Cell Anchorage-independent Growth Research Articles

FBXO46 negatively regulates p53 activity by stabilizing Mdm2.

The tumor suppressor p53 plays a central role in suppressing tumor formation. Mouse double minute 2 homolog (Mdm2) serves as the principal ubiquitin E3 ligase responsible for the ubiquitination and subsequent degradation of p53. However, the regulatory mechanisms governing the Mdm2-p53 pathway are not comprehensively understood. Here, we report that F-box only protein 46 (FBXO46) directly binds to Mdm2 and inhibits its self-ubiquitination and degradation, leading to Mdm2 stabilization and subsequent Mdm2-mediated ubiquitination and degradation of p53. Functionally, FBXO46 promotes cell proliferation, accelerates G1/S cell cycle progression, and increases anchorage-independent cell growth by inhibiting p53. Collectively, these findings reveal a critical role for FBXO46 in controlling Mdm2 stability and establish FBXO46 as an important regulator of the Mdm2-p53 pathway.

PKR associates with 4.1R to promote anchorage-independent growth of hepatocellular carcinoma and lead to poor prognosis.

RNA-dependent protein kinase (PKR) may have a positive regulatory role in controlling tumor growth and progression in hepatocellular carcinoma (HCC). However, the downstream substrates and the molecular mechanism of PKR in the growth and progression of HCC have not been clarified. In this study, mass spectrometry analysis was performed with immunoprecipitated samples, and 4.1R was identified as a protein that binds to PKR. In transfected COS7 cells, an immunoprecipitation experiment showed that 4.1R binds to wild-type PKR, but not to a kinase-deficient mutant PKR, suggesting that PKR binds to 4.1R in a kinase activity-dependent manner. In HCC cell lines, HuH7 and HepG2, the expression level of 4.1R protein was shown to be regulated by protein expression and activation of PKR. Interestingly, high expression of 4.1R, as well as PKR, is associated with a worse prognosis in HCC. PKR increased HCC cell growth in both anchorage-dependent and anchorage-independent manners, whereas 4.1R was involved in HCC cell growth only in an anchorage-independent manner, not in an anchorage-dependent manner. The rescue experiment indicated that increased anchorage-independent growth of HCC cells by PKR might be caused by 4.1R. In conclusion, PKR associates with 4.1R and promotes anchorage-independent growth of HCC. The PKR-4.1R axis might be a new therapeutic target in HCC.

ISO-upregulated BECN1 specifically promotes LC3B-dependent autophagy and anticancer activity in invasive bladder cancer

Isorhapontigenin (ISO), an active compound isolated from the Chinese herb Gnetum Cleistostachyum, exhibited strong preventive and therapeutic effects on bladder cancer (BC) both in vitro and in vivo. Our previous studies revealed that ISO-induced autophagy is crucial for its anti-cancer activity. However, the underlying mechanism remains unclear. Here, we showed that BECN1, an important autophagic protein, was induced by ISO treatment and played crucial roles in ISO-induced late phase of LC3B-dependent, and LC3A-independent autophagy, as well as anti-cancer activity. Downregulation of BECN1 was observed in human BCs and BBN-induced mouse invasive BC tissues, whereas co-treatment with ISO completely reversed BECN1 downregulation in BBN-induced mouse invasive BCs. Consistently, ISO treatment significantly increased BECN1 expression in vitro in a dose- and time-dependent manner. Depletion of BECN1 significantly impaired LC3B-dependent autophagy following ISO treatment, as well as abolished the inhibitory effect of ISO on anchorage-independent growth of human BC cells. Mechanistic studies revealed that BECN1 induction was mediated by ISO downregulation of c-Myc, which resulted in miR-613 reduction, in turn leading to increased NCL translation and further promoting NCL binding to BECN1 mRNA, subsequently stabilizing BECN1 mRNA. In conclusion, our results demonstrate that by activating c-Myc/miR-613/NCL axis, ISO treatment results in BECN1 posttranscriptional upregulation, which specifically initiates LC3B-dependent autophagy and anti-cancer activity. Our findings further strengths our application of ISO for therapy of high-grade invasive BC (HGIBC) patients.

RSK2-mediated cGAS phosphorylation induces cGAS chromatin-incorporation-mediated cell transformation and cancer cell colony growth

