JMJD2A-dependent silencing of Sp1 in advanced breast cancer promotes metastasis by downregulation of DIRAS3

The emerging roles of lysine-specific demethylase 4A in cancer: Implications in tumorigenesis and therapeutic opportunities

Lysine-specific demethylase 4 A (KDM4A, also named JMJD2A, KIA0677, or JHDM3A) is a demethylase that can remove methyl groups from histones H3K9me2/3, H3K36me2/3, and H1.4K26me2/me3. Accumulating evidence suggests that KDM4A is not only involved in body homeostasis (such as cell proliferation, migration and differentiation, and tissue development) but also associated with multiple human diseases, especially cancers. Recently, an increasing number of studies have shown that pharmacological inhibition of KDM4A significantly attenuates tumor progression in vitro and in vivo in a range of solid tumors and acute myeloid leukemia. Although there are several reviews on the roles of the KDM4 subfamily in cancer development and therapy, all of them only briefly introduce the roles of KDM4A in cancer without systematically summarizing the specific mechanisms of KDM4A in various physiological and pathological processes, especially in tumorigenesis, which greatly limits advances in the understanding of the roles of KDM4A in a variety of cancers, discovering targeted selective KDM4A inhibitors, and exploring the adaptive profiles of KDM4A antagonists. Herein, we present the structure and functions of KDM4A, simply outline the functions of KDM4A in homeostasis and non-cancer diseases, summarize the role of KDM4A and its distinct target genes in the development of a variety of cancers, systematically classify KDM4A inhibitors, summarize the difficulties encountered in the research of KDM4A and the discovery of related drugs, and provide the corresponding solutions, which would contribute to understanding the recent research trends on KDM4A and advancing the progression of KDM4A as a drug target in cancer therapy.

In-silico guided chemical exploration of KDM4A fragments hits

BACKGROUND

Lysine demethylase enzymes (KDMs) are an emerging class of therapeutic targets, that catalyse the removal of methyl marks from histone lysine residues regulating chromatin structure and gene expression. KDM4A isoform plays an important role in the epigenetic dysregulation in various cancers and is linked to aggressive disease and poor clinical outcomes. Despite several efforts, the KDM4 family lacks successful specific molecular inhibitors.

RESULTS

Herein, starting from a structure-based fragments virtual screening campaign we developed a synergic framework as a guide to rationally design efficient KDM4A inhibitors. Commercial libraries were used to create a fragments collection and perform a virtual screening campaign combining docking and pharmacophore approaches. The most promising compounds were tested in-vitro by a Homogeneous Time-Resolved Fluorescence-based assay developed for identifying selective substrate-competitive inhibitors by means of inhibition of H3K9me3 peptide demethylation. 2-(methylcarbamoyl)isonicotinic acid was identified as a preliminary active fragment, displaying inhibition of KDM4A enzymatic activity. Its chemical exploration was deeply investigated by computational and experimental approaches which allowed a rational fragment growing process. The in-silico studies guided the development of derivatives designed as expansion of the primary fragment hit and provided further knowledge on the structure-activity relationship.

CONCLUSIONS

Our study describes useful insights into key ligand-KDM4A protein interaction and provides structural features for the development of successful selective KDM4A inhibitors.

Specificity Proteins (Sp) and Cancer

The specificity protein (Sp) transcription factors (TFs) Sp1, Sp2, Sp3 and Sp4 exhibit structural and functional similarities in cancer cells and extensive studies of Sp1 show that it is a negative prognostic factor for patients with multiple tumor types. In this review, the role of Sp1, Sp3 and Sp4 in the development of cancer and their regulation of pro-oncogenic factors and pathways is reviewed. In addition, interactions with non-coding RNAs and the development of agents that target Sp transcription factors are also discussed. Studies on normal cell transformation into cancer cell lines show that this transformation process is accompanied by increased levels of Sp1 in most cell models, and in the transformation of muscle cells into rhabdomyosarcoma, both Sp1 and Sp3, but not Sp4, are increased. The pro-oncogenic functions of Sp1, Sp3 and Sp4 in cancer cell lines were studied in knockdown studies where silencing of each individual Sp TF decreased cancer growth, invasion and induced apoptosis. Silencing of an individual Sp TF was not compensated for by the other two and it was concluded that Sp1, Sp3 and Sp4 are examples of non-oncogene addicted genes. This conclusion was strengthened by the results of Sp TF interactions with non-coding microRNAs and long non-coding RNAs where Sp1 contributed to pro-oncogenic functions of Sp/non-coding RNAs. There are now many examples of anticancer agents and pharmaceuticals that induce downregulation/degradation of Sp1, Sp3 and Sp4, yet clinical applications of drugs specifically targeting Sp TFs are not being used. The application of agents targeting Sp TFs in combination therapies should be considered for their potential to enhance treatment efficacy and decrease toxic side effects.

