c-Myc Inhibitor Research Articles

Abstract 1218: CDK9 inhibitors modulate the transcriptional landscape of colorectal cancer to suppress MAPK signaling and synergizes with BRAF inhibitors to treat BRAF-mutant colorectal cancer

Abstract Background: Colorectal cancer (CRC) is the second leading cause of cancer deaths in the US, and it remains a significant public health burden. Metastatic CRC (mCRC) is usually treated with combination chemotherapy and targeted therapy regimens, but eventually becomes chemotherapy refractory. Thus, novel and more effective treatments for mCRC are urgently needed. Cyclin-dependent kinase 9 (CDK9) is a key activator of RNA Pol II transcription and promotes the expression of many cancer driver genes, making CDK9 a promising target for cancer therapy. Methods: Human CRC cell lines, patient-derived organoids (PDOs), cell line xenografts, and patient-derived xenografts were used to investigate the efficacy and mechanisms of action of the CDK9 inhibitors AZD4573, enitociclib, and NVP-2, as well as the BRAF inhibitors encorafenib and dabrafenib. In vitro viability was measured by chemical cell proliferation assays and in vivo tumor sizes were measured by calipers. In vitro mechanisms of action were assessed by RNA sequencing, real time polymerase chain reaction, and Western blotting. In vivo mechanisms of action were assessed by immunohistochemistry. Results: CDK9 inhibitors potently inhibited CRC cells and PDOs. In contrast to hematologic malignancies, we did not observe consistent suppression of the oncogenes c-MYC and MCL-1 by CDK9 inhibitor treatment. Instead, CDK9 inhibitors suppressed several other key cancer pathways in CRC, such as MAPK, mTOR, and PI3K signaling pathways. Importantly, multiple targets within the MAPK pathway were strongly suppressed, including EGFR, KRAS, and BRAF. We hypothesized that combination treatment with CKD9 inhibitors and MAPK pathway inhibitors can synergistically treat CRC. As proof-of-concept, we investigated the combination of CDK9 and BRAF inhibitors in models of BRAF-mutant CRC, a particularly aggressive type of CRC. We found this combination to synergistically suppress CRC growth in vitro and in vivo. Compared to single agents, combination treatment led to significantly stronger induction of apoptosis and suppression of MAPK pathway signaling. Our results suggest that concurrent treatment with CDK9 inhibitors plus established MAPK pathway inhibitors, such as BRAF inhibitors, can significantly improve upon single agent treatment. Conclusions: We have found CDK9 inhibitors to potently suppress CRC growth and survival through a unique mechanism of action, by vertical suppression of the MAPK signaling pathway. We demonstrate that CDK9 inhibitors can synergize with BRAF inhibitors in the treatment of BRAF-mutant CRC models. Thus, CDK9 inhibitors are a promising class of drugs warranting further investigation, including early-phase clinical trials, in mCRC. Citation Format: Chaoyuan Kuang, Ning Wei, Mahshid Mohammadi, Muzaffer A. Bhat, Terence Li, Priyanka Patil, Othon Wiltz, Renee Huang, Kohtaro Ooka, Melanie Quintal, Edward Chu. CDK9 inhibitors modulate the transcriptional landscape of colorectal cancer to suppress MAPK signaling and synergizes with BRAF inhibitors to treat BRAF-mutant colorectal cancer [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 1218.

Inhibition of the MALT1-LPCAT3 axis protects cartilage degeneration and osteoarthritis

The proinflammatory cytokines and arachidonic acid (AA)-derived eicosanoids play a key role in cartilage degeneration in osteoarthritis (OA). The lysophosphatidylcholine acyltransferase 3 (LPCAT3) preferentially incorporates AA into the membranes. Our recent studies showed that MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that LPCAT3 expression was up-regulated in both human and mice articular cartilage of OA, and correlated with severity of OA. The IL-1β-induces cell death via upregulation of LPCAT3, MMP3, ADAMTS5, and eicosanoids via MALT1. Gene silencing or pharmacological inhibition of LPCAT3 or MALT1 in chondrocytes and human cartilage explants notably suppressed the IL-1β-induced cartilage catabolism through inhibition of expression of MMP3, ADAMTS5, and also secretion of cytokines and eicosanoids. Mechanistically, overexpression of MALT1 in chondrocytes significantly upregulated the expression of LPCAT3 along with MMP3 and ADAMTS5 via c-Myc. Inhibition of c-Myc suppressed the IL-1β-MALT1-dependent upregulation of LPCAT3, MMP3 and ADAMTS5. Consistent with the in vitro data, pharmacological inhibition of MALT1 or gene silencing of LPCAT3 using siRNA-lipid nanoparticles suppressed the synovial articular cartilage erosion, pro-inflammatory cytokines, and eicosanoids such as PGE2, LTB4, and attenuated osteoarthritis induced by the destabilization of the medial meniscus in mice. Overall, our data reveal a previously unrecognized role of the MALT1-LPCAT3 axis in osteoarthritis. Targeting the MALT1-LPCAT3 pathway with MALT1 inhibitors or siRNA-liposomes of LPCAT3 may become an effective strategy to treat OA by suppressing eicosanoids, matrix-degrading enzymes, and proinflammatory cytokines.Graphical

Abstract 5587: Regulator of chromosome condensation 1 (RCC1) as a novel therapeutic target in pancreatic ductal adenocarcinoma

