Subset Of Cancer Stem Cells Research Articles

HDAC11 Regulates Glycolysis through the LKB1/AMPK Signaling Pathway to Maintain Hepatocellular Carcinoma Stemness.

Hepatocellular carcinoma (HCC) contains a subset of cancer stem cells (CSC) that cause tumor recurrence, metastasis, and chemical resistance. Histone deacetylase 11 (HDAC11) mediates diverse immune functions and metabolism, yet little is known about its role in HCC CSCs. In this study, we report that HDAC11 is highly expressed in HCC and is closely related to disease prognosis. Depletion of HDAC11 in a conditional knockout mouse model reduced hepatocellular tumorigenesis and prolonged survival. Loss of HDAC11 increased transcription of LKB1 by promoting histone acetylation in its promoter region, thereby activating the AMPK signaling pathway and inhibiting the glycolysis pathway, which in turn leads to the suppression of cancer stemness and HCC progression. Furthermore, HDAC11 overexpression reduced HCC sensitivity to sorafenib. Collectively, these data propose HDAC11 as a new target for combination therapy in patients with kinase-resistant HCC. SIGNIFICANCE: This study finds that HDAC11 suppresses LKB1 expression in HCC to promote cancer stemness, progression, and sorafenib resistance, suggesting the potential of targeting HDAC11 to treat HCC and overcome kinase inhibitor resistance.

Exploitation of the vitamin A/retinoic acid axis depletes ALDH1-positive cancer stem cells and re-sensitises resistant non-small cell lung cancer cells to cisplatin

Despite advances in personalised medicine and the emerging role of immune checkpoints in directing treatment decisions in subsets of lung cancer patients, non-small cell lung cancer (NSCLC) remains the most common cause of cancer-related deaths worldwide. The development of drug resistance plays a key role in the relapse of lung cancer patients in the clinical setting, mainly due to the unlimited renewal capacity of residual cancer stem cells (CSCs) within the tumour cell population during chemotherapy. In this study, we investigated the function of the CSC marker, aldehyde dehydrogenase (ALDH1) in retinoic acid cell signalling using an in vitro model of cisplatin resistant NSCLC. The addition of key components in retinoic acid cell signalling, all-trans retinoic acid (ATRA) and retinol to cisplatin chemotherapy, significantly reduced ALDH1-positive cell subsets in cisplatin resistant NSCLC cells relative to their sensitive counterparts resulting in the re-sensitisation of chemo-resistant cells to the cytotoxic effects of cisplatin. Furthermore, combination of ATRA or retinol with cisplatin significantly inhibited cell proliferation, colony formation and increased cisplatin-induced apoptosis. This increase in apoptosis may, at least in part, be due to differential gene expression of the retinoic acid (RARα/β) and retinoid X (RXRα) nuclear receptors in cisplatin-resistant lung cancer cells. These data support the concept of exploiting the retinoic acid signalling cascade as a novel strategy in targeting subsets of CSCs in cisplatin resistant lung tumours.

Defective Natural Killer Cells in Melanoma: Role of NKG2D in Pathogenesis and Immunotherapy.

Melanoma is the most aggressive and deadliest form of skin cancer, and its prognosis is very poor. Although the early detection is responsive to many treatments, metastatic melanoma is refractory to most of them. In the United States, skin melanoma is the fifth most common type of cancer in men and the sixth in women. Current treatment modalities, depending on the cancer stage, consist primarily of surgical excision, chemotherapy, adjuvant therapy, targeted therapies, and immunotherapy. Despite the wide range of therapeutic options and the steadily increasing response rates, a large subset of the treated patients relapse and develop resistance to further treatments. One novel approach in preclinical and clinical trials in immunotherapy is the adaptation of natural killer (NK) cells against resistant cancer cells. NK cells can kill a variety of cancer cell types, as well as the cancer stem cells, while leaving normal cells intact. In skin melanoma, as in most cancers, NK cells in the tumor microenvironment (TME) are functionally impaired. Several factors underlie the defective cause of NK cells, one of which is the dysregulation of the activating receptor NKG2D. This is the dominant receptor in regulating the cytotoxic activity, cytokine production, and regulation of other receptors expressed on NK cells and other lymphocytes. The defective NK cells in cancer models were associated with tumor growth and metastasis. In this review, we discuss the role of NK cells and their phenotypic variants in skin melanoma. Using bioinformatics, we have further analyzed the expression of NKG2D, confirming its low transcript levels in patients with skin melanoma. Furthermore, we show that the CD133 subset of cancer stem cells expresses low levels of NKG2D. Based on these findings we discuss the potential therapeutic approaches that can be exploited to upregulate NKG2D in patients' NK cells and restore their anti-melanoma effects, resulting in tumor regression and prolonged survival.

