obvious suppression in tumor volume, only Ad-hTERT-E1a-HN delivered via intratumoral injection elicited a complete response to treatment. These results reinforced previous findings and highlighted the potential therapeutic application of Ad-hTERT-E1a-HN for treatment of esophageal cancer in clinical trials.

Tolfenamic acid induces apoptosis and growth inhibition in anaplastic thyroid cancer: Involvement of nonsteroidal anti-inflammatory drug-activated gene-1 expression and intracellular reactive oxygen species generation

Nonsteroidal anti-inflammatory drugs (NSAIDs) are usually used for the treatment of inflammatory diseases. However, certain NSAIDs also have antitumor activities in various cancers, including head and neck cancer, through cyclooxygenase-dependent or independent pathways. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a TGF-β superfamily protein, is induced by NSAIDs and has been shown to be induced by several antitumorigenic compounds and to exhibit proapoptotic and antitumorigenic activities. In this report, we demonstrate for the first time that tolfenamic acid (TA) transcriptionally induced the expression of NAG-1 during TA-induced apoptosis of anaplastic thyroid cancer (ATC) cells. TA reduced the viability of ATC cells in a dose-dependent manner and induced apoptosis, findings that were coincident with NAG-1 expression. Overexpression of the NAG-1 gene using cDNA enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. Subsequently, we found that intracellular ROS generation plays an important role in activating the proapoptotic protein NAG-1. Then, we confirmed antitumorigenic effects of TA in a nude mouse orthotopic ATC model, and this result accompanied the augmentation of NAG-1 expression and ROS generation in tumor tissue. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression and ROS generation in in vitro and in vivo ATC models, providing a novel mechanistic explanation and indicating a potential chemotherapeutic approach for treatment of ATC.

Anti-tumor activity of non-steroidal anti-inflammatory drugs: cyclooxygenase-independent targets

Non-steroidal anti-inflammatory drugs (NSAIDs) are used extensively for analgesic and antipyretic treatments. In addition, NSAIDs reduce the risk and mortality to several cancers. Their mechanisms in anti-tumorigenesis are not fully understood, but both cyclooxygenase (COX)-dependent and -independent pathways play a role. We and others have been interested in elucidating molecular targets of NSAID-induced apoptosis. In this review, we summarize updated literature regarding cellular and molecular targets modulated by NSAIDs. Among those NSAIDs, sulindac sulfide and tolfenamic acid are emphasized in this review because these two drugs have been well investigated for their anti-tumorigenic activity in many different types of cancer.

The involvement of endoplasmic reticulum stress in the suppression of colorectal tumorigenesis by tolfenamic acid

The nonsteroidal anti-inflammatory drug tolfenamic acid has been shown to suppress cancer cell growth and tumorigenesis in different cancer models. However, the underlying mechanism by which tolfenamic acid exerts its antitumorigenic effect remains unclear. Previous data from our group and others indicate that tolfenamic acid alters expression of apoptosis- and cell-cycle arrest-related genes in colorectal cancer cells. Here, we show that tolfenamic acid markedly reduced the number of polyps and tumor load in APC(min)(/+) mice, accompanied with cyclin D1 downregulation in vitro and in vivo. Mechanistically, tolfenamic acid promotes endoplasmic reticulum (ER) stress, resulting in activation of the unfolded protein response (UPR) signaling pathway, of which PERK-mediated phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) induces the repression of cyclin D1 translation. Moreover, the PERK-eIF2α-ATF4 branch of the UPR pathway plays a role in tolfenamic acid-induced apoptosis in colorectal cancer cells, as silencing ATF4 attenuates tolfenamic acid-induced apoptosis. Taken together, these results suggest ER stress is involved in tolfenamic acid-induced inhibition of colorectal cancer cell growth, which could contribute to antitumorigenesis in a mouse model.

Apoptotic effect of methanol extract of Picrasma quassioides by regulating specificity protein 1 in human cervical cancer cells

In the present study, we examined the effects of methanol extracts of Picrasma quassioides (MEPQ) on apoptosis in human cervical cancer cells. The results showed that MEPQ decreased the viability and induced caspase-dependent apoptosis in HEp-2 cells. MEPQ decreased specificity protein 1 (Sp1) in HEp-2 cells, whereas Sp1 mRNA was not changed. We found that MEPQ reduced Sp1 protein through proteasome-dependent protein degradation, but not the inhibition of protein synthesis. Also, MEPQ increased the expressions of Bad and truncated Bid (t-Bid) but did not alter other Bcl-2 family members. The knock-down of Sp1 by both Sp1 interfering RNA and Mithramycin A, Sp1 specific inhibitor clearly increased Bad and t-Bid expression to decrease cell viability and induce apoptosis. In addition, MEPQ inhibited cell viability and induced apoptotic cell death through the modulation of Sp1 in KB cells. These results suggest that MEPQ may be a potential anticancer agent for human cervical cancer.

