Galiellalactone inhibits stem cell-like ALDH-positive prostate cancer cells

Galiellalactone is a potent and specific inhibitor of STAT3 signaling which has been shown to possess growth inhibitory effects on prostate cancer cells expressing active STAT3. In this study we aimed to investigate the effect of galiellalactone on prostate cancer stem cell-like cells. We explored the expression of aldehyde dehydrogenase (ALDH) as a marker for cancer stem cell-like cells in different human prostate cancer cell lines and the effects of galiellalactone on ALDH expressing (ALDH+) prostate cancer cells. ALDH+ subpopulations were detected and isolated from the human prostate cancer cell lines DU145 and long-term IL-6 stimulated LNCaP cells using ALDEFLUOR® assay and flow cytometry. In contrast to ALDH− cells, ALDH+ prostate cancer cells showed cancer stem cell-like characteristics such as increased self-renewing and colony forming capacity and tumorigenicity. In addition, ALDH+ cells showed an increased expression of putative prostate cancer stem cell markers (CD44 and integrin α2β1). Furthermore, ALDH+ cells expressed phosphorylated STAT3. Galiellalactone treatment decreased the proportion of ALDH+ prostate cancer cells and induced apoptosis of ALDH+ cells. The gene expression of ALDH1A1 was downregulated in vivo in galiellalactone treated DU145 xenografts. These findings emphasize that targeting the STAT3 pathway in prostate cancer cells, including prostate cancer stem cell-like cells, is a promising therapeutic approach and that galiellalactone is an interesting compound for the development of future prostate cancer drugs.     

Dexamethasone selectively inhibits differentiation of cord blood stem cell derived-dendritic cell (DC) precursors into immature DCs

Perinatal dexamethasone (Dx) alters the immune system leading to increased infections and developmental abnormalities. Dendritic cells (DCs) derived from cord-blood monocytes are especially Dx sensitive and we sought to determine the effects of Dx on cord-blood CD34+-DCs. Distinct stages of cord-blood CD34+-DC development were delineated: pre-DC, immature, and mature DCs. Dx added during development of pre-DCs did not suppress precursor number, or translocate the glucocorticoid receptor (GcR) from the cytoplasm to the nucleus. However, Dx added during pre-DCs differentiation into immature DCs, prompted GcR translocation to the nucleus, enhanced DC apoptosis, suppressed differentiation to CD1a+ cells, inhibited expression of CD86, reduced subsequent CD83 expression, maintained DC endocytic activity, suppressed IL-6 secretion, enhanced IL-10 secretion, and reduced DC-mediated T cell stimulation. Dx added during the maturation stage caused less dramatic effects. Thus, Dx stalled maturation, selectively induced apoptosis of developing DCs and the sensitivity peaked during pre-DCs differentiation into immature DCs.     

Metformin inhibits RANKL and sensitizes cancer stem cells to denosumab

The increased propensity of BRCA1 mutation carriers to develop aggressive breast tumors with stem-like properties begins to be understood in terms of osteoprotegerin (OPG)-unrestricted cross-talk between RANKL-overproducing progesterone-sensor cells and cancer-initiating RANK⁺ responder cells that reside within pre-malignant BRCA1^mut/+ breast epithelial tissue. We recently proposed that, in the absence of hormone influence, cancer-initiating cells might remain responsive to RANKL stimulation, and hence to the therapeutic effects of the anti-RANKL antibody denosumab because genomic instability induced by BRCA1 haploinsufficiency might suffice to cell-autonomously hyperactivate RANKL gene expression. Here we report that the biguanide metformin prevents BRCA1 haploinsufficiency-driven RANKL gene overexpression, thereby disrupting an auto-regulatory feedback control of RANKL-addicted cancer stem cell-like states within BRCA1^mut/? cell populations. Moreover, metformin treatment elicits a synergistic decline in the breast cancer-initiating cell population and its self-renewal capacity in BRCA1-mutated basal-like breast cancer cells with bone metastasis-initiation capacity that exhibit primary resistance to denosumab in mammosphere assays. The specific targeting of RANKL/RANK signaling with denosumab is expected to revolutionize prevention and treatment strategies currently available for BRCA1 mutation carriers. Our findings provide a rationale for new denosumab/metformin combinatorial strategies to clinically manage RANKL-related breast oncogenesis and metastatic progression.     

