Downregulation of transcription factor, Sp1, during cellular senescence

Hypothalamic circuits and aging: keeping the circadian clock updated

Over the past century, age-related diseases, such as cancer, type-2 diabetes, obesity, and mental illness, have shown a significant increase, negatively impacting overall quality of life. Studies on aged animal models have unveiled a progressive discoordination at multiple regulatory levels, including transcriptional, translational, and post-translational processes, resulting from cellular stress and circadian derangements. The circadian clock emerges as a key regulator, sustaining physiological homeostasis and promoting healthy aging through timely molecular coordination of pivotal cellular processes, such as stem-cell function, cellular stress responses, and inter-tissue communication, which become disrupted during aging. Given the crucial role of hypothalamic circuits in regulating organismal physiology, metabolic control, sleep homeostasis, and circadian rhythms, and their dependence on these processes, strategies aimed at enhancing hypothalamic and circadian function, including pharmacological and non-pharmacological approaches, offer systemic benefits for healthy aging. Intranasal brain-directed drug administration represents a promising avenue for effectively targeting specific brain regions, like the hypothalamus, while reducing side effects associated with systemic drug delivery, thereby presenting new therapeutic possibilities for diverse age-related conditions.

Cirbp suppression compromises DHODH-mediated ferroptosis defense and attenuates hypothermic cardioprotection in an aged donor transplantation model

Hypothermia is commonly used to protect donor hearts during transplantation. However, patients transplanted with aged donor hearts still have severe myocardial injury and decreased survival rates, but the underlying mechanism remains unknown. Because aged hearts are not considered suitable for donation, the number of patients awaiting heart transplants is increasing. In this study, we examined whether hypothermic cardioprotection was attenuated in aged donor hearts during transplantation and evaluated potential therapeutic targets. Using a rat heart transplantation model, we found that hypothermic cardioprotection was impaired in aged donor hearts but preserved in young donor hearts. RNA-Seq showed that cold-inducible RNA-binding protein (Cirbp) expression was decreased in aged donor hearts, and these hearts showed severe ferroptosis after transplantation. The young donor hearts from Cirbp-KO rats exhibited attenuated hypothermic cardioprotection, but Cirbp overexpression in aged donor hearts ameliorated hypothermic cardioprotection. Cardiac proteomes revealed that dihydroorotate dehydrogenase (DHODH) expression was significantly decreased in Cirbp-KO donor hearts during transplantation. Consequently, DHODH-mediated ubiquinone reduction was compromised, thereby exacerbating cardiac lipid peroxidation and triggering ferroptosis after transplantation. A cardioplegic solution supplemented with CIRBP agonists improved hypothermic cardioprotection in aged donor hearts, indicating that this method has the potential to broaden the indications for using aged donor hearts in transplantation.

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.

What matters in aging is signaling for responsiveness

Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.

Metformin: A Promising Antidiabetic Medication for Cancer Treatment

Metformin is a widely used drug in patients with type 2 diabetes mellitus. Metformin inhibits hepatic gluconeogenesis and increases glucose utilization in peripheral tissues. In recent years, several studies have shown that metformin is a potential therapeutic agent against cancer, alone or combined with other anticancer treatments. Metformin mainly activates the AMPK complex and regulates intracellular energy status, inhibiting the mitochondrial respiratory chain complex I and reducing the production of reactive oxygen species. Other anticancer targets of metformin are specific transcription factors inhibiting cell proliferation, promoting apoptosis and reducing drug resistance. In addition, metformin modulates tumor cells' response to anticancer treatments, favoring the activity of T cells. In diabetic patients, metformin reduces the occurrence of cancer and improves the prognosis and efficacy of anticancer treatments. In this review, we provided a comprehensive perspective of metformin as an anticancer drug.

Evolutionarily conserved transcription factors as regulators of longevity and targets for geroprotection

Aging is the single largest risk factor for many debilitating conditions, including heart diseases, stroke, cancer, diabetes, and neurodegenerative disorders. While far from understood in its full complexity, it is scientifically well-established that aging is influenced by genetic and environmental factors, and can be modulated by various interventions. One of aging's early hallmarks are aberrations in transcriptional networks, controlling for example metabolic homeostasis or the response to stress. Evidence in different model organisms abounds that a number of evolutionarily conserved transcription factors, which control such networks, can affect lifespan and healthspan across species. These transcription factors thus potentially represent conserved regulators of longevity and are emerging as important targets in the challenging quest to develop treatments to mitigate age-related diseases, and possibly even to slow aging itself. This review provides an overview of evolutionarily conserved transcription factors that impact longevity or age-related diseases in at least one multicellular model organism (nematodes, flies, or mice), and/or are tentatively linked to human aging. Discussed is the general evidence for transcriptional regulation of aging and disease, followed by a more detailed look at selected transcription factor families, the common metabolic pathways involved, and the targeting of transcription factors as a strategy for geroprotective interventions.

Down-syndrome-induced senescence disrupts the nuclear architecture of neural progenitors

Down syndrome (DS) is a genetic disorder driven by the triplication of chromosome 21 (T21) and characterized by a wide range of neurodevelopmental and physical disabilities. Transcriptomic analysis of tissue samples from individuals with DS has revealed that T21 induces a genome-wide transcriptional disruption. However, the consequences of T21 on the nuclear architecture and its interplay with the transcriptome remain unknown. In this study, we find that unlike human induced pluripotent stem cells (iPSCs), iPSC-derived neural progenitor cells (NPCs) exhibit genome-wide "chromosomal introversion," disruption of lamina-associated domains, and global chromatin accessibility changes in response to T21, consistent with the transcriptional and nuclear architecture changes characteristic of senescent cells. Treatment of T21-harboring NPCs with senolytic drugs alleviates the transcriptional, molecular, and cellular dysfunctions associated with DS. Our findings provide a mechanistic link between T21 and global transcriptional disruption and indicate that senescence-associated phenotypes may play a key role in the neurodevelopmental pathogenesis of DS.