Cyclic guanosine-adenosine monophosphate synthase (cGAS) is a key cytosolic DNA sensor that plays a pivotal role in the innate immune response. Although a decade of research on the cGAS has advanced our understanding of inflammasome formation, cytokine production, and signaling pathways, the role of cGAS in the nucleus remains unclear. In this study, we found that the nuclear localization of endogenous and stably expressed cGAS differed from transiently expressed cGAS, which mainly localized in the cytosol. In the nucleus, cGAS is tightly bound to chromatin DNA. The chromatin DNA binding of cGAS was dependent on RSK2. Our molecular mechanism study indicated that the N-lobe of RSK2 harboring 1–323 interacted with the NTase domain of cGAS harboring residues 213–330. This interaction increased RSK2-induced cGAS phosphorylation at Ser120 and Thr130, resulting in the tightly binding of cGAS to chromatin. Importantly, epidermal growth factor (EGF)-induced cell transformation and anchorage-independent colony growth showed an increase in growth factors, such as EGF or bFGF, in cGAS stable expression compared to mock expression. Notably, the cGAS-S120A/T130A mutant abolished the increasing effect of cell transformation of JB6 Cl41 cells and colony growth of SK-MEL-2 malignant melanoma cells. The results suggested that cGAS’s chromatin DNA binding, which is indispensable to RSK2-dependent phosphorylation of cGAS at Ser120/Thr130, provides the first clue to how cGAS may participate in chromatin remodeling in the nucleus.

12234 Gα13 Promotes Clonogenic Growth By Increasing Tolerance To Oxidative Metabolic Stress In Prostate Cancer Cells

Abstract Disclosure: D. Wu: None. W. Lim: None. X. Chai: None. V.P. Seshachalam: None. S.A. Rasheed: None. S. Ghosh: None. P.J. Casey: None. Gα13 and Gα12 are members of the G12 family of Gα proteins that, along with their associated Gβγ subunits, mediate signaling from specific G protein-coupled receptors. Analyses of tumor specimens indicate that Gα13 expression correlates with patient survival in several solid cancers. We previously reported a role for Gα13 in cell migration and invasion in prostate cancer cell lines. Interestingly, patient data supports the notion that mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason scores. Gα13 lower-expressing LNCaP cells also have lower SOD2 protein levels compared to the Gα13 higher-expressing PC3 cells. Hence, we explored the role of Gα13 in prostate tumorigenesis, and its effect on cellular processes such as cell survival and mitochondrial metabolism, in human prostate cancer cell lines PC3 and LNCaP. We stably knocked-down GNA13 expression in PC3 cells and overexpressed GNA13 in LNCaP cells. We found that Gα13 promoted anchorage-independent cell growth in PC3 and LNCaP cell lines, as assessed by soft agar colony formation, spheroid formation, and xenograft tumor growth. Whole-genome transcriptome analyses suggested that Gα13-regulated genes are functionally enriched in the mitochondria compartment and that GNA13 expression positively correlated to SOD2 transcript levels in PC3 cells. We found that silencing GNA13 sensitized PC3 cells to long-term oxidative metabolic stress when cultured in media containing non-glycolytic metabolites, namely galactose, glutamate plus malate, and succinate. Furthermore, Gα13 levels impacted the abundance of SOD2 protein in the mitochondria, as well as SOD2 promoter activity and mRNA expression. In addition, silencing GNA13 increased mitochondrial superoxide levels in PC3 cells when cultured in galactose medium, as assessed by MitoSOX staining and flow cytometry. Moreover, overexpression of SOD2 could rescue the effect of Gα13 loss on suppression of anchorage-independent cell growth in PC3 cells. Importantly, anchorage-independent cell growth was not rescued when a catalytically-inactive SOD2(Q167A) mutant was expressed. Likewise, stable knockdown of SOD2 suppressed the effect of overexpression of Gα13 on anchorage-independent cell growth in LNCaP cells. We propose a novel biological route of Gα13-mediated anchorage-independent growth and response to oxidative metabolic stress through regulation of SOD2 expression in prostate cancer cells. Given that SOD2 protein levels correlate with prostate cancer Gleason grade, identifying the upregulated GPCRs that signal through Gα13 in prostate cancer could lead to novel preventive or therapeutic strategies. Presentation: 6/1/2024

Roles of ZEB1 and ZEB2 in E-cadherin expression and cell aggressiveness in head and neck cancer.

Zinc finger E-box binding homeobox 1 (ZEB1) has been identified as a key factor in cancer cell differentiation and metastasis, and has been well studied in the field of cancer cell biology. ZEB2 has a highly similar conformation to ZEB1, but its role in head and neck squamous cell carcinoma (HNSCC) cells is not fully understood. Here, we separately overexpressed ZEB1 and ZEB2 in C57BL/6 mouse oral cancer (MOC) cells and investigated their cellular characteristics, including E-cadherin levels, motile properties, chemoresistance, and metastatic ability in immunocompetent mice. Both ZEB1 and ZEB2 overexpression reduced epithelial traits and converted cells to an aggressive phenotype. Surprisingly, ZEB1 overexpression increased the endogenous level of ZEB2 in MOC cells, and vice versa. The molecular mechanisms underlying these findings remain unclear. However, the in vitro anchorage-independent growth of MOC cells overexpressing ZEB2 was considerably greater than that of MOC cells overexpressing ZEB1. These findings suggest that ZEB2, like ZEB1, has the ability to induce the differentiation of cancer cells into those with highly aggressive traits.

