Expression Of Cancer Stem Cells Research Articles

Abstract 6353: Cholesterol modification enhances potency and pharmacokinetic properties of a selective cancer stem cell targeting agent

Abstract Increasing evidence supports the concept that tumor-initiating cancer stem cells (CSCs) are responsible for the relapse and reconstitution of formerly treated tumors. Previously, our lab identified a potent and selective inhibitor of colorectal CSCs, named G2.2, from a library of non-saccharide glycosaminoglycan mimetics (NSGMs). To further improve upon the potency, pharmacokinetics, and drug-like properties of G2.2, cholesterol-modified analogs were rationally designed using computational molecular modeling and molecular dynamics studies. A small group of designed NSGMs, labeled as G2C, G5C and G8C, were synthesized for biological evaluation. These agents and the parent NSGM G2.2 were studied for their ability to inhibit the growth of primary spheroids from a panel of 15 human colorectal cancer (CRC) cells representative of the consensus molecular subtypes of human CRC. Spheroid formation frequencies (SFFs) of cell lines were measured using limiting dilution assays (LDAs), and IC50 of inhibition was evaluated from dose-response curves for monolayer growth and primary spheroid growth in the presence of NSGMs. Selectivity of CSC targeting was assessed from the ratio of IC50,monolayer to IC50,spheroid. Pharmacokinetics (PK) and bioavailability in rodents were deduced following IV and PO administrations. In-vivo therapeutic potential of the NSGMs was studied in CSC-induced xenograft models aided by ex-vivo CSC phenotype characterization. Each NSGM preferentially targeted 3D spheroidal growth in comparison to monolayer cellular growth by 12- to 450-fold, suggesting excellent CSC selectivity. Cholesterol modification of G2.2 enhanced in-vitro spheroid inhibition potency across the entire panel of cell lines on average by 3- to 21-fold. G8C showed the highest inhibition potency with an IC50 of 1 to 10 μM across cell lines. Cells with higher SFF were several-fold more sensitive to NSGMs, suggesting that basal expression of CSCs could predict NSGM response. Robust reductions in tumor volumes were observed in mice treated with G5C (100 mg/kg i.p. 3x a week) following an intial-treatment with oxaliplatin and 5-fluorouracil (weekly x3) compared to vehicle controls. This reduction was concomitant with a 3.9-fold reduction in colonic crypt stemness marker LGR5+ cells and 2.6-fold decrease in xenograft-derived tertiary spheroids. No gross or organ specific toxicity was found in animals treated with G5C. Finally, cholesterol modification greatly improved PK and oral bioavailability of parent G2.2. Overall, cholesterol modification of CSC-selective G2.2 was found to enhance in vitro potency against spheroidal growth without compromising selectivity toward tumor initiating CSCs. The G2.2 analogs offered robust tumor reductions in vivo with essentially no off target toxicity, and serve as promising and novel potential cancer therapeutics. Citation Format: Connor P. O'Hara, Rio S. Boothello, Shravan Morla, Alberto Vera, Daniel K. Afosah, Nehru V. Sankaranarayanan, Balaji Nagarajan, Chetna Sharon, Bhaumik B. Patel, Umesh R. Desai. Cholesterol modification enhances potency and pharmacokinetic properties of a selective cancer stem cell targeting agent [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6353.

Abstract 6022: The relationship of TMEM (tumor microenvironment of metastasis) doorways with breast cancer stem cells

