Anoikis and cancer cell differentiation: novel modes of shikonin derivatives anticancer action in vitro.

BACKGROUND: Shikonin is a naturally occurring naphthoquinone found in the roots of several genera of the Boraginaceae family, widely known for its numerous biological activities, such as antiinflammatory, antioxidant, antimicrobial and anticancer. In this study, the antitumor effect of six naphthoquinones isolated from the roots of Onosma visianii was evaluated using two cell lines, mouse melanoma B16 and highly aggressive rat glioma cell line C6. METHODS AND RESULTS: All examined shikonins dose-dependently decreased the viability of tested cells, with compounds 5 and 6 being the most potent ones and hence subjected to further analysis. The diminished viability of B16 melanoma cells was in correlation with detected caspase-mediated apoptosis. Importantly, observed altered cell morphology along with the loss of dividing potential upon exposure to both shikonins implied reprogram of B16 cell phenotype. Elevated expression of myelin basic protein indicated the acquirement of Schwann-like cell phenotype, while detected autophagy might be connected to this phenomenon. On the contrary, upon exposure to both agents, C6 cells underwent specific cell death-anoikis, provoked by detachment from the extracellular matrix and compromised integrin signaling. Oppositely to compound 5, compound 6 realized anoikis in a caspase-independent manner and under sustained ERK1/2 activation, indicating the deviation from standard proanoikis signaling. CONCLUSIONS: Herein, we have pointed out the diversity and novelty in the mode of action of shikonin derivatives depending on the tumor cell features, which represents a good platform for new investigations of these promising natural compounds.

Carboranes as Potent Phenyl Mimetics: A Comparative Study on the Reversal of ABCG2-Mediated Drug Resistance by Carboranylquinazolines and Their Organic Isosteres.

Multidrug resistance is a major challenge in clinical cancer therapy. In particular, overexpression of certain ATP-binding cassette (ABC) transporter proteins, like the efflux transporter ABCG2, also known as breast cancer resistance protein (BCRP), has been associated with the development of resistance to applied chemotherapeutic agents in cancer therapies, and therefore targeted inhibition of BCRP-mediated transport might lead to reversal of this (multidrug) resistance (MDR). In a previous study, we have described the introduction of a boron-carbon cluster, namely closo-dicarbadodecaborane or carborane, as an inorganic pharmacophore into a polymethoxylated 2-phenylquinazolin-4-amine backbone. In this work, the scope was extended to the corresponding amide derivatives. As most of the amide derivatives suffered from poor solubility, only the amide derivative QCe and the two amine derivatives DMQCc and DMQCd were further investigated. Carboranes are often considered as sterically demanding phenyl mimetics or isosteres. Therefore, the organic phenyl and sterically demanding adamantyl analogues of the most promising carborane derivatives were also investigated. The studies showed that the previously described DMQCd, a penta-methoxylated N-carboranyl-2-phenylquinazolin-4-amine, was by far superior to its organic analogues in terms of cytotoxicity, inhibition of the human ABCG2 transporter, as well as the ability to reverse BCRP-mediated mitoxantrone resistance in MDCKII-hABCG2 and HT29 colon cancer cells. Our results indicate that DMQCd is a promising candidate for further in vitro as well as in vivo studies in combination therapy for ABCG2-overexpressing cancers.

The Second Derivative of Fullerene C60 (SD-C60) and Biomolecular Machinery of Hydrogen Bonds: Water-Based Nanomedicine.