Differential glycosylation of collagen modulates lung cancer stem cell subsets through β1 integrin-mediated interactions.

In lung cancer, CD133+ cells represent the subset of cancer stem cells (CSC) able to sustain tumor growth and metastatic dissemination. CSC function is tightly regulated by specialized niches composed of both stromal cells and extracellular matrix (ECM) proteins, mainly represented by collagen. The relevance of collagen glycosylation, a fundamental post‐translational modification controlling several biological processes, in regulating tumor cell phenotype remains, however, largely unexplored. To investigate the bioactive effects of differential ECM glycosylation on lung cancer cells, we prepared collagen films functionalized with glucose (Glc‐collagen) and galactose (Gal‐collagen) exploiting a neoglycosylation approach based on a reductive amination of maltose and lactose with the amino residues of collagen lysines. We demonstrate that culturing of tumor cells on collagen determines a glycosylation‐dependent positive selection of CSC and triggers their expansion/generation. The functional relevance of CD133+ CSC increase was validated in vivo, proving an augmented tumorigenic and metastatic potential. High expression of integrin β1 in its active form is associated with an increased proficiency of tumor cells to sense signaling from glycosylated matrices (glyco‐collagen) and to acquire stemness features. Accordingly, inhibition of integrin β1 in tumor cells prevents CSC enrichment, suggesting that binding of integrin β1 to Glc‐collagen subtends CSC expansion/generation. We provide evidence suggesting that collagen glycosylation could play an essential role in modulating the creation of a niche favorable for the generation and selection/survival of lung CSC. Interfering with this crosstalk may represent an innovative therapeutic strategy for lung cancer treatment.

Enhanced DNA damage response through RAD50 in triple negative breast cancer resistant and cancer stem-like cells contributes to chemoresistance.

A growing body of evidence supports the notion that cancer resistance is driven by a small subset of cancer stem cells (CSC), responsible for tumor initiation, growth, and metastasis. Both CSC and chemoresistant cancer cells may share common qualities to activate a series of self-defense mechanisms against chemotherapeutic drugs. Here, we aimed to identify proteins in chemoresistant triple-negative breast cancer (TNBC) cells and corresponding CSC-like spheroid cells that may contribute to their resistance. We have identified several candidate proteins representing the subfamilies of DNA damage response (DDR) system, the ATP-binding cassette, and the 26S proteasome degradation machinery. We have also demonstrated that both cell types exhibit enhanced DDR when compared to corresponding parental counterparts, and identified RAD50 as one of the major contributors in the resistance phenotype. Finally, we have provided evidence that depleting or blocking RAD50 within the Mre11-Rad50-NBS1 (MRN) complex resensitizes CSC and chemoresistant TNBC cells to chemotherapeutic drugs.

Abstract 6019: Identification of the neo-genesis of glioblastoma stem cells using label-free quantitative phase imaging