Abstract Background: Breast cancer cells use tumor microenvironment of metastasis (TMEM) doorways as portals for hematogenous dissemination to distant sites. Each TMEM doorway is composed of one perivascular macrophage in direct contact with one endothelial cell and one Mena expressing cancer cell. TMEM density is prognostic of metastatic outcome in breast cancer patients. Since the development of metastases requires tumor initiating properties in cancer cells, and we recently demonstrated that cancer cells expressing cancer stem cell biosensors and other stem cell markers accumulate around TMEM (Sharma et al 2020 AACR abstract), we wanted to assess the relationship between stem cell marker expression and TMEM in mouse and human breast cancer. Methods: We evaluated the distribution of cancer stem cells relative to TMEM doorways in MDA-MB-231breast cancer cell xenografts that express a reporter (SORE6) and in transgenic PyMT mammary carcinomas using Sox9 as marker of stemness. We also evaluated the correlation of the percentage of cancer cells expressing stem cell markers (CD44high/CD24low, CD133, ALDH, and Sox9) with TMEM and the distribution of cancer cells expressing stem cell markers relative to TMEM in 49 breast cancers collected from patients. The stem cell markers were assessed by flow cytometry, fluorescence in situ hybridization (FISH), and qRT-PCR in Fine Needle Aspirates (FNA), as well as in fixed tissues by immunofluorescence assay. TMEM density was assessed in corresponding formalin-fixed and paraffin-embedded (FFPE) tumors by immunohistochemistry. The correlation of TMEM with stemness and the distance analysis of stem cells relative to TMEM was evaluated by Spearman's and Pearson's rank correlation respectively. Results: We observed a 7- and 3.4-fold enrichment of cancer stem cells (CSCs) close to TMEM (<200µm) compared to away from TMEM in MDA-MB-231 xenografts and PyMT tumors respectively. This CSC enrichment was specific to TMEM doorways, as we did not see any enrichment of CSCs around blood vessels lacking TMEMs. In breast cancer patients, we also observed strong positive correlation between percentage of CD44high/CD24low cells and TMEM scores (r=0.91), as well as the percentage of CD133 and ALDH1 expressing cells with TMEM scores (r=0.88 and 0.86 respectively). FISH results were validated using qRT-PCR and showed very strong correlation with TMEM scores (r=0.76 and 0.73 for CD133 and ALDH1 respectively). Moreover, we found strong positive correlation between TMEM and Sox9 and CD133 (r=0.84 and 0.47 respectively) in FFPE tissues. Conclusion: The density of TMEM doorways positively correlates with the number of cancer stem cells in human breast cancer. Moreover, stem cells accumulate around TMEM consistent with the findings that TMEM doorways represent an educational niche for stemness in breast cancer. Citation Format: Gina Kim, Ved P. Sharma, Gargi Bandyopadhyaya, Eli Grunblatt, Sweta Roy, Nathan Agi, Binwu Tang, Esther Adler, Joan Jones, George S. Karagiannis, Xianjun Ye, David Entenberg, Sumanta Goswami, Lalage Wakefield, John S. Condeelis, Maja H. Oktay. The relationship of TMEM (tumor microenvironment of metastasis) doorways with breast cancer stem cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6022.

Irradiated mesenchymal stem cells support stemness maintenance of hepatocellular carcinoma stem cells through Wnt/\u03b2-catenin signaling pathway

BackgroundCancer stem cells are the main reason of relapse, metastasis and resistance to anti-cancer therapies of Hepatocellular carcinoma (HCC). Mesenchymal stem cells (MSCs) are an important part of the tumor microenvironment. MSCs have been demonstrated to be involved in drug resistance in tumor. How MSCs contribute to radiotherapy resistance of HCC is still indistinct.MethodsFlow cytometry analysis was performed to isolate CD133+ cells from HCC cell lines Huh7 and PLC. The stemness of Huh7-CD133 and PLC-CD133 those were co-cultured with IR-MSCs were investigated by Colony formation assay. Tumor formation in nude mice was used to explore the tumorigenicity of CD133+ cancer cells. The activating Wnt/β-catenin signaling pathway in CSCs were also detected by RT-PCR and Western blotting.ResultsWe report that irradiated MSCs (IR-MSCs) could increase the ratio of CD133+ cells in hepatocellular carcinoma cells. IR-MSCs could promote stemness maintenance of HCC stem cells. After co-cultured with IR-MSCs, liver cancer stem cells (CSCs) presented increased colony formation ability and tumor formation ability. We also found IR-MSCs promoted Wnt expression of CSCs. Reverse suppression experiment showed that when Wnt inhibitor was added into the culture medium, the effect of IR-MSCs on stemness maintenance was counteracted.ConclusionsThese data showed that IR-MSCs could support stemness maintenance of CSCs by activating Wnt/β-catenin signaling pathway.

Glycosphingolipid expression at breast cancer stem cells after novel thieno[2,3-b]pyridine anticancer compound treatment

Glycosphingolipid expression differs between human breast cancer stem cells (CSC) and cancer non-stem cells (non-CSC). We performed studies of viability, type of cell death, cancer stem cell percent and glycosphingolipid expression on CSC and non-CSC after treatment of MDA-MB-231 and MDA-MB-453 triple-negative breast cancer cells with a newly developed thienopyridine anticancer compound (3-amino-N-(3-chloro-2-methylphenyl)-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide, 1). Compound 1 was cytotoxic for both breast cancer cell lines and the majority of cells died by treatment-induced apoptosis. The percent of cancer stem cells and number of formed mammospheres was significantly lower. Glycosphingolipids IV6Neu5Ac-nLc4Cer and GalNAc-GM1b (IV3Neu5Ac-Gg5Cer) not reported previously, were identified in both CSCs and non-CSCs. IV6Neu5Ac-nLc4Cer had increased expression in both CSCs and non-CSCs of both cell lines after the treatment with 1, while GM3 (II3Neu5Ac-LacCer) had increased expression only on both cell subpopulations in MDA-MB-231 cell line. GalNAc-GM1b, Gb4Cer (GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer) and GM2 (II3Neu5Ac-GalNAcβ1-4Galβ1-4Glcβ1-1Cer) were increased only in CSCs of both cell lines while GD3 was decreased in CSC of MDA-MB-231 cell line. Due to its effect in reducing the percentage of cancer stem cells and number of mammospheres, and its influence upon several glycosphingolipid expressions, it can be concluded that compound 1 deserves attention as a potential new drug for triple-negative breast cancer therapy.