Transcription factors specificity protein and nuclear receptor 4A1 in pancreatic cancer

Specificity protein (Sp) transcription factors (TFs) Sp1, Sp3 and Sp4, and the orphan nuclear receptor 4A1 (NR4A1) are highly expressed in pancreatic tumors and Sp1 is a negative prognostic factor for pancreatic cancer patient survival. Results of knockdown and overexpression of Sp1, Sp3 and Sp4 in pancreatic and other cancer lines show that these TFs are individually pro-oncogenic factors and loss of one Sp TF is not compensated by other members. NR4A1 is also a pro-oncogenic factor and both NR4A1 and Sp TFs exhibit similar functions in pancreatic cancer cells and regulate cell growth, survival, migration and invasion. There is also evidence that Sp TFs and NR4A1 regulate some of the same genes including survivin, epidermal growth factor receptor, PAX3-FOXO1, α5- and α6-integrins, β1-, β3- and β4-integrins; this is due to NR4A1 acting as a cofactor and mediating NR4A1/Sp1/4-regulated gene expression through GC-rich gene promoter sites. Several studies show that drugs targeting Sp downregulation or NR4A1 antagonists are highly effective inhibitors of Sp/NR4A1-regulated pathways and genes in pancreatic and other cancer cells, and the triterpenoid celastrol is a novel dual-acting agent that targets both Sp TFs and NR4A1.

DNA damage-induced degradation of Sp1 promotes cellular senescence

Persistent DNA damage (genotoxic stress) triggers signaling cascades that drive cells into apoptosis or senescence to avoid replicating a damaged genome. Sp1 has been found to play a role in double strand break (DSB) repair, and a link between Sp1 and aging has also been established, where Sp1 protein, but not RNA, levels decrease with age. Interestingly, inhibition ATM reverses the age-related degradation of Sp1, suggesting that DNA damage signaling is involved in senescence-related degradation of Sp1. Proteasomal degradation of Sp1 in senescent cells is mediated via sumoylation, where sumoylation of Sp1 on lysine 16 is increased in senescent cells. Taking into consideration our previous findings that Sp1 is phosphorylated by ATM in response to DNA damage and that proteasomal degradation of Sp1 at DSBs is also mediated by its sumoylation and subsequent interaction with RNF4, we investigated the potential contribution of Sp1’s role as a DSB repair factor in mediating cellular senescence. We report here that Sp1 expression is decreased with a concomitant increase in senescence markers in response to DNA damage. Mutation of Sp1 at serine 101 to create an ATM phospho-null mutant, or mutation of lysine 16 to create a sumo-null mutant, prevents the sumoylation and subsequent proteasomal degradation of Sp1 and results in a decrease in senescence. Conversely, depletion of Sp1 or mutation of Sp1 to create an ATM phosphomimetic results in premature degradation of Sp1 and an increase in senescence markers. These data link a loss of genomic stability with senescence through the action of a DNA damage repair factor.

Role of stress granules in modulating senescence and promoting cancer progression: Special emphasis on glioma

Stress granules (SGs) contain mRNAs and proteins stalled in translation during stress; these are increasingly being implicated in diseases, including neurological disorders and cancer. The dysregulated assembly, persistence, disassembly and clearance of SGs contribute to the process of senescence. Senescence has long been a mysterious player in cellular physiology and associated diseases. The systemic process of aging has been pivotal in the development of various neurological disorders like age-related neuropathy, Alzheimer's disease and Parkinson's disease. Glioma is a cancer of neurological origin with a very poor prognosis and high rate of recurrence, SGs have only recently been implicated in its pathogenesis. Senescence has long been established to play an antitumorigenic role, however, relatively less studied is its protumorigenic importance. Here, we have evaluated the existing literature to assess the crosstalk of the two biological phenomena of senescence and SG formation in the context of tumorigenesis. In this review, we have attempted to analyze the contribution of senescence in regulating diverse cellular processes, like, senescence associated secretory phenotype (SASP), microtubular reorganization, telomeric alteration, autophagic clearance and how intricately these phenomena are tied with the formation of SGs. Finally, we propose that interplay between senescence, its contributing factors and the genesis of SGs can drive tumorigenicity of gliomas, which can potentially be utilized for therapeutic intervention.

Detection of genetic variation and activity analysis of the promoter region of the cattle tRNA-modified gene TRDMT1

The tRNA modification gene in eukaryotes is relatively conservative. As an important modification gene, the TRDMT1 gene plays an important role in maintaining tRNA structural maintenance and reducing mistranslation of protein translation by methylation of specific tRNA subpopulations. Mouse and zebrafish TRDMT1 knockout experiments indicate that it may mediate growth and development through tRNA modification. However, there are no systematic reports on the function of tRNA-modified genes in livestock. In this study, Qinchuan cattle DNA pool sequencing technology was used. A G>C mutation in the -1223 bp position upstream of the TRDMT1 translation initiator codon was found. At this locus, the dual-luciferase assay indicated that different genotypes cause differences in transcriptional activity (P<0.05). Our experiment detected a natural genetic variation of a tRNA modification gene TRDMT1, which may provide potential natural molecular materials for the study of tRNA modification.

