Inhibits Cancer Stem Research Articles

Abstract 31: Targeted dissociation of PF1 from SIN3A chromatin regulator complex inhibits tumor growth and metastasis in triple-negative breast cancer

Abstract Triple negative breast cancer (TNBC) is characterized by an aggressive, poorly differentiated phenotype associated with early recurrence. Chemotherapy is the only treatment option due to the lack of an effective molecular target. Targeting reversible epigenetic alterations in TNBC to reprogram the TNBC phenotype may increase chemosensitivity and identify effective targeted therapies. The SIN3 chromatin modifier complex is a multidomain scaffold protein which plays a key role in multiple cellular functions including epigenetic gene expression regulation, making SIN3 a potential therapeutic target. The PAH-2 domain of SIN3 binds with different affinities to a group of proteins that contain variations of an amino acid sequence known as the SIN3 interaction domain (SID). We previously reported the effects of blocking PAH-2 interaction with MAD-1, a SID sequence containing protein by using SID peptides and small molecule inhibitors (SMI) as decoys. We now report the effects of blocking the PAH-2 binding of PF1 and TGIF1, two other Sin3 interacting proteins with different amino acid sequence and PAH-2 binding affinities. Treatment with MAD-1 SID peptide and SMI revert the epithelial to mesenchymal transition (EMT) process, inhibit cancer stem cells expansion, cell invasion, tumor growth and metastasis development in human and mouse models of TNBC. TGIF1 interaction with SIN3 is associated with the invasive phenotype and EMT regulation by modulating wnt signaling and inhibiting beta catenin nuclear localization which is reverted by TGIF1 knockdown. PF1, which binds MRG15 and KDM5A/B, an epigenetic modifier, is involved in the regulation of cancer stem cell compartment expansion, DNA damage control, senescence, apoptosis and the expression of genes involved in metastatic progression. Interestingly, decrease in H3K4me3 is found in stem cell and EMT genes following 72 hour SID peptide treatment. PF1 dissociation from Sin3 by transfecting MDA-MB-231 and 4T1 cells with a PF1-SID expressing vector grown in 3D morphogenesis cultures display the formation of small organoids in the MDA-MB-231PF1-SID and tubular morphogenesis in the 4T1PF1-SID cells. There is increased activated caspase-3 and γH2AX, reduced Ki67, tenascin-C and marked cortical actin reorganization. This is accompanied by small organized colonies with loss of invasive and proliferative phenotype. In vivo, 4T1PF1-SID barely form tumors and have a 95% decrease in lung metastasis. These results show that decoys can be designed to block specific proteins that bind to the PAH-2 domain resulting in different outcomes which contribute to a common effect on inhibition of tumor progression and metastasis dissemination. Therefore, this strategy opens a potential therapeutic alternative for TNBC patients for whom there are no other therapeutic options besides chemotherapy. Citation Format: Rama Kadamb, Nidhi Bansal, Boris A Leibovitch, Yeon-Jin Kwon, Ming-Ming Zhou, Eduardo Farias, Samuel Waxman. Targeted dissociation of PF1 from SIN3A chromatin regulator complex inhibits tumor growth and metastasis in triple-negative breast cancer [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 31.

Abstract LB-051: An Astragalus-based Chinese herbal medicine extraction inhibits cancer stem cell growth and sensitizes of drug-resistant human non-small cell lung cancer cells for targeted therapy

Abstract Chinese herbal medicine has been used extensively as a complementary intervention for many diseases including cancer, based on its relatively lower cytotoxicity and side-effects. The major criticism of its clinical use remains the scientific based evidence. Here, we described a precision-based translational approach to identify and validate an Astragalus-based herbal medicine (YQ1) as an antagonist of non-small cell lung cancer. Using various big data analysis approaches, we found that the L1000 profiles of YQ1was associated with anti-cancer stem cell signatures. It suggested that treatment of YQ1 might reduce cancer stem cell population. Experimentally, YQ1 treatment resulted in the significant reduction in lung cancer stem cell properties, including side population, sphere formation, stemness marker expression, and drug resistance. YQ1 may have anti-cancer stem cell ability via suppressing Wnt/β-catenin signaling to inhibit the self-renewal or/and proliferation of lung cancer stem cells. Notably, the combination of YQ1 and gefitinib significantly suppresses tumorigenesis in vivo, reflected by the down-regulation of EGFR signaling and β-catenin. Collectively, we provided preclinical evidence for using YQ1 as a cancer stem cell inhibitor to potentiate anti-tumor effects when combined with tyrosine-kinase inhibitors to significantly improve therapeutic efficacy in NSCLC patients. Citation Format: Tse-Hung Huang, Hsuan-Min Hsu, Chi-Ying F. Huang. An Astragalus-based Chinese herbal medicine extraction inhibits cancer stem cell growth and sensitizes of drug-resistant human non-small cell lung cancer cells for targeted therapy [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 LB-051.