Abstract Background and Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with limited treatment options. There is an urgent need for the identification of novel therapeutic targets for PDAC. The transport of molecular cargo between the nucleus and cytoplasm, facilitated by Ran-GTPase, is a critical process that dividing cells rely on to maintain their growth. Elevated nuclear Ran-GTP levels are produced by the activity of the Ran guanine nucleotide exchange factor (GEF) known as Regulator of Chromosome Condensation 1 (RCC1), which is found in the nucleus bound to chromatin. This creates a Ran-GTP gradient across the nuclear membrane, which maintains proper directional transport of proteins and RNA. To sustain proliferative signaling, cancer cells become reliant on high rates of nucleocytoplasmic transport through dysregulation of transport machinery. Methods: We examined the role of RCC1 in the biology of PDAC. The impact of RCC1 modulation on PDAC growth was evaluated using RNA interference and CRISPR-Cas9 in vitro and in vivo using PDAC cell lines and LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx1-Cre (KPC) tumor-derived cells. The broader impact of RCC1 silencing on PDAC-sustaining signaling was evaluated through RNA-sequencing and proteomics. Results: Transcriptomic sequencing of PDAC tissue (n=5,071) as well as analysis of publicly available data from the TCGA, CPTAC and GTEx revealed that RCC1 expression is higher in PDAC tissues compared to normal pancreas. Moreover, PDAC patients with higher RCC1 expression were more likely to have poorer outcomes. RCC1 silencing by RNAi and CRISPR-Cas9 resulted in reduced proliferation in 2D and 3D cultures and attenuated tumor growth in vivo. RCC1 KD decreased migration and colony formation, enhanced apoptosis, and altered the cell cycle in human and KPC mouse PDAC cells. Subcutaneous RCC1 KO cell line-derived xenografts show arrested growth. Subcellular Ran distribution was disrupted upon RCC1 KO, suggesting that nuclear Ran concentration is important for PDAC proliferation. Nuclear and cytosolic proteomic analysis revealed altered subcellular proteome in RCC1 KD KPC tumor-derived cells. Altered cytoplasmic protein pathways include several metabolic pathways, PI3K-AKT, and Hedgehog signaling. Nuclear enriched pathways include cell cycle, mitosis, metabolic processes, and RNA processing. RNA-seq of RCC1 KO cells showed widespread transcriptional alterations. Upstream of RCC1, c-MYC activates the RCC1-RAN axis, and RCC1 KO cells show differential sensitivity to c-MYC inhibitors. Finally, RCC1 KD resulted in the sensitization of PDAC cells to Gemcitabine. Molecular characterization of conditional Rcc1fl/fl KO transgenic model to study the role of RCC1 in PDAC in vivo is ongoing. Conclusions: Overall, our results show that RCC1 is involved in the regulation of PDAC growth and is a potential target for therapy. Citation Format: Sahar F. Bannoura, Husain Y. Khan, Amro Aboukameel, Md Hafiz Uddin, Rund Nimri, Eliza Beal, Seongho Kim, Mohammed Najeeb Al Hallak, Bassel El-Rayes, Philip A. Philip, Boris Pasche, Ramzi Mohammad, Asfar S. Azmi. Regulator of chromosome condensation 1 (RCC1) as a novel therapeutic target in pancreatic ductal adenocarcinoma [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 5587.

EIF2Ss, a Novel c-Myc-Correlated Gene Family, is Associated with Poor Prognosis and Immune Infiltration in Pancreatic Adenocarcinoma.

Pancreatic adenocarcinoma (PAAD) is a highly malignant tumor in urgent need of novel diagnostics, prognostic markers, and treatments. Eukaryotic translation initiation factor 2 subunits (EIF2Ss), comprising Eukaryotic translation initiation factor 2 subunit alpha (EIF2S1), Eukaryotic translation initiation factor 2 subunit beta (EIF2S2), and Eukaryotic translation initiation factor 2 subunit gamma (EIF2S3), is a family of eukaryotic initiation factors that participate in early protein synthesis and are crucial for tumor initiation and progression. However, the role of EIF2Ss in PAAD has yet to be reported. The aim of this study was therefore to analyze EIF2Ss in relation to the diagnosis, prognosis, and treatment of PAAD. The cancer genome atlas (TCGA) database was used to investigate gene expression and patient survival. Gene alterations, immune cell infiltration, and immune checkpoints in PAAD were also evaluated. Univariate and multivariate analysis, nomograms, calibration curves, and Decision Curve Analysis (DCA) diagrams were used to develop and evaluate a prediction model for patient outcome. Single-cell RNA-seq (scRNA) analysis, functional enrichment, co-IP assay, mass spectrometry, and western blot were used to study the relationship between EIF2Ss and c-myc in PAAD. EIF2Ss are over-expressed in PAAD tissue and are associated with poor prognosis. The frequency of EIF2S1, EIF2S2, and EIF2S3 gene alteration in PAAD was 0.2%, 0.4%, and 0.2%, respectively. High EIF2Ss expression was associated with Th2 cell infiltration, whereas low expression was associated with pDC infiltration. Moreover, EIF2Ss expression was positively correlated with the expression of the NT5E, ULBP1, PVR, CD44, IL10RB, and CD276 checkpoints. A prediction model developed using EIF2Ss and important clinicopathologic features showed good predictive value for the overall survival of PAAD patients. ScRNA-Seq data showed that EIF2Ss was associated with enrichment for endothelial cells, fibroblasts, malignant cells, and ductal cells. EIF2Ss expression was also correlated with adipogenesis, interferon-alpha response, epithelial-mesenchymal transition, myc targets, G2M checkpoint, oxidative phosphorylation, and hypoxia. Functional enrichment analysis of EIF2Ss showed a close correlation with the myc pathway, and interactions between EIF2Ss and c-myc were confirmed by co-IP assay and mass spectrometry. Importantly, knockdown of c-myc decreased the expression of EIF2S1, EIF2S2, and EIF2S3 in PAAD cells. EIF2Ss were found to have significant clinical implications for the prognosis and treatment of PAAD. Inhibition of c-myc caused the downregulation of EIF2S1, EIF2S2, and EIF2S3 expression.