Identification of drugs including a dopamine receptor antagonist that selectively target cancer stem cells

Selective targeting of cancer stem cells (CSCs) offers promise for a new generation of therapeutics. However, assays for both human CSCs and normal stem cells that are amenable to robust biological screens are limited. Using a discovery platform that reveals differences between neoplastic and normal human pluripotent stem cells (hPSC), we identify small molecules from libraries of known compounds that induce differentiation to overcome neoplastic self-renewal. Surprisingly, thioridazine, an antipsychotic drug, selectively targets the neoplastic cells, and impairs human somatic CSCs capable of in vivo leukemic disease initiation while having no effect on normal blood SCs. The drug antagonizes dopamine receptors that are expressed on CSCs and on breast cancer cells as well. These results suggest that dopamine receptors may serve as a biomarker for diverse malignancies, demonstrate the utility of using neoplastic hPSCs for identifying CSC-targeting drugs, and provide support for the use of differentiation as a therapeutic strategy.     

Targeting proapoptotic protein BAD inhibits survival and self-renewal of cancer stem cells

Emerging evidence suggests that the resistance of cancer stem cells (CSC) to many conventional therapies is one of the major limiting factors of cancer therapy efficacy. Identification of mechanisms responsible for survival and self-renewal of CSC will help design new therapeutic strategies that target and eliminate both differentiated cancer cells and CSC. Here we demonstrated the potential role of proapoptotic protein BAD in the biology of CSC in melanoma, prostate and breast cancers. We enriched CD44⁺/CD24⁻ cells (CSC) by tumorosphere formation and purified this population by FACS. Both spheres and CSC exhibited increased potential for proliferation, migration, invasion, sphere formation, anchorage-independent growth, as well as upregulation of several stem cell-associated markers. We showed that the phosphorylation of BAD is essential for the survival of CSC. Conversely, ectopic expression of a phosphorylation-deficient mutant BAD induced apoptosis in CSC. This effect was enhanced by treatment with a BH3-mimetic, ABT-737. Both pharmacological agents that inhibit survival kinases and growth factors that are involved in drug resistance delivered their respective cytotoxic and protective effects by modulating the BAD phosphorylation in CSC. Furthermore, the frequency and self-renewal capacity of CSC was significantly reduced by knocking down the BAD expression. Consistent with our in vitro results, significant phosphorylation of BAD was found in CD44⁺ CSC of 83% breast tumor specimens. In addition, we also identified a positive correlation between BAD expression and disease stage in prostate cancer, suggesting a role of BAD in tumor advancement. Our studies unveil the role of BAD in the survival and self-renewal of CSC and propose BAD not only as an attractive target for cancer therapy but also as a marker of tumor progression.Although tumors initially respond positively to anti-cancer agents, several cancers, despite the best care and significant improvements in treatment, recur and progress to advanced stages of the disease. The mechanisms underlying this recurrence and metastasis are not clearly understood. Over the past decade, substantial evidence supported the cancer stem cell (CSC) hypothesis as a viable explanation for the initiation, progression and recurrence of cancer. According to this hypothesis, each tumor harbors a small subpopulation of specialized cells among cellular heterogeneity, known as CSC. These cells exhibit self-renewal property that drives tumorigenesis and plasticity to differentiate into multiple cell types contributing to tumor cellular heterogeneity. Support for this hypothesis came from the studies by Lapidot et al. who identified tumor-initiating cells in acute myeloid leukemia.^{1, 2} Subsequently, CSCs have been identified in several cancers.^{3, 4, 5, 6, 7, 8, 9, 10}Accumulating evidence suggests that current cancer therapies can only shrink tumors as they target and kill the differentiated cancer (DC) cells, but are unable to target the rare CSC population.^{11, 12} Thus, despite a wealth of information on DC cells, the active survival and self-renewal pathways in CSCs have not been characterized thoroughly. An understanding of the molecular mechanisms involved in the survival, self-renewal and resistance of CSCs to current therapeutic regimens is of immense clinical interest. This information will help in developing novel strategies for more effective treatments for cancer.Most anti-cancer drugs exert their effects through triggering the apoptotic pathways. However, malignant cancer cells can escape apoptosis by altering the expression level of proapoptotic and antiapoptotic BCL-2 family members. Considering the potential role of BCL-2 family members in tumorigenesis and cancer cell survival, their role in CSC biology has been increasingly studied.^{13, 14} BAD (BCL2-antagonist of cell death) is a member of the BH3-only BCL-2 family protein that when dephosphorylated promotes apoptosis by heterodimerizing with the antiapoptotic proteins BCL-XL and BCL-2.¹⁵ The cytotoxic effects of BAD are controlled by mechanisms that regulate its phosphorylation on at least two distinct serine residues, S112 and S136.^{16, 17, 18} Previously, we showed that phosphorylation at either site is sufficient to protect prostate cancer cells from apoptosis.^{19, 20, 21} We also showed that BAD promotes prostate tumor growth in mouse models.²² Clinically, while BAD expression was associated with relapse in tamoxifen-treated breast cancer patients,^{23, 24} phospho-BAD expression was associated with cisplatin resistance and poor overall survival in ovarian cancer.²⁵Our previous findings along with other reports showing the role of BAD in the apoptosis modulation and growth of DC cells^{19, 22, 26} prompted us to explore the potential role of BAD in the biology of CSCs. We started our investigation by assessing the role of BAD in survival and self-renewal of CSCs. As we observed a significant role for BAD in CSC''s biology, we extended our work to assess the BAD phosphorylation in CSCs of breast cancer patient tumors and for a potential correlation between BAD expression and disease progression in prostate cancer.     