Ubiquitin-specific protease 22 acts as an oncoprotein to maintain glioma malignancy through deubiquitinating B cell-specific Moloney murine leukemia virus integration site 1 for stabilization.

Ubiquitin‐specific protease 22 (USP22) is a member of the “death‐from‐cancer” signature, which plays a key role in cancer progression. Previous evidence has shown that USP22 is overexpressed and correlates with poor prognosis in glioma. The effect and mechanism of USP22 in glioma malignancy, especially cancer stemness, remain elusive. Herein, we find USP22 is more enriched in stem‐like tumorspheres than differentiated glioma cells. USP22 knockdown inhibits cancer stemness in glioma cell lines. With a cell‐penetrating TAT‐tag protein, B cell‐specific Moloney murine leukemia virus integration site 1 (BMI1), a robust glioma stem‐cell marker, is found to mediate the effect of USP22 on glioma stemness. By immunofluorescence, USP22 and BMI1 are found to share similar intranuclear expression in glioma cells. By analysis with immunohistochemistry and bioinformatics, USP22 is found to positively correlate with BMI1 at the post‐translational level only rather than at the transcriptional level. By immunoprecipitation and in vivo deubiquitination assay, USP22 is found to interact with and deubiquitinate BMI1 for protein stabilization. Microarray analysis shows that USP22 and BMI1 mutually regulate a series of genes involved in glioma stemness such as POSTN,HEY2,PDGFRA and ATF3. In vivo study with nude mice confirms the role of USP22 in promoting glioma tumorigenesis by regulating BMI1. All these findings indicate USP22 as a novel deubiquitinase of BMI1 in glioma. We propose a working model of the USP22‐BMI1 axis, which promotes glioma stemness and tumorigenesis through oncogenic activation. Thus, targeting USP22 might be an effective strategy to treat glioma especially in those with elevated BMI1 expression.

Nobiletin Inhibits CD36-Dependent Tumor Angiogenesis, Migration, Invasion, and Sphere Formation Through the Cd36/Stat3/Nf-Κb Signaling Axis.

Targeted cancer therapy with natural compounds is more effective than nontargeted therapy. Nobiletin is a flavonoid derived from citrus peel that has anticancer activity. Cluster of differentiation 36 (CD36) is a member of the class B scavenger receptor family that is involved in importing fatty acids into cells. CD36 plays a role in tumor angiogenesis by binding to its ligand, thrombospondin-1 (TSP-1), and then interacting with transforming growth factor beta 1 (TGFβ1). CD36 is implicated in tumor metastasis through its roles in fatty acid metabolism. This study investigated the molecular mechanisms underlying nobiletin’s anticancer activity by characterizing its interactions with CD36 as the target molecule. We hypothesize that the anti-angiogenic activity of nobiletin involving its regulation of CD36 via signal transducer and activator of transcription 3 (STAT3) rather than through TSP-1. Gene analysis identified a Gamma interferon activation site (GAS) element in the CD36 gene promoter that acts as a STAT3 binding site, an interaction that was confirmed by ChIP assay. STAT3 interacts with nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), suggesting that nobiletin also acts through the CD36/ (STAT3)/NF-κB signaling axis. Nobiletin inhibited CD36-dependent breast cancer cell migration and invasion as well as CD36-mediated tumor sphere formation. Taken together, these results suggest that nobiletin inhibits cancer stem cells in multiple ways.

