Driver Of Tumorigenesis Research Articles

Abstract 1607: Saffron restricts MACC1-dependent cell proliferation and motility of colorectal cancer cells, and alters the microbiome structure

Abstract Saffron has proven a beneficial effect as a supplement in the treatment of many conditions through its perceived anti-oxidative and anti-inflammatory properties. We previously identified the gene MACC1 and demonstrated its importance as metastasis inducer, prognostic and predictive biomarker for colorectal cancer (CRC). It is confirmed as decisive driver for tumorigenesis and metastasis for a broad range of solid cancers. Therefore, we explored the inhibitory impact of saffron extracts on MACC1-induced cancer cell growth and motility and its effects on the gut microbiome. First, we assessed cell proliferation of MACC1-high and MACC1-low expressing cells using MTT and the IncuCyte real-time cell imaging system. We employed the endogenously MACC1-low expressing colon cancer cell line SW480 and clones with ectopic MACC1 overexpression. In addition, SW620 cells with endogenous high MACC1 expression and CRISPR-Cas9 mediated MACC1 knock-out were used. Cells were treated with increasing amounts of extracts from 4 different saffron species and concentration-dependent proliferation was analyzed by MTT assay. Changes in cell cycle were assessed by FACS. In vitro migration was measured by Boyden chamber assays. Activation of caspases was analyzed by Western blot. In addition, rats treated with saffron had their gut microbiome analyzed through 16S rDNA sequencing of fecal DNA samples. Upon addition of saffron, cells with high MACC1 expression showed a growth delay compared to cells with reduced MACC1 expression. Further, MACC1-dependent migration was reduced when cells were treated with saffron extracts. We did not find activation of caspases, but we showed a cell cycle arrest of MACC1 positive cells treated with saffron extracts. Using real-time measurement of cell proliferation we identified crocin as most active compound, in our system. Furthermore, rats fed with saffron showed major changes at the phylum level of their gut microbiome. A dramatic reduction/depletion of Cyanobacteria and Proteobacteria and a decrease of Bacteroidetes/Firmicutes ratio was found within the saffron treated rats. These reductions were accompanied by enrichment in Spirochaetes, Tenericutes and Candidatus saccharribacteria phyla in these rats. This is the first identification of saffron-based compounds restricting cancer cells proliferation and motility progression via the novel target MACC1. In addition, change of microbiome composition by saffron favors short chain fatty acid synthesis. The use of saffron or some of its extracts might be of therapeutic value to CRC patients. Citation Format: Nazli Güllü, Hassan Brim, Marjorie Gondre-Lewis, Silvia Bisti, Hamid Shoraka, Dennis Kobelt, Akbar Soleimani, Lena Timm, Janice Smith, Hassan Ashktorab, Ulrike Stein. Saffron restricts MACC1-dependent cell proliferation and motility of colorectal cancer cells, and alters the microbiome structure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1607.

Abstract P1-06-08: A p53-independent DNA damage response that regulates breast cancer phenotypes

Abstract Defects in the DNA damage repair system result in increased genomic instability and have recently been implicated as being drivers of tumorigenesis in both familial and sporadic breast cancers. To maintain genomic integrity, cells have a DNA damage response (DDR) mechanism that functions to repair damaged DNA efficiently and commits cells to death if damage is irreparable. Failure of this mechanism results in genomic instability and cancer predisposition. Widespread chromosomal instability is a characteristic feature of Triple-Negative Breast Cancer (TNBC), making it difficult to decipher between genes that drive cancer development from those that play a bystander role. Little is known about what gives rise to the extensive genomic instability of TNBC, and presents a major deficit in our scientific and clinical knowledge. Oncogene induced hyper-proliferation results in replication-associated double strand breaks (DSBs) that engage an Mre11-Rad50-Nbs1 complex-dependent DDR. Classically, the oncogene induced DDR is believed to suppress tumorigenesis due to downstream activation of p53. Using genetically engineered primary mammary epithelial cell models, we demonstrate p53-independent effects of the Mre11-dependent DDR in suppressing proliferation and DNA damage induced by diverse oncogenic drivers. Single cell whole genome sequencing in Her2/Neu expressing primary mammary epithelial cells reveals a landscape of stochastic copy number aberrations induced by oncogenic stress that becomes enriched for a genomic scar pattern of larger-size deletions in cells with Mre11 hypomorphism. We identify Mre11 pathway hypomorphism in a subset of basal-like breast cancers (BLBC), which confers vulnerability to specific DNA damaging agents and DDR inhibitors in murine models of p53-deficient BLBC. Thus, assessing the functional status of the Mre11-dependent DDR pathway in p53-mutant breast cancers may provide an opportunity for therapeutic exploitation. Citation Format: Fagan-Solis KD, Simpson DA, Kapustina M, Martelotto L, Reis-Filho JS, Petrini JH, Gupta GP. A p53-independent DNA damage response that regulates breast cancer phenotypes [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-06-08.