Abstract Introduction: Glioblastoma (GBM) is the most aggressive neurological cancer with a very poor prognosis due to its propensity to regenerate after medical interventions. Our experimental model is U87-MG cells, which contain subsets of cancer stem cells (CSC) and have the unusual property of spontaneously forming neurospheres in culture. We are investigating the origins of these stem cells. Materials and Methods: We employ recently developed time label-free, time-lapse quantitative phase imaging (QPI) technology that allows precise quantification of the refractive index (RI) distributions on a sub-cellular level. These measurements are stored in 2D or 3D arrays which can be presented as images or videos at various resolutions. Cells were seeded into sealable culture Petrie dishes and imaged while maintaining appropriate environmental controls. Results: We first noted CSCs in late stage cultures in exploratory experiments, where they presented as small cells (10-15 um) compared to the 50-100 um range of mature U8-MR cells. Their refractive index (RI) is 1.42, compared to about 1.40 for the cytoplasm of mature cells. QPI technology sensitivity enables almost complete separation between the two cell types in RI histograms. We exemplify a grouping of cells in an 80 um2 field of view, tracked in multiple time segments ranging from 20 minutes to 12 hours over a period of about 18 hours, containing a mature U87 which serves as a reference marker. Around this cell, there are 3 distinct pro-stem (PS) cells 12 to 16 um in size: PS-1 with numerous 0.5 um particles in the size range of mitochondria, PS-2 with a nucleus with nucleoli but no nuclear membrane, and PS-3 with a distinct nucleus, nucleoli, and cytosol. The cells are all connected in a network of nanotubes and tunnels. PS-1 and PS-2 are not very active in the early analysis, but they eventually move together and appear to fuse while still maintaining their individual shapes. PS-3 is very actively interacting with another cell on the border of the analysis window. It is extending and retracting a tube and is apparently moving materials both to and away from the other cell in a very regular and linear fashion, suggesting a primitive form of transcription. Discussion: The processes we observed are consistent with tumor stem cell generation by autophagy, mitophagy, and catabolization followed by reprograming of the remnants and formation of neoplastic stem cells. The novelty of our approach is determined by technical capabilities of our QPI platforms, which is non-invasive label-free approach coupled with ultra-high-resolution analysis, previously unobtainable in traditional time-lapse imaging systems. Citation Format: Ed Luther, Livia P. Mendes, Vladimir P. Torchilin. Identification of the neo-genesis of glioblastoma stem cells using label-free quantitative phase imaging [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 6019.

Abstract 4940: Heterogeneous SOX2 protein turnover in human glioblastoma subsets

Abstract The high-mobility group (HMG) DNA-binding protein SOX2 (SRY – Homology Box 2) imposes stemness sustaining transcription patterns in early vertebrate embryogenesis and further segregates with lineage determined stem cells of mostly epithelial or neuronal fate. Tumors originating from these tissues (carcinomas and gliomas) thus often show SOX2 expression, where the protein is either detected ubiquitously or confined to subsets of cells with functional overlap to the cancer stem cell (CSC) compartment. These pattern differences may coincide with gene duplication events in the first, or more selective forms of promoter activation in the latter scenario. More recently, we and others identified the PI3K/AKT/SOX2 axis as a post-transcriptional module of SOX2 nucleo-cytosolic shuttling and turnover regulation in multiple stem and cancer (stem) cell systems. We hypothesized that, next to genetic events, deviant modes of protein turnover regulation may further diversify the expression patterns of SOX2. To unravel such differences, we examined a panel of human glioblastoma cell lines (LN215, LN229, LN319, LN401, LN405, U87, and U373) for their endogenous SOX2 expression status, relative PI3K/AKT signaling activity, and anti-PI3K/AKT imposed depletion efficacy of the SOX2 protein. Surprisingly, relative SOX2 abundance and endogenous PI3K/AKT activity diverged within this gallery, with SOX2 positive cells in fact depending on STAT signaling as proliferation trigger. With regards to SOX2 turnover however, all but one cell line responded to PI3K/AKT pathway inhibition with a successive proteasomal clearance of SOX2, thus confirming the PI3K/AKT/SOX2 axis as a superordinate determinant of SOX2 protein stability. In U373 cells though, SOX2 levels did not change despite effective PI3K/AKT pathway inhibition, also not at extended incubation times and iterative drug dosing. Subsequent immunocytochemistry stainings confirmed these results indicating anti-AKT imposed nuclear depletion and subsequent proteasomal degradation of SOX2 in all except U373 cells, in which persistent nuclear SOX2 expression was again observed. Detailed functional examinations that relate to these differences, involving chemo-resistance analyses and tumorigenicity studies, as well as molecular profiling of underlying SOX2 protein modifications are currently pending and will be presented at the conference. Based on our observations we conclude that SOX2 turnover regulation and proliferation control do not converge in a canonical PI3K/AKT/SOX2 axis in SOX2 expressing glioblastoma. Moreover, selected glioblastoma cells effectively uncouple SOX2 homeostasis from PI3K/AKT signaling. We anticipate that a better understanding of the underlying molecular principles will help dissect differences among glioblastoma subtypes, and respectively between CSC subsets and non-stem “bulk” tumor cells. Citation Format: Thorsten Schaefer, Alain Dumlin, Christoph Schürch, Marie-Françoise Ritz, Gregor Hutter, Jean-Louis Boulay, Claudia Lengerke. Heterogeneous SOX2 protein turnover in human glioblastoma subsets [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 4940.