C-Myc Drives inflammation of the maternal-fetal interface, and neonatal lung remodeling induced by intra-amniotic inflammation.

Background: Intra-amniotic inflammation (IAI) is associated with increased risk of preterm birth and bronchopulmonary dysplasia (BPD), but the mechanisms by which IAI leads to preterm birth and BPD are poorly understood, and there are no effective therapies for preterm birth and BPD. The transcription factor c-Myc regulates various biological processes like cell growth, apoptosis, and inflammation. We hypothesized that c-Myc modulates inflammation at the maternal-fetal interface, and neonatal lung remodeling. The objectives of our study were 1) to determine the kinetics of c-Myc in the placenta, fetal membranes and neonatal lungs exposed to IAI, and 2) to determine the role of c-Myc in modulating inflammation at the maternal-fetal interface, and neonatal lung remodeling induced by IAI. Methods: Pregnant Sprague-Dawley rats were randomized into three groups: 1) Intra-amniotic saline injections only (control), 2) Intra-amniotic lipopolysaccharide (LPS) injections only, and 3) Intra-amniotic LPS injections with c-Myc inhibitor 10058-F4. c-Myc expression, markers of inflammation, angiogenesis, immunohistochemistry, and transcriptomic analyses were performed on placenta and fetal membranes, and neonatal lungs to determine kinetics of c-Myc expression in response to IAI, and effects of prenatal systemic c-Myc inhibition on lung remodeling at postnatal day 14. Results: c-Myc was upregulated in the placenta, fetal membranes, and neonatal lungs exposed to IAI. IAI caused neutrophil infiltration and neutrophil extracellular trap (NET) formation in the placenta and fetal membranes, and neonatal lung remodeling with pulmonary hypertension consistent with a BPD phenotype. Prenatal inhibition of c-Myc with 10058-F4 in IAI decreased neutrophil infiltration and NET formation, and improved neonatal lung remodeling induced by LPS, with improved alveolarization, increased angiogenesis, and decreased pulmonary vascular remodeling. Discussion: In a rat model of IAI, c-Myc regulates neutrophil recruitment and NET formation in the placenta and fetal membranes. c-Myc also participates in neonatal lung remodeling induced by IAI. Further studies are needed to investigate c-Myc as a potential therapeutic target for IAI and IAI-associated BPD.

LINC00460-FUS-MYC feedback loop drives breast cancer metastasis and doxorubicin resistance.

Therapeutic resistance and metastasis largely contribute to mortality from breast cancer and therefore understanding the underlying mechanisms of such remains an urgent challenge. By cross-analysis of TCGA and GEO databases, LINC00460 was identified as an oncogenic long non-coding RNA, highly expressed in Doxorubicin resistant breast cancer. LINC00460 was further demonstrated to promote stem cell-like and epithelial-mesenchymal transition (EMT) characteristics in breast cancer cells. LINC00460 interacts with FUS protein with consequent enhanced stabilization, which further promotes MYC mRNA maturation. LINC00460 expression was transcriptionally enhanced by c-MYC protein, forming a positive feedback loop to promote metastasis and Doxorubicin resistance. LINC00460 depletion in Doxorubicin-resistant breast cancer cells restored sensitivity to Doxorubicin and increased the efficacy of c-MYC inhibitor therapy. Collectively, these findings implicate LINC00460 as a promising prognostic biomarker and potential therapeutic target to overcome Doxorubicin resistance in breast cancer.

Selective CDK7 Inhibition Suppresses Cell Cycle Progression and MYC Signaling While Enhancing Apoptosis in Therapy-resistant Estrogen Receptor-positive Breast Cancer.