Abstract P6-12-02: isomiR-140-3p-regulated mevalonic acid pathway as a potiental target for prevention of triple negative breast cancer

Abstract Background: Prevention of triple negative breast cancer (TNBC) is hampered by lack of knowledge about the drivers of tumorigenesis. Methods: In order to identify molecular markers and their downstream networks that can potentially be targeted for TNBC prevention, we analyzed small RNA and RNA sequencing of a cell line model that represents early stages of TNBC development. We identified direct gene targets of an isomiRNA and using cell based and in vivo model systems we demonstrate the utility of targeting downstream pathways for prevention of TNBC. Results: These analyses showed that 5'isomiRNA of miR-140-3p (miR-140-3p-1) were deregulated in the normal-to- preneoplastic transition. We also identified novel direct gene targets of miR140-3p-1, HMG-CoA reductase (HMGCR) and HMG-CoA synthase 1(HMGCS1), key enzymes in the cholesterol biosynthesis pathway, and found that these too are deregulated in the normal to preneoplastic transition, resulting in activation of the cholesterol synthesis pathway. Upregulation in the cholesterol pathway creates a metabolic vulnerability that can be targeted with the statin class of inhibitors. Consistent with this hypothesis, we found direct targeting of miR-140-3p-1 and its downstream pathway by fluvastatin inhibits growth of these preneoplastic MCF10.AT1 cells. However, although, fluvastatin inhibited the growth of MCF10.AT1-derived xenografts, histological progression remained unchanged. The cholesterol pathway is highly regulated, and HMGCR enzymatic activity inhibition is known to trigger a feedback response leading to restoration of the pathway. Indeed, we found fluvastatin treatment induced HMGCR transcript levels in the explanted xenografts, with higher transcript induction directly correlated with the degree of histological progression of lesions, indicating an adaptive resistance mechanism that circumvents statin targeting of HMGCR. Therefore, we hypothesized that dual targeting of HMGCR and the feedback loops are necessary to overcome this adaptive resistance. To test this hypothesis, we generated MCF10AT1 cells resistant to fluvastatin. We then treated these resistance AT1 cells with an activator of AMP-activated protein kinase (AMPK), a brake in the cholesterol feedback pathway. AMPK activation by aspirin effectively abrogated the statin-induced upregulation of HMGCR and sensitized these resistant cells to fluvastatin. Conclusions: Our preclinical data suggests that the statin treatment induced homeostatic upregulation of the cholesterol pathway is a barrier to effective chemoprevention with statins. However, our results also suggest that this adaptive resistance mechanism can be abrogated by combined treatment with statin and AMPK activators such as aspirin. Clinical studies of this combined regimen should be considered in high risk patients. Citation Format: Bhardwaj A, Singh H, Trinidad CM, Albarracin C, Hunt KK, Bedrosian I. isomiR-140-3p-regulated mevalonic acid pathway as a potiental target for prevention of triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-12-02.

Abstract P6-21-06: Target N-Ras for degradation by flunarizine to treat basal-like breast cancer