Cancer Stem Cell Plasticity - A Deadly Deal.

Intratumoral heterogeneity is a major ongoing challenge in the effective therapeutic targeting of cancer. Accumulating evidence suggests that a fraction of cells within a tumor termed Cancer Stem Cells (CSCs) are primarily responsible for this diversity resulting in therapeutic resistance and metastasis. Adding to this complexity, recent studies have shown that there can be different subpopulations of CSCs with varying biochemical and biophysical traits resulting in varied dissemination and drug-resistance potential. Moreover, cancer cells can exhibit a high level of plasticity or the ability to dynamically switch between CSC and non-CSC states or among different subsets of CSCs. In addition, CSCs also display extensive metabolic plasticity. The molecular mechanisms underlying these different interconnected axes of plasticity has been under extensive investigation and the trans-differentiation process of Epithelial to Mesenchymal transition (EMT) has been identified as a major contributing factor. Besides genetic and epigenetic factors, CSC plasticity is also shaped by non-cell-autonomous effects such as the tumor microenvironment (TME). In this review, we discuss the latest developments in decoding mechanisms and implications of CSC plasticity in tumor progression at biochemical and biophysical levels, and the latest in silico approaches being taken for characterizing cancer cell plasticity. These efforts can help improve existing therapeutic approaches by taking into consideration the contribution of cellular plasticity/heterogeneity in enabling drug resistance.

Epithelial Plasticity, Autophagy and Metastasis: Potential Modifiers of the Crosstalk to Overcome Therapeutic Resistance.

Epithelial-to-mesenchymal transition (EMT) initiates malignant transformation of cancer cells and is responsible for the generation of heterogenic subsets of cancer stem cells (CSCs). Signals in the form of environmental cues and paracrine factors within tumor microenvironment (TME) niche, support the possibility of generation of pool of CSCs with two distinct functional transition states. Cyclic CSCs with predominant epithelial phenotype, self-renew and differentiate into mature cancer cells. Subsets of autophagic/ non-cyclic CSCs with predominant mesenchymal phenotype have capacity to invade, metastasize, resist to apoptosis, escape immunosurveillance, survive chemotherapies and are majorly responsible for cancer mortality. Differences in phenotypic plasticity may form the basis of differential impact of therapeutic outcomes on heterogeneous subpopulations of CSCs. Activation of autophagy is responsible for the recycling of damaged organelles and protein aggregates, regulates EMT, confers the survival advantage to neoplastic cells to anti-cancer therapies, significantly affects the invasive potential of cancer cells and supports their metastatic dissemination in a tissue and tumor stage dependent manner. Therapy resistance is the primary obstacle in the complete ablation of tumor cells. Combinational treatments based on targeting autophagic CSCs and inhibiting EMT regulators may represent potential anticancer strategies for the prevention of cancer invasion, metastatic spread and disease relapse.

Targeting cancer stem cells from a metabolic perspective.

The process of cancer development and progression is driven by distinct subsets of cancer stem cells (CSCs) that contribute the self-renewal capacity as the major impetus to the metastatic dissemination and main impediments in cancer treatment. Given that CSCs are so scarce in the tumor mass, there are debatable points on the metabolic signatures of CSCs. As opposed to differentiated tumor progenies, CSCs display exquisite patterns of metabolism that, depending on the type of cancer, predominately rely on glycolysis, oxidative metabolism of glutamine, fatty acids, or amino acids for ATP production. Metabolic heterogeneity of CSCs, which attributes to differences in type and microenvironment of tumors, confers CSCs to have the plasticity to cope with the endogenous mitochondrial stress and exogenous microenvironment. In essence, CSCs and normal stem cells are like mirror images of each other in terms of metabolism. To achieve reprogramming, CSCs not only need to upregulate their metabolic engine for self-renewal and defense mechanism, but also expedite the antioxidant defense to sustain the redox homeostasis. In the context of these pathways, this review portrays the connection between the metabolic features of CSCs and cancer stemness. Identification of the metabolic features in conferring resistance to anticancer treatment dictated by CSCs can enhance the opportunity to open up a new therapeutic dimension, which might not only improve the effectiveness of cancer therapies but also annihilate the whole tumor without recurrence. Henceforth, we highlight current findings of potential therapeutic targets for the design of alternative strategies to compromise the growth, drug resistance, and metastasis of CSCs by altering their metabolic phenotypes. Perturbing the versatile skills of CSCs by barricading metabolic signaling might bring about plentiful approaches to discover novel therapeutic targets for clinical application in cancer treatments.Impact statementThis minireview highlights the current evidence on the mechanisms of pivotal metabolic pathways that attribute to cancer stem cells (CSCs) with a special focus on developing metabolic strategies of anticancer treatment that can be exploited in preclinical and clinical settings. Specific metabolic inhibitors that can overwhelm the properties of CSCs may impede tumor recurrence and metastasis, and potentially achieve a permanent cure of cancer patients.