Histone methyltransferase SETD2 regulates osteosarcoma cell growth and chemosensitivity by suppressing Wnt/β-catenin signaling

SETD2 is a histone methyltransferase that catalyzes the trimethylation of lysine 36 on histone 3. SETD2 is frequently found to be mutated or deleted in a variety of human tumors, whereas the role of SETD2 in oncogenesis of osteosarcoma has never been defined. Here in our study, we uncovered that SETD2 regulates tumor growth and chemosensitivity of osteosarcoma. Overexpression of SETD2 significantly inhibited osteosarcoma cell growth in vitro and in vivo. Moreover, SETD2 significantly enhanced cisplatin-induced apoptosis in osteosarcoma cells and inhibited cancer stem cell properties in OS cells. SETD2 regulates Wnt/β-catenin signaling and its downstream gene c-myc, CD133 and cyclin D1. We further revealed that SETD2 upregulates H3K36me3 modification in GSK3B loci and promotes its transcription, which lead to β-catenin degradation. Together, our study delineates SETD2 function in osteosarcoma as an important regulator of Wnt/β-catenin signaling, and suggests SETD2 as a novel target in diagnosis and combined chemotherapy of osteosarcoma.

Phase 1b/2 trial of cancer stemness inhibitor napabucasin (NAPA) + nab-paclitaxel (nPTX) and gemcitabine (Gem) in metastatic pancreatic adenocarcinoma (mPDAC).

4110Background: NAPA is an oral investigational agent, hypothesized to inhibit cancer stemness pathways, including STAT3 pathway implicated in cancer stem-cell viability. We report updated data in ...

The BRIGHTER trial: A phase 3 randomized double-blind study of napabucasin (NAPA) plus paclitaxel (PTX) versus placebo (PBO) plus PTX in patients (pts) with pretreated advanced gastric and gastroesophageal junction (GEJ) adenocarcinoma.

4010Background: NAPA is an oral investigational agent, hypothesized to inhibit cancer stemness pathways, including STAT3 pathway implicated in cancer stem-cell viability. Synergistic antitumor acti...

A phase 1b study of napabucasin (NAPA) + weekly paclitaxel (PTX) in patients (pts) with advanced thymoma and thymic carcinoma.

e20578Background: NAPA is an oral investigational agent, hypothesized to inhibit cancer stemness pathways, including the STAT3 pathway implicated in cancer stem-cell viability. A clinical trial eva...

BBI608 inhibits cancer stemness and reverses cisplatin resistance in NSCLC

Non-small cell lung cancer (NSCLC) is the most common cause of cancer-related deaths worldwide. While partial or complete tumor regression can be achieved in patients, particularly with cisplatin-based strategies, these initial responses are frequently short-lived and are followed by tumor relapse and chemoresistance. Identifying the root of cisplatin resistance in NSCLC and elucidating the mechanism(s) of tumor relapse, is of critical importance in order to determine the point of therapeutic failure, which in turn, will aid the discovery of novel therapeutics, new combination strategies and a strategy to enhance the efficacy of current chemotherapeutics. It has been hypothesized that cancer stem cells (CSCs) may be the initiating factor of resistance. We have previously identified and characterized an aldehyde dehydrogenase 1 CSC subpopulation in cisplatin resistant NSCLC. BBI608 is a small molecule STAT3 inhibitor known to suppress cancer relapse, progression and metastasis. Here, we show that BBI608 can inhibit stemness gene expression, deplete CSCs and overcome cisplatin resistance in NSCLC.

Cancer Chemoprevention and Piperine: Molecular Mechanisms and Therapeutic Opportunities.

Cancer is a genetic disease characterized by unregulated growth and dissemination of malignantly transformed neoplastic cells. The process of cancer development goes through several stages of biochemical and genetic alterations in a target cell. Several dietary alkaloids have been found to inhibit the molecular events and signaling pathways associated with various stages of cancer development and therefore are useful in cancer chemoprevention. Cancer chemoprevention has long been recognized as an important prophylactic strategy to reduce the burden of cancer on health care system. Cancer chemoprevention assumes the use of one or more pharmacologically active agents to block, suppress, prevent, or reverse the development of invasive cancer. Piperine is an active alkaloid with an excellent spectrum of therapeutic activities such as anti-oxidant, anti-inflammatory, immunomodulatory, anti-asthmatic, anti-convulsant, anti-mutagenic, antimycobacterial, anti-amoebic, and anti-cancer activities. In this article, we made an attempt to sum up the current knowledge on piperine that supports the chemopreventive potential of this dietary phytochemical. Many mechanisms have been purported to understand the chemopreventive action of piperine. Piperine has been reported to inhibit the proliferation and survival of many types of cancer cells through its influence on activation of apoptotic signaling and inhibition of cell cycle progression. Piperine is known to affect cancer cells in variety of other ways such as influencing the redox homeostasis, inhibiting cancer stem cell (CSC) self-renewal and modulation of ER stress and autophagy. Piperine can modify activity of many enzymes and transcription factors to inhibit invasion, metastasis, and angiogenesis. Piperine is a potent inhibitor of p-glycoprotein (P-gp) and has a significant effect on the drug metabolizing enzyme (DME) system. Because of its inhibitory influence on P-gp activity, piperine can reverse multidrug resistance (MDR) in cancer cells and acts as bioavailability enhancer for many chemotherapeutic agents. In this article, we emphasize the potential of piperine as a promising cancer chemopreventive agent and the knowledge we collected in this review can be applied in the strategic design of future researches particularly human intervention trials with piperine.

