Proportion Of Cancer Stem Cells Research Articles

Anti-cell growth and anti-cancer stem cell activities of the non-canonical hedgehog inhibitor GANT61 in triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) exhibits biologically aggressive behavior and has a poor prognosis. Novel molecular targeting agents are needed to control TNBC. Recent studies revealed that the non-canonical hedgehog (Hh) signaling pathway plays important roles in the regulation of cancer stem cells (CSCs) in breast cancer. Therefore, the anti-cell growth and anti-CSC effects of the non-canonical Hh inhibitor GANT61 were investigated in TNBC cells. The effects of GANT61 on cell growth, cell cycle progression, apoptosis, and the proportion of CSCs were investigated in three TNBC cell lines. Four ER-positive breast cancer cell lines were also used for comparisons. The expression levels of effector molecules in the Hh pathway: glioma-associated oncogene (GLI) 1 and GLI2, were measured. The combined effects of GANT61 and paclitaxel on anti-cell growth and anti-CSC activities were also investigated. Basal expression levels of GLI1 and GLI2 were significantly higher in TNBC cells than in ER-positive breast cancer cells. GANT61 dose-dependently decreased cell growth in association with G1-S cell cycle retardation and increased apoptosis. GANT61 significantly decreased the CSC proportion in all TNBC cell lines. Paclitaxel decreased cell growth, but not the CSC proportion. Combined treatments of GANT61 and paclitaxel more than additively enhanced anti-cell growth and/or anti-CSC activities. The non-canonical Hh inhibitor GANT61 decreased not only cell growth, but also the CSC population in TNBC cells. GANT61 enhanced the anti-cell growth activity of paclitaxel in these cells. These results suggest for the first time that GANT61 has potential as a therapeutic agent in the treatment of patients with TNBC.

Bile acid: a potential inducer of colon cancer stem cells.

BackgroundAlthough the unconjugated secondary bile acids, specifically deoxycholic acid (DCA) and lithocholic acid (LCA), are considered to be risk factors for colorectal cancer, the precise mechanism(s) by which they regulate carcinogenesis is poorly understood. We hypothesize that the cytotoxic bile acids may promote stemness in colonic epithelial cells leading to generation of cancer stem cells (CSCs) that play a role in the development and progression of colon cancer.MethodsNormal human colonic epithelial cells (HCoEpiC) were used to study bile acid DCA/LCA-mediated induction of CSCs. The expression of CSC markers was measured by real-time qPCR. Flow cytometry was used to isolate CSCs. T-cell factor/lymphoid-enhancing factor (TCF/LEF) luciferase assay was employed to examine the transcriptional activity of β-catenin. Downregulation of muscarinic 3 receptor (M3R) was achieved through transfection of corresponding siRNA.ResultsWe found DCA/LCA to induce CSCs in normal human colonic epithelial cells, as evidenced by the increased proportion of CSCs, elevated levels of several CSC markers, as well as a number of epithelial–mesenchymal transition markers together with increased colonosphere formation, drug exclusion, ABCB1 and ABCG2 expression, and induction of M3R, p-EGFR, matrix metallopeptidases, and c-Myc. Inhibition of M3R signaling greatly suppressed DCA/LCA induction of the CSC marker ALDHA1 and also c-Myc mRNA expression as well as transcriptional activation of TCF/LEF.ConclusionsOur results suggest that bile acids, specifically DCA and LCA, induce cancer stemness in colonic epithelial cells by modulating M3R and Wnt/β-catenin signaling and thus could be considered promoters of colon cancer.

A novel double-targeted nondrug delivery system for targeting cancer stem cells.

Instead of killing cancer stem cells (CSCs), the conventional chemotherapy used for cancer treatment promotes the enrichment of CSCs, which are responsible for tumor growth, metastasis, and recurrence. However, most therapeutic agents are only able to kill a small proportion of CSCs by targeting one or two cell surface markers or dysregulated CSC pathways, which are usually shared with normal stem cells (NSCs). In this study, we developed a novel nondrug delivery system for the dual targeting of CSCs by conjugating hyaluronic acid (HA) and grafting the doublecortin-like kinase 1 (DCLK1) monoclonal antibody to the surface of poly(ethylene glycol) (PEG)–poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (NPs), which can specifically target CD44 receptors and the DCLK1 surface marker – the latter was shown to possess the capacity to distinguish between CSCSs and NSCs. The size and morphology of these NPs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). This was followed by studies of NP encapsulation efficiency and in vitro drug release properties. Then, the cytotoxicity of the NPs was tested via Cell Counting Kit-8 assay. Finally, the 4T1 CSCs were obtained from the alginate-based platform, which we developed as an in vitro tumor model. Tumor-bearing nude mice were used as in vivo models to systematically detect the ability of NPs to target CSCs. Our results showed that the DCLK1–HA–PEG–PLGA NPs exhibited a targeting effect toward CSCs both in vitro and in vivo. These findings have important implications for the rational design of drug delivery systems that target CSCs with high efficacy.