MiR-21-5p knockdown inhibits epithelial to mesenchymal transition in A549 lung adenocarcinoma cells by upregulating RhoB.

MiR-21-5p is a highly expressed microRNA that plays an important role in various cancer-promoting processes, including anchorage-independent growth, invasion, migration metastasis, and drug resistance in lung cancer. Studies indicate that miR-21-5p may contribute to these processes by promoting epithelial-mesenchymal transition (EMT). Ras homolog gene family member B (RhoB), a gene downregulated by miR-21-5p, has also been linked to EMT in lung cancer. However, the role of the miR-21-5p/RhoB axis in EMT regulation in lung adenocarcinoma remains unclear. In this study, we aimed to investigate the regulatory role of the miR-21-5p/RhoB axis in EMT and related in vitro functional characteristics such as migration, invasion, cisplatin resistance, and the formation of tumor spheroids. A549 cells were transfected with the miR-21-5p inhibitor, RhoB siRNA, and their corresponding negative controls. Wound healing, transwell invasion, Methyl thiazole tetrazolium (MTT), and sphere formation assays were also performed to evaluate the migration, invasion, cisplatin resistance, and anchorage-independent growth of A549 cells. RT-qPCR was used to determine the mRNA expression levels of EMT markers. MiR-21-5p knockdown inhibited migration, invasion, cisplatin resistance, and sphere formation while upregulating E-cadherin and downregulating Slug. Furthermore, RhoB silencing restored EMT and related in vitro functional characteristics in A549 cells. Knockdown of miR-21-5p inhibits EMT and related in vitro functional characteristics by upregulating RhoB, suggesting that miR-21-5p may promote EMT through downregulation of RhoB.

Evaluation of antitumor potential of an anti-glypican-1 monoclonal antibody in preclinical lung cancer models reveals a distinct mechanism of action.

The main objective of this study was to investigate the antitumor effect of a mouse anti-human glypican-1 (GPC1) monoclonal antibody (mAb) on non-small cell lung carcinoma (NSCLC) and associated molecular mechanisms. The anti-proliferative and anti-migratory activities of anti-GPC1 mAb were examined in A549 and H460 NSCLC cells and LL97A lung fibroblasts. The inhibitory effect of anti-GPC1 mAb on tumor growth was evaluated in an orthotopic lung tumor model. The in vitro study showed that anti-GPC1 mAb profoundly inhibited the anchorage-independent growth of A549 and H460 NSCLC cells and exhibited relatively high cytotoxic activities towards LL97A lung fibroblasts, A549/LL97A and H460/LL97A coculture spheroids. Moreover, anti-GPC1 mAb significantly decreased the expression of phospho-Src (p-Src; Tyr416), p-Akt (Ser473) and β-catenin in the co-cultured LL97A lung fibroblasts, and the expression of phospho-mitogen-activated protein kinase kinase (p-MEK; Ser217/221) and phospho-90 kDa ribosomal s6 kinase (p-p90RSK; Ser380) in co-cultured A549 cells. When anti-GPC1 mAb was administered to tumor-bearing mice, the inhibitory effect of anti-GPC1 mAb on the orthotopic lung tumor growth was not statistically significant. Nonetheless, results of Western blot analysis showed significant decrease in the phosphorylation of fibroblast growth factor receptor 1 (FGFR1) at Tyr766, Src at Tyr416, extracellular signal-regulated kinase (ERK) at Thr202/Tyr204, 90 kDa ribosomal S6 kinase (RSK) at Ser380, glycogen synthase kinases 3α (GSK3α) at Ser21 and GSK3β at Ser9 in tumor tissues. These data implicate that anti-GPC1 mAb treatment impairs the interaction between tumor cells and tumor associated fibroblasts by attenuating the paracrine FGFR signal transduction. The relatively potent cytotoxicity of anti-GPC1 mAb in lung fibroblasts and its potential inhibitory effect on the paracrine FGFR signal transduction warrant further studies on the combined use of this mAb with targeted therapeutics to improve therapeutic outcomes in lung cancer.

Neurotrophin-3 Facilitates Stemness Properties and Associates with Poor Survival in Lung Cancer