Napabucasin versus placebo in refractory advanced colorectal cancer: a randomised phase 3 trial

Napabucasin is a first-in-class cancer stemness inhibitor that targets STAT3, which is a poor prognostic factor in colorectal cancer. This study aimed to test napabucasin in advanced colorectal cancer. This study was a double-blind randomised phase 3 trial done at 68 centres in Canada, Australia, New Zealand, and Japan. Patients with advanced colorectal cancer with a good Eastern Cooperative Oncology Group (ECOG) performance status (0-1) for whom all available standard therapies had failed were eligible for the study. Patients were randomly assigned (1:1) to receive placebo or napabucasin through a web-based system with a permuted block method, after stratification by ECOG performance status, KRAS status, previous VEGF inhibitor treatment, and time from diagnosis of metastatic disease. Napabucasin 480 mg or matching placebo was taken orally every 12 h. All patients received best supportive care. The primary endpoint was overall survival assessed in an intention-to-treat analysis. This is the final analysis of this trial, which is registered at ClinicalTrials.gov, number NCT01830621. Accrual began on April 15, 2013, and was stopped for futility on May 23, 2014, at which point 282 patients had undergone randomisation (138 assigned to the napabucasin group and 144 to the placebo group). Overall survival did not differ significantly between groups: median overall survival was 4·4 months (95% CI 3·7-4·9) in the napabucasin group and 4·8 months (4·0-5·3) in the placebo group (adjusted hazard ratio [HR] 1·13, 95% CI 0·88-1·46, p=0·34). The safety population included 136 patients in the napabucasin group and 144 patients in the placebo group. More patients who received napabucasin had any grade of treatment-related diarrhoea (108 [79%] of 136 patients), nausea (69 [51%]), and anorexia (52 [38%]) than did patients who received placebo (28 [19%] of 144 patients, 35 [24%], and 23 [16%], respectively). The most common severe (grade 3 or worse) treatment-related adverse events were abdominal pain (five [4%] patients receiving napabucasin vs five [3%] receiving placebo), diarrhoea (21 [15%] vs one [1%]), fatigue (14 [10%] vs eight [6%]), and dehydration (six [4%] vs one [1%]). 251 (89%) patients had data on pSTAT3 expression, of whom 55 (22%) had pSTAT3-positive tumours (29 in the napabucasin group, 26 in the placebo group). In a prespecified biomarker analysis of pSTAT3-positive patients, overall survival was longer in the napabucasin group than in the placebo group (median 5·1 months [95% CI 4·0-7·5] vs 3·0 months [1·7-4·1]; HR 0·41, 0·23-0·73, p=0·0025). Although there was no difference in overall survival between groups in the overall unselected population, STAT3 might be an important target for the treatment of colorectal cancer with elevated pSTAT3 expression. Nevertheless, these results require validation. Canadian Cancer Society Research Institute and Boston Biomedical.

BRM270 inhibits cancer stem cell maintenance via microRNA regulation in chemoresistant A549 lung adenocarcinoma cells

Chemotherapy is a standard treatment for non-small-cell lung cancer (NSCLC). However, the dose-limiting toxicity of drugs and the development of chemoresistance are major clinical challenges to successful management of NSCLC. Asian traditional medicine is gaining global attention as a non-toxic alternative to chemotherapy. BRM270 is an extract formulated from seven Asian medicinal plants that has been shown to inhibit tumor cell proliferation in diverse cancer types. We previously demonstrated that BRM270 suppresses tumorigenesis by negatively regulating nuclear factor-κB signaling in multidrug-resistant cancer stem cells (CSCs). In this study we report that the growth, migration, and invasion of normal human lung adenocarcinoma cells and their chemoresistant derivatives was inhibited by BRM270 treatment. Notably, BRM270 was found to modulate CSC self-renewal and tumor-initiating capacity via positive regulation of the miRNA-128. Thus, combination therapy with miRNA-128 and BRM270 may be an effective treatment strategy for chemoresistant NSCLC.