A Modified Lentivirus-Based Reporter for Magnetic Separation of Cancer Stem Cells

Cancer stem cells (CSCs) are the most malignant subpopulation of tumor cells that possess a tumorigenic potential and resistantance to chemotherapy. These properties make CSCs a promising target for the development of targeted antitumor therapy which is especially in demand in highly aggressive cancers. However, the correct identification of cancer cells with stem properties remains a challenge. A newly developed lentivirus-based reporter SORE6 allows to directly identify CSCs by measuring gene expression of the embryonic stem cell factors SOX2 and OCT4. In the current study the reporter was modified to enable isolation of SOX2^(+)/OCT4^(+) cells by immunomagnetic separation and then was used to transduce HCC1806 and MDA-MB-453 triple-negative breast cancer (TNBC) cell lines. To validate the modified reporter, SOX2^(+)/OCT4^(+) populations were isolated and analyzed for the content of NANOG, a key transcription factor of pluropotency which expression is regulated by SOX2/OCT4. The percentage of SOX2^(+)/OCT4^(+) cells was assessed for each cell line. An increased content of NANOG protein was found in isolated SOX2^(+)/OCT4^(+) cell fractions indicating that the modified reporter is suitable for further studying the CSC subset.

Cancer Stem Cells and Osteosarcoma: Opportunities and Limitations

Osteosarcoma (OS) is the most common primary bone malignancy and is a leading cause of cancer-related death in children and young adults. Combination chemotherapy developed 3 decades ago significantly improved long-term survival compared to surgery alone. However, despite notable tumor cytoreduction and remission, the 5-year survival rate has remained static at ∼70% since, and the surviving patients have high chemoresistance with sustained risk of recurrent OS that has propensity to metastasize. After metastasis, the 5-year survival rate is abysmally low (∼10% to 20%). Emerging new evidence has revealed that within the heterogenous OS tumor evolves a subset of cancer stem cells with progenitor abilities that contribute to chemoresistance, tumor recurrence, and metastasis. Mechanistic insight into these cells has rekindled the hope for novel agents and treatment regimens for OS patients. In this review we discuss the recent advances towards the understanding of OS with emphasis on the functions of the cancer stem cells, microenvironment niche, genetic, epigenetic factors, and signaling pathways as well as their potential for new therapeutics.

Abstract 2033: Bidirectional paracrine IL-33-TGF-beta signaling underlies a tumor-promoting stem cell niche

Abstract Malignant tumor progression and aggressive tumor recurrence after treatment are driven by subsets of cancer stem cells (CSCs), but targeting CSCs remains a major challenge due to their plasticity. CSCs in squamous cell carcinoma reside at the tumor-stromal interface, a paramount tumor microenvironment (TME) for interactive crosstalk between cancer cells and various other cells via soluble mediators, and tumor-infiltrating immune cells are pivotal regulators of tumor progression. However, the molecular link between tumor-associated immune-inflammatory responses and the regulation of CSCs are largely unknown. To define a framework of the CSC niche, we have been focusing on crosstalk between TGF-beta-activated CSCs and their neighboring immune cells. By transcriptomic analysis, we identify interleukin-33 (IL-33) as the most upregulated cytokine in TGF-beta-activated CSCs. We find that IL-33 is secreted in response to the activation of antioxidant responses, and IL-33 mobilizes a subset of tumor-promoting macrophages that express the IL-33 receptor in the adjacent stroma. Tumor-specific IL33 knockdown in vivo dampens both invasive carcinogenesis and paracrine TGF-beta signaling in tumor cells, indicating that IL-33 has a crucial role in the formation of TGF-beta-rich tumor-promoting TME by affecting tumor-infiltrating bone marrow-derived monocytes. Together, these findings on a bidirectional paracrine signaling axis provide novel insights into mechanisms of the formation a CSC privilege niche, which may hold great potential to drastically improve the therapeutic efficacy of current and future cancer treatments. Note: This abstract was not presented at the meeting. Citation Format: Naoki Oshimori, Sachiko Oshimori, Ajit Elhance, Justin Leitenberger, Sushil Kumar. Bidirectional paracrine IL-33-TGF-beta signaling underlies a tumor-promoting stem cell niche [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 2033.