Resistance to endocrine therapy (ET) and CDK4/6 inhibitors (CDK4/6i) is a clinical challenge in estrogen receptor (ER)-positive (ER+) breast cancer. Cyclin-dependent kinase 7 (CDK7) is a candidate target in endocrine-resistant ER+ breast cancer models and selective CDK7 inhibitors (CDK7i) are in clinical development for the treatment of ER+ breast cancer. Nonetheless, the precise mechanisms responsible for the activity of CDK7i in ER+ breast cancer remain elusive. Herein, we sought to unravel these mechanisms. We conducted multi-omic analyses in ER+ breast cancer models in vitro and in vivo, including models with different genetic backgrounds. We also performed genome-wide CRISPR/Cas9 knockout screens to identify potential therapeutic vulnerabilities in CDK4/6i-resistant models. We found that the on-target antitumor effects of CDK7 inhibition in ER+ breast cancer are in part p53 dependent, and involve cell cycle inhibition and suppression of c-Myc. Moreover, CDK7 inhibition exhibited cytotoxic effects, distinctive from the cytostatic nature of ET and CDK4/6i. CDK7 inhibition resulted in suppression of ER phosphorylation at S118; however, long-term CDK7 inhibition resulted in increased ER signaling, supporting the combination of ET with a CDK7i. Finally, genome-wide CRISPR/Cas9 knockout screens identified CDK7 and MYC signaling as putative vulnerabilities in CDK4/6i resistance, and CDK7 inhibition effectively inhibited CDK4/6i-resistant models. Taken together, these findings support the clinical investigation of selective CDK7 inhibition combined with ET to overcome treatment resistance in ER+ breast cancer. In addition, our study highlights the potential of increased c-Myc activity and intact p53 as predictors of sensitivity to CDK7i-based treatments.

Abstract B070: Myc synthetic lethality as a therapeutic strategy for resistance: Insights into the targetability of mitochondrial complex I in Myc-high TNBC

Abstract Patients with advanced triple-negative breast cancer (TNBC) frequently develop chemoresistance, emphasizing an urgent need for novel therapeutic strategies able to eradicate treatment resistant tumor cells. Recent studies have highlighted MYC as a common oncogenic alteration and a driver of stem-like TNBC phenotype, which commonly features high mitochondrial respiratory activity instated through OXPHOS system and chemoresistance. Interestingly, emerging evidence suggests that residual tumors from chemo treatment remain susceptible to OXPHOS inhibition through inhibition of respiratory complex I. Our previous studies have revealed a specific MYC-dependent and tumor suppressive synthetic lethal action for combination of metformin and BH3 mimetics in cells, ex vivo and in vivo models of aggressive breast cancer (PMID: 30728358). Metformin is a systemic and local metabolic modulator, which acts as a weak complex I inhibitor and promoter of AMPK activation. Here, we have explored the role of MYC in OXPHOS regulation, to address the question if metformin specifically and lethally targets MYC-modulated OXPHOS in MYC-high TNBC. We found that a selective c-MYC inhibitor (EN4) leads to a significant decrease in complex I activity despite only a modest drop in complex I mass in endogenously MYC-high TNBC cell lines. Conversely, engineered MYC overexpression in these cells upregulated complex I activity. Our current work explores transcriptomic, proteomic, and functional approaches to the mechanisms through which MYC regulates complex I activity, structure, and dynamics, ultimately hoping to define a biological rationale for therapeutic targeting of OXPHOS in Myc-high TNBC. Citation Format: Antti O Hiltunen, Linda J Id, Juha Klefström. Myc synthetic lethality as a therapeutic strategy for resistance: Insights into the targetability of mitochondrial complex I in Myc-high TNBC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B070.

KIF20A Promotes CRC Progression and the Warburg Effect through the C-Myc/HIF-1α Axis.

Colorectal cancer (CRC) is a prevalent form of cancer globally, characterized by a high mortality rate. Therefore, discovering effective therapeutic approaches for CRC treatment is critical. The levels of KIF20A in CRC clinical samples were determined using Western Blot and immunofluorescence assay. SW480 cells were transfected with siRNA targeting KIF20A, while HT-29 cells were transfected with a KIF20A overexpression vector. Cell viability and apoptosis of CRC cells were assessed using CCK-8 and TUNEL analysis. Migration ability was investigated using Transwell. The levels of pyruvate, lactate and ATP were determined through corresponding assay kits. Western Blot was applied to confirm the level of proteins associated with glycolysis, c- Myc, HIF-1α, PKM2 and LDHA. Subsequently, functional rescue experiments were conducted to investigate further the regulatory relationship between KIF20A, c-Myc, and HIF-1α in colorectal cancer (CRC), employing the c-Myc inhibitor 10058-F4 and c-Myc overexpression plasmids. KIF20A was up-regulated in vivo and in vitro in CRC. KIF20A knockdown inhibited cell viability and migration while promoting cell apoptosis in SW480 cells. Conversely, overexpression of KIF20A yielded contrasting effects in HT-29 cells. Moreover, inhibition of KIF20A restrained the pyruvate, lactate production and ATP level, whereas overexpression of KIF20A enhanced the Warburg effect. Western Blot indicated that knockdown KIF20A attenuated the levels of c-Myc, HIF-1α, PKM2 and LDHA. In addition, rescue experiments further verified that KIF20A enhanced the Warburg effect by the KIF20A/c-Myc/HIF-1α axis in CRC. KIF20A, being a crucial regulator in the progression of CRC, has the potential to be a promising therapeutic target for the treatment of CRC.

Chemotherapy-Enabled Colorectal Cancer Immunotherapy of Self-Delivery Nano-PROTACs by Inhibiting Tumor Glycolysis and Avoiding Adaptive Immune Resistance.