The human body contains 60-70% water, depending on age. As a body fluid, it is not only a medium in which physical and chemical processes take place, but it is also one of the active mediators. Water is the richest substance with non-covalent hydrogen bonds. Water molecules, by themselves (in vacuum), are diamagnetic but when organized into clusters, they become diamagnetic or paramagnetic. Also, biomolecules (DNA, collagen, clathrin, and other proteins) have non-covalent hydrogen bonds in their structure. The interaction, as well as signal transmission, between water and biomolecules is achieved through the vibrations of covalent and non-covalent hydrogen bonds, which determine the state and dynamics of conformational changes in biomolecules. Disruptive conformational changes in biomolecules, cells, and tissues lead to their dysfunctionality, so they are a frequent cause of many disorders and diseases. For example, the rearrangement of hydrogen bonding due to mitochondrial disease mutation in cytochrome bc1 disturbs heme bH redox potential and spin state. In order to prevent and repair the dysfunctional conformational changes, a liquid substance was developed based on the second derivative of the C60 molecule (SD-C60), which has classical and quantum properties. The characterization of SD-C60 by UV-VIS-NIR, FTIR, TEM, and AFM/MFM was performed and it is shown that SD-C60 water layers generate vibrations with near-zero phase dispersion which are transmitted through Fibonacci's water chains to biomolecules. In comparison with previously published SD-C60 derivate (3HFWC, size until 10 nm, and 1-5 water layers), the improved formulation (3HFWC-W, size 10-25 nm, and 6-9 water layers) showed multiplied cytotoxic activity against melanoma cell lines of different aggressiveness. Apart from this, the mode of action was preserved and based on an induction of senescence rather than cell death. Importantly, high selectivity towards malignant phenotypes was detected. Observed effects can be ascribed to a machinery of hydrogen bonds, which are generated in SD-C60 and transmitted through water to biomolecules. This approach may open a new field in science and healthcare-a "water-based nanomedicine".

Anticancer Potential of Xanthohumol and Isoxanthohumol Loaded into SBA-15 Mesoporous Silica Particles against B16F10 Melanoma Cells.

Xanthohumol (XN) and isoxanthohumol (IXN), prenylated flavonoids from Humulus lupulus, have been shown to possess antitumor/cancerprotective, antioxidant, antiinflammatory, and antiangiogenic properties. In this study, mesoporous silica (SBA-15) was loaded with different amounts of xanthohumol and isoxanthohumol and characterized by standard analytical methods. The anticancer potential of XN and IXN loaded into SBA-15 has been evaluated against malignant mouse melanoma B16F10 cells. When these cells were treated with SBA-15 containing xanthohumol, an increase of the activity correlated with a higher immobilization rate of XN was observed. Considering the amount of XN loaded into SBA-15 (calculated from TGA), an improved antitumor potential of XN was observed (IC50 = 10.8 ± 0.4 and 11.8 ± 0.5 µM for SBA-15|XN2 and SBA-15|XN3, respectively; vs. IC50 = 18.5 ± 1.5 µM for free XN). The main mechanism against tumor cells of immobilized XN includes inhibition of proliferation and autophagic cell death. The MC50 values for SBA-15 loaded with isoxanthohumol were over 300 µg/mL in all cases investigated.

Combined Action of Hyper-Harmonized Hydroxylated Fullerene Water Complex and Hyperpolarized Light Leads to Melanoma Cell Reprogramming In Vitro.

(1) Background: Their unique structure and electron deficiency have brought fullerenes into the focus of research in many fields, including medicine. The hyper-harmonized hydroxylated fullerene water complex (3HFWC) formulation has solved the limitations of the poor solubility and bioavailability of fullerenes. To achieve better antitumor activity, 3HFWC was combined with short-term irradiation of cells with hyperpolarized light (HPL) generated by the application of a nanophotonic fullerene filter in a Bioptron® device. The benefits of HPL were confirmed in the microcirculation, wound healing and immunological function. (2) Methods: B16, B16-F10 and A375 melanoma cells were exposed to a wide spectrum of 3HFWC doses and to a single short-term HPL irradiation. (3) Results: Apart from the differences in the redox status and level of invasiveness, the effects of the treatments were quite similar. Decreased viability, morphological alteration, signs of melanocytic differentiation and cellular senescence were observed upon the successful internalization of the nanoquantum substance. (4) Conclusions: Overall, 3HFWC/HPL promoted melanoma cell reprogramming toward a normal phenotype.

Mesenchymal Stem Cells From Mouse Hair Follicles Reduce Hypertrophic Scarring in a Murine Wound Healing Model.

