McCoy's Medium Research Articles

In vitro evaluation of natural hydroxyapatite from Osteoglossum bicirrhosum fish scales for biomedical application

AbstractThis study reports the obtainment of bioactive hydroxyapatite (HAp) extracted from scales of arowana fish (FSHA) (Osteoglossum bicirrhosum) by alkaline treatment followed by calcination at 600 and 800°C. The cell viability and bioactivity of hydroxyapatite particles (FSHA) were investigated and compared with those of HAp synthesized (s.HA) by the precipitation method. The HAp particles from fish scales showed non‐toxic behavior to dental pulp stem cells similar to HAp synthesized. Additionally, bioactivity assays show that the Hap from natural source forms the bone‐like apatite layer faster than s.HA sample, after being incubated in McCoy medium for 3 days. The results illustrate that HAp obtained from Osteoglossum bicirrhosum fish scale bio‐waste showed excellent biocompatibility. Besides, this study provides an effective method for converting low‐cost bio‐waste into a value‐added and it can be a potential alternative biomaterial for various biomedical applications.

Development of a Novel Calreticulin Reporter for Determination of Immunogenic Cell Death

Immunogenic cell death (ICD) initiates a series of damage associated molecular patterns (DAMPs) that are able to activate an immune response. Of these, translocation of calreticulin (CRT) from the endoplasmic reticulum (ER) to the outer leaflet of the cell membrane is a hallmark event that leads to activation of antigen presenting cells (APC), thus priming an immune response. Induction of ICD in cancer cells may provide a manner of activating an immunological anti‐tumor response, which may be utilized in immunotherapy. Currently, a few chemotherapeutic drugs, such as doxorubicin, are known to induce ICD and have been proposed to be repurposed for this use. Thus, it is likely that other known drugs may exhibit ICD induction and may be utilized in immunotherapy. However, to evaluate such drugs, there is a need to develop a high throughput method of detecting ICD.Here, a novel ICD reporter based on translocation of CRT and the HiBit‐tag expression system is described. This system utilizes a recombinant HiBit‐tag that associates with cell impermeable LgBit, thereby forming a bioluminescent protein complex. HiBit‐tagged CRT will complex with LgBit when translocated to the outer leaflet of the cell membrane, which may be detected bioluminescently by addition of D‐luciferin. Thus, the intensity of bioluminescence may be correlated to translocation of CRT, a hallmark of ICD.To create the novel ICD reporter, the human CRT gene was amplified using polymerase chain reaction (PCR) from plasmid HsCD00322958 (Harvard Medical School, MA), and inserted onto the 3′ end of the HiBit tag (pBiT3.1‐N, Promega, WI) using restriction enzyme digestion (PspXI and SbfI) followed by ligation. The recombinant HiBiT‐CRT plasmid was transformed into competent DH5α E. coli cells using the heat‐shock method. The HiBit‐CRT cassette was validated by DNA Sanger sequencing (Genscript, Piscataway, NJ). In order to transfect human ovarian adenocarcinoma cells (SKOV‐3) with the ICD reporter, the optical concentration of geneticin was determined by performing a kill curve. In brief, SKOV‐3 cells were maintained in McCoy's 5A cell medium supplemented with 10 % fetal bovine serum (FBS) at 37°C and 5% CO2, and then treated with varying concentrations of geneticin (0.05 mg/mL, 0.1 mg/mL, 0.25 mg/mL, 0.5 mg/mL, 0.75 mg/mL, 1 mg/mL, 1.25 mg/mL, 1.5 mg/mL, 1.75 mg/mL, 2 mg/mL). The cell viability was evaluated daily for 7 days using bright field microscopy. The optimal concentration was determined to be 1.25 mg/mL. Next, SKOV‐3 cells will be transfected with the ICD reporter, and used to screen the Approved Oncology Drug Set VI (kind gift from the National Cancer Institute) for compounds that induce ICD.Support or Funding InformationWestern Illinois University Research Council GrantThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Zinc-doped Calcium Phosphate Coating on Titanium Surface Using Ostrich Eggshell as a Ca2+ Ions Source

Natural calcium source materials can be thermochemically processed and directly transformed into hydroxyapatite. In this work, ostrich eggshell was used as Ca2+ ions source in the preparation of zinc-calcium phosphate coatings on Ti substrates promoted by a two-step deposition method. The obtained coatings were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy with field emission gun (FEG-SEM), bioactivity using McCoy medium and toxicity with chicken embryo chorioallantoic membrane (CAM). The results showed the presence of Znbrushite and Zn-hydroxyapatite as coating phases. Bioactivity was observed in all samples showing bone-like apatite on their surface. The toxicity test showed inflammatory response between mild to moderate confirming the material’s biocompatibility. The use of ostrich eggshells was shown to be effective as a Ca2+ ions source to obtain zinc-containing hydroxyapatite coatings on Ti substrates.

