Breast Cancer Cancer Stem Cells Research Articles

PH-Triggered Transformable Peptide Nanocarriers Extend Drug Retention for Breast Cancer Combination Therapy.

Increasing the penetration and accumulation of antitumor drugs at the tumor site are crucial in chemotherapy. Smaller drug-loaded nanoparticles (NPs) typically exhibit increased tumor penetration and more effective permeation through the nuclear membrane, whereas larger drug-loaded NPs show extended retention at the tumor site. In addition, cancer stem cells (CSCs) have unlimited proliferative potential and are crucial for the onset, progression, and metastasis of cancer. Therefore, a drug-loaded amphiphilic peptide, DDP- and ATRA-loaded Pep1 (DA/Pep1), is designed that self-assembles into spherical NPs upon the encapsulation of cis-diamminedichloroplatinum (DDP) and all-trans retinoic acid (ATRA). In an acidic environment, DA/Pep1 transforms into aggregates containing sheet-like structures, which significantly increases drug accumulation at the tumor site, thereby increasing antitumor effects and inhibiting metastasis. Moreover, although DDP treatment can increase the number of CSCs present, ATRA can induce the differentiation of CSCs in breast cancer to increase the therapeutic effect of DDP. In conclusion, this peptide nanodelivery system that transforms in response to the acidic tumor microenvironment is an extremely promising nanoplatform that suggests a new idea for the combined treatment of tumors.

Loss of function of GATA3 regulates FRA1 and c-FOS to activate EMT and promote mammary tumorigenesis and metastasis

Basal-like breast cancers (BLBCs) are among the most aggressive cancers, partly due to their enrichment of cancer stem cells (CSCs). Breast CSCs can be generated from luminal-type cancer cells via epithelial-mesenchymal transition (EMT). GATA3 maintains luminal cell fate, and its expression is lost or reduced in BLBCs. However, deletion of Gata3 in mice or cells results in early lethality or proliferative defects. It is unknown how loss-of-function of GATA3 regulates EMT and CSCs in breast cancer. We report here that haploid loss of Gata3 in mice lacking p18Ink4c, a cell cycle inhibitor, up-regulates Fra1, an AP-1 family protein that promotes mesenchymal traits, and downregulates c-Fos, another AP-1 family protein that maintains epithelial fate, leading to activation of EMT and promotion of mammary tumor initiation and metastasis. Depletion of Gata3 in luminal tumor cells similarly regulates Fra1 and c-Fos in activation of EMT. GATA3 binds to FOSL1 (encoding FRA1) and FOS (encoding c-FOS) loci to repress FOSL1 and activate FOS transcription. Deletion of Fra1 or reconstitution of Gata3, but not reconstitution of c-Fos, in Gata3 deficient tumor cells inhibits EMT, preventing tumorigenesis and/or metastasis. In human breast cancers, GATA3 expression is negatively correlated with FRA1 and positively correlated with c-FOS. Low GATA3 and FOS, but high FOSL1, are characteristics of BLBCs. Together, these data provide the first genetic evidence indicating that loss of function of GATA3 in mammary tumor cells activates FOSL1 to promote mesenchymal traits and CSC function, while concurrently repressing FOS to lose epithelial features. We demonstrate that FRA1 is required for the activation of EMT in GATA3 deficient tumorigenesis and metastasis.

A recombinant adenovirus vector containing the synNotch receptor gene for the treatment of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is known as the most difficult molecular subtype of breast cancer to treat. Recent studies revealed that cancer stem cells (CSCs) play a critical role in TNBC recurrence and metastasis. In this study, we developed a recombinant replication-deficient adenoviral vector (Ad-CD44-N-HIF-3α4), which contains a gene encoding a synthetic Notch (synNotch) receptor composed of the extracellular domain of CD44 (CD44-ECD) and the hypoxia-inducible factor (HIF)-3α4 connected by the Notch core regulatory region. CD44 is a transmembrane glycoprotein and known as a CSC marker in breast cancer and other malignancies. HIF-3α4 is a dominant-negative regulator of HIF-1α and HIF-2α and inhibits hypoxia-inducing effect. Both CD44 and HIF signals contribute cancer stemness and maintaining CSCs in breast cancer. The CD44-ECD in the synNotch receptor acts as the CD44 decoy receptor, and after a ligand such as a hyaluronic acid binds to the CD44-ECD, HIF-3α4 is released from the Notch core domain. We performed an in vivo study using a mouse xenograft model of MDA-MB-231, a highly invasive TNBC cell, and confirmed the significant antitumor activity of the intratumoral injections of Ad-CD44-N-HIF3α4. Our findings in this study warrant the further development of Ad-CD44-N-HIF3α4 for the treatment of patients with TNBC.