E-CADHERIN EXPRESSION DOWNREGULATION ELEVATES TUMOROGENIC POTENTIAL OF HUMAN COLON CANCER CELL LINE HCT116 VIA INCREASE IN CANCER STEM CELLS AMOUNT

Introduction. E-cadherin aberrant expression or complete loss is common for a number of human malignant neoplasms, and can be a launching mechanism of an epithelial-mesenchymal transition. Passing through epithelial-mesenchymal transition could in turn promote to the acquisition of so called cancer stem cell phenotype by the transformed cells. The objective of the present study is to reveal the influence of E-cadherin expression level on the amount of cancer stem cells in human colon cancer cell line HCT116. Materials and methods. We have created cell sublines with E-cadherin up- and downregulation and assessed the percentage of cancer stem cells using tumor formation assay, clonogenic assay; we also evaluated profile of cell pluripotency markers. Results and conclusion. We have shown that the proportion of cancer stem cells in human colon adenocarcinoma cell line HCT116 depends on the E-cadherin expression level. E-cadherin expression downregulation results in elevated expression of pluripotency genes and in the increase of proportion of cancer stem cells via activation of Wnt/ß-signalling pathway. E-cadherin upregulation has a reverse effect and decreases the amount of HCT116 cancer stem cells. Thus, E-cadherin expression restoration seems prospective in colorectal anticancer therapy.

Multi-cycle chemotherapy with the glycolipid-like polymeric micelles evade cancer stem cell enrichment in breast cancer therapy

Multi-cycle chemotherapy is commonly used in the clinic, while the phenomena of enrichment of cancer stem cells (CSCs) and enhanced multi-drug resistance (MDR) are commonly involved. This research was designed for evaluating this successive administration. Chitosan oligosaccharide-g-stearic acid (CSOSA) polymer was used as the drug delivery system (DDS) to perform tri-cycle chemotherapy on a new tumor model induced by mammosphere cells. In vitro, on CSCs enriched mammospheres model, the doxorubicin-loaded CSOSA (CSOSA/DOX) displayed an improved growth inhibition effect measured by acid phosphatase assay (APH). While in vivo, the CSOSA/DOX micelles blocked tumor progression and led to a marked decrease of CSCs proportion as well as MDR capacity. What's more, the CSOSA/DOX helped decay the microenvironment and attenuate systemic side effects. We concluded that the CSOSA polymer could be a potential DDS for long-term multi-cycle chemotherapy in antitumor research.

Prognostic Value of a BCSC-associated MicroRNA Signature in Hormone Receptor-Positive HER2-Negative Breast Cancer

PurposeBreast cancer patients with high proportion of cancer stem cells (BCSCs) have unfavorable clinical outcomes. MicroRNAs (miRNAs) regulate key features of BCSCs. We hypothesized that a biology-driven model based on BCSC-associated miRNAs could predict prognosis for the most common subtype, hormone receptor (HR)-positive, HER2-negative breast cancer patients. Patients and MethodsAfter screening candidate miRNAs based on literature review and a pilot study, we built a miRNA-based classifier using LASSO Cox regression method in the training group (n=202) and validated its prognostic accuracy in an internal (n=101) and two external validation groups (n=308). ResultsIn this multicenter study, a 10-miRNA classifier incorporating miR-21, miR-30c, miR-181a, miR-181c, miR-125b, miR-7, miR-200a, miR-135b, miR-22 and miR-200c was developed to predict distant relapse free survival (DRFS). With this classifier, HR+HER2− patients were scored and classified into high-risk and low-risk disease recurrence, which was significantly associated with 5-year DRFS of the patients. Moreover, this classifier outperformed traditional clinicopathological risk factors, IHC4 scoring and 21-gene Recurrence Score (RS). The patients with high-risk recurrence determined by this classifier benefit more from chemotherapy. ConclusionsOur 10-miRNA-based classifier provides a reliable prognostic model for disease recurrence in HR+HER2− breast cancer patients. This model may facilitate personalized therapy-decision making for HR+HER2− individuals.

Abstract LB-139: Prognostic value of a BCSC-associated microRNA signature in hormone receptor-positive her2-negative breast cancer