Current progress in bionanomaterials to modulate the epigenome

Recent advances in genomics during the 1990s have made it possible to study and identify genetic and epigenetic responses of cells and tissues to various drugs and environmental factors. This has accelerated the number of targets available to treat a range of diseases from cancer to wound healing disorders. Equally interesting is the understanding of how bio- and nanomaterials alter gene expression through epigenetic mechanisms, and whether they have the potential to elicit a positive therapeutic response without requiring additional biomolecule delivery. In fact, from a cell's perspective, a biomaterial is nothing more than an environmental factor, and so it has the power to epigenetically modulate gene expression of cells in contact with it. Understanding these epigenetic interactions between biomaterials and cells will open new avenues in the development of technologies that can not only provide biological signals (i.e. drugs, growth factors) necessary for therapy and regeneration, but also intimately interact with cells to promote the expression of genes of interest. This review article aims to summarise the current state-of-the-art and progress on the development of bio- and nanomaterials to modulate the epigenome.

GTP-binding protein Di-RAS3 diminishes the migration and invasion of non-small cell lung cancer by inhibiting the RAS/extracellular-regulated kinase pathway

The GTP-binding protein Di-Ras3 (DIRAS3) has been established as a maternally imprinted tumor suppressor gene. Growing evidence has correlated the DIRAS3 gene with tumor progression, but its role in non-small cell lung cancer (NSCLC) is rarely reported. Accordingly, the current study sought to evaluate the role and mechanism of DIRAS3 in NSCLC cell progression. First, we uncovered that DIRAS3 was poorly expressed in NSCLC tissues and cells. Subsequently, we examined the effect of DIRAS3 over-expression or knockdown in different lung cancer cells on their malignant phenotypes, with the help of transwell cell migration and invasion assays, and Western blot analyses. It was found that the over-expression of DIRAS3 inhibited the migration and invasion of A549 cells or H520 cells, whereas knockdown of DIRAS3 led to opposing trends. In addition, over-expression of DIRAS3 attenuated the tumor growth and reduced the number of lung tumor nodules. Mechanistically, DIRAS3 may inhibit the migration and invasion of NSCLC cells by inhibiting the RAS/extracellular-regulated kinase (ERK) signaling pathway. Collectively, our findings indicate that DIRAS3 could serve as a potential therapeutic target biomarker for NSCLC.

KDM4 Involvement in Breast Cancer and Possible Therapeutic Approaches

Breast cancer (BC) is the second leading cause of cancer death in women, although recent scientific and technological achievements have led to significant improvements in progression-free disease and overall survival of patients. Genetic mutations and epigenetic modifications play a critical role in deregulating gene expression, leading to uncontrolled cell proliferation and cancer progression. Aberrant histone modifications are one of the most frequent epigenetic mechanisms occurring in cancer. In particular, methylation and demethylation of specific lysine residues alter gene accessibility via histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs). The KDM family includes more than 30 members, grouped into six subfamilies and two classes based on their sequency homology and catalytic mechanisms, respectively. Specifically, the KDM4 gene family comprises six members, KDM4A-F, which are associated with oncogene activation, tumor suppressor silencing, alteration of hormone receptor downstream signaling, and chromosomal instability. Blocking the activity of KDM4 enzymes renders them "druggable" targets with therapeutic effects. Several KDM4 inhibitors have already been identified as anticancer drugs in vitro in BC cells. However, no KDM4 inhibitors have as yet entered clinical trials due to a number of issues, including structural similarities between KDM4 members and conservation of the active domain, which makes the discovery of selective inhibitors challenging. Here, we summarize our current knowledge of the molecular functions of KDM4 members in BC, describe currently available KDM4 inhibitors, and discuss their potential use in BC therapy.