Abstract 893: GD2 is a potential biomarker for glioblastoma cancer stem cells

Abstract Introduction: Treatment resistance and tumor recurrence of Glioblastoma (GBM) have been associated with cancer stem cells (CSCs), a subpopulation of cancer cells defined by capabilities of sphere-formation in 3D culture, self-renewal, migration, and survival in serum-deprived conditions. Therefore, therapies specifically targeting CSCs are urgently needed. Previous works have identified Ganglioside GD2 as a biomarker of triple negative breast cancer CSCs and suggested that GD2 is highly expressed in GBM cells. Here, we hypothesize that GD2 is also a potential biomarker of GBM CSCs and is involved with cancer stemness. Methods: GBM cells U-87 MG and U-118 MG were sorted as GD2- and GD2+ cells via FACS. Cells were cultured in 2D and 3D. 3D neurosphere size was measured and GD2 in 2D and 3D cultures was quantified via flow cytometry. Transwell migration assay was used to examine the migration capability of GD2- and GD2+ cells. Unsorted cells were cultured in either complete (10% serum) or deprived (1% serum) media and their GD2 was quantified via flow cytometry. Results: To test our hypothesis, we determined whether GD2+ cells express CSCs capabilities of sphere-formation in 3D culture, migration, and survival in serum-deprived conditions. First, we examined the sphere-forming capability by culturing GD2-, GD2+, and unsorted cells in 3D and found that they all formed neurospheres. However, GD2+ neurosphere size was significantly larger compared with unsorted and GD2- neurospheres for day 1 and 2. Interestingly, the significant difference was no longer seen on day 6. Analysis for GD2 expression in the spheres revealed that GD2- spheres contained GD2+ cells, suggesting that GD2- cells could spontaneously dedifferentiate to generate CSCs. To test this, we sorted GD2- and GD2+ cells into 2D conditions and quantified daily GD2 expression via flow cytometry. We found that GD2- seeded cells spontaneously expressed GD2 over six days, explaining the presence of GD2 in GD2- neurospheres. GD2+ cells also demonstrated the enhanced capability to migrate of CSCs with a significantly higher number of migrated cells compared with GD2- cells in the transwell migration assay. To examine the ability to survive in serum-deprived conditions, we cultured unsorted cells in either complete or deprived media. We found that these cells proliferated in the serum-deprived condition at approximately the same level as complete media. GD2 analysis by flow cytometry also showed a remarkably higher percentage of GD2+ cells in deprived media, suggesting that GD2 is involved in driving cell survival and maintaining cancer stemness in serum-deprived conditions. Conclusion: Our data suggests that GD2+ cells demonstrate characteristics of CSCs and GD2 is a potential biomarker of CSCs in GBM. Therefore, GD2 could be utilized as a differential therapeutic target for GBM. Further mechanistic studies are necessary to elucidate how GD2 is synthesized and maintains the stemness of GBM CSCs. Citation Format: Khoa Nguyen, Minh Tran, Thomas Cheng, Kurtis Willingham, Reza Izadpanah, Matthew Burow. GD2 is a potential biomarker for glioblastoma cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 893.

Assessment of Breast Cancer Stem Cell Activity Using a Spheroid Formation Assay.

Evidence is emerging that cancer cells are arranged as a hierarchy that spans from stem cells to lineage-restricted progenitor cells. The recent development of spheroid cultures with several tissue type has provided new opportunities to assess cancer stem cell (CSC) activity by allowing them to propagate under conditions that resemble the microenvironment for growth of tumors. One tissue type widely used for stem cell investigations is mammary tissue, and the sphere formation assay has been used in both normal mammary tissue and in breast cancer. Here, we describe detailed experimental methodology for generating and propagating spheres from normal mammary tissue and primary breasttumors of mice, patient derived xenografts (PDXs) and breast cancercell lines. We further describe how these sphere cultures can be employed for coculture assays to assess the effect of tumor microenvironment (TME) on self-renewal ability of CSCs in breast cancer.

Interferon-gamma inhibits aldehyde dehydrogenasebright cancer stem cells in the 4T1 mouse model of breast cancer.