Abstract 1491: Immune resistance emerges from tumor-initiating stem cells

Abstract The remarkable capacity of the long-lived stem cells-like population to self-renew, initiate and propagate a tumor placed these cancer stem cells (CSC) at the root of tumorigenesis. Many unique molecular features of stem cells endow these key population with specialized properties to drive tumor formation. However, in order to achieve these functions, the neoplastic stem cells must first overcome the immune barrier. Although it has long been postulated that, as the core of a tumor, CSCs must be superior at evading the immune detection, direct evidence is still lacking to demonstrate this stem cell trait. Another important feature of CSCs is that these cells are programed to resist traditional cancer treatments, including chemotherapy and radiation. Yet, it is still unexplored how CSCs react to the immunotherapy, which just start to revolutionize the cancer treatments. In order to address these fascinating questions, we have designed a spontaneous skin squamous cell carcinoma (SCC) mouse model that can be effectively targeted by adoptive cell transfer (ACT)-based immunotherapy, without losing the targeted tumor antigen. Employing this model, we have lineage traced the fate of tumor-initiating stem cells during and after ACT treatment. In this study, we will present data demonstrating that a subset of TGFβ-responding CSCs, residing at the tumor-stromal interface, are always able to survive from the injected CD8+ T cell treatment and give rise to the relapsed tumor. Furthermore, the extensive profiling of ACT surviving stem cells revealed that multiple immune resistant pathways are highly up-regulated in these stem cells. In addition, TGFβ appears to orchestrate these immune resistant processes in the tumor-initiating stem cells. This study highlights CSCs as the core to mediate immune evasion. Citation Format: Yuxuan Miao. Immune resistance emerges from tumor-initiating stem cells [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 1491.

The promotion of nanoparticle delivery to two populations of gastric cancer stem cells by CD133 and CD44 antibodies

Gastric cancer which starts from the stomach is a fatal cancer with poor prognosis around the world. The recurrence and metastasis of gastric cancer may be attributed to gastric cancer stem cells. It is recognized that cancer usually possesses multiple populations of distinct cancer stem cells with different phenotypes, thus it will be imperative to target more subsets of cancer stem cells instead of targeting only one population of cancer stem cells. It is generally accepted that both CD44 and CD133 are gastric cancer stem cells markers, we hereby developed CD44/CD133-ATRA-PLPN (CD44 and CD133 antibody-conjugated all-trans retinoic acid-loaded poly(lactide-co-glycolide)-lecithin-PEG nanoparticles) to target both CD133+ and CD44+ gastric cancer stem cells. In this study, the therapeutic effect of CD44/CD133-ATRA-PLPN against gastric cancer stem cells was investigated. The results presented here confirmed that CD44/CD133-ATRA-PLPN was efficiently and specifically delivered to CD44+ or CD133+ gastric cancer stem cells, resulting in enhanced growth inhibitory effect towards gastric cancer stem cells compared with single targeted and non-targeted nanoparticles. As far as we know, we firstly reported the promotion of nanoparticle delivery to two populations of gastric cancer stem cells by antibodies. Since cancer usually contains distinct populations of cancer stem cells with multiple phenotypes, our dual targeting nanoparticles constitute an effective drug delivery platform for targeting multiple populations of cancer stem cells within the cancer.

Superparamagnetic iron oxide nanoparticle-mediated expression of miR-326 inhibits human endometrial carcinoma stem cell growth.