Peptide-targeted, stimuli-responsive polymersomes for delivering a cancer stemness inhibitor to cancer stem cell microtumors

Often cancer relapses after an initial response to chemotherapy because of the tumor’s heterogeneity and the presence of progenitor stem cells, which can renew. To overcome drug resistance, metastasis, and relapse in cancer, a promising approach is the inhibition of cancer stemness. In this study, the expression of the neuropilin-1 receptor in both pancreatic and prostate cancer stem cells was identified and targeted with a stimuli-responsive, polymeric nanocarrier to deliver a stemness inhibitor (napabucasin) to cancer stem cells. Reduction-sensitive amphiphilic block copolymers PEG1900-S-S-PLA6000 and the N3-PEG1900-PLA6000 were synthesized. The tumor penetrating iRGD peptide-hexynoic acid conjugate was linked to the N3-PEG1900-PLA6000 polymer via a Cu2+ catalyzed “Click” reaction. Subsequently, this peptide-polymer conjugate was incorporated into polymersomes for tumor targeting and tissue penetration. We prepared polymersomes containing 85% PEG1900-S-S-PLA6000, 10% iRGD-polymer conjugate, and 5% DPPE-lissamine rhodamine dye. The iRGD targeted polymersomes encapsulating the cancer stemness inhibitor napabucasin were internalized in both prostate and pancreatic cancer stem cells. The napabucasin encapsulated polymersomes significantly (p < .05) reduced the viability of both prostate and pancreatic cancer stem cells and decreased the stemness protein expression notch-1 and nanog compared to the control and vesicles without any drug. The napabucasin encapsulated polymersome formulations have the potential to lead to a new direction in prostate and pancreatic cancer therapy by penetrating deeply into the tumors, releasing the encapsulated stemness inhibitor, and killing cancer stem cells.

Breast cancer metastasis suppressor OTUD1 deubiquitinates SMAD7

Metastasis is the main cause of death in cancer patients. TGF-β is pro-metastatic for malignant cancer cells. Here we report a loss-of-function screen in mice with metastasis as readout and identify OTUD1 as a metastasis-repressing factor. OTUD1-silenced cancer cells show mesenchymal and stem-cell-like characteristics. Further investigation reveals that OTUD1 directly deubiquitinates the TGF-β pathway inhibitor SMAD7 and prevents its degradation. Moreover, OTUD1 cleaves Lysine 33-linked poly-ubiquitin chains of SMAD7 Lysine 220, which exposes the SMAD7 PY motif, enabling SMURF2 binding and subsequent TβRI turnover at the cell surface. Importantly, OTUD1 is lost in multiple types of human cancers and loss of OTUD1 increases metastasis in intracardial xenograft and orthotopic transplantation models, and correlates with poor prognosis among breast cancer patients. High levels of OTUD1 inhibit cancer stemness and shut off metastasis. Thus, OTUD1 represses breast cancer metastasis by mitigating TGF-β-induced pro-oncogenic responses via deubiquitination of SMAD7.

Piperlongumine inhibits cancer stem cell properties and regulates multiple malignant phenotypes in oral cancer.

Piperlongumine (PL), a natural product of Piper longum, inhibits multiple malignant phenotypes. Therefore, the present study examined whether PL suppresses cancer stemness in oral cancer. The cellular effects of PL were determined by examining alterations in tumor sphere formation, cell migration, invasion, proliferation ability, chemosensitivity and radiosensitivity. Reverse transcription-quantitative polymerase chain reaction analysis and western blotting were performed in order to determine molecular expression levels. The present study revealed that PL inhibited cancer stem cell-forming ability and suppressed the expression of the stemness-related transcription factors SRY-Box 2, POU class 5 homeobox 1, and Nanog homeobox. However, it increased the expression of the differentiation marker cytokeratin 18. PL also suppressed cell migration and invasion, resulting in the elimination of the epithelial-mesenchymal transition. Furthermore, PL increased chemo- and radiosensitivity and suppressed tumor growth in vitro and in vivo. The results of the present study suggested that PL inhibits malignant phenotypes via the suppression of cancer stemness in oral cancer. Thus, PL may serve as an effective therapeutic agent for oral cancer.

