Sp1 Protein Research Articles

Magnolol Inhibits High Fructose-Induced Podocyte Inflammation via Downregulation of TKFC/Sp1/HDAC4/Notch1 Activation.

High fructose has been implicated as an important trigger of kidney inflammation in patients and experimental models. Magnolol, isolated from Magnolia officinalis, has an anti-inflammatory effect, but its protective role in podocytes remains underexplored. This study explored the protective effects and underlying mechanism of magnolol against high fructose-induced podocyte inflammation. The effects of magnolol on high fructose-induced podocyte inflammation were assessed in male Sprague Dawley rats administered 10% (w/v) fructose water for 12 weeks and heat-sensitive human podocyte cell lines (HPCs) exposed to 5 mM fructose. Podocyte foot processes were examined using transmission electron microscopy. The expression levels of nephrin, podocin, tumor necrosis factor-α (TNF-α), Notch1 intracellular domain (NICD1), triokinase/FMN cyclase (TKFC), specificity protein 1 (Sp1) and histone deacetylase 4 (HDAC4) were determined by Western blot, immunofluorescence and real-time quantitative polymerase chain reaction (qRT-PCR). The chromatin immunoprecipitation (ChIP) assay was performed to evaluate the interaction between Sp1 and the promoter region of HDAC4. Magnolol mitigated the impairment of glomerular filtration function in high fructose-fed rats. Besides, it significantly alleviated the inflammatory responses in glomeruli and HPCs, evidenced by decreased protein levels of TNF-α and NICD1. Increased protein levels of TKFC, Sp1 and HDAC4 were observed in high fructose-stimulated HPCs and rat glomeruli. TMP195, an HDAC4 inhibitor, reduced TNF-α and NICD1 protein levels in high fructose-exposed HPCs. The increased Sp1 was shown to associate with the promoter region of HDAC4, promoting HDAC4 protein expression in high fructose-exposed HPCs. The knockdown of TKFC in HPCs by TKFC siRNA decreased Sp1, HDAC4 and NICD1 protein levels, alleviating podocyte inflammatory response. Furthermore, magnolol inhibited TKFC/Sp1/HDAC4/Notch1 activation in vivo and in vitro. Magnolol attenuated high fructose-induced podocyte inflammation possibly through the suppression of TKFC/Sp1/HDAC4/Notch1 activation, providing new evidence for its potential role in podocyte protection.

Crosstalk between BER and NHEJ in XRCC4-Deficient Cells Depending on hTERT Overexpression.

Targeting DNA repair pathways is an important strategy in anticancer therapy. However, the unrevealed interactions between different DNA repair systems may interfere with the desired therapeutic effect. Among DNA repair systems, BER and NHEJ protect genome integrity through the entire cell cycle. BER is involved in the repair of DNA base lesions and DNA single-strand breaks (SSBs), while NHEJ is responsible for the repair of DNA double-strand breaks (DSBs). Previously, we showed that BER deficiency leads to downregulation of NHEJ gene expression. Here, we studied BER's response to NHEJ deficiency induced by knockdown of NHEJ scaffold protein XRCC4 and compared the knockdown effects in normal (TIG-1) and hTERT-modified cells (NBE1). We investigated the expression of the XRCC1, LIG3, and APE1 genes of BER and LIG4; the Ku70/Ku80 genes of NHEJ at the mRNA and protein levels; as well as p53, Sp1 and PARP1. We found that, in both cell lines, XRCC4 knockdown leads to a decrease in the mRNA levels of both BER and NHEJ genes, though the effect on protein level is not uniform. XRCC4 knockdown caused an increase in p53 and Sp1 proteins, but caused G1/S delay only in normal cells. Despite the increased p53 protein, p21 did not significantly increase in NBE1 cells with overexpressed hTERT, and this correlated with the absence of G1/S delay in these cells. The data highlight the regulatory function of the XRCC4 scaffold protein and imply its connection to a transcriptional regulatory network or mRNA metabolism.

Subcellular localization and function analysis of PINK1 mitron in PD progression: Mitron modulates mitochondrial morphology to regulate neuronal death

Parkinson’s disease (PD) is a multi-factorial neurodegenerative disorder. Loss or degeneration of the dopaminergic neurons in the substantia nigra and development of Lewy Bodies in dopaminergic neurons were the defining pathologic changes. MiRNAs fine-tune the protein levels by post-transcriptional gene regulation. MiR-7019-3p is encoded within the 5th intron of PD associated protein PINK1. In present study, we firstly demonstrated miR-7019-3p expression is significantly up regulated in PD mice model and neuron cell models, miR-7019-3p mainly existed in mitochondria, miR-7019-3p could regulate the structure and function of mitochondria in neuronal cells. We predicted and verified that mitochondria associated protein OPA1 and 12s rRNA, 16s rRNA and polycistronic RNA are target genes of miR-7019-3p. Finally, we proved that SP1 protein could independently regulate the expression of miR-7019-3p at the upstream. The evidences in the study suggest the role miR-7019-3p in the regulation of mitochondrial structure and function, and this kind of regulation could be implemented or promoted through the pathway of SP1-miR-7019-3p-OPA1/12s rRNA, 16s rRNA and polycistronic RNA.Our results have suggested a promising and potential therapeutic target for reversing mitochondria dysregulation in neuronal cells during Parkinson's disease process.