Abstract Background: Breast cancer patients with high proportion of cancer stem cells (BCSCs) are more chemotherapy-resistant and have unfavorable clinical outcomes. MicroRNAs (miRNAs) can function as oncogenes or tumor suppressor genes, which regulate key features of BCSCs. Since BCSCs have unique miRNA expression profile, we hypothesized that a biology-driven model based on BCSC-associated miRNAs could provide prognostic information for low recurrent-risk HR+HER2- breast cancer patients. Methods: A systematic literature reviewing suggested 50 BCSC-associated miRNAs that regulate the BCSC features. We excluded 15 of these miRNAs as they were not constantly detectable in the 40 paraffin embedded tumor samples by qRT-PCR (A pilot assay). A total of 35 BCSC-associated miRNAs were identified. We randomly assigned 303 patients into a training group (n = 202) and an internal validation (n = 101) group. We built a 10-miRNA-based classifier using a LASSO Cox model in the training group and validated its prognostic in the internal validation group, and two external independent groups of 308 patients. Results: In this multicenter study, we developed build a 10-miRNA classifier to predict disease-relapse free survival (DRFS). With this classifier, HR+HER2- breast cancer patients were classified into high-risk and low-risk group of diseases recurrence. The DFS was significantly different between these two groups in all of the patient groups. In the training group, the 5-year DRFS was 90.83% and 35.0% for the low-risk and the high-risk group, respectively (hazard ratio [HR] 15.85, 95% CI 8.15-30.82; p<0•0001). In the internal validation group, the 5-year DRFS was 91.95% and 7.14% for the low-risk and the high-risk group, respectively (HR 20.62, 95% CI 8.31-51.20; p<0•0001). Furthermore, in the 1st external validation group, the 5-year DRFS for low-risk group and high-risk group were 87.50% and 37.50%, respectively (HR 6.623, 95% CI 3.54-12.39; p<0•0001). In the 2nd external validation group, it was 91.74% for the low-risk group and 57.14% for the high-risk group (HR 6.99, 3.12-15.64; p<0•0001). Moreover, the 10-miRNA-based classifier outperformed the traditional clinicopathological risk factors and IHC4 scoring in predicting the 5-year DRFS. In addition, the patients in the high-risk group were associated with a more favorable response to chemotherapy than the low-risk group (HR 1.806, 95% CI 1.10-2.98; p = 0.0278). Interpretation: Our 10-miRNA-based classifier provides a reliable prognostic model for disease recurrence in HR+HER2- breast cancer patients. This classifier may facilitate patient counseling and serve in personalized treatment for breast cancer patients. Citation Format: Chang Gong, Weige Tan, Kai Chen, Na You, Shan Zhu, Wei Luo, Xinhua Xie, Yunjie Zeng, Nengtai Ouyang, Zhihua Li, Mushen Zeng, ShiMei Zhuang, Wan-Yee Lau, Qiang Liu, Fengxi Su, Xueqin Wang, Erwei Song. Prognostic value of a BCSC-associated microRNA signature in hormone receptor-positive her2-negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-139.

Abstract 1555: MDSC mediated spatiotemporal tumor plasticity in breast cancer metastasis

Abstract Metastatic breast cancer is the second leading cause of cancer-related death among women. Although the genetic and epigenetic differences between the metastatic versus non-metastatic breast tumors have been well studied, early events between tumor and immune system in metastatic process remain poorly understood. In order to determine early events, we utilized murine mammary tumors (4T1 as metastatic, EMT6 or 67NR as non-metastatic) in syngeneic mouse model. The 4T1 tumor contained a higher proportion of cancer stem cell (CSC) population compared to the non-metastatic EMT6 or 67NR clones. Although, both murine tumor cell lines (50K each) grow to same size tumors within 8 weeks, 4T1 tumors develop spontaneous metastasis in 100% of animals most of which do not survive more than 8 weeks due to extensive wide spread metastasis to lung, liver and bone. We observed immune infiltrates in the lungs of 4T1 tumor bearing mice as early as 1 week. We next assessed the cytokine profile of metastatic 4T1 tumor compared to non-metastatic counterparts (EMT6 or 67NR) secretes significantly higher levels of inflammatory cytokines, including the IL6, IL8, RANTES, GCSF, GM-CSF, IL12, CXCL16 and CXCL5. MDSCs are potent suppressor of anti-tumor immunity and a significant impediment to cancer therapy. We therefore hypothesized that the tumor secreted inflammatory cytokines promotes the systemic expansion of MDSCs that down regulate immune surveillance and anti-tumor immunity, thus facilitating tumor progression. We sought to determine whether 4T1 tumors could induce MDSCs in mice. Murine 4T1 or EMT6 tumor cells (at 50K cells each) were implanted into the fat pads of BALB/c mice, then sacrificed (4 mice from each group) at weeks 1, 2, 3 and 4 for subsequent evaluation of the MDSC expansion in bone marrow, spleen, lung and tumors. The MDSC induction and infiltration in bone marrow, spleen, lung and tumors were observed as early as one-week post-implantation of 4T1 tumor compared to the EMT6. Furthermore, the MDSCs isolated from 4T1 tumor bearing animals were more suppressive than that of the EMT6 tumor bearing mice. We determined that non-metastatic EMT6-Luciferase tumor growth and metastasis is robustly enhanced in pre-primed animals (in which metastatic 4T1 cells were pre-implanted in the fat pads and resected after 10 days when tumors were 2mm in size) or by IP injection of inflammatory cytokine rich 4T1 conditioned medium when compared to injection of EMT6-Luci cells into naïve animals. Our preliminary findings suggested that 4T1 tumors within 10 days of implantation created a systemic tumor-promoting microenvironment and thus promoted the metastatic spread of EMT6-Luci. Together these studies strongly suggest that metastatic 4T1 tumor with high CSC phenotype generate a permissive systemic microenvironment for successful metastasis via secretion of inflammatory cytokines in syngeneic BALB/c mice. Citation Format: Hasan Korkaya, Eunmi Lee, Maria Ouzounova, Raziye Piranlioglu, Abdeljabar El-Andaloussi, Ena Novakovic, Alicia Hudson, Sumeyye Korkaya, Mhmet F. Demirci, Gang Zhou. MDSC mediated spatiotemporal tumor plasticity in breast cancer metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1555.