Background:Despite improvements in disease diagnosis, treatment, and prognosis, breast cancer is still a leading cause of cancer death for women. Compelling evidence suggests that targeting cancer stem cells (CSCs) have a crucial impact on overcoming the current shortcomings of chemotherapy and radiotherapy. In the present study, we aimed to study the effects of T cells and a critical anti-tumor cytokine, interferon-gamma (IFN-γ), on breast cancer stem cells.Methods:BALB/c mice and BALB/c nude mice were subcutaneously injected with 4T1 tumor cells. Tumor growth and pulmonary metastasis were assessed. ALDEFLOUR™ assays were performed to identify aldehyde dehydrogenasebright (ALDHbr) tumor cells. ALDHbr cells as well as T cells from tumor-bearing BALB/c mice were analyzed using flow cytometry. The effects of CD8+ T cells on ALDHbr tumor cells were assessed in vitro and in vivo. The expression profiles of ALDHbr and ALDHdim 4T1 tumor cells were determined. The levels of plasma IFN-γ were measured by enzyme-linked immunosorbent assay, and their associations with the percentages of ALDHbr tumor cells were evaluated. The effects of IFN-γ on ALDH expression and the malignancy of 4T1 tumor cells were analyzed in vitro.Results:There were fewer metastatic nodules in tumor-bearing BALB/c mice than those in tumor-bearing BALB/c nude mice (25.40 vs. 54.67, P < 0.050). CD8+ T cells decreased the percentages of ALDHbr 4T1 tumor cells in vitro (control vs. effector to target ratio of 1:1, 10.15% vs. 5.76%, P < 0.050) and in vivo (control vs. CD8+ T cell depletion, 10.15% vs. 21.75%, P < 0.001). The functions of upregulated genes in ALDHbr 4T1 tumor cells were enriched in the pathway of response to IFN-γ. The levels of plasma IFN-γ decreased gradually in tumor-bearing BALB/c mice, while the percentages of ALDHbr tumor cells in primary tumors increased. IFN-γ at a concentration of 26.68 ng/mL decreased the percentages of ALDHbr 4T1 tumor cells (22.88% vs. 9.88%, P < 0.050) and the protein levels of aldehyde dehydrogenase 1 family member A1 in 4T1 tumor cells (0.86 vs. 0.49, P < 0.050) and inhibited the abilities of sphere formation (sphere diameter <200 μm, 159.50 vs. 72.0; ≥200 μm, 127.0 vs. 59.0; both P < 0.050) and invasion (89.67 vs. 67.67, P < 0.001) of 4T1 tumor cells.Conclusion:CD8+ T cells and IFN-γ decreased CSC numbers in a 4T1 mouse model of breast cancer. The application of IFN-γ may be a potential strategy for reducing CSCs in breast cancer.

The LSD1 inhibitor iadademstat (ORY-1001) targets SOX2-driven breast cancer stem cells: a potential epigenetic therapy in luminal-B and HER2-positive breast cancer subtypes.

SOX2 is a core pluripotency-associated transcription factor causally related to cancer initiation, aggressiveness, and drug resistance by driving the self-renewal and seeding capacity of cancer stem cells (CSC). Here, we tested the ability of the clinically proven inhibitor of the lysine-specific demethylase 1 (LSD1/KDM1A) iadademstat (ORY-100) to target SOX2-driven CSC in breast cancer. Iadademstat blocked CSC-driven mammosphere formation in breast cancer cell lines that are dependent on SOX2 expression to maintain their CSC phenotype. Iadademstat prevented the activation of an LSD1-targeted stemness-specific SOX2 enhancer in CSC-enriched 3-dimensional spheroids. Using high-throughput transcriptional data available from the METABRIC dataset, high expression of SOX2 was significantly more common in luminal-B and HER2-enriched subtypes according to PAM50 classifier and in IntClust1 (high proliferating luminal-B) and IntClust 5 (luminal-B and HER2-amplified) according to integrative clustering. Iadademstat significantly reduced mammospheres formation by CSC-like cells from a multidrug-resistant luminal-B breast cancer patient-derived xenograft but not of those from a treatment-naïve luminal-A patient. Iadademstat reduced the expression of SOX2 in luminal-B but not in luminal-A mammospheres, likely indicating a selective targeting of SOX2-driven CSC. The therapeutic relevance of targeting SOX2-driven breast CSC suggests the potential clinical use of iadademstat as an epigenetic therapy in luminal-B and HER2-positive subtypes.

Abstract P4-04-02: Epigenomic analysis of cancer stem cells (CSCs) from triple-negative breast cancer (TNBC) reveals p63 and p73 as core metastasis drivers

Abstract Cancer stem cells (CSCs) are key drivers of cancer metastasis, drug resistance, and disease recurrence. While the transcriptional regulatory circuitry that underlies the generation and propagation of the breast CSC state is not completely understood, defining the core regulators of the CSC state has the potential to reveal how these cells arise and point to potential targetable pathways for therapeutic intervention. We isolated CSCs by selecting for surface expression of integrin β4 (ITGB4). ITGB4-hi cells are highly enriched for CSCs and display cellular and molecular features indicative of their residence in an intermediate EMT state, including the ability to seed metastasis in vivo. Using ITGB4-hi CSCs isolated from the SUM159 breast cancer cell line, we deployed epigenome mapping by H3K27ac ChIP-seq, nucleosome occupancy by ATAC-seq, and transcriptome analysis by RNA-seq. Using comparative analysis of enhancer usage and DNA accessibility, we identified the transcriptional regulatory circuitry of breast cancer CSCs and pinpointed the master transcription factors that control the CSC state. We find that p63/p73 proteins function as master transcriptional regulators in breast CSCs and establish super-enhancers at critical CSC state genes. Loss of p63 and p73 disrupts the transcriptional circuitry of CSCs and leads to a highly mesenchymal state that is incompatible with metastatic colonization. Re-introduction of p63/p73 expression into non-CSCs leads to reactivation of the CSC transcriptional program and enables metastasis. These findings reveal the unique transcriptional circuitry of CSCs and suggest potential dependencies and pathways for therapeutic targeting of cells in the CSC state. Citation Format: Arthur Lambert, Christopher Fiore, Yogesh Chutake, Elisha Verhaar, Mei Wei Chen, Joana Donaher, Ferenc Reinhardt, Ian Engstrom, Bingbing Yuan, Brian Bierie, Daneyal Farouq, John Carulli, Eric Olson, Matthew Guenther, Robert Weinberg. Epigenomic analysis of cancer stem cells (CSCs) from triple-negative breast cancer (TNBC) reveals p63 and p73 as core metastasis drivers [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-04-02.

