Apoptosis In Cancer Stem-like Cells Research Articles

Targeting c-Myc with decoy oligodeoxynucleotide-loaded polycationic nanoparticles inhibits cell growth and induces apoptosis in cancer stem-like cells (NTERA-2).

Anincreaseincancerstemcell(CSC)populations and their resistance tocommontreatmentscouldbearesultofc-Myc dysregulationsincertain cancer cells. In the current study, we investigated anticancer effects of c-Myc decoy ODNs loaded-poly (methacrylic acid-co-diallyl dimethyl ammonium chloride) (PMA-DDA)-coated silica nanoparticles as carriers on cancer-like stem cells (NTERA-2). The physicochemical characteristics of the synthesized nanocomposites (SiO2@PMA-DDA-DEC) were analyzed using FT-IR, DLS, and SEM techniques. UV-Vis spectrophotometer was applied to analyze the release pattern of decoy ODNs from the nanocomposite. Furthermore, uptake, cell viability, apoptosis, and cell cycle assays were used to investigate the anticancer effects of nanocomposites loaded with c-Myc decoy ODNs on NTERA-2 cancer cells. The results of physicochemical analytics demonstrated that SiO2@PMA-DDA-DEC nanocomposites were successfully synthesized. The prepared nanocomposites were taken up by NTERA-2 cells with high efficiency, and could effectively inhibit cell growth and increase apoptosis rate in the treated cells compared to the control group. Moreover, SiO2@PMA-DDA nanocomposites loaded with c-Myc decoy ODNs induced cell cycle arrest at the G0/G1 phase in the treated cells. The conclusion drawn from this study is that c-Myc decoy ODN-loaded SiO2@PMA-DDA nanocomposites can effectively inhibit cell growth and induce apoptosis in NTERA-2 cancer cells. Moreover, given that a metal core is incorporated into this synthetic nanocomposite, it could potentially be used in conjunction with irradiation as part of a decoy-radiotherapy combinational therapy in future investigations.

Chelerythrine Chloride Inhibits Stemness of Melanoma Cancer Stem-Like Cells (CSCs) Potentially via Inducing Reactive Oxygen Species and Causing Mitochondria Dysfunction.

Growing evidence has demonstrated that high heterogeneity contributes to poor prognosis and malignancies. The existence of melanoma cancer stem-like cells (CSCs), which are a small subpopulation of melanoma cells, is responsible for tumour resistance to therapies. Recently, plant secondary metabolites have attracted attention because they are considered promising compounds that are isolated from herbs that could help to target different subpopulations of tumours. In the present study, we aimed to identify the antitumourigenic activities of the medicinal compound chelerythrine chloride (CHE) on melanoma CSCs. CHE (30-40 μmol/L) induced apoptosis in A375 and A2058 CSCs. A relatively low dose of CHE (1-5 μmol/L) inhibited the stemness of melanoma CSCs without inducing apoptosis. Coculture of CHE with A375 and A2058 cells also inhibited sphere formation and decreased stemness factors, including Nanog, Oct4, and Sox2. In functional characterizations, we observed that CHE treatment increased both cellular reactive oxygen species (ROS) and mitochondrial ROS, which resulted in a decrease in mitochondrial energy production and sphere formation. Abolishing CHE-induced ROS by N-acetyl-L-cysteine (NAC), a ROS scavenger, reversed the inhibitory effects of CHE on sphere formation, suggesting that CHE-induced ROS are the potential cause of the inhibition of sphere formation. In conclusion, CHE may exert its antitumour effect as an antistem cell natural compound, suggesting that selection of the antistem cell effects of natural compounds might be a promising strategy to overcome the poor prognosis of melanoma due to the presence of CSCs.

Lumiflavin Enhances the Effects of Ionising Radiation on Ovarian Cancer Stem-Like Cells by Inhibiting Autophagy.