Background: Previously, our group confirmed the presence of a subset of cancer stem cells in the tissues of endometrial carcinoma (ie, human endometrial carcinoma stem cells [HuECSCs]). However, the mechanisms by which microRNAs regulate the growth of HuECSCs remain elusive.Methods: We loaded miR-326 onto superparamagnetic iron oxide nanoparticles (miR-326@SPION) and transfected them into HuECSCs.Results: In the present study, we found that the expression levels of members of the G-protein coupled receptor 91 (GPR91)/signal transducer and activator of transcription 3 (STAT3)/vascular endothelial growth factor (VEGF) pathway were significantly elevated in CD44+/CD133+ HuECSCs. Luciferase reporter assays indicated that the succinate receptor 1 (SUCNR1) gene, also known as the G-protein coupled receptor 91 (GPR91) gene, was one of the potential targets of miR-326. Transmission electron microscopy revealed that the SPIONs could cross the cell membrane and accumulate in the cytoplasm. The overexpression of miR-326 significantly inhibited the proliferation and cell cycle progression of HuECSCs in vitro. MiR-326 overexpression also effectively inhibited the invasion and angiogenic capacities of HuECSCs in the extracellular matrix. Meanwhile, miR-326 overexpression significantly inhibited the tumorigenicity and tumour neovascularization capacity of HuECSCs in nude mice. Both quantitative real-time PCR and Western blotting confirmed that overexpression of miR-326 significantly reduced the expression of members of the GPR91/STAT3/VEGF pathway in HuECSCs, and the activity (level of phosphorylation) of key molecules in this pathway was also reduced.Conclusion: Collectively, we confirmed that SPIONs are highly efficient nanocarriers for nucleic acids, on which the loading of miR-326 inhibited the activation of the GPR91/STAT3/VEGF signaling pathway and significantly attenuated the activity of stem cells in endometrial carcinoma, both in vitro and in vivo.

Surface expression marker profile in colon cancer cell lines and sphere-derived cells suggests complexity in CD26+ cancer stem cells subsets.

ABSTRACTTaking advantage of eight established cell lines from colorectal cancer patients at different stages of the disease and the fact that all of them could form spheres, cell surface biomarkers of cancer stem cells and epithelial-mesenchymal transition were tested. The aim was to investigate cancer stem cells and metastatic stem cells in order to provide functional characterization of circulating tumor cells and promote the development of new anti-metastatic therapies. Our model showed an important heterogeneity in EpCAM, CD133, CD44, LGR5, CD26 and E-cadherin expression. We showed the presence of a subset of E-cadherin+ (some cells being E-cadherinhigh) expressing CD26+ (or CD26high) together with the well-known CSC markers LGR5 and EpCAMhigh, sometimes in the absence of CD44 or CD133. The already described CD26+/E-cadherinlow or negative and CD26+/EpCAM−/CD133− subsets were also present. Cell division drastically affected the expression of all markers, in particular E-cadherin, so new-born cells resembled mesenchymal cells in surface staining. CD26 and/or dipeptidyl peptidase 4 inhibitors have already shown anti-metastatic effects in pre-clinical models, and the existence of these CD26+ subsets may help further research against cancer metastasis.

G-protein-signaling modulator 2 expression and role in a CD133+ pancreatic cancer stem cell subset.

BackgroundTo investigate the expression and role of G-protein-signaling modulator 2 (GPSM2) in a CD133+ pancreatic stem cell subset.Materials and methodsPancreatic cancer stem cells (PCSCs) from the cell line PANC-1 were sorted into CD133+ and CD133− subsets by flow cytometry. The tumorigenic potential of the subsets was assessed by subcutaneous tumor formation experiments in nude mice. Differential expression of GPSM2 was examined by real-time quantitative-PCR (qPCR) and Western blotting. To silence GPSM2 expression, a shRNA lentiviral vector targeting GPSM2 was constructed and stably transfected into CD133+ PCSCs. The inhibitory efficiency of the GPSM2 gene was verified by qPCR and Western blotting. The proliferation, colony formation, and migration abilities of the transfected CD133+ pancreatic cancer cells were assessed by MTT, soft agar colony formation, and Transwell assays.ResultsCD133+ and CD133− cell subsets were successfully isolated from PANC-1 cells. The CD133+ subset subcutaneously formed tumors in nude mice that were significantly bigger (343.05±57.59 mm3 vs 176.86±32.58 mm3, P<0.01) and denser (4.13±0.37 g vs 1.07±0.21 g, P<0.01) than those of the CD133− group. The GPSM2 mRNA and protein expression was significantly higher in CD133+ cells than in CD133− cells. Stable downregulation of GPSM2 expression reduced the proliferation, colony formation, and migration abilities of CD133+ PANC-1 cells (P<0.05).ConclusionThe CD133+PANC-1 cells have obvious stem cell characteristics and increased GPSM2 expression. Downregulation of GPSM2 significantly reduces the proliferation and migration ability of the cells. Therefore, GPSM2 may provide an important target for regulating PCSCs.