The deubiquitylase UCHL3 maintains cancer stem-like properties by stabilizing the aryl hydrocarbon receptor

Cancer stem cells (CSCs) exhibit highly aggressive and metastatic features and resistance to chemotherapy and radiotherapy. Aryl hydrocarbon receptor (AhR) expression varies among non-small cell lung cancers (NSCLCs), and the mechanisms that support abnormal AhR expression in CSCs remain elusive. Here, we identified ubiquitin carboxyl terminal hydrolase L3 (UCHL3), a DUB enzyme in the UCH protease family, as a bona fide deubiquitylase of the AhR in NSCLC. UCHL3 was shown to interact with, deubiquitylate, and stabilize AhR in a manner dependent on its deubiquitylation activity. Moreover, we showed that UCHL3 promotes the stem-like characteristics and potent tumorigenic capacity of NSCLC cells. UCHL3 increased AhR stability and the binding of AhR to the promoter regions of the “stemness” genes ATP-binding cassette subfamily G member 2 (ABCG2), KLF4, and c-Myc. Depletion of UCHL3 markedly downregulated the “stemness” genes ABCG2, KLF4, and c-Myc, leading to the loss of self-renewal and tumorigenesis in NSCLCs. Furthermore, the UCHL3 inhibitor TCID induced AhR degradation and exhibited significantly attenuated efficacy in NSCLC cells with stem cell-like properties. Additionally, UCHL3 was shown to indicate poor prognosis in patients with lung adenocarcinoma. In general, our results reveal that the UCHL3 deubiquitylase is pivotal for AhR protein stability and a potential target for NSCLC-targeted therapy.

Reciprocal Regulation Between Indoleamine 2,3-Dioxigenase 1 and Notch1 Involved in Radiation Response of Cervical Cancer Stem Cells.

Cervical cancer is the fourth most common cancer in women around the world. Cancer stem cells (CSCs) are responsible for cancer initiation, as well as resistance to radiation therapy, and are considered as the effective target of cancer therapy. Indoleamine 2,3-dioxygenase 1 (IDO1) mediates tryptophan metabolism and T cell suppression, but the immune-independent function of IDO1 in cancer behavior is not fully understood. Using tumorsphere cultivation for enriched CSCs, we firstly found that IDO1 was increased in HeLa and SiHa cervical cancer cells and in these two cell lines after radiation treatment. The radiosensitivity of HeLa and SiHa tumorsphere cells was increased after the inhibition of IDO1 through RNA interference or by the treatment of INCB-024360, an IDO1 inhibitor. With the treatment of kynurenine, the first breakdown product of the IDO1-mediated tryptophan metabolism, the radiosensitivity of HeLa and SiHa cells decreased. The inhibition of Notch1 by shRNA downregulated IDO1 expression in cervical CSCs and the binding of the intracellular domain of Notch (NICD) on the IDO1 promoter was reduced by Ro-4929097, a γ-secretase inhibitor. Moreover, the knockdown of IDO1 also decreased NICD expression in cervical CSCs, which was correlated with the reduced binding of aryl hydrocarbon receptor nuclear translocator to Notch1 promoter. In vivo treatment of INCB-0234360 sensitized SiHa xenograft tumors to radiation treatment in nude mice through increased DNA damage. Furthermore, kynurenine increased the tumorsphere formation capability and the expression of cancer stemness genes including Oct4 and Sox2. Our data provide a reciprocal regulation mechanism between IDO1 and Notch1 expression in cervical cancer cells and suggest that the IDO1 inhibitors may potentially be used as radiosensitizers.

CCR9 Promotes Migration and Invasion of Lung Adenocarcinoma Cancer Stem Cells.

Aim: CC chemokine receptor 9 (CCR9) interacts with its exclusive ligand CCL25, resulting in promoting tumor progression and metastasis. However, the effect and mechanisms of CCR9 on lung adenocarcinoma distant metastasis remain largely unknown. To preliminary clarify the underlying mechanisms, we investigate the correlation between CCR9 and ALDH1A1+cancer stem cells (CSCs), as well as the effect of CCR9 on the migration and invasion of CSCs.Methods: Immunohistochemistry was performed to detect the expression of CCR9 in lung adenocarcinoma tissues. The correlations of CCR9 with distant metastasis and overall survival were investigated. Serial paraffin-embedded tissue blocks were used to detect ALDH1A1+CSCs expression. The correlations between CCR9 expression and ALDH1A1+CSCs were evaluated. We further studied the effect of CCR9/CCL25 on the migration and invasion of CSCs using transwell assays.Results: There were positive correlations between CCR9 expression and distant metastasis, as well as poor overall survival. Patients with high CCR9 expression were more likely to develop distant metastasis and demonstrated poorer overall survival than patients with low CCR9 expression. In addition, there was positive correlation between the expression of CCR9 and ALDH1A1 in the same tumor microenvironment. ALDHhigh CSCs demonstrated enhanced expression of CCR9 than ALDHlow cells. Further transwell assays demonstrated that the numbers of CSCs migrated or invaded in response to CCL25 were more than that without CCL25 stimulation. Additional application of anti-CCR9 antibody reversed the CCL25-induced migration and invasion of CSCs.Conclusions: In summary, our study demonstrated that CCR9/CCL25 promoted the migration and invasion of CSCs, which might contribute to distant metastasis and poor overall survival. Our findings provided evidence that CCR9/CCL25 could be used as novel therapeutic targets for lung adenocarcinoma.