OTU deubiquitinase, ubiquitin aldehyde binding 2 (OTUB2) modulates the stemness feature, chemoresistance, and epithelial-mesenchymal transition of colon cancer via regulating GINS complex subunit 1 (GINS1) expression

BackgroundColon cancer is one of the most prevalent tumors in the digestive tract, and its stemness feature significantly contribute to chemoresistance, promote the epithelial-mesenchymal transition (EMT) process, and ultimately lead to tumor metastasis. Therefore, it is imperative for researchers to elucidate the molecular mechanisms underlying the enhancement of stemness feature, chemoresistance, and EMT in colon cancer.MethodsSphere-formation and western blotting assays were conducted to assess the stemness feature. Edu, flow cytometry, and cell viability assays were employed to evaluate the chemoresistance. Immunofluorescence and western blotting assays were utilized to detect EMT. Immunoprecipitation, ubiquitination, agarose gel electrophoresis, chromatin immunoprecipitation followed by quantitative PCR (chip-qPCR), and dual luciferase reporter gene assays were employed for mechanistic investigations.ResultsWe demonstrated a markedly higher expression level of OTUB2 in colon cancer tissues compared to adjacent tissues. Furthermore, elevated OTUB2 expression was closely associated with poor prognosis and distant tumor metastasis. Functional experiments revealed that knockdown of OTUB2 attenuated stemness feature of colon cancer, enhanced its sensitivity to oxaliplatin, inhibited its EMT process, ultimately reduced the ability of tumor metastasis. Conversely, overexpression of OTUB2 exerted opposite effects. Mechanistically, we identified OTUB2 as a deubiquitinase for SP1 protein which bound specifically to SP1 protein, thereby inhibiting K48 ubiquitination of SP1 protein. The SP1 protein functioned as a transcription factor for the GINS1, exerting its regulatory effect by binding to the 1822–1830 region of the GINS1 promoter and enhancing its transcriptional activity. Ultimately, alterations in GINS1 expression directly regulated stemness feature, chemosensitivity, and EMT progression in colon cancer.ConclusionCollectively, the OTUB2/SP1/GINS1 axis played a pivotal role in driving stemness feature, chemoresistance, and EMT in colon cancer. These results shed new light on understanding chemoresistance and metastasis mechanisms involved in colon cancer.

Ovatodiolide inhibited hepatocellular carcinoma stemness through SP1/MTDH/STAT3 signaling pathway

Hepatocellular carcinoma (HCC) is characterized with high recurrence and mortality, and the clinical treatments for HCC are very limited. Hepatocellular carcinoma stem cells are the root of HCC progress, recurrence, and multidrug resistance. Ovatodiolide (OVA) is a bioactive diterpenoid served as an inflammatory and immunotherapeutic responses modulator. In this research, we found OVA inhibited HCC stemness through inhibiting MTDH gene transcription. Moreover, we firstly discovered transcription factor SP1 bound to the promoter region of MTDH to transcriptionally regulate MTDH level. Mechanically, we demonstrated OVA decreased SP1 protein stability to transcriptionally inhibit MTDH gene, and inhibited the nuclear translocation of p65, and then diminished IL-6 level to suppress JAK/STAT3 signaling pathway, eventually decreases CD133 level and the stemness of HCC. Furthermore, we demonstrated ACT004, OVA derivative with high metabolic stability towards cytochrome P450 enzymes, showed no genotoxicity and no accumulative or delayed toxicities after long-term administration in rats. And the in vivo efficacy experiments indicated ACT004 inhibited tumor growth of hepatocellular carcinoma. In conclusion, we revealed the mechanism of OVA in regulating HCC stemness, detected the toxicity of OVA derivative and evaluated the in vivo efficacy which lays a foundation for further discovery of anti-HCC stem cell agents and provide a new strategy for the application of OVA in clinical treatment.

Skeletal muscle differentiation induces wide-ranging nucleosome repositioning in muscle gene promoters

In a previous report, we demonstrated that Cbx1, PurB and Sp3 inhibited cardiac muscle differentiation by increasing nucleosome density around cardiac muscle gene promoters. Since cardiac and skeletal muscle express many of the same proteins, we asked if Cbx1, PurB and Sp3 similarly regulated skeletal muscle differentiation. In a C2C12 model of skeletal muscle differentiation, Cbx1 and PurB knockdown increased myotube formation. In contrast, Sp3 knockdown inhibited myotube formation, suggesting that Sp3 played opposing roles in cardiac muscle and skeletal muscle differentiation. Consistent with this finding, Sp3 knockdown also inhibited various muscle-specific genes. The Cbx1, PurB and Sp3 proteins are believed to influence gene-expression in part by altering nucleosome position. Importantly, we developed a statistical approach to determine if changes in nucleosome positioning were significant and applied it to understanding the architecture of muscle-specific genes. Through this novel statistical approach, we found that during myogenic differentiation, skeletal muscle-specific genes undergo a set of unique nucleosome changes which differ significantly from those shown in commonly expressed muscle genes. While Sp3 binding was associated with nucleosome loss, there appeared no correlation with the aforementioned nucleosome changes. In summary, we have identified a novel role for Sp3 in skeletal muscle differentiation and through the application of quantifiable MNase-seq have discovered unique fingerprints of nucleosome changes for various classes of muscle genes during myogenic differentiation.