Abstract 1624: Silencing of ERK2 reverses EMT and suppresses the CSC phenotype, inhibiting lung metastasis in triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is an aggressive subtype lacking estrogen receptor, progesterone receptor, and HER2 overexpression. Patients with TNBC have a generally poor prognosis due to metastasis, high rates of recurrence, and lack of FDA-approved targeted therapies. We previously showed using functional proteomics that patients with high-ERK2-expressing TNBC tumors had a higher risk of death than those with low-ERK2-expressing tumors. Moreover, ERK2 but not ERK1 plays an important role in epithelial-mesenchymal transition (EMT) and is required for acquisition of stem cell-like characteristics. Compared to other breast cancer subtypes, TNBC has a higher proportion of cancer stem cells (CSCs) and is linked to EMT, two critical features associated with breast cancer progression, metastasis, and recurrence in patients. The MAPK signaling pathway is activated in TNBC, but the roles of ERK isoforms in tumor progression and metastasis are not well defined. We hypothesized that ERK2 but not ERK1 promotes EMT, the CSC phenotype, and metastasis in TNBC. Methods and Results: Knockdown of ERK2 in SUM149 and BT549 TNBC cells significantly inhibited anchorage-independent colony formation (p<0.0001), inhibited formation of mammospheres (p = 0.003), and reduced the CSC population (CD44+/CD24-) (p = 0.002) in vitro. This effect correlated with a reduction in migration (p = 0.0004) and invasion (p<0.0001). SCID-beige mice injected via the tail vein with SUM149 shERK2 cells had a significantly lower lung metastatic burden than control mice (p = 0.0034) or mice injected with shERK1 cells (p = 0.0012), suggesting that ERK2 is a mediator of metastatic burden. To determine the mechanism by which ERK2 mediates this phenotype, we performed an Affymetrix Human Genome U133 Plus 2.0 array and compared the gene expression levels between SUM149 cells with ERK2 or ERK1 knockdown or transfection with control shRNA. Analysis of microarray data revealed that global gene expression changes associated with ERK2 knockdown predominantly altered regulation of the EMT pathway. Among the genes with ERK2-knockdown-associated expression change was EGR1, an immediate early response transcription factor whose downstream targets affect cell growth and differentiation. EGR1 is down-regulated 6-fold (p = 0.00013) compared to control and shERK1 cells. Knockdown of ERK2, but not ERK1, resulted in significantly lower EGR1 at both the mRNA and protein levels, validating our microarray data. Conclusions and Future Directions: Our findings support our hypothesis, indicating that ERK2 promotes EMT and the CSC phenotype through EGR1 and mediates metastasis in TNBC. Future studies will determine ERK activity and pathway engagement using a novel peptide sensor based on the Sox fluorophore. We will pursue a therapeutic approach using siRNA against ERK2 incorporated in a DOTAP:cholesterol liposome. Citation Format: Mary Kathryn Pitner, Hitomi Saso, Richard Larson, Rachel M. Sammons, Huiqin Chen, Caimiao Wei, Gaurav Chauhan, Kimie Kondo, Naoto T. Ueno, Kevin Dalby, Bisrat G. Debeb, Chandra Bartholomeusz. Silencing of ERK2 reverses EMT and suppresses the CSC phenotype, inhibiting lung metastasis in triple-negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1624.

Abstract 3734: Preclinical evaluation of Rad6 inhibition to overcome platinum resistance in ovarian cancer

Abstract Ovarian cancer (OC) is the most lethal gynecological cancer in women in the United States. Advances in surgery and chemotherapy have not significantly changed the overall survival rate of OC for the last few decades, which highlights the need for new therapeutic strategies. Platinum drug resistance and refractory disease pose major challenges in treating this disease and are major factors contributing to the poor survival rate of OC patients. Although most patients initially respond to platinum based chemotherapy, about 80% of cases present with recurrent disease, develop platinum resistance, and die with the advanced disease. Considering the heterogeneity, small fractions of the cells could be inherently resistant to chemotherapy and/or dormant and exhibit stem-like cell properties, contributing to the resistant phenotype and disease recurrence. Although the Cancer stem cell (CSC) theory of therapeutic resistance proposes that the proportion of CSCs correlate to enhanced chemoresistance and early disease recurrence, the specific molecular mechanisms that regulate tumor cell behavior (stemness) and integrate signaling networks with aberrant oncogenic signaling in OC cells are not known. Our analysis of clinical samples revealed upregulation of Rad6, an E2 ubiquitin conjugating enzyme, in more than 80% of ovarian tumors compared to normal ovarian tissues. Upregulation of Rad6 also correlated well with tumor progression. Further analysis of molecular pathways in OC cells revealed a strong correlation between Rad6 upregulation and increased β-catenin and hedgehog signaling, stem cell like characteristics and platinum resistance. Downregulation of Rad6 using siRNAs or inhibition of its catalytic activity by a small molecule inhibitor, attenuated carboplatin induced monoubiquitination of its target proteins such as histone 2B, PCNA and proteins of the Fanconi anemia pathway thereby sensitizing OC cells to carboplatin. Interestingly, inhibition of Rad6 alone in OC cells induced replication stress and reduced cell survival and proliferation by arresting cells in the G2/M phase. Moreover, inhibition of Rad6 in various OC cell lines reduced expression of β-catenin, Gli1 and several OC stem cell markers. Moreover, Rad6 plays an important role in the activation of the trans-lesion synthesis (TLS) pathway by monoubiquitinating PCNA and in the activation of the Fanconi Anemia (FA) DNA repair pathway. These are critical mechanisms for cells to repair DNA crosslinks induced by platinum drugs. Together with these observations, our data suggest that inhibition of Rad6 could be a viable therapeutic target for overcoming platinum resistance and disease recurrence in ovarian cancer. Citation Format: Sebastian M. Spencer, Ranganatha R. Somasagara, Kaushlendra Tripathi, David W. Clark, Hend Kothayer, Andrew D. Westwell, Rodney P. Rocconi, Komaraiah Palle. Preclinical evaluation of Rad6 inhibition to overcome platinum resistance in ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3734.