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.

Loss of polarity protein Par3 is mediated by transcription factor Sp1 in breast cancer

Loss of polarity protein Par3 promotes breast cancer tumorigenesis and metastasis. The underlying molecular mechanisms of Par3 down-regulation and related prognostic significance in breast cancer remain unclear. Here, we discovered that Par3 down-regulation was associated with shorter relapse-free survival in Luminal A subtype of breast cancer. Par3 knockdown promoted breast cancer cells migration and invasion. Importantly, we identified that transcription factor Sp1 bound to PARD3 promoter region and induced Par3 expression. Breast cancer patients with low Sp1 showed significantly worse RFS and low expression level of Par3. Par3 over-expression partially reversed Sp1 knockdown induced migration and invasion. Together, decreased Sp1 level mediates Par3 down-regulation, which correlated with poor prognosis of ER + breast cancer patients, via reduced binding with PARD3 promoter.

SP1 Expression and the Clinicopathological Features of Tumors: A Meta-Analysis and Bioinformatics Analysis

Objective: Specificity protein 1 (SP1) plays a vital role to promote carcinogenesis in a variety of tumors, and its up-regulated expression is reported to be a hinter of poor prognosis of patients. We conducted this meta-analysis to elucidate the clinical significance and prognostic value of SP1 in malignant tumors. Methods: PubMed and Cochrane Library were searched for studies published between January 1, 2000 and June 1, 2020. The combined odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (95% CIs) were used to investigate the correlation of SP1 with clinical behaviors and prognosis in patients with solid tumors. UALCAN was used to conduct bioinformatics analysis. Results: A total of 24 documents involving 2,739 patients were enrolled in our review. The random-effect model was used to perform this analysis due to the high level of heterogeneity. SP1 low expression was not conducive to lymph node metastasis (OR = 0.42; 95% CI: 0.28-0.64; p < 0.05), progression of TNM stage (OR = 0.34; 95% CI: 0.20-0.57; p < 0.05) and tumor infiltration (OR = 0.33; 95% CI: 0.18-0.60; p < 0.05). Elevated SP1 expression was connected with shorter survival time of patients with hepatocellular carcinoma, pancreatic cancer, gastric cancer and esophageal cancer (HR = 1.95; 95% CI: 1.16-3.28; p < 0.05). According to UALCAN database, breast cancer, ovarian cancer, colon cancer and lung adenocarcinoma display an elevated SP1 expression in comparison with normal tissues. Kaplan-Meier survival plots indicate SP1 mRNA level has negative effects on prognosis of liver hepatocellular carcinoma and brain lower grade glioma. Conclusion: SP1 was associated with lymph node metastasis, TNM stage and depth of invasion, and indicated poor clinical outcome, which brought new insights on the potential candidacy of SP1 in clinical usage.

TIMELESS regulates sphingolipid metabolism and tumor cell growth through Sp1/ACER2/S1P axis in ER-positive breast cancer

Breast cancer is one of the most common female malignant cancers. Biorhythm disorder largely increases the risk of breast cancer. We aimed to investigate the biological functions and molecular mechanisms of circadian gene TIMELESS circadian regulator (TIM) in estrogen receptor (ER)-positive breast cancer and provide a new therapeutic target for breast cancer patients. Here, we explored that the expression of TIM was elevated in breast cancer, and high expression of TIM in cancer tissues was associated with poor prognosis, especially in the ER-positive breast cancer patients. In addition, we found that TIM promoted cell proliferation and enhanced mitochondrial respiration. TIM interacted with specificity protein 1 (Sp1) which contributes to upregulate the expression of alkaline ceramidase 2 (ACER2). Moreover, ACER2 is responsible for TIM-mediated promotive effects of cell growth and mitochondrial respiration. Collectively, our research unveiled a novel function of TIM in sphingolipid metabolism through interaction with Sp1. It provides a new theoretical explanation for the pathogenesis of breast cancer, and targeting TIM may serve as a potential therapeutic target for ER-positive breast cancer.

