Combination of Histone Deacetylase Inhibitor with Cu(II) 5,5-diethylbarbiturate Complex Induces Apoptosis in Breast Cancer Stem Cells: A Promising Novel Approach.

BACKGROUND: Cancer Stem Cells (CSCs) are a subpopulation within the tumor that play a role in the initiation, progression, recurrence, resistance to drugs and metastasis of cancer. It is well known that epigenetic changes lead to tumor formation in cancer stem cells and show drug resistance. Epigenetic modulators and /or their combination with different agents have been used in cancer therapy. OBJECTIVE: In our study, we scope out the effects of a combination of a histone deacetylases inhibitor, Valproic Acid (VPA), and Cu(II) complex [Cu(barb-κN)(barb-κ2N,O)(phen-κN,N')]·H2O] on cytotoxicity/apoptosis in a stem-cell enriched population (MCF-7s) obtained from parental breast cancer cell line (MCF-7). METHODS: The viability of the cells was measured by the ATP assay. Apoptosis was elucidated via the assessment of caspase-cleaved cytokeratin 18 (M30 ELISA) and a group of flow cytometry analysis (caspase 3/7 activity, phosphatidylserine translocation by annexin V-FITC assay, DNA damage and oxidative stress) and 2',7'- dichlorofluorescein diacetate staining. RESULTS: The VPA combined with Cu(II) complex showed anti-proliferative activity on MCF-7s cells in a doseand time-dependent manner. Treatment with a combination of 2.5 mM VPA and 3.12 µM Cu(II) complex induced oxidative stress in a time-dependent manner, as well as apoptosis evidenced by the increase in caspase 3/7 activity, positive annexin-V-FITC, and increase in M30 levels. CONCLUSION: The results suggest that the combination therapy induces apoptosis following increased oxidative stress, thereby making it a possible promising therapeutic strategy for which further analysis is required.

A promising therapeutic combination for metastatic prostate cancer: Chloroquine as autophagy inhibitor and palladium(II) barbiturate complex.

Autophagy is a catabolic process for cells that can provide energy sources and allows cancer cells to evade cell death. Therefore, studies on the combination of autophagy inhibitors with drugs are increasing as a new treatment modality in cancer. Previously, we reported the anti-tumor activity of a Palladium (Pd)(II) complex against different types of cancer in vitro and in vivo. Chloroquine (CQ), the worldwide used anti-malarial drug, has recently been focused as a chemosensitizer in cancer treatment. The aim of this study was to investigate the efficacy of a combined treatment of these agents that work through different mechanisms to provide an effective treatment modality for metastatic prostate cancer that is certainly fatal. Metastatic prostate cancer cell lines (PC-3 and LNCaP) were treated with Pd (II) complex, CQ, and their combination. The combination enhanced apoptosis by increasing phosphatidylserine translocation and pro-apoptotic proteins. Apoptosis was confirmed by the use of apoptosis inhibitor. The formation of acidic vesicular organelles (AVOs) was observed by acridine orange staining in fluorescence microscopy. The Pd (II) complex increased AVOs formation in prostate cancer cells and CQ-pretreatment has potentiated this effect. Importantly, treatment with CQ suppressed the pro-survival function of autophagy, which might have contributed to enhanced cytotoxicity. In addition, PI3K/AKT/mTOR-related protein expressions were altered after the combination of treatments. Our results suggest that combination treatment enhances apoptotic cell death possibly via the inhibition of autophagy, and may therefore be regarded as a novel and better approach for the treatment of metastatic prostate cancer.

Toxicity assessment of Hypericum olympicum subsp. olympicum L. on human lymphocytes and breast cancer cell lines.