Inhibition of Specificity Protein 1 Is Involved in Phloretin-Induced Suppression of Prostate Cancer

Phloretin is a flavonoid existed in various plants and has been reported to possess anticarcinogenic activity. However, the anticancer mechanism of phloretin in prostate cancer (PCa) remains unclear. Here, our in vitro and in vivo experimental data demonstrate that phloretin inhibits the phosphorylation and the activation of EGFR and then inhibits its downstream PI3K/AKT and MEK/ERK1/2 pathways in PCa cells. Inhibition of these two pathways further decreases expression of Sp1 by inhibiting Sp1 gene transcription, induces degradation of Sp1 protein by inhibiting GSK3β phosphorylation, suppresses nucleolin-enhanced translation of Sp1 mRNA by inhibiting nucleolin phosphorylation, and directly inactivates transcription activity of Sp1. Inhibition of Sp1 subsequently decreases the expression of Sp3/4, VEGF, and Survivin and then upregulates apoptosis-related proteins and downregulates cell cycle-related proteins in PCa cells. Finally, phloretin treatment in PCa cells induces cell growth inhibition and apoptosis, suggesting that phloretin may be an effective therapy compound in the treatment of prostate cancer.

The role of Sp1 in the detection and elimination of cells with persistent DNA strand breaks

Maintenance of genome stability suppresses cancer and other human diseases and is critical for organism survival. Inevitably, during a life span, multiple DNA lesions can arise due to the inherent instability of DNA molecules or due to endogenous or exogenous DNA damaging factors. To avoid malignant transformation of cells with damaged DNA, multiple mechanisms have evolved to repair DNA or to detect and eradicate cells accumulating unrepaired DNA damage. In this review, we discuss recent findings on the role of Sp1 (specificity factor 1) in the detection and elimination of cells accumulating persistent DNA strand breaks. We also discuss how this mechanism may contribute to the maintenance of physiological populations of healthy cells in an organism, thus preventing cancer formation, and the possible application of these findings in cancer therapy.

MiR-29c protects against inflammation and apoptosis in Parkinson's disease model in vivo and in vitro by targeting SP1

MicroRNAs (miRNAs) have been shown to have complicated implications in the pathogenesis of Parkinson's disease (PD). However, the role of miR-29c and the underlying mechanism in the development of PD remain not well understood. In this work, the MPTP-treated mice or MPP+ -intoxicated SH-SY5Y cells were established as an in vivo or in vitro PD model. Then the specific agomir of miR-29c was employed to examine its biological function on PD progress. We found that miR-29c was down-expressed but SP1 was high-expressed in substantia nigra pars compacta (SNpc) of MPTP-induced PD mice. Overexpression of miR-29c attenuated dopaminergic neuron loss and α-synuclein accumulation in SNpc of PD mice. Furthermore, the increments of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and TUNEL-positive apoptotic cells in MPTP-treated mice were ameliorated by miR-29c. Similarly, in SH-SY5Y cell models of PD, we also found that miR-29c inhibited inflammatory cytokine production, reduced apoptotic rate and suppressed pro-apoptotic regulator activity. In addition, the increased expression of SP1 in PD models was found to be inhibited by miR-29c. Luciferase reporter assay confirmed that SP1 was complementary with miR-29c. Knockdown of SP1 with siRNA restored α-synuclein accumulation, inflammation and apoptosis in MPP+ -induced SH-SY5Y cells. Collectively, this current work presents that miR-29c may directly target SP1 to protect against the neuroinflammatory and apoptotic responses in PD, providing a potential biomarker for PD diagnosis and treatment.

Hallmarks of Aging in the Liver

While the liver demonstrates remarkable resilience during aging, there is growing evidence that it undergoes all the cellular hallmarks of aging, which increases the risk of liver and systemic disease. The aging process in the liver is driven by alterations of the genome and epigenome that contribute to dysregulation of mitochondrial function and nutrient sensing pathways, leading to cellular senescence and low-grade inflammation. These changes promote multiple phenotypic changes in all liver cells (hepatocytes, liver sinusoidal endothelial, hepatic stellate and Küpffer cells) and impairment of hepatic function. In particular, age-related changes in the liver sinusoidal endothelial cells are a significant but under-recognized risk factor for the development of age-related cardiometabolic disease.

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Liver aging is driven by transcription and metabolic epigenome alterations.

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This leads to cellular senescence and low-grade inflammation.

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Hepatocyte, sinusoidal endothelial, stellate and Küpffer cells undergoes the hallmarks of aging.

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Each cell type demonstrates phenotypical cellular changes with age.