The chemo-regulation abilities of chemotherapeutic medications are appealing to address the low immunogenicity, immunosuppressive lactate microenvironment, and adaptive immune resistance of colorectal cancer. In this work, the proteolysis targeting chimera (PROTAC) of BRD4 (dBET57) is found to downregulate colorectal cancer glycolysis through the transcription inhibition of c-Myc, which also inhibits the expression of programmed death ligand 1 (PD-L1) to reverse immune evasion and avoid adaptive immune resistance. Based on this, self-delivery nano-PROTACs (designated as DdLD NPs) are further fabricated by the self-assembly of doxorubicin (DOX) and dBET57 with the assistance of DSPE-PEG2000. DdLD NPs can improve the stability, intracellular delivery, and tumor targeting accumulation of DOX and dBET57. Meanwhile, the chemotherapeutic effect of DdLD NPs can efficiently destroy colorectal cancer cells to trigger a robust immunogenic cell death (ICD). More importantly, the chemo-regulation effects of DdLD NPs can inhibit colorectal cancer glycolysis to reduce the lactate production, and downregulate the PD-L1 expression through BRD4 degradation. Taking advantages of the chemotherapy and chemo-regulation ability, DdLD NPs systemically activated the antitumor immunity to suppress the primary and metastatic colorectal cancer progression without inducing any systemic side effects. Such self-delivery nano-PROTACs may provide a new insight for chemotherapy-enabled tumor immunotherapy.

Dual inhibition of atypical PKC signaling and PI3K/Akt signaling dysregulates c-Myc to induce apoptosis in clear cell Renal Cell Carcinoma.

Renal Cell Carcinoma (RCC) is the most common type of kidney cancer (85%). 75% of the RCC cases involve conventional clear cell RCC (ccRCC). Approximately, 39% of late-stage patients (stage IV) are treated with chemotherapeutic agents. Phosphatidylinositol-3-kinase (PI3K) and Mitogen-Activated Protein Kinase Kinase (MEK)/extracellular signal-regulated kinase (ERK1/2) pathways are frequently activated in RCC. In addition, atypical PKCs (PKC-ί and PKC ζ) are overexpressed in most cancer cells, and they play a central role in tumor progression and the metastasis of different types of cancers. Our goal is to establish the role of aPKCs in the regulation of multiple key activated pathways in ccRCC. In this study, we also established a novel therapeutic regimen for dual inhibition of key activated pathways. In this study, 786-0 and Caki-1 cells were studied and subjected to cell viability assay, western blot analysis, scratch & wound healing assay, transwell invasion assay, immunofluorescence, immunoprecipitation, flow cytometry, and quantitative real-time polymerase chain reaction. We used combination of PI3K inhibitor- Alpelisib (BYL719) and ICA-1 (a PKC-ι-specific 5-amino-1-2,3-dihydroxy-4-(methylcyclopentyl)-1H-imidazole-4-carboxamide). In addition to drug treatment, small interfering RNA (siRNA) technology was used to further confirm the experimental outcome of the drug treatment. Our results suggest that treatment of ccRCC cells with a combination of ICA-1 (aPKC inhibitor) and BYL719 (PI3K inhibitor) downregulates PKC-ί and causes downstream inhibition of c-Myc. Inhibition of the PKCί also reduces activation of MEK/ERK1/2. It is observed that treatment with ICA-1 disrupts the level of the aPKC-Akt1 association. ICA-1 treatment also shows a reduced level of association between aPKC and c-Myc. The inhibition of aPKCs and downstream effector proteins by combination therapy is more pronounced compared to a single therapy. These effects contribute to reduced cell growth, and eventually, the induction of apoptosis. The decreased level of N-cadherin, p-vimentin, and vimentin and the increased level of E-cadherin confirm reduced malignancy. Therefore, implementing a combination of Alpelisib and a PKC-ι inhibitor is an effective approach to reducing cell proliferation, and invasion that eventually induces apoptosis and may be considered as a potential therapeutic option in ccRCC.

Deubiquitinase OTUB1 regulates doxorubicin-induced cardiotoxicity via deubiquitinating c-MYC.

Doxorubicin (DOX), an anthracycline drug widely used in antitumor therapies, has dose-dependent toxicity that can cause cardiomyocyte apoptosis and oxidative stress, thus limiting its clinical application. OTUB1 (ovarian tumor associated proteinase B1) is an OTU superfamily deubiquitinase that effectively regulates cell proliferation, inflammatory responses, apoptosis, and oxidative stress by specifically removing K48- and K63-linked ubiquitination; however, its role in DOX-induced cardiotoxicity remains unknown. A DOX-induced subacute cardiotoxicity mouse model was established by intraperitoneal injection, and cardiac injury was assessed by echocardiography, serum cardiac markers, and histopathological staining. Western blotting, qRT-PCR, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) immunohistochemistry were used to analyze cell apoptosis, tissue oxidative stress was assessed by superoxide dismutase (SOD) activity, malondialdehyde (MDA), and glutathione peroxidase (GSH-PX) activity. Cell counting kit-8 (CCK-8) assay, TUNEL staining, Western blotting, qRT-PCR, and reactive oxygen species (ROS) flow cytometry were applied on isolated neonatal mice cardiomyocytes to assess apoptosis and oxidative stress. Differentially expressed genes were analyzed using RNA sequencing and clustering analyses. c-MYC inhibitor 10,058-F4 and siRNA targeting c-Myc were used to investigate the roles of c-MYC in OTUB1's regulations of DOX-induced cardiotoxicity. Immunoprecipitation and Western blotting were performed to reveal the deubiquitinating effects of OTUB1 on c-MYC expression. We found that global Otub1-knockdown in vivo alleviated the subacute DOX treatment-induced cardiac dysfunction, fibrosis, and cardiomyocyte atrophy. Mechanistically, unbiased RNA sequencing and molecular biology experiments revealed that cardiomyocyte apoptosis, inflammation, and oxidative stress in DOX-induced cardiotoxicity were significantly compromised in the Otub1-knockdown group. Further in vitro studies have shown that c-MYC, a critical regulator of apoptosis, is indispensable in OTUB1's regulations of DOX-induced cardiotoxicity. Deubiquitinating effects of OTUB1 on K48- and K63-linked ubiquitination of c-MYC protein are essential for promoting cardiomyocyte apoptosis and oxidative responses. OTUB1-c-MYC inhibition protected cardiomyocytes against DOX-induced apoptosis and oxidative stress, suggesting that OTUB1 is a potential translational therapeutic target for preventing DOX-induced cardiotoxicity.

