c-Myc Phosphorylation Research Articles

Inhibition of WNK Kinases in NK Cells Disrupts Cellular Osmoregulation and Control of Tumor Metastasis

Introduction: The serine/threonine with-no-lysine (WNK) kinase family function in blood pressure control, electrolyte homeostasis, and cellular osmoregulation. These kinases and their downstream effectors are considered promising therapeutic targets in hypertension and stroke. However, the role of WNK kinases in immune cells remains poorly understood. Methods: Using the small-molecule WNK kinase inhibitors WNK463 and WNK-IN-11, we investigated how WNK kinase inhibition affects natural killer (NK) cell physiology. Results: WNK kinase inhibition with WNK463 or WNK-IN-11 significantly decreased IL-2-activated NK cell volume, motility, and cytolytic activity. Treatment of NK cells with these inhibitors induced autophagy by activating AMPK and inhibiting mTOR signaling. Moreover, WNK kinase inhibition increased phosphorylation of Akt and c-Myc by misaligning activity of activating kinases and inhibitory phosphatases. Treatment of tumor-bearing mice with WNK463 impaired tumor metastasis control by adoptively transferred NK cells. Conclusion: The catalytic activity of WNK kinases has a critical role of multiple aspects of NK cell physiology and their pharmacologic inhibition negatively impacts NK cell function.

Metabolic Reprogramming of Tumor-Associated Macrophages Using Glutamine Antagonist JHU083 Drives Tumor Immunity in Myeloid-Rich Prostate and Bladder Cancers.

Glutamine metabolism in tumor microenvironments critically regulates antitumor immunity. Using the glutamine-antagonist prodrug JHU083, we report potent tumor growth inhibition in urologic tumors by JHU083-reprogrammed tumor-associated macrophages (TAMs) and tumor-infiltrating monocytes. We show JHU083-mediated glutamine antagonism in tumor microenvironments induced by TNF, proinflammatory, and mTORC1 signaling in intratumoral TAM clusters. JHU083-reprogrammed TAMs also exhibited increased tumor cell phagocytosis and diminished proangiogenic capacities. In vivo inhibition of TAM glutamine consumption resulted in increased glycolysis, a broken tricarboxylic acid (TCA) cycle, and purine metabolism disruption. Although the antitumor effect of glutamine antagonism on tumor-infiltrating T cells was moderate, JHU083 promoted a stem cell-like phenotype in CD8+ T cells and decreased the abundance of regulatory T cells. Finally, JHU083 caused a global shutdown in glutamine-utilizing metabolic pathways in tumor cells, leading to reduced HIF-1α, c-MYC phosphorylation, and induction of tumor cell apoptosis, all key antitumor features. Altogether, our findings demonstrate that targeting glutamine with JHU083 led to suppressed tumor growth as well as reprogramming of immunosuppressive TAMs within prostate and bladder tumors that promoted antitumor immune responses. JHU083 can offer an effective therapeutic benefit for tumor types that are enriched in immunosuppressive TAMs.

STK16 promoted colorectal cancer progress in a c-MYC signaling-dependent manner

BackgroundColorectal cancer standed as a global health challenge, ranking third in cancer incidence and second in cancer-related deaths worldwide. A deeper understanding of the intricate mechanisms driving colorectal cancer development was pressing need. STK16 had garnered attention in recent researches, while its involvement in cancer had been minimally explored. c-MYC had emerged as a key player in cancer biology. Due to its complex structure, multifunctionality, and intricate interactions, directly inhibiting the activity of c-MYC proves to be challenging. Hence, current research was directing efforts towards modulating c-MYC expression levels.MethodsImmunoblot, Immunohistochemistry and immunoprecipitation assays were conducted to assess the indicated protein expression levels. RT-PCR was performed to detect the corresponding mRNA expression levels. The proliferation, migration, invasion, and colony formation abilities of the specified cancer cells were investigated using CCK8 assays, Brdu assays, transwell assays, and colony formation assays, respectively. Cellular and animal experiments were performed to investigate the correlation between STK16 signaling and c-MYC signaling.ResultsSTK16 plays a positive regulatory role in the progression of colorectal cancer. Delving into the molecular mechanisms, we unveiled that STK16 phosphorylated c-MYC at serine 452, a pivotal event hindering the ubiquitin-proteasome pathway degradation of c-MYC. Importantly, colorectal cancer proliferation mediated by STK16 was found to be dependent on the phosphorylation of c-MYC at S452. Furthermore, the researchers demonstrated that STK16 knockout or pharmacological inhibition significantly curtailed colorectal cancer proliferation and c-MYC expression in in vivo animal models.ConclusionWe discovered that STK16 phosphorylates c-MYC at serine 452, hindering its degradation via the ubiquitin-proteasome pathway. STK16 inhibition, either genetically or pharmacologically, effectively curtails cancer growth and c-MYC expression in vivo. These findings highlight STK16 as a potential therapeutic target for colorectal cancer.