Abstract 4990: Genotoxic chemotherapy impedes antibody-mediated complement dependent cytotoxicity (CDC), via a Chk1-CD59 axis

Abstract Monoclonal antibodies such as rituximab exert targeted tumor cell lysis via complement dependent cytotoxicity (CDC). These antibodies are often combined with chemotherapy in clinical treatment protocols. However, the impact of chemotherapy on cell-intrinsic pathways that regulate antibody-mediated CDC is not known. Through a phage display screen, we identified that genotoxic stress caused upregulation of a membrane complement regulatory protein (mCRP), CD46, prompting further investigation into its implications and mechanism. Using cell lines from diffuse large B cell lymphoma (DLBCL) as our model, we confirmed that genotoxic chemotherapy upregulates CD46, as well as other mCRPs such as CD55 and CD59. We hypothesized that upregulated mCRPs could impede Rituximab-mediated CDC. We assessed this in-vitro using rituximab and complement human serum. Aligned with our hypothesis, chemotherapy treatment of DLBCL cells significantly impeded rituximab-induced CDC. Using blocking antibodies to each mCRP, reversal of the effect of chemotherapy on CDC only occurred after co-treatment with a CD59 blocking antibody, suggesting that CD59 is a key player for chemotherapy-invoked resistance to CDC. To further elucidate the underlying cellular pathway, we performed a high-throughput small molecule screen using rituximab-induced CDC as a readout, with or without cotreatment of a genotoxic chemotherapeutic (etoposide). We identified Chk1 inhibitors as consistent top rescuers. qPCR and flow cytometry revealed that Chk1 inhibition prevented the upregulation of mCRPs transcriptionally. Sp1 is a known transcription factor driving constitutive CD59 expression. Inhibiting Sp1 similarly prevented chemotherapy-induced upregulation of CD59 and resistance to CDC. However, CHIP-qPCR showed no increased binding of total Sp1 protein to the CD59 promoter after chemotherapy. Instead, positive co-immunoprecipitation of pATM and p300 with Sp1 only with etoposide and not with co-treatment of Chk1 inhibitor suggests Chk1-mediated activation of Sp1. Mechanistically, we have found that chemotherapy-activated Chk1 modulates Sp1-mediated CD59 transcription and that the induced upregulation of CD59 is able to prevent antibody-mediated CDC. Overall, these results indicate novel immune regulation by DNA damage response, particularly in the context of complement regulatory proteins. Our results advocate consideration when using simultaneous administration of chemotherapy with CDC-inducing monoclonal antibodies, and suggest Chk1 blockade as a possible therapeutic addition. Citation Format: Allison S. Chan, Patrick W. Jaynes, Nurulhuda B. Mustafa, Akshaya A. Anbuselvan, Charmaine Z. Ong, Anand D. Jeyasekharan. Genotoxic chemotherapy impedes antibody-mediated complement dependent cytotoxicity (CDC), via a Chk1-CD59 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4990.

Abstract 2345: Docking and molecular dynamic simulations of mithramycin against Sp1, Sp3, and survivin

Abstract Purpose: Therapeutic targeting of transcription factors, Specificity protein (Sp)1 and Sp3 and their downstream effectors, such as survivin, are studied in various cancers. Due to role in in poorer cancer prognoses in several cancers their downregulation has been investigated as an effective treatment approach. Mithramycin (Mit) showed innate anti-cancer properties by targeting Sp proteins through GC/GT DNA binding interference. Recent studies have given new insights into further mechanisms of action of Mit, however in-depth binding and mechanistic studies are lacking. Our objective is to investigate Mit’s specific binding interactions with Sp1, Sp3, and survivin. Methods: Protein structures and sequences for Sp1, Sp3, and survivin (ID: P08047, Q02447, and O153392, respectively) were retrieved from UniProtKB database. Experimental predicted structures for Sp1 and Sp3 were obtained from AlphaFold. Sequence lengths of Sp1 and Sp3 were 785 and 781 amino acids (aa), domain regions of Sp1 (619-785) and Sp3 (461-781) were note. Survivin structure was obtained from PDB and was comprised of 142 aa. Co-crystallized compounds were removed during analyses using BIOVIA Discovery Studio 4.5 Visualizer. Prediction of binding sites and docking were performed using CASTp, GHECOM, DEPTH tools, glide, and AutoDock 4.2 software. Energy minimization and Molecular dynamics simulations were performed in the Schrödinger suite. Results: Binding sites were identified for Sp1, Sp3, and survivin. Simulated docking demonstrated multiple binding complexes and varying binding energies. The most efficient binding was seen with Sp1 and Sp3. RMSF and RMSD simulations revealed stabilization of Sp1-, Sp3-, and survivin-Mit complexes. This shows Mithramycin can potentially inhibit all three proteins, with slightly more stability with Sp1 and Sp3. Radius of gyration (rGyr), H-bond analysis, and solvent accessible surface area (SASA) support docking findings with Mit-protein complexes remaining stable in the binding pocket, forming new H-bonds, and altering hydrophilic and hydrophobic interaction areas. Conclusion: Our findings warrant further in vitro testing of the ability of Mit to interact with a wider range of oncogenic targets. While we only tested the ability of Mit to interact with Sp1, Sp3 and survivin, similar model can be used to evaluate the interaction with other critical proteins associated with cancer and to further elucidate mechanisms of action. These finding are crucial to understanding base mechanistic abilities and can be useful to test additional agents for their ability to interact with Sp1 or survivin. Citation Format: Christoffer Briggs Lambring, Santosh K. Behera, Riyaz Basha. Docking and molecular dynamic simulations of mithramycin against Sp1, Sp3, and survivin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2345.

