Tumor Suppressor Activity Research Articles

AH-6809 mediated regulation of lung adenocarcinoma metastasis through NLRP7 and prognostic analysis of key metastasis-related genes.

Lung adenocarcinoma (LUAD) has become one of the leading causes of cancer-related deaths globally, with metastasis representing the most lethal stage of the disease. Despite significant advances in diagnostic and therapeutic strategies for LUAD, the mechanisms enabling cancer cells to breach the blood-brain barrier remain poorly understood. While genomic profiling has shed light on the nature of primary tumors, the genetic drivers and clinical relevance of LUAD metastasis are still largely unexplored. This study aims to investigate the genomic differences between brain-metastatic and non-brain-metastatic LUAD, identify potential prognostic biomarkers, and evaluate the efficacy of AH-6809 in modulating key molecular pathways involved in LUAD metastasis, with a focus on post-translational modifications (PTMs). Genomic analyses were performed using data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) between brain-metastatic and non-metastatic LUAD samples were identified. Key gene modules were determined using Weighted Gene Co-expression Network Analysis (WGCNA), and their prognostic significance was assessed through Kaplan-Meier analysis. Cellular experiments, including CCK8 and qRT-PCR assays, were conducted to evaluate the anti-cancer effects of AH-6809 in LUAD cells. Apoptosis and inflammatory marker expression were assessed using immunofluorescence. Genomic analysis differentiated brain-metastatic from non-brain-metastatic LUAD and identified NLRP7, FIBCD1, and ELF5 as prognostic markers. AH-6809 significantly suppressed LUAD cell proliferation, promoted apoptosis, and modulated epithelial-mesenchymal transition (EMT) markers. These effects were reversed upon NLRP7 knockdown, highlighting its role in metastasis. Literature analysis further supported AH-6809's tumor-suppressive activity, particularly in NLRP7 knockdown cells, where it inhibited cell growth and facilitated apoptosis. AH-6809 was also found to affect SUMO1-mediated PTMs and downregulate EMT markers, including VIM and CDH2. NLRP7 knockdown partially reversed these effects. Immunofluorescence revealed enhanced apoptosis and inflammation in lung cancer cells, especially in NLRP7 knockdown cells treated with AH-6809. The regulatory mechanisms involve SUMO1-mediated post-translational modifications and NQO1. Further studies are required to elucidate the molecular mechanisms and assess the clinical potential of these findings. These findings demonstrate the critical role of NLRP7 and associated genes in LUAD metastasis and suggest that AH-6809 holds promise as a potential therapeutic agent for brain-metastatic LUAD.

Anti-tumor activity of butorphanol in colorectal cancer via targeting SIGMAR1.

Colorectal cancer (CRC) stands for a prevailing gastrointestinal neoplasm, concomitant with considerable occurrence and lethality rate. Butorphanol, a synthetic opioid analgesic medication targeting the opiate receptor, has been recently reckoned to harbor anti-oncogenic properties. This study proposes to delineate the impacts of butorphanol on CRC and the interrelated response mechanism. In sigma non-opioid intracellular receptor 1 (SIGMAR1)-overexpressing CRC cells treated by varying concentrations of butorphanol, the functional experiments including CCK-8 method, EDU staining, wound healing and transwell assays severally appraised the capabilities for CRC cells to proliferate, migrate as well as invade. TUNEL staining assayed the cellular apoptotic level. The expressions of proteins implicated in proliferation, metastasis as well as apoptosis were ascertained by Western blot. CB-Dock2 server predicated butorphanol-SIGMAR1 interaction and Western blot also examined SIGMAR1 expression. Noticeably, butorphanol profoundly eliminated the capabilities of CRC cells to proliferate, migrate and invade whilst intensified the cellular apoptotic level with the ascending doses. Butorphanol was identified to possess an interrelation with SIGMAR1 and concentration-dependently lowered SIGMAR1 expression. Elevation of SIGMAR1 partially blunted the affection of butorphanol on the biological events of CRC cells. To sum up, butorphanol may extenuate the aggressive cellular behaviors to produce tumor-suppressing activity on CRC via binding with SIGMAR1.

Molecular interplay between the upregulated levels of Sad1 and UNC84 Domain Containing 2 (SUN2) and gene expression in medulloblastoma cells.