MicroRNA: The Impact on Cancer Stemness and Therapeutic Resistance.

Cancer ranks as the second leading cause of death worldwide, causing a large social and economic burden. However, most anti-cancer treatments face the problems of tumor recurrence and metastasis. Therefore, finding an effective cure for cancer needs to be solved urgently. Recently, the discovery of cancer stem cells (CSCs) provides a new orientation for cancer research and therapy. CSCs share main characteristics with stem cells and are able to generate an entire tumor. Besides, CSCs usually escape from current anti-cancer therapies, which is partly responsible for tumor recurrence and poor prognosis. microRNAs (miRNAs) belong to small noncoding RNA and regulate gene post-transcriptional expression. The dysregulation of miRNAs leads to plenty of diseases, including cancer. The aberrant miRNA expression in CSCs enhances stemness maintenance. In this review, we summarize the role of miRNAs on CSCs in the eight most common cancers, hoping to bridge the research of miRNAs and CSCs with clinical applications. We found that miRNAs can act as tumor promoter or suppressor. The dysregulation of miRNAs enhances cell stemness and contributes to tumor metastasis and therapeutic resistance via the formation of feedback loops and constitutive activation of carcinogenic signaling pathways. More importantly, some miRNAs may be potential targets for diagnosis, prognosis, and cancer treatments.

Assessment of cancer stem cell marker expression in primary head and neck squamous cell carcinoma shows prognostic value for aldehyde dehydrogenase (ALDH1A1)

Cancer stem cells (CSCs) play a key role in carcinogenesis and progression of head and neck squamous cell carcinomas (HNSCC). The most common markers indicating for CSCs are: CD44, CD24, CD133, ALDH1A1. Our objective was to evaluate the prognostic potential of CSC markers in HNSCC.The study included 49 patients treated for primary HNSCC, 11 patients with upper respiratory tract epithelial dysplasia and 12 subjects with the normal pharyngeal mucosa as a control group. The frequency and expression levels of the four CSC markers were assessed by immunohistochemistry. Univariate and multivariate analyses were used to correlate CSC expression levels with tumor stage, lymph node metastases or overall survival (OS).CD44, CD24, CD133, ALDH1A1 were widely expressed in tumors, whereas CD44 was found to be higher in cancer tissue (P = 0.001). ALDH1A1 expression levels were found to be significantly higher in T3-T4 tumors vs. T1-T2 tumors (P = 0.05). Lymph node metastases had significantly higher expression levels of CD24 (P = 0.01) and CD133 (P < 0.05) than primary tumors. Multifactorial analysis revealed that overall survival (OS) for patients with ALDH1A1 negative tumors was 5.25 times higher than for patients with ALDH1A1 positive (ALDH1A1+) tumors (P = 0.01). On univariate and multivariate analysis, only ALDH1A1 positivity had a significant effect on OS of HNSCC patients (HR = 2.47 for P = 0.02).Immunohistochemistry-based assessments of CSC marker expression in HNSCC has significant predictive implications for patients with HNSCC. The frequency of CSCs in the tumor, specifically of ALDH1A1+ cells correlated with five-year OS in these patients.

Thy-1 predicts poor prognosis and is associated with self-renewal in ovarian cancer