There is a limited number of studies about the constituents of Hypericum olympicum subsp. olympicum and its genotoxic and cytotoxic potency. We examined the possible antigenotoxic/genotoxic properties of methanolic extract of H. olympicum subsp. olympicum (HOE) on human lymphocytes by employing sister chromatid exchange, micronucleus and comet assay and analyzed its chemical composition by GCxGC-TOF/MS. The anti-growth activity against MCF-7 and MDA-MB-231 cell lines was assessed by using the ATP viability assay. Cell death mode was investigated with fluorescence staining and ELISA assays. The major components of the flower and trunk were determined as eicosane, heptacosane, 2-propen-1-ol, hexahydrofarnesyl acetone and α-muurolene. HOE caused significant DNA damage at selected doses (250-750 µg/ml) while chromosomal damage was observed at higher concentrations (500 and 750 µg/ml). HOE demonstrated anti-growth activity in a dose-dependent manner between 3.13-100 µg/ml. Pyknotic nuclei were observed at 100 µg/ml concentration of HOE in both cell lines. In conclusion, HOE demonstrated cytotoxic effects in a cell type-dependent manner, however its genotoxic effects were observed at relatively higher doses.

Key actors in cancer therapy: epigenetic modifiers.

Epigenetic reprogramming plays a crucial role in the tumorigenicity and maintenance of tumor-specific gene expression that especially occurs through DNA methylation and/or histone modifications. It has well-defined mechanisms. It is known that alterations in the DNA methylation pattern and/or the loss of specific histone acetylation/methylation markers are related to several hallmarks of cancer, such as drug resistance, stemness, epithelial-mesenchymal transition, and metastasis. It has also recently been highlighted that epigenetic alterations are critical for the regulation of the stemlike properties of cancer cells (tumor-initiating cells; cancer stem cells). Cancer stem cells are thought to be responsible for the recurrence of cancer which makes the patient return to the clinic with metastatic tumor tissue. Hence, the dysregulation of epigenetic machinery represents potential new therapeutic targets. Therefore, compounds with epigenetic activities have become crucial for developing new therapy regimens (e.g., antimetastatic agents) in the fight against cancer. Here, we review the epigenetic modifiers that have already been used in the clinic and/or in clinical trials, related preclinical studies in cancer therapy, and the smart combination strategies that target cancer stem cells along with the other cancer cells. The emerging role of epitranscriptome (RNA epigenetic) in cancer therapy has also been included in this review as a new avenue and potential target for the better management of cancer-beneficial epigenetic machinery.

Paclitaxel resistance and the role of miRNAs in prostate cancer cell lines.

PURPOSE: To investigate the expression profiles of 86 miRNAs in paclitaxel-resistant prostate cancer cell lines and to identify the genes that have a role in the development of drug resistance. METHODS: Three prostate cancer cell lines, androgen-dependent VCaP, androgen-independent PC-3 and DU-145, were used to obtain paclitaxel-resistant cells by progressively increasing the concentration of paclitaxel in the culture medium. Viability assays with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium and sulforhodamine B were used to assess the cell resistance level and cytotoxic effects of paclitaxel treatment. Total RNA was isolated from both prostate cancer cell lines and their resistant versions, and cDNA samples were reverse transcribed from total RNA. Selected target genes of miRNAs that showed differences in expression and were estimated to be effective on drug resistance mechanism were analyzed with western blot analysis. RESULTS: Expression study of 86 miRNAs by RT-PCR demonstrated that several of the miRNAs were expressed at different levels in paclitaxel-resistant cells compared to wild-type cells. Moreover, the expression profiles of these miRNAs varied among different prostate cancer cell line types, with 13 miRNAs being up-regulated in the resistant cells. Among these, miR-200b-3p, miR-34b-3p and miR-375 exhibited a marked up-regulation. Further, miR-100-5p showed a prominent increase in paclitaxel-resistant VCaP-R and DU145-R cells. Western blot and RT-PCR studies showed that only the LARP1 and CCND1 genes were over-expressed up to 2-5 times in all paclitaxel-resistant cell lines compared to the other investigated genes. CONCLUSIONS: In this study, the three paclitaxel-resistant prostate cancer cell lines examined showed remarkably different miRNA expression profiles.

