Down-regulation Of C-myc Expression Research Articles

Unveiling the Mechanism of the ChaiShao Shugan Formula Against Triple-Negative Breast Cancer.

The ChaiShao Shugan Formula (CSSGF) is a traditional Chinese medicine formula with recently identified therapeutic value in triple-negative breast cancer (TNBC). This study aimed to elucidate the underlying mechanism of CSSGF in TNBC treatment. TNBC targets were analyzed using R and data were from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The major ingredients and related protein targets of CSSGF were explored via the Traditional Chinese Medicine Systems Pharmacology database, and an ingredient-target network was constructed via Cytoscape to identify hub genes. The STRING database was used to construct the PPI network. GO and KEGG enrichment analyses were performed via R to obtain the main targets. The online tool Kaplan‒Meier plotter was used to identify the prognostic genes. Molecular docking was applied to the core target genes and active ingredients. MDA-MB-231 and MCF-7 cell lines were used to verify the efficacy of the various drugs. A total of 4562 genes were screened as TNBC target genes. The PPI network consisted of 89 nodes and 845 edges. Our study indicated that quercetin, beta-sitosterol, luteolin and catechin might be the core ingredients of CSSGF, and EGFR and c-Myc might be the latent therapeutic targets of CSSGF in the treatment of TNBC. GO and KEGG analyses indicated that the anticancer effect of CSSGF on TNBC was mainly associated with DNA binding, transcription factor binding, and other biological processes. The related signaling pathways mainly involved the TNF-a, IL-17, and apoptosis pathways. The molecular docking data indicated that quercetin, beta-sitosterol, luteolin, and catechin had high affinity for EGFR, JUN, Caspase-3 and ESR1, respectively. In vitro, we found that CSSGF could suppress the expression of c-Myc or promote the expression of EGFR. In addition, we found that quercetin downregulates c-Myc expression in two BC cell lines. This study revealed the effective ingredients and latent molecular mechanism of action of CSSGF against TNBC and confirmed that quercetin could target c-Myc to induce anti-BC effects.

Super enhancer related gene ANP32B promotes the proliferation of acute myeloid leukemia by enhancing MYC through histone acetylation

BackgroundAcute myeloid leukemia (AML) is a malignancy of the hematopoietic system, and childhood AML accounts for about 20% of pediatric leukemia. ANP32B, an important nuclear protein associated with proliferation, has been found to regulate hematopoiesis and CML leukemogenesis by inhibiting p53 activity. However, recent study suggests that ANP32B exerts a suppressive effect on B-cell acute lymphoblastic leukemia (ALL) in mice by activating PU.1. Nevertheless, the precise underlying mechanism of ANP32B in AML remains elusive.ResultsSuper enhancer related gene ANP32B was significantly upregulated in AML patients. The expression of ANP32B exhibited a negative correlation with overall survival. Knocking down ANP32B suppressed the proliferation of AML cell lines MV4-11 and Kasumi-1, along with downregulation of C-MYC expression. Additionally, it led to a significant decrease in H3K27ac levels in AML cell lines. In vivo experiments further demonstrated that ANP32B knockdown effectively inhibited tumor growth.ConclusionsANP32B plays a significant role in promoting tumor proliferation in AML. The downregulation of ANP32B induces cell cycle arrest and promotes apoptosis in AML cell lines. Mechanistic analysis suggests that ANP32B may epigenetically regulate the expression of MYC through histone H3K27 acetylation. ANP32B could serve as a prognostic biomarker and potential therapeutic target for AML patients.

Distinguishing G-Quadruplexes Stabilizer and Chaperone for c-MYC Promoter G-Quadruplexes through Single-Molecule Manipulation.

G-quadruplex (G4) selective stabilizing ligands can regulate c-MYC gene expression, but the kinetic basis remains unclear. Determining the effects of ligands on c-MYC promoter G4s' folding/unfolding kinetics is challenging due to the polymorphic nature of G4s and the high energy barrier to unfold c-MYC promoter G4s. Here, we used single-molecule magnetic tweezers to manipulate a duplex hairpin containing a c-MYC promoter sequence to mimic the transiently denatured duplex during transcription. We measured the effects of six commonly used G4s binding ligands on the competition between quadruplex and duplex structures, as well as the folding/unfolding kinetics of G4s. Our results revealed two distinct roles for G4s selective stabilization: CX-5461 is mainly acting as c-MYC G4s stabilizer, reducing the unfolding rate (ku) of c-MYC G4s, whereas PDS and 360A also act as G4s chaperone, accelerating the folding rates (kf) of c-MYC G4s. qRT-PCR results obtained from CA46 and Raji cell lines demonstrated that G4s stabilizing ligands can downregulate c-MYC expression, while G4s stabilizer CX-5461 exhibited the strongest c-MYC gene suppression. These results shed light on the potential of manipulating G4s' folding/unfolding kinetics by ligands for precise regulation of promoter G4-associated biological activities.