Bioactivity Assessment of Calcium Phosphate Coatings

Nowadays, bioactive coatings or modifications on titanium surface have been tested in vitro and in vivo. In this study, two types of calcium phosphate coatings were produced by a chemical deposition method and their bioactivity assay in cell culture medium were investigated. The calcium phosphate coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with field emission gun (FEG-SEM) analyses. Titanium substrate was successfully coated with brushite using chemical deposition method and, after a second step of conversion, the hydroxyapatite coating was obtained. The hydroxyapatite coating showed a bioactivity property after 14 days’ incubation in McCoy medium culture.

A simple method to induce hypoxia-induced vascular endothelial growth factor-A (VEGF-A) expression in T24 human bladder cancer cells.

Angiogenesis is an essential process for the establishment, development, and dissemination of several malignant tumors including bladder cancer. The hypoxic condition promotes the stabilization of hypoxia-inducible factor 1 alpha (HIF-1α), which translocates to the nucleus to mediate angiogenic factors including the vascular endothelial growth factor A (VEGF-A). AnaeroGen system was developed for microbiology area to create a low oxygen tension required to the growth of anaerobic bacteria. Here, we hypothesized the use of AnaeroGen system to induce hypoxia in T24 human bladder carcinoma cells, in order to promote the overexpression of VEGF-A. T24 cells were cultured in six-well plates containing McCoy medium. Exposures of T24 cells to hypoxia for 1, 8, 24, and 48h were performed using the Oxoid AnaeroGen system, while T24 cells under normoxia were used as control. The expression of VEGF-A and HIF-1α was analyzed by real-time PCR. ELISA for HIF-1α was carried out. The VEGF-A expression increased significantly by Oxoid AnaeroGen-induced hypoxia in a time-depending manner, reaching the peak in 48h of hypoxia. Although HIF-1α mRNA was not changed, HIF-1α protein was increased in the presence of hypoxia, reaching a peak at 8h. These results demonstrated that the Oxoid AnaeroGen system is a simple method to expose T24 cells to hypoxia and efficiently to upregulate VEGF expression in T24 cells.

Frozen and Fresh Ovarian Tissue Require Different Culture Media to Promote in Vitro Development of Bovine Preantral Follicles

The aim of this study was to evaluate the efficiency of different media in the in vitro culture of bovine preantral follicles that were used either fresh or following slow freezing treatment. Frozen and fresh noncultured or cultured ovarian fragments were processed for histological, viability, and cell proliferation analyses. For cryopreservation, a solution containing 1.5 M ethylene glycol was frozen in a programmable biological freezer. After thawing, a portion of the samples was destined for frozen controls. The remainder were cultured in vitro for 5 days in three media: α-MEM, McCoy, or M199. Samples from these culture media were collected on days 1 and 5 for quantification of reactive oxygen species (ROS) and for hormonal assays. In fresh-cultured tissues, the percentage of morphologically normal follicles was significantly higher when cultured in M199 compared to that in the other media. In frozen-cultured tissues, McCoy medium was significantly superior to the other media, and was the only treatment that helped in maintaining the viability similar to fresh and frozen controls. Upon quantification of the nucleolus organizer region, we observed greater proliferation of granulosa cells in the frozen-cultured tissues with McCoy medium, and lesser proliferation in fresh-cultured tissues only with α-MEM. In frozen-cultured tissues, ROS levels were highest at day 1 and progressively reduced during culture, independent of the media used. In conclusion, under the conditions used in this study, the M199 and McCoy media are recommended for the culture of follicles derived from fresh and frozen ovarian tissues, respectively.