Cancer-associated fibroblast-derived acetate promotes pancreatic cancer development by altering polyamine metabolism via the ACSS2–SP1–SAT1 axis

The ability of tumour cells to thrive in harsh microenvironments depends on the utilization of nutrients available in the milieu. Here we show that pancreatic cancer-associated fibroblasts (CAFs) regulate tumour cell metabolism through the secretion of acetate, which can be blocked by silencing ATP citrate lyase (ACLY) in CAFs. We further show that acetyl-CoA synthetase short-chain family member 2 (ACSS2) channels the exogenous acetate to regulate the dynamic cancer epigenome and transcriptome, thereby facilitating cancer cell survival in an acidic microenvironment. Comparative H3K27ac ChIP–seq and RNA–seq analyses revealed alterations in polyamine homeostasis through regulation of SAT1 gene expression and enrichment of the SP1-responsive signature. We identified acetate/ACSS2-mediated acetylation of SP1 at the lysine 19 residue that increased SP1 protein stability and transcriptional activity. Genetic or pharmacologic inhibition of the ACSS2–SP1–SAT1 axis diminished the tumour burden in mouse models. These results reveal that the metabolic flexibility imparted by the stroma-derived acetate enabled cancer cell survival under acidosis via the ACSS2–SP1–SAT1 axis.

RhoGDIβ inhibition via miR-200c/AUF1/SOX2/miR-137 axis contributed to lncRNA MEG3 downregulation-mediated malignant transformation of human bronchial epithelial cells.

Nickel pollution is a recognized factor contributing to lung cancer. Understanding the molecular mechanisms of its carcinogenic effects is crucial for lung cancer prevention and treatment. Our previous research identified the downregulation of a long noncoding RNA, maternally expressed gene 3 (MEG3), as a key factor in transforming human bronchial epithelial cells (HBECs) into malignant cells following nickel exposure. In our study, we found that deletion of MEG3 also reduced the expression of RhoGDIβ. Notably, artificially increasing RhoGDIβ levels counteracted the malignant transformation caused by MEG3 deletion in HBECs. This indicates that the reduction in RhoGDIβ contributes to the transformation of HBECs due to MEG3 deletion. Further exploration revealed that MEG3 downregulation led to enhanced c-Jun activity, which in turn promoted miR-200c transcription. High levels of miR-200c subsequently increased the translation of AUF1 protein, stabilizing SOX2 messenger RNA (mRNA). This stabilization affected the regulation of miR-137, SP-1 protein translation, and the suppression of RhoGDIβ mRNA transcription and protein expression, leading to cell transformation. Our study underscores the co-regulation of RhoGDIβ expression by long noncoding RNAMEG3, multiple microRNAs (miR-200c and miR-137), and RNA-regulated transcription factors (c-Jun, SOX2, and SP1). This intricate network of molecular events sheds light on the nature of lung tumorigenesis. These novel findings pave the way for developing targeted strategies for the prevention and treatment of human lung cancer based on the MEG3/RhoGDIβ pathway.

Effects of Different Light Environments with Varying Spectral Composition on the Axial Lengths and Scleral Specificity Protein 1 and Collagen Type I Expression in Juvenile Guinea Pigs.

The study aimed to investigate changes in the eye axial length in juvenile guinea pigs and the expression of scleral specificity protein 1 (Sp1) and collagen type I (Col-I) under different light environments with varying spectral composition. The animals were randomly divided into five groups: natural light (N), LED light with a low colour temperature (L), E light (E), Fulia light (F), and Gulia light (G). Axial lengths were measured every two weeks, and the expression of Sp1 and Col-I in the sclera was assessed by immunohistochemistry, Western blot and RT-qPCR. After 4, 6, 8, 10, and 12 weeks of light exposure, the L and G groups showed considerably longer axial lengths than the N group, with the L group exhibiting significantly longer axial lengths compared with the E and F groups. The protein and mRNA expression levels of Sp1 and Col-I, ranked from highest to lowest, were as follows: N, E, F, G, and L. The expression of Sp1 and Col-I was positively correlated, but both were negatively correlated with the length of the eye axis. The E group demonstrated higher Sp1 and Col-I expression than the other artificial light groups. Artificial light with a continuous, full spectrum lacking peaks and valleys can inhibit the elongation of the eye axis in juvenile guinea pigs and has a protective effect against myopia. There may be a certain relationship between Sp1 and Col-I, and the transforming growth factor-β1-Sp1-Col-I signalling pathway may play a crucial role in myopic scleral extracellular matrix remodelling.