Introduction: Cancer stem cells (CSCs) shape the tumor microenvironment via neuroendocrine signaling and orchestrate drug resistance and metastasis. Cytokine antibody array demonstrated the upregulation of neurotrophin-3 (NT-3) in lung CSCs. This study aims to dissect the role of NT-3 in lung CSCs during tumor innervation. Methods: Western blotting, quantitative reverse transcription-PCR, and flow cytometry were used to determine the expression of the NT-3 axis in lung CSCs. NT-3-knockdown and NT-3-overexpressed cells were derived lung CSCs, followed by examining the stemness gene expression, tumorsphere formation, transwell migration and invasion, drug resistance, soft agar colony formation, and in vivo tumorigenicity. Human lung cancer tissue microarray and bioinformatic databases were used to investigate the clinical relevance of NT-3 in lung cancer. Results: NT-3 and its receptor tropomyosin receptor kinase C (TrkC) were augmented in lung tumorspheres. NT-3 silencing (shNT-3) suppressed the migration and anchorage-independent growth of lung cancer cells. Further, shNT-3 abolished the sphere-forming capability, chemo-drug resistance, invasion, and in vivo tumorigenicity of lung tumorspheres with a decreased expression of CSC markers. Conversely, NT-3 overexpression promoted migration and anchorage-independent growth and fueled tumorsphere formation by upregulating the expression of CSC markers. Lung cancer tissue microarray analysis revealed that NT-3 increased in patients with advanced-stage, lymphatic metastasis and positively correlated with Sox2 expression. Bioinformatic databases confirmed a co-expression of NT-3/TrkC-axis and demonstrated that NT-3, NT-3/TrkC, NT-3/Sox2, and NT-3/CD133 worsen the survival of lung cancer patients. Conclusion: NT-3 conferred the stemness features in lung cancer during tumor innervation, which suggests that NT-3-targeting is feasible in eradicating lung CSCs.

Isorhapontigenin inhibition of basal muscle-invasive bladder cancer attributed to its downregulation of SNHG1 and DNMT3b

BackgroundBladder cancer (BC) is among the most prevalent malignant urothelial tumors globally, yet the prognosis for patients with muscle-invasive bladder cancer (MIBC) remains dismal, with a very poor 5-year survival rate. Consequently, identifying more effective and less toxic chemotherapeutic alternatives is critical for enhancing clinical outcomes for BC patients. Isorhapontigenin (ISO), a novel stilbene isolated from a Gnetum found in certain provinces of China, has shown potential as an anticancer agent due to its diverse anticancer activities. Despite its promising profile, the specific anticancer effects of ISO on BC and the underlying mechanisms are still largely unexplored.MethodsThe anchorage-independent growth, migration and invasion of BC cells were assessed by soft agar and transwell invasion assays, respectively. The RNA levels of SOX2, miR-129 and SNHG1 were quantified by qRT-PCR, while the protein expression levels were validated through Western blotting. Furthermore, methylation-specific PCR was employed to assess the methylation status of the miR-129 promoter. Functional assays utilized siRNA knockdown, plasmid-mediated overexpression, and chemical inhibition approaches.ResultsOur study demonstrated that ISO treatment significantly reduced SNHG1 expression in a dose- and time-dependent manner in BC cells, leading to the inhibition of anchorage-independent growth and invasion in human basal MIBC cells. This effect was accompanied by the downregulation of MMP-2 and MMP-9 and the upregulation of the tumor suppressor PTEN. Further mechanistic investigations revealed that SOX2, a key upstream regulator of SNHG1, played a crucial role in mediating the ISO-induced transcriptional suppression of SNHG1. Additionally, we found that ISO treatment led to a decrease in DNMT3b protein levels, which in turn mediated the hypomethylation of the miR-129 promoter and the subsequent suppression of SOX2 mRNA 3’-UTR activity, highlighting a novel pathway through which ISO exerts its anticancer effects.ConclusionsCollectively, our study highlights the critical role of SNHG1 downregulation as well as its upstream DNMT3b/miR-129/SOX2 axis in mediating ISO anticancer activity. These findings not only elucidate the mechanism of action of ISO but also suggest novel targets for BC therapy.

MiR-617 interacts with the promoter of DDX27 and positively regulates its expression: implications for cancer therapeutics

BackgroundPervasive transcription of the eukaryotic genome generates noncoding RNAs (ncRNAs), which regulate messenger RNA (mRNA) stability and translation. MicroRNAs (miRNAs/miRs) represent a group of well-studied ncRNAs that maintain cellular homeostasis. Thus, any aberration in miRNA expression can cause diseases, including carcinogenesis. According to microRNA microarray analyses, intronic miR-617 is significantly downregulated in oral squamous cell carcinoma (OSCC) tissues compared to normal oral tissues.MethodsThe miR-617-mediated regulation of DDX27 is established by performing experiments on OSCC cell lines, patient samples, and xenograft nude mice model. Overexpression plasmid constructs, bisulphite sequencing PCR, bioinformatics analyses, RT-qPCR, Western blotting, dual-luciferase reporter assay, and cell-based assays are utilized to delineate the role of miR-617 in OSCC.ResultsThe present study shows that miR-617 has an anti-proliferative role in OSCC cells and is partly downregulated in OSCC cells due to the hypermethylation of its independent promoter. Further, we demonstrate that miR-617 upregulates DDX27 gene by interacting with its promoter in a dose-dependent and sequence-specific manner, and this interaction is found to be biologically relevant in OSCC patient samples. Subsequently, we show that miR-617 regulates cell proliferation, apoptosis, and anchorage-independent growth of OSCC cells by modulating DDX27 levels. Besides, our study shows that miR-617 exerts its effects through the PI3K/AKT/MTOR pathway via regulating DDX27 levels. Furthermore, the OSCC xenograft study in nude mice shows the anti-tumorigenic potential of miR-617.ConclusionmiR-617-mediated upregulation of DDX27 is a novel mechanism in OSCC and underscores the therapeutic potential of synthetic miR-617 mimics in cancer therapeutics. To the best of our knowledge, miR-617 is the 15th example of a miRNA that upregulates the expression of a protein-coding gene by interacting with its promoter.