Valproic acid, a histone deacetylase inhibitor, induces apoptosis in breast cancer stem cells.

Cancer stem-like cells (CSCs) are a cell subpopulation that can reinitiate tumors, resist chemotherapy, give rise to metastases and lead to disease relapse because of an acquired resistance to apoptosis. Especially, epigenetic alterations play a crucial role in the regulation of stemness and also have been implicated in the development of drug resistance. Hence, in the present study, we examined the cytotoxic and apoptotic activity of valproic acid (VPA) as an inhibitor of histone deacetylases (HDACs) against breast CSCs (BCSCs). Increased expression of stemness markers were determined by western blotting in mammospheres (MCF-7s, a cancer stem cell-enriched population) propagated from parental MCF-7 cells. Anti-growth activity of VPA was determined via ATP viability assay. The sphere formation assay (SFA) was performed to assess the inhibitory effect of VPA on the self-renewal capacity of MCF-7s cells. Acetylation of histon H3 was detected with ELISA assay. Cell death mode was performed by Hoechst dye 33342 and propidium iodide-based flouresent stainings (for pyknosis and membrane integrity), by M30 and M65 ELISA assays (for apoptosis and primary or secondary necrosis) as well as cytofluorimetric analysis (caspase 3/7 activity and annexin-V-FITC staining for early and late stage apoptosis). VPA exhibited anti-growth effect against both MCF-7 and MCF-7s cells in a dose (0.6-20 mM) and time (24, 48, 72 h) dependent manner. As expected, MCF-7s cells were found more resistant to VPA than MCF-7 cells. It was observed that VPA prevented mammosphere formation at relatively lower doses (2.5 and 5 mM) while the acetylation of histon H3 was increased. At the same doses, VPA increased the M30 levels, annexin-V-FITC positivity and caspase 3/7 activation, implying the induction of apoptosis. The secondary necrosis (late stage of apoptosis) was also evidenced by nuclear pyknosis with propidium iodide staining positivity. Taken together, inhibition of HDACs is cytotoxic to BCSCs by apoptosis. Our results suggested that targeting the epigenetic regulation of histones may be a novel approach and hold significant promise for successful treatment of breast cancer.

A promising natural product, pristimerin, results in cytotoxicity against breast cancer stem cells in vitro and xenografts in vivo through apoptosis and an incomplete autopaghy in breast cancer.

Several natural products have been suggested as effective agents for the treatment of cancer. Given the important role of CSCs (Cancer Stem Cells) in cancer, which is a trendy hypothesis, it is worth investigating the effects of pristimerin on CSCs as well as on the other malignant cells (MCF-7 and MDA-MB-231) of breast cancer. The anti-growth activity of pristimerin against MCF-7 and MCF-7s (cancer stem cell enriched population) cells was investigated by real time viability monitorization (xCELLigence System®) and ATP assay, respectively. Mode of cell death was evaluated using electron and fluorescence microscopies, western blotting (autophagy, apoptosis and ER-stress related markers) and flow cytometry (annexin-V staining, caspase 3/7 activity, BCL-2 and PI3K expressions). Pristimerin showed an anti-growth effect on cancer cells and cancer stem cells with IC50 values ranging at 0.38-1.75µM. It inhibited sphere formation at relatively lower doses (<1.56µM). Apoptosis was induced in MCF-7 and MCF-7s cells. In addition, extensive cytoplasmic vacuolation was observed, implying an incompleted autophagy as evidenced by the increase of autophagy-related proteins (p62 and LC3-II) with an unfolded protein response (UPR). Pristimerin inhibited the growth of MCF-7 and MDA-MB-231-originated xenografts in NOD.CB17-Prkdcscid/J mice. In mice, apoptosis was further confirmed by cleavage of PARP, activation of caspase 3 and/or 7 and TUNEL staining. Taken together, pristimerin shows cytotoxic activity on breast cancer both in vitro and in vivo. It seems to represent a robust promising agent for the treatment of breast cancer. Pristimerin's itself or synthetic novel derivatives should be taken into consideration for novel potent anticancer agent(s).