Wound healing of acute full-thickness injuries and chronic non-healing ulcers leads to delayed wound closure, prolonged recovery period and hypertrophic scarring, generating a demand for an autologous cell therapy and a relevant pre-clinical research models for wound healing. In this study, an immunocompetent model for wound healing was employed using a syngeneic murine cell line of mesenchymal stem cells cultured from the mouse whisker hair follicle outer root sheath (named moMSCORS). moMSCORS were isolated using an air-liquid interface method, expanded in vitro and characterized according to the MSC definition criteria - cell viability, in vitro proliferation, MSC phenotype and multi-lineage differentiations. Moreover, upon applying moMSCORS in an in vivo full-thickness wound model in the syngeneic C57BL/6 mice, the treated wounds displayed different morphology to that of the untreated wound beds. Quantitative evaluation of angiogenesis, granulation and wound closure involving clinical scoring and software-based quantification indicated a lower degree of inflammation in the treated wounds. Histological staining of treated wounds by the means of H&E, Alcian Blue, PicroSirius Red and αSMA immune labelling showed lower cellularity, less collagen filaments as well as thinner dermal and epidermal layers compared with the untreated wounds, indicating a general reduction of hypertrophic scars. The decreased inflammation, accelerated wound closure and non-hypertrophic scarring, which were facilitated by moMSCORS, hereby address a common problem of hypertrophic scars and non-physiological tissue properties upon wound closure, and additionally offer an in vivo model for the autologous cell-based wound healing.

Synthetic Tubulysin Derivative, Tubugi-1, Against Invasive Melanoma Cells: The Cell Death Triangle.

BACKGROUND/AIM: Tubugi-1 is a more stable and accessible synthetic counterpart of natural tubulysins. This study aimed to evaluate its cytotoxic potential against anaplastic human melanoma cells. MATERIALS AND METHODS: The viability of A-375 cells was determined by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet assay. The type of cell death and proliferative rate were investigated using flow cytometry and fluorescent microscopy, while the molecular background was evaluated by western blot. RESULTS: Tubugi-1 reduced the viability of A-375 cells, inducing massive micronucleation, followed by augmented expression of inhibitor of nuclear factor-κB and caspase-2, typical of a mitotic catastrophe. Disturbed proliferation and G2M block with prominent caspase activity, weakened the expression of B-cell lymphoma 2 and B-cell lymphoma 2-associated X transient up-regulation, coexisted with intensive autophagy. Specific inhibition of autophagy by chloroquine resulted in conversion from mitotic catastrophe to rapid apoptosis. CONCLUSION: Multilevel anticancer action of tubugi-1 is extended by co-application of an autophagy inhibitor, giving a new dimension in further preclinical advancement of this potential agent.

The synthetic tubulysin derivative, tubugi-1, improves the innate immune response by macrophage polarization in addition to its direct cytotoxic effects in a murine melanoma model.

Synthetic tubugis are equally potent but more stable than their natural forms. Their anticancer potential was estimated on a solid melanoma in vitro and in vivo. Tubugi-1 induced the apoptosis in B16 cells accompanied with strong intracellular production of reactive species, subsequently imposing glutathione and thiol group depletion. Paradoxically, membrane lipids were excluded from the cascade of intracellular oxidation, according to malondialdehyde decrease. Although morphologically apoptosis was typical, externalization of phosphatidylserine (PS) as an early apoptotic event was not detected. Even their exposition is pivotal for apoptotic cell eradication, primary macrophages successfully eliminated PS-deficient tubugi-1 induced apoptotic cells. The tumor volume in animals exposed to the drug in therapeutic mode was reduced in comparison to control as well as to paclitaxel-treated animals. Importantly, macrophages isolated from tubugi-1 treated animals possessed conserved phagocytic activity and were functionally and phenotypically recognized as M1. The cytotoxic effect of tubugi-1 is accomplished through its ability to polarize the macrophages toward M1, probably by PS independent apoptotic cell engulfment. The unique potential of tubugi-1 to prime the innate immune response through the induction of a specific pattern of tumor cell apoptosis can be of extraordinary importance from fundamental and applicable aspects.

Senescence as a main mechanism of Ritonavir and Ritonavir-NO action against melanoma.

The main focus of this study is exploring the effect and mechanism of two HIV-protease inhibitors: Ritonavir and Ritonavir-nitric oxide (Ritonavir-NO) on in vitro growth of melanoma cell lines. NO modification significantly improved the antitumor potential of Ritonavir, as the IC50 values of Ritonavir-NO were approximately two times lower than IC50 values of the parental compound. Our results showed for the first time, that both compounds induced senescence in primary and metastatic melanoma cell lines. This transformation was manifested as a change in cell morphology, enlargement of nuclei, increased cellular granulation, upregulation of ß-galactosidase activity, lipofuscin granules appearance, higher production of reactive oxygen species and persistent inhibition of proliferation. The expression of p53, as one of the key regulators of senescence, was upregulated after 48 hours of Ritonavir-NO treatment only in metastatic B16F10 cells, ranking it as a late-response event. The development of senescent phenotype was consistent with the alteration of the cytoskeleton-as we observed diminished expression of vinculin, α-actin, and ß-tubulin. Permanent inhibition of S6 protein by Ritonavir-NO, but not Ritonavir, could be responsible for a stronger antiproliferative potential of the NO-modified compound. Taken together, induction of senescent phenotype may provide an excellent platform for developing therapeutic approaches based on selective killing of senescent cells.