The development of Cancer Stem-like Cells (CSCs) is one of the main causes of ovarian cancer tolerance to radiotherapy. Autophagy is an adaptive process by which cells damage due to radiation. As a metabolite of riboflavin, lumiflavin can enhance the chemotherapeutic effects of cisplatin on ovarian cancer CSCs. This study aimed to investigate the synergistic effects of lumiflavin and ionising radiation on ovarian cancer CSCs and explore the association of this metabolite with autophagy. CSCs of human ovarian cancer cell lines HO8910 were treated with lumiflavin and rapamycin and then subjected to irradiation at a cumulative dose of 8 Gy. Cell proliferation ability, clonal formation ability, apoptosis rate, autophagy changes and autophagy-related protein changes were detected. Lumiflavin and ionising radiation synergistically reduced cell vitality and clone formation and increased the apoptosis of CSCs compared with irradiation alone. In addition, ionising radiation increased autophagy and the expression of associated proteins, whereas lumiflavin reduced those changes in autophagy progression. Moreover, rapamycin, an autophagy inhibitor, was observed to block the synergistic effects of lumiflavin and ionising radiation on CSC apoptosis. Lumiflavin can enhance the effects of ionising radiation on ovarian cancer CSCs. The mechanism by which these effects are exerted is related to blocking the autophagy pathway.

Survival of salivary gland cancer stem cells requires mTOR signaling

Advanced salivary gland mucoepidermoid carcinoma (MEC) is a relentless cancer that exhibits resistance to conventional chemotherapy. As such, treatment for patients with advanced MEC is tipically radical surgery and radiotherapy. Facial disfigurement and poor quality of life are frequent treatment challenges, and many patients succumb to loco-regional recurrence and/or metastasis. We know that cancer stem-like cells (CSC) drive MEC tumorigenesis. The current study tests the hypothesis that MEC CSC are sensitive to therapeutic inhibition of mTOR. Here, we report a correlation between the long-term clinical outcomes of 17 MEC patients and the intratumoral expression of p-mTOR (p = 0.00294) and p-S6K1 (p = 0.00357). In vitro, we observed that MEC CSC exhibit constitutive activation of the mTOR signaling pathway (i.e., mTOR, AKT, and S6K1), unveiling a potential strategy for targeted ablation of these cells. Using a panel of inhibitors of the mTOR pathway, i.e., rapamycin and temsirolimus (mTOR inhibitors), buparlisib and LY294002 (AKT inhibitors), and PF4708671 (S6K1 inhibitor), we observed consistently dose-dependent decrease in the fraction of CSC, as well as inhibition of secondary sphere formation and self-renewal in three human MEC cell lines (UM-HMC-1,-3A,-3B). Notably, therapeutic inhibition of mTOR with rapamycin or temsirolimus induced preferential apoptosis of CSC, when compared to bulk tumor cells. In contrast, conventional chemotherapeutic drugs (cisplatin, paclitaxel) induced preferential apoptosis of bulk tumor cells and accumulation of CSC. In vivo, therapeutic inhibition of mTOR with temsirolimus caused ablation of CSC and downregulation of Bmi-1 expression (major inducer of stem cell self-renewal) in MEC xenografts. Transplantation of MEC cells genetically silenced for mTOR into immunodeficient mice corroborated the results obtained with temsirolimus. Collectively, these data demonstrated that mTOR signaling is required for CSC survival, and unveiled the therapeutic potential of targeting the mTOR pathway for elimination of highly tumorigenic cancer stem-like cells in salivary gland mucoepidermoid carcinoma.

Pinostrobin inhibits proliferation and induces apoptosis in cancer stem-like cells through a reactive oxygen species-dependent mechanism.