Abstract 3017: Lack of MCPIP1 enzymatic activity leads to neoplastic transformation of normal kidney cells

Abstract Introduction: The MCPIP1 protein (Monocyte Chemotactic Protein-1 Induced Protein) is involved in the negative regulation of inflammation due to its RNase activity. A growing number of publications suggest that the MCPIP1 protein may influence the development of cancer by regulation of factors involved in angiogenesis, proliferation and cell death. We believe, that MCPIP1 may be a potential tumor suppressor. Our recent results show that lack of enzymatic activity of MCPIP1 leads to increased tumor growth, angiogenesis and metastasis. The main aim of our research is to study the importance of MCPIP1 for neoplastic transformation of normal, epithelial kidney cells, as well as acquirement of stemness features. Material and Methods: To examine the effect of MCPIP1 in normal epithelial cell lines TCMK-1, RPTEC-Tert1 and HK-2 were transduced to overexpress mutated, inactive form of MCPIP1 (pLIX D141N) with proper control (pLIX PURO). We analyzed cells clonogenicity, as well as the levels of CSCs markers by western blot, NGS and qPCR. Next, cells were injected subcutaneously into NOD-SCID mice to check if mutation of MCPIP1 will induce tumor growth in vivo. Mice blood was analyzed for the presence of circulating tumor cells (CTCs), and secretion of cytokines by Proteome Profiler assay. Tumors were evaluated by multiple IHC stainings, as well as western blot and qPCR. Results and Discussion: We have shown that the mutation of MCPIP1 increases the clonogenicity of kidney cells. Moreover, pLIX D141N cells were characterized by higher levels of the c-Met receptor, vimentin, Twist, CD44 and c-Myc, which are the markers of epithelial to mesenchymal transition and cancer stemness. The obtained results suggest that the loss of the MCPIP1 protein causes the acquisition of the characteristics of neoplastic cells. Next, we checked whether MCPIP1 mutation in normal cells predisposes them to proliferate when administered to mice. We found that, D141N mutation caused the growth of large tumors with higher expression of Cd44, Klf4 and Myc and number of CTCs, while the control cells injected into mice developed only local fibrosis with high expression of aSMA. pLIX D141N tumors secreted CXCL16 into mice plasma, and were characterized by increased phosphorylation of c-Met, Src kinase and c-Myc. Conclusions: We believe that the MCPIP1 protein may be a marker of tumor initiation and play a key role in neoplastic transformation by regulating the changes in cell phenotype and levels of CSCs markers. This study was supported by National Science Center grants no. 2022/47/B/NZ5/02724, 2022/45/B/NZ5/01973 and MNS 15/2021. Citation Format: Paulina Marona, Iga Piasecka, Judyta Gorka, Oliwia Kwapisz, Rafal Myrczek, Ewelina Pospiech, Jolanta Jura, Katarzyna Miekus. Lack of MCPIP1 enzymatic activity leads to neoplastic transformation of normal kidney cells [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 3017.

The Crosstalk between N-Formyl Peptide Receptors and uPAR in Systemic Sclerosis: Molecular Mechanisms, Pathogenetic Role and Therapeutic Opportunities.

Systemic Sclerosis (SSc) is a heterogeneous autoimmune disease characterized by widespread vasculopathy, the presence of autoantibodies and the progressive fibrosis of skin and visceral organs. There are still many questions about its pathogenesis, particularly related to the complex regulation of the fibrotic process, and to the factors that trigger its onset. Our recent studies supported a key role of N-formyl peptide receptors (FPRs) and their crosstalk with uPAR in the fibrotic phase of the disease. Here, we found that dermal fibroblasts acquire a proliferative phenotype after the activation of FPRs and their interaction with uPAR, leading to both Rac1 and ERK activation, c-Myc phosphorylation and Cyclin D1 upregulation which drive cell cycle progression. The comparison between normal and SSc fibroblasts reveals that SSc fibroblasts exhibit a higher proliferative rate than healthy control, suggesting that an altered fibroblast proliferation could contribute to the initiation and progression of the fibrotic process. Finally, a synthetic compound targeting the FPRs/uPAR interaction significantly inhibits SSc fibroblast proliferation, paving the way for the development of new targeted therapies in fibrotic diseases.

Arecoline promotes Akt-c-Myc-driven aerobic glycolysis in esophageal epithelial cells.