SUN2 is a nuclear envelope protein associated with the nuclear lamina and with proteins linked to nuclear export, splicing, and nucleo-cytoskeleton communication. Studies of SUN2 in cancer have been limited but have suggested that it has tumor-suppressive activity in some carcinomas. Medulloblastoma is a pediatric tumor that develops in the cerebellum and is currently classified intofour molecular groups: WNT (Wingless), SHH (Sonic Hedgehog), 3, and 4. SUN2 expression profiles appear to be altered in brain cancer but have not been previously evaluated in medulloblastoma. The University of Alabama at Birmingham Cancer (UALCAN) data analysis portal, Gene Expression Profiling Interactive Analysis (GEPIA), the Oncopression gene expression compendium, and the R2 genomics analysis and visualization platform were used to analyze SUN2 expression in cancer, which was found to vary by cancer type; in particular, SUN2 expression was found to be upregulated in medulloblastoma. We also explored the effects of reduced SUN2 protein levels (by RNA interference) on gene expression profiles using a cDNA microarray in DAOY medulloblastoma-derived cells. We found that SUN2 protein is upregulated in medulloblastoma, mainly in the SHH group, which correlates with poor survival. Furthermore, the reduced SUN2 expression in medulloblastoma cells is associated with the downregulation of the expression of other genes, including members of the bitter taste-sensing type 2 receptor (TAS2R) family. This study shows that SUN2 is upregulated in medulloblastoma-with molecular interplay in gene expression-which has group-dependent implications for medulloblastoma development. In particular, the upregulation of SUN2 is associated with a progression of the SHH group of medulloblastoma.

The Novel Direct AR Target Gene Annexin A2 Mediates Androgen-Induced Cellular Senescence in Prostate Cancer Cells.

Clinical trials for prostate cancer (PCa) patients have implemented the bipolar androgen therapy (BAT) that includes the treatment with supraphysiological androgen level (SAL). SAL treatment induces cellular senescence in tumor samples of PCa patients and in various PCa cell lines, including castration-resistant PCa (CRPC), and is associated with enhanced phospho-AKT levels. Using an AKT inhibitor (AKTi), the SAL-mediated cell senescence is inhibited. Here, we show by RNA-seq analyses of two human PCa cell lines, that annexin A2 (ANXA2) expression is induced by SAL and repressed by co-treatment with AKTi. Higher ANXA2 expression is associated with better survival of PCa patients and suggests that ANXA2 is part of SAL-mediated tumor suppressive activity. ChIP-seq revealed that AR is recruited to the intronic regions of ANXA2 gene suggesting that ANXA2 is a novel direct AR target gene. Knockdown of ANXA2 shows that SAL-induced cellular senescence is mediated by ANXA2 and enhances the levels of phospho-AKT indicating an interaction between the AR, ANXA2 and AKT. Notably, we found that the level of heat shock protein HSP27, known to interact with ANXA2, is associated with cellular senescence. HSP27 level is induced by SAL but the induction is blunted by knockdown of ANXA2 suggesting a novel ANXA2-HSP27 pathway in PCa. This was confirmed using an HSP27 inhibitor that reduced the SAL-induced cellular senescence levels suggesting that ANXA2 upregulates HSP27 to mediate AR-signaling in SAL-induced cellular senescence. Thus, the data indicate ANXA2-HSP27 cross-talk as novel factors in the signaling by the AR-AKT pathway to mediate cellular senescence.

Oncogenic HRAS Induces Metformin Resistance in Head and Neck Cancer by Promoting Glycolytic Metabolism.

Metformin administration has recently emerged as a candidate strategy for the prevention of head and neck squamous cell carcinoma (HNSCC). However, the intricate relationship between genetic alterations in HNSCC and metformin sensitivity is still poorly understood, which prevents the stratification of patients, harboring oral premalignant lesions that may benefit from the chemopreventive activity of metformin. In this study, we investigate the impact of prevalent mutations in HNSCC on response to metformin. Notably, we found that the expression of oncogenic HRAS mutants confers resistance to metformin in isogenic HNSCC cell systems, and that HNSCC cells harboring endogenous HRAS mutations display limited sensitivity to metformin. Remarkably, we found that metformin fails to reduce activation of the mTOR pathway in HRAS oncogene-expressing HNSCC cells in vitro and in vivo, correlating with reduced tumor suppressive activity. Mechanistically, we found that this process depends on the ability of HRAS to enhance glycolytic metabolism, thereby suppressing the requirement for oxidative phosphorylation to maintain the cellular energetic balance. Overall, our study revealed that HNSCC cells with oncogenic HRAS mutations exhibit diminished metformin sensitivity, thus shedding light on a potential mechanism of treatment resistance. This finding may also help explain the limited clinical responses to metformin in cancers with RAS mutations. Ultimately, our study underscores the importance of understanding the impact of the genetic landscape in tailoring precision cancer-preventive approaches in the context of HNSCC and other cancers that are characterized by the presence of a defined premalignant state, and therefore, are amenable to cancer interception strategies. Prevention Relevance: Our findings highlight the challenges of using metformin for cancer prevention in RAS-mutant cancers, where elevated glycolysis may reduce drug efficacy. This underscores the need to explore metformin's potential in early, premalignant stages, before metabolic shifts render it less effective.