The hop-derived prenylflavonoid isoxanthohumol inhibits the formation of lung metastasis in B16-F10 murine melanoma model.

Isoxanthohumol (IXN), a prenylflavonoid from hops and beer, gained increasing attention as a potential chemopreventive agent. In the present study, IXN antimetastatic potential in vitro against the highly invasive melanoma cell line B16-F10 and in vivo in a murine metastatic model was investigated. Melanoma cell viability was diminished in a dose-dependent manner following the treatment with IXN. This decrease was a consequence of autophagy and caspase-dependent apoptosis. Additionally, the dividing potential of highly proliferative melanoma cells was dramatically affected by this isoflavanone, which was in correlation with an abrogated cell colony forming potential, indicating changes in their metastatic features. Concordantly, IXN promoted strong suppression of the processes that define metastasis- cell adhesion, invasion, and migration. Further investigation at the molecular level revealed that the abolished metastatic potential of a melanoma subclone was due to disrupted integrin signaling. Importantly, these results were reaffirmed in vivo where IXN inhibited the development of lung metastatic foci in tumor-challenged animals. The results of the present study may highlight the beneficial effects of IXN on melanoma as the most aggressive type of skin cancer and will hopefully shed a light on the possible use of this prenylflavonoid in the treatment of metastatic malignancies.

Anticancer and Differentiation Properties of the Nitric Oxide Derivative of Lopinavir in Human Glioblastoma Cells.

Glioblastoma (GBM) is the most frequent and deadly form of primary malignant brain tumor among adults. A promising emerging approach for GBM treatment may be offered from HIV protease inhibitors (HIV-PIs). In fact, in addition to their primary pharmacological activity in the treatment of HIV infection, they possess important anti-neoplastic effects. According to previous studies, the addition of a nitric oxide (NO) donating group to parental compounds can reduce their toxicity and enhance the anticancer action of various compounds, including HIV-PIs. In this study we compared the effects of the HIV-PI Lopinavir (Lopi) and of its NO-derivative Lopinavir-NO (Lopi-NO) on the in vitro growth of LN-229 and U-251 human GBM cell lines. Lopi-NO reduced the viability of LN-229 and U-251 cells at significantly lower concentrations than the parental drug. In particular, Lopi-NO inhibited tumor cell proliferation and induced the differentiation of U-251 cells toward an astrocyte-like phenotype without triggering significant cell death in both cell types. The anticancer effect of Lopi-NO was persistent even upon drug removal. Furthermore, Lopi-NO induced strong autophagy that did not appear to be related to its chemotherapeutic action. Overall, our results suggest that Lopi-NO could be a potential effective anticancer drug for GBM treatment.

Drug Delivery System for Emodin Based on Mesoporous Silica SBA-15.

In this study mesoporous silica SBA-15 was evaluated as a vehicle for the transport of cytotoxic natural product emodin (EO). SBA-15 was loaded with different quantities of EO (SBA-15|EO1⁻SBA-15|EO5: 8⁻36%) and characterized by traditional methods. Several parameters (stabilities) and the in vitro behavior on tumor cell lines (melanoma A375, B16 and B16F10) were investigated. SBA-15 suppresses EO release in extremely acidic milieu, pointing out that EO will not be discharged in the stomach. Furthermore, SBA-15 protects EO from photodecomposition. In vitro studies showed a dose dependent decrease of cellular viability which is directly correlated with an increasing amount of EO in SBA-15 for up to 27% of EO, while a constant activity for 32% and 36% of EO in SBA-15 was observed. Additionally, SBA-15 loaded with EO (SBA-15|EO3) does not disturb viability of peritoneal macrophages. SBA-15|EO3 causes inhibition of tumor cell proliferation and triggers apoptosis, connected with caspase activation, upregulation of Bax, as well as Bcl-2 and Bim downregulation along with amplification of poly-(ADP-ribose)-polymerase (PARP) cleavage fragment. Thus, the mesoporous SBA-15 is a promising carrier of the water-insoluble drug emodin.