7,12-Dimethylbenz[α]anthracene increases cell proliferation and invasion through induction of Wnt/β-catenin signaling and EMT process

7,12-Dimethylbenz[α]anthracene (DMBA) is a hazardous component present in polluted environments. DMBA has been used as an experimental tool for in vivo tumor formation owing to its carcinogenic effects, but the detailed molecular mechanism of DMBA has not been fully established. To comprehend the carcinogenic mechanism of DMBA, we explored its effects in the breast cancer cell lines, MCF-7 and MDA-MB-231, and the cervical cancer cell line, HeLa. Cell viability assay and measurement of a proliferation marker showed that DMBA markedly increased cancer cell proliferation. Furthermore, morphological observations and wound healing assays in nontumorigenic MCF-10A cells and trans-well invasion assays in cancer cells following DMBA treatment revealed that DMBA induced cell migration and invasion. To reveal the molecular mechanism of DMBA, we investigated the effects of DMBA on the epithelial-mesenchymal transition (EMT) process and Wnt/β-catenin signaling, a critical pathway for cell proliferation that was reported to correlate with the EMT process, by using quantitative RT-PCR (qPCR), western blot analysis, and confocal microscopy. Consequently, we found that DMBA increased cancer cell proliferation and invasion through the promotion of EMT-inducing factors and β-catenin. Especially, it was revealed in promoter activity assay using mutated luciferase vectors on transcription factor-binding sites that TWIST1 is promoted by DMBA through induction of STAT3-mediated promoter activation. To further elucidate the detailed mechanism of DMBA, we aimed to identify the key regulator of its carcinogenic action. DMBA was shown to significantly upregulate the expression of specificity protein 1 (Sp1), a transcription factor, and the carcinogenic effects of DMBA were blocked via the suppression or interruption of Sp1 activity. In conclusion, our data suggested that DMBA induced carcinogenic effects through activation of Wnt/β-catenin signaling and the EMT process by upregulating Sp1 activity.

Specificity Protein Transcription Factors and Cancer: Opportunities for Drug Development

Specificity protein (Sp) transcription factors (TFs) such as Sp1 are critical for early development but their expression decreases with age and there is evidence that transformation of normal cells to cancer cells is associated with upregulation of Sp1, Sp3, and Sp4, which are highly expressed in cancer cells and tumors. Sp1 is a negative prognostic factor for pancreatic, colon, glioma, gastric, breast, prostate, and lung cancer patients. Functional studies also demonstrate that Sp TFs regulate genes responsible for cancer cell growth, survival, migration/invasion, inflammation and drug resistance, and Sp1, Sp3 and Sp4 are also nononcogene addiction (NOA) genes and important drug targets. The mechanisms of drug-induced downregulation of Sp TFs and pro-oncogenic Sp-regulated genes are complex and include ROS-dependent epigenetic pathways that initially decrease expression of the oncogene cMyc. Many compounds such as curcumin, aspirin, and metformin that are active in cancer prevention also exhibit chemotherapeutic activity and these compounds downregulate Sp TFs in cancer cell lines and tumors. The effects of these compounds on downregulation of Sp TFs in normal cells and the contribution of this response to their chemopreventive activity have not yet been determined. Cancer Prev Res; 11(7); 371-82. ©2018 AACR.

Survive or thrive: tradeoff strategy for cellular senescence

Aging-dependent cellular behaviors toward extrinsic stress are characterized by the confined localization of certain molecules to either nuclear or perinuclear regions. Although most growth factors can activate downstream signaling in aging cells, they do not in fact have any impact on the cells because the signals cannot reach their genetic targets in the nucleus. For the same reason, varying apoptotic stress factors cannot stimulate the apoptotic pathway in senescent cells. Thus, the operation of a functional nuclear barrier in an aging-dependent manner has been investigated. To elucidate the mechanism for this process, the housekeeping transcription factor Sp1 was identified as a general regulator of nucleocytoplasmic trafficking (NCT) genes, including various nucleoporins, importins, exportins and Ran GTPase cycle-related genes. Interestingly, the posttranslational modification of Sp1 is readily influenced by extrinsic stress, including oxidative and metabolic stress. The decrease in SP1 O-GlcNAcylation under oxidative stress or during replicative senescence makes it susceptible to proteosomal degradation, resulting in defective NCT functions and leading to nuclear barrier formation. The operation of the nuclear barrier in aging provides a fundamental mechanism for cellular protection against stress and promotes survival at the expense of growth via stress-sensitive transcriptional control.

Specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 are non-oncogene addiction genes in cancer cells

Specificity protein (Sp) transcription factor (TF) Sp1 is overexpressed in multiple tumors and is a negative prognostic factor for patient survival. Sp1 and also Sp3 and Sp4 are highly expressed in cancer cells and in this study, we have used results of RNA interference (RNAi) to show that the three TFs individually play a role in the growth, survival and migration/invasion of breast, kidney, pancreatic, lung and colon cancer cell lines. Moreover, tumor growth in athymic nude mice bearing L3.6pL pancreatic cancer cells as xenografts were significantly decreased in cells depleted for Sp1, Sp3 and Sp4 (combined) or Sp1 alone. Ingenuity Pathway Analysis (IPA) of changes in gene expression in Panc1 pancreatic cancer cells after individual knockdown of Sp1, Sp3 and Sp4 demonstrates that these TFs regulate genes and pathways that correlated with the functional responses observed after knockdown but also some genes and pathways that inversely correlated with the functional responses. However, causal IPA analysis which integrates all pathway-dependent changes in all genes strongly predicted that Sp1-, Sp3- and Sp4-regulated genes were associated with the pro-oncogenic activity. These functional and genomic results coupled with overexpression of Sp transcription factors in tumor vs. non-tumor tissues and decreased Sp1 expression with age indicate that Sp1, Sp3 and Sp4 are non-oncogene addiction (NOA) genes and are attractive drug targets for individual and combined cancer chemotherapies.