Role of CD44 in breast cancer.

Breast cancer (BC) is among the most prevalent type of malignancy affecting females worldwide. BC is classified into different types according to the status of the expression of receptors such as estrogen receptor (ER), human epidermal growth factor receptor 2 (HER2), and progesterone receptor (PR). Androgen receptor (AR) appears to be a promising therapeutic target of BC. Binding of 5α-dihydrotestosterone (DHT) to AR controls the expression of microRNA (miRNA) molecules in BC, consequently, affecting protein expression. One of these proteins is the transmembrane glycoprotein cluster of differentiation 44 (CD44). Remarkably, CD44 is a common marker of cancer stem cells in BC. It functions as a co-receptor for a broad diversity of extracellular matrix ligands. Several ligands, primarily hyaluronic acid (HA), can interact with CD44 and mediate its functions. CD44 promotes a variety of functions independently or in cooperation with other cell-surface receptors through activation of varied signaling pathways like Rho GTPases, Ras-MAPK, and PI3K/AKT pathways to regulate cell adhesion, migration, survival, invasion, and epithelial-mesenchymal transition. In this review, we present the relations between AR, miRNA, and CD44 and their roles in BC.

Knockdown of XB130 restrains cancer stem cell-like phenotype through inhibition of Wnt/β-Catenin signaling in breast cancer.

The cancer stem cells (CSCs) is a subset of cancer cells that possess stem cell properties, which plays a crucial role in the occurrence, metastasis, and recurrence of the tumor. XB130 is a novel adapter protein potentially serves as a functional factor in CSCs. To determine the role of CSCs in breast cancer, we focused on the study of XB130. In our study, we found that XB130 expression was significantly upregulated in breast cancer and was closely related to the clinicopathologic characteristics, overall survival and poor prognosis of breast cancer patients. Functionally, we found that knockdown of XB130 was not only played an important role in proliferation, epithelial-mesenchymal transition (EMT), and metastasis in breast cancer cells but also exhibited potent antitumor activity in animal tumor models. Moreover, we demonstrated that silencing endogenous XB130 regulated the cancer stem cell-like properties of breast cancer, including the formation of self-renewing spheres and the proportion of breast cancer SP+ cells. Mechanistically, our studies indicated that downregulation of XB130 restrained the EMT and Wnt/β-catenin signaling, so as to weaken the tumor-initiating cell-like phenotype of breast cancer cells. This study indicates that XB130 plays an important role in maintaining the EMT and stem cell-like characteristics of breast cancer cells, supporting the significance of XB130 as a new potential therapeutic target for early diagnosis and prognosis of breast cancer.

Cadherin 11 Inhibition Downregulates β-catenin, Deactivates the Canonical WNT Signalling Pathway and Suppresses the Cancer Stem Cell-Like Phenotype of Triple Negative Breast Cancer.

Background: Cancer stem cells (CSCs) promote tumor progression and distant metastasis in breast cancer. Cadherin 11 (CDH11) is overexpressed in invasive breast cancer cells and implicated in distant bone metastases in several cancers. The WNT signalling pathway regulates CSC activity. Growing evidence suggest that cadherins play critical roles in WNT signalling pathway. However, CDH11 role in canonical WNT signalling and CSCs in breast cancer is poorly understood. Methods: We investigated the functional association between CDH11 and WNT signalling pathway in triple negative breast cancer (TNBC), by analyzing their expression profile in the TCGA Breast Cancer (BRCA) cohort and immunohistochemical (IHC) staining of TNBC samples. Results: We observed a significant correlation between high CDH11 expression and poor prognosis in the basal and TNBC subtypes. Also, CDH11 expression positively correlated with β-catenin, wingless type MMTV integration site (WNT)2, and transcription factor (TCF)12 expression. IHC results showed CDH11 and β-catenin expression significantly correlated in TNBC patients (p < 0.05). We also showed that siRNA-mediated loss-of-CDH11 (siCDH11) function decreases β-catenin, Met, c-Myc, and matrix metalloproteinase (MMP)7 expression level in MDA-MB-231 and Hs578t. Interestingly, immunofluorescence staining showed that siCDH11 reduced β-catenin nuclear localization and attenuated TNBC cell migration, invasion and tumorsphere-formation. Of translational relevance, siCDH11 exhibited significant anticancer efficacy in murine tumor xenograft models, as demonstrated by reduced tumor-size, inhibited tumor growth and longer survival time. Conclusions: Our findings indicate that by modulating β-catenin, CDH11 regulates the canonical WNT signalling pathway. CDH11 inhibition suppresses the CSC-like phenotypes and tumor growth of TNBC cells and represents a novel therapeutic approach in TNBC treatment.