Isoliquiritigenin (ISL) inhibits ErbB3 signaling in prostate cancer cells

Isoliquiritigenin (ISL), a flavonoid found in licorice, shallot, and bean sprouts, has been identified as a potent anti-tumor promoting agent. We previously demonstrated that ISL reduces cell proliferation and induces apoptosis in DU145 human prostate cancer cells and MAT-LyLu (MLL) rat prostate cancer cells. Overexpression of members of the ErbB receptor family is a frequently observed event in several human cancers, and ErbB receptors currently constitute the primary targets of anticancer strategies. In order to elucidate the mechanisms underlying the ISL regulation of prostate cancer cell proliferation, the present study attempted to determine whether ISL inhibits heregulin (HRG)-beta-induced ErbB3 signaling. DU145 and MLL cells were cultured in serum-free medium with ISL and/or HRG-beta. Exogenous HRG-beta alone was shown to effect an increase in the numbers of viable cells, whereas HRG-beta did not counteract the ISL-induced growth inhibition. ISL reduced the protein and mRNA levels of ErbB3 in a dose-dependent manner, but exerted no effect on HRG protein levels. Immunoprecipitation/Western blot studies indicated that ISL inhibited the HRG-beta-induced tyrosine phosphorylation of ErbB3, the recruitment of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3K) to ErbB3, and Akt phosphorylation in DU145 cells. These results indicate that ISL inhibits the proliferation of prostate cancer cells, at least in part, via the inhibition of ErbB3 signaling and the PI3K/Akt pathway.     

Induced pluripotent stem (iPS) cells from human fetal stem cells (hFSCs)

Introduction

(1) Human embryonic stem (ES) cells are pluripotent but are difficult to be used for therapy because of immunological, oncological and ethical barriers. (2) Pluripotent cells exist in vivo, i.e., germ cells and epiblast cells but cannot be isolated without sacrificing the developing embryo. (3) Reprogramming to pluripotency is possible from adult cells using ectopic expression of OKSM and other integrative and non-integrative techniques. (4) Hurdles to overcome include i.e stability of the phenotype in relation to epigenetic memory.

Sources of data

We reviewed the literature related to reprogramming, pluripotency and fetal stem cells.

Areas of agreement

(1) Fetal stem cells present some advantageous characteristics compared with their neonatal and postnatal counterparts, with regards to cell size, growth kinetics, and differentiation potential, as well as in vivo tissue repair capacity. (2) Amniotic fluid stem cells are more easily reprogrammed to pluripotency than adult fibroblast. (3) The parental population is heterogeneous and present an intermediate phenotype between ES and adult somatic stem cells, expressing markers of both.

Areas of controversy

(1) It is unclear whether induced pluripotent stem (iPS) derived from amniotic fluid stem cells are fully or partially reprogrammed. (2) Optimal protocols to ensure highest efficiency and phenotype stability remains to be determined. (3) The “level” of reprogramming, fully vs partial, of iPS derived from amniotic fluid stem cells remain to be determined.