TRIM65 promotes renal cell carcinoma through ubiquitination and degradation of BTG3

As a typical E3 ligase, TRIM65 (tripartite motif containing 65) is involved in the regulation of antiviral innate immunity and the pathogenesis of certain tumors. However, the role of TRIM65 in renal cell carcinoma (RCC) and the underlying mechanism has not been determined yet. In this study, we identified TRIM65 as a novel oncogene in RCC, which enhanced the tumor cell proliferation and anchorage-independent growth abilities both in vitro and in vivo. Moreover, we found that TRIM65-regulated RCC proliferation mainly via direct interaction with BTG3 (BTG anti-proliferation factor 3), which in turn induced the K48-linked ubiquitination and subsequent degradation through K41 amino acid. Furthermore, TRIM65 relieved G2/M phase cell cycle arrest via degradation of BTG3 and regulated downstream factors. Further studies revealed that TRIM65 acts through TRIM65-BTG3-CyclinD1 axis and clinical sample IHC chip data indicated a negative correction between TRIM65 and BTG3. Taken together, our findings demonstrated that TRIM65 promotes RCC cell proliferation via regulation of the cell cycle through degradation of BTG3, suggesting that TRIM65 may be a promising target for RCC therapy.

Role of Protein Tyrosine Phosphatase Receptor Type E (PTPRE) in Chemoresistant Retinoblastoma.

Protein tyrosine phosphatase receptor type E (PTPRE) is a member of the "classical" protein tyrosine phosphatase subfamily and regulates a variety of cellular processes in a tissue-specific manner by antagonizing the function of protein tyrosine kinases. PTPRE plays a tumorigenic role in different human cancer cells, but its role in retinoblastoma (RB), the most common malignant eye cancer in children, remains to be elucidated. Etoposide-resistant RB cell lines and RB patients display significant higher PTPRE expression levels compared to chemosensitive counterparts and the healthy human retina, respectively. PTPRE promotor methylation analyses revealed that PTPRE expression in RB is not regulated via this mechanism. Lentiviral PTPRE knockdown (KD) induced a significant decrease in growth kinetics, cell viability, and anchorage-independent growth of etoposide-resistant Y79 and WERI RB cells. Caspase-dependent apoptosis rates were significantly increased and a re-sensitization for etoposide could be observed after PTPRE depletion. In vivo chicken chorioallantoic membrane (CAM) assays revealed decreased tumor formation capacity as well as reduced tumor size and weight following PTPRE KD. Expression levels of miR631 were significantly downregulated in etoposide-resistant RB cells and patients. Transient miR631 overexpression resulted in significantly decreased PTPRE levels and concomitantly decreased proliferation and increased apoptosis levels in etoposide-resistant RB cells. These impacts mirror PTPRE KD effects, indicating a regulation of PTPRE via this miR. Additionally, PTPRE KD led to altered phosphorylation of protein kinase SGK3 and-dependent on the cell line-AKT and ERK1/2, suggesting potential PTPRE downstream signaling pathways. In summary, these results indicate an oncogenic role of PTPRE in chemoresistant retinoblastoma.

Abstract 4366: Loss of EP300 triggers IL-1α signaling and subsequent activation of the IL-6/JAK/STAT3 axis to drive oncogenesis in bladder cancer