Antitumor efficacy of a sequence-specific DNA-targeted γPNA-based c-Myc inhibitor

Targeting oncogenes at the genomic DNA level can open new avenues for precision medicine. Significant efforts are ongoing to target oncogenes using RNA-targeted and protein-targeted platforms, but no progress has been made to target genomic DNA for cancer therapy. Here, we introduce a gamma peptide nucleic acid (γPNA)-based genomic DNA-targeted platform to silence oncogenes invivo. γPNAs efficiently invade the mixed sequences of genomic DNA with high affinity and specificity. As a proof of concept, we establish that γPNA can inhibit c-Myc transcription in multiple cell lines. We evaluate the invivo efficacy and safety of genomic DNA targeting in three pre-clinical models. We also establish that anti-transcription γPNA in combination with histone deacetylase inhibitors and chemotherapeutic drugs results in robust antitumor activity in cell-line- and patient-derived xenografts. Overall, this strategy offers a unique therapeutic platform to target genomic DNA to inhibit oncogenes for cancer therapy.

A recurrent de novo MAX p.Arg60Gln variant causes a syndromic overgrowth disorder through differential expression of c-Myc target genes

Cyclin D2 (CCND2) stabilization underpins a range of macrocephaly-associated disorders through mutation of CCND2 or activating mutations in upstream genes encoding PI3K-AKT pathway components. Here, we describe three individuals with overlapping macrocephaly-associated phenotypes who carry the same recurrent de novo c.179G>A (p.Arg60Gln) variant in Myc-associated factor X (MAX). The mutation, located in the b-HLH-LZ domain, causes increased intracellular CCND2 through increased transcription but it does not cause stabilization of CCND2. We show that the purified b-HLH-LZ domain of MAXArg60Gln (Max∗Arg60Gln) binds its target E-box sequence with a lower apparent affinity. This leads to a more efficient heterodimerization with c-Myc resulting in an increase in transcriptional activity of c-Myc in individuals carrying this mutation. The recent development of Omomyc-CPP, a cell-penetrating b-HLH-LZ-domain c-Myc inhibitor, provides a possible therapeutic option for MAXArg60Gln individuals, and others carrying similar germline mutations resulting in dysregulated transcriptional c-Myc activity.

The Aurora kinase inhibitor AT9283 inhibits Burkitt lymphoma growth by regulating Warburg effect

Objective To investigate the effect of the kinase inhibitor AT9283 on Burkitt lymphoma (BL) cells and elucidate the underlying mechanisms. Methods The effect of AT9283 on the proliferation of BL cell lines was tested using the MTT assay. Apoptosis and cell cycle were measured by flow cytometry. The proteins associated with the cell cycle, apoptosis, and the Warburg effect were detected using Western blotting. Alterations in glycolytic metabolism in terms of glucose intake and lactate concentrations were determined by glucose and lactate assays. Results The current study utilized the GEPIA, the Human Protein Atlas (HAP) database and immunohistochemistry to conduct analyses, which revealed a high expression of Aurora kinases and Warburg effect-related proteins in malignant B-cell lymphoma tissues. AT9283 significantly inhibited the cell proliferation of BL cells and induced G2/M arrest. Additionally, AT9283 induced apoptosis in BL cells and reversed the Warburg effect by increasing glucose uptake and reducing lactate production. Moreover, the protein expression of hexokinase 2, pyruvate kinase M2, and lactate dehydrogenase A was significantly suppressed by AT9283, possibly through the inhibition of c-Myc and HIF-1α protein expression. Conclusion The reversal of the Warburg effect in BL cells and the subsequent inhibition of cell proliferation and induction of apoptosis were observed by targeting Aurora A and Aurora B with AT9283. This finding may present new therapeutic options and targets for BL.