Current treatments and targeted therapies for malignancies are limited due to their severe toxicity and the development of resistance against such treatments, which leads to relapse. Past evidence has indicated that a number of plant-derived dietary agents possess biological activity against highly tumorigenic and resistant cell populations associated with cancer relapse. These subpopulations, termed cancer stem-like cells (CSCs), have been targeted with plant-derived dietary flavonoids. The present study was undertaken to assess the anti-proliferative potential of pinostrobin, a dietary flavonoid, against CSCs. Sphere-forming cells were developed from HeLa cell lines using specific culture conditions. The existence of a CSC population was confirmed by the morphological examination and analysis of surface markers using confocal microscopy and flow cytometry. The effect of pinostrobin on the cell viability of the CSC population, evaluated through MTT reduction assays and the expression levels of surface markers (CD44+ and CD24+), was studied through various biological assays. HeLa-derived CSCs showed higher CD44+ and lower CD24+ expression. Pinostrobin inhibited the self-renewal capacity and sphere formation efficiency of CSCs in a dose-dependent manner. Increased ROS production, and decreased mitochondrial membrane potential and CD44+ expression indicated that pinostrobin promoted ROS-mediated apoptosis in CSCs. These results thus demonstrate the therapeutic potential and effectiveness of pinostrobin in the chemoprevention and relapse of cancer by targeting the CSC population. Thus, pinostrobin, in combination with currently available chemo and radiation therapies, could possibly be used as a safe strategy to alleviate adverse treatment effects, together with enhancing the efficacy.

Aspirin cooperates with p300 to activate the acetylation of H3K9 and promote FasL-mediated apoptosis of cancer stem-like cells in colorectal cancer

Cancer stem-like cells (CSCs) have been proposed as a key driving force of tumor growth and relapse in colorectal cancer (CRC), and therefore, they are promising targets for cancer therapy. Epidemiological evidence has suggested that the daily use of aspirin reduces overall mortality of CRC and the risk of distant metastasis. We investigated the effect and mechanism of aspirin on CSCs in CRC.Methods: The ratio of CSCs was analyzed after aspirin treatment both in a cell model and patient samples. Chemically modified aspirin and immunoprecipitation were adopted to detect the target proteins of aspirin. A locus-specific light-inducible epigenetic modification system based on CRISPR technology was constructed to verify the causal relationship in these molecular events. In vivo characterization was performed in a xenograft model.Results: We found that aspirin induces apoptosis in enriched colorectal CSCs, inhibits tumor progression, and enhances the anti-neoplastic effects of chemotherapeutic agents. Furthermore, aspirin directly interacts with p300 in the nucleus, promotes H3K9 acetylation, activates FasL expression, and induces apoptosis in colorectal CSCs. Notably, these effects of aspirin are absent in non-CSCs since H3K9 is hypermethylated in non-CSCs and the effects are not induced by other NSAIDs. In addition, aspirin can suppress oxaliplatin-enriched CSCs and serve as an adjuvant therapy.Conclusions: Taken together, we revealed a unique epigenetic and cox-independent pathway (p300-AcH3K9-FasL axis) by which aspirin eliminates colorectal CSCs. These findings establish an innovative framework of the therapeutic significance of aspirin.

Selenium suppresses leukemia through the action of endogenous eicosanoids.

Eradicating cancer stem-like cells (CSC) may be essential to fully eradicate cancer. Metabolic changes in CSC could hold a key to their targeting. Here, we report that the dietary micronutrient selenium can trigger apoptosis of CSC derived from chronic or acute myelogenous leukemias when administered at supraphysiologic but nontoxic doses. In leukemia CSC, selenium treatment activated ATM-p53-dependent apoptosis accompanied by increased intracellular levels of reactive oxygen species. Importantly, the same treatment did not trigger apoptosis in hematopoietic stem cells. Serial transplantation studies with BCR-ABL-expressing CSC revealed that the selenium status in mice was a key determinant of CSC survival. Selenium action relied upon the endogenous production of the cyclooxygenase-derived prostaglandins Δ(12)-PGJ2 and 15d-PGJ2. Accordingly, nonsteroidal anti-inflammatory drugs and NADPH oxidase inhibitors abrogated the ability of selenium to trigger apoptosis in leukemia CSC. Our results reveal how selenium-dependent modulation of arachidonic acid metabolism can be directed to trigger apoptosis of primary human and murine CSC in leukemia.