Abstract Bladder Cancer (BLCA) is the sixth most common cancer in the United States with 81,180 new cases and 17,100 deaths in 2022. Next Generation Sequencing of BLCA has revealed an enrichment of alterations in genes classified as chromatin modifiers compared to other solid tumors. Among these is EP300, the gene encoding the p300 histone acetyltransferase, which is mutated in ~12% of BLCA with the majority putative loss of function frameshift and nonsense mutations. To investigate the biological role of EP300 loss-of-function in BLCA pathogenesis, we generated isogenic EP300 null RT112 bladder cancer cells using a 2-step CRISPR knockout (KO) and knockin strategy. EP300 KO cells demonstrated increased proliferation, anchorage independent cell growth, tumor formation in mice, and enhanced invasive potential. To investigate the mechanism(s) whereby EP300 loss-of-function enhances oncogenicity, we performed an unbiased Tandem Tag Mass Spectrometry (TMT MS) screen to identify pathways dysregulated in EP300 KO versus parental cells. EP300 loss-of-function was found to induce IL-6/JAK/STAT3 signaling via upregulated expression of IL-1α, a canonical pro-inflammatory cytokine. Knock down of IL1A gene expression was sufficient to downregulate STAT3 activation in EP300 KO cells, whereas ectopic stimulation using IL-1α increased STAT3 activation in parental RT112 cells, suggesting that IL-1α was the predominant upstream activator of JAK/STAT3 signaling in our model. Pharmacological inhibition of downstream targets of IL-1α signaling such as IRAK1/4 were also able to inhibit STAT3 signaling in EP300 KO cells in a dose and time dependent manner. Further investigations indicated that activated IL-1α signaling not only drove transcriptional upregulation of IL-6 but also the production of soluble IL-6R, activating IL-6 trans signaling. Finally, to elucidate how IL-1α upregulation is triggered by EP300 loss-of-function, we performed immunoprecipitation and immunofluorescence assays, which revealed that IL-1α binds directly to p300. Additionally, ectopic p300 expression in EP300 KO clones dramatically reduced IL-1α protein expression, indicating that p300 acts as a negative regulator of IL-1α in a bladder cancer context. In summary, EP300 loss-of-function relieves p300’s transcriptional and/or physical-tethering inhibition on IL-1α signaling, subsequently activating the IL-6/JAK/STAT3 pathway to drive oncogenesis in BLCA. Citation Format: James A. Rodrigues, Jiaqian Luo, Amanda R. Sabel, Ziyu Chen, Xinran Tang, Fengshen Kuo, Hikmat Al-Ahmadie, Kwanghee Kim, Eugene Pietzak, Gopa Iyer, David B. Solit, Sizhi P. Gao. Loss of EP300 triggers IL-1α signaling and subsequent activation of the IL-6/JAK/STAT3 axis to drive oncogenesis in bladder 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 4366.

Abstract 472: Long non-coding RNA MIR31HG-derived circRNA enhances the oncogenicity of oral carcinoma

Abstract Introduction: Oral carcinoma (OC) represents a significant health challenge, with the role of non-coding RNAs, particularly microRNAs and long non-coding RNAs (LncRNAs), being well-established in its progression. However, the implications of circular RNAs (circRNAs) in this context are less well understood, presenting a notable gap in current research. Our study focuses on the MIR31HG LncRNA, identified as crucial in OC, particularly its role in producing circRNA, as evidenced by sequencing. This specific MIR31HG-derived circRNA, designated 31HGcircR, which contains a potential open reading frame (ORF), and may demonstrate phenotypic significances. Alterations to 31HGcircR, either through knockout or ORF mutation, result in remarkable phenotypic changes, highlighting its potential importance in the pathogenesis of OC. Methods: We implemented 31HGcircR overexpression in OC cell lines, utilizing the TetOff system for gene expression control. CRISPR/Cas9 was employed for gene knockout, and siRNA for gene knockdown. Gene expression was quantified using qPCR. Additionally, the BaseScope assay was used to label and detect the spatial expression of overexpressed 31HGcircR within the cells. Assays to assess cell proliferation, invasion, migration, anchorage-independent growth (AIG), and clonogenicity were conducted. Results: The findings revealed specific junctions of 31HGcircR and varied expression levels across different OC cell lines. There was a significant correlation among the expression of 31HGcircR, MIR31HG and miR-31-5p. Notably, the knockdown of 31HGcircR led to pronounced inhibition of cell growth, migration, invasion, AIG, and clonogenic activity. Conversely, overexpression of 31HGcircR or its ORFs augmented invasion and clonogenic potential in certain cell lines. The TetOff system demonstrated that minimal concentrations of Doxycycline effectively suppressed 31HGcircR expression, with reversible effects upon removal. Knocking out 31HGcircR resulted in reduced invasion and clonogenic capabilities. Conclusion: This study provides clues demonstrating the oncogenic roles of 31HGcircR in OC, which simulate the functions of MIR31HG or miR-31-5p. The changes in cell phenotypes following 31HGcircR manipulation suggest its potential as a therapeutic target or biomarker in OC. These findings offer valuable insights, contributing to the evolving understanding of circRNAs in cancer research and potential treatment avenues. Citation Format: Chung-Hsien Chou, Hsi-Feng Tu, Kuo-Wei Chang, Shu-Chun Lin. Long non-coding RNA MIR31HG-derived circRNA enhances the oncogenicity of oral carcinoma [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 472.