Abstract Background:Basal-like breast cancer (BLBC) is an aggressive form of breast cancer that are usually triple negative for ER, PR, and HER2. There is no effective targeted therapy for BLBC due to the lack of a druggable driver. Ras GTPases are powerful drivers for tumorigenesis. We have shown that wild type N-Ras, but not K- or H-Ras, is overexpressed in BLBC and driving itsgrowth and transforming activities. However, there is currently no treatment that directly target Ras. This study thus screened existing pharmacologically active and approved compounds for the new ability to induce N-Ras degradation in BLBC. Methods:Compounds in the LOPAC library were screened by an automated microscopy system for the ability to reduce GFP-N-Ras signals in the cells. Isolated compounds were then examined to identify those that can degrade endogenous N-Ras in BLBC cells without impacting levels of other Ras proteins. Final candidate compounds were further examined to determine by which proteolytic pathway N-Ras is induced to be degraded. The potentials of the identified compound to treat BLBC were assessed by examining cell growth and soft agar colony formation in vitroand tumor growth in vivo. Results:We identified flunarizine (FLN), previously approved for treating migraine and epilepsy. The FLN-induced N-Ras degradation was not affected by a 26S-proteasome inhibitor. Rather, it was blocked by autophagy inhibitors. Furthermore, N-Ras can be seen co-localized with active autophagosomes upon FLN treatment, suggesting that FLN alters the autophagy pathway to degrade N-Ras. Importantly, FLN treatment recapitulated the effect of N-RASsilencingin vitroby selectively inhibiting the growth of BLBC cells, but not that of breast cancer cells of other subtypes. In addition, in vivoFLN inhibited tumor growth of a BLBC xenograft model. Conclusion:This proof-of-principle study presents evidence that the autophagy pathway can be coerced by small molecule inhibitors, such as FLN, to degrade Ras as a strategy to treat cancer. FLN has low toxicity and should be further investigated to enrich the toolbox of cancer therapeutics against BLBC. Citation Format: Zheng Z-Y, Li J, Li F, Zhu Y, Cui K, Wong ST, Chang EC, Liao Y-h. Target N-Ras for degradation by flunarizine to treat basal-like breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-21-06.

Reprogramming Captures the Genetic and Tumorigenic Properties of Neurofibromatosis Type 1 Plexiform Neurofibromas.

SummaryNeurofibromatosis type 1 (NF1) is a tumor predisposition genetic disease caused by mutations in the NF1 tumor suppressor gene. Plexiform neurofibromas (PNFs) are benign Schwann cell (SC) tumors of the peripheral nerve sheath that develop through NF1 inactivation and can progress toward a malignant soft tissue sarcoma. There is a lack of non-perishable model systems to investigate PNF development. We reprogrammed PNF-derived NF1(−/−) cells, descendants from the tumor originating cell. These NF1(−/−)-induced pluripotent stem cells (iPSCs) captured the genomic status of PNFs and were able to differentiate toward neural crest stem cells and further to SCs. iPSC-derived NF1(−/−) SCs exhibited a continuous high proliferation rate, poor myelination ability, and a tendency to form 3D spheres that expressed the same markers as their PNF-derived primary SC counterparts. They represent a valuable model to study and treat PNFs. PNF-derived iPSC lines were banked for making them available.

Clinical Practice Guidance: Surveillance for phaeochromocytoma and paraganglioma in paediatric succinate dehydrogenase gene mutation carriers.

SummaryThe succinate dehydrogenase (SDH) enzyme complex functions as a key enzyme coupling the oxidation of succinate to fumarate in the citric acid cycle. Inactivation of this enzyme complex results in the cellular accumulation of the oncometabolite succinate, which is postulated to be a key driver in tumorigenesis. Succinate accumulation inhibits 2‐oxoglutarate‐dependent dioxygenases, including DNA and histone demethylase enzymes and hypoxic gene response regulators. Biallelic inactivation (typically resulting from one inherited and one somatic event) at one of the four genes encoding the SDH complex (SDHA/B/C/D) is the most common cause for SDH deficient (dSDH) tumours. Germline mutations in the SDHx genes predispose to a spectrum of tumours including phaeochromocytoma and paraganglioma (PPGL), wild type gastrointestinal stromal tumours (wtGIST) and, less commonly, renal cell carcinoma and pituitary tumours. Furthermore, mutations in the SDHx genes, particularly SDHB, predispose to a higher risk of malignant PPGL, which is associated with a 5‐year mortality of 50%. There is general agreement that biochemical and imaging surveillance should be offered to asymptomatic carriers of SDHx gene mutations in the expectation that this will reduce the morbidity and mortality associated with dSDH tumours. However, there is no consensus on when and how surveillance should be performed in children and young adults. Here, we address the question: “What age should clinical, biochemical and radiological surveillance for PPGL be initiated in paediatric SDHx mutation carriers?”.

Orange is the new black: Kinases are the new master regulators of tumor suppression.

For many decades, kinases have predominantly been characterized as oncogenes and drivers of tumorigenesis, because activating mutations in kinases occur in cancer with high frequency. The oncogenic functions of kinases relate to their roles as growth factor receptors and as critical mediators of mitogen‐activated pathways. Indeed, some of the most promising cancer therapeutic agents are kinase inhibitors. However, cancer genomics studies, especially screens that utilize high‐throughput identification of loss‐of‐function somatic mutations, are beginning to shed light on a widespread role for kinases as tumor suppressors. The initial characterization of tumor‐suppressing kinases— in particular members of the protein kinase C (PKC) family, MKK4 of the mitogen‐activated protein kinase kinase family, and DAPK3 of the death‐associated protein kinase family— laid the foundation for bioinformatic approaches that enable the identification of other tumor‐suppressing kinases. In this review, we discuss the important role that kinases play as tumor suppressors, using several examples to illustrate the history of their discovery and highlight the modern approaches that presently aid in the identification of tumor‐suppressing kinases. © 2018 IUBMB Life, 71(6):738–748, 2019

Aberrant RNA Splicing in Cancer.