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 (0-100µM). 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.

Pelargonium quercetorum Agnew induces apoptosis without PARP or cytokeratin 18 cleavage in non-small cell lung cancer cell lines.

Pelargonium species have various uses in folk medicine as traditional remedies, and several of them have been screened for their biological activity, including anticancer. Pelargonium quercetorum Agnew (P. quercetorum) is traditionally used for its anthelminthic activity. However, little is known about its biological activity or its effect on cancer cells. The aim of the present study was to determine the cytotoxic activity of P. quercetorum extract on lung cancer cell lines with varying properties. Following the analyses of its chemical composition, the cytotoxic activity was screened by the adenosine triphosphate viability test. M30-Apoptosense® and M65 EpiDeath® enzyme-linked immunosorbent assays were used to determine the cell death mode (apoptosis vs. necrosis). For apoptosis, additional methods, including Annexin-V-fluorescein isothiocyanate (FITC) and Hoechst 33342 staining, were employed. The cleavage of poly (adenosine diphosphate-ribose) polymerase (PARP) was assayed by western blotting to further dissect the apoptosis mechanism. The methanol extract of P. quercetorum caused cytotoxic activity in a dose-dependent manner. The mode of cell death was apoptosis, as evidenced by the positive staining of the cells for Annexin-V-FITC and the presence of pyknotic nuclei. Notably, neither PARP cleavage nor cytokeratin 18 fragmentation were observed. P.quercetorum caused cell death by an apoptosis mechanism that is slightly different from classical apoptosis. Therefore, future in vivo experiments are required for further understanding of the effect of this plant on cancer cells.

Ni(ii)/Cu(ii)/Zn(ii) 5,5-diethylbarbiturate complexes with 1,10-phenanthroline and 2,2'-dipyridylamine: synthesis, structures, DNA/BSA binding, nuclease activity, molecular docking, cellular uptake, cytotoxicity and the mode of cell death.

New 5,5-diethylbarbiturate (barb) complexes of Ni(ii), Cu(ii) and Zn(ii) with 1,10-phenanthroline (phen) and 2,2'-dipyridylamine (dpya), namely [Ni(phen-κN,N')3]Cl(barb)·7H2O (), [Cu(barb-κN)(barb-κ(2)N,O)(phen-κN,N')]·H2O (), [Cu(barb-κN)2(phen-κN,N')] (), [Zn(barb-κN)2(phen-κN,N')]·H2O (), [Ni(barb-κ(2)N,O)(dpya-κN,N')2]Cl·2H2O (), [Cu(barb-κ(2)N,O)2(dpya-κN,N')]·2H2O () and [Zn(barb-κN)2(dpya-κN,N')] (), were synthesized and characterized by elemental analysis, UV-vis, FT-IR and ESI-MS. The structures of the complexes were determined by X-ray crystallography. Notably, and were fluorescent in MeOH : H2O at rt. The interaction of the complexes with fish sperm (FS) DNA and bovine serum albumin (BSA) was investigated in detail by various techniques. The complexes exhibited groove binding along with a partial intercalative interaction with DNA, while the hydrogen bonding and hydrophobic interactions played a major role in binding to BSA. It is noteworthy that exhibited the highest affinity towards DNA and BSA. Enzyme inhibition assay showed that show a preference for both A/T and G/C rich sequences in pUC19 DNA, while and display a binding specificity to the G/C and A/T rich regions, respectively. These findings were further supported by molecular docking. The cellular uptake studies suggested that was deposited mostly in the membrane fraction of the cells. Among the present complexes, exhibited a very strong cytotoxic effect on A549, MCF-7, HT-29 and DU-145 cancer cells, being more potent than cisplatin. Moreover, induces cell death through the apoptotic mode obtained by flow cytometry.