Abstract 7072: MYC acetylated lysine residues drive oncogenic cell transformation and regulate select genetic programs for cell adhesion-independent growth and survival

Abstract The MYC oncogenic transcription factor is acetylated by the p300 and GCN5 histone acetyltransferases. The significance of MYC acetylation and functions of specific acetylated lysine (K) residues have remained unclear. Here, we show that the major p300-acetylated K148(149) and K157(158) sites in human (or mouse) MYC and the main GCN5-acetylated K323 residue are reversibly acetylated in various malignant and non-malignant cells. Oncogenic overexpression of MYC enhances its acetylation and alters regulation of site-specific acetylation by proteasome and deacetylase inhibitors. Acetylation of MYC at different K residues differentially affects its stability in a cell type- dependent manner. Lysine-to-arginine substitutions indicate that although none of the acetylated K (AcK) residues is required for MYC stimulation of adherent cell proliferation, individual AcK sites have gene-specific functions controlling select MYC-regulated processes in cell adhesion, contact inhibition, apoptosis, and/or metabolism, and are required for the malignant cell transformation activity of MYC. Each AcK site is required for anchorage-independent growth of MYC-overexpressing cells in vitro, and both the AcK148(149) and AcK157(158) residues are also important for the tumorigenic activity of MYC-transformed cells in vivo. These AcK residues may also preferentially activate transcription via facilitating MYC binding to several cancer-associated target gene promoters and via enhancing RNAP II recruitment. With the knowledge that MYC lysine residues can be acetylated by HATs GCN5 and P300, some HATs and HAT associated cofactors (i.e. YEATS2 and PIN1) are important for MYC recruitment to DNA binding. By identifying MYC acetylation-dependent coregulators and their oncogenic function, we proposed to understand whether and how MYC acetylation residues cooperate with its cofactors and influence malignant transformation in breast cancer cells.Overall, this study will uncover the functions and mechanisms of MYC acetylation in regulation of malignant transformation and the impact on breast cancer initiation and progression. By analyzing deregulated target genes and MYC-relevant coactivators, the MYC AcK site-specific signaling pathways identified may offer new avenues for selective therapeutic targeting of MYC oncogenic activities. Citation Format: Jeffrey J. Pino, Matthew Hurd, Yifan Zhao, Kay Jang, Michael Allevato, Marina Vorontchikhina, Wataru Ichikawa, Ryan Gates, Emily Villalpando, Michael Hamilton, Francesco Failo, Songqin Pan, Yue Qi, Yu-wen Hung, Thomas Girke, David Ann, Victoria Seewaldt, Ernest Martinez. MYC acetylated lysine residues drive oncogenic cell transformation and regulate select genetic programs for cell adhesion-independent growth and survival [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 7072.

Abstract 761: The relationship between ANGPTL4 and epidermal malignant transformation

Abstract High body mass index (BMI) is a risk factor for several types of cancers. Although epidemiology suggests obesity is negatively associated with non-melanoma skin cancer (NMSC), bariatric surgery has been shown to reduce the risk, suggesting a possible role of adipose tissue in the initiation and promotion of skin cancer. To gain mechanistic insight into how adipose tissue drives cutaneous carcinogenesis, we cultured non-tumorigenic mouse keratinocytes (JB6 P+ cells) with or without factors released from murine visceral adipose tissue (mFTF) and performed RNA-Sequencing. Published work demonstrated mFTF induces anchorage-independent cell growth, a surrogate marker for malignant transformation. Transcriptomic analysis demonstrated a significant induction of Angptl4 mRNA in JB6 P+ cells cultured with mFTF for 3 and 8 hours compared to the vehicle-treated cells. ANGPTL4 is an endogenous inhibitor of lipoprotein lipase that modulates free fatty acid delivery to adipose tissue and oxidative tissues such as muscle and liver. The C-terminal protein demonstrates tumor-associated activities such as angiogenesis, metastasis, protection against anoikis, and enhancement of cell survival. Therefore, we hypothesized that the induction of this gene promotes malignant transformation. RNA-seq data was validated in multiple cell models, including primary keratinocytes with human adipose tissue. Immunohistochemistry was used to assess ANGPTL4 expression in 37 actinic keratosis (pre-malignant) and cutaneous squamous cell carcinoma (cSCC) from patients with different BMIs (18.6 - 49.5). Notably, ANGPTL4 was only observed in the suprabasal epidermal layers in normal skin. For samples containing both lesional and perilesional skin, there was an increase in ANGPTL4 expression in the lesional epidermis relative to the normal perilesional skin. Furthermore, ANGPTL4 expression increased from transition to actinic keratosis to cSCC in situ, suggesting that ANGTL4 is induced during malignant transformation as observed in our pre-clinical models. Interestingly, once cSCC developed an invasive component, ANGTPL4 expression was lost in the invasive keratinocytes but persisted in the in situ component. There was no association between ANGPTL4 expression and BMI in lesional tissue. These data suggest that targeting ANTPLT4 may be a novel therapy for the prevention of skin cancer and that ANGPTL4-high patients or cancer patients with obesity may be a critical demographic for potential risk assessment or therapeutic intervention. Future studies will determine the impact of knocking out ANGTPL4 in our models of malignant transformation. Citation Format: Nat Ato Yawson, Jonathan D. Diedrich, Karen T. Liby, Jesse Veenstra, Jamie Jenna Bernard. The relationship between ANGPTL4 and epidermal malignant transformation [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 761.