Identification of an Allele-Specific Transcription Factor Binding Interaction that May Regulate PLA2G2A Gene Expression.

The secreted phospholipase A2 (sPLA2) isoform, sPLA2-IIA, has been implicated in a variety of diseases and conditions, including bacteremia, cardiovascular disease, COVID-19, sepsis, adult respiratory distress syndrome, and certain cancers. Given its significant role in these conditions, understanding the regulatory mechanisms impacting its levels is crucial. Genome-wide association studies (GWAS) have identified several single nucleotide polymorphisms (SNPs), including rs11573156, that are associated with circulating levels of sPLA2-IIA. The work in the manuscript leveraged 4 publicly available datasets to investigate the mechanism by which rs11573156 influences sPLA2-IIA levels via bioinformatics and modeling analysis. Through genotype-tissue expression (GTEx), 234 expression quantitative trait loci (eQTLs) were identified for the gene that encodes for sPLA2-IIA, PLA2G2A. SNP2TFBS was used to ascertain the binding affinities between transcription factors (TFs) to both the reference and alternative alleles of identified eQTL SNPs. Subsequently, candidate TF-SNP interactions were cross-referenced with the ChIP-seq results in matched tissues from ENCODE. SP1-rs11573156 emerged as the significant TF-SNP pair in the liver. Further analysis revealed that the upregulation of PLA2G2A transcript levels through the rs11573156 variant was likely affected by tissue SP1 protein levels. Using an ordinary differential equation based on Michaelis-Menten kinetic assumptions, we modeled the dependence of PLA2G2A transcription on SP1 protein levels, incorporating the SNP influence. Collectively, our analysis strongly suggests that the difference in the binding dynamics of SP1 to different rs11573156 alleles may underlie the allele-specific PLA2G2A expression in different tissues, a mechanistic model that awaits future direct experimental validation. This mechanism likely contributes to the variation in circulating sPLA2-IIA protein levels in the human population, with implications for a wide range of human diseases.

Ferrostatin-1 improves neurological impairment induced by ischemia/reperfusion injury in the spinal cord through ERK1/2/SP1/GPX4

Spinal cord ischemia/reperfusion injury (SCIRI) induced by artificial aortic occlusion for a while during aortic surgery is a serious complication, leading to paraplegia and even death. Ferroptosis in the nervous system has been confirmed to contribute to neuronal death induced by SCIRI. Therefore, we investigated the therapeutic benefits of ferrostatin-1 (Fer-1, a ferroptosis inhibitor) and explored the mechanism and target of Fer-1 in SCIRI. Our results demonstrate that intrathecal injection of Fer-1 had a strong anti-SCIRI effect, improved ferroptosis-related indices, increased neurological function scores and motor neuron counts, and reduced BSCB leakage and neuroinflammation levels in the anterior horn. We found that SCIRI significantly elevated the levels of several important proteins, including SP1, p-ERK1/2/ERK1/2, COX2, TFR1, SLC40A1, SLC7A11, cleaved Caspase 3, GFAP, and Iba1, while reducing FTH1 and GPX4 protein expression, with no effect on ACSL4 expression. Fer-1 effectively ameliorated the ferroptosis-related changes in these proteins induced by SCIRI. However, for p-ERK1/2 and SP1, Fer-1 not only failed to reduce their expression but also significantly enhanced it. Fer-1 was injected into sham operation rats, abnormal increases in p-ERK1/2/ERK1/2 and SP1 were observed, along with an increase in GPX4. Fluorescent double labeling revealed that SP1 and GPX4 were expressed in neurons and astrocytes. Inhibitors of the ERK pathway (SCH772984) and siRNA against SP1 (AV-sh-SP1) significantly decreased the increase in SP1 and GPX4 protein levels, fluorescent density of SP1 and GPX4 in neurons, and the number of SP1-positive and GPX4-positive neurons induced by Fer-1. SCH772984 but not AV-sh-SP1 significantly reversed the decrease in GFAP and Iba1 induced by Fer-1. In conclusion, our results indicate that Fer-1 inhibited ferroptosis in spinal cord anterior horn neurons, improving neurological impairment and BSCB damage after SCIRI through the ERK1/2/SP1/GPX4 signaling pathway in rats.

Specificity protein 1 (Sp1) and glucocorticoid receptor (GR) stimulate bovine alphaherpesvirus 1 (BoHV-1) replication and cooperatively transactivate the immediate early transcription unit 1 promoter.