Doxycycline, an Inhibitor of Mitochondrial Biogenesis, Effectively Reduces Cancer Stem Cells (CSCs) in Early Breast Cancer Patients: A Clinical Pilot Study.

Background and objectives: Cancer stem cells (CSCs) have been implicated in tumor initiation, recurrence, metastatic spread and poor survival in multiple tumor types, breast cancers included. CSCs selectively overexpress key mitochondrial-related proteins and inhibition of mitochondrial function may represent a new potential approach for the eradication of CSCs. Because mitochondria evolved from bacteria, many classes of FDA-approved antibiotics, including doxycycline, actually target mitochondria. Our clinical pilot study aimed to determine whether short-term pre-operative treatment with oral doxycycline results in reduction of CSCs in early breast cancer patients.Methods: Doxycycline was administered orally for 14 days before surgery for a daily dose of 200 mg. Immuno-histochemical analysis of formalin-fixed paraffin-embedded (FFPE) samples from 15 patients, of which 9 were treated with doxycycline and 6 were controls (no treatment), was performed with known biomarkers of “stemness” (CD44, ALDH1), mitochondria (TOMM20), cell proliferation (Ki67, p27), apoptosis (cleaved caspase-3), and neo-angiogenesis (CD31). For each patient, the analysis was performed both on pre-operative specimens (core-biopsies) and surgical specimens. Changes from baseline to post-treatment were assessed with MedCalc 12 (unpaired t-test) and ANOVA.Results: Post-doxycycline tumor samples demonstrated a statistically significant decrease in the stemness marker CD44 (p-value < 0.005), when compared to pre-doxycycline tumor samples. More specifically, CD44 levels were reduced between 17.65 and 66.67%, in 8 out of 9 patients treated with doxycycline. In contrast, only one patient showed a rise in CD44, by 15%. Overall, this represents a positive response rate of nearly 90%. Similar results were also obtained with ALDH1, another marker of stemness. In contrast, markers of mitochondria, proliferation, apoptosis, and neo-angiogenesis, were all similar between the two groups.Conclusions: Quantitative decreases in CD44 and ALDH1 expression are consistent with pre-clinical experiments and suggest that doxycycline can selectively eradicate CSCs in breast cancer patients in vivo. Future studies (with larger numbers of patients) will be conducted to validate these promising pilot studies.

Extra-virgin olive oil contains a metabolo-epigenetic inhibitor of cancer stem cells.

Targeting tumor-initiating, drug-resistant populations of cancer stem cells (CSC) with phytochemicals is a novel paradigm for cancer prevention and treatment. We herein employed a phenotypic drug discovery approach coupled to mechanism-of-action profiling and target deconvolution to identify phenolic components of extra virgin olive oil (EVOO) capable of suppressing the functional traits of CSC in breast cancer (BC). In vitro screening revealed that the secoiridoid decarboxymethyl oleuropein aglycone (DOA) could selectively target subpopulations of epithelial-like, aldehyde dehydrogenase (ALDH)-positive and mesenchymal-like, CD44+CD24−/low CSC. DOA could potently block the formation of multicellular tumorspheres generated from single-founder stem-like cells in a panel of genetically diverse BC models. Pretreatment of BC populations with noncytotoxic doses of DOA dramatically reduced subsequent tumor-forming capacity in vivo. Mice orthotopically injected with CSC-enriched BC-cell populations pretreated with DOA remained tumor-free for several months. Phenotype microarray-based screening pointed to a synergistic interaction of DOA with the mTOR inhibitor rapamycin and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine. In silico computational studies indicated that DOA binds and inhibits the ATP-binding kinase domain site of mTOR and the S-adenosyl-l-methionine (SAM) cofactor-binding pocket of DNMTs. FRET-based Z-LYTE™ and AlphaScreen-based in vitro assays confirmed the ability of DOA to function as an ATP-competitive mTOR inhibitor and to block the SAM-dependent methylation activity of DNMTs. Our systematic in vitro, in vivo and in silico approaches establish the phenol-conjugated oleoside DOA as a dual mTOR/DNMT inhibitor naturally occurring in EVOO that functionally suppresses CSC-like states responsible for maintaining tumor-initiating cell properties within BC populations.

Association between inflammation and cancer stem cell phenotype in breast cancer.