BackgroundOvarian cancer is the leading cause of gynecologic cancer death in the United States despite effective first-line systemic chemotherapy. Cancer stem cells (CSCs) retain the ability to self-renew and proliferate and may be a means of harboring disease that evades standard treatment strategies. We previously performed a high-throughput screen to assess differential protein expression in ovarian CSCs compared to non-CSCs and observed that Thy-1 was more highly expressed in CSCs. Our primary aim was to validate Thy-1 (CD90) as a cancer stem cell (CSC) marker in epithelial ovarian cancer (EOC), correlate with clinical outcomes, and assess as a potential therapeutic target.ResultsKaplan Meier (KM) Plotter data were correlated with survival outcomes. Quantitative real-time PCR, flow cytometry, and immunoblots assessed RNA and protein expression. Limiting dilution assays assessed self-renewal capacity and proliferation assays assessed proliferative capacity. RNA in-situ hybridization was performed on patient specimens to assess feasibility. Thy-1 (CD90) is more highly expressed in ovarian CSCs than non-CSCs, in EOC compared to benign ovarian epithelium (P < 0.001), and is highest in serous EOC (P < 0.05). Serous ovarian cancers with high Thy-1 expression have poorer outcomes (median PFS 15.8 vs. 18.3 months, P = 0 < 0.001; median OS 40.1 v. 45.8 months, P = 0.036). Endometrioid ovarian cancers with high Thy-1 have poorer PFS, but no difference in OS (upper quartile PFS 34 v. 11 months, P = 0.013; quartile OS not reached, P = 0.69). In vitro, Thy-1 expression is higher in CSCs versus non-CSCs. EOC cells with high Thy-1 expression demonstrate increased proliferation and self-renewal. Thy-1 knockdown in EOC cells decreases proliferative capacity and self-renewal capacity, and knockdown is associated with decreased expression of stem cell transcription factors NANOG and SOX2. RNA in situ hybridization is feasible in ovarian cancer tissue specimens.ConclusionsThy-1 is a marker of ovarian CSCs. Increased expression of Thy-1 in EOC predicts poor prognosis and is associated with increased proliferative and self-renewal capacity. Thy-1 knockdown decreases proliferative and self-renewal capacity, and represents a potential therapeutic target.

Abstract AP26: CANCER STEM CELLS: DISTINCT SEEDS FOR RECURRENT OVARIAN CANCER

Abstract PURPOSE: The treatment of ovarian cancer (OC) with chemotherapy leaves resistant cancer cells which in a short time re-grow as recurrent cancer. A diverse array of resistance mechanisms for chemotherapy has been described but none have proven as viable targets in a clinical setting. Cancer stem cells (CSCs) are increasingly accepted as the putative mediators of chemoresistance and relapse of cancer. This study aimed to understand the molecular mechanisms involved with chemoresistance and recurrence by investigating the proteomic profile of ascites-derived tumor cells obtained from OC patients prior to (chemonaive, CN) and after chemotherapy treatments (recurrent, CR). METHODS: Ascites collected from CN and CR OC patients diagnosed with advanced-stage serous OC were cultured using a novel in vitro method to obtain a distinct population of epithelial tumor cells. Flow cytometry and immunofluorescence were used to characterize the tumor population. High-resolution label-free quantitative proteomic profiling was used to define significantly differentially expressed proteins between CN and CR tumor cells. KEGG and DAVID software's were used to determine pathways associated with CR cells. The mechanisms of survival of cisplatin and paclitaxel-treated OC cancer cells were determined in vitro by mRNA analysis and in vivo mouse xenograft models by immunohistochemistry. RESULTS: Proteomic profiling of CN and CR tumor cells showed significant differences in proteins encoding for CSC, immune surveillance, DNA repair mechanisms, cytoskeleton rearrangement, cell-cell adhesion, cell cycle pathways, cellular transport, and proteins involved with glycine/proline/arginine synthesis in tumor cells isolated from CR relative to CN patients. Pathway analyses revealed enrichment of chemoresistance markers, energy metabolism, DNA repair mechanisms and immune surveillance pathways in recurrent CR tumor cells. Validation of these pathways in OC cell lines and nude mice treated with chemotherapy demonstrated increased expression of CSC and chemoresistant markers, enhancement in glycolytic pathway and oxidative phosphorylation, suppression of immune surveillance in chemotherapy treated cell lines and recurrent mice xenografts compared to untreated control. CONCLUSION: These findings unravel some of the molecular mechanisms by which chemoresistance and relapse occur in OC patients' post-chemotherapy treatment; and may be important in designing novel therapeutic options for advanced-stage OC patients. Citation Format: Nuzhat Ahmed, Ruth Escalona, Elif Kadife, Dilys Leung and George Kannourakis. CANCER STEM CELLS: DISTINCT SEEDS FOR RECURRENT OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP26.

N-Dihydrogalactochitosan Potentiates the Radiosensitivity of Liver Metastatic Tumor Cells Originated from Murine Breast Tumors.