Aerobic glycolysis is a typical metabolic rearrangement for tumorigenesis. Arecoline is of explicit carcinogenicity, numerous works demonstrate its mutagenicity, genotoxicity, and cytotoxicity. However, the effects of arecoline on aerobic glycolysis of esophageal epithelial cells remain unclear. In the present study, 5 μM arecoline efficiently increased HK2 expression to induce aerobic glycolysis in Het-1A-Are and NE2-Are cells. The mechanistic analysis showed that arecoline activated the Akt-c-Myc signaling pathway and reduced the GSK3β-mediated phosphorylation of c-Myc on Thr58 to prevent its ubiquitination and destruction, subsequently promoting HK2 transcription and expression. Taken together, these results suggest that arecoline can induce aerobic glycolysis of esophageal epithelial cells and further confirm that arecoline is a carcinogen harmful to human health.

Synergistic Anti-Tumor Effects in RAS Mut Multiple Myeloma By Targeting MAP4K2 and RAS Pathways

Mitogen-activated protein kinase kinase kinase kinase 2 (MAP4K2) is an important key regulator of the stress-activated MAPK core signaling pathways. Our previous work demonstrated that MAP4K2 is highly expressed in multiple myeloma (MM) cells, and MM cells carrying a RAS mutation are more vulnerable to MAP4K2 inhibition, associated with the downregulation of critical transcriptional factors including IKZF1/3, BCL-6, and c-MYC proteins ( Li et al. Blood 2021). Targeting the aberrant RAS/MAPK signaling, MEK inhibitors have been shown to induce cytotoxicity in MM (De la Puente, P. et al. Blood Cancer J. 2016). Thus, we used a recently developed MEK inhibitor (MEKi) Trametinib to investigate the therapeutic potential of combined MEK and MAP4K2 signaling inhibition in RAS-driven MM. Tet-on sh-MAP4K2 lentivirus was introduced into RAS Mut MM cells to establish the inducible MAP4K2 knockdown cells upon doxycycline treatment. To examine the combined effects, Tet-on sh-MAP4K2 RAS Mut MM cells were treated with doxycycline to silence MAP4K2 expression, followed by treatment of MEKi Trametinib at different dosages. Cell proliferation, apoptosis, and cell cycle were analyzed five days later. Data showed that MAP4K2 silencing combined with MEK inhibition significantly decreased cell proliferation to 10% compared with MEKi alone 32% ( p<0.01) by MTS assays, and enhanced cell apoptosis (MEKi alone vs. with MAP4K2 silencing: 26% vs 91%, p<0.01). Cell cycle assay demonstrated that MEKi induced G1 arrest in RAS Mut MM cells (MEKi alone:76% vs vehicle control: 54%, p<0.01), which was also significantly higher in combination with MAP4K2 silencing (92%). Western blot assay confirmed that MAP4K2 silencing combined with MEKi significantly enhanced the downregulation of IKZF1 and c-MYC compared to the MEKi treatment alone. These data suggest that the MEKi and MAP4K2 inhibition combination has synergetic anti-MM effects. To further confirm the synergetic effects, we tested the combined effects of MEKi with the MAP4K2 kinase inhibitor TL4-12. H929 (N-Ras Mut) cells were treated by vehicle control, TL4-12 (2 uM) alone, MEKi (200 nM) alone, or TL4-12 + MEKi for 4 days, followed by an apoptosis assay. The combination of TL4-12 and MEKi strongly enhanced the cytotoxicity effects compared to the single-agent treatments. Consistently, the carboxyfluorescein diacetate succinimidyl ester (CFSE) cell proliferation assay confirmed that dual treatment significantly delayed H929 cell proliferation compared to the single-agent treatments (percentage of proliferating cells: TL4-12 alone: 86.2%; MEKi alone: 89.03%; dual treatment: 18.9%. p<0.01). Western blotting assay further confirmed that dual treatment of MEKi and MAP4K2i enhanced the decrease in MEK1/2 and ERK1/2 phosphorylation and downregulation of transcriptional factors IKZF1 and c-MYC. Taken together, our findings demonstrate that the combination of MAP4K2 inhibition with MEKi results in synergetic anti-MM effects in RAS mutation myeloma, therefore could be a potent novel therapeutic regimen for patients with relapsed/refractory multiple myeloma.