Abstract PR010: DICER1 cancer predisposition tumor promotion mediated non-cell autonomously via neutrophils and NETosis

Abstract DICER1 cancer predisposition syndrome is a heritable condition where affected patients have increased risk of neoplasms including fusion-negative rhabdomyosarcoma (FN-RMS). The syndrome is defined by germline heterozygous loss of function mutations in DICER1, but it remains unclear exactly how these mutations predispose children to cancer. To gain insight into the role of Dicer1 loss in DICER1 cancer predisposition, we deleted the Dicer1 gene both in the germline or conditionally within the tumor cell in our previously established mouse model of FN-RMS. One would expect the germline loss of one allele to provide a sensitized background in the tumor cell to acquire a second hit mutation. However, we observed faster tumor onset and increased penetrance in mice with germline heterozygous Dicer1 loss (Dicer1 +/- ) but not in mice when Dicer1 loss was restricted to the tumor cells (Dicer1 Flox/+ ), demonstrating that haploinsufficient tumor suppressor activity of Dicer1 loss requires non-cell autonomous cell types. Single cell RNA sequencing (scRNA-Seq) revealed significant expansion of immature neutrophils in Dicer1 +/- tumors, which were enriched for proteases associated with neutrophil extracellular traps (NETs). NETs are webs of chromatin and proteases released when neutrophils in response to inflammatory stimuli in process termed NETosis. We show Dicer1 +/- murine and human tumors are enriched for neutrophils and tumor-bearing mice had abundant circulating NETs. NETs cause significant damage to the local extracellular matrix (ECM) and have been implicated in tumor promotion. In addition, neutrophil enrichment, we found that Dicer1 +/- tumors show significant ECM remodeling and are increased C5a, a potent neutrophil chemoattractant and NET-priming factor. These results suggest NETosis is upregulated in Dicer1 +/- FN-RMS tumors. Ligand-receptor pair analysis (iTALK) on the scRNA- Seq data revealed a putative interaction between a NET-derived ligand and EGFR and IGF1R on tumor cells, suggesting direct tumor promoting signaling from NET-to-tumor. We validated this novel FN-RMS promotion mechanism in vitro using human FN-RMS cell lines and observed that this NET-derived ligand promoted FN-RMS growth through both EGFR and IGF1R signaling. NET release requires citrullination of histone H3 mediated by peptidyl arginine deiminase 4 (PADI4) to facilitate decondensation of chromatin. We intercrossed the Padi4 -/- allele into our tumor model to genetically block NETosis and observed complete rescue of the accelerated tumor onset and increased penetrance observed in Dicer1 +/- mice. These results demonstrate that NETosis promotes the growth of Dicer1 +/- FN-RMS tumors and is required for Dicer1 +/- haploinsufficiency. These findings may be applicable to many DICER1 syndrome- associated cancers, as neutrophils which get converted to tumor promoters by heterozygous DICER1 loss are present in DICER1 syndrome patients regardless of tumor type and suggest targeting neutrophils/NET-release may reduce cancer risk in DICER1 +/- individuals. Citation Format: Randolph K Larsen, Jason A Hanna, Hongjian Jin, Kristen B Reed, Darden W Kimbrough, Kyna Voung, Myron K Evans, Casey G Langdon, Catherine J Drummond, Matthew R Garcia, David Finkelstein, Patrick A Schreiner, Jerold E Rehg, Kris Ann P Schultz, Mark E Hatley. DICER1 cancer predisposition tumor promotion mediated non-cell autonomously via neutrophils and NETosis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr PR010.