RNA splicing, the enzymatic process of removing segments of premature RNA to produce mature RNA, is a key mediator of proteome diversity and regulator of gene expression. Increased systematic sequencing of the genome and transcriptome of cancers has identified a variety of means by which RNA splicing is altered in cancer relative to normal cells. These findings, in combination with the discovery of recurrent change-of-function mutations in splicing factors in a variety of cancers, suggest that alterations in splicing are drivers of tumorigenesis. Greater characterization of altered splicing in cancer parallels increasing efforts to pharmacologically perturb splicing and early-phase clinical development of small molecules that disrupt splicing in patients with cancer. Here we review recent studies of global changes in splicing in cancer, splicing regulation of mitogenic pathways critical in cancer transformation, and efforts to therapeutically target splicing in cancer.

A primary undifferentiated pleomorphic sarcoma of the lumbosacral region harboring a LMNA-NTRK1 gene fusion with durable clinical response to crizotinib: a case report

BackgroundHigh-grade spindle cell sarcomas are a subtype of rare, undifferentiated pleomorphic sarcomas (UPSs) for which diagnosis is difficult and no specific treatment strategies have been established. The limited published data on UPSs suggest an aggressive clinical course, high rates of local recurrence and distant metastasis, and poor prognosis.Case presentationHere we present the unusual case of a 45-year-old male patient with a lumbosacral UPS extending into the sacrum. An initial diagnosis of a low-grade malignant spindle cell tumor was based on a tumor core biopsy. After complete extensive resection, the diagnosis of an UPS of the lumbosacral region was confirmed by excluding other types of cancers. Despite treatment with neoadjuvant radiotherapy, extensive resection, and adjuvant chemotherapy, the patient presented with multiple pulmonary metastases 3 months after surgery. The patient then began treatment with crizotinib at an oral dose of 450 mg per day, based on the detection of a LMNA-NTRK1 fusion gene in the tumor by next-generation sequencing. Over 18 months of follow-up through July 2018, the patient maintained a near-complete clinical response to crizotinib.ConclusionsThe LMNA-NTRK1 fusion was likely the molecular driver of tumorigenesis and metastasis in this patient, and the observed effectiveness of crizotinib treatment provides clinical validation of this molecular target. Molecular and cytogenetic evaluations are critical to accurate prognosis and treatment planning in cases of UPS, especially when treatment options are limited or otherwise exhausted. Molecularly targeted therapy of these rare but aggressive lesions represents a novel treatment option that may lead to fewer toxic side effects and better clinical outcomes.

Prolactin signaling drives tumorigenesis in human high grade serous ovarian cancer cells and in a spontaneous fallopian tube derived model

The pathways responsible for tumorigenesis of high grade serous ovarian cancer (HGSOC) from the fallopian tube epithelium (FTE) are still poorly understood. A human prolactin (PRL) like gene, Prl2c2 was amplified >100 fold in a spontaneous model of FTE-derived ovarian cancer (MOEhigh - murine oviductal epithelium high passage). Prl2c2 stable knockdown in MOEhigh cells demonstrated a significant reduction in cell proliferation, 2-dimensional foci, anchorage independent growth, and blocked tumor formation. The overall survival of ovarian cancer patients from transcriptome analysis of 1868 samples was lower when abundant PRL and prolactin receptors (PRL-R) were expressed. A HGSOC cell line (OVCAR3) and a tumorigenic human FTE cell line (FT33-Tag-Myc) were treated with recombinant PRL and a significant increase in cellular proliferation was detected. A CRISPR/Cas9 mediated PRL-R deletion in OVCAR3 and FT33-Tag-Myc cells demonstrated significant reduction in cell proliferation and eliminated tumor growth using the OVCAR3 model. PRL was found to phosphorylate STAT5, m-TOR and ERK in ovarian cancer cells. This study identified Prl2c2 as a driver of tumorigenesis in a spontaneous model and confirmed that prolactin signaling supports tumorigenesis in high grade serous ovarian cancer.