A Systematic Investigation into Aging Related Genes in Brain and Their Relationship with Alzheimer's Disease

Aging, as a complex biological process, is accompanied by the accumulation of functional loses at different levels, which makes age to be the biggest risk factor to many neurological diseases. Even following decades of investigation, the process of aging is still far from being fully understood, especially at a systematic level. In this study, we identified aging related genes in brain by collecting the ones with sustained and consistent gene expression or DNA methylation changes in the aging process. Functional analysis with Gene Ontology to these genes suggested transcriptional regulators to be the most affected genes in the aging process. Transcription regulation analysis found some transcription factors, especially Specificity Protein 1 (SP1), to play important roles in regulating aging related gene expression. Module-based functional analysis indicated these genes to be associated with many well-known aging related pathways, supporting the validity of our approach to select aging related genes. Finally, we investigated the roles of aging related genes on Alzheimer's Disease (AD). We found that aging and AD related genes both involved some common pathways, which provided a possible explanation why aging made the brain more vulnerable to Alzheimer's Disease.

Transcription factor Sp1 prevents TRF2(ΔBΔM)-induced premature senescence in human diploid fibroblasts

Telomere uncapping is thought to be the fundamental cause of replicative cellular senescence, but the cellular machineries mediating this process have not been fully understood. In the present study, we present the role of Sp1 transcription factor in the state of telomere uncapping using the TRF2(ΔBΔM)-induced senescence model in human diploid fibroblasts. We observed that the expression of Sp1 is down-regulated in the TRF2(ΔBΔM)-induced senescence, which was mediated by ATM and p38 MAPK. In addition, overexpression of Sp1 prevented the TRF2(ΔBΔM)-induced senescence. Among transcriptional targets of Sp1, expression levels of nuclear transport genes such as karyopherin α, Nup107, and Nup50 were down-regulated in the TRF2(ΔBΔM)-induced senescence, which was prevented by Sp1 overexpression. Moreover, inhibition of the nuclear transport by wheat germ agglutinin (an import inhibitor) and leptomycin B (an export inhibitor) induced premature senescence. These results suggest that Sp1 is an anti-senescence transcription factor in the telomere uncapping-induced senescence and that down-regulation of Sp1 leads to the senescence via down-regulation of the nuclear transport.

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.

Sulindac sulfide inhibits colon cancer cell growth and downregulates specificity protein transcription factors

Background

Specificity protein (Sp) transcription factors play pivotal roles in maintaining the phenotypes of many cancers. We hypothesized that the antineoplastic effects of sulindac and its metabolites were due, in part, to targeting downregulation of Sp transcription factors.

Methods

The functional effects of sulindac, sulindac sulfone and sulindac sulfide on colon cancer cell proliferation were determined by cell counting. Effects of these compounds on expression of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes were determined by western blot analysis of whole cell lysates and in transient transfection assays using GC-rich constructs.

Results

Sulindac and its metabolites inhibited RKO and SW480 colon cancer cell growth and the order of growth inhibitory potency was sulindac sulfide > > sulindac sulfone > sulindac. Treatment of SW480 and RKO cells with sulindac sulfide downregulated expression of Sp1, Sp3 and Sp4 proteins. Sulindac sulfide also decreased expression of several Sp-regulated genes that are critical for cancer cell survival, proliferation and angiogenesis and these include survivin, bcl-2, epidermal growth factor receptor (EGFR), cyclin D1, p65 subunit of NFκB and vascular endothelial growth factor (VEGF). Sulindac sulfide also induced reactive oxygen species (ROS) and decreased the level of microRNA-27a in colon cancer cells, which resulted in the upregulation of the Sp-repressor ZBTB10 and this resulted in downregulation of Sp proteins.

Conclusions

The results suggest that the cancer chemotherapeutic effects of sulindac in colon cancer cells are due, in part, to its metabolite sulindac sulfide which downregulates Sp transcription factors and Sp-regulated pro-oncogenic gene products.

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.

Sp1 and the 'hallmarks of cancer'

For many years, transcription factor Sp1 was viewed as a basal transcription factor and relegated to a role in the regulation of so-called housekeeping genes. Identification of Sp1's role in recruiting the general transcription machinery in the absence of a TATA box increased its importance in gene regulation, particularly in light of recent estimates that the majority of mammalian genes lack a TATA box. In this review, we briefly consider the history of Sp1, the founding member of the Sp family of transcription factors. We review the evidence suggesting that Sp1 is highly regulated by post-translational modifications that positively and negatively affect the activity of Sp1 on a wide array of genes. Sp1 is over-expressed in many cancers and is associated with poor prognosis. Targeting Sp1 in cancer treatment has been suggested; however, our review of the literature on the role of Sp1 in the regulation of genes that contribute to the 'hallmarks of cancer' illustrates the extreme complexity of Sp1 functions. Sp1 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, as well as genes involved in essential cellular functions, including proliferation, differentiation, the DNA damage response, apoptosis, senescence and angiogenesis. Sp1 is also implicated in inflammation and genomic instability, as well as epigenetic silencing. Given the apparently opposing effects of Sp1, a more complete understanding of the function of Sp1 in cancer is required to validate its potential as a therapeutic target.

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.

REACTIVE OXYGEN SPECIES AND COLORECTAL CANCER

Several agents used for treatment of colon and other cancers induce reactive oxygen species (ROS) and this plays an important role in their anticancer activities. In addition to the well-known proapoptotic effects of ROS inducers, these compounds also decrease expression of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and several pro-oncogenic Spregulated genes important for cancer cell proliferation, survival and metastasis. The mechanism of these responses involve ROS-dependent downregulation of microRNA-27a (miR-27a) or miR-20a (and paralogs) and induction of two Sp-repressors, ZBTB10 and ZBTB4 respectively. This pathway significantly contributes to the anticancer activity of ROS inducers and should be considered in development of drug combinations for cancer chemotherapy.