Kr\xfcppel-like factor 9 and histone deacetylase inhibitors synergistically induce cell death in glioblastoma stem-like cells

BackgroundThe dismal prognosis of patients with glioblastoma (GBM) is attributed to a rare subset of cancer stem cells that display characteristics of tumor initiation, growth, and resistance to aggressive treatment involving chemotherapy and concomitant radiation. Recent research on the substantial role of epigenetic mechanisms in the pathogenesis of cancers has prompted the investigation of the enzymatic modifications of histone proteins for therapeutic drug targeting. In this work, we have examined the function of Krüppel-like factor 9 (KLF9), a transcription factor, in chemotherapy sensitization to histone deacetylase inhibitors (HDAC inhibitors).MethodsSince GBM neurosphere cultures from patient-derived gliomas are enriched for GBM stem-like cells (GSCs) and form highly invasive and proliferative xenografts that recapitulate the features demonstrated in human patients diagnosed with GBM, we established inducible KLF9 expression systems in these GBM neurosphere cells and investigated cell death in the presence of epigenetic modulators such as histone deacetylase (HDAC) inhibitors.ResultsWe demonstrated that KLF9 expression combined with HDAC inhibitor panobinostat (LBH589) dramatically induced glioma stem cell death via both apoptosis and necroptosis in a synergistic manner. The combination of KLF9 expression and LBH589 treatment affected cell cycle by substantially decreasing the percentage of cells at S-phase. This phenomenon is further corroborated by the upregulation of cell cycle inhibitors p21 and p27. Further, we determined that KLF9 and LBH589 regulated the expression of pro- and anti- apoptotic proteins, suggesting a mechanism that involves the caspase-dependent apoptotic pathway. In addition, we demonstrated that apoptosis and necrosis inhibitors conferred minimal protective effects against cell death, while inhibitors of the necroptosis pathway significantly blocked cell death.ConclusionsOur findings suggest a detailed understanding of how KLF9 expression in cancer cells with epigenetic modulators like HDAC inhibitors may promote synergistic cell death through a mechanism involving both apoptosis and necroptosis that will benefit novel combinatory antitumor strategies to treat malignant brain tumors.

The Antigen ASB4 on Cancer Stem Cells Serves as a Target for CTL Immunotherapy of Colorectal Cancer.

Colorectal cancer consists of a small number of cancer stem cells (CSC) and many non-CSCs. Although rare in number, CSCs are a target for cancer therapy, because they survive conventional chemo- and radiotherapies and perpetuate tumor formation in vivo In this study, we conducted an HLA ligandome analysis to survey HLA-A24 peptides displayed by CSCs and non-CSCs of colorectal cancer. The analysis identified an antigen, ASB4, which was processed and presented by a CSC subset but not by non-CSCs. The ASB4 gene was expressed in CSCs of colorectal cancer, but not in cells that had differentiated into non-CSCs. Because ASB4 was not expressed by normal tissues, its peptide epitope elicited CD8+ cytotoxic T-cell (CTL) responses, which lysed CSCs of colorectal cancer and left non-CSCs intact. Therefore, ASB4 is a tumor-associated antigen that can elicit CTL responses specific to CSCs and can discriminate between two cellular subsets of colorectal cancer. Adoptively transferred CTLs specific for the CSC antigen ASB4 could infiltrate implanted colorectal cancer cell tumors and effectively prevented tumor growth in a mouse model. As the cancer cells implanted in these mice contained very few CSCs, the elimination of a CSC subset could be the condition necessary and sufficient to control tumor formation in vivo These results suggest that CTL-based immunotherapies against colorectal CSCs might be useful for preventing relapses. Cancer Immunol Res; 6(3); 358-69. ©2018 AACR.