Inflammation and cancer stem cells (CSCs) are becoming increasingly recognized as components of tumorigenesis in breast cancer. In the present study, the association between inflammation and BCSC phenotype was evaluated in human breast cancer tissue. Immunohistochemical staining for cluster of differentiation (CD)24, 44, 4, 8 and 68 was performed using tissue microarray blocks containing 47 consecutive cases of invasive breast carcinoma and 10 normal breast tissue samples. The levels of inflammatory modulators and cytokines, and intratumoral or peritumoral lymphocyte infiltration, were assessed. BCSCs were defined as CD44+/CD24- tumor cells. In total, 21.3% of samples exhibited the CD44+/CD24- phenotype. This phenotype was identified to be significantly inversely associated with lymph node metastasis. In addition, the CD44+/CD24- phenotype was significantly associated with the molecular subtype of breast cancer, and was particularly increased in the basal-like subtype. Furthermore, the CD44+/CD24- phenotype was significantly associated with intratumoral inflammation and tumor-infiltrating CD4+ T cell counts. Notably, tumor-infiltrating CD4+ T cells were significantly increased in patients with the basal-like molecular subtype of breast cancer. In conclusion, the present study identified a significant association between inflammation and the CD44+/CD24- phenotype in breast cancer. These results suggest that the interaction between inflammation and CSCs may affect the tumorigenesis and progression of breast cancer. Further studies are required to clarify the role of inflammation and CSCs in breast cancer.

ARE CD44+/CD24– CELLS THE ASSUMED CANCER STEM CELLS IN BREAST CANCER

To determine the validation of the CSC model for cell surface markers such as CD44and CD24and their clinical significance. Primary tumor samples of 45patients with invasive BC without chemotherapy prior to surgery exposure were examined in paraffin blocks. CD44and CD24antigens expression was evaluated by the percentage of positive cells using different chromogens and the MultiVision detection system by immunohistochemical method. In this research the evaluation was determined by the following criteria: (-), negative- expression in < 10% of tumor cells; (+), positive- expression in ≥10% of cells. The same scoring system was applied for the expression of CD44+/CD24-. 62.2% of investigated patients are patients older than 50years and most of them with stage II of disease (71.0%) and luminal tumor subtypes (68.9%). We analysed the expression of CD44, CD24 and CD44+/CD24- for diffe-rent patients with dividing them into two groups. The group A consists of patients with unfavorable prognosis (relapses and metastases have occurred in the first three years after diagnosis), and the group B- with a favourable prognosis (thedevelopment of metastases after three years). Median disease-free survival in the group A is 19months, in the group B- 46months. The difference between the overall survival (OS) curves in the groups A and B is statistically significant (p <0.001), the risk of death was higher in the group A (hazard ratio (HR) 5.9; confidence interval (CI) 2.3-15.2). The content of CD44 cells did not differ statistically between groups A and B (p=0.18), but there was a tendency for increasing in OS with the existence of CD44+ cells (p=0.056). The distribution of the expression of CD24marker did not differ between the groups (p=0.36) as well as the OS curves (p=0.59). Analysis of the expression of CD44+/CD24- which were considered as possible CSC, revealed a paradoxical increase (p=0.03) of the frequency in patients of the group B (40.9%) compared to the group A (8.7%). Nevertheless, the comparison of the clinical outcomes did not reveal a statistically significant difference in the survival curves in the groups with existence and absence of CD44+/CD24- expression (p = 0.08). Theanalysis showed the increasing of the risk of worse clinical outcomes in the cases of expression absence of CD44+/CD24- (HR 2.8; CI 1.1-6.8). As a result of our research, the analysis of the quantity of assumed stem cells of the BC, which were identified by immunohistochemistry as CD44 and CD24 cells, failed to detect a statistically significant relation between groups of patients with different prognosis, and the identification of their expression is not enough for the characteristics of CSC. Theobtained data demonstrating the worst clinical outcome in the cases of absence of CD44+/CD24- expression apparently require further investigations and the validation of the immunohistochemical method with the determination of the cut-off line in defining of CD44and CD24status.

Phenotypic and microRNA transcriptomic profiling of the MDA-MB-231 spheroid-enriched CSCs with comparison of MCF-7 microRNA profiling dataset.

Breast cancer spheroids have been widely used as in vitro models of cancer stem cells (CSCs), yet little is known about their phenotypic characteristics and microRNAs (miRNAs) expression profiles. The objectives of this research were to evaluate the phenotypic characteristics of MDA-MB-231 spheroid-enriched cells for their CSCs properties and also to determine their miRNAs expression profile. Similar to our previously published MCF-7 spheroid, MDA-MB-231 spheroid also showed typical CSCs characteristics namely self-renewability, expression of putative CSCs-related surface markers and enhancement of drug resistance. From the miRNA profile, miR-15b, miR-34a, miR-148a, miR-628 and miR-196b were shown to be involved in CSCs-associated signalling pathways in both models of spheroids, which highlights the involvement of these miRNAs in maintaining the CSCs features. In addition, unique clusters of miRNAs namely miR-205, miR-181a and miR-204 were found in basal-like spheroid whereas miR-125, miR-760, miR-30c and miR-136 were identified in luminal-like spheroid. Our results highlight the roles of miRNAs as well as novel perspectives of the relevant pathways underlying spheroid-enriched CSCs in breast cancer.