Radiation is a widely used therapeutic method for treating breast cancer. N-dihydrogalactochitosan (GC), a biocompatible immunostimulant, is known to enhance the effects of various treatment modalities in different tumor types. However, whether GC can enhance the radiosensitivity of cancer cells remains to be explored. In this study, triple-negative murine 4T1 breast cancer cells transduced with multi-reporter genes were implanted in immunocompetent Balb/C mice to track, dissect, and identify liver-metastatic 4T1 cells. These cells expressed cancer stem cell (CSC) -related characteristics, including the ability to form spheroids, the expression of the CD44 marker, and the increase of protein stability. We then ex vivo investigated the potential effect of GC on the radiosensitivity of the liver-metastatic 4T1 breast cancer cells and compared the results to those of parental 4T1 cells subjected to the same treatment. The cells were irradiated with increased doses of X-rays with or without GC treatment. Colony formation assays were then performed to determine the survival fractions and radiosensitivity of these cells. We found that GC preferably increased the radiosensitivity of liver-metastatic 4T1 breast cancer cells rather than that of the parental cells. Additionally, the single-cell DNA electrophoresis assay (SCDEA) and γ-H2AX foci assay were performed to assess the level of double-stranded DNA breaks (DSBs). Compared to the parental cells, DNA damage was significantly increased in liver-metastatic 4T1 cells after they were treated with GC plus radiation. Further studies on apoptosis showed that this combination treatment increased the sub-G1 population of cells, but not caspase-3 cleavage, in liver-metastatic breast cancer cells. Taken together, the current data suggest that the synergistic effects of GC and irradiation might be used to enhance the efficacy of radiotherapy in treating metastatic tumors.

Transcriptomic Analysis of Breast Cancer Stem Cells and Development of a pALDH1A1:mNeptune Reporter System for Live Tracking

Many solid cancers are hierarchically organized with a small number of cancer stem cells (CSCs) able to regrow a tumor, while their progeny lacks this feature. Breast CSC is known to contribute to therapy resistance. The study of those cells is usually based on their cell-surface markers like CD44high /CD24low/neg or their aldehyde dehydrogenase (ALDH) activity. However, these markers cannot be used to track the dynamics of CSC. Here, a transcriptomic analysis is performed to identify segregating gene expression in CSCs and non-CSCs, sorted by Aldefluor assay. It is observed that among ALDH-associated genes, only ALDH1A1 isoform is increased in CSCs. A CSC reporter system is then developed by using a far red-fluorescent protein (mNeptune) under the control of ALDH1A1 promoter. mNeptune-positive cells exhibit higher sphere-forming capacity, tumor formation, and increased resistance to anticancer therapies. These results indicate that the reporter identifies cells with stemness characteristics. Moreover, live tracking of cells in a microfluidic system reveals a higher extravasation potential of CSCs. Live tracking of non-CSCs under irradiation treatment show, for the first time, live reprogramming of non-CSCs into CSCs. Therefore, the reporter will allow for cell tracking to better understand the implication of CSCs in breast cancer development and recurrence.

Abstract 4681: Functional correlation between cancer stem cells and algorithmic effectiveness of targeted drugs of RAS and PI3K pathways in TNBC

Abstract Background: Cancer stem cells (CSCs) are important for the initiation, metastasis, relapse, and chemo/radio-resistance of several tumors including BC (Polyak K et al., 2008, 2010). We reported a method to study a relationship between the characteristic pattern of CSCs (CD24L/CD44H/CD44v6) expression and the mutational status in PTEN-null MDA-MB468, HCC70; RAS/RAF mutated MDA-MB231; BRCA mutated/PTEN-null SUM149 &amp; HCC1937; PIK3CA mutated BT20 TNBC cells. We also tested CD44/CD24 expression in the context of rational combinations of the PI3K-pathway inhibitors in subtype-specific BC (Carlson et al, AACR, 2016; SABCS 2016). Recently, we studied the role of genetic background in determining the effectiveness of the RAS and PI3K pathway(s) targeted drugs in TNBC by testing a combination of the MEK1/2 inhibitor with mTOR kinase inhibitor or AKT inhibitors (Carlson et al SABCS 2018 P2-03-11). Hypothesis: This study was undertaken to identify the relationship between CSCs and effectiveness of RAS and PI3K pathway(s) targeted drugs in TNBC by testing a combination of the MEK1/2 inhibitor with mTOR kinase inhibitor or AKT inhibitors or PI3K inhibitors. Methods: TNBC cell lines MDA-MB231, SUM149, MDA-MB468 and BT20 were used for the study. Proliferation (Incucyte) and apoptosis (AnnexinV) were tested following the drug treatment alone or in combination. Clonogenic growth (3D matrigel assay). WB was used to interogate signaling events in the context of proliferation and apoptosis. CSC subpopulations were monitored by flow cytometry following treatment in both 2D and 3D. Results: The response to treatment with pathway targeted inhibitor is a function of the relative proportion of CSC and the mutational status of TNBC tumor cells. TNBC cells with higher numbers of CSC tend to be more resistant to PI3K inhibition. Rational drug combinations blocked proliferative signals and enhanced apoptosis (cleaved caspase3) as demonstrated by WB. Single agent treatments were mostly cytostatic and temporarily decreased proliferation, while a marked increase in AnnexinV was seen in doublet combinations. Cells with a higher CSC population demonstrated lower sensitivity to treatment in both 2D and 3D models and a smaller change in the CSC population was seen following 3D growth. The mechanistic details of the effect of this combination on the CD44H/CD24L stem cell populations are being worked out to delineate the relationship between CSC and drug response in TNBC models, the results of which will be presented in the meeting. Significance: As CSCs are considered one of the targets for obtaining a better therapeutic response (Huang R, Rofstad EK, 2017) additionaly normal as well as neoplastic nonstem cells can spontaneously convert to a stem-like state (Chaffer CL et al., 2011), our study reveals the relationship between the effect of targeted therapy and stem cell population. Citation Format: Jennifer C. Aske, Pradip K. De, Brian Leyland-Jones, Nandini Dey. Functional correlation between cancer stem cells and algorithmic effectiveness of targeted drugs of RAS and PI3K pathways in TNBC [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 4681.