Abstract B006: Rescuing expression of a tumor suppressor gene – restoring FH in Hereditary leiomyomatosis and renal cell carcinoma

Abstract Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a disorder characterized by the loss of fumarate hydratase (FH) activity, leading to the development of cutaneous leiomyomas, uterine leiomyomas, and aggressive early-onset type 2 papillary renal cell carcinoma. In HLRCC, the disease is driven by the somatic loss of the remaining functional FH allele in individuals carrying a germline pathogenic variant in one copy of the FH gene. The complete loss of FH activity disrupts the tricarboxylic acid (TCA) cycle, resulting in the accumulation of fumarate, which disrupts signaling pathways and contributes to the oncogenic phenotype. We recently identified a single nucleotide polymorphism (SNP) in an intronic region of the fumarate hydratase (FH) gene that leads to the loss of FH activity (Crooks et al., 2023). This SNP introduces a novel splice-acceptor site, resulting in the inclusion of an aberrant exon between wild-type exons 9 and 10. This ‘poison-like’ exon encodes a premature STOP codon, producing a nonfunctional truncated FH protein. Previous studies have shown that restoring FH activity can abrogate pathogenic behavior in patient-derived cells, highlighting the potential for therapeutic interventions targeting FH activity restoration. Our goal is to restore FH enzymatic activity by preventing the inclusion of this cryptic exon in carriers of this variant. To achieve this, we are exploring strategies to restore functional FH production by interfering with the inclusion of the pathogenic intron during splicing by removing the splice acceptor using CRISPR-Cas9 or base editing technologies. We tested these approaches by generating a reporter cell line that recapitulates the splicing pattern observed in patients, where expression of GFP depends on correct splicing between exon 9 and 10. We successfully identified antisense oligonucleotide (ASO) and single-guide RNA (sgRNA) sequences that restore GFP expression in our reporter cell lines. We are now evaluating the efficacy of these reagents in patient-derived cells. An alternative approach involves using synthetic RNA to restore FH expression. The expression of proteins from synthetic RNAs is a promising strategy for treating cancer and infectious diseases. We are currently investigating the efficiency of restoring FH activity through in-vitro transcribed (IVT) mRNA. This approach has the advantage of enabling FH function restoration in cells with mutations that are not amenable to antisense oligonucleotide (ASO) or gene editing techniques. This work serves as an avenue to investigate the application of nucleic acid therapies to restoring activity tumor suppressor genes in kidney cancer. Citation Format: Siddhardha S. Maligireddy, Mariana D. Mandler, Jodie C. Lunger, Christina M. Fitzsimmons, Daniel R. Crooks, Geetha M. Cawthon, Christopher J. Ricketts, Cathy D. Vocke, W. Marson Linehan, Pedro J. Batista. Rescuing expression of a tumor suppressor gene – restoring FH in Hereditary leiomyomatosis and renal cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr B006.

The pro-oncogenic noncanonical activity of a RAS•GTP:RanGAP1 complex facilitates nuclear protein export.

Canonical RAS signaling, including PI3K/AKT- and RAF/MEK-dependent activities, results mainly from RAS•GTP interaction with its effectors at the plasma membrane. Here, we identified a fundamental, oncogenic, noncanonical RAS•GTP activity that increases XPO1-dependent export of nuclear protein cargo into the cytoplasm and is independent of PI3K/AKT and RAF/MEK signaling. This RAS-dependent step acts downstream from XPO1 binding to nuclear protein cargo and is mediated by a perinuclear protein complex between RAS•GTP and RanGAP1 that facilitates hydrolysis of Ran•GTP to Ran•GDP, which promotes release of nuclear protein cargo into the cytoplasm. The export of nuclear EZH2, which promotes cytoplasmic degradation of the DLC1 tumor suppressor protein, is a biologically important component of this pro-oncogenic activity. Conversely, preventing nuclear protein export contributes to the antitumor activity of KRAS inhibition, which can be further augmented by reactivating the tumor suppressor activity of DLC1 or potentially combining RAS inhibitors with other cancer treatments.