Late-life rapamycin treatment reverses age-related heart dysfunction

Rapamycin has been shown to extend lifespan in numerous model organisms including mice, with the most dramatic longevity effects reported in females. However, little is known about the functional ramifications of this longevity-enhancing paradigm in mammalian tissues. We treated 24-month-old female C57BL/6J mice with rapamycin for 3 months and determined health outcomes via a variety of noninvasive measures of cardiovascular, skeletal, and metabolic health for individual mice. We determined that while rapamycin has mild transient metabolic effects, there are significant benefits to late-life cardiovascular function with a reversal or attenuation of age-related changes in the heart. RNA-seq analysis of cardiac tissue after treatment indicated inflammatory, metabolic, and antihypertrophic expression changes in cardiac tissue as potential mechanisms mediating the functional improvement. Rapamycin treatment also resulted in beneficial behavioral, skeletal, and motor changes in these mice compared with those fed a control diet. From these findings, we propose that late-life rapamycin therapy not only extends the lifespan of mammals, but also confers functional benefits to a number of tissues and mechanistically implicates an improvement in contractile function and antihypertrophic signaling in the aged heart with a reduction in age-related inflammation.

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.

Type II TGFβ receptor modulates chondrocyte phenotype

Aging is one of the major risk factors of osteoarthritis. This pathology during which chondrocytes undergo modifications of their phenotype may result from alteration of transforming growth factor β (TGFβ) signaling. This study investigates the role of TGFβ response in the process of chondrocyte dedifferentiation/redifferentiation. Dedifferentiation was induced by successive passages of human articular chondrocytes, whereas their redifferentiation was performed by three-dimensional culture in alginate. Human mesenchymal stem cells were obtained from bone marrow and differentiated into chondrocyte-like phenotype by three-dimensional culture, embedded in the same scaffold. Protein and mRNA levels were analyzed by Western blot and real-time reverse transcription PCR. Regulatory mechanism was investigated using specific inhibitors (mithramycin), mRNA silencing or decoy oligonucleotides, and expression vectors. Chondrocyte dedifferentiation interfered with TGFβ signaling by decreasing TβRII mRNA and protein levels and subsequent TGFβ response. TβRII ectopic expression in passaged chondrocytes permitted to increase the expression of several matrix genes, such as aggrecan or type II collagen. Redifferentiation of passaged chondrocytes permitted to restore, at least in part, TβRII expression and was related to differentiation of human bone marrow mesenchymal stem cells toward chondrocytes, where both specific protein 1 (Sp1) and TβRII mRNA levels were increased. Moreover, Sp1 manipulation by silencing or ectopic expression and pharmacologic inhibition revealed a link between expression levels of this transcriptional factor, which is crucial for constitutive expression of TβRII in cartilage, and TGFβ response. Therefore, these data permit us to suggest an important role of TβRII expression in the maintenance of chondrocyte phenotype, which is altered with age, and bring new insights in our understanding of chondrogenesis process.

The transcription factor Sp1 is responsible for aging-dependent altered nucleocytoplasmic trafficking

Hyporesponsiveness to external signals, such as growth factors and apoptotic stimuli, is a cardinal feature of cellular senescence. We previously reported that an aging-dependent marked reduction in nucleocytoplasmic trafficking (NCT)-related genes could be responsible for this phenomenon. In searching for the mechanism, we identified the transcription factor, Sp1, as a common regulator of NCT genes, including various nucleoporins, importins, exportins, and Ran GTPase cycle-related genes. Sp1 knockdown led to a reduction of those genes in young human diploid fibroblast cells (HDF); Sp1 overexpression induced those genes in senescent cells. In addition, epidermal growth factor stimulation-induced p-ERK1/2 nuclear translocation and Elk-1 phosphorylation were severely impaired by Sp1 depletion in young HDFs; Sp1 overexpression restored the nuclear translocation of p-ERK1/2 in senescent HDFs. Furthermore, we observed that Sp1 protein levels were decreased in senescent cells, and H(2) O(2) treatment decreased Sp1 levels in a proteasome-dependent manner. In addition, O-GlcNAcylation of Sp1 was decreased in senescent cells as well as in H(2) O(2) -treated cells. Taken together, these results suggest that Sp1 could be a key regulator in the control of NCT genes and that reactive oxygen species-mediated alteration in Sp1 stability may be responsible for the generalized repression of those genes, leading to formation of the senescence-dependent functional nuclear barrier, resulting in subsequent hyporesponsiveness to external signals.

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.

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.

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.

Pharmacologic doses of ascorbic acid repress specificity protein (Sp) transcription factors and Sp-regulated genes in colon cancer cells

Ascorbic acid (vitamin C) inhibits cancer cell growth, and there is a controversy regarding the cancer chemoprotective effects of pharmacologic doses of this compound that exhibits prooxidant activity. We hypothesized that the anticancer activity of pharmacologic doses of ascorbic acid (<5 mM) is due, in part, to reactive oxygen species-dependent downregulation of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and Sp-regulated genes. In this study, ascorbic acid (1-3 mM) decreased RKO and SW480 colon cancer cell proliferation and induced apoptosis and necrosis, and this was accompanied by downregulation of Sp1, Sp3, and Sp4 proteins. In addition, ascorbic acid decreased expression of several Sp-regulated genes that are involved in cancer cell proliferation [hepatocyte growth factor receptor (c-Met), epidermal growth factor receptor and cyclin D1], survival (survivin and bcl-2), and angiogenesis [vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2)]. Other prooxidants such as hydrogen peroxide exhibited similar activities in colon cancer cells, and cotreatment with glutathione inhibited these responses. This study demonstrates for the first time that the anticancer activities of ascorbic acid are due, in part, to ROS-dependent repression of Sp transcription factors.