Expression of cancer stem cell markers is prognostic in metastatic gastroesophageal adenocarcinoma

Gastroesophageal adenocarcinoma is a common and highly lethal malignancy. Cancer stem cells (CSCs) have a key role in the development and progression of metastatic disease. While expression of CSC markers CD44, CD133 and aldehyde dehydrogenase 1 (ALDH1) in locoregional gastroesophageal cancer is known to be associated with poorer clinical outcomes, the significance of CSC marker expression in distal metastatic disease is unknown. We investigated the clinicopathological and prognostic associations of the CSC markers, CD44, CD133, and ALDH1, on metastatic deposits from gastroesophageal adenocarcinomas, and evaluated the association of CSC expression with urokinase-type plasminogen activator receptor (uPAR) expression. Of the 36 patients included in the study, 16 (44%) were positive for CD44, 13 (36%) were positive for CD133, and 26 (72%) were positive for ALDH1. CD44 expression was significantly associated with poorer overall survival (OS) in univariate [hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.3-6.9, p=0.008] and multivariate analyses (HR 2.5, 95%CI 1.1-6.2, p=0.04). ALDH1 expression was significantly associated with poorer OS in univariate (HR 2.4, 95% CI 1.01-5.7, p=0.04) analysis but was not significant in multivariate analysis. Both CD44 and ALDH1 expression were significantly associated with uPAR expression. We found no association between CD133 expression and OS. CD44 expression on metastatic disease from gastroesophageal adenocarcinomas is an independent prognostic marker associated with poorer OS. These results expand current evidence to support the role of CSCs as biomarkers in metastatic gastroesophageal cancer.

ALDH1A3-regulated long non-coding RNA NRAD1 is a potential novel target for triple-negative breast tumors and cancer stem cells

To discover novel therapeutic targets for triple-negative breast cancer (TNBC) and cancer stem cells (CSCs), we screened long non-coding RNAs (lncRNAs) most enriched in TNBCs for high expression in CSCs defined by high Aldefluor activity and associated with worse patient outcomes. This led to the identification of non-coding RNA in the aldehyde dehydrogenase 1 A pathway (NRAD1), also known as LINC00284. Targeting NRAD1 in TNBC tumors using antisense oligonucleotides reduced cell survival, tumor growth, and the number of cells with CSC characteristics. Expression of NRAD1 is regulated by an enzyme that causes Aldefluor activity in CSCs, aldehyde dehydrogenase 1A3 (ALDH1A3) and its product retinoic acid. Cellular fractionation revealed that NRAD1 is primarily nuclear localized, which suggested a potential function in gene regulation. This was confirmed by transcriptome profiling and chromatin isolation by RNA purification, followed by sequencing (ChIRP-seq), which demonstrated that NRAD1 has enriched chromatin interactions among the genes it regulates. Gene Ontology enrichment analysis revealed that NRAD1 regulates expression of genes involved in differentiation and catabolic processes. NRAD1 also contributes to gene expression changes induced by ALDH1A3; thereby, the induction of NRAD1 is a novel mechanism through which ALDH1A3 regulates gene expression. Together, these data identify lncRNA NRAD1 as a downstream effector of ALDH1A3, and a target for TNBCs and CSCs, with functions in cell survival and regulation of gene expression.

Lactate Promotes Cancer Stem-like Property of Oral Sequamous Cell Carcinoma.

Accumulation of lactate in tumor has been linked to poor prognosis of oral squamous cell carcinoma (OSCC), but the underlying mechanism remained largely uncertain. Previous studies have suggested that presence of cancer stem cells (CSCs) closely correlated with cellular malignancy of OSCC. Here, using 3D organoid culture model, we investigated whether lactate promoted CSCs phenotype in primary OSCC cells. We generated organoids using fresh OSCC specimens and verified that organoids recapitulated histopathology and cellular heterogeneity of parental tumor. Organoids were then transfected with a Wnt reporter to visualize Wnt activity. The sphere forming assay demonstrated that high Wnt activity functionally designated CSCs population in OSCC cells. Further investigations indicated that lactate treatment promoted Wnt activity and increased the expression of CSCs (i.e. CD133+ cells) in organoids. Moreover, silencing monocarboxylate transporter 1 (MCT1), the prominent path for lactate uptake in human tumor with siRNA significantly impaired organoid forming capacity of OSCC cells. Together, our study demonstrated that lactate can promote CSCs phenotype of OSCC, and MCT1 may be a therapeutic target against OSCC growth.