Abstract 2705: A computational algorithm to predict tumor growth and cancer stem cell proportion in-vitro and in-vivo from single-cell observations

Abstract We have developed a new mathematical algorithm and corresponding computer software that uses observations of single cell behavior to predict the growth of the cancer stem-like cell proportion in larger cancer cell groups. Cancer stem-like cells (CSCs) have been implicated in ovarian cancer tumor growth, chemotherapy resistance, and disease recurrence. Aldehyde dehydrogenase (ALDH) is a primary discriminator of CSCs in ovarian cancer as well as in other cancer types. Unfortunately, the rarity and ability of CSCs to rapidly differentiate makes them difficult to study in-vitro and in-vivo. Microfluidic capture devices now allow us to grow and evaluate single ovarian cancer cells in isolated culture. We deployed microfluidic devices to evaluate the different self-renewal and asymmetric division patterns of ALDH+ and ALDH(-) ovarian CSCs. We analyzed data gathered from arrays of single cell chamber observations and found that purified ALDH+ cells were more proliferative than ALDH(-) cells in both cell-line (n = 112, p < 0.001) and primary (n = 41, p = 0.008) ovarian cancer specimens. Importantly, ALDH+ cells could produce both ALDH+ and ALDH(-) cells, whereas ALDH- cells were only able to produce ALDH- cells. Based on this hierarchy-defining data, we developed an easy to use computer algorithm on the freely-available software R to predict cancer cell population growth in-vitro and in-vivo. In our algorithm, size changes of cell populations are simulated by drawing from observed events. We compared the predictions from our hybrid microfluidics chip and computational algorithm with validation experiments in-vivo and in-vitro for both cell line and primary ovarian cancer cells. We found a superb correlation between observed and predicted in-vitro total and CSC counts for both cell line and primary ovarian cancer cells (correlation r = 0.98, p < 0.0001). Furthermore, this approach appropriately predicted changes in cell growth in the presence of the CSC-promoting growth factor EGFL6 both in vitro and in vivo, over time frames of up to 28 days. The single cell division based sampling algorithm developed here allows for rapid and inexpensive means to predict in-vivo ovarian tumor growth based on microfluidic chip culture and can easily be adapted to evaluate new therapeutic options across other cancer subtypes. Citation Format: Alexander T. Pearson, Patrick Ingram, Shoumei Bai, Euisik Yoon, Trachette Jackson, Ronald J. Buckanovich. A computational algorithm to predict tumor growth and cancer stem cell proportion in-vitro and in-vivo from single-cell observations. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2705.

Immunohistochemical expression of stem cell markers CD44 and nestin in glioblastomas: Evaluation of their prognostic significance

Glioblastoma (GB) is a highly aggressive brain tumor with dismal prognosis and its standard of care consists of surgery followed by radiotherapy plus adjuvant chemotherapy with temozolomide (Stupp protocol). The response to therapy is variable and may be affected by the presence, within the tumor, of a proportion of cancer stem cells, implicated in chemo- and radioresistance. The expression of the stem cell markers nestin and CD44 in GBs has been extensively investigated.The aim of our study was to compare the immunohistochemical expression of nestin and CD44 in 25 cases of GBs and evaluate their possible prognostic value in relation to overall survival time.We found that their expression was strongly correlated (p=0.0090e r=0.5320) and this finding was confirmed by observation with double staining techniques. For the first time, we made a separate immunohistochemical examination of membrane and cytoplasmic nestin staining, finding that although the two signals correlated (p=0.0184, r=0.4678), they had different impact on survival (respectively p=0.0255 and p=0.6376). Enhanced CD44 expression was associated with poor survival rates even if this finding was not statistically significant (p=0.4481, ĸ2=0.5755).Overall, membrane nestin signal was found to be a valid prognostic factor. Furthermore, the detection of CD44 in GBs could be of value also as predictive marker; hyaluronan-based nanoparticles have already shown an active targeting of this antigen in other tumors.

Prognostic value of a BCSC-associated microRNA signature in hormone receptor-positive HER2-negative breast cancer.

532Background: Breast cancer patients with high proportion of cancer stem cells (BCSCs) are more chemotherapy-resistant and have unfavorable clinical outcomes. MicroRNAs (miRNAs) can function as on...