Growing points

Banking of fully reprogrammed cells may be important both for (1) autologous and allogenic applications in medicine, and (2) disease modeling.     

The curry spice curcumin selectively inhibits cancer cells growth in vitro and in preclinical model of glioblastoma

Previous studies suggested that curcumin is a potential agent against glioblastomas (GBMs). However, the in vivo efficacy of curcumin in gliomas remains not established. In this work, we examined the mechanisms underlying apoptosis, selectivity, efficacy and safety of curcumin from in vitro (U138MG, U87, U373 and C6 cell lines) and in vivo (C6 implants) models of GBM. In vitro, curcumin markedly inhibited proliferation and migration and induced cell death in liquid and soft agar models of GBM growth. Curcumin effects occurred irrespective of the p53 and PTEN mutational status of the cells. Interestingly, curcumin did not affect viability of primary astrocytes, suggesting that curcumin selectivity targeted transformed cells. In U138MG and C6 cells, curcumin decreased the constitutive activation of PI3K/Akt and NFkappaB survival pathways, down-regulated the antiapoptotic NFkappaB-regulated protein bcl-xl and induced mitochondrial dysfunction as a prelude to apoptosis. Cells developed an early G2/M cell cycle arrest followed by sub-G1 apoptosis and apoptotic bodies formation. Caspase-3 activation occurred in the p53-normal cell type C6, but not in the p53-mutant U138MG. Besides its apoptotic effect, curcumin also synergized with the chemotherapeutics cisplatin and doxorubicin to enhance GBM cells death. In C6-implanted rats, intraperitoneal curcumin (50 mg kg(-1) d(-1)) decreased brain tumors in 9/11 (81.8%) animals against 0/11 (0%) in the vehicle-treated group. Importantly, no evidence of tissue (transaminases, creatinine and alkaline phosphatase), metabolic (cholesterol and glucose), oxidative or hematological toxicity was observed. In summary, data presented here suggest curcumin as a potential agent for therapy of GBMs.     

Relationships between stem cells and cancer stem cells

Stem cells have been shown to exist in a variety of tissues. Recent studies have characterized stem cell gene expression patterns, phenotypes, and potential therapeutic uses. One of the most important properties of stem cells is that of self renewal. This raises the possibility that some of the clinical properties of human tumors may be due to transformed stem cells. Similar signaling pathways may regulate self renewal in normal and transformed stem cells. These rare transformed stem cells may drive the process of tumorigenesis due to their potential for self renewal. There are important ramifications for clinical cancer treatment if the growth of solid tumors is at least partially dependent on a cancer stem cell population. In the cancer stem cell model, tumor recurrence may be due to the non-targeted stem cell compartment repopulating the tumor. If cancer stem cells can be prospectively identified and isolated, it should be possible to identify therapies that will selectively target these cells.     

MicroRNAs,stem cells and cancer stem cells

This review discusses the various regulatory charac-teristics of microRNAs that are capable of generating widespread changes in gene expression via post translational repression of many mRNA targets and control self-renewal, differentiation and division of cells. It controls the stem cell functions by controlling a wide range of pathological and physiological processes, including development, differentiation, cellular proliferation, programmed cell death, oncogenesis and metastasis. Through either mRNA cleavage or translational repression, miRNAs alter the expression of their cognate target genes; thereby modulating cellular pathways that affect the normal functions of stem cells, turning them into cancer stem cells, a likely cause of relapse in cancer patients. This present review further emphasizes the recent discoveries on the functional analysis of miRNAs in cancer metastasis and implications on miRNA based therapy using miRNA replacement or anti-miRNA technologies in specific cancer stem cells that are required to establish their efficacy in controlling tumorigenic potential and safe therapeutics.     

A trans-platinum(II) complex induces apoptosis in cancer stem cells of breast cancer