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.

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

Methyl 2-cyano-3,11-dioxo-18β-olean-1,12-dien-30-oate (CDODA-Me) and the corresponding 2-trifluoromethyl analog (CF(3)DODA-Me) are derived synthetically from the triterpenoid glycyrrhetinic acid, a major component of licorice. CDODA-Me and CF(3)DODA-Me inhibited growth of highly invasive ARO, DRO, K-18, and HTh-74 thyroid cancer cells and this was due, in part, to decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 that are overexpressed in these cells. CDODA-Me and CF(3)DODA-Me also decreased expression of Sp-dependent genes, such as survivin and vascular endothelial growth factor (VEGF), and induced apoptosis. In addition, pituitary tumor-transforming gene-1 (PTTG-1) protein and mRNA levels were also decreased in thyroid cancer cells treated with CDODA-Me or CF(3)DODA-Me and this was accompanied by decreased expression of PTTG-1-dependent c-Myc and fibroblast growth factor-2 (FGF-2) genes. RNA interference studies against Sp1, Sp3, and Sp4 proteins showed that in thyroid cancer cells, PTTG-1 was an Sp-dependent gene. This study demonstrates for the first time that drugs, such as CDODA-Me and CF(3)DODA-Me, that decrease Sp protein expression also downregulate PTTG-1 in thyroid cancer cells and therefore have potential for clinical treatment of thyroid cancer and other endocrine neoplasias where PTTG-1 is a major pro-oncogenic factor.

Increased expression of miR-34a and miR-93 in rat liver during aging, and their impact on the expression of Mgst1 and Sirt1

Age-dependent loss of oxidative defense is well recognized in rodent models, although the control mechanism is still obscure; a few studies have shown how microRNAs, a non-coding RNA species, regulate the expression of their target genes at the post-transcriptional level. In the current study, miR-34a and miR-93 are observed to increase in middle- and old-age rat liver, compared to young rats; the up-regulation of these two miRNAs is determined by qPCR through a grind-and-find approach, and histochemical in situ hybridization. Three commonly used miRNA target prediction programs suggest four candidate targets of miR-34a and miR-93: Sp1, Nrf2 (Nfe2l2), Sirt1 and Mgst1; their expression is found to be reduced inversely to the up-regulation of the two miRNAs by Western blotting of protein extracts, as well as immunofluorescence staining of intact liver tissues. Furthermore, the suppression of the four proteins by miR-34a/miR-93 is examined in HEK 293 cells by transfection and co-transfection; miR-34a represses all four proteins' expression, whereas miR-93 affects only Sp1, Sirt1 and Mgst1. Taken together, our study suggests a model of post-transcriptional repression, not only of genes involved in oxidative stress regulation and oxidative stress defense proteins, such as Sirt1 and Mgst1, but also of upstream transcription factors (TFs) regulating their activation, since Sp1 is the TF for both Sirt1 and Mgst1, and Nrf2 is the TF of Mgst1. Thus, up-regulation of both miR-34a and miR-93 constitutes an inescapable repression of two vital oxidative defense genes, by targeting not only the targets, but also transcription factors controlling their activation, a double dampening regulation at the post-transcriptional level.

Arsenic trioxide downregulates specificity protein (Sp) transcription factors and inhibits bladder cancer cell and tumor growth

Arsenic trioxide exhibits antiproliferative, antiangiogenic and proapoptotic activity in cancer cells, and many genes associated with these responses are regulated by specificity protein (Sp) transcription factors. Treatment of cancer cells derived from urologic (bladder and prostate) and gastrointestinal (pancreas and colon) tumors with arsenic trioxide demonstrated that these cells exhibited differential responsiveness to the antiproliferative effects of this agent and this paralleled their differential repression of Sp1, Sp3 and Sp4 proteins in the same cell lines. Using arsenic trioxide-responsive KU7 and non-responsive 253JB-V bladder cancer cells as models, we show that in KU7 cells, < or =5 microM arsenic trioxide decreased Sp1, Sp3 and Sp4 and several Sp-dependent genes and responses including cyclin D1, epidermal growth factor receptor, bcl-2, survivin and vascular endothelial growth factor, whereas at concentrations up to 15 microM, minimal effects were observed in 253JB-V cells. Arsenic trioxide also inhibited tumor growth in athymic mice bearing KU7 cells as xenografts, and expression of Sp1, Sp3 and Sp4 was significantly decreased. Inhibitors of oxidative stress such as glutathione or dithiothreitol protected KU7 cells from arsenic trioxide-induced antiproliferative activity and Sp repression, whereas glutathione depletion sensitized 253JB-V cells to arsenic trioxide. Mechanistic studies suggested that arsenic trioxide-dependent downregulation of Sp and Sp-dependent genes was due to decreased mitochondrial membrane potential and induction of reactive oxygen species, and the role of peroxides in mediating these responses was confirmed using hydrogen peroxide.