Correction: A Novel Berbamine Derivative Inhibits Cell Viability and Induces Apoptosis in Cancer Stem-Like Cells of Human Glioblastoma, via Up-Regulation of miRNA-4284 and JNK/AP-1 Signaling

Correction: A Novel Berbamine Derivative Inhibits Cell Viability and Induces Apoptosis in Cancer Stem-Like Cells of Human Glioblastoma, via Up-Regulation of miRNA-4284 and JNK/AP-1 Signaling

A novel berbamine derivative inhibits cell viability and induces apoptosis in cancer stem-like cells of human glioblastoma, via up-regulation of miRNA-4284 and JNK/AP-1 signaling.

Glioblastoma (GBM) is the most common primary brain tumor, accounting for approximately 40% of all central nervous system malignancies. Despite standard treatment consisting of surgical resection, radiotherapy and/or chemotherapy, the prognosis for GBM is poor; with a median survival of 14.6 months. The cancer stem cell or cancer-initiating cell model has provided a new paradigm for understanding development and recurrence of GBM following treatment. Berbamine (BBM) is a natural compound derived from the Berberis amurensis plant, and along with its derivatives, has been shown to exhibit antitumor activity in several cancers. Here, we reported that a novel synthetic Berbamine derivative, BBMD3, inhibits cell viability and induces apoptosis of cancer stem-like cells (CSCs) in a time- and dose-dependent manner when the CSCs from four GBM patients (PBT003, PBT008, PBT022, and PBT030) were cultured. These CSCs grew in neurospheres and expressed CD133 and nestin as markers. Treatment with BBMD3 destroyed the neurosphere morphology, and led to the induction of apoptosis in the CSCs. Induction of apoptosis in these CSCs is dependent upon activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase (PARP). MicroRNA-4284 (miR-4284) was shown to be over-expressed about 4-fold in the CSCs following BBMD3 treatment. Furthermore, transfection of synthetic anti-sense oligonucleotide against human miR-4284 partially blocked the anticancer effects of BBMD3 on the GBM derived CSCs. BBMD3 also increased phosphorylation of the c-Jun N-terminal kinase (JNK)/stress-activated protein kinase (SAPK), resulting in an increase expression of phosphorylated c-Jun and total c-Fos; the major components of transcriptional factor AP-1. The JNK-c-Jun/AP-1 signaling pathway plays an important role in the induction of apoptosis in response to UV irradiation and some drug treatments. Targeting glioblastoma stem-like cells with BBMD3 is therefore novel, and may have promise as an effective therapeutic strategy for treating GBM patients.

LGR5 is a Marker of Poor Prognosis in Glioblastoma and is Required for Survival of Brain Cancer Stem‐Like Cells

In various types of cancers including glioblastoma, accumulating evidence show the existence of cancer stem-like cells (CSCs), characterized by stem cell marker expression, capability of differentiation and self-renewal, and high potential for tumor propagation in vivo. LGR5, whose expression is positively regulated by the Wnt signaling pathway, is a stem cell marker in intestinal mucosa and hair follicle in the skin. As Wnt signaling is also involved in brain development, the function of LGR5 in the maintenance of brain CSCs is to be assessed. Our study showed that the LGR5 transcript level was increased in CSCs. Co-immunofluorescence staining demonstrated the co-localization of CD133- and LGR5-positive cells in glioblastoma tissue sections. Functionally, silencing of LGR5 by lentiviral shRNA-mediated knockdown induced apoptosis in brain CSCs. Moreover, LGR5 depletion led to a downregulation of L1 cell adhesion molecule expression. In line with an important function in glioma tumorigenesis, LGR5 expression increased with glioma progression and correlated with an adverse outcome. Our findings suggest that LGR5 plays a role in maintenance and/or survival of brain CSCs.