Bovine alphaherpesvirus 1 (BoHV-1) infections cause respiratory tract disorders and suppress immune responses, which can culminate in bacterial pneumonia. Following acute infection, BoHV-1 establishes lifelong latency in sensory neurons present in trigeminal ganglia (TG) and unknown cells in pharyngeal tonsil. Latently infected calves consistently reactivate from latency after an intravenous injection of the synthetic corticosteroid dexamethasone (DEX), which mimics the effects of stress. The immediate early transcription unit 1 (IEtu1) promoter drives expression of infected cell protein 0 (bICP0) and bICP4, two key viral transcriptional regulators. The IEtu1 promoter contains two functional glucocorticoid receptor (GR) response elements (GREs), and this promoter is transactivated by GR, DEX, and certain Krüppel transcription factors that interact with GC-rich motifs, including consensus specificity protein 1 (Sp1) binding sites. Based on these observations, we hypothesized that Sp1 stimulates productive infection and transactivates key BoHV-1 promoters. DEX treatment of latently infected calves increased the number of Sp1+ TG neurons and cells in pharyngeal tonsil indicating that Sp1 expression is induced by stress. Silencing Sp1 protein expression with siRNA or mithramycin A, a drug that preferentially binds GC-rich DNA, significantly reduced BoHV-1 replication. Moreover, BoHV-1 infection of permissive cells increased Sp1 steady-state protein levels. In transient transfection studies, GR and Sp1 cooperatively transactivate IEtu1 promoter activity unless both GREs are mutated. Co-immunoprecipitation studies revealed that GR and Sp1 interact in mouse neuroblastoma cells (Neuro-2A) suggesting this interaction stimulates IEtu1 promoter activity. Collectively, these studies suggested that the cellular transcription factor Sp1 enhances productive infection and stress-induced BoHV-1 reactivation from latency.IMPORTANCEFollowing acute infection, bovine alphaherpesvirus 1 (BoHV-1) establishes lifelong latency in sensory neurons in trigeminal ganglia (TG) and pharyngeal tonsil. The synthetic corticosteroid dexamethasone consistently induces BoHV-1 reactivation from latency. The number of TG neurons and cells in pharyngeal tonsil expressing the cellular transcription factor specificity protein 1 (Sp1) protein increases during early stages of dexamethasone-induced reactivation from latency. Silencing Sp1 expression impairs BoHV-1 replication in permissive cells. Interestingly, mithramycin A, a neuroprotective antibiotic that preferentially binds GC-rich DNA, impairs Sp1 functions and reduces BoHV-1 replication suggesting that it is a potential antiviral drug. The glucocorticoid receptor (GR) and Sp1 cooperatively transactivate the BoHV-1 immediate early transcript unit 1 (IEtu1) promoter, which drives expression of infected cell protein 0 (bICP0) and bICP4. Mithramycin A also reduced Sp1- and GR-mediated transactivation of the IEtu1 promoter. These studies revealed that GR and Sp1 trigger viral gene expression and replication following stressful stimuli.

DDDR-14. DEVELOPMENT OF A NOVEL CYP17A1-TARGETED INHIBITOR FOR GLIOBLASTOMA

Abstract Glioblastoma (GBM) is a highly aggressive and invasive brain tumor, resistant to current standard treatments, including temozolomide (TMZ) and radiotherapy. Despite these interventions, GBM's intrinsic drug resistance often renders it incurable, thus highlighting the dire need for novel therapeutic strategies. In this study, we used ultra-high pressure liquid chromatography-mass spectrometry to examine the levels of neurosteroids in tumor specimens from primary and recurrent GBM patients. This led to the discovery of differential expression patterns, most notably in androgen, including dehydroepiandrosterone and testosterone. Our results indicated androgen over-production weakens the GBM's sensitivity to TMZ by inducing post-translational modification of Sp1 protein, which aids in DNA repair. Interestingly, Sp1 activity is further enhanced by histone deacetylase (HDAC) 6, which in turn diminishes the DNA damage caused by TMZ. In addition, proteomic analysis revealed an overexpression of cytochrome (CYP) 17A1, particularly in recurrent GBM, which led us to hypothesize that a drug inhibiting both CYP17A1 and HDAC6 could potentially serve as a viable treatment for TMZ-resistant GBM. To validate this, the drug was tested in vitro on U87MG-R cells and patient-derived Pt#3 TMZ-resistant cells, demonstrating the therapeutic efficacy based on cell viability assays. In vivo testing in the TMZ-resistant GBM orthotopic mouse model also showed promising anti-tumor activity, with treated mice demonstrating increased survival times compared to controls. In conclusion, our findings suggest that this drug targeting both CYP17A1 and HDAC6 presents a potential breakthrough in GBM-targeted therapy, addressing the pervasive issue of TMZ resistance.

Sp1 mediated the inhibitory effect of glutamate on pulmonary surfactant synthesis.