Addition of niclosamide to palladium(II) saccharinate complex of terpyridine results in enhanced cytotoxic activity inducing apoptosis on cancer stem cells of breast cancer.

Wnt signaling is one of the core signaling pathways of cancer stem cells (CSCs). It is re-activated in CSCs and plays essential role in the survival, self-renewal and proliferation of these cells. Therefore, we aimed to evaluate the cytotoxic effects of palladium(II) complex which is formulated as [PdCl(terpy)](sac)2H2O and its combination with niclosamide which is an inhibitor of Wnt signaling pathway associated with breast cancer stem cells. Characteristic cell surface markers (CD44(+)/CD24(-)) were determined by flow cytometry in CSCs. ATP viability assay was used to determine the cytotoxic activity. The mode of cell death was evaluated morphologically using fluorescence microscopy and biochemically using M30 ELISA assay as well as performing qPCR. Our study demonstrated that the combination of niclosamide (1.5 µM) and Pd(II) complex (12.5, 25 and 50 µM) at 48 h has enhanced cytotoxic activity resulted from the induction of apoptosis (indicated by the presence of pyknotic nuclei, increments in M30 and over expression of proapoptotic genes of TNFRSF10A and FAS). Importantly, the addition of niclosamide resulted in the suppression of autophagy (proved by the decrease in ATG5 gene levels) that might have contributed to the enhanced cytotoxicity. In conclusion, the application of this combination may be regarded as a novel and effective approach for the treatment of breast cancer due to its promising cytotoxic effect on cancer stem cells that cause recurrence of the disease.

Apoptosis-inducing effect of a palladium(II) saccharinate complex of terpyridine on human breast cancer cells in vitro and in vivo.

The anti-growth effect of a palladium(II) complex-[PdCl(terpy)](sac)·2H2O] (sac=saccharinate, and terpy=2,2':6',2″-terpyridine)-was tested against human breast cancer cell lines, MCF-7 and MDA-MB-231. Anti-growth effect was assayed by the MTT and ATP viability assays in vitro and then confirmed on Balb/c mice in vivo. The mode of cell death was determined by both histological and biochemical methods. The Pd(II) complex had anti-growth effect on a dose dependent manner in vitro and in vivo. The cells died by apoptosis as evidenced by the pyknotic nucleus, cleavage of poly-(ADP-ribose) polymerase (PARP) and induction of active caspase-3. These results suggest that the palladium(II) saccharinate complex of terpyridine represents a potentially active novel complex for the breast cancer treatment, thus warrants further studies.

Synthesis, structural characterization and cell death-inducing effect of novel palladium(II) and platinum(II) saccharinate complexes with 2-(hydroxymethyl)pyridine and 2-(2-hydroxyethyl)pyridine on cancer cells in vitro.

Four palladium(II) and platinum(II) saccharinate (sac) complexes with 2-(hydroxymethyl)pyridine (2-hmpy) and 2-(2-hydroxyethyl)pyridine (2-hepy), namely trans-[Pd(2-hmpy)2(sac)2]·H2O (1), trans-[Pt(2-hmpy)2(sac)2]·3H2O (2), trans-[Pd(2-hepy)2(sac)2] (3) and trans-[Pt(2-hepy)2(sac)2] (4), have been synthesized and characterized by elemental analysis, UV-vis, IR and NMR. Single crystal X-ray analysis reveals that the metal(II) ions in each complex are coordinated by two sac and two 2-hmpy or 2-hepy ligands with a trans arrangement. Anticancer effects of 1-4 were tested against four different cancer cell lines (A549 and PC3 for lung cancer, C6 for glioblastoma, and Hep3B for liver cancer). Cytotoxicity was first screened by the MTT assay and the results were further confirmed by the ATP assay. The mode of cell death was determined by both histological and biochemical methods. Among the metal complexes, complex 2 resulted in relatively stronger anti-growth effect in a dose-dependent manner (3.13-200µM), compared to the others, by inducing apoptosis.