The Novel CDK9/CDK4/6/PI3K Triple Inhibitor LCI139 for the Treatment of MYC-Driven Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is an aggressive B cell malignancy with characteristic t(11;14)(q13;q32) translocation juxtaposing IGH and CCND1 gene loci. This chromosomal rearrangement leads to Cyclin D1 overexpression and cell cycle dysregulation at the G1/S phase transition. MCL is generally diagnosed at advanced stages and follows an aggressive course of disease. Although chemotherapy-based combination regimens are initially effective, most patients relapse with a median survival of only 2.5-5 years. While novel targeted therapeutics have shown promising activity in relapsed/refractory patients, inevitable relapse associated with progressively declining efficacy and increasing resistance to single agent targeted therapy is a major concern. To overcome this barrier, we designed in-silico based a novel multitarget small molecule inhibitor LCI139 which simultaneously blocks three oncogenic targets: cyclin-dependent kinase 9 (CDK9), CDK4/6, and phosphatidylinositol-3 kinase (PI3K). LCI139 is a potent CDK9/CDK4/6/PI3K inhibitor with IC 50s of 0.000039µM (CDK9), 0.0015µM/0.0036µM (CDK4/6) 0.070µM (p110α), 0.461µM (p110γ), and 0.214 (p110δ), as determined by cell free assay alpha screens. Dose-dependent screening of LCI139 against a panel of MCL cell lines revealed robust cytotoxic effects with maximal IC 50 of 86.67 nM in JeKo-1 cells, 64.8 nM in Mino cells, and 202.5 nM in Rec-1 cells. Compared with clinical single agent CDK9 inhibitor AZD4573, LCI139 is less toxic to normal human stromal cells (HS-5), whereas both LCI139 and AZD4573 have no significant cytotoxic effect on normal human foreskin fibroblast cells (Hs68). LCI139 treatment at various concentrations for 24hrs induced significant apoptotic response in two MCL cell lines, JeKo-1 (p<0.001 DMSO vs LCI139 100 nM, p<0.0001 DMSO vs LCI139 200 nM) and Mino (p<0.05 DMSO vs LCI139 100 nM, p<0.0001 DMSO vs LCI139 200 nM) as determined by Annexin V/7-AAD apoptosis staining. Similarly, LCI139-induced apoptotic cell death was further confirmed by increasing cl-PARP protein levels compared to control as assessed by Western blot analysis. LCI139 induced robust G2/M cell cycle arrest in JeKo-1 cells and G1 arrest in Mino cells. The mechanism of action of pan-CDK inhibitors has been associated with downregulation of the anti-apoptotic protein MCL-1 through inhibition of transcriptional CDKs. Our results show that short-term exposure of LCI139 (1hr and 3hr) significantly suppressed MCL-1 and MYC mRNA expression in JeKo-1 (p<0.00001 DMSO vs LCI139) and Mino cells (p<0.00001 DMSO vs LCI139). LCI139 suppressed pRpb1 (Ser2), MCL-1 and cMYC protein expression in IgM-stimulated JeKo-1 and Mino cells in a dose-dependent manner. Treatment with LCI139 had no significant effect on pAKT (Ser473) in Jeko-1 cells, whereas pAKT (Ser473) was completely abolished in Mino cells at 500nM of LCI139. Mechanistically, our findings also demonstrate that LCI139 decreased MCL-1 and cMYC protein stability and reduced half-life as accessed by cycloheximide chase assay. This decrease in cMYC stability is associated with decreased of cMYC phosphorylation at Ser62. Adaptive kinome remodeling via drug-induced transcriptional reprogramming is a known contributor to ibrutinib resistant (IR) MCL. RNA-sequencing analysis of JeKo-1 vs Jeko-1 IR cells revealed a total of 3468 differentially expressed genes (FC > 1.5 and FDR < 0.05) where 110 kinases display altered expression in JeKo-1 IR cells. Finally, we show that LCI139 overcomes chronic ibrutinib resistance by decreasing viability in JeKO-1 IR and Mino IR cells with an IC 50 of 79 nM and 89 nM, respectively. Therefore, the multitarget small molecule inhibitor LCI139 has superior potency against IR MCL cell lines and overcomes ibrutinib-resistance at nanomolar doses.

Phosphorylated Hsp27 promotes adriamycin resistance in breast cancer cells through regulating dual phosphorylation of c-Myc

Chemotherapy resistance of breast cancer cells is one of the major factors affecting patient survival rate. Heat shock protein 27 (Hsp27) is a member of the small heat shock protein family that has been reported to be associated with chemotherapy resistance in tumor cells, but the exact mechanism is not fully understood. Here, we explored the regulation of Hsp27 in adriamycin-resistant pathological conditions of breast cancer in vitro and in vivo. We found that overexpression of Hsp27 in MCF-7 breast cancer cells reversed DNA damage induced by adriamycin, and thereby reduced subsequent cell apoptosis. Non-phosphorylated Hsp27 accelerated ubiquitin-mediated degradation of c-Myc under normal physiological conditions. After stimulation with adriamycin, Hsp27 was phosphorylated and translocated from the cytoplasm into the nucleus, where phosphorylated Hsp27 upregulated c-Myc and Nijmegen breakage syndrome 1 (NBS1) protein levels thus leading to ATM activation. We further showed that phosphorylated Hsp27 promoted c-Myc nuclear import and stabilization by regulating T58/S62 phosphorylation of c-Myc through a protein phosphatase 2A (PP2A)-dependent mechanism. Collectively, the data presented in this study demonstrate that Hsp27, in its phosphorylation state, plays a critical role in adriamycin-resistant pathological conditions of breast cancer cells.