H19, a Long Non-coding RNA, Mediates Transcription Factors and Target Genes through Interference of MicroRNAs in Pan-Cancer

Long non-coding RNAs (lncRNAs) have recently been found to be important in gene regulation. lncRNA H19 has been reported to play an oncogenic role in many human cancers. Its specific regulatory role is still elusive. In this study, we developed a novel analytic approach by integrating the synergistic regulation among lncRNAs (e.g., H19), transcription factors (TFs), target genes, and microRNAs (miRNAs) and then applied it to the pan-cancer expression datasets from The Cancer Genome Atlas (TCGA). Using linear regression models, we identified 88 H19-TF-gene co-regulatory triplets, in which 93% of the TF-gene pairs were related to cancer, indicating that our approach was effective to identify disease-related lncRNA-TF-gene co-regulation mechanisms. lncRNAs can function as miRNA sponges. Our further experiments found that H19 might regulate SP1-TGFBR2 through let-7b and miR-200b, ETS1-TGFBR2 through miR-29a and miR-200b, and STAT3-KLF11 through miR-17 in breast cancer cell lines. Our work suggests that miRNA-mediated lncRNA-TF-gene co-regulation is complicated yet important in cancer.

Identification of lncRNA-associated ceRNA network in high-grade serous ovarian cancer metastasis

Aim: To uncover a novel lncRNA-miRNA-mRNA network associated with high-grade serous ovarian cancer metastasis. Material & methods: The candidate differentially expressed lncRNAs were obtained from RNA-sequencing data and determined by functional experiments. The downstream miRNAs and mRNAs were identified by bioinformatic prediction and subjected to functional enrichment analysis. Results: The expression levels of lncRNA ENTPD1-AS1/PRANCR/NR2F2-AS1 were reduced in omental metastatic tissues. Similar differential expression patterns of these lncRNAs were also found in lnCAR database and we verified their tumor suppressive roles by performing functional experiments. Furthermore, we predicted miRNAs and mRNAs via bioinformatic tools and validated their alteration in expression levels in presence of lncRNA interference. Conclusion: We proposed a potential ceRNA regulatory mechanism in high-grade serous ovarian cancer omental metastasis.

Pharmacological Inhibition of Necroptosis Promotes Human Breast Cancer Cell Proliferation and Metastasis

BACKGROUND

Breast cancer remains a great threat to females worldwide. As a recently defined programmed cell death pathway that associates with immune activation, RIP1/RIP3/MLKL necroptosis signaling has been implicated in a variety of diseases. The present study aimed to investigate the role of RIP1/RIP3/MLKL signaling in breast cancer cell proliferation and metastasis in vivo and in vitro.

METHODS

Western blot and quantitative real-time PCR were performed to evaluate the activation of necroptosis signaling in clinical human breast cancer tissues. Correlation of necroptosis signaling markers with clinicopathological parameters was statistically assessed. Cell viability assay, colony formation assay, wound healing assay, and transwell migration and invasion assays were performed to investigate the effects of necroptosis inhibition on breast cancer cell proliferation and metastasis.

RESULTS

Clinical breast cancer tissues showed significantly higher levels of tumor necrosis factor alpha (TNFα), RIP1, RIP3 and MLKL at both mRNA and protein levels as compared with their paired non-cancerous tissues. Phosphorylation of RIP3 and MLKL was also remarkably provoked. Statistics showed that both RIP1 and MLKL positively correlated with cancer parameters such as N-cadherin (p=0.002 for RIP1 and p=0.021 for MLKL) and Ki67 (p=0.031 for RIP1 and p=0.05 for MLKL). The MLKL expression level significantly correlated with tumor size (p=0.001) and the proliferation indicator Ki67 (p=0.018). In addition, pharmacological inhibition of the necroptosis signaling using necrostatin-1 promoted breast cancer cell proliferation and colony formation by approximately 50%. Blockade of necroptosis signaling also accelerated wound healing process and cell transmigration in breast cancer cells.