4,8-Dicarboxyl-8,9-iridoid-1-glycoside inhibits apoptosis in human osteoarthritis chondrocytes via enhanced c-MYC-mediated cholesterol metabolism in vitro

BackgroundOsteoarthritis (OA) is a degenerative disease related to cholesterol metabolism disorders. However, current therapies for OA are insufficient and no convincing disease-modifying OA drugs exist. Therefore, we aimed to elucidate the mechanism by which borojoa iridoid glycoside (BIG) inhibits chondrocyte apoptosis in OA.MethodsBorojoa pulp was heated to 70 °C, and the main active substance in borojoa, BIG, was extracted by fractionation at an ultraviolet 254-nm absorption peak. Chondrocytes were identified by immunohistochemistry and visualized by immunofluorescence confocal microscopy. The proliferation of chondrocytes cultured with BIG was determined by MTS assay. The apoptosis of chondrocytes cultured with BIG was tested by Annexin V-FITC/PI, and the cytokine, protein, and cholesterol levels in chondrocytes were detected by ELISA, RT‒qPCR, Western blot, and biochemistry analyses. Protein‒protein interactions were verified by a coimmunoprecipitation (Co-IP) assay.ResultsBIG promoted chondrocyte proliferation and reduced apoptosis in vitro. BIG induced an alteration of the total RNA profiles in chondrocytes, and bioinformatic analysis showed that BIG inhibited chondrocyte apoptosis by promoting c-MYC expression; KEGG analysis confirmed that BIG-inhibited apoptosis was enriched in the cell cycle pathway. Flow cell cycle experiments confirmed that BIG promoted chondrocyte proliferation by significantly increasing the S phase cell number. The c-MYC inhibitor 10058-F4 stimulated the increased expression of IL-1β, IL-6, TNF-α, and AGEs and suppressed the cholesterol metabolism, which promoted chondrocyte apoptosis and autophagy. Co-IP analysis showed that BIG promoted the interaction of c-MYC and CH25H, Bcl-2, which suggests that BIG could inhibit chondrocyte apoptosis in part by enhancing c-MYC-mediated cholesterol metabolism.ConclusionsThis study confirmed that BIG promotes chondrocyte proliferation and inhibits apoptosis and autophagy, and BIG improving OA is associated with cholesterol metabolism. The results identify a potential mechanism by which BIG enhances c-MYC-mediated CH25H regulation of cholesterol metabolism in vitro and suggest that BIG might be a promising new drug against OA.

Network and Computational Drug Repurposing Analysis for c-Myc Inhibition in Burkitt Lymphoma.

The treatment rate of Burkitt lymphoma (BL) is still low in low-income countries and among elderly patients. The c-Myc dysregulation induced by mutations is one of the characteristics of BL. However, studies on the downstream signaling pathways of c-Myc are still lacking. This study aimed to identify the signaling pathways regulated by c-Myc. Network and gene set analyses using c-Myc inhibition (i.e., c-Myc knock-down and c-Myc inhibitor treatment) transcriptome datasets for BL cell lines were performed to determine the pathways regulated by c-Myc. In addition, computational drug repurposing was used to identify drugs that can regulate c-Myc downstream signaling pathway. Computational drug repurposing revealed that the ERK/MAPK signaling pathway is regulated by c-Myc in BL and that this pathway can be modulated by vorinostat. Furthermore, in the pharmacogenomics database, vorinostat showed a cell viability half-maximal inhibitory concentration of less than 2 μM in the BL cell lines. The downstream signaling pathway regulated by c-Myc and the drug that can modulate this pathway is presented for the first time.

Synergistic Effect of CK2 Inhibitor CX-4945 with HDACi Chidamide on Cell Proliferation Arrest and Apoptosis in Acute Myeloid Leukemia

Background CX-4945 is an ATP-competitive inhibitor of CK2, which is currently being used in clinical trials to treat various cancer types. Chidamide (CHI), a novel histone deacetylase inhibitor (HDACi), is now involved in the salvage treatment of relapsed/refractory acute myeloid leukemia (AML) in a clinical trial. The anti-leukemia effects of either single drug have been reported by inducing cell apoptosis through suppressing multi-oncogenic pathways in human tumor cells. However, whether and how the combination of the two drugs exerts synergistic anti-tumor effects remains undetermined. This study is to investigate the synergistic therapeutic effects of CX-4945 in combination with CHI in AML. Methods Cell Counting Kit-8 (CCK-8) cell proliferation assay, Annexin V apoptosis assay, and Propidium Iodide cell cycle assay were performed in AML cells in the presence of CX-4945 only, CHI only, CX-4945 + CHI, and vehicle control for 48h. RNA-seq was performed in U937 cells treated with CX-4945 and CHI, respectively; the differentially expressed genes (DEGs) were identified by R studio, and pathway enrichment of the DEGs was analyzed with Metascape online tool. Data were expressed as the mean ± standard deviation. Ordinary one-way ANOVA statistical analysis and Log-rank test was employed to determine the significant difference between groups. A synergistic effect was determined by the combination indices (CIs) with CalcuSyn software. Results The 50% inhibiting concentration (IC50) of CX-4945 on the U937 and THP-1 cell proliferation is 7.435±0.066μmol/L and 6.787±0.153μmol/L. The IC50 of CHI on the U937 and THP-1 cell proliferation is 3.009±0.32μmol/L and 3.782±0.239μmol/L, respectively. The combination of various doses of CHI with either IC50 or 1/2 IC50 of CX-4945 significantly decreases the cell viability of the cells versus single-drug control and CalcuSyn analysis showed the high synergistic therapeutic effects of CHI with CX-4945 (Fig.1A). The combination of (4µM) CHI with (8µM) CX-4945 significantly induced the G0/G1 cell cycle arrest (p <0.001, Fig.1B) and elevated the % of apoptotic cells (p <0.0001, Fig.1C) in the AML cells compared to either single drug alone. Moreover, the combination of (1.6µM) CHI with (8µM) CX-4945 significantly increased the % of apoptotic cells in the primary blasts from the AML patient versus either single drug alone (p<0.0001, Fig.1D). To further understand the underlying mechanism of the synergy, RNA-seq analysis was performed in U937 cells treated with either CHI or CX-4945, respectively (Fig.2A). The DEGs are achieved upon either drug treatment, and the 76 up-regulated and 411 down-regulated overlapped DEGs were identified (Fig.2B). Pathways analysis showed that the overlapped DEGs are enriched in cell cycle progress, apoptosis, and multiple oncogenic signaling including cMyc and PI3K/AKT signaling pathways (Fig.2C). cMyc and PI3K/AKT-dependent signaling pathways are involved in myeloid cell proliferation. Also, our ChIP-seq data indicated obvious Ikaros binding peaks in the promoter region of cMyc and PIK3CD and they are the direct targets of Ikaros (data not shown). cMyc and PIK3CD are at the top of the overlapped DEGs, indicating the critical roles of the cMyc and PIK3CD underlying the mechanism of the combination in AML. Indeed, the mRNA level of cMyc and PIK3CD is significantly down-regulated upon the combination treatment versus single drug control (Fig.2D or data not shown). Consistently, the mRNA level of PIK3CD is significantly higher expressed in AML patients versus that in bone marrow samples of the healthy donors (p<0.05, Fig.2E) and the AML patients with high PIK3CD high expression have shorter OS than that with low expression (p <0.05, Fig.2F). These data support the hypothesis that the combination exerts the anti-tumor effect by suppression of cMyc and PIK3CD expression in AML. Conclusions The combination of CHI and CX-4945 has a synergistic effect on cell proliferation arrest, apoptosis, and cell cycle arrest by suppressing cMyc and PI3K signaling in AML cells. Our data provide experimental evidence for the combination as a potential option for AML therapy. More pre-clinical studies will be explored for future clinical trials.