Formyl-peptide receptor 2 signalling triggers aerobic metabolism of glucose through Nox2-dependent modulation of pyruvate dehydrogenase activity.

The human formyl-peptide receptor 2 (FPR2) is activated by an array of ligands. By phospho-proteomic analysis we proved that FPR2 stimulation induces redox-regulated phosphorylation of many proteins involved in cellular metabolic processes. In this study, we investigated metabolic pathways activated in FPR2-stimulated CaLu-6 cells. The results showed an increased concentration of metabolites involved in glucose metabolism, and an enhanced uptake of glucose mediated by GLUT4, the insulin-regulated member of GLUT family. Accordingly, we observed that FPR2 transactivated IGF-IRβ/IRβ through a molecular mechanism that requires Nox2 activity. Since cancer cells support their metabolism via glycolysis, we analysed glucose oxidation and proved that FPR2 signalling promoted kinase activity of the bifunctional enzyme PFKFB2 through FGFR1/FRS2- and Akt-dependent phosphorylation. Furthermore, FPR2 stimulation induced IGF-IRβ/IRβ-, PI3K/Akt- and Nox-dependent inhibition of pyruvate dehydrogenase activity, thus preventing the entry of pyruvate in the tricarboxylic acid cycle. Consequently, we observed an enhanced FGFR-dependent lactate dehydrogenase (LDH) activity and lactate production in FPR2-stimulated cells. As LDH expression is transcriptionally regulated by c-Myc and HIF-1, we demonstrated that FPR2 signalling promoted c-Myc phosphorylation and Nox-dependent HIF-1α stabilization. These results strongly indicate that FPR2-dependent signalling can be explored as a new therapeutic target in treatment of human cancers.

Lobetyolin inhibits cell proliferation and induces cell apoptosis by downregulating ASCT2 in gastric cancer.

Gastric cancer (GC) is a heterogeneous disease and is the fifth most common cancer worldwide. Lobetyolin, as a bioactive ingredient extracted from Codonopsis pilosula (Franch.) Nannf., has been reported to exert anti-tumor effects in several cancer types. This study was aimed to investigate the role of lobetyolin in GC and the associated mechanism. MKN-45 and MKN-28 cells were incubated with concentrations of lobetyolin for 24h. The viability and survival of GC cells were evaluated by performing MTT assay. Glutamine uptake, Adenosine Triphosphate, reactive oxygen species (ROS), and glutathione levels were measured by corresponding kits. Apoptosis and mitochondrial membrane potential of GC cells were determined by flow cytometry. Alanine, serine, cysteine-preferring transporter 2 (ASCT2) and the AKT/GSK3β/c-Myc pathway protein levels were examined by western blotting. Xenograft model and immunohistochemical staining were used to evaluate the pharmacological effects of lobetyolin in mice in vivo. We found that lobetyolin treatment suppressed the proliferative capacity of both MKN-45 and MKN-28 cells in a concentration-dependent manner. Lobetyolin reduced the uptake of glutamine and downregulated the expression levels of ASCT2 in GC cells and xenograft tumors. Lobetyolin effectively restrained the growth of tumors in vivo. In addition, lobetyolin induced the accumulation of ROS to attenuate mitochondria-mediated apoptosis via downregulation of ASCT2 expression. Lobetyolin promoted the phosphorylation of c-Myc and suppressed the phosphorylation of GSK3β and AKT in both MKN-45 and MKN-28 cells. The level of total Nrf2 protein was reduced after lobetyolin treatment. Overall, lobetyolin exerts anti-cancer effects by repressing cell proliferation and inducing cell apoptosis via downregulation of ASCT2 in GC.

Targeting Squalene Epoxidase Confers Metabolic Vulnerability and Overcomes Chemoresistance in HNSCC.