Experimental in vivo models for understanding inter-molecular interactions and preventing multifactor disease development

The increased spontaneous fragility in the centromere regions of the chromosomes predisposes to abnormal cellular division due to abnormal interaction with the mitotic spindle, which leads to number chromosomal aberrations. The abnormal structure of the microtubule-associated proteins (MAPs) could also be among the internal factors, predisposing to these pathologies. On the other hand, the increased frequency of the spontaneous chromosomal fragility suggests abnormal structure of the respective chromosomal/chromatin components and thus an increased risk about gene mutations and structural chromosomal aberrations. The spontaneous chromosomal fragility was tested by light microscopy observation of metaphases from peripheral blood lymphocytes of 8 patients with polygene pathologies (neoplasms, neuro-degenerative diseases, and neuro-psychiatric disorders) and of 18 healthy controls. In the tested patients was established significantly higher frequency of the spontaneous chromosomal fragility, including in the centromere chromosomal regions, compared to the controls. Different inter-molecular interactions, which could prevent the pathology appearance, were investigated by appropriate experimental in vivo models. As a whole, in the most cases, the presented data showed significantly lower average titers of anti-ganglioside antibodies and gangliosides in the samples from myocardium and liver than in the samples from brain and pancreas. By taking into consideration that the myocardium and liver are known as the most enriched of GSH anatomic organs, the presented data could be explained with the literature messages of higher amounts of de novo-synthesized free GSH tri-peptide in the same two organs. Moreover, a possibility about the production of antibodies/immunoglobulins by non-lymphoid types of cells, tissues, and organs in appropriate conditions was shown. Because the so-produced antibodies are out of the germinative centers in the specialized lymphoid tissues and organs, the control of their functions by small ions and molecules as gangliosides is very important. In the current study, the attention was particularly directed to the iteractions with the participation of gangliosides, the reduced form of the tri-peptide glutathione (GSH), and the protein HACE1. Besides the tumor-suppressor activity of protein HACE1, also its neuroprotective influence was proven, namely by interactions with specific molecules.

Role of the basic leucine zipper transcription factor BATF2 in modulating immune responses and inflammation in health and disease.

Basic leucine zipper transcription factor ATF-like 2 (BATF2) is a transcription factor that is known to exhibit tumor-suppressive activity in cancer cells. Within recent years, however, BATF2 has also emerged as an important transcriptional regulator of the immune system. Through its immunomodulatory function, BATF2 has been implicated in a variety of (patho)physiological processes, including host defense against infection, anti-tumor immunity, and maintenance of tissue inflammatory homeostasis. Below, we discuss recent literature that has provided insight into the role of BATF2 as a transcriptional regulator of immune responses in health and disease, including the cell types that express BATF2, the different diseases in which the immunomodulatory effects of BATF2 have been shown to play a role, and the molecular mechanisms through which BATF2 is thought to exert those effects. In doing so, we highlight that the immunological effects of BATF2 are highly context-dependent, and we point out overlap between the mechanisms of action of BATF2 in infectious disease and non-infectious disease. We also discuss areas of interest for future research, the clinical relevance of better understanding BATF2 function, and potential strategies for therapeutic modulation of BATF2.

The Inhibitory Effect and Mechanism of the Histidine-Rich Peptide rAj-HRP from Apostichopus japonicus on Human Colon Cancer HCT116 Cells.

Colon cancer is a common and lethal malignancy, ranking second in global cancer-related mortality, highlighting the urgent need for novel targeted therapies. The sea cucumber (Apostichopus japonicus) is a marine organism known for its medicinal properties. After conducting a bioinformatics analysis of the cDNA library of Apostichopus japonicus, we found and cloned a cDNA sequence encoding histidine-rich peptides, and the recombinant peptide was named rAj-HRP. Human histidine-rich peptides are known for their anti-cancer properties, raising questions as to whether rAj-HRP might exhibit similar effects. To investigate whether rAj-HRP can inhibit colon cancer, we used human colon cancer HCT116 cells as a model and studied the tumor suppressive activity in vitro and in vivo. The results showed that rAj-HRP inhibited HCT116 cell proliferation, migration, and adhesion to extracellular matrix (ECM) proteins in vitro. It also disrupted the cytoskeleton and induced apoptosis in these cells. In vivo, rAj-HRP significantly inhibited the growth of HCT116 tumors in BALB/c mice, reducing tumor volume and weight without affecting the body weight of the tumor-bearing mice. Western blot analysis showed that rAj-HRP inhibited HCT116 cell proliferation and induced apoptosis by upregulating BAX and promoting PARP zymogen degradation. Additionally, rAj-HRP inhibited HCT116 cell adhesion and migration by reducing MMP2 levels. Further research showed that rAj-HRP downregulated EGFR expression in HCT116 cells and inhibited key downstream molecules, including AKT, P-AKT, PLCγ, P38 MAPK, and c-Jun. In conclusion, rAj-HRP exhibits significant inhibitory effects on HCT116 cells in both in vitro and in vivo, primarily through the EGFR and apoptosis pathways. These findings suggest that rAj-HRP has the potential as a novel targeted therapy for colon cancer.