Reactive oxygen species mediate tolfenamic acid-induced apoptosis in human colorectal cancer cells

Several studies have shown substantial evidences that non-steroidal anti-inflammatory drugs (NSAIDs) exert anticancer effects by generating reactive oxygen species (ROS). Tolfenamic acid (TA) is one of the traditional NSAIDs widely used for treatment of migraine. TA has anti-cancer activities in several human cancer models. In this study, we report that generation of ROS by TA leads to apoptosis through modulation of several pathways in human colorectal cancer cells. TA induced rapid generation of intracellular ROS and led to an increase of phosphorylation of H2AX, a tail moment of comet and distribution of fragmented genomic DNA traces. Treatment of N-acetyl-l-cysteine (NAC) abolished TA-induced phosphorylation of H2AX and apoptosis. Treatment of TA resulted in an increase of nuclear factor-kappaB (NF-κB) transcriptional activity through inhibitor of kappa B (IκB-α) degradation and subsequent p65 nuclear translocation. In addition, TA increased apoptosis-inducing activating transcription factor 3 (ATF3) expression. However, the treatment of NAC abolished TA-mediated NF-κB activation and ATF3 expression and chemical inhibition of NF-κB or knockdown of p65 significantly attenuated TA-induced ATF3 expression. Our finding indicates that ROS-mediated DNA damage and subsequent activation of NF-κB and ATF3 expression plays a significant role in TA-induced apoptosis in human colorectal cancer cells.

Disruption of the transforming growth factor-β pathway by tolfenamic acid via the ERK MAP kinase pathway

Transforming growth factor-β (TGF-β) modulates diverse cell physiological processes and plays a complicated role in tumor development. It has been well established that TGF-β inhibits cell proliferation in normal and early stage carcinoma and facilitates tumor metastasis in late-stage carcinoma. Therefore, blocking TGF-β signaling in advanced stage carcinogenesis provides a potentially interesting chemotherapeutic strategy. We aimed to determine the effect of tolfenamic acid (TA) on TGF-β-induced protumorigenic activity. Here, we demonstrate that TA attenuates tumor-promoting effects of TGF-β in cancer cells. Further observation indicates TA blocks the TGF-β/Smad pathway, and this blockage is mainly attributed to the interference of TGF-β1-driven phosphorylation of Smad2/3. We also show that TA could exert this effect on cancer cell lines from several different origins and that TA is much better than other non-steroidal anti-inflammatory drugs with respect to inhibition of TGF-β1-induced Smad2 phosphorylation. Finally, extracellular signal-regulated kinase mitogen-activated protein kinase plays a role in TA-induced suppression of Smad2/3 phosphorylation and subsequent nuclear accumulation of Smad2/3 in response to TGF-β1. Our study provides a possible mechanism by which TA affects anticancer activity by inhibiting the TGF-β pathway and sheds light on the application of TA for cancer patients.

Apoptotic effect of tolfenamic acid on MDA-MB-231 breast cancer cells and xenograft tumors

Recent studies have indicated that non-steroidal anti-inflammatory drug (NSAID), particularly tolfenamic acid, can inhibit proliferation and induce apoptosis invarious cancer cells. Breast cancer represents one-third of all cancers diagnosed in women and is the second leading cause of cancer death in Western European and North American women. In the present study, we investigated the apoptotic effect of tolfenamic acid in MDA-MB-231 estrogen receptor-negative human breast carcinoma cells and in a xenograft tumor model. Treatment of cells with tolfenamic acid significantly decreased cell viability in a concentration-dependent manner. Notably, tolfenamic acid increased apoptosis-related proteins, such as p53 and p21, within 48 h. Furthermore, in vivo experiments showed that tolfenamic acid treatment resulted in a significant reduction in tumor volume over 5 weeks. Immunohistochemistry results showed that apoptosis-related protein induction by tolfenamic acid was significantly higher in the 50 mg/kg-treated group compared to the control group. Together, these results indicate that tolfenamic acid induces apoptosis in MDA-MB-231 breast cancer cells and tumor xenograft model and it may be a potential chemotherapeutic agent against breast cancer.

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.

The drug resistance suppression induced by curcuminoids in colon cancer SW-480 cells is mediated by reactive oxygen species-induced disruption of the microRNA-27a-ZBTB10-Sp axis

SCOPE

Mechanisms involving the curcuminoids effects in decreasing the prooncogenic specificity protein (Sp) transcription factors, and Sp-regulated genes in SW-480 colon cancer cells and how the multidrug resistance protein (MDR1) inhibition is mediated by Sp suppression.