Cisplatin resistance poses a substantial hurdle in effectively treating head and neck squamous cell carcinoma (HNSCC). Utilizing multiple tumor models and examining an internal HNSCC cohort, squalene epoxidase (SQLE) is pinpointed as a key driver of chemoresistance and tumorigenesis, operating through a cholesterol-dependent pathway. Comprehensive transcriptomic analysis reveals that SQLE is essential for maintaining c-Myc transcriptional activity by stabilizing the c-Myc protein and averting its ubiquitin-mediated degradation. Mechanistic investigation demonstrates that SQLE inhibition diminishes Akt's binding affinity to lipid rafts via a cholesterol-dependent process, subsequently deactivating lipid raft-localized Akt, reducing GSK-3β phosphorylation at S9, and increasing c-Myc phosphorylation at T58, ultimately leading to c-Myc destabilization. Importantly, employing an Sqle conditional knockout mouse model, SQLE's critical role in HNSCC initiation and progression is established. The preclinical findings demonstrate the potent synergistic effects of combining terbinafine and cisplatin in arresting tumor growth. These discoveries not only provide novel insights into the underlying mechanisms of SQLE-mediated cisplatin resistance and tumorigenesis in HNSCC but also propose a promising therapeutic avenue for HNSCC patients unresponsive to conventional cisplatin-based chemotherapy.

Identification of antimycin A as a c-Myc degradation accelerator via high-throughput screening

c-Myc is a critical regulator of cell proliferation and growth. Elevated levels of c-Myc cause transcriptional amplification, leading to various types of cancers. Small molecules that specifically inhibit c-Myc-dependent regulation are potentially invaluable for anticancer therapy. Because c-Myc does not have enzymatic activity or targetable pockets, researchers have attempted to obtain small molecules that inhibit c-Myc cofactors, activate c-Myc repressors, or target epigenetic modifications to regulate the chromatin of c-Myc-addicted cancer without any clinical success. In this study, we screened for c-Myc inhibitors using a cell-dependent assay system in which the expression of c-Myc and its transcriptional activity can be inferred from monomeric Keima and enhanced GFP fluorescence, respectively. We identified one mitochondrial inhibitor, antimycin A, as a hit compound. The compound enhanced the c-Myc phosphorylation of threonine-58, consequently increasing the proteasome-mediated c-Myc degradation. The mechanistic analysis of antimycin A revealed that it enhanced the degradation of c-Myc protein through the activation of glycogen synthetic kinase 3 by reactive oxygen species (ROS) from damaged mitochondria. Furthermore, we found that the inhibition of cell growth by antimycin A was caused by both ROS-dependent and ROS-independent pathways. Interestingly, ROS-dependent growth inhibition occurred only in the presence of c-Myc, which may reflect the representative features of cancer cells. Consistently, the antimycin A sensitivity of cells was correlated to the endogenous c-Myc levels in various cancer cells. Overall, our study provides an effective strategy for identifying c-Myc inhibitors and proposes a novel concept for utilizing ROS inducers for cancer therapy.

WIF1 promoter hypermethylation induce endometrial carcinogenesis through the Wnt/β-catenin signaling pathway.

This study explores the mechanism underlying WIF1 promoter methylation and its relationship with the pathogenesis of endometrial carcinoma. WIF1 promoter methylation was detected using methylation-specific polymerase chain reaction (MSP). WIF1 expression was examined through qRT-PCR and western blotting. Furthermore, 5-aza-2'-deoxycytidine (5-Aza) was used to demethylate the WIF1 promoter. The roles of WIF1 were investigated using in vitro loss- and gain-of-function assays. Xenograft models were used to analyze WIF1 expression and downstream genes, and results were confirmed using immunofluorescence and western blotting. WIF1 promoter methylation in endometrial cancer cells was significantly higher than that in normal cells, but the WIF1 mRNA and protein levels were reduced. The expression of WIF1 increased significantly after 5-Aza treatment (p<.05). Thus, 5-Aza treatment can inhibit the proliferation of endometrial cancer cells and induce apoptosis, while knockdown of WIF1 significantly inhibits the effects of 5-Aza. 5-Aza treatment can also inhibit Wnt pathway genes, including phosphorylation of β-catenin protein, c-Myc, and CyclinD1, inhibit downstream functional genes, and activate the tumor suppressor gene APC, which can be blocked by WIF1 knockdown in endometrial carcinoma cells. Finally, 5-Aza inhibited the proliferation of subcutaneous tumor-bearing nude mice with endometrial cancer cells, but the effect was weaker than that of WIF1 overexpression. Our research shows that WIF1 promoter hypermethylation may promote the progression of endometrial cancer by downregulating WIF1 expression, activating the Wnt/β-catenin pathway, and promoting proliferation and inhibiting apoptosis. WIF1 may be a potential biological target for gene therapy and drug development for the treatment of endometrial cancer.

Characterization of a Distinct State in the Continuum of Pluripotency Facilitated by Inhibition of PKCζ in Mouse Embryonic Stem Cells.