Salinomycin Hydroxamic Acids: Synthesis, Structure, and Biological Activity of Polyether Ionophore Hybrids

The polyether ionophore salinomycin has recently gained attention due to its exceptional ability to selectively reduce the proportion of cancer stem cells within a number of cancer cell lines. Efficient single step strategies for the preparation of hydroxamic acid hybrids of this compound varying in N- and O-alkylation are presented. The parent hydroxamic acid, salinomycin-NHOH, forms both inclusion complexes and well-defined electroneutral complexes with potassium and sodium cations via 1,3-coordination by the hydroxamic acid moiety to the metal ion. A crystal structure of an cationic sodium complex with a noncoordinating anion corroborates this finding and, moreover, reveals a novel type of hydrogen bond network that stabilizes the head-to-tail conformation that encapsulates the cation analogously to the native structure. The hydroxamic acid derivatives display down to single digit micromolar activity against cancer cells but unlike salinomycin selective reduction of ALDH(+) cells, a phenotype associated with cancer stem cells was not observed. Mechanistic implications are discussed.

Promoting tumor penetration of nanoparticles for cancer stem cell therapy by TGF-β signaling pathway inhibition

Cancer stem cells (CSCs), which hold a high capacity for self-renewal, play a central role in the development, metastasis, and recurrence of various malignancies. CSCs must be eradicated to cure instances of cancer; however, because they can reside far from tumor vessels, they are not easily targeted by drug agents carried by nanoparticle-based drug delivery systems. We herein demonstrate that promoting tumor penetration of nanoparticles by transforming growth factor β (TGF-β) signaling pathway inhibition facilitates CSC therapy. In our study, we observed that although nanoparticles carrying siRNA targeting the oncogene polo-like kinase 1 (Plk1) efficiently killed breast CSCs derived from MDA-MB-231 cells in vitro, this intervention enriched CSCs in the residual tumor tissue following systemic treatment. However, inhibition of the TGF-β signaling pathway with LY364947, an inhibitor of TGF-β type I receptor, promoted the penetration of nanoparticles in tumor tissue, significantly ameliorating the intratumoral distribution of nanoparticles in MDA-MB-231 xenografts and further leading to enhanced internalization of nanoparticles by CSCs. As a result, synergistic treatment with a nanoparticle drug delivery system and LY364947 inhibited tumor growth and reduced the proportion of CSCs in vivo. This study suggests that enhanced tumor penetration of drug-carrying nanoparticles can enhance CSCs clearance in vivo and consequently provide superior anti-tumor effects.

Curcumin Suppresses Phthalate-Induced Metastasis and the Proportion of Cancer Stem Cell (CSC)-like Cells via the Inhibition of AhR/ERK/SK1 Signaling in Hepatocellular Carcinoma.

Recent evidence indicating that phthalates promote cancer development, including cell proliferation, migration, and invasion, has raised public health concerns. Here, we show that bis(2-ethylhexyl) phthalate promotes the migration, invasion, and epithelial-mesenchymal transition of hepatocellular carcinoma cells. In addition, bis(2-ethylhexyl) phthalate increased the proportion of cancer stem cell (CSC)-like cells and stemness maintenance in vitro as well as tumor growth and metastasis in vivo. The various activities of curcumin, including anticancer, anti-inflammation, antioxidation, and immunomodulation, have been investigated extensively. Curcumin suppressed phthalate-induced cell migration, invasion, and epithelial-mesenchymal transition, decreased the proportion of CSC-like cells in hepatocellular carcinoma cell lines in vitro, and inhibited tumor growth and metastasis in vivo. We also reveal that curcumin suppressed phthalate-induced migration, invasion, and CSC-like cell maintenance through inhibition of the aryl hydrocarbon receptor/ERK/SK1/S1P3 signaling pathway. Our results suggest that curcumin may be a potential antidote for phthalate-induced cancer progression.

Hypoxia and TGF-β1 lead to endostatin resistance by cooperatively increasing cancer stem cells in A549 transplantation tumors.

BackgroundLung cancer is the leading cause of cancer-related deaths worldwide, and treatments for lung cancer have a high failure rate. Anti-angiogenic therapy is also often ineffective because of refractory disease. Endostatin (ES) is one of the most widely-used anti-angiogenic drugs for lung cancer in China, and resistance to it is a barrier that needs to be resolved. It has been shown that myeloid-derived suppressor cells (MDSCs) are involved in resistance to ES. Whether other cells and/or cell factors in the tumor microenvironment that have been shown to be related to resistance to other anti-cancer drugs are also involved in ES resistance is unknown.ResultsIn this study, we showed that after continuously treatment with ES for 12 days, volumes of A549 transplantation tumors of mice reached the sizes of tumors which were borne by mice that were treated with normal saline and this meant that resistance to ES appeared. Cancer stem cells (CSCs), which have been widely accepted as one of reasons responsible for resistance to many anti-tumor drugs were also being discovered increased proportionally in A549 transplantation tumors after ES treatment for 12 days. During further exploration of reasons for this increase, we discovered that after ES treatment, microvessel density and vascular endothelial growth factor level was decreased in tumors, whereas transforming growth factor (TGF)-β1 level was elevated, and MDSCs, one of the sources of TGF-β1, were also increased. We speculate that hypoxia and TGF-β1 are responsible for the increased CSC number in A549 transplantation tumors. By using cobalt chloride to mimic hypoxia and human recombinant TGF-β1 in vitro, we found that hypoxia and TGF-β1can indeed enhance the stemness of A549 cells. In addition, the inductive effect of hypoxia is stronger than TGF-β1, and the combination of both is stronger than either alone, which is first report of such a finding, to our knowledge.ConclusionsIncreased TGF-β1 and strengthened hypoxia in A549 transplantation tumors, as a result of ES therapy, cooperatively increase proportion of CSCs that are involved in ES resistance which was revealed by failure of tumor volume repression after continuously treatment with ES for 12 days.