Versatile antitumor potential of isoxanthohumol: Enhancement of paclitaxel activity in vivo.

Isoxanthohumol (IXN), a prenylated flavonoid from hops, exhibits diverse biological activities, e.g. antitumor, antiinflammatory, antioxidant and antiangiogenic. In this study, the effect of IXN is evaluated on two melanoma cell lines with dissimilar molecular background, B16 and A375. The treatment of both cell lines with IXN resulted in dose-dependent decrease of cell viability. Abolished viability was in correlation with changed morphology and loss of dividing potential indicating phenotypical alteration of both tested cell lines. While modified B16 cells underwent the process of non-classic differentiation followed by tyrosinase activity without enhancement of melanin content, inhibition of Notch 1, ß-catenin and Oct-3/4 was observed in A375 cells indicating loss of their pluripotent characteristics. In parallel with this, distinct subpopulations in both cell cultures entered the process of programmed cell death-apoptosis in a caspase independent manner. The described changes in cultures upon exposure to IXN could be connected with the suppression of reactive oxygen (ROS) and nitrogen species (RNS) induced by the drug. Despite the differences in which IXN promoted modifications in the upper part of the PI3K/Akt and MEK-ERK signaling pathways between B16 and A375 cells, p70S6K and its target S6 protein in both types of melanoma cells, after transient activation, became inhibited. In addition to direct input of IXN on cell viability, this study for the first time shows that IXN strongly sensitizes melanoma cells to the treatment with paclitaxel in vivo, in concordance with data obtained in vitro on B16 cells as well as their highly invasive F10 subclone.

Ruthenium(II) p-cymene complex bearing 2,2'-dipyridylamine targets caspase 3 deficient MCF-7 breast cancer cells without disruption of antitumor immune response.

[Ru(η(6)-p-cym)Cl{dpa(CH2)4COOEt}][PF6] (cym=cymene; dpa=2,2'-dipyridylamine; complex 2) was prepared and characterized by elemental analysis, IR and multinuclear NMR spectroscopy, as well as ESI-MS and X-ray structural analysis. The structural analog without a side chain [Ru(η(6)-p-cym)Cl(dpa)][PF6] (1) as well as 2 were investigated in vitro against 518A2, SW480, 8505C, A253 and MCF-7 cell lines. Complex 1 is active against all investigated tumor cell lines while the activity of compound 2 is limited only to caspase 3 deficient MCF-7 breast cancer cells, however, both are less active than cisplatin. As CD4(+)Th cells are necessary to trigger all the immune effector mechanisms required to eliminate tumor cells, besides testing the in vitro antitumor activity of 1 and 2, the effect of ruthenium(II) complexes on the cells of the adaptive immune system have also been evaluated. Importantly, complex 1 applied in concentrations which were effective against tumor cells did not affect immune cell viability, nor did exert a general immunosuppressive effect on cytokine production. Thus, beneficial characteristics of 1 might contribute to the overall therapeutic properties of the complex.

Novel inhibitors of macrophage migration inhibitory factor prevent cytokine-induced beta cell death.

Macrophage migration inhibitory factor is a multifunctional cytokine involved in the regulation of immune processes and also in apoptosis induction. Elevated MIF expression is detrimental for insulin-producing beta cells and MIF inhibition protected beta cells from several cytotoxic insults such as inflammatory cytokines, high fatty acids or high glucose concentrations. Therefore, the aim of this study was to investigate two newly synthesized small molecule MIF inhibitors (K664-1 and K647-1) and to compare them with previously established effects of the prototypical MIF inhibitor, ISO-1. Our results indicate that K664-1 and K647-1 are 160- and 40-fold more effective in inhibition of MIF׳s tautomerase activity than ISO-1. Also, new inhibitors confer beta cell protection from cytokine-triggered apoptosis at significantly lower concentrations than ISO-1. Although all three MIF inhibitors inhibit caspase 3 activity, K664-1 and K647-1 suppress pro-apoptotic BAX protein expression and up-regulate anti-apoptotic Bcl-2 mRNA. Finally, all three MIF inhibitors operate through blockade of nitric oxide production stimulated by cytokines. In conclusion, two novel MIF inhibitors are more potent than ISO-1 and operate through inhibition of the mitochondria-related apoptotic pathway. We propose that these compounds represent a unique class of anti-MIF antagonists that should be further tested for therapeutic use.