Tissue engineering of skin and cornea: Development of new models for in vitro studies

Human beings are greatly preoccupied with the unavoidable nature of aging. While the biological processes of senescence and aging are the subjects of intense investigations, the molecular mechanisms linking aging with disease and death are yet to be elucidated. Tissue engineering offers new models to study the various processes associated with aging. Using keratin 19 as a stem cell marker, our studies have revealed that stem cells are preserved in human skin reconstructed by tissue engineering and that the number of epithelial stem cells varies according to the donor's age. As with skin, human corneas can also be engineered in vitro. Among the epithelial cells used for reconstructing skin and corneas, significant age-dependent variations in the expression of the transcription factor Sp1 were observed. Culturing skin epithelial cells with a feeder layer extended their life span in culture, likely by preventing Sp1 degradation in epithelial cells, therefore demonstrating the pivotal role played by this transcription factor in cell proliferation. Finally, using the human tissue-engineered skin as a model, we linked Hsp27 activation with skin differentiation.

MicroRNA-27a Indirectly Regulates Estrogen Receptor {alpha} Expression and Hormone Responsiveness in MCF-7 Breast Cancer Cells

MicroRNA-27a (miR-27a) is expressed in MCF-7 breast cancer cells, and antisense miR-27a (as-miR-27a) induces ZBTB10, a specificity protein (Sp) repressor. Both as-miR-27a and overexpression of ZBTB10 decreased Sp1, Sp3, and Sp4 mRNA and protein expression in MCF-7 cells, and this was also accompanied by decreased levels of estrogen receptor alpha (ERalpha) mRNA and protein. RNA interference studies confirmed that basal expression of ERalpha was dependent on Sp1 but not Sp3 or Sp4 in MCF-7 cells. as-miR-27a and overexpression of ZBTB10 inhibited 17beta-estradiol (E2)-induced transactivation in MCF-7 cells, and this was accompanied by decreased binding of Sp and ER proteins in cell lysates to oligonucleotides containing GC-rich motifs or estrogen-responsive elements, respectively. as-miR-27a and overexpression of ZBTB10 arrested MCF-7 cells in G(0)/G(1) and inhibited E2-induced G(0)/G(1) to S phase progression. as-miR-27a induced only a minimal increase in Myt-1, another miR-27a regulated gene, and this was not accompanied by Myt-1-dependent G(2)/M arrest as observed previously in ER-negative MDA-MB-231 breast cancer cells. Thus, miR-27a indirectly regulates E2-responsiveness in MCF-7 cells through suppression of ZBTB10, thereby enhancing expression of ERalpha.

Methyl 2-cyano-3,12-dioxooleana-1,9-dien-28-oate decreases specificity protein transcription factors and inhibits pancreatic tumor growth: role of microRNA-27a

The anticancer agent 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and its methyl ester (CDDO-Me) typically induce a broad spectrum of growth-inhibitory, proapoptotic, and antiangiogenic responses. Treatment of Panc1, Panc28, and L3.6pL pancreatic cancer cells with low micromolar concentrations of CDDO or CDDO-Me resulted in growth inhibition, induction of apoptosis, and down-regulation of cyclin D1, survivin, vascular endothelial growth factor (VEGF), and its receptor (VEGFR2). RNA interference studies indicate that these repressed genes are regulated by specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, and Western blot analysis of lysates from pancreatic cancer cells treated with CDDO and CDDO-Me shows for the first time that both compounds decreased the expression of Sp1, Sp3, and Sp4. Moreover, CDDO-Me (7.5 mg/kg/day) also inhibited pancreatic human L3.6pL tumor growth and down-regulated Sp1, Sp3, and Sp4 in tumors using an orthotopic pancreatic cancer model. CDDO-Me also induced reactive oxygen species (ROS) and decreased mitochondrial membrane potential (MMP) in Panc1 and L3.6pL cells, and cotreatment with antioxidants (glutathione and dithiothreitol) blocked the formation of ROS, reversed the loss of MMP, and inhibited down-regulation of Sp1, Sp3, and Sp4. Repression of Sp and Sp-dependent genes by CDDO-Me was due to the down-regulation of microRNA-27a and induction of zinc finger and BTB domain containing 10 (ZBTB10), an Sp repressor, and these responses were also reversed by antioxidants. Thus, the anticancer activity of CDDO-Me is due, in part, to activation of ROS, which in turn targets the microRNA-27a:ZBTB10-Sp transcription factor axis. This results in decreased expression of Sp-regulated genes, growth inhibition, induction of apoptosis, and antiangiogenic responses.

Drugs that target specificity proteins downregulate epidermal growth factor receptor in bladder cancer cells

The epidermal growth factor receptor (EGFR) is an important chemotherapeutic target for tyrosine kinase inhibitors and antibodies that block the extracellular domain of EGFR. Betulinic acid (BA) and curcumin inhibited bladder cancer cell growth and downregulated specificity protein (Sp) transcription factors, and this was accompanied by decreased expression of EGFR mRNA and protein levels. EGFR, a putative Sp-regulated gene, was also decreased in cells transfected with a cocktail (iSp) containing small inhibitory RNAs for Sp1, Sp3, and Sp4, and RNA interference with individual Sp knockdown indicated that EGFR expression was primarily regulated by Sp1 and Sp3. BA, curcumin, and iSp also decreased phosphorylation of Akt in these cells, and downregulation of EGFR by BA, curcumin, and iSp was accompanied by induction of LC3 and autophagy, which is consistent with recent studies showing that EGFR suppresses autophagic cell death. The results show that EGFR is an Sp-regulated gene in bladder cancer, and drugs such as BA and curcumin that repress Sp proteins also ablate EGFR expression. Thus, compounds such as curcumin and BA that downregulate Sp transcription factors represent a novel class of anticancer drugs that target EGFR in bladder cancer cells and tumors by inhibiting receptor expression.