METHODS AND RESULTS

HT-29 and SW-480 colon cancer and normal CCD-18Co colon fibroblast cells were treated with curcuminoids previously analyzed by HPLC. Gene and protein expression regulation were assessed by RT-PCR, transfections with expression constructs, and Western blots. Curcuminoids (2.5-10 μg/mL) suppressed preferentially the growth of SW-480 and HT-29 compared to CCD-18Co cells and enhanced the anticancer activity of the chemotherapeutic drug 5-fluorouracil due to the suppression of MDR1. Additionally, Sp1, Sp3, and Sp4 and Sp-regulated genes were downregulated by curcuminoids in SW-480 and this was accompanied by suppression of microRNA-27a (miR-27a) and induction of ZBTB10, an mRNA target of miR-27a and a transcriptional repressor of Sp expression. This mechanism was mediated by the induction of ROS. RNA-interference and transfection with ZBTB10-expression plasmid demonstrated that MDR1 was regulated by Sp1 and Sp3 and the disruption of the miR-27a-ZBTB10-Sp axis.

CONCLUSION

Colon cancer treatment with curcuminoids will enhance the therapeutic effects of drugs in patients who have developed drug resistance.

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.

Synergistic anti-cancer effects of resveratrol and chemotherapeutic agent clofarabine against human malignant mesothelioma MSTO-211H cells

Dietary phytochemicals as adjuvants have been suggested to play important roles in enhancing chemotherapeutic potential owing to multitargeted chemopreventive properties and lack of substantial toxicity. Here, we investigated the efficacy of the combined treatment of various phytochemicals with the anticancer drug clofarabine in malignant mesothelioma MSTO-211H cells and normal mesothelial MeT-5A cells. The combined treatment of resveratrol and clofarabine produced a synergistic antiproliferative effect in MSTO-211H cells, but not in MeT-5A cells. In MSTO-211H cells, the nuclear accumulation of Sp1 and the levels of p-Akt, Sp1, c-Met, cyclin D1, and p21 were effectively decreased by the combined treatment of them. In combination with clofarabine, the ability of resveratrol to reduce the contents of Sp1 and its target gene products was also evident in a time- and dose-dependent experiment. The inhibition of phosphoinositide 3-kinase using Ly294002 augmented a decrease in the p21 level induced by their combination, but it showed no significant effects on expression of Sp1 and cyclin D1. Taken together, the data provide evidence that the synergistic antiproliferative effect of resveratrol and clofarabine is linked to the inhibition of Akt and Sp1 activities, and suggest that this combination may have therapeutic value in treatment of malignant mesothelioma.

Small molecule tolfenamic acid inhibits PC-3 cell proliferation and invasion in vitro, and tumor growth in orthotopic mouse model for prostate cancer

BACKGROUND

Specificity protein (Sp) transcription factors are implicated in critical cellular and molecular processes associated with cancer that impact tumor growth and metastasis. The non-steroidal anti-inflammatory drug, tolfenamic acid (TA) is known to inhibit Sp proteins in some human cancer cells and laboratory animal models. We evaluated the anti-cancer activity of TA using in vitro and in vivo models for prostate cancer.

METHODS

The anti-proliferative efficacy of TA was evaluated using DU-145, PC-3, and LNCaP cells. PC-3 cells were treated with DMSO or 50 µM TA for 48 hr. Whole cell lysates were evaluated for the expression of Sp1, survivin, c-PARP, Akt/p-Akt, c-Met, cdk4, cdc2, cyclin D3, and E2F1 by Western blot analysis. Cell invasion was assessed by Boyden-chamber assay and flow cytometry analysis was used to study apoptosis and cell cycle distribution. An orthotopic mouse model for prostate cancer with PC-3-Luc cells was used to study the in vivo effect of TA.

RESULTS

TA inhibited the expression of Sp1, c-Met, p-Akt, and survivin; increased c-PARP expression and caspases activity in PC-3 cells. TA caused cell arrest at G(0) /G(1) phase accompanied by a decrease in cdk4, cdc2, cyclin D3, and E2F1 and an increase in critical apoptotic markers. TA augmented annexin-V staining, caspase activity, and c-PARP expression indicating the activation of apoptotic pathways. TA also decreased PC-3 cell invasion. TA significantly decreased the tumor weight and volume which was associated with low expression of Sp1 and survivin in tumor sections.

CONCLUSION

TA targets critical pathways associated with tumorigenesis and invasion. These pre-clinical data strongly demonstrated the anti-cancer activity of TA in prostate cancer.