Abstract 1916: Peptidylarginine deiminase IV (PADI4) is a novel tumor suppressor that may contribute to regulation of breast cancer stem cell dynamics

Abstract Breast cancer is a global problem that accounts for almost a fourth of all cancers in women. Despite the many therapeutic strategies currently in use, treated patients often suffer from cancer relapse and metastasis due to the presence of a subpopulation of tumorigenic cells capable of self-renewal and termed cancer stem cells (CSCs). To address the properties of this critical sub-population, we utilized our recently-developed lentiviral CSC reporter carrying an Oct4/Sox2 response element coupled to a green fluorescent protein (SORE6-GFP) to detect and isolate the CSC population in a low-grade ER+ human breast cancer model, MCF10Ca1h, by FACS. Whole transcriptome sequencing analysis (RNA-seq) on the sorted cells identified Peptidylarginine deiminase IV (PADI4) as differentially expressed between CSCs and non-CSCs. PADI4 was recently shown to regulate citrullination of histone H1, displacing it from chromatin and resulting in global chromatin decondensation and pluripotency induction in embryonic stem cells (Christophorou, et al., 2014, Nature 507:104). Thus, we hypothesized that PADI4 may also regulate the stemness phenotype in breast cancer CSCs, likely through effects on chromatin structure. We showed that PADI4 protein expression is higher in luminal breast cancer cell lines than other subtypes, and we did shRNA knockdown (KD) of PADI4 in the luminal MCF10Ca1h model. PADI4 KD increased tumorosphere formation and clonogenicity indicating increased CSC population/activity. Additionally, MCF10Ca1h cells treated with a PADI4 selective inhibitor showed an increase in CSCs as assessed using the SORE6-GFP stem cell reporter. In vivo limiting dilution studies demonstrate that PADI4 KD increased tumor incidence at low cell inoculum, reflecting a statistically significant 2-4 fold increase in CSCs upon PADI4 KD. Our findings suggest that PADI4 may function as a tumor suppressor in luminal breast cancer. In support of this conclusion, deep deletions of PADI4 locus are found in 1% of human breast cancers in the TCGA datasets. Analysis of the effect of PADI4 KD on chromatin organization in the CSC and non-CSC compartments is ongoing. Citation Format: Nellie Moshkovich. Peptidylarginine deiminase IV (PADI4) is a novel tumor suppressor that may contribute to regulation of breast cancer stem cell dynamics [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 1916. doi:10.1158/1538-7445.AM2017-1916

Abstract C22: A phase Ib study of the CXCR1/2 inhibitor Reparixin in combination with weekly paclitaxel in metastatic HER2 negative breast cancer - final analysis

Abstract Background. Cancer Stem Cells (CSC) have the ability to self-renew and generate the full range of cells that make up a bulk tumor. Experimental models and retrospective clinical observations point to CSC as responsible for tumor recurrence and metastasis. An ideal CSC targeting agent should be a non toxic molecule that can be safely administered also in combination with chemotherapy to improve disease control. CXCR1, one of the receptors for CXCL8, has been identified on breast cancer CSC. Reparixin, an allosteric inhibitor of CXCR1, reduced CSC in breast cancer (BC) xenografts (Ginestier C et al., JCI 2010) both as single agent and in combination with taxane chemotherapy. Methods. Patients were female aged ≥ 18 years with HER-2 negative metastatic BC, non taxane-refractory, who had received up to 3 prior chemotherapy (CT) lines for advanced BC (not including neo/adjuvant CT), had measurable disease according to RECIST 1.1, ECOG PS of 0-1, adequate organ function, and no brain metastases. Patients received a 3-day run-in with reparixin oral tablets 3 times daily (tid) followed by paclitaxel 80 mg/m2 (days 1, 8, and 15 for 28-day cycle) + reparixin oral tablets tid for 21 days. Three dose levels of 3-6 subjects were explored: 400 mg, 800 mg and 1200 mg oral reparixin tid. The highest safe dose level was expanded twice to gain additional safety and activity data. Treatment continued until disease progression, unacceptable toxicity or withdrawal of consent. Primary endpoints were safety and tolerability, and pharmacokinetic (PK) profile of the combination treatment. Among secondary endpoints, assessment of disease response every 2 cycles for indication of efficacy and correlative evaluations on peripheral blood samples were conducted. First analysis (i.e., 60 days post last patient in, LPI) of the results from this trial was reported earlier (Schott AF et al., SABC 2014). Results. Herein we report data at 6 months post LPI. From 02/2012 to 04/2014, 33 patients entered the study (4 in cohort 1, 3 in cohort 2 and 26 in cohort 3). 30 patients were evaluable for safety. Neither grade 4 adverse events (AE) nor Serious AE related to reparixin were reported. 9/23 patients at the highest dose level reported Grade 3 AE among which granulocytopenia (3 patients) and peripheral neuropathy (2 patients) that are commonly seen with paclitaxel alone. Overall, 8 confirmed responses (2 CR, 6 PR) were observed among 26 patients who underwent at least 1 tumor assessment (every 8 weeks). Response duration (days) was 645+, 466+ (for CR) and 280+, 169, 141, 113, 113+, 47 (for PR). Two additional patients experienced SD &amp;gt; 6 months (318 and 288 days, respectively). Of responding patients, all but one was from cohort 3. Median TTP (days) in the safety population was 58, 67 and 170 in cohorts 1, 2 and 3, respectively. Conclusions. Combination treatment demonstrated good tolerability with low incidence and severity of adverse reactions. The recommended dose of reparixin for the combination was established at 1200 mg tid. A sizeable response rate and mTTP was recorded, with some interesting long term responders. A randomized phase II study of the combination versus single agent weekly paclitaxel in frontline treatment of patients with metastatic triple-negative BC is ongoing (NCT02370238). Citation Format: Anne F. Schott, Max S. Wicha, Raymond P. Perez, Giraldo Kato, Tiffany Avery, Massimo Cristofanilli, James M. Reuben, R. Katherine Alpaugh, Pier Adelchi Ruffini, Susan Mccanna, Lori J. Goldstein. A phase Ib study of the CXCR1/2 inhibitor Reparixin in combination with weekly paclitaxel in metastatic HER2 negative breast cancer - final analysis. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C22.