Homoharringtonine Enhances the Anti-Leukemia Effect of Venetoclax in Acute Myeloid Leukemia with t(8;21)(q22;q22) Via Regulation of c-Myc/Bim Axis

Purpose: Recently, small cases reports showed that acute myeloid leukemia (AML) with translocation (8;21)(q22;q22) [t(8;21) AML] responded poorly to venetoclax (VEN) plus azacitidine (AZA) (VA) regimen. Our previous study revealed homoharringtonine (HHT) enhanced the the killing effect of VA in AML. This study went further to explore the mechanism of VEN-resistance and the synergetic effect of VEN and HHT (VH) in overcoming resistance in t(8;21) AML. Methods: Patients with/without t(8;21) AML, being treated with VA with/without HHT were included for response assessment. Synergetic effect and mechanism of VEN combined with HHT or AZA was studied in cell lines, primary cells and mice. Results: Patients with t(8;21) AML acquired significantly lower CR/CRi rate than those without, with VA regimen as frontline (1/5 vs. 56/82, P=0.027) or salvage treatment (1/10 vs. 60/127, P=0.023), while the CR/CRi rate was comparable between the two cohorts with VA plus HHT (VAH) as salvage treatment (9/13 vs. 102/152, P>0.05). Synergetic effect in anti-leukemia was observed in VH but not VA in t(8;21) AML cell lines, primary cells and cell line-derived xenograft mice. Transcriptome RNA-sequencing and western blot detection found c-Myc and its downstring signialing were significantly decreased with the treatment of VH but not VA as compared to the controls. In addition, VEN induced accumulation of c-Myc in t(8;21) cells. Genetic silencing or pharmacological inhibition of c-Myc restored VEN sensitivity in t(8;21) cells. Co-immunoprecipitation assay found Bim, the crucial BH3-only protein, participated in the course of VH-inducing apoptosis. Direct or indirect inhibition of c-Myc increased expression of Bim, while overexpression of c-Myc significantly inhibited the transcription of Bim in t(8;21) cells. CUT&RUN assay revealed two functional sites of c-Myc binded to the promoter of Bim gene. Conclusion: Abnormal activation of c-Myc might contribute to the resistance of VEN via suppression of Bim in t(8;21) AML. HHT might enhance the killing effect of VEN by regulation of c-Myc/Bim axis. Key words: acute myeloid leukemia, t(8;21), homoharringtonine, venetoclax, c-Myc

Tetrazole derivatives as potent immunomodulatory agents in tumor microenvironment

Twenty-seven compounds bearing a tetrazole ring as a central unit have been designed, synthetized and biologically evaluated. Studies have been performed in order to compare the effect of tetrazole derivatives bearing amine electron-donor or nitro electron-acceptor groups. The antiproliferative activity has been determined in monoculture studies on tumor cell lines HT-29, A-549, MCF-7 and on non-tumor cell line HEK-293 as well as in co-culture studies (HT-29/THP-1). All the compounds have been studied as PD-L1 (Programmed Death Ligand 1), VEGFR-2 (Vascular Endothelial Growth Factor 2), CD-47 (Cluster of Differentiation 47) and c-Myc inhibitors. The effect on TNF-α secretion has also been determined. Bromoderivatives 23, 24 and chloroderivatives 26, 27 have demonstrated an apoptotic effect on HT-29 cancer cells. Compounds bearing an amine group have shown very promising effects as TME immunomodulatory agents.