Abstract 1397: Identification of a hepatocellular carcinoma cell line capable of monitoring the differentiation of CD13(+)CD166(-) cancer stem cells and effects of sorafenib

Abstract Background: Recent cancer stem cell (CSC) research has highlighted the necessity to develop drugs targeting CSCs. However, only few in vitro models are available which show CSC hierarchy and allow monitoring of CSC differentiation and screening of drugs targeting CSC. Aim: In the present study, we aimed to identify such hepatocellular carcinoma (HCC) cell line(s). Methods: Based on a hypothesis that the proportion of CSCs would decrease during culture because of their differentiation into progenitors (population switch), we tested the positivity of several markers (CD13, EpCAM, CD133, CD44, CD90, CD24, CD166) in HCC cell lines (HuH-7, Li-7, PLC/PRF/5, HLF, HLE) before and after 2 months culture. Results: Only Li-7 cells showed relevant population switch: the proportion of CD13 decreased, while that of CD166 increased during the culture. High tumorigenicity of Li-7 was lost after the population switch. CD13(+)/CD166(-) cells showed slow growth and reconstructed the bulk Li-7 populations composed of CD13(+)/CD166(-), CD13(-)/CD166(-) and CD13(-)/CD166(+) fractions, while CD13(-)/CD166(+) cells showed rapid growth but could not reproduce any other cell populations. CD13(+)/CD166(-) cells showed high ALDH activity, spheroid forming ability and resistance to 5FU. Microarray analysis demonstrated higher expression of stemness-related genes in CD166(-) than CD166(+) fraction. These results indicated the hierarchy of Li-7 cells, in which CD13(+)/CD166(-) and CD13(-)/CD166(+) cells serve as slow growing CSCs and rapid growing progenitors, respectively. Interestingly, sorafenib selectively targeted CD166(-) fraction including CD13(+) CSCs, which exhibited higher mRNA expression of FGF3 and FGF4, candidate biomarkers for sorafenib. 5-FU followed by sorafenib inhibited the growth of bulk Li-7 cells more effectively than reverse sequence or either alone. Conclusions: We identified an useful cell line Li-7 capable of monitoring the CD13 (+) CSC differentiation and screening the drugs targeting the CSCs of HCC and found that sorafenib preferentially targeted CD13(+) CSCs in vitro. Screening cell lines for “population switch” may be useful to identify novel candidate model systems for screening drugs targeting CSCs. Citation Format: Takeshi Yamada, Masato Abei, Inaho Danjoh, Ryoko Shirota, Taro Yamashita, Shinji Endo, Ichinosuke Hyodo, Yukio Nakamura. Identification of a hepatocellular carcinoma cell line capable of monitoring the differentiation of CD13(+)CD166(-) cancer stem cells and effects of sorafenib. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1397. doi:10.1158/1538-7445.AM2015-1397

Abstract 466: Systemic early immune priming via tumor-secreted cytokines facilitates breast cancer metastasis in syngeneic mouse model