BTG2 Is Down-Regulated and Inhibits Cancer Stem Cell-Like Features of Side Population Cells in Hepatocellular Carcinoma.

Our previous study found that B cell translocation gene 2 (BTG2) was hyper-methylated and down-regulated in side population (SP) cells of hepatocellular carcinoma (HCC) cell line. However, its clinical significances and biological impacts on HCC SP cells remained unclear. To investigate the prognostic value of BTG2 gene in HCC and its influences on cancer stem cells (CSCs)-like traits of HCC cell line SP cells. BTG2 expression in human HCC and adjacent non-cancerous tissues was detected by immunohistochemical staining and quantitative real-time PCR, and also obtained from GEO and TCGA data. Its prognostic values were assessed. Its biological influences on HCC cell line SP cells were evaluated using cell viability, cell cycle, plate clone-forming assay, and chemoresistance in vitro and tumorigenicity in vivo. BTG2 expression was significantly suppressed in human HCC compared to adjacent non-cancerous tissues. BTG2 expression was correlated with TNM stage, tumor size and vascular invasion. Lower expression of BTG2 was associated with poorer overall survival and disease-free survival. In vitro, overexpression of BTG2 substantially suppressed cell proliferation and accumulation of HCC cell line SP cells in G0/G1 phase. Colony formation ability was markedly suppressed by BTG2 overexpression. Moreover, sensitivity of HCC cell line SP cells to 5-fluorouracil was substantially increased by overexpression of BTG2. Furthermore, tumorigenicity of HCC cell line SP cells transfected with BTG2 plasmids was significantly reduced in vivo. BTG2 gene could regulate the CSC-like traits of HCC cell line SP cells, and it represented as a molecular prognostic marker for HCC.

Mitoketoscins: Novel mitochondrial inhibitors for targeting ketone metabolism in cancer stem cells (CSCs)

Previous studies have now well-established that epithelial cancer cells can utilize ketone bodies (3-hydroxybutyrate and aceto-acetate) as mitochondrial fuels, to actively promote tumor growth and metastatic dissemination. The two critical metabolic enzymes implicated in this process are OXCT1 and ACAT1, which are both mitochondrial proteins. Importantly, over-expression of OXCT1 or ACAT1 in human breast cancer cells is sufficient to genetically drive tumorigenesis and/or lung metastasis, validating that they indeed behave as metabolic “tumor promoters”. Here, we decided to target these two enzymes, which give cancer cells the ability to recycle ketone bodies into Acetyl-CoA and, therefore, to produce increased ATP. Briefly, we used computational chemistry (in silico drug design) to select a sub-set of potentially promising compounds that spatially fit within the active site of these enzymes, based on their known 3D crystal structures. These libraries of compounds were then phenotypically screened for their effects on total cellular ATP levels. Positive hits were further validated by metabolic flux analysis. Our results indicated that four of these compounds effectively inhibited mitochondrial oxygen consumption. Two of these compounds also induced a reactive glycolytic phenotype in cancer cells. Most importantly, using the mammosphere assay, we showed that these compounds can be used to functionally inhibit cancer stem cell (CSC) activity and propagation. Finally, our molecular modeling studies directly show how these novel compounds are predicted to bind to the active catalytic sites of OXCT1 and ACAT1, within their Coenzyme A binding site. As such, we speculate that these mitochondrial inhibitors are partially mimicking the structure of Coenzyme A. Thus, we conclude that OXCT1 and ACAT1 are important new therapeutic targets for further drug development and optimization. We propose that this new class of drugs should be termed “mitoketoscins”, to reflect that they were designed to target ketone re-utilization and mitochondrial function.