CONCLUSION

Our results suggested that pharmacological inhibition of necroptosis promoted breast cancer cell proliferation and metastasis. Modulation of tumor cell necroptosis might represent a novel strategy as to breast cancer treatment.

Advances in histone demethylase KDM4 as cancer therapeutic targets

The KDM4 subfamily H3K9 histone demethylases are epigenetic regulators that control chromatin structure and gene expression by demethylating histone H3K9, H3K36, and H1.4K26. The KDM4 subfamily mainly consists of four proteins (KDM4A-D), all harboring the Jumonji C domain (JmjC) but with differential substrate specificities. KDM4A-C proteins also possess the double PHD and Tudor domains, whereas KDM4D lacks these domains. KDM4 proteins are overexpressed or deregulated in multiple cancers, cardiovascular diseases, and mental retardation and are thus potential therapeutic targets. Despite extensive efforts, however, there are very few KDM4-selective inhibitors. Defining the exact physiological and oncogenic functions of KDM4 demethylase will provide the foundation for the discovery of novel potent inhibitors. In this review, we focus on recent studies highlighting the oncogenic functions of KDM4s and the interplay between KDM4-mediated epigenetic and metabolic pathways in cancer. We also review currently available KDM4 inhibitors and discuss their potential as therapeutic agents for cancer treatment.

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

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

Long noncoding RNA RUSC1‑AS‑N promotes cell proliferation and metastasis through Wnt/β‑catenin signaling in human breast cancer

Breast cancer is one of the most frequently diagnosed cancers among females worldwide. Long noncoding RNAs (lncRNAs) have been revealed to serve significant roles in diagnosis and treatment of breast cancer. In the present study, the novel lncRNA RUSC1-AS-N was demonstrated to promote cell viability and metastasis. A total of 100 patients with breast cancer were recruited for this study and it was revealed that RUSC1-AS-N was upregulated in tumor tissues compared with in adjacent non-cancerous counterparts. In addition, using several breast cancer cell lines, it was demonstrated that the mRNA levels of RUSC1-AS-N were highest in the notably metastatic cell lines MDA-MB-231 and MDA-MB-468. Knockdown of RUSC1-AS-N in breast cancer cells inhibited cell proliferation in the colony formation and cell proliferation assays. Furthermore, depletion of RUSC1-AS-N suppressed cell metastasis, as revealed by wound-healing and western blot assays. In addition, the protein levels of Wnt1 and β-catenin were significantly decreased when RUSC1-AS-N was knocked down. However, Wnt signaling pathway activator Wnt agonist 1 reversed the effects of RUSC1-AS-N knockdown on cell proliferation and metastasis. The present study demonstrated that lncRNA RUSC1-AS-N promoted cell viability and metastasis via Wnt/β-catenin signaling in human breast cancer, which may indicate novel targets for the treatment of breast cancer in clinic.

A network of epigenomic and transcriptional cooperation encompassing an epigenomic master regulator in cancer

Coordinated experiments focused on transcriptional responses and chromatin states are well-equipped to capture different epigenomic and transcriptomic levels governing the circuitry of a regulatory network. We propose a workflow for the genome-wide identification of epigenomic and transcriptional cooperation to elucidate transcriptional networks in cancer. Gene promoter annotation in combination with network analysis and sequence-resolution of enriched transcriptional motifs in epigenomic data reveals transcription factor families that act synergistically with epigenomic master regulators. By investigating complementary omics levels, a close teamwork of the transcriptional and epigenomic machinery was discovered. The discovered network is tightly connected and surrounds the histone lysine demethylase KDM3A, basic helix-loop-helix factors MYC, HIF1A, and SREBF1, as well as differentiation factors AP1, MYOD1, SP1, MEIS1, ZEB1, and ELK1. In such a cooperative network, one component opens the chromatin, another one recognizes gene-specific DNA motifs, others scaffold between histones, cofactors, and the transcriptional complex. In cancer, due to the ability to team up with transcription factors, epigenetic factors concert mitogenic and metabolic gene networks, claiming the role of a cancer master regulators or epioncogenes. Significantly, specific histone modification patterns are commonly associated with open or closed chromatin states, and are linked to distinct biological outcomes by transcriptional activation or repression. Disruption of patterns of histone modifications is associated with the loss of proliferative control and cancer. There is tremendous therapeutic potential in understanding and targeting histone modification pathways. Thus, investigating cooperation of chromatin remodelers and the transcriptional machinery is not only important for elucidating fundamental mechanisms of chromatin regulation, but also necessary for the design of targeted therapeutics.