Monitoring preantral follicle survival and growth in bovine ovarian biopsies by repeated use of neutral red and cultured in vitro under low and high oxygen tension

The development and optimization of preantral follicle culture methods are crucial in fertility preservation strategies. As preantral follicle dynamics are usually assessed by various invasive techniques, the need for alternative noninvasive evaluation tools exists. Recently, neutral red (NR) was put forward to visualize preantral follicles in situ within ovarian cortical fragments. However, intense light exposure of NR-stained tissues can lead to cell death because of increased reactive oxygen species production, which is also associated with elevated oxygen tension. Therefore, we hypothesize that after repeated NR staining, follicle viability and dynamics can be altered by changes in oxygen tension. In the present study, we aim (1) to determine whether NR can be used to repeatedly assess follicular growth, activation, and viability and (2) to assess the effect of a low (5% O2) or high (20% O2) oxygen tension on the viability, growth, and stage transition of preantral follicles cultured in vitro by means of repeated NR staining. Cortical slices (n = 132; six replicates) from bovine ovaries were incubated for 3 hours at 37 °C in a Leibovitz medium with 50 μg/mL NR. NR-stained follicles were evaluated in situ for follicle diameter and morphology. Next, cortical fragments were individually cultured in McCoy's 5A medium for 6 days at 37 °C, 5% CO2, and 5% or 20% O2. On Days 4 and 6, the fragments were restained by adding NR to the McCoy's medium and follicles were reassessed. In both low and high oxygen tension treatment groups, approximately 70% of the initial follicles survived a 6-day in vitro culture, but no significant difference in follicle survival on Day 4 or 6 could be observed compared with Day 0 (P > 0.05). A significant decrease in the number of primordial and increase in primary and secondary follicles was observed within 4 days of culture (P < 0.001). In addition, a significant increase of the mean follicle diameter in NR-stained follicles was observed (P < 0.001), resulting in an average growth of 11.82 ± 0.81 μm (5% O2) and 11.78 ± 1.06 μm (20% O2) on Day 4 and 20.94 ± 1.24 μm (5% O2) and 19.12 ± 1.36 μm (20% O2) on Day 6 compared with Day 0. No significant differences in follicle growth rate or stage transition could be observed between 5% and 20% O2 (P > 0.05). In conclusion, after repeated NR staining, we could not find a difference between low and high oxygen tension in terms of follicle viability, stage transition, or growth. Therefore, under our culture conditions follicle dynamics are not determined by the oxygen tension in combination with quality assessment protocols using repeated NR staining.

Fresh and vitrified bovine preantral follicles have different nutritional requirements during in vitro culture

The aim of this study was to compare the efficiency of different media for the in vitro culturing of fresh and vitrified bovine ovarian tissues. Fragments of the ovarian cortex were subjected to vitrification and histological and viability analyses or were immediately cultured in vitro using the alfa minimum essential medium, McCoy's 5A medium (McCoy), or medium 199 (M199). Samples of different culture media were collected on days 1 (D1) and 5 (D5) for quantification of reactive oxygen species and for hormonal assays. In non-vitrified (i.e., fresh) ovarian tissue cultures, the percentage of morphologically normal follicles was significantly greater than that recorded for the other media (e.g., M199). In the case of previously vitrified tissues, the McCoy medium was significantly superior to the other media in preserving follicular morphology up until the last culture day (i.e., D5), thus maintaining a similar percentage from D1 to D5. Reactive oxygen species levels were higher in D1 vitrified cultured tissues, but there were no differences in the levels among the three media after 5days. The hormonal assays showed that in the case of previously vitrified tissues, at D5, progesterone levels increased on culture in the M199 medium and estradiol levels increased on culture in the McCoy medium. In conclusion, our results indicate that the use of M199 would be recommended for fresh tissue cultures and of McCoy for vitrified tissue cultures.