Tumor-suppressive activities for pogo transposable element derived with KRAB domain via ribosome biogenesis restriction

Transposable elements (TEs) are indispensable for human development, with critical functions in pluripotency and embryogenesis. TE sequences also contribute to human pathologies, especially cancer, with documented activities as cis/trans transcriptional regulators, as sources of non-coding RNAs, and as mutagens that disrupt tumor suppressors. Despite this knowledge, little is known regarding the involvement of TE-derived genes (TEGs) in tumor pathogenesis. Here, systematic analyses of TEG expression across human cancer reveal a prominent role for pogo TE derived with KRAB domain (POGK). We show that POGK acts as a tumor suppressor in triple-negative breast cancer (TNBC) cells and that it couples with the co-repressor TRIM28 to directly block the transcription of ribosomal genes RPS16 and RPS29, in turn causing widespread inhibition of ribosomal biogenesis. We report that POGK undergoes deactivation by isoform switching in clinical TNBC, altogether revealing its exapted activities in tumor growth control.

Advances in CRISPR-Cas9 Technology for Tumor Therapy

Genome editing technology is an emerging toolbox that can specifically target genes. At present, the existing gene editing technologies include ZFN, TALEN, and CRISPR system editing technology with clusters of regularly spaced short palindromic repeats. However, ZFN and TALEN are no longer the preferred tools for gene editing due to some of their problems, and their complex protein design, high cost, and high difficulty are the main reasons that limit their use. The CRISPR system, on the other hand, is able to achieve specific binding by base complementary pairing of sgRNA to the target sequence. Traditional cancer treatment methods have limited efficacy and high recurrence rates, and the disease can be fundamentally treated by inactivating oncogenes or activating tumor suppressor genes through gene editing technology and then changing downstream signaling pathways for cancer treatment. With CRISPR-Cas9 technology, it is possible to have gene knockouts, insertions, and mutations. Here, we will investigate and explore the feasibility of the CRISPR system for tumor treatment, including the following three topics: oncogene knockout, augmentation of tumor suppressor gene expression, and enhancement of engineered T cell viability for effective tumor Through these methods, the CRISPR system is of great help and promising tumor therapy.

The N-Terminal Region of the Transcription Factor E2F1 Contains a Novel Transactivation Domain and Recruits General Transcription Factor GTF2H2.

The transcription factor E2F1 is the principal target of the tumor suppressor pRB. E2F1 promotes cell proliferation by activating growth-promoting genes upon growth stimulation. In contrast, E2F1 contributes to tumor suppression by activating tumor suppressor genes, such as ARF, upon loss of pRB function, a major oncogenic change. The transactivation domain of E2F1 has previously been mapped to the C-terminal region. We show here that the N-terminal region of E2F1 is critical for the activation of tumor suppressor genes. Deletion of the N-terminal region dramatically compromised E2F1 activation of tumor suppressor genes. The N-terminal region showed transactivation ability when fused to the DNA-binding domain of GAL4. A search for novel interacting factors with the N-terminal region, using a yeast two-hybrid system, identified the general transcription factor GTF2H2. Overexpression of GTF2H2 enhanced E2F1 activation of tumor suppressor genes and induction of cell death. Conversely, the knockdown of GTF2H2 compromised both. E2F1 binding enhanced the binding of GTF2H2 to target promoters depending on the integrity of the N-terminal region. Taken together, these results suggest that the N-terminal region of E2F1 contains a novel transactivation domain that mediates the activation of tumor suppressor genes, at least in part, by recruiting GTF2H2.