Recent accumulating evidence has supported the notion that tumors have hierarchically organized heterogeneous cell populations and a small subpopulation of cells, termed cancer stem cells (CSCs), are responsible for tumor initiation, maintenance as well as drug resistance. Therefore, targeting the CSCs along with the other cancer cells has been the most important topic during the last decade. In the present study, we evaluated the cytotoxic activity of trans-[PtCl₂(2-hepy)₂] [2-hepy = 2-(2-hydroxyethyl) pyridine] complex and the mechanism of cell death in breast CSCs. Stemness markers, Oct-4 and Sox2, were determined in mammospheres by western blotting. Cytotoxicity was assessed using the ATP viability assay. Cell death was fluorescently visualized and further confirmed by flow cytometry as well as gene expression analysis. The Pt(II) complex significantly reduced the cell viability, prevented mammosphere formation and disrupted mammosphere structures in a dose-dependent manner (0–100 μM). The mode of cell death was apoptosis and it was shown by the presence of caspase 3/7 activity, Annexin V-FITC positivity, decreased mitochondrial membrane potential and increased expressions of pro-apoptotic genes (TNFRSF10A and HRK). Interestingly, necroptosis was also observed by the evidence of increased MLKL expression. In conclusion, the Pt(II) complex seems to be a highly promising anticancer compound due to its promising cytotoxic activity on CSCs. Therefore, it deserves in vivo further studies for the proof-of-concept.     

(Re)defining stem cells

Stem-cell nomenclature is in a muddle! So-called stem cells may be self-renewing or emergent, oligopotent (uni- and multipotent) or pluri- and totipotent, cells with perpetual embryonic features or cells that have changed irreversibly. Ambiguity probably seeped into stem cells from common usage, flukes in biology's history beginning with Weismann's divide between germ and soma and Haeckel's biogenic law and ending with contemporary issues over the therapeutic efficacy of adult versus embryonic cells. Confusion centers on tissue dynamics, whether stem cells are properly members of emerging or steady-state populations. Clarity might yet be achieved by codifying differences between cells in emergent populations, including embryonic stem and embryonic germ (ES and EG) cells in tissue culture as opposed to self-renewing (SR) cells in steady-state populations.     

Secondary metabolites from acridocarpus orientalis inhibits 4T1 cells and promotes mesenchymal stem cells (MSCs) proliferation

Molecular Biology Reports - Among medicinal plants, Acridocarpus orientalis (AO) possesses a remarkable anti-cancer potential, possibly because of its anti-oxidant property. In this study, the leaf...     

Membrane depolarization selectively inhibits receptor-operated calcium channels in human T (Jurkat) lymphoblasts

Jurkat lymphoblasts were stimulated by a monoclonal antibody against the CD3 membrane antigen and the evoked calcium signal was followed by the intracellular fluorescent calcium indicator indo-1. The technique applied allowed us to separately investigate the stimulus-induced intracellular calcium release and the calcium-influx pathways, respectively. In the same cells membrane potential was estimated by the fluorescent dye diS-C3-(5). The resting membrane potential of Jurkat lymphoblasts under normal conditions was between -55 and -60 mV. Membrane depolarization, obtained by increasing external K+ concentration, removing external Cl-, or by increasing the Na+/K+ leak permeability with gramicidin or PCMBS, did not induce calcium influx in the resting cells and did not influence the CD3 receptor-mediated internal calcium release, while strongly inhibited the receptor-mediated calcium influx pathway. Half-maximum inhibition of this calcium influx was observed at membrane potential values of about -35 to -40 mV and this inhibition did not depend on the external calcium concentration varied between 5 and 2500 microM. Membrane hyperpolarization by valinomycin did not affect either component of the calcium signal. The observed selective inhibition of the receptor-operated calcium influx pathway by membrane depolarization is probably an important modulator of calcium-dependent cell stimulation.     

Novel non-trimethoxylphenyl piperlongumine derivatives selectively kill cancer cells

Piperlongumine (PL) is a natural alkaloid with broad biological activities. Twelve analogues have been designed and synthesized with non-substituted benzyl rings or heterocycles in this work. Most of the compounds showed better anticancer activities than the parent PL without apparent toxicity in normal cells. Elevation of cellular ROS levels was one of the main anticancer mechanisms of these compounds. Cell apoptosis and cell cycle arrest for the best compound ZM90 were evaluated and similar mechanism of action with PL was demonstrated. The SAR was also characterized, providing worthy directions for further optimization of PL compounds.     

Cervical cancer stem cells

The concept of cancer stem cells (CSC) has been established over the past decade or so, and their role in carcinogenic processes has been confirmed. In this review, we focus on cervical CSCs, including (1) their purported origin, (2) markers used for cervical CSC identification, (3) alterations to signalling pathways in cervical cancer and (4) the cancer stem cell niche. Although cervical CSCs have not yet been definitively identified and characterized, future studies pursuing them as therapeutic targets may provide novel insights for treatment of cervical cancer.