Blocking of STAT3 activation by miR-491, acting via EGFR, is involved in metastasis of hepatocellular carcinoma cells through inhibiting cancer stem cell-like properties

Blocking of STAT3 activation by miR-491, acting via EGFR, is involved in metastasis of hepatocellular carcinoma cells through inhibiting cancer stem cell-like properties

Abstract 4777: Cancer stemness and resistance: Napabucasin (BBI-608) sensitizes stemness-high cancer cells to Paclitaxel by inhibiting the STAT3-MUC1 pathway

Abstract Stemness-high cancer cells, or cancer stem cells (CSC) represent a subpopulation of cancer cells with enhanced tumorigenic capacity, metastasis-forming potential, and resistance to conventional chemotherapy and radiation. One such key CSC pathway is regulated by STAT3, a transcription factor that is downstream of several cytokines and growth factor receptors which controls the expression of a broad range of target genes and plays essential roles in CSC biology in many tumor types. Cancer stemness inhibitor Napabucasin (BBI-608), a small molecule that inhibits gene transcription driven by STAT3, can inhibit stemness gene expression, block spherogenesis, and kill CSCs. In vivo, BBI-608 effectively blocks cancer relapse and metastasis in xenograft models while sparing normal hematopoietic stem cells, suggesting that targeting stemness-high cancer cells is a feasible approach for developing next-generation cancer therapeutics to combat cancer recurrence. SOX2 (sex-determining region Y-box protein 2), a transcription factor that is essential for self-renewal and pluripotency, is amplified in various cancer types and has been shown to be required for CSC self-renewal and maintenance. Mucin 1 (MUC1), a glycoprotein normally expressed at the apical surface of epithelial cells, is overexpressed in most human epithelial cancers. MUC1 has been implicated in regulating tumor proliferation, metabolism, invasion, angiogenesis, chemoresistance, and inflammation. Here, we generated a stemness-high culture system based on the reporter activity of a SOX2-regulatory region construct in MKN28 gastric cancer cells (MKN28 SOX2-reporter GFP+ cells). BBI-608 treatment inhibited the STAT3-MUC1 pathway in stemness-high cells. High MUC1 status in stemness-high cells was associated with Paclitaxel resistance. Down-regulation of MUC1 sensitized stemness-high cells to Paclitaxel. Moreover, BBI-608 synergized with Paclitaxel in inhibiting spherogenesis of stemness-high cells. This study provides a new mechanism for the association of cancer stemness with drug resistance. Our findings support this combination therapy, which pairs a conventional chemotherapy (Paclitaxel) with a cancer stemness inhibitor (BBI-608), as a promising strategy to combat cancer. Citation Format: Harry A. Rogoff, Juying Li, Chiang Li. Cancer stemness and resistance: Napabucasin (BBI-608) sensitizes stemness-high cancer cells to Paclitaxel by inhibiting the STAT3-MUC1 pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4777. doi:10.1158/1538-7445.AM2017-4777

Abstract LB-142: Identification of STK33 as a cancer stemness kinase and regulator of Nanog function

Abstract In recent years evidence has accumulated in support of the cancer stem cell (CSC) model in cancer chemotherapy resistance, highlighting the urgency and necessity of identifying CSC targets for developing novel cancer therapeutics. A number of studies have suggested that Nanog is a crucial factor that can confer stemness properties to a portion of the heterogeneous cancer cell population. Although latent in normal somatic cells, aberrant expression of Nanog has been reported in many types of human cancers. Importantly, the expression levels of Nanog are often positively correlated with treatment resistance and poor survival of cancer patients. Various studies have shown that upregulation of Nanog expression enhances the tumorigenicity both in vivo and in vitro whereas repression or ablation of Nanog inhibits tumor initiation. Thus, expression of the stemness factor Nanog is linked to tumor progression, therapeutic resistance, relapse and metastasis. However, Nanog is considered a non-druggable target. Here we provide data to support a role for STK33 (Serine Threonine Kinase 33) as a novel regulator of Nanog and as a potential therapeutic target. Ectopic STK33 expression promotes stemness phenotypes of cancer cells and increases expression levels of CSC drivers including Nanog, KLF4, and SOX2. On the other hand, knockdown of STK33 inhibits expression of Nanog and results in a reduction of the stemness phenotype. STK33 directly interacts with Nanog and appears to promote its stabilization through phosphorylation, resulting in increased Nanog transcriptional activity. Moreover, BBI-503 (Amcasertib), a first-in-class cancer stemness inhibitor, potently inhibits STK33, which led to inhibition of phosphorylation of Nanog. Collectively, our data demonstrate STK33 is a critical element in the signaling network that governs the stemness of cancer cells, and as a promising therapeutic target for cancer. Citation Format: Susan L. Tran, Yudai Furuta, Chen Zhu, Ao Yang, Xiangao Sun, Harry A. Rogoff, Chiang J. Li. Identification of STK33 as a cancer stemness kinase and regulator of Nanog function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-142. doi:10.1158/1538-7445.AM2017-LB-142