ALK Rearrangements Are Infrequent in Cellular Blue Nevus and Deep Penetrating Nevus.

Recent studies have identified kinase fusions in Spitzoid melanocytic neoplasms, and approximately 10% of Spitzoid neoplasms harbor anaplastic lymphoma kinase (ALK) rearrangements and corresponding ALK immunoreactivity. Deep penetrating nevi (DPN), a subset of melanocytic neoplasms, have histologic and immunohistochemical overlap that have historically supported classification of DPN with blue/cellular blue nevi (CBN). However, HRAS mutations have rarely been detected in DPN, thereby also linking them to Spitz nevi. The purpose of this study was to see if DPN or CBN possess ALK rearrangements, thereby providing more evidence that these melanocytic lesions may be pathogenetically related to Spitzoid neoplasms. Using ALK immunohistochemistry as a surrogate for ALK rearrangement, the authors examined 26 DPN, 30 CBN, and 4 conventional blue nevi. ALK immunoreactive cases underwent fluorescent in situ hybridization to investigate for the presence of ALK gene rearrangement. Patchy and focal ALK immunostaining was found in only 1 case of DPN (1/26, 3.8%). Seven cases of CBN (7/30; 23%) showed ALK immunostaining (6 focal/patchy, 1 strong and diffuse). Fluorescent in situ hybridization using ALK break-apart probes showed various degrees of gain of 2p23 and rare ALK break-apart signals. Four CBN showed ALK rearrangement in 2%-4% of cells. Two cases of CBN showed gain of 2p23 in 10%-20% of cells. In our study, ALK rearrangements are uncommon in both CBN and DPN, making ALK an unlikely driver in tumorigenesis and classification of these melanocytic variants. However, our study did identify ALK molecular changes and immunohistochemical staining patterns that have not been previously described in CBN or DPN.

Abstract 1815: Massively parallel identification of conserved drug resistant mutations in kinases

Abstract Drug resistant mutations that arise in therapeutic targets often limit clinical responses. However, the discovery of such mutations has historically been performed one gene or mutation at a time, often over decades of experimental and clinical testing, limiting our understanding of conserved mechanisms of drug resistance. We hypothesized that deep mutational scanning of canonical kinases may expedite this process and identify novel conserved elements that cause drug resistance when mutated (similar to the well-studied “Gatekeeper” residue). To test this, we generated cDNA-expression libraries containing all possible amino acid substitutions in CDK6, CDK4, ERK2, and EGFR. We screened each library against clinically utilized, ATP-competitive small molecule inhibitors. We then mapped the phenotypic data for over 40,000 missense mutations onto the aligned crystal structures of each protein and searched for shared structural attributes associated with drug resistance. This analysis revealed 4 equivalent amino acid sites whose mutation conferred drug resistance to ATP-competitive inhibitors in all of our screens: the Gatekeeper residue, as well as three uncharacterized residues. One of these sites, which we have termed the “Keymaster”, was additionally found to cause resistance in published data sets of sub-saturation BRAF, HER2, BCR-ABL, and MEK1 mutagenesis screens against their respective inhibitors. We confirmed that drug resistant phenotypes are caused by these alterations utilizing growth assays and protein target phosphorylation detection assays. Mechanistically, we show preliminary evidence that Keymaster-mutant proteins are competent for drug binding, but may display elevated basal activity. Consistent with our findings, we additionally identified mutations at Keymaster residues in reported patient tumors in a number of oncogene kinases, suggesting that Keymaster mutations could be drivers of tumorigenesis, as well as drug resistance. These efforts may prove useful for characterizing somatic kinase mutations of unknown function, designing next-generation therapeutics and deepening our understanding of kinase regulation. Citation Format: Nicole S. Persky, Desiree Hernandez, Jonathon Cordova, Amanda Walker, Lisa Brenan, Federica Piccioni, Sasha Pantel, Yenarae Lee, Amy Goodale, Xiaoping Yang, Yoichiro Mitsuishi, Mariana Do Carmo, Cong Zhu, Aleksandr Andreev, David E. Root, Cory M. Johannessen. Massively parallel identification of conserved drug resistant mutations in kinases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1815.