Inhibition of rhabdomyosarcoma cell and tumor growth by targeting specificity protein (Sp) transcription factors

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.

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.

Tolfenamic acid induces apoptosis and growth inhibition in head and neck cancer: involvement of NAG-1 expression

Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1) is induced by nonsteroidal anti-inflammatory drugs and possesses proapoptotic and antitumorigenic activities. Although tolfenamic acid (TA) induces apoptosis in head and neck cancer cells, the relationship between NAG-1 and TA has not been determined. This study investigated the induction of apoptosis in head and neck cancer cells treated by TA and the role of NAG-1 expression in this induction. TA reduced head and neck cancer cell viability in a dose-dependent manner and induced apoptosis. The induced apoptosis was coincident with the expression of NAG-1. Overexpression of NAG-1 enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. TA significantly inhibited tumor formation as assessed by xenograft models, and this result accompanied the induction of apoptotic cells and NAG-1 expression in tumor tissue samples. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression in head and neck squamous cell carcinoma, providing an additional mechanistic explanation for the apoptotic activity of TA.

Modulation of the activity of Sp transcription factors by mithramycin analogues as a new strategy for treatment of metastatic prostate cancer

Deregulated activity of transcription factors (TFs) of the Sp/KLF family, like Sp1, Sp3 and Sp4, and consequent over-expression of Sp-regulated genes occur frequently in human cancers. This provides the rationale for development of inhibitors of Sp TFs as cancer therapeutics. Mithramycin A (MTM-A) is a natural polyketide that binds GC-rich DNA sequences, inhibits activity of Sp TFs and exhibits potent antitumor activity in experimental systems. However, clinical use of MTM-A is limited by the severe toxicity of the compound. Here, we studied two MTM-A analogues, which had been generated by genetically engineering of the MTM-A biosynthetic pathway, and evaluated their activity in human prostate cancer in cell cultures and mouse models. The compounds, named MTM-SDK and MTM-SK, were highly effective in vitro inhibiting proliferation of prostate cancer cells and transcription of Sp-regulated genes by blocking binding of Sp proteins to the gene promoters When administered to mice, both compounds were well tolerated with maximum tolerated doses of MTM-SDK and MTM-SK, respectively, 4- and 32- fold higher than MTM-A. After systemic administration, both compounds were cleared rapidly from the bloodstream but maintained plasma levels well above the active concentrations required in vitro for inhibition of Sp TF activity and cell proliferation. Consistently, MTM-SDK and MTM-SK inhibited transcription of Sp-regulated genes in prostate tumor xenografts and exhibited potent antitumor activity in subcutaneous and metastatic tumor xenograft models with no or minimal toxicity. Taken together, these data indicate that MTM-SDK and MTM-SK possess significantly improved pharmacological and toxicological properties compared to MTM-A and represent promising drugs for treatment of advanced prostate cancer.

Betulinic acid decreases ER-negative breast cancer cell growth in vitro and in vivo: role of Sp transcription factors and microRNA-27a:ZBTB10

Betulinic acid (BA), a pentacyclic triterpenoid isolated from tree bark is cytotoxic to cancer cells. There is evidence that specificity proteins (Sps), such as Sp1, Sp3, and Sp4, are overexpressed in tumors and contribute to the proliferative and angiogenic phenotype associated with cancer cells. The objective of this study was to determine the efficacy of BA in decreasing the Sps expression and underlying mechanisms. Results show that BA decreased proliferation and induced apoptosis of estrogen-receptor-negative breast cancer MDA-MB-231 cells. The BA-induced Sp1, Sp3, and Sp4 downregulation was accompanied by increased zinc finger ZBTB10 expression, a putative Sp-repressor and decreased microRNA-27a levels, a microRNA involved in the regulation of ZBTB10. Similar results were observed in MDA-MB-231 cells transfected with ZBTB10 expression plasmid. BA induced cell cycle arrest in the G2/M phase and increased Myt-1 mRNA (a microRNA-27a target gene), which causes inhibition in G2/M by phosphorylation of cdc2. The effects of BA were reversed by transient transfection with a mimic of microRNA-27a. In nude mice with xenografted MDA-MB-231 cells, tumor size and weight were significantly decreased by BA treatment. In tumor tissue, ZBTB10 mRNA was increased while mRNA and protein of Sp1, Sp3 and Sp4, as well as mRNA of vascular endothelial growth factor receptor (VEGFR), survivin and microRNA-27a were decreased by BA. In lungs of xenografted mice, human β2-microglobulin mRNA was decreased in BA-treated animals. These results show that the anticancer effects of BA are at least in part based on interactions with the microRNA-27a-ZBTB10-Sp-axis causing increased cell death.