Tryptophanol-derived oxazoloisoindolinone fluorescent probes for cellular localization studies of p53 activators

The protein p53 is a transcription factor with several key roles in cells, including acting as a tumour suppressor. In most human cancers its tumour suppressor function is inactivated, either through inhibition by negative regulators or by mutation in the TP53 gene. Thus, there is a high interest in developing molecules able to activate p53 tumour suppressor activity. Tryptophanol-derived isoindolinones are known to act as wild-type and mutant p53 activators. Specifically, SLMP53-1 is a non-fluorescent wild-type and mutant p53 R280K reactivator, with potent in vivo anti-tumour activity in HCT116 and MDA-MB-231 mice xenograft models. With the aim of studying tryptophanol-derived isoindolinones intracellular localization by fluorescence microscopy, three SLMP53-1 based fluorescent probes were prepared. Here we report the design, synthesis, photophysical characterization, antiproliferative activity and cell localization studies of these fluorescent probes.The previously described structure–activity relationships of the SLMP53-1 scaffold set the basis for the design the fluorescent probes. The probes were prepared by connecting a small fluorophore (dansyl or 7-nitrobenzofurazan) to the indole nitrogen of the tryptophanol-derived oxazoloisoindolinone SLMP53-1 through two different linkers. The antiproliferative activity and cell localization studies of the three fluorescent probes were performed in HCT116 cells. The three probes showed enhanced internalization when compared with their fluorophore-linker intermediates, good photo-stability and high affinity for the endoplasmic reticulum, indicating the potential involvement of endoplasmic reticulum in the mechanism of action of tryptophanol-derived oxazoloisoindolinones.

Heparin-binding EGF-like growth factor via miR-126 controls tumor formation/growth and the proteolytic niche in murine models of colorectal and colitis-associated cancers

MicroRNAs, including the tumor-suppressor miR-126 and the oncogene miR-221, regulate tumor formation and growth in colitis-associated cancer (CAC) and colorectal cancer (CRC). This study explores the impact of the epithelial cytokine heparin-binding epidermal growth factor (HB-EGF) and its receptor epidermal growth factor receptor (EGFR) on the pathogenesis of CAC and CRC, particularly in the regulation of microRNA-driven tumor growth and protease expression. In murine models of CRC and CAC, lack of miR-126 and elevated miR-221 expression in colonic tissues enhanced tumor formation and growth. MiR-126 downregulation in colon cells established a pro-tumorigenic proteolytic niche by targeting HB-EGF-active metalloproteinase-7, -9 (MMP7/MMP9), disintegrin, and metalloproteinase domain-containing protein 9, and modulating chemokine-mediated recruitment of HB-EGF-loaded inflammatory cells. Mechanistically, downregulation of HB-EGF and EGFR in the colon suppressed miR-221 and enhanced miR-126 expression via activating enhancer-binding protein 2 alpha. Reintroducing miR-126 reduced tumor development and HB-EGF expression. Combining miR-126 reintroduction, which targets specific HB-EGF-active proteases but not ADAM17, with MMP inhibitors like Batimastat or Marimastat effectively suppressed tumor growth. This combination normalized protease expression and balanced miR-126 and miR-221 levels in developing and growing tumors. These findings demonstrate that suppressing HB-EGF and EGFR1 shifts the balance from oncogenic miR-221 to tumor-suppressive miR-126 action. Consequently, normalizing miR-126 expression could open new avenues for treating patients with CAC and CRC, and this normalization is intertwined with the anticancer efficacy of MMP inhibitors.

Discovery and Characterization of Brigimadlin, a Novel and Highly Potent MDM2-p53 Antagonist Suitable for Intermittent Dose Schedules.

p53 is known as the guardian of the genome and is one of the most important tumor-suppressors. It is inactivated in most tumors, either via tumor protein p53 (TP53) gene mutation or copy number amplification of key negative regulators, e.g., mouse double minute 2 (MDM2). Compounds that bind to the MDM2 protein and disrupt its interaction with p53 restore p53 tumor suppressor activity, thereby promoting cell cycle arrest and apoptosis. Previous clinical experience with MDM2-p53 protein-protein interaction antagonists (MDM2-p53 antagonists) have demonstrated that thrombocytopenia and neutropenia represent on-target dose-limiting toxicities that might restrict their therapeutic utility. Dosing less frequently, while maintaining efficacious exposure, represents an approach to mitigate toxicity and improve the therapeutic window of MDM2-p53 antagonists. However, to achieve this, a molecule possessing excellent potency and ideal pharmacokinetic properties is required. Here, we present the discovery and characterization of brigimadlin (BI 907828), a novel, investigational spiro-oxindole MDM2-p53 antagonist. Brigimadlin exhibited high bioavailability and exposure, as well as dose-linear pharmacokinetics in preclinical models. Brigimadlin treatment restored p53 activity and led to apoptosis induction in preclinical models of TP53 wild-type, MDM2-amplified cancer. Oral administration of brigimadlin in an intermittent dosing schedule induced potent tumor growth inhibition in several TP53 wild-type, MDM2-amplified xenograft models. Exploratory clinical pharmacokinetic studies (NCT03449381) showed high systemic exposure and a long plasma elimination half-life in cancer patients who received oral brigimadlin. These findings support the continued clinical evaluation of brigimadlin in patients with MDM2-amplified cancers, such as dedifferentiated liposarcoma.