Abstract 5249: Crosstalk between visceral adipose and tumor tissue in colorectal cancer patients: Molecular signals driving host-tumor interaction

Abstract Adipose tissue has recently emerged as a driver of tumorigenesis, as adipose-associated factors enhance tumor growth and development. Here we investigated for the first time direct crosstalk between visceral adipose tissue (VAT) and tumor tissues in colorectal cancer (CRC) patients. We analyzed paired transcriptomic profiles of tissues and systemic inflammatory biomarkers among CRC patients to elucidate potential mechanisms and molecular signals driving the host-tumor interaction. Paired presurgery blood and tumor adjacent VAT, colorectal tumor and mucosa tissue samples collected during surgery were obtained from 47 Caucasian patients diagnosed with microsatellite-stable primary CRC enrolled in the ColoCare Study. Clinical/demographic information, and lifestyle-related risk factors, were reported. VAT was quantified by computed tomography. RNA was extracted from VAT, colorectal tumor and mucosa tissues, analyzed using HumanHT-12 Expression BeadChips, processed, and validated. Serum-based assays were conducted in 46 of 47 patients for systemic inflammatory markers with the Mesoscale Discovery Platform. High PTGS2 tumor expression was associated with 131 significantly altered VAT genes, of which 85.5% were upregulated. A significant upstream regulator of dysregulated VAT genes was SAA1. Investigation of circulating inflammatory biomarkers corroborated these transcriptomic findings, as patients with high PTGS2 tumor expression were also significantly more likely to have higher serum-based SAA levels. The differential expression of PPAR-γ in VAT identified 284 significantly altered tumor genes. 71.8% of tumor genes were upregulated in association with higher PPAR-γ VAT expression. Differentially expressed tumor genes were enriched in functional cellular movement. Inflammatory biomarkers in patient sera showed marginally significant differences for soluble ICAM-1 in association with differential PPAR-γ VAT expression. Overlap of the 131 altered VAT genes associated with differential PTGS2 tumor expression with the 284 dysregulated tumor genes associated with differential PPAR-γ VAT expression identified 15 common genes. Gene set enrichment analysis demonstrated that phenotypes associated with these genes in humans included cancer invasiveness signatures from tumor microenvironment interactions. Our multi-omics profiling of paired tissue transcriptomics and systemic inflammatory biomarkers from CRC patients established a bidirectional link between VAT and colorectal tumor tissue. We have demonstrated that this direct crosstalk activates signaling cascades to promote proinflammatory interactions and metabolic reprogramming. Future efforts to develop mechanism-based interventions that disrupt these molecular signals at the nexus of VAT-tumor crosstalk may improve obesity-driven CRC prevention and control. Citation Format: Andreana N. Holowatyj, Mariam Haffa, Tengda Lin, Biljana Gigic, Jennifer Ose, Christy Warby, Caroline Himbert, Clare Abbenhardt, Juergen Boehm, Magnus von Knebel Doeberitz, Nina Habermann, Esther Herpel, Hans-Ulrich Kauczor, Matthias Kloor, Johanna Nattenmüller, Peter Schirmacher, Martin Schneider, Petra Schrotz-King, Thomas Simon, Alexis Ulrich, Laura Bowers, Stephen D. Hursting, Cornelia M. Ulrich. Crosstalk between visceral adipose and tumor tissue in colorectal cancer patients: Molecular signals driving host-tumor interaction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5249.

Abstract 5312: The effect of Dnmt1 overexpression on intestinal tumorigenesis

Abstract Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in the United States. Strong genetic drivers of tumorigenesis, such as loss of function of the APC tumor-suppressor gene, have been well characterized, but the role of epigenetic alterations remains poorly understood. Upregulation of DNA methyltransferases (DNMTs), including DNMT1, has been reported in various human cancers, but its functional significance to cancer is unclear. Here we report a novel mouse model of inducible Dnmt1 upregulation, bypassing the embryonic lethality of Dnmt1 overexpression. We accomplish inducible control of Dnmt1 expression by targeting the tet transcriptional activator to the endogenous Dnmt1 promoter. We combine this model with the ApcMin allele to investigate the effect of Dnmt1 upregulation on intestinal tumorigenesis. Our preliminary data suggests that Dnmt1 overexpression increases the size and multiplicity of intestinal polyps in ApcMin/+ mice. Previous work in our lab showed that DNA methylation is critical for tumor formation, but it is not known which DNA methylation alterations have functional relevance. To investigate this, we will use the Dnmt1 overexpression model to identify DNA methylation events that are responsible for the observed phenotype in ApcMin/+ mice. In summary, we describe a novel mouse model of Dnmt1 overexpression and provide preliminary evidence to suggest that such upregulation exacerbates intestinal tumorigenesis. Our investigation may yield new insights into the role of epigenetics in CRC initiation and progression and into potential epigenetic therapies. Citation Format: Nicole A. Vander Schaaf, JinA Park, Oluwasei Dina, KwangHo Lee, Peter W. Laird. The effect of Dnmt1 overexpression on intestinal tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5312.