Studies have shown that the release of endogenous glutamate (Glu) participates in lung injury by activating N-methyl-D-aspartate receptor (NMDAR), but the mechanism is still unclear. This study was to investigate the effects and related mechanisms of Glu on the lipid synthesis of pulmonary surfactant (PS) in isolated rat lung tissues. The cultured lung tissues of adult SD rats were treated with Glu. The amount of [3H]-choline incorporation into phosphatidylcholine (PC) was detected. RT-PCR and Western blot were used to detect the changes of mRNA and protein expression of cytidine triphosphate: phosphocholine cytidylyltransferase alpha (CCTα), a key regulatory enzyme in PC biosynthesis. Western blot was used to detect the expression of NMDAR1, which is a functional subunit of NMDAR. Specific protein 1 (Sp1) expression plasmids were used. After transfected with Sp1 expression plasmids, the mRNA and protein levels of CCTα were detected by RT-PCR and Western blot in A549 cells. After treated with NMDA and MK-801, the mRNA and protein levels of Sp1 were detected by RT-PCR and Western blot in A549 cells. Glu decreased the incorporation of [3H]-choline into PC in a concentration- and time- dependent manner. Glu treatment significantly reduced the mRNA and protein levels of CCTα in lungs. Glu treatment up-regulated NMDAR1 protein expression, and the NMDAR blocker MK-801 could partially reverse the reduction of [3H]-choline incorporation induced by Glu (10-4 mol/L) in lungs. After transfected with Sp1 plasmid for 30 h, the mRNA and protein expression levels of CCTα were increased and the protein expression of Sp1 was also up-regulated. After A549 cells were treated with NMDA, the level of Sp1 mRNA did not change significantly, but the expression of nucleus protein in Sp1 was significantly decreased, while the expression of cytoplasmic protein was significantly increased. However, MK-801could reverse these changes. Glu reduced the biosynthesis of the main lipid PC in PS and inhibited CCTα expression by activating NMDAR, which were mediated by the inhibition of the nuclear translocation of Sp1 and the promoter activity of CCTα. In conclusion, NMDAR-mediated Glu toxicity leading to impaired PS synthesis may be a potential pathogenesis of lung injury.

ROS-Sp1 axis is involved in thermochemotherapy-enhanced sensitivity of pancreatic cancer cells to gemcitabine.

Gemcitabine (GEM)-based chemotherapy represents the first choice for locally unresectable advanced pancreatic cancer, while the benefit is limited due to acquired chemoresistance or drug delivery insufficiency. Hyperthermia treatment potentially improves the clinical efficacy of GEM. However, the underlying mechanism is incompletely revealed. Our study aims to investigate the effect and involved mechanism of thermochemotherapy on cell survival. Pancreatic cancer cells PANC-1 and ASPC-1 were either treated with GEM or thermochemotherapy, then cell viability, apoptosis, migration, invasion, reactive oxygen species (ROS) production, and Sp1 expression were evaluated. The results showed that GEM dose and time-dependently affected cell viability, and 30 μM GEM achieved favorable effect in suppressing cancer cell growth. Meanwhile, hyperthermia preconditioning (43°C for 60 min) 24 h before GEM treatment yielded superior effect than other treatment sequence. GEM caused significant cell apoptosis and proapoptotic genes of both cancer cells, and thermochemotherapy further promoted apoptosis and genes transcription, accompanied by excessive ROS production. Thermochemotherapy was superior to GEM in suppressing cell migration and invasion of pancreatic cancer cells. Meanwhile, GEM significantly reduced Sp1 mRNA and protein and its downstream gene Cox-2, and thermochemotherapy further suppressed their expressions. ROS elimination with N-acetyl-l-cysteine notably neutralizes the suppressive effect of GEM and thermochemotherapy on cell growth and expressions of Sp1 and Cox-2. In conclusion, thermochemotherapy inhibited pancreatic cell viability, migration and invasion, and promoted cell apoptosis by inducing excessive ROS production, which subsequently suppressed Sp1 expression and the downstream Cox-2.

The non-cell-autonomous function of ID1 promotes AML progression via ANGPTL7 from the microenvironment

AbstractThe bone marrow microenvironment (BMM) can regulate leukemia stem cells (LSCs) via secreted factors. Increasing evidence suggests that dissecting the mechanisms by which the BMM maintains LSCs may lead to the development of effective therapies for the eradication of leukemia. Inhibitor of DNA binding 1 (ID1), a key transcriptional regulator in LSCs, previously identified by us, controls cytokine production in the BMM, but the role of ID1 in acute myeloid leukemia (AML) BMM remains obscure. Here, we report that ID1 is highly expressed in the BMM of patients with AML, especially in BM mesenchymal stem cells, and that the high expression of ID1 in the AML BMM is induced by BMP6, secreted from AML cells. Knocking out ID1 in mesenchymal cells significantly suppresses the proliferation of cocultured AML cells. Loss of Id1 in the BMM results in impaired AML progression in AML mouse models. Mechanistically, we found that Id1 deficiency significantly reduces SP1 protein levels in mesenchymal cells cocultured with AML cells. Using ID1-interactome analysis, we found that ID1 interacts with RNF4, an E3 ubiquitin ligase, and causes a decrease in SP1 ubiquitination. Disrupting the ID1-RNF4 interaction via truncation in mesenchymal cells significantly reduces SP1 protein levels and delays AML cell proliferation. We identify that the target of Sp1, Angptl7, is the primary differentially expression protein factor in Id1-deficient BM supernatant fluid to regulate AML progression in mice. Our study highlights the critical role of ID1 in the AML BMM and aids the development of therapeutic strategies for AML.