Distinct biological characterization of the CD44 and CD90 phenotypes of cancer stem cells in gastric cancer cell lines.

Recent study implicates that gastric cancer stem cells (CSCs) are capable of generating multiple types of cells to promote tumor growth and heterogeneity important for the development of gastric cancer. However, knowledge is limited regarding the expression and characteristics of marker-positive gastric CSCs. Therefore, gastric CSCs from a series of human gastric cancer cell lines (SNU-5, SNU-16, BGC-823, PAMC-82, MKN-45, and NCI-N87) using four putative CSC surface markers (CD44, CD90, CD133, and epithelial-cell adhesion molecule) were investigated the underlying mechanisms regulating such subpopulations. Only SNU-5 and SNU-16 exhibited independent co-expression of CD44+ and CD90+, which exhibited spheroid-colony formation in vitro and tumor formation in immunodeficient mice. Functional studies revealed that CD44+ cells were more invasive compared with CD90+ cells, whereas CD90+ cells exhibited higher levels of proliferation than CD44+ cells. Furthermore, serial xenotransplantation in mice of CD44+/CD90+ cells derived from SNU-5 and SNU-16 revealed rapid growth of CD90+ cells in subcutaneous lesions and a high metastatic capacity of CD44+ cells in the lung. Mechanistic analyses revealed that CD44+ cells underwent epithelial-to-mesenchymal transition (EMT) following acquisition of mesenchymal features, whereas CD90+ cells enhanced the activation of retinoblastoma phosphorylation at Ser780 and oncogenic cell cycle regulators. The expression of CD44 and CD90 in gastric cancer tissues was associated with distant metastasis and the differentiation state of tumors. These results demonstrated that CD44 and CD90 are specific biomarkers capable of identifying and isolating metastatic and tumorigenic CSCs through their ability to regulate EMT and the cell cycle in gastric cancer cell lines.

SERPINB2 Is a Novel Indicator of Cancer Stem Cell Tumorigenicity in Multiple Cancer Types.

Drug resistance is one of the major characteristics of cancer stem cells (CSCs) and a mechanism of tumor recurrence. Therefore, selectively targeting CSCs may be an effective therapeutic strategy to overcome cancer recurrence. In the present study, we found that exposure to tumorigenic compounds significantly increased the growth potential and stem-cell-like properties of various CSCs. Early-response genes involved in tumorigenesis can be used as specific markers to predict potential tumorigenicity. Importantly, for the first time we identified, a labile tumorigenic response gene—SERPINB2—and showed that tumorigenic compound exposure more profoundly affected its expression in CSCs than in non-stem cancer cells, although both cells exhibit basal expression of SERPINB2 in multiple cancer types. Our data also revealed a strong relationship between the significantly enhanced expression of SERPINB2 and metastatic progression in multiple cancer types. To the best of our knowledge, this is the first study to focus on the functions of SERPINB2 in the tumorigenicity of various CSCs and these findings will facilitate the development of promising tumorigenicity test platforms.

Phenethyl Isothiocyanate Exposure Promotes Oxidative Stress and Suppresses Sp1 Transcription Factor in Cancer Stem Cells.

Aldehyde dehydrogenase 1 (ALDH1) is a cytosolic marker of cancer stem cells (CSCs), which are a sub-population within heterogeneous tumor cells. CSCs associate with therapy-resistance, self-renewal, malignancy, tumor-relapse, and reduced patient-survival window. ALDH1-mediated aldehyde scavenging helps CSCs to survive a higher level of oxidative stress than regular cancer cells. Cruciferous vegetable-derived phenethyl isothiocyanate (PEITC) selectively induces reactive oxygen species (ROS), leading to apoptosis of cancer cells, but not healthy cells. However, this pro-oxidant role of PEITC in CSCs is poorly understood and is investigated here. In a HeLa CSCs model (hCSCs), the sphere-culture and tumorsphere assay showed significantly enriched ALDHhi CSCs from HeLa parental cells (p < 0.05). Aldefluor assay and cell proliferation assay revealed that PEITC treatments resulted in a reduced number of ALDHhi hCSCs in a concentration-dependent manner (p < 0.05). In the ROS assay, PEITC promoted oxidative stress in hCSCs (p ≤ 0.001). Using immunoblotting and flow cytometry techniques, we reported that PEITC suppressed the cancer-associated transcription factor (Sp1) and a downstream multidrug resistance protein (P-glycoprotein) (both, p < 0.05). Furthermore, PEITC-treatment of hCSCs, prior to xenotransplantation in mice, lowered the in vivo tumor-initiating potential of hCSCs. In summary, PEITC treatment suppressed the proliferation of ALDH1 expressing cancer stem cells as well as key factors that are involved with drug-resistance, while promoting oxidative stress and apoptosis in hCSCs.