Small molecule KDM4s inhibitors as anti-cancer agents

Histone demethylation is a vital process in epigenetic regulation of gene expression. A number of histone demethylases are present to control the methylated states of histone. Among these enzymes, KDM4s are one subfamily of JmjC KDMs and play important roles in both normal and cancer cells. The discovery of KDM4s inhibitors is a potential therapeutic strategy against different diseases including cancer. Here, we summarize the development of KDM4s inhibitors and some related pharmaceutical information to provide an update of recent progress in KDM4s inhibitors.

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.

Estrogen and progesterone promote breast cancer cell proliferation by inducing cyclin G1 expression

Breast cancer is the most common cause of cancer among women in most countries (WHO). Ovarian hormone disorder is thought to be associated with breast tumorigenesis. The present study investigated the effects of estrogen and progesterone administration on cell proliferation and underlying mechanisms in breast cancer MCF-7 cells. It was found that a single administration of estradiol (E2) or progesterone increased MCF-7 cell viability in a dose-dependent manner and promoted cell cycle progression by increasing the percentage of cells in the G2/M phase. A combination of E2 and progesterone led to a stronger effect than single treatment. Moreover, cyclin G1 was up-regulated by E2 and/or progesterone in MCF-7 cells. After knockdown of cyclin G1 in MCF-7 cells using a specific shRNA, estradiol- and progesterone-mediated cell viability and clonogenic ability were significantly limited. Additionally, estradiol- and progesterone-promoted cell accumulation in the G2/M phase was reversed after knockdown of cyclin G1. These data indicated that estrogen and progesterone promoted breast cancer cell proliferation by inducing the expression of cyclin G1. Our data indicated that novel therapeutics against cyclin G1 are promising for the treatment of estrogen- and progesterone-mediated breast cancer progression.

Cantharidin suppressed breast cancer MDA-MB-231 cell growth and migration by inhibiting MAPK signaling pathway

As an active constituent of the beetle Mylabris used in traditional Chinese medicine, cantharidin is a potent and selective inhibitor of protein phosphatase 2A (PP2A) that plays a crucial role in cell cycle progression, apoptosis, and cell fate. The role and possible mechanisms exerted by cantharidin in cell growth and metastasis of breast cancer were investigated in this study. Cantharidin was found to inhibit cell viability and clonogenic potential in a time- and dose-dependent manner. Cell cycle analysis revealed that cell percentage in G2/M phase decreased, whereas cells in S and G1 phases progressively accumulated with the increasing doses of cantharidin treatment. In a xenograft model of breast cancer, cantharidin inhibited tumor growth in a dose-dependent manner. Moreover, high doses of cantharidin treatment inhibited cell migration in wound and healing assay and downregulated protein levels of major matrix metalloproteinases (MMP)-2 and MMP-9. MDA-MB-231 cell migration and invasion were dose-dependently inhibited by cantharidin treatment. Interestingly, the members of the mitogen-activated protein kinase (MAPK) signaling family were less phosphorylated as the cantharidin dose increased. Cantharidin was hypothesized to exert its anticancer effect through the MAPK signaling pathway. The data of this study also highlighted the possibility of using PP2A as a therapeutic target for breast cancer treatment.

SUMO modification of a heterochromatin histone demethylase JMJD2A enables viral gene transactivation and viral replication