Differential effect of plakoglobin in restoring the tumor suppressor activities of p53-R273H vs. p53-R175H mutants.

The six most common missense mutations in the DNA binding domain of p53 are known as "hot spots" and include two of the most frequently occurring p53 mutations (p53-R175H and p53-R273H). p53 stability and function are regulated by various post-translational modifications such as phosphorylation, acetylation, sumoylation, methylation, and interactions with other proteins including plakoglobin. Previously, using various carcinoma cell lines we showed that plakoglobin interacted with wild-type and several endogenous p53 mutants (e.g., R280K, R273H, S241F, S215R, R175H) and restored their tumor suppressor activities in vitro. Since mutant p53 function is both mutant-specific and cell context-dependent, we sought herein, to determine if plakoglobin tumor suppressive effects on exogenously expressed p53-R273H and p53-R175H mutants are similarly maintained under the same genetic background using the p53-null and plakoglobin-deficient H1299 cell line. Functional assays were performed to assess colony formation, migration, and invasion while immunoblotting and qPCR were used to examine the subcellular distribution and expression of specific proteins and genes that are typically regulated by or regulate p53 function and are altered in mutant p53-expressing cell lines and tumors. We show that though, plakoglobin interacted with both p53-R273H and p53-R175H mutants, it had a differential effect on the transcription and subcellular distribution of their gene targets and their overall oncogenic properties in vitro. Notably, we found that plakoglobin's tumor suppressive effects were significantly stronger in p53-R175H expressing cells compared to p53-R273H cells. Together, our results indicate that exploring plakoglobin interactions with p53-R175H may be useful for the development of cancer therapeutics focused on the restoration of p53 function.

Deubiquitinase OTUD7B Regulates Cell Proliferation in Breast Cancer

PurposeThe deubiquitylase OTUD7B plays a facilitates role in lung tumorigenesis through VEGF protein, but its role in breast cancer remains unclear. In the present study, we proposed to explore the role of deubiquitylase OTUD7B in breast cancer. MethodsThe expression of OTUD7B in breast cancer and adjacent tissues was detected. The role of OTUD7B in cell proliferation and invasion of breast cancer cell lines such as MCF-7 and MDA-MB-453 was explored. ResultsOTUD7B is highly expressed in human breast cancer tissues and its higher expression correlates with better survival of patients. Further mechanistic studies reveal that OTUD7B associates with RASGRF1 and PLCE1 to disrupt RAS signaling pathway. Knockdown of OTUD7B results in decreasing levels of RASGRF1 protein, suppression cell growth and invasion in breast cancer. Collectively, our results reveal a previously unappreciated anti-oncogentic role OTUD7B involved in RAS signaling pathway in breast cancer and indicate that deubiquitylases could induce tumor-suppressing or tumor-promoting activities in a cell- and tissue-dependent context.

P53motifDB: integration of genomic information and tumor suppressor p53 binding motifs.

The tumor suppressor gene TP53 encodes the DNA binding transcription factor p53 and is one of the most commonly mutated genes in human cancer. Tumor suppressor activity requires binding of p53 to its DNA response elements and subsequent transcriptional activation of a diverse set of target genes. Despite decades of close study, the logic underlying p53 interactions with its numerous potential genomic binding sites and target genes is not yet fully understood. Here, we present a database of DNA and chromatin-based information focused on putative p53 binding sites in the human genome to allow users to generate and test new hypotheses related to p53 activity in the genome. Users can query genomic locations based on experimentally observed p53 binding, regulatory element activity, genetic variation, evolutionary conservation, chromatin modification state, and chromatin structure. We present multiple use cases demonstrating the utility of this database for generating novel biological hypotheses, such as chromatin-based determinants of p53 binding and potential cell type-specific p53 activity. All database information is also available as a precompiled sqlite database for use in local analysis or as a Shiny web application.