Revisiting Indocyanine Green: Effects of Serum and Physiological Temperature on Absorption and Fluorescence Characteristics

Indocyanine green (ICG) remains as the only near infrared dye approved by the FDA. Despite its long history of usage in clinical medicine, a systematic study of the effects of serum proteins at physiologically relevant levels and temperature on absorption and fluorescence characteristics of ICG has been missing. We incubated ICG at concentrations in the range of 0.6-25.8 μM in McCoy's 5a cell culture medium, without and with supplemental fetal bovine serum (FBS) at 5% and 10% levels. Our analyses of absorption and fluorescence spectra indicate that the peak absorbance of ICG associated with its monomeric form increases in the presence of FBS. For example, at ICG concentration of 25.8 μM, the monomer absorbance is increased by nearly 100% in the presence of 10% FBS. Similarly, there is an increase in the relative fluorescence quantum yield of ICG, by as much as nearly 3.5 times in the presence of FBS. When incubated at 37 °C, the presence of FBS in the cell culture medium helps maintain the monomeric absorption of ICG and sustain the increased fluorescence emission. We offer explanations to describe the possible photophysical mechanisms underlying the observed effects and discuss the importance of these results to in-vivo applications of ICG.

Peroxisome Proliferator-activated Receptor γ Agonists Induce Cell Cycle Arrest through Transcriptional Regulation of Krüppel-like Factor 4 (KLF4)

Peroxisome proliferator-activated receptor γ (PPARγ), a subgroup of ligand-activated nuclear receptors, plays critical roles in cell cycle regulation, differentiation, apoptosis, and invasion. PPARγ is involved in tumorigenesis and is a potent target for cancer therapy. PPARγ transactivation of KLF4 has been demonstrated in various studies; however, how PPARγ regulates KLF4 expression is not clear. In this study, we reveal that PPARγ regulates the expression of KLF4 by binding directly to the PPAR response element (PPRE) within the KLF4 promoter. The PPRE resides at -1657 to -1669 bp upstream of the KLF4 ATG codon, which is essential for the transactivation of troglitazone-induced KLF4 expression. Furthermore, we found that stable silencing of KLF4 obviously suppressed the G(1)/S arrest and anti-proliferation effects induced by PPARγ ligands. Taken together, our data indicate that up-regulation of KLF4 upon PPARγ activation is mediated through the PPRE in the KLF4 promoter, thus providing further insights into the PPARγ signal transduction pathway as well as a novel cancer therapeutic strategy.

A Role for Prolyl 3-Hydroxylase 2 in Post-translational Modification of Fibril-forming Collagens

The fibrillar collagen types I, II, and V/XI have recently been shown to have partially 3-hydroxylated proline (3Hyp) residues at sites other than the established primary Pro-986 site in the collagen triple helical domain. These sites showed tissue specificity in degree of hydroxylation and a pattern of D-periodic spacing. This suggested a contributory role in fibril supramolecular assembly. The sites in clade A fibrillar α1(II), α2(V), and α1(I) collagen chains share common features with known prolyl 3-hydroxylase 2 (P3H2) substrate sites in α1(IV) chains implying a role for this enzyme. We pursued this possibility using the Swarm rat chondrosarcoma cell line (RCS-LTC) found to express high levels of P3H2 mRNA. Mass spectrometry determined that all the additional candidate 3Hyp substrate sites in the pN type II collagen made by these cells were highly hydroxylated. In RNA interference experiments, P3H2 protein synthesis was suppressed coordinately with prolyl 3-hydroxylation at Pro-944, Pro-707, and the C-terminal GPP repeat of the pNα1(II) chain, but Pro-986 remained fully hydroxylated. Furthermore, when P3H2 expression was turned off, as seen naturally in cultured SAOS-2 osteosarcoma cells, full 3Hyp occupancy at Pro-986 in α1(I) chains was unaffected, whereas 3-hydroxylation of residue Pro-944 in the α2(V) chain was largely lost, and 3-hydroxylation of Pro-707 in α2(V) and α2(I) chains were sharply reduced. The results imply that P3H2 has preferred substrate sequences among the classes of 3Hyp sites in clade A collagen chains.