SiRNA-mediated downregulation of BATF3 diminished proliferation and induced apoptosis through downregulating c-Myc expression in chronic myelogenous leukemia cells.

Despite considerable improvement in therapeutic approaches to chronic myeloid leukemia (CML) treatment, this malignancy is considered incurable due to resistance. However, investigating the molecular mechanism of CML may give rise to the development of extremely efficient targeted therapies that improve the prognosis of patients. Basic leucine zipper transcription factor ATF-like3 (BATF3), as transcription factor, is considered a key regulator of cellular activities and its function has been evaluated in tumor development and growth in several cancer types. This study aimed to evaluate the potential of the cellular impact of siRNA-mediated downregulation of BATF3 on CML cancer cells through cell proliferation, induction of apoptosis, and cell cycle distribution. The transfection of BATF3 siRNA to K562 CML cells was performed by electroporation device. To measure cellular viability and apoptosis, MTT assay and Annexin V/PI staining were carried out, respectively. Also, cell cycle assay and flow cytometry instrument were applied to assess cell cycle distribution of K562 cells. For more validation, mRNA expression of correlated genes was relatively evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). The data indicated that siRNA-mediated BATF3 inactivating severely promoted the cell apoptosis. Also, the targeted therapy led to high expression of Caspase-3 gene and Bax/Bcl-2 ratio. Silenced BATF3 also induced cell cycle arrest in phase sub-G1 compared to control. Finally, a noticeable decrement was obtained in c-Myc gene expression through suppression of BATF3 in CML cells. The findings of this research illustrated the suppression of BATF3 as an effective targeted therapy strategy for CML.

The Combination of Methioninase and Ethionine Exploits Methionine Addiction to Selectively Eradicate Osteosarcoma Cells and Not Normal Cells and Synergistically Down-regulates the Expression of C-MYC.

The fundamental and general hallmark of cancer cells, methionine addiction, termed the Hoffman effect, is due to overuse of methionine for highly-increased transmethylation reactions. In the present study, we tested if the combination efficacy of recombinant methioninase (rMETase) and a methionine analogue, ethionine, could eradicate osteosarcoma cells and down-regulate the expression of c-MYC. 143B osteosarcoma cells and Hs27 normal human fibroblasts were tested. The efficacy of rMETase alone and ethionine, alone and in their combination, on cell viability was determined with the WST-8 assay on 143B cells and Hs27 cells. c-MYC expression was examined with western immunoblotting and compared in 143B cells treated with/without rMETase, ethionine, or the combination of both rMETase and ethionine. 143B cells were more sensitive to both rMETase and ethionine than Hs 27 cells, with the following IC50s: rMETase (143B: 0.22 U/ml; Hs27: 0.82 U/ml); ethionine (143B: 0.24 mg/ml; Hs27: 0.42 mg/ml). The combination of rMETase and ethionine synergistically eradicated 143B cells, lowering the IC50 for ethionine 14-fold compared to ethionine alone (p<0.001). In contrast, Hs27 fibroblasts were relatively resistant to the combination. The expression of c-MYC was significantly down-regulated only by the combination of rMETase and ethionine in 143B cells (p<0.001). In the present study, we showed, for the first time, the synergistic combination efficacy of rMETase and ethionine on osteosarcoma cells in contrast to normal fibroblasts, which were relatively resistant. The combination of rMETase and ethionine down-regulated c-MYC expression in the cancer cells. The present results indicate the combination of rMETase and ethionine may reduce the malignancy of osteosarcoma cells and can be a potential future clinical strategy.

Selinexor Synergizes CX4945 on Anti-Tumor Effect By Targeting XPO1/Ikros/c-Myc Signaling in T-Cell Acute Lymphoblastic Leukemia

Background Acute lymphocytic leukemia (ALL) is an aggressive hematologic malignancy with poor outcomes. The IKZF1 (Ikaros) gene plays a crucial role in normal hematopoiesis as well as acts as a leukemia suppressor in ALL. Casein kinase II (CK2) inhibitor, CX4945, has shown potential function in restoring Ikaros on transcriptional repression of target genes in ALL. Exportin-1 (XPO1) is a critical mediator of nuclear export, which is essential for regulating the cell cycle and proliferation of normal and malignant tissues. Increased expression of XPO1 has been observed in various types of cancer, including ALL. In this study, we investigated the combined effects of Selinexor and CX4945 in T-cell ALL (T-ALL) and explored the underlying mechanisms. Methods Cell Counting Kit-8(CCK-8) was used for cell viability assay, and Annexin-V/PI staining following flow cytometry analysis for apoptosis. qPCR was used for gene expression in CEM and Molt4 T-ALL cell lines. CalcuSyn analysis was performed for a synergistic effect. Results Treatment of CX4945 or Selinexor significantly led to cell proliferation arrest of CEM and Molt4 cells in a dose-dependent manner. The combination of Selinexor with CX4945 significantly enhanced the cell proliferation arrest of CEM and Molt4 cells versus the single drug controls, and CalcuSyn analysis exhibited a synergistic effect of the two drugs in the cells (Fig.1A, B). The combination also significantly increased the apoptotic cells compared to the single-drug controls (Fig.1C). c-Myc oncogene plays an essential role in human cancers. Our results showed that c-Myc mRNA level was significantly higher expressed in the cohort of T-ALL patients compared to that of normal bone marrow controls (Fig.1D). To gain insight into the underlying mechanism of the synergy, we observed the effect of the drugs on the expression of c-Myc. Results showed that the combination of Selinexor with CX4945 significantly down-regulated the expression of c-Myc compared to the single-drug controls in CEM and Molt4 cells (Fig.1E). Moreover, the combination of Selinexor with CX4945 significantly enhanced the cell growth arrest in primary cells from T-ALL patients compared to single drug controls (Fig.1F). Taken together, our data indicated the synergistic effect of Selinexor with CX4945 on cell proliferation arrest and apoptosis by down-regulation of c-Myc expression. We previously reported that Ikaros directly regulates c-Myc transcription in ALL and CX4945 suppresses c-Myc expression in a Ikaros-dependent manner. Also, c-Myc is the cargo of XPO1. Thus, our results in this study reveal a model that treatment with XPO1 inhibitor, Selinexor prevents the nuclear transport of c-Myc and leads to its nuclear accumulation and down-regulation of c-Myc expression. The combination of Selinexor and CX4945 showed the synergistic anti-tumor effect by suppressing c-Myc expression in both transcriptional and post-transcriptional levels. The mechanism model is summarized in Fig.1G. ConclusionsThe combination of Selinexor and CX4945 has synergistic effects on cell proliferation arrest and apoptosis in T-ALL by targeting the XPO1/IKROS/c-Myc signaling. Our results also provide experimental evidence for the new combination of Selinexor and CX4945 as a new potential therapeutic option for T-ALL patients.

Dual PI3K/HDAC Inhibitor BEBT-908 Exhibits Potent Efficacy as Monotherapy for Primary Central Nervous System Lymphoma.

The efficacy of systemic treatment for primary central nervous system lymphoma (PCNSL) is limited because of the blood-brain barrier (BBB) and the ineffectiveness of chemotherapy. The dual PI3K/HDAC inhibitor BEBT-908 has exhibited favorable in vivo distribution and activity in various cancers. The aims of this study were to assess the efficacy of BEBT-908 in brain orthotopic mouse models of hematological malignancies, to investigate its pharmacologic properties, and to elucidate the underlying mechanism of action. We evaluated the anticancer activity of BEBT-908 in various hematological malignancies through cell viability assays. The impact of BEBT-908 on c-Myc expression and ferroptosis signaling pathways was assessed using Western blotting, qPCR, ROS detection, GSH/GSSG detection, and IHC. Pharmacokinetic and pharmacodynamic profiles were assessed through LC-MS/MS and Western blotting. The effects of BEBT-908 in vivo were examined using xenografts and brain orthotopic mouse models. Our findings demonstrate that BEBT-908 exhibits promising anti-tumor activity in vitro and in vivo across multiple subtypes of hematological malignancies. Furthermore, BEBT-908 exhibits excellent BBB penetration and inhibits tumor growth in a brain orthotopic lymphoma model with prolonged survival of host mice. Mechanistically, BEBT-908 downregulated c-Myc expression, which contributed to ferroptosis, ultimately leading to tumor shrinkage. Our study provides robust evidence for the dual PI3K/HDAC inhibitor BEBT-908 as an effective anti-cancer agent for PCNSL.

3-Bromopyruvate Inhibits the Growth and Glucose Metabolism of TNBC Xenografts in Nude Mice by Targeting c-Myc.

Due to the lack of effective drug treatment, triple-negative breast cancer (TNBC) is prone to recurrence and metastasis after an operation. As a glycolytic inhibitor, 3-bromopyruvic acid (3-BrPA) can inhibit the proliferation and induce apoptosis of TNBC cells. However, whether it has similar effects in animal models remains unclear. To observe the effect of 3-BrPA on the growth and glucose metabolism of human TNBC transplanted tumors in nude mice and to investigate the mechanism. We constructed subcutaneous xenografts of human TNBC in nude mice and treated them with low, medium and high concentrations of 3-BrPA. After 15 days, nude mice were sacrificed to detect hexokinase (HK) activity and adenosine triphosphate (ATP) content in tumor tissues. Hematoxylin-eosin (HE) staining was used to detect the damage of transplanted tumors and liver and kidney in nude mice, which 3-BrPA caused. The expression of c-Myc in tumor tissues was detected by Immunohistochemistry (IHC). Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining was used to detect the apoptosis of tumor tissues. Besides, the expressions of Cytc, Bax, Bcl-2 and Caspase-9 were detected by Western blotting. Compared with the control group, intraperitoneal injection of 3-BrPA inhibited the growth of human TNBC transplant tumors, decreased HK activity and ATP production in tumor tissues, disrupted the tissue structure of transplant tumors, and did not significantly damage liver and kidney tissues. IHC staining and Western blotting showed that 3-BrPA could decrease the expression of c-Myc and Bcl-2, increase the expression of Cyt -c, Bax and Caspase-9 expression and promote apoptosis in tumor tissues. The above data indicate that 3-BrPA inhibits the growth of human TNBC transplanted tumors and promotes their apoptosis. Its anti-cancer mechanism might reduce HK activity by down-regulating c-Myc expression, eventually leading to decreased glycolytic pathway energy production and promoting apoptosis of transplanted tumors.

Abstract 1690: Myc suppression permits entry into the cancer endocycle to evade toxic effects of chemotherapy

Abstract Recent advances in precision medicine and immunotherapy have made great strides in cancer treatment and care, but chemoresistance remains a major challenge. One method of chemoresistance employed by cancer cells is accession of the protective polyaneuploid cancer cell (PACC) state, in which cells enter a functionally dormant state upon environmental stress. Entry into the PACC state begins with a whole-genome duplication event followed by endocycling, where the cells are metabolically active and cycling through repeated G1, S and G2 phases of the cell cycle without dividing. While in this state, cells avoid the mitotic stress exerted by common chemotherapeutics and survive therapy, eventually undergoing a depolyploidization process to repopulate the tumor, driving cancer lethality. The mechanisms by which a cancer cell can switch between a mitotic cell cycle and an endocycle are unknown. Cancer is characterized by deregulated cell proliferation, often driven by mutation or amplification of genes that govern the cell cycle. C-myc, an oncogenic transcription factor, is dysregulated in roughly 70% of cancers and is clinically used as a negative prognostic factor for disease-free survival and metastasis. C-myc is responsible for the transcriptional activation of many cell cycle-related genes, and repression of cell cycle inhibitors. Our data indicate that endocycling cells in the PACC state downregulate c-myc expression. Transcriptomic analyses show repression of myc targets, along with supporting protein data that total c-myc protein levels are decreased. While myc downregulation is expected in non-proliferative cells, the compensatory mechanisms mediating the G1/S transition in the cancer endocycle remain unknown. These observations suggest the presence of underlying mechanisms to reprogram the mitotic cell cycle to access the PACC state. We hypothesize that myc downregulation is essential for cells to activate the cancer endocyle and enter the protective PACC state. Understanding the mechanisms that govern this transition is crucial to generate next-generation cancer therapeutics to block accession or disrupt this state. Citation Format: Michael Loycano, Kenneth J. Pienta, Sarah R. Amend. Myc suppression permits entry into the cancer endocycle to evade toxic effects of chemotherapy [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 1690.

Targeted downregulation of MYC mediated by a highly efficient lactobionic acid-based glycoplex to enhance chemosensitivity in human hepatocellular carcinoma cells

The chemosensitization of tumor cells by gene therapy represents a promising strategy for hepatocellular carcinoma (HCC) treatment. In this regard, HCC-specific and highly efficient gene delivery nanocarriers are urgently needed. For this purpose, novel lactobionic acid-based gene delivery nanosystems were developed to downregulate c-MYC expression and sensitize tumor cells to low concentration of sorafenib (SF). A library of tailor-made cationic glycopolymers, based on poly(2-aminoethyl methacrylate hydrochloride) (PAMA) and poly(2-lactobionamidoethyl methacrylate) (PLAMA) were synthesized by a straightforward activators regenerated by electron transfer atom transfer radical polymerization. The nanocarriers prepared with PAMA114-co-PLAMA20 glycopolymer were the most efficient for gene delivery. These glycoplexes specifically bound to the asialoglycoprotein receptor and were internalized through the clathrin-coated pit endocytic pathway. c-MYC expression was significantly downregulated by MYC short-hairpin RNA (MYC shRNA), resulting in efficient inhibition of tumor cells proliferation and a high levels apoptosis in 2D and 3D HCC-tumor models. Moreover, c-MYC silencing increased the sensitivity of HCC cells to SF (IC50 for MYC shRNA + SF 1.9 μM compared to 6.9 μM for control shRNA + SF). Overall, the data obtained demonstrated the great potential of PAMA114-co-PLAMA20/MYC shRNA nanosystems combined with low doses of SF for the treatment of HCC.

A new inhibitor of human peptide deformylase suppresses cell proliferation and induces cell apoptosis and autophagy in cancers.

Human peptide deformylase (hsPDF) has been found overexpressed in many cancer cells and its inhibitors exhibit antitumor activity. Studies were performed to validate that hsPDF is a good antitumor target. The inhibitory effect of PDF64 on hsPDF enzymatic activity was measured and confirmed by computation analysis. Antiproliferation activity was determined and in-vivo antitumor activity were analyzed in HCT116 and HL60 nude mice xenografts. Mitochondrial membrane potential (MMP), cell apoptosis, and autophagic cell death were analyzed by flow cytometry. ATP level was quantified using an ATP assay kit. Protein expression and kinase phosphorylation were determined by western blotting. A new hsPDF inhibitor PDF64 was identified. It showed evident antiproliferation activity in 10 cancer cells and significantly suppressed tumor growth in HCT116 and HL60 xenografts. It induced an obvious decrease in MMP and caused apparent cell apoptosis and autophagy in HCT116 and Jurkat cells. PDF64 treatment also led to an evident decrease in cellular ATP levels in these cells. Moreover, PDF64 downregulated c-Myc expression and had some effects on extracellular regulated protein kinases (ERK) and protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) pathways. PDF64 exhibited good antitumor effects both in vivo and in vitro . It caused cell apoptosis and autophagic death in HCT116 and Jurkat cells. The effects may be mediated by inhibiting c-Myc expression and ERK or PI3K-Akt-mTOR pathway. Therefore, PDF64 may be a promising reagent for antitumor drug development, which further supports that hsPDF is a good antitumor drug target.

Abstract A037: TT-00420, a novel kinase inhibitor potentially benefiting c-Myc amplified/overexpressed osteosarcoma

Abstract Osteosarcoma (OS) is the most common bone tumor in pediatric patients, whose effective therapies are of great unmet medical needs, particularly for those of high-risk features. c-Myc, a well-known oncogene, is commonly amplified/overexpressed in OS patients, contributes to dismal prognosis and associates with lower 5-year overall survival rate, which is also confirmed by our retrospective analysis for the correlation between c-Myc gene amplification/overexpression and patient prognosis in our patient cohort. TT-00420, a clinical-stage small molecule targeting Aurora A/B, VEGFRs, FGFRs, JAKs and CSF1R, has demonstrated down-regulation on c-Myc expression in TNBC studies. Moreover, as reported, Aurora kinases and c-Myc regulate each other back and forth, triggering maintenance of the malignant state. In this study, we examined the efficacy of TT-00420 in c-Myc-amplified/overexpressed OS. In pre-clinical clonogenic assay, TT-00420 significantly inhibited the colony formation in c-Myc-overexpressed OS cell lines in a dose-dependent manner. In MNNG/HOS cell line, we demonstrated that TT-00420 dramatically suppressed Aurora kinase pathway and blunted c-Myc protein expression level, indicating TT-00420 might down-regulate c-Myc by Aurora kinases inhibition. In pre-clinical in-vivo efficacy studies, 143B cells were injected into the medullary cavity of the tibia to make the orthotopic OS xenograft model. With 15 mg/kg/day treatment of TT-00420, tumor growth was obviously inhibited as compared to vehicle group. Immunohistochemistry (IHC) analyses in tumors revealed that TT-00420-treated tumors exhibited increased apoptosis with upregulated expression of cleaved caspase 3 (CC3) and H2AX, and significantly decreased proliferations with raised expression of Ki67. Moreover, in a c-Myc-overexpressed OS patient-derived xenograft (PDX) model from a male pediatric patient, 15 mg/kg/day TT-00420 dramatically blunted the tumor growth with a TGI of 87.6%. In China, an investigator-initiated trial is currently ongoing to evaluate the safety and tolerability of TT-00420 in OS patients with c-Myc overexpression (ChiCTR2000036618). Taken together, TT-00420 depicted robust anti-tumor activity in c-Myc overexpressed OS both in vitro and in vivo with downregulation of c-Myc expression, indicating its potential as a novel monotherapy for OS patients with c-Myc overexpression. Future clinical trial result is of great expectation. Citation Format: Yingqi Hua, Xiaoyan Qiang, Kai Tian, Yafei Jiang, Frank Wu, Peng Peng. TT-00420, a novel kinase inhibitor potentially benefiting c-Myc amplified/overexpressed osteosarcoma [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A037.

Effects of G-Quadruplex-Binding Plant Secondary Metabolites on c-MYC Expression.

Guanine-rich DNA sequences tending to adopt noncanonical G-quadruplex (G4) structures are over-represented in promoter regions of oncogenes. Ligands recognizing G4 were shown to stabilize these DNA structures and drive their formation regulating expression of corresponding genes. We studied the interaction of several plant secondary metabolites (PSMs) with G4s and their effects on gene expression in a cellular context. The binding of PSMs with G4s formed by the sequences of well-studied oncogene promoters and telomeric repeats was evaluated using a fluorescent indicator displacement assay. c-MYC G4 folding topology and thermal stability, as well as the PMS influence on these parameters, were demonstrated by UV-spectroscopy and circular dichroism. The effects of promising PSMs on c-MYC expression were assessed using luciferase reporter assay and qPR-PCR in cancer and immortalized cultured cells. The ability of PMS to multi-targeting cell signaling pathways was analyzed by the pathway-focused gene expression profiling with qRT-PCR. The multi-target activity of a number of PSMs was demonstrated by their interaction with a set of G4s mimicking those formed in the human genome. We have shown a direct G4-mediated down regulation of c-MYC expression by sanguinarine, quercetin, kaempferol, and thymoquinone; these effects being modulated by PSM’s indirect influence via cell signaling pathways.

Phenformin Down-Regulates c-Myc Expression to Suppress the Expression of Pro-Inflammatory Cytokines in Keratinocytes.

The treatment of many skin inflammation diseases, such as psoriasis and atopic dermatitis, is still a challenge and inflammation plays important roles in multiple stages of skin tumor development, including initiation, promotion and metastasis. Phenformin, a biguanide drug, has been shown to play a more efficient anti-tumor function than another well-known biguanide drug, metformin, which has been reported to control the expression of pro-inflammatory cytokines; however, little is known about the effects of phenformin on skin inflammation. This study used a mouse acute inflammation model, ex vivo skin organ cultures and in vitro human primary keratinocyte cultures to demonstrate that phenformin can suppress acute skin inflammatory responses induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in vivo and significantly suppresses the pro-inflammatory cytokines IL-1β, IL-6 and IL-8 in human primary keratinocytes in vitro. The suppression of pro-inflammatory cytokine expression by phenformin was not directly through regulation of the MAPK or NF-κB pathways, but by controlling the expression of c-Myc in human keratinocytes. We demonstrated that the overexpression of c-Myc can induce pro-inflammatory cytokine expression and counteract the suppressive effect of phenformin on cytokine expression in keratinocytes. In contrast, the down-regulation of c-Myc produces effects similar to phenformin, both in cytokine expression by keratinocytes in vitro and in skin inflammation in vivo. Finally, we showed that phenformin, as an AMPK activator, down-regulates the expression of c-Myc through regulation of the AMPK/mTOR pathways. In summary, phenformin inhibits the expression of pro-inflammatory cytokines in keratinocytes through the down-regulation of c-Myc expression to play an anti-inflammation function in the skin.

3-Bromopyruvic acid regulates glucose metabolism by targeting the c-Myc/TXNIP axis and induces mitochondria-mediated apoptosis in TNBC cells.

Aerobic glycolysis is commonly observed in tumor cells, including triple-negative breast cancer (TNBC) cells, and the rate of aerobic glycolysis is higher in TNBC cells than in non-TNBC cells. Hexokinase 2 (HK2) is a key enzyme in the glycolytic pathway and a target of the transcription factor c-Myc, which is highly expressed in TNBC and promotes aerobic glycolysis by enhancing HK2 expression. As an inhibitor of HK2, 3-bromopyruvic acid (3-BrPA) exhibits good therapeutic efficacy in intrahepatic and extrahepatic tumors and inhibits the proliferation of human tumor cells with high expression levels of c-Myc in vivo and in vitro. In addition, 3-BrPA combines with photodynamic therapy to inhibit TNBC cell migration. Thioredoxin-interacting protein (TXNIP) competes with c-Myc to reduce glucose consumption in tumor cells to restrain cell proliferation. A comparative analysis was performed in the present study in TNBC (HCC1143) and non-TNBC (MCF-7) cell lines to explore the effect of 3-BrPA on energy metabolism in TNBC cells and to investigate the possible mechanism of action. Cell viability and apoptosis were detected through Cell Counting Kit-8 and flow cytometry assays, respectively. Expression levels of HK2, glucose transporter 1, TXNIP, c-Myc and mitochondria-regulated apoptosis pathway proteins were measured through western blotting. 3-BrPA inhibited cell proliferation, downregulated c-Myc and HK2 expression, and upregulated TXNIP expression in TNBC cells, but it doesn't have the same effect on non-TNBC cells. Furthermore, 3-BrPA induced the typical manifestations of mitochondrial-mediated apoptosis such as decreasing Bcl-2 expression and increasing Bax, Cyt-C and Caspase-3 expression. The present results suggested that 3-BrPA promoted TXNIP protein expression and reduced HK2 expression in TNBC cells by downregulating c-Myc expression, inhibiting glycolysis including suppressing lactate generation, intracellular ATP generation and HK activity, inducing mitochondrial-mediated apoptosis and eventually suppressing TNBC cell proliferation. These findings may reveal a novel therapeutic target for the clinical treatment of TNBC.

Novel dual-targeting c-Myc inhibitor D347-2761 represses myeloma growth via blocking c-Myc/Max heterodimerization and disturbing its stability

BackgroundTranscription factor c-Myc plays a critical role in various physiological and pathological events. c-Myc gene rearrangement is closely associated with multiple myeloma (MM) progression and drug resistance. Thereby, targeting c-Myc is expected to be a useful therapeutic strategy for hematological disease, especially in MM.MethodsMolecular docking-based virtual screening and dual-luciferase reporter gene assay were used to identify novel c-Myc inhibitors. Cell viability and flow cytometry were performed for evaluating myeloma cytotoxicity. Western blot, immunofluorescence, immunoprecipitation, GST pull down and Electrophoretic Mobility Shift Assay were performed for protein expression and interaction between c-Myc and Max. c-Myc downstream targets were measured by Q-PCR and Chromatin immunoprecipitation methods. Animal experiments were used to detect myeloma xenograft and infiltration in vivo.ResultsWe successfully identified a novel c-Myc inhibitor D347-2761, which hindered the formation of c-Myc/Max heterodimer and disturbed c-Myc protein stability simultaneously. Compound D347-2761 dose-and time-dependently inhibited myeloma cell proliferation and induced apoptosis. Dual knockout Bak/Bax partially restored D347-2761-mediated cell death. Additionally, compound D347-2761 could, in combination with bortezomib (BTZ), enhance MM cell DNA damage and overcome BTZ drug resistance. Our in vivo studies also showed that compound D347-2761 repressed myeloma growth and distal infiltration by downregulating c-Myc expression. Mechanistically, novel dual-targeting c-Myc inhibitor D347-2761 promoted c-Myc protein degradation via stimulating c-Myc Thr58 phosphorylation levels, which ultimately led to transcriptional repression of CDK4 promoter activity.ConclusionsWe identified a novel dual-targeting c-Myc small molecular inhibitor D347-2761. And this study may provide a solid foundation for developing a novel therapeutic agent targeting c-Myc.CCo5k36iLrbCHdtx-yHunTVideo

Identification of Trovafloxacin, Ozanimod, and Ozenoxacin as Potent c-Myc G-Quadruplex Stabilizers to Suppress c-Myc Transcription and Myeloma Growth.

c-Myc is a major oncogene that is estimated to result in almost all human cancers and the c-Myc downregulation has become an attractive strategy for cancer treatment. For it is hard to design compounds that can directly interact with the c-Myc protein, the DNA G-quadruplex (G4) was discovered in its promoter region which was referred to as a potential drug target for controlling c-Myc expression. In this study, a combined strategy of molecular docking-based virtual screening, molecular dynamics (MD) simulation, and molecular mechanics/generalized Born surface area (MM/GBSA) free energy calculation was conducted on the existing FDA-Approved Drugs Library, eight compounds were selected for further experimental assay. Among them, five compounds exhibited dose-dependently anticancer activities against RPMI-8226 cells with IC50 values less than 18.4 μM. Further experiments showed that Trovafloxacin, Ozanimod, and Ozenoxacin decreased c-Myc mRNA level obviously and downregulated c-Myc expression significantly. In summary, compounds Trovafloxacin, Ozanimod, and Ozenoxacin might be regarded as new c-Myc G4 stabilizers for the treatment of c-Myc related cancers in the future.

PRMT5-activated c-Myc promote bladder cancer proliferation and invasion through up-regulating NF-κB pathway

AimPRMT5 and c-Myc were considered as oncogene of bladder cancer. Nevertheless, whether the interaction between of PRMT5 and c-Myc affect bladder cancer progress is unknown. Herein, we explore the above points and discuss deeply its’ potential mechanism. Method5637 and T24 cells were study subjects in vitro. Western blot was used to examined the protein expression. CCK8 and transwell assay were used to analyze proliferation and invasion ability. Additionally, xenograft tumor model was established. Mice imaging experiment, Immunochemistry assay and western blot were carried out. ResultWestern blot result showed successful transfection of PRMT5-siRNA and c-Myc-siRNA. PRMT5-siRNA could inhibit c-Myc expression, and decrease the proliferation and invasion of bladder cells. And c-Myc overexpression could reverse inhibitory action caused by PRMT5 silence. And in vitro studies found low-expression of c-Myc reduced proliferation and invasion of tumor cells and make the NF-κB pathway inactivation. In vivo studies also demonstrated that inhibiting PRMT5 could downregulate c-Myc expression and inhibit the bladder cancer progress, and the potential mechanism was likely to be related to NF-κB signaling pathway. ConclusionIn a word, low-expression of PRMT5 suppressed c-Myc, and thus inhibited proliferation and invasion ability of 5637 and T24 cells through NF-κB pathway.

Gene Expression Profiling and Protein Analysis Reveal Suppression of the C-Myc Oncogene and Inhibition JAK/STAT and PI3K/AKT/mTOR Signaling by Thymoquinone in Acute Myeloid Leukemia Cells.

Overexpression of c-Myc plays an essential role in leukemogenesis and drug resistance, making c-Myc an attractive target for cancer therapy. However, targeting c-Myc directly is impossible, and c-Myc upstream regulator pathways could be targeted instead. This study investigated the effects of thymoquinone (TQ), a bioactive constituent in Nigella sativa, on the activation of upstream regulators of c-Myc: the JAK/STAT and PI3K/AKT/mTOR pathways in HL60 leukemia cells. Next-generation sequencing (NGS) was performed for gene expression profiling after TQ treatment. The expression of c-Myc and genes involved in JAK/STAT and PI3K/AKT/mTOR were validated by quantitative reverse transcription PCR (RT-qPCR). In addition, Jess assay analysis was performed to determine TQ’s effects on JAK/STAT and PI3K/AKT signaling and c-Myc protein expression. The results showed 114 significant differentially expressed genes after TQ treatment (p < 0.002). DAVID analysis revealed that most of these genes’ effect was on apoptosis and proliferation. There was downregulation of c-Myc, PI3K, AKT, mTOR, JAK2, STAT3, STAT5a, and STAT5b. Protein analysis showed that TQ also inhibited JAK/STAT and PI3K/AKT signaling, resulting in inhibition of c-Myc protein expression. In conclusion, the findings suggest that TQ potentially inhibits proliferation and induces apoptosis in HL60 leukemia cells by downregulation of c-Myc expression through inhibition of the JAK/STAT and PI3K/AKT signaling pathways.

Synthesis of N-acyl Derivatives of Aminocombretastatin A-4 and Study of their Interaction with Tubulin and Downregulation of c-Myc.

Six N-acyl derivatives of aminocombretastatin A-4 have been synthesized and evaluated according to their interaction with tubulin and as c-Myc downregulators. In search of new promising anti-cancer agents. This study is focused on the synthesis and the biological evaluation of N-acyl derivatives of aminocombretastatin A-4 (CA-4). Docking studies were carried out to find out whether the synthetic derivatives could bind to tubulin at the colchicine site in a conformation similar to that of CA- 4. The synthetic derivatives' effect on the proliferation of several cancer cells and non-cancer cells has been measured. Their effect on tubulin polymerization, cell cycle distribution, the microtubule network and c-Myc expression has also been evaluated. A set of six N-acyl derivatives was achieved by means of a peptide-type coupling of aminocombretastatin A-4 and the corresponding carboxylic acid. The synthetic compounds' ability to inhibit cell proliferation was measured by MTT assay against three human carcinoma cell lines (colorectal HT-29, lung A549, and breast adenocarcinoma MCF-7) and one non-tumor cell line (HEK- 293). Turbidimetry time-course measurements evaluated the inhibition of tubulin polymerization. The action of the synthetic derivatives on cell cycle distribution was measured by flow cytometry and their effects on the microtubule network were determined by immunofluorescence microscopy. Finally, the downregulation of the synthetic derivatives on c-Myc protein was quantified by ELISA assay, while the effect on c-Myc gene was measured by RT-qPCR analysis. Derivatives bearing pentanoyl (compound 2), hexanoyl (compound 3), and heptanoyl (compound 4) side chains show anti-proliferative activities on the HT-29 line in the low nanomolar range, with values similar to that exhibited by AmCA-4 but far exceeding those of CA-4. Compounds 1 (butanoyl side chain) and 2-3 inhibit tubulin polymerization in vitro in a manner similar to that of CA-4 and AmCA-4 whereas compounds 4, 5 (octanoyl side chain) and 6 (dodecanoyl side chain) may be considered as partial inhibitors of tubulin polymerization. While all derivatives are able to accumulate cells in G2/M phase, compounds with the longest acyl chains (5 and 6) are the least active ones in this particular action. Moreover, compounds 2-3 were the most active ones as c-Myc downregulators. Our studies show that the most active compounds in the disruption of the microtubule network are also the most potent ones in the downregulation of c-Myc expression. Other: Compounds 2 and 3 are good candidates for in vivo studies as they combine the best antimitotic and c-Myc downregulation activities at low doses.