Small-Molecule Inhibitors Disrupt let-7 Oligouridylation and Release the Selective Blockade of let-7 Processing by LIN28

SUMMARYLIN28 is an RNA-binding protein that regulates the maturation of the let-7 family of microRNAs by bipartite interactions with let-7 precursors through its two distinct cold shock and zinc-knuckle domains. Through inhibition of let-7 biogenesis, LIN28 functions as a pluripotency factor, as well as a driver of tumorigenesis. Here, we report a fluorescence polarization assay to identify small-molecule inhibitors for both domains of LIN28 involved in let-7 interactions. Of 101,017 compounds screened, six inhibit LIN28:let-7 binding and impair LIN28-mediated let-7 oligouridylation. Upon further characterization, we demonstrate that the LIN28 inhibitor TPEN destabilizes the zinc-knuckle domain of LIN28, while LI71 binds the cold shock domain to suppress LIN28’s activity against let-7 in leukemia cells and embryonic stem cells. Our results demonstrate selective pharmacologic inhibition of individual domains of LIN28 and provide a foundation for therapeutic inhibition of the let-7 biogenesis pathway in LIN28-driven diseases.

Targeting PIM kinase as a therapeutic strategy in human hepatoblastoma.

Increasing incidence coupled with poor prognosis and treatments that are virtually unchanged over the past 20 years have made the need for the development of novel therapeutics for hepatoblastoma imperative. PIM kinases have been implicated as drivers of tumorigenesis in multiple cancers, including hepatocellular carcinoma. We hypothesized that PIM kinases, specifically PIM3, would play a role in hepatoblastoma tumorigenesis and that PIM kinase inhibition would affect hepatoblastoma in vitro and in vivo. Parameters including cell survival, proliferation, motility, and apoptosis were assessed in human hepatoblastoma cells following PIM3 knockdown with siRNA or treatment with the PIM inhibitor AZD1208. An in vivo model of human hepatoblastoma was utilized to study the effects of PIM inhibition alone and in combination with cisplatin. PIM kinases were found to be present in the human hepatoblastoma cell line, HuH6, and in a human hepatoblastoma patient-derived xenograft, COA67. PIM3 knockdown or inhibition with AZD1208 decreased cell survival, attachment independent growth, and motility. Additionally, inhibition of tumor growth was observed in a hepatoblastoma xenograft model in mice treated with AZD1208. Combination therapy with AZD1208 and cisplatin resulted in a significant increase in animal survival when compared to either treatment alone. The current studies showed that PIM kinase inhibition decreased human hepatoblastoma tumorigenicity both in vitro and in vivo, implying that PIM inhibitors may be useful as a novel therapeutic for children with hepatoblastoma.

Validation of Arid1a as a Mammary Tumor Driver in Mice

Distinguishing commonly deleted genes as drivers or passengers of human cancers are key to delineating mechanisms of tumor initiation. The “Chaos3” mouse model of spontaneous breast cancer carries a missense mutation in MCM4 (minichromosome maintenance 4), causing destabilization of the MCM2‐7 replicative helicase, which in turn causes elevated genomic instability. Approximately 80% of female mice homozygous for this mutation in the C3H/FeJ background develop mammary tumors with an average latency of 12 months. Genomic analysis of these tumors revealed that ~70% had monoallelic deletion of tumor suppressor Arid1a. Arid1a is a member of the SWI/SNF chromatin remodeling complex and is responsible for conferring specificity of SWI/SNF complexes to their targets. Previous studies in the lab have shown that introduction of a second Arid1a allele in monoallelically deleted, cultured tumor cells rescued the tumorgenic phenotype following transplantation into host mammary glands. We propose that deletion of Arid1a early in postnatal development is one driver of Chaos3 mammary tumors. Here, we will perform intraductal mammary injections of adeno‐cre virus into Chaos3 females bearing a floxed Arid1a allele. Loss of Arid1a has been implicated as a driver of tumorigenesis in many cancers such as clear cell ovarian carcinoma and endometrioid carcinoma, and is deleted in ~5–11% of human breast cancers. Identifying Arid1a as a driver of mammary tumors in Chaos3 mice would validate its potential role in development of sporadic breast cancer in people.Support or Funding InformationBreast Cancer Coalition of RochesterThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Targeted inhibition of Hedgehog-GLI signaling by novel acylguanidine derivatives inhibits melanoma cell growth by inducing replication stress and mitotic catastrophe