Ion reactivity of calcium-deficient hydroxyapatite in standard cell culture media

Solution-mediated surface reactions occur for most calcium phosphate-based biomaterials and may influence cellular response. A reasonable extrapolation of such processes observed in vitro to in vivo performance requires a deep understanding of the underlying mechanisms. We therefore systematically investigated the nature of ion reactivity of calcium-deficient hydroxyapatite (CDHA) by exposing it for different periods of time to standard cell culture media of different chemical composition (DMEM and McCoy medium, with and without osteogenic supplements and serum proteins). Kinetic ion interaction studies of principal extracellular ions revealed non-linear sorption of Ca 2+ (∼50% sorption) and K + (∼8%) as well as acidification of all media during initial contact with CDHA (48 h). Interestingly, inorganic phosphorus (P i) was sorbed from McCoy medium (∼50%) or when using osteogenic media containing β-glycerophosphate, but not from DMEM medium. Non-linear sorption data could be perfectly described by pseudo-first-order and pseudo-second-order sorption models. At longer contact time (21 days), and with frequent renewal of culture medium, sorption of Ca 2+ remained constant throughout the experiment, while sorption of P i gradually decreased in McCoy medium. In great contrast, CDHA began to release P i slowly with time when using DMEM medium. Infrared spectra showed that CDHA exposed to culture media had a carbonated surface chemistry, suggesting that carbonate plays a key role in the ion reactivity of CDHA. Our data show that different compositions of the aqueous environment may provoke opposite ion reactivity of CDHA, and this must be carefully considered when evaluating the osteoinductive potential of the material.

Abstract 4410: Apoptosis in Ovarian Cancer Cells Induced by Polyclonal Antibodies to Secreted Frizzle-related Protein 2

Abstract Objectives: We have previously discovered a novel angiogenesis factor, secreted frizzle-related protein 2 (SFRP2), that is strongly expressed in many human tumors including ovarian carcinoma. SFRP2 protects against endothelial cell apoptosis, and induces endothelial tube formation and migration. We hypothesize that in addition to its paracrine role in stimulating angiogenesis, SFRP2 also has a direct effect in tumor cells, and therefore blocking SFRP2 will induce ovarian cancer apoptosis. Methods: Protein expression of SFRP2 in ovarian cancer cells: SKOV-3 and OVCA −3 ovarian cancer cells were cultured in McCoy's medium with 10% bovine serum albumin. Whole cell protein lysates were obtained and Western blot analysis was performed probing for SFRP2. Apoptosis assay: SKOV3 cells were plated in 96 well plates and allowed to attach overnight. Rabbit polyclonal antibody to SFRP2 (SFRP2 Ab) was run through a column with a saline buffer to remove the sodium azide preservative. Cells were treated with antibody in 1:10, 1:100, and 1:1000 concentrations. McCoy's culture medium with 1% saline was used as a negative control. Cells were incubated at 37°C for 48 hours. Apoptosis was measured by the activity of cleaved caspase-3 by using a caspase-specific fluorogenic substrate. Statistical analysis was performed with a two-tailed student's t-test. Results: SKOV-3 and OVCA-3 ovarian cancer cells strongly express SFRP2 on Western Blot analysis. When SKOV-3 cells were treated with polyclonal antibody to SFRP2 (1:10) there was a 47% increase in apoptosis as compared with negative controls (control = 1509 RFU ± 50, SFRP2 Ab =2221 RFU ± 39, n=4 for both groups, p&amp;lt;0.0001). Conclusions: SFRP2 is a protein endogenously expressed by ovarian carcinoma. Blocking SFRP2 with a polyclonal antibody induces apoptosis in SKOV-3 ovarian cancer cell line, suggesting that this protein may be a potential target in the treatment of ovarian cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4410.

Syndecan-2 Regulates the Migratory Potential of Melanoma Cells

Syndecan-2, a transmembrane heparan sulfate proteoglycan, is a critical mediator in the tumorigenesis of colon carcinoma cells. We explored the function of syndecan-2 in melanoma, one of the most invasive types of cancers, and found that the expression of this protein was elevated in tissue samples from both nevus and malignant human melanomas but not in melanocytes of the normal human skin tissues. Similarly, elevated syndecan-2 expression was observed in various melanoma cell lines. Overexpression of syndecan-2 enhanced migration and invasion of melanoma cells, whereas the opposite was observed when syndecan-2 levels were knocked down using small inhibitory RNAs. Syndecan-2 expression was enhanced by fibroblast growth factor-2, which is known to stimulate melanoma cell migration; however, alpha-melanocyte-stimulating hormone decreased syndecan-2 expression and melanoma cell migration and invasion in a melanin synthesis-independent manner. Furthermore, syndecan-2 overexpression rescued the migration defects induced by alpha-melanocyte-stimulating hormone treatment. Together, these data strongly suggest that syndecan-2 plays a crucial role in the migratory potential of melanoma cells.