Abstract 3319: Identification of cervical cancer stem cells by using an imaging system for proteasome activity

Abstract Cervical cancer is one of the most common cancers among women worldwide and the fourth most common cause of cancer death in women worldwide (275,100 deaths in 2008). For advanced cervical cancer, concurrent radiotherapy and chemotherapy are commonly administered. However, the 5-year survival rate remains at only ∼60%, indicating the need for significant improvements in clinical outcomes. Recurrence and metastatic potential can be due to a specific radioresistant subpopulation of cells with stem-like characteristics, cancer stem cells (CSCs) which maintain the capacity to regenerate entire tumors. Targeting of the CSCs is a promising avenue to explore to develop new therapies for this devastating cancer. Recently, cancer cells with low proteasome activity have been identified as CSCs in breast cancer, glioma, and pancreatic cancer with a fluorescence marker system for level of proteasome activity. We stably infected two cervical cancer cell lines, HeLa and CaSki, with an expression vector for a fusion protein between the green fluorescent protein, ZsGreen, and the C-terminal degron of murine ornithine decarboxylase to monitor 26S proteasome activity in living cells. we divided these cells into ZsGreen-high (low proteasome activity) and ZsGreen-low (high proteasome activity) groups according to their fluorescence intensity. Sphere forming assay revealed that the self-renewal ability of the ZsGreen-high population was significantly higher than that of the ZsGreen-low population. Tumorigenicity assay confirmed that the ZsGreen-high population exhibited higher tumorigenic potential than the ZsGreen-low population. The radioresistance of the ZsGreen-high population of both HeLa and CaSki cells and the chemoresistance of the ZsGreen-high population of CaSki cells were confirmed by clonogenic survival assay and the MTT assay, respectively. These results indicated that ZsGreen-high populations of both the HeLa and CaSki cell lines possess CSC-like properties and therapeutic resistance. We conclude that established cervical cancer cell lines are heterogeneous with regard to their intrinsic proteasome activity and that they contain CSCs-enriched subpopulations that can be identified by low proteasome activity. Citation Format: Keisuke Tamari, Hideshi Ishii, Kazuhiko Hayashi, Masamitsu Konno, Koichi Kawamoto, Naohiro Nishida, Jun Kozeki, Takahito Fukusumi, Yuichiro Doki, Masaki Mori, Kazuhiko Ogawa. Identification of cervical cancer stem cells by using an imaging system for proteasome activity. [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 3319. doi:10.1158/1538-7445.AM2015-3319

Metformin and prostate cancer stem cells: a novel therapeutic target.

Prostate cancer is the second most frequently diagnosed cancer in the world. Localized disease can be effectively treated with radiation therapy or radical prostatectomy. However, advanced prostate cancer is more difficult to treat and if metastatic, is incurable. There is a need for more effective therapy for advanced prostate cancer. One potential target is the cancer stem cell (CSC). CSCs have been described in several solid tumors, including prostate cancer, and contribute to therapeutic resistance and tumor recurrence. Metformin, a common oral biguanide used to treat type 2 diabetes, has been demonstrated to have anti-neoplastic effects. Specifically, metformin targets CSCs in breast cancer, pancreatic cancer, glioblastoma and colon cancer. Metformin acts directly on the mitochondria to inhibit oxidative phosphorylation and reduce mitochondrial ATP production. This forces tumor cells to compensate by increasing the rate of glycolysis. CSCs rely heavily on mitochondrial oxidative phosphorylation for energy production. The glycolytic switch results in an energy crisis in these cells. Metformin could be used to exploit this metabolic weakness in CSCs. This would increase CSC sensitivity to conventional cancer therapies, circumventing treatment resistance and enhancing treatment efficacy. This review will explore the characteristics of prostate CSCs, their role in tumor propagation and therapeutic resistance and the role of metformin as a potential prostate CSC sensitizer to current anticancer therapies.