Aberrant activation of the Hedgehog (HH) signaling is a critical driver in tumorigenesis. The Smoothened (SMO) receptor is one of the major upstream transducers of the HH pathway and a target for the development of anticancer agents. The SMO inhibitor Vismodegib (GDC-0449/Erivedge) has been approved for treatment of basal cell carcinoma. However, the emergence of resistance during Vismodegib treatment and the occurrence of numerous side effects limit its use. Our group has recently discovered and developed novel and potent SMO inhibitors based on acylguanidine or acylthiourea scaffolds. Here, we show that the two acylguanidine analogs, compound (1) and its novel fluoride derivative (2), strongly reduce growth and self-renewal of melanoma cells, inhibiting the level of the HH signaling target GLI1 in a dose-dependent manner. Both compounds induce apoptosis and DNA damage through the ATR/CHK1 axis. Mechanistically, they prevent G2 to M cell cycle transition, and induce signs of mitotic aberrations ultimately leading to mitotic catastrophe. In a melanoma xenograft mouse model, systemic treatment with 1 produced a remarkable inhibition of tumor growth without body weight loss in mice. Our data highlight a novel route for cell death induction by SMO inhibitors and support their use in therapeutic approaches for melanoma and, possibly, other types of cancer with active HH signaling.

Curcumol Controls Choriocarcinoma Stem-Like Cells Self-Renewal via Repression of DNA Methyltransferase (DNMT)- and Histone Deacetylase (HDAC)-Mediated Epigenetic Regulation.

BackgroundCancer stem cells (CSCs), in choriocarcinoma and other carcinomas, possess the ability of self-renewal and multilineage differentiation potential. We previous isolated choriocarcinoma cancer stem-like cells (CSLCs), which hold the stemness characteristics of CSCs. Epigenetic modifications have emerged as drivers in tumorigenesis, but the mechanisms of CSCs are largely unknown, and new drug therapies are needed to break the persistence of CSCs.Material/MethodsQuantitative real-time PCR (qRT-PCR) and Western blot analysis were performed to detect the expression of DNMTs, HDACs, and stemness-genes. DNMTs and HDACs silencing and overexpressing lentivirus were transfected into JEG-3 cells to investigate the epigenetic functions in CSLCs. In vivo expression of curcumol effects of CSLCs on DNMTs and HDACs were analyzed by immunohistochemistry.ResultsExpression of DNMT1, DNMT3b, HDAC1, and HDAC3 were increased in choriocarcinoma CSLCs. Consistent with the inhibitory effect of 5-AzaC and TSA on CSLCs, DNMT/HDAC knockdown displayed significant repression of self-renewal in CSLCs. Curcumol inhibited the stemness ability of CSLCs in vitro and in vivo, and the inhibitory effect we observed was mediated in part through repressing activity of DNMTs and HDACs. Importantly, curcumol showed a better effect than DNMT and HDAC inhibitors combined in eliminating CSLCs.ConclusionsThese findings indicate that DNMT- and HDAC-mediated epigenetic regulation plays an important role in the biology of choriocarcinoma CSLCs, and curcumol has the potential to be a new drug to fight CSLCs, warranting further investigation of epigenetic-based therapies.

Emerging functions of the EGFR in cancer.

The physiological function of the epidermal growth factor receptor (EGFR) is to regulate epithelial tissue development and homeostasis. In pathological settings, mostly in lung and breast cancer and in glioblastoma, the EGFR is a driver of tumorigenesis. Inappropriate activation of the EGFR in cancer mainly results from amplification and point mutations at the genomic locus, but transcriptional upregulation or ligand overproduction due to autocrine/paracrine mechanisms has also been described. Moreover, the EGFR is increasingly recognized as a biomarker of resistance in tumors, as its amplification or secondary mutations have been found to arise under drug pressure. This evidence, in addition to the prominent function that this receptor plays in normal epithelia, has prompted intense investigations into the role of the EGFR both at physiological and at pathological level. Despite the large body of knowledge obtained over the last two decades, previously unrecognized (herein defined as ‘noncanonical’) functions of the EGFR are currently emerging. Here, we will initially review the canonical ligand‐induced EGFR signaling pathway, with particular emphasis to its regulation by endocytosis and subversion in human tumors. We will then focus on the most recent advances in uncovering noncanonical EGFR functions in stress‐induced trafficking, autophagy, and energy metabolism, with a perspective on future therapeutic applications.