LY294002 Induces G0/G1 Cell Cycle Arrest and Apoptosis of Cancer Stem-like Cells from Human Osteosarcoma Via Down-regulation of PI3K Activity

Osteosarcoma, the most common primary mesenchymal malignant tumor, usually has bad prognosis in man, with cancer stem-like cells (CSCs) considered to play a critical role in tumorigenesis and drug-resistance. It is known that phosphatidylinositol 3-kinase (PI3K) is involved in regulation of tumor cell fates, such as proliferation, cell cycling, survival and apoptosis. Whether and how PI3K and inhibitors might cooperate in human osteosarcoma CSCs is still unknown. We therefore evaluated the effects of LY294002, a PI3K inhibitor, on the cell cycle and apoptosis of osteosarcoma CSCs in vitro. LY294002 prevented phosphorylation of protein kinase B (PKB/Akt) by inhibition of PI3K phosphorylation activity, thereby inducing G0/G1 cell cycle arrest and apoptosis in osteosarcoma CSCs. Further studies also demonstrated that apoptosis induction by LY294002 is accompanied by activation of caspase-9, caspase-3 and PARP, which are involved in the mitochondrial apoptosis pathway. Therefore, our results indicate PI3K inhibitors may represent a potential strategy for managing human osteosarcoma via affecting CSCs.

COX-2 regulates the proliferation of glioma stem like cells

Cancer stem-like cells (CSCs) possessing features of neural precursor cells (NPC) influence initiation, recurrence and chemoresistance of glioblastoma multiforme (GBM). As inflammation is crucial for glioblastoma progression we investigated the effect of chronic IL-1β treatment on CSCs derived from glioblastoma cell line U87MG. Exposure to IL-1β for 10days increased (i) accumulation of 8-OHdG – a key biomarker of oxidative DNA damage; (ii) DNA damage response (DDR) indicators γH2AX, ATM and DNA-PK; (iii) nuclear and cytoplasmic p53 and COX-2 levels and (iv) interaction between COX-2 and p53. Despite upregulating p53 expression IL-1β had no effect on cell cycle progression, apoptosis or self renewal capacity of CSCs. COX-2 inhibitor Celecoxib reduced self renewal capacity and increased apoptosis of both control and IL-1β treated CSCs. Therefore the ability of COX-2 to regulate proliferation of CSCs irrespective of exposure to IL-1β, warrants further investigation of COX-2 as a potential anti-glioma target.

Resveratrol suppresses growth of cancer stem-like cells by inhibiting fatty acid synthase

Resveratrol is a natural polyphenolic compound and has been shown to exhibit cardio-protective as well as anti-neoplastic effects on various types of cancers. However, the exact mechanism of its anti-tumor effect is not clearly defined. Resveratrol has been shown to have strong hypolipidemic effect on normal adipocytes and as hyper-lipogenesis is a hallmark of cancer cell physiology, the effect of resveratrol on lipid synthesis in cancer stem-like cells (CD24(-)/CD44(+)/ESA(+)) that were isolated from both ER+ and ER- breast cancer cell lines was examined. The authors found that resveratrol significantly reduced the cell viability and mammosphere formation followed by inducing apoptosis in cancer stem-like cells. This inhibitory effect of resveratrol is accompanied by a significant reduction in lipid synthesis which is caused by the down-regulation of the fatty acid synthase (FAS) gene followed by up-regulation of pro-apoptotic genes, DAPK2 and BNIP3. The activation of apoptotic pathway in the cancer stem-like cells was suppressed by TOFA and by Fumonisin B1, suggesting that resveratrol-induced apoptosis is indeed through the modulation of FAS-mediated cell survival signaling. Importantly, resveratrol was able to significantly suppress the growth of cancer stem-like cells in an animal model of xenograft without showing apparental toxicity. Taken together, the results of this study indicate that resveratrol is capable of inducing apoptosis in the cancer stem-like cells through suppression of lipogenesis by modulating FAS expression, which highlights a novel mechanism of anti-tumor effect of resveratrol.