Downregulation of LAMB3 Altered the Carcinogenic Properties of Human Papillomavirus 16-Positive Cervical Cancer Cells.

Nearly all cervical cancer cases are caused by infection with high-risk human papillomavirus (HR-HPV) types. The mechanism of cervical cell transformation is related to the powerful action of viral oncoproteins and cellular gene alterations. Transcriptomic data from cervical cancer and normal cervical cells were utilized to identify upregulated genes and their associated pathways. The laminin subunit beta-3 (LAMB3) mRNAwas overexpressed in cervical cancer and was chosen for functional analysis. The LAMB3 was predominantly expressed in the extracellular region and the plasma membrane, which play a role in protein binding and cell adhesion molecule binding, leading to cell migration and tissue development. LAMB3 was found to be implicated in the pathway in cancer and the PI3K-AKT signaling pathway. LAMB3 knockdown decreased cell migration, invasion, anchorage-dependent and anchorage-independent cell growth and increased the number of apoptotic cells. These effects were linked to a decrease in protein levels involved in the PI3K-AKT signaling pathway and an increase in p53 protein. This study demonstrated that LAMB3 could promote cervical cancer cell migration, invasion and survival.

Histone demethylase KDM4B accelerates the progression of glioblastoma via the epigenetic regulation of MYC stability

BackgroundGlioblastoma (GBM) is the most malignant and invasive human brain tumor. Histone demethylase 4B (KDM4B) is abnormally expressed in GBM, but the molecular mechanisms by which KDM4B affects the malignant tumor progression are not well defined.MethodsGBM cell lines and xenograft tumor samples were subjected to quantitative PCR (qPCR), Western blot, immunohistochemical staining (IHC), as well as ubiquitination, immunoprecipitation (IP), and chromatin immunoprecipitation (ChIP) assays to investigate the role of KDM4B in the progression of GBM.ResultsHere, we report that KDM4B is an epigenetic activator of GBM progression. Abnormal expression of KDM4B is correlated with a poor prognosis in GBM patients. In GBM cell lines, KDM4B silencing significantly inhibited cell survival, proliferation, migration, and invasion, indicating that KDM4B is essential for the anchorage-independent growth and tumorigenic activity of GBM cells. Mechanistically, KDM4B silencing led to downregulation of the oncoprotein MYC and suppressed the expression of cell cycle proteins and epithelial-to-mesenchymal transition (EMT)-related proteins. Furthermore, we found that KDM4B regulates MYC stability through the E3 ligase complex SCFFBXL3+CRY2 and epigenetically activates the transcription of CCNB1 by removing the repressive chromatin mark histone H3 lysine 9 trimethylation (H3K9me3). Finally, we provide evidence that KDM4B epigenetically activates the transcription of miR-181d-5p, which enhances MYC stability.ConclusionsOur study has uncovered a KDM4B-dependent epigenetic mechanism in the control of tumor progression, providing a rationale for utilizing KDM4B as a promising therapeutic target for the treatment of MYC-amplified GBM.

Inhibition of Survivin Homodimerization Decreases Neuroblastoma Cell Growth.

Increased expression of BIRC5/survivin, a crucial regulator of the mitotic spindle checkpoint, is associated with poor prognosis in neuroblastoma (NB), the most common extracranial tumor of childhood. Transcriptional inhibitors of survivin have been tested in adult cancers and inhibitors of survivin homodimerization are emerging. We compared genetic inhibition of survivin transcription with the inhibition of survivin homodimerization by S12 and LQZ-7I, chosen from a larger panel of survivin dimerization inhibitors with activity against NB cells. Mice hemizygous for Birc5 were crossed with NB-prone TH-MYCN mice to generate Birc5+/-/MYCNtg/+ mice. The marked decrease of survivin transcription in these mice did not suffice to attenuate the aggressiveness of NB, even when tumors were transplanted into wild-type mice to assure that immune cell function was not compromised by the lack of survivin. In contrast, viability, clonogenicity and anchorage-independent growth of NB cells were markedly decreased by S12. S12 administered systemically to mice with subcutaneous NB xenotransplants decreased intratumoral hemorrhage, albeit not tumor growth. LQZ-7I, which directly targets the survivin dimerization interface, was efficacious in controlling NB cell growth in vitro at markedly lower concentrations compared to S12. LQZ-7I abrogated viability, clonogenicity and anchorage-independent growth, associated with massively distorted mitotic spindle formation. In vivo, LQZ-7I effectively reduced tumor size and cell proliferation of NB cells in CAM assays without apparent toxicity to the developing chick embryo. Collectively, these findings show that inhibiting survivin homodimerization with LQZ-7I holds promise for the treatment of NB and merits further investigation.