Biodegradable Mg corrosion and osteoblast cell culture studies

Magnesium (Mg) is a biodegradable metal that has significant potential advantages as an implant material. In this paper, corrosion and cell culture experiments were performed to evaluate the biocompatibility of Mg. The corrosion current and potential of a Mg disk were measured in different physiological solutions including deionized (DI) water, phosphate-buffered saline (PBS), and McCoy's 5A culture medium. The corrosion currents in the PBS and in the McCoy's 5A-5% FBS media were found to be higher than in DI water, which is expected because corrosion of Mg occurs faster in a chloride solution. Weight loss, open-circuit potential, and electrochemical impedance spectroscopy measurements were also performed. The Mg specimens were also characterized using an environmental scanning electron microscope and energy-dispersive X-ray analysis (EDAX). The X-ray analysis showed that in the cell culture media a passive interfacial layer containing oxygen, chloride, phosphate, and potassium formed on the samples. U2OS cells were then co-cultured with a Mg specimen for up to one week. Cytotoxicity results of magnesium using MTT assay and visual observation through cell staining were not significantly altered by the presence of the corroding Mg sample. Further, bone tissue formation study using von Kossa and alkaline phosphatase staining indicates that Mg may be suitable as a biodegradable implant material.

Adsorption of fetal bovine serum on H/O-terminated diamond studied by atomic force microscopy

We investigate adsorption of fetal bovine serum (FBS), a crucial component for cell growth, on intrinsic CVD mono-crystalline diamond with hydrogen and oxygen surface terminations. The surface terminations are prepared by oxygen and hydrogen plasma process. The FBS adsorption is done by immersing diamond into McCoy's 5A medium supplemented with 15% FBS for 10 s–24 h. After rinsing the samples are characterized in the McCoy's medium and for comparison also in air by atomic force microscopy (AFM). By optimized measurements of AFM topography in oscillating regime and by using advanced AFM regimes such as phase imaging, nanoshaving, and force spectroscopy we characterize FBS thickness, adhesion, conformation and selectivity on the H/O-diamond surfaces. We find that FBS is adsorbed in about the same monolayer thickness (2–4 nm) on both H/O-diamond surfaces, yet the protein conformation is different. We present a schematic model.

Antitumor Effects of JBD57 in Human Multiple Myeloma Cells in Vitro

JBD57 is a nucleoside/nucleotide analogue that in human cells causes depletion of mitochondrial DNA by disrupting oxidative phosphorylation pathways leading to toxic accumulation of nonesterified fatty acids, dicarboxylic acids and free radicals. Human 26S proteasome is also a target for JBD57. Here we evaluated JBD57 citotoxicity in several human tumor cell lines in vitro. Human MM cell line RPMI 8226/S (CCL-155), human T-cell lymphoblastic-like (Jurkat) and human T-cell leukemia (1301) were grown in RPMI 1640 medium; uterine sarcoma (MES-S (CRL-1976) cells were grown in McCoy medium; HUV-EC-C (CRL-1730) cells were grown in 199/EBSS medium. Media were supplemented with 10 % FBS. Cells were incubated at 37°C in a water-jacketed incubator with 5 % CO2. To evaluate JBD57 citotoxicity in RPMI 8226/S, MES-S, Jurkat, 1301 and HUV-EC-C cells, 104cells/well were grown in flat-bottomed 96-well tissue culture plates for 24, 48 and 72 hr; JBD57 was added to the media in several concentrations (0μM, 32.25μM, 62.5μM, 125μM, 250μM and 500μM). At the end of the experimental periods, cell viability was determined by the MTT method. JBD57 inhibited the growth of MM cell line RPMI 8226/S in a dose- and time-dependent manner. Cell viability decreased progressively with increasing concentrations of JBD57 as well as with increasing time periods. The IC50 (inhibitory concentration at 50%) was 125 μM at 72 hr. The viability of the MM cells after 72 hr incubation with JBD57 500μM was 33%, whereas 100% viability was observed when no drug was added. On the other hand, JBD57 did not affect cell viability of any of the other studied cell lines (uterine sarcoma, Jurkat, 1301 and HUVEC-C). JBD57 promotes a significant human