Solamargine enhanced gefitinib antitumor effect via regulating MALAT1/miR-141-3p/Sp1/IGFBP1 signaling pathway in non-small cell lung cancer.

Lung cancer is the leading cause of cancer-related deaths worldwide. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) showed great therapeutic efficacy for non-small cell lung cancer (NSCLC) patients. However, acquired resistance severely limits the clinical application and efficacy of EGFR-TKIs. In the current study, we found that solamargine (SM), a natural alkaloid derived from the fruit of Lycium tomato lobelia, has been found to inhibit the progression of NSCLC and enhance the anticancer effect of EGFR-TKIs. In brief, SM significantly inhibited the cell viability of NSCLC cells and enhanced the anticancer effect of gefitinib (GFTN) and erlotinib (ERL). Mechanistically, SM decreased the expression of MALAT1 and induced miR-141-3p, whereas reduced SP1 protein levels. Interestingly, both MALAT1 and Sp1 have classical and conservative binding sites of miR-141-3p in their 3'-UTR regions. Silence of MALAT1 and overexpression of miR-141-3p both decreased the protein expression of Sp1. Subsequently, promoter activity and protein expression of IGFBP1 were upregulated by SM, which was not observed in cells with SP1 overexpression. Moreover, the inhibitory effect of SM on cell growth was significantly blocked by knockdown of IGFBP1 expression. More importantly, the combination of SM and GFTN synergistically inhibited the progression of lung cancer. Similar results were observed in experiments in vivo. Finally, the clinical relevance of MALAT1, Sp1 and IGFBP1 was further validated using bioinformatics analysis. Taken together, we confirmed that SM significantly enhanced the anticancer effect of EGFR-TKIs by regulating the MALAT1/miR-141-3p/Sp1/IGFBP1 signaling pathway. This study unravels a novel mechanism and suggests a new potential NSCLC-associated therapy.

Abstract 6733: Targeting Sp1 in Ewing sarcoma: a multi-approach method for the utilization of mithramycin

Abstract Purpose: Ewing Sarcoma (ES) is a bone and soft tissue cancer affecting young adults and children. Localized ES presents with a 5-year survival rate of 70%, while metastatic cases range from 15-30%. Our laboratory investigates combination treatments using less toxic agents to induce sensitization to chemotherapy in ES. The anti-cancer activity of an antineoplastic antibiotic, Mithramycin (Mit), against ES cells has been shown. Mit inhibits Specificity protein 1 (Sp1) a marker associated with aggressive cancer cell growth and resistance to chemo/radiation therapies. However, its mechanistic effects on other oncogenic proteins have yet to be elucidated in ES. The purpose of this study is to evaluate the effectiveness of Mit and combination with other chemotherapeutic agents, Etoposide and Vincristine, to inhibit ES cell growth and assess the effect on cancer related proteins regulated by Sp1. Future studies will expand upon Mithramycin's mechanism of action in Ewing Sarcoma utilizing RNA sequencing and computational methods. Methods: Anti-proliferative activity of Mit and/or Vincristine and Etoposide against ES cell lines, TC205 and CHLA10, was evaluated using CellTiterGlo kit. Dose curves and IC50 values were determined by Sigma-Plot software. The expression of Sp1 and survivin was determined by Western blot analysis. Cell lines were obtained from Children’s Oncology Group. The specific type of drug effect of the combination treatments were determined by analyzing the combination index obtained via Calcusyn software. Nude mice were injected with TC-205 cells and treated over two weeks with either Mit (1mg/kg per week) and/or Etoposide (5mg/kg per week) and tumor volume was compared. Protein models were obtained from RCSB PDB and homology tests were performed in the Swiss-model workspace. Results: Mit significantly decreased ES cell line viability and tumor volume in nude mice. Mit showed the ability to reduce the expression of Sp1 and offered differing effects on survivin expression, indicative of anti-apoptotic mechanisms being implemented in the ES cell lines. IC50 values of both chemotherapeutics and Mit were decreased by nearly 50% when used in combination and this effect was mirrored in further decreases in Sp1 expression. Synergistic drug responses were shown in the combination of Mit with both Vincristine and Etoposide. Sp1 and survivin protein models were established and homology verification using Ramachandran plots and QMEAN Z-scores indicated quality protein models for further computational studies. Conclusions: Mit may effectively sensitize ES cells and improve the response of chemotherapy while lowering necessary effective dosages. Studies to understand the mechanism of action of Mit on Sp1, survivin, and other proteins involved in Ewing Sarcomagenesis are underway. This study is partially supported by a grant from the Cancer Prevention and Research Institute of Texas (Award#: RP210046) Citation Format: Christoffer Lambring, Riyaz Basha, Umesh Sankpal. Targeting Sp1 in Ewing sarcoma: a multi-approach method for the utilization of mithramycin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6733.