Small ubiquitin-like modifier (SUMO) modification of chromatin has profound effects on transcription regulation. By using Kaposi’s sarcoma associated herpesvirus (KSHV) as a model, we recently demonstrated that epigenetic modification of viral chromatin by SUMO-2/3 is involved in regulating gene expression and viral reactivation. However, how this modification orchestrates transcription reprogramming through targeting histone modifying enzymes remains largely unknown. Here we show that JMJD2A, the first identified Jumonji C domain-containing histone demethylase, is the histone demethylase responsible for SUMO-2/3 enrichment on the KSHV genome during viral reactivation. Using in vitro and in vivo SUMOylation assays, we found that JMJD2A is SUMOylated on lysine 471 by KSHV K-bZIP, a viral SUMO-2/3-specific E3 ligase, in a SUMO-interacting motif (SIM)-dependent manner. SUMOylation is required for stabilizing chromatin association and gene transactivation by JMJD2A. These finding suggest that SUMO-2/3 modification plays an essential role in the epigenetic regulatory function of JMJD2A. Consistently, hierarchical clustering analysis of RNA-seq data showed that a SUMO-deficient mutant of JMJD2A was more closely related to JMJD2A knockdown than to wild-type. Our previous report demonstrated that JMJD2A coated and maintained the “ready to activate” status of the viral genome. Consistent with our previous report, a SUMO-deficient mutant of JMJD2A reduced viral gene expression and virion production. Importantly, JMJD2A has been implicated as an oncogene in various cancers by regulating proliferation. We therefore further analyzed the role of SUMO modification of JMJD2A in regulating cell proliferation. Interestingly, the SUMO-deficient mutant of JMJD2A failed to rescue the proliferation defect of JMJD2A knockdown cells. Emerging specific inhibitors of JMJD2A have been generated for evaluation in cancer studies. Our results revealed that SUMO conjugation mediates an epigenetic regulatory function of JMJD2A and suggests that inhibiting JMJD2A SUMOylation may be a novel avenue for anti-cancer therapy.

Epigenetic dysregulation connects genotype to diseases. An understanding of epigenetic regulation holds promise for clinical use. The profound epigenetic changes that occur during the latent-to-lytic switch of the Kaposi’s sarcoma associated herpesvirus (KSHV) life cycle make it an attractive model system for studies of epigenetic regulation. Using this model, our recent work showed that the demethylase JMJD2A and SUMO-2/3 specific modifications of viral and host chromatin are associated with epigenetic regulation of transcription during reactivation. However, how SUMO modification and histone modifying enzymes interface to orchestrate epigenetic regulation remains largely unknown. Here, we demonstrate JMJD2A as an example of a histone demethylase that is SUMO-2/3 modified by the KSHV encoded SUMO E3 ligase, K-bZIP. SUMO modification of JMJD2A is essential for stabilizing its chromatin binding and exerting its transcriptional derepression activity. Emerging evidence has implicated JMJD2A as an oncogene involved in the progression of various human tumors. The essential role of SUMO in regulating the biological function of JMJD2A suggests that SUMOylation of JMJD2A may be one of the potential underlying mechanisms responsible for JMJD2A-mediated oncogenesis. In this regard, inhibition of JMJD2A SUMOylation could be a new strategy for anti-cancer therapy.

Long noncoding RNA linc-ITGB1 promotes cell migration and invasion in human breast cancer

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death in women globally. Its high morbidity and mortality, as well as its elevated tendency to metastasize to other organs, warrant the urgency to find new biomarkers for breast cancer diagnosis and treatment. The specific roles of long noncoding RNA linc-ITGB1 on cell proliferation and metastasis in breast cancer were explored in this study. The expression of linc-ITGB1 was significantly upregulated in both clinical breast cancer tissues and cultured breast cancer cell lines. The linc-ITGB1 knockdown with specific short hairpin RNA (shRNA) decreased cell proliferation and colony formation in vitro. Tumor growth in vivo was also inhibited by linc-ITGB1 depletion. In addition, linc-ITGB1 depletion caused cell accumulation in the G0/G1 phase. Breast cancer cell lines with linc-ITGB1 depletion exhibited decreased migration and invasion abilities compared with the control cells. Furthermore, the linc-ITGB1 knockdown decreased the expression of mesenchymal markers N-cadherin and vimentin while increasing the expression of the epithelial marker E-cadherin. Key cell cycle regulators Cdc25C and Cyclin B1 were also decreased by the linc-ITGB1 knockdown. These data suggest that linc-ITGB1 promotes breast cancer progression by inducing cell cycle arrest and interrupting the epithelial-to-mesenchymal transition process.