Abstract Metastatic breast cancer is the second leading cause of cancer-related death among women in the United States. Although the genetic and epigenetic differences between the metastatic versus non-metastatic breast tumors have been well studied, early events between tumor and immune system in metastatic process remain poorly understood. In order to determine early events, we utilized murine mammary tumors (4T1 as metastatic, EMT6 or 67NR as non-metastatic) in syngeneic mouse model. The 4T1 tumor contained a higher proportion of cancer stem cell (CSC) population compared to the non-metastatic EMT6 or 67NR clones. Although, both murine tumor cell lines (50K each) grow to same size tumors within 8 weeks, 4T1 tumors develop spontaneous metastasis in 100% of animals most of which do not survive more than 8 weeks due to extensive wide spread metastasis to lung, liver and bone. We observed immune infiltrates in the lungs of 4T1 tumor bearing mice as early as 1 week. We next assessed the cytokine profile of metastatic 4T1 tumor compared to non-metastatic counterparts (EMT6 or 67NR) secretes significantly higher levels of inflammatory cytokines, including the IL6, IL8, RANTES, GCSF, GM-CSF, IL12, CXCL16 and CXCL5. MDSCs are potent suppressor of anti-tumor immunity and a significant impediment to cancer therapy. We therefore hypothesized that the tumor secreted inflammatory cytokines promotes the systemic expansion of MDSCs that down regulate immune surveillance and anti-tumor immunity, thus facilitating tumor progression. We sought to determine whether 4T1 tumors could induce MDSCs in mice. Murine 4T1 or EMT6 tumor cells (at 50K cells each) were implanted into the fat pads of BALB/c mice, then sacrificed (4 mice from each group) at weeks 1, 2, 3 and 4 for subsequent evaluation of the MDSC expansion in bone marrow, spleen, lung and tumors. The MDSC induction and infiltration in bone marrow, spleen, lung and tumors were observed as early as one-week post-implantation of 4T1 tumor compared to the EMT6. Furthermore, the MDSCs isolated from 4T1 tumor bearing animals were more suppressive than that of the EMT6 tumor bearing mice. We determined that non-metastatic EMT6-Luciferase tumor growth and metastasis is robustly enhanced in pre-primed animals (in which metastatic 4T1 cells were pre-implanted in the fat pads and resected after 10 days when tumors were 2mm in size) or by IP injection of inflammatory cytokine rich 4T1 conditioned medium when compared to injection of EMT6-Luci cells into naïve animals. Our preliminary findings suggested that 4T1 tumors within 10 days of implantation created a systemic tumor-promoting microenvironment and thus promoted the metastatic spread of EMT6-Luci. Together these studies strongly suggest that metastatic 4T1 tumor with high CSC phenotype generate a permissive systemic microenvironment for successful metastasis via secretion of inflammatory cytokines in syngeneic BALB/c mice. Citation Format: Hasan Korkaya, Eunmi Lee, Maria Ouzounova, Abdeljabar El Andaloussi, Ena Novakovic, Raziye Piranlioglu, Mehmet F. Demirci, Shawn G. Clouthier, Max S. Wicha. Systemic early immune priming via tumor-secreted cytokines facilitates breast cancer metastasis in syngeneic mouse model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 466. doi:10.1158/1538-7445.AM2015-466

Abstract 4236: FAK inhibitor VS-6063 (defactinib) targets mesothelioma cancer stem cells, which are enriched by standard of care chemotherapy

Abstract Malignant pleural mesothelioma (MPM) is an aggressive tumor in the lining of the lung often resulting from prior exposure to asbestos. Median overall survival with standard of care chemotherapy is only 12 months from diagnosis. This poor prognosis may be attributable at least in part to cancer stem cells (CSCs) which are resistant to chemotherapy and can mediate cancer recurrence and progression. Focal adhesion kinase (FAK) has been shown to play an essential role in the survival, self-renewal and tumor-initiating capability of CSCs. Accordingly, the FAK inhibitor VS-6063 is currently being tested in patients with MPM following disease control on standard pemetrexed/platinum chemotherapy (COMMAND, ClinicalTrials.gov NCT01870609). Aldehyde dehydrogenase (ALDH) activity was validated as a CSC marker in MPM by assessment of tumor-initiating capability in mice. As compared to ALDH-negative cells, sorted ALDH-positive MM87 MPM cells showed 35-fold greater tumor initiating capacity when implanted in limiting dilutions into immunodeficient mice. Indeed, 50 ALDH-positive cells were sufficient to generate sizeable tumors in 3 weeks illustrating the aggressive nature of MPM CSCs. Treatment of a human MPM cell line with pemetrexed enriched ALDH-positive CSCs 6-fold, with similar CSC enrichment by cisplatin. In direct contrast, the FAK inhibitor VS-6063 markedly reduced the proportion of CSCs. The enrichment of MPM CSCs was similarly observed in samples from 11 tested patients following first line chemotherapy. Patient specimens post treatment with pemetrexed and cisplatin showed an elevated ALDH immunohistochemistry H-score and an increase in expression of CSC genes such as CD133 as compared to matched MPM biopsies taken from the same patients prior to chemotherapy. To assess drug effects on tumor-initiating capacity, MM87 merlin-low MPM and H28 merlin-high MPM cell lines were treated in vitro with VS-6063, pemetrexed or the combination and subsequently implanted into mice. While control and pemetrexed-treated MPM cells showed robust tumor initiation, cells treated with VS-6063 alone or VS-6063 plus pemetrexed showed little or no tumor initiating capacity. Accordingly, in tumor biopsies from MPM patients treated for 12 days with VS-6063, tumor pFAK (Y397) and expression of CSC genes such as CD133 were reduced. MPM patient-derived xenograft (PDX) tumors were employed to model the clinical scenario. Compared to control, tumor growth was blocked by 2-week treatment with pemetrexed/cisplatin. Tumors then grew rapidly upon cessation of pemetrexed/platinum treatment, whereas tumor growth was substantially delayed by FAK inhibitor treatment after cessation of chemotherapy. These data provide strong rationale for the current clinical testing of VS-6063 following treatment with pemetrexed plus platinum to potentially prolong time to progression in patients with mesothelioma. Citation Format: Jonathan A. Pachter, Vihren N. Kolev, Laurel Schunselaar, Irina M. Shapiro, Raphael Bueno, Paul Baas, Qunli Xu, David T. Weaver. FAK inhibitor VS-6063 (defactinib) targets mesothelioma cancer stem cells, which are enriched by standard of care chemotherapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4236. doi:10.1158/1538-7445.AM2015-4236