Inhibition of PKC (PKCi) signaling maintains pluripotency of embryonic stem cells (ESCs) across different mammalian species. However, the position of PKCi maintained ESCs in the pluripotency continuum is largely unknown. Here we demonstrate that mouse ESCs when cultured continuously, with PKCi, for 75days are retained in naïve state of pluripotency. Gene expression analysis and proteomics studies demonstrated enhanced naïve character of PKCi maintained ESCs in comparison to classical serum/LIF (S/L) supported ESCs. Molecular analysis revealed that activation of PKCζ isoform associate with primed state of pluripotency, present in epiblast-like stem cells generated in vitro while inhibition of PKCζ phosphorylation associated with naïve state of pluripotency in vitro and in vivo. Phosphoproteomics and chromatin modification enzyme array based studies showed loss in DNA methyl transferase 3B (DNMT3B) and its phosphorylation level upon functional inhibition of PKCζ as one of the crucial components of this regulatory pathway. Unlike ground state of pluripotency maintained by MEK/GSK3 inhibitor in addition to LIF (2i/LIF), loss in DNMT3B is a reversible phenomenon in PKCi maintained ESCs. Absence of phosphorylation of c-MYC, RAF1, SPRY4 while presence of ERF, DUSP6, CIC and YAP1 phosphorylation underlined the phosphoproteomics signature of PKCi mediated maintenance of naïve pluripotency. States of pluripotency represent the developmental continuum and the existence of PKCi mediated mouse ESCs in a distinct state in the continuum of pluripotency (DiSCo) might contribute to the establishment of stages of murine embryonic development that were non-permissible till date.

S100A9 promotes glycolytic activity in HER2-positive breast cancer to induce immunosuppression in the tumour microenvironment

PurposeThe purpose of this study was to investigate the correlation between S100 calcium binding protein A9 (S100A9), tumour glycolysis and tumour infiltrating lymphocytes (TIL) in human epidermal growth factor receptor 2 (HER2) - positive breast cancer (BRCA). Materials and methodsA total of 667 BRCA patients in Xiangya Hospital of Central South University were enrolled in this study. Haematoxylin and eosin (H&E) staining were used to count TIN in tissues. Human breast cancer cell lines (SK-BR-3 cells and BT474 cells) were transfected with S100A9 specific small interfering RNA (siRNA). The expressions of S100A9, glycolytic enzymes and lymphocyte markers were detected by immunohistochemistry (IHC) staining, Western blot and immunofluorescence. Lactate production, glucose consumption and the extracellular acidification rate (ECAR) were detected to assess glycolysis activity. ResultsS100A9 was significantly overexpressed in HER2+ cases. The expressions of phosphoglycerol kinase 1 (PGK1), lactate dehydrogenase A (LDHA) and enolase α (ENO1) were significantly up-regulated in S100A9 dominant tissues. The expressions of PGK1, LDHA and ENO1 detected in S100A9 silenced cell lines were significantly down-regulated. Moreover, S100A9 silencing significantly altered lactate production, glucose uptake and ECAR levels in HER2+ cell lines. Co-expression of S100A9 and c-Myc was detected in HER2+ tissues. The absence of S100A9 greatly hindered β-catenin expression in cell lines, which later induced the phosphorylation of c-Myc.The amount of TILs in cases with abundant S100A9 and LDHA was much greater than in cases with low S100A9 levels and poorer LDHA. TIL deficiency and elevated S100A9 intensity are factors affecting the survival rate of HER2+ BRCA cases. ConclusionsS100A9 overexpression upregulated the glycolysis activity of tumour cells through the c-Myc-related pathway, suppressing lymphocyte infiltration in the tumour stroma, affecting the efficacy of immune regulation and long-term survival of patients.

Repurposed benzydamine targeting CDK2 suppresses the growth of esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is one of the leading causes of cancer death worldwide. It is urgent to develop new drugs to improve the prognosis of ESCC patients. Here, we found benzydamine, a locally acting non-steroidal anti-inflammatory drug, had potent cytotoxic effect on ESCC cells. Benzydamine could suppress ESCC proliferation in vivo and in vitro. In terms of mechanism, CDK2 was identified as a target of benzydamine by molecular docking, pull-down assay and in vitro kinase assay. Specifically, benzydamine inhibited the growth of ESCC cells by inhibiting CDK2 activity and affecting downstream phosphorylation of MCM2, c-Myc and Rb, resulting in cell cycle arrest. Our study illustrates that benzydamine inhibits the growth of ESCC cells by downregulating the CDK2 pathway.

Type IV collagen α5 chain promotes luminal breast cancer progression through c-Myc-driven glycolysis.