Long non-coding RNA TUG1 promotes cell proliferation and metastasis in human breast cancer

BACKGROUND

Long non-coding RNAs (LncRNAs) utilize a wide variety of mechanisms to regulate RNAs or proteins on the transcriptional or post-transcriptional levels. Accumulating studies have identified numerous LncRNAs to exert critical effects on different physiological processes, genetic disorders, and human diseases.

MATERIALS AND METHODS

Both clinical tissues from breast cancer patients and cultured cells were used for the qRT-PCR analysis. Specific siRNAs were included to assess the roles of TUG1 with cell viability assay, transwell assay, and cell apoptosis assay, respectively.

RESULTS

The expression of TUG1 was enhanced in breast cancerous tissues and in highly invasive breast cancer cell lines and was associated with clinical variables, including tumor size, distant metastasis and TNM staging. Knockdown of TUG1 significantly slowed down cell proliferation, cell migration, and invasion in breast cancer cell lines MDA-MB-231 and MDA-MB-436. In addition, cell apoptotic rate was shown to increase upon siTUG1 treatment as evidenced by increases of the activities of caspase-3 and caspase-9.

CONCLUSION

The identification of TUG1 as a critical mediator of breast cancer progression implied that it might serve as a biomarker for the diagnosis and treatment of breast cancer in clinic.

Identification and characterization of PKF118-310 as a KDM4A inhibitor

Epigenetic modifications are functionally involved in gene expression regulation. In particular, histone posttranslational modifications play a crucial role in functional chromatin organization. Several drugs able to inhibit or stimulate some families of proteins involved in epigenetic histone regulation have been found, a number of which are FDA-approved for the treatment of cutaneous T-cell lymphoma or are in phase I/II/III clinical trials for solid tumors. Although some protein families, such as histone deacetylases and their inhibitors, are well characterized, our understanding of histone lysine demethylases is still incomplete. We describe the in silico, in vitro, and cell-based characterization of the compound PKF118-310, an antagonist of transcription factor 4 (TCF4)/β-catenin signaling, as inhibitor of KDM4A. PKF118-310 potential inhibitor activity was discovered via virtual screening on the crystal structure of KDM4A. A peptide-based histone trimethylation assay developed in-house confirmed its potent KDM4A inhibitor activity. Its protein target was identified by cellular thermal shift assay experiments. PKF118-310 anticancer activity was observed in both liquid and solid tumor cells, and shown to have a dose- and time-dependent effect. We demonstrate the previously unreported inhibitory action of PKF118-310 on KDM4A. Our findings open up the possibility of developing the first KDM4A-specific inhibitors and derivatives.

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.

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

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

Activation of AKR1C1/ERβ induces apoptosis by downregulation of c-FLIP in prostate cancer cells: A prospective therapeutic opportunity

We provide first-time evidence for ERβ-mediated transcriptional upregulation of c-FLIP as an underlying mechanism in the development of castrate-resistant cancer. While androgens inhibit apoptosis partly through transcriptional upregulation of the anti-apoptotic protein, c-FLIP in androgen-responsive cells, they downregulate c-FLIP in androgen-independent cells. We found that although Sp1 and p65 trans-activate c-FLIP, the combination of Sp1 and p65 has differential effects in a cellular context-dependent manner. We show that activation of the androgen metabolism enzyme, aldo-keto reductase, AKR1C1, relieves androgen independence through activation of 3β-Adiol-mediated upregulation of ERβ. ERβ competes with Sp1 and Sp3 to transcriptionally downregulate c-FLIP in the absence of consensus estrogen-response element in androgen-independent cells. Forced expression of AR in androgen-independent cells show that ERβ-mediated growth inhibition occurs under conditions of androgen independence. Reactivation of ERβ with the estrogenic metabolite, 2-methoxyestradiol, decreased enrichment ratio of Sp1/Sp3 at the c-FLIP promoter with concomitant effects on cell growth and death. Expression of Sp1 and c-FLIP are elevated while AKR1C1, ERβ and Sp3 are significantly low in human prostate tumor samples. ERβ is epigenetically silenced in prostate cancer patients, therefore our results suggest that combination of ERβ agonists with ADT would benefit men stratified on the basis of high estrogen levels.