Cancer cell metabolism reprogramming is one of the hallmarks of cancer. Cancer cells preferentially utilize aerobic glycolysis, which is regulated by activated oncogenes and the tumor microenvironment. Extracellular matrix (ECM) in the tumor microenvironment, including the basement membranes (BMs), is dynamically remodeled. However, whether and how ECM regulates tumor glycolysis is largely unknown. We show that type IV collagens, components of BMs essential for the tissue integrity and proper function, are differentially expressed in breast cancer subtypes that α5 chain (α5(IV)) is preferentially expressed in the luminal-type breast cancer and is regulated by estrogen receptor-α. α5(IV) is indispensable for luminal breast cancer development. Ablation of α5(IV) significantly reduces the growth of luminal-type breast cancer cells and impedes the development of luminal-type breast cancer. Impaired cell growth and tumor development capability of α5(IV)-ablated luminal breast cancer cells is attributed to the reduced expression of glucose transporter and glycolytic enzymes and impaired glycolysis in luminal breast cancer cells. Non-integrin collagen receptor discoidin domain receptor-1 (DDR1) expression and p38 mitogen-activated protein kinase activation are attenuated in α5(IV)-ablated luminal breast cancer cells, resulting in reduced c-Myc oncogene expression and phosphorylation. Ectopic expression of constitutively active DDR1 or c-Myc restores the expression of glucose transporter and glycolytic enzymes, and thereafter restores aerobic glycolysis, cell proliferation, and tumor growth of luminal breast cancer. Thus, type IV collagen α5 chain is a luminal-type breast cancer-specific microenvironmental regulator modulating cancer cell metabolism.

MEDB-89. Elucidation of the Oncogenic role of Nuclear Factor I/B (NFIB) in group 3 medulloblastoma

Amongst the 4 subgroups of medulloblastoma (MB), tumors falling into group 3 are the most aggressive and associated with increased incidence of aberrations on chromosome 17p, c-Myc amplification, metastases at diagnosis, and rapid tumor relapse. Thus, patients with group 3 tumors suffer the worst prognosis with a 5-year survival rate of <50%. We have prior identified a novel tumor-suppressive microRNA, miR-212, silenced on chromosome 17p and its deregulated oncoprotein target, Nuclear Factor I/B (NFIB). Here, we sought to identify the role of NFIB in group 3 MB pathophysiology. NFIB is a transcription factor that regulates chromosomal gene accessibility and expression of pro-metastatic genes in various cancers. Transcriptomic interrogation of group 3 tumors revealed deregulated expression of NFIB. Kaplan-Meier survival analysis confirmed poorer survival in NFIB high-expressing patients. Using inducible silencing of NFIB in a classic group 3 MB cell line, HDMB03, we observed downregulation of key driver genes (49 genes, Log2 fold change < -0.5, p < 0.001) associated with group 3 MB pathogenesis by RNA sequencing. NFIB expression knockdown (NFIBKD) further reduced tumor cell growth and aggressiveness, as evidenced by reduced proliferation, colony formation, migration, and invasion. NFIBKD also affected group 3 MB stemness, with attenuation of medullospheres and a reduction in stem cell markers (Nanog, Oct4, Sox2, CD133). Moreover, NFIBKD destabilized c-Myc phosphorylation at serine-62, resulting in reduced total c-Myc levels and subsequent cellular apoptosis. Concurrently, NFIBKD decreased the expression of upstream activators of c-Myc such as p-Akt and p-Erk. Taken together, these results validate the oncogenic role of NFIB in group 3 medulloblastomas and provide a potential new therapeutic target.

Oct4 facilitates chondrogenic differentiation of mesenchymal stem cells by mediating CIP2A expression.

Bone development and cartilage formation require strict modulation of gene expression for mesenchymal stem cells (MSCs) to progress through their differentiation stages. Octamer-binding transcription factor 4 (Oct4) expression is generally restricted to developing embryonic pluripotent cells, but its role in chondrogenic differentiation (CD) of MSCs remains unclear. We therefore investigated the role of Oct4 in CD using a microarray, quantitative real-time polymerase chain reaction, and western blotting. The expression of Oct4 was elevated when the CD of cultured MSCs was induced. Silencing Oct4 damaged MSC growth and proliferation and decreased CD, indicated by decreased cartilage matrix formation and the expression of Col2a1, Col10a1, Acan, and Sox9. We found a positive correlation between the expression of CIP2A, a natural inhibitor of protein phosphatase 2A (PP2A) and that of Oct4. Cellular inhibitor of PP2A (CIP2A) expression gradually increased after CD. Overexpression of CIP2A in MSCs with Oct4 depletion promoted cartilage matrix deposition as well as Col2a1, Col10a1, Acan, and Sox9 expression. The chondrogenic induction triggered c-Myc, Akt, ERK, and MEK phosphorylation and upregulated c-Myc and mTOR expression, which was downregulated upon Oct4 knockdown and restored by CIP2A overexpression. These findings indicated that Oct4 functions as an essential chondrogenesis regulator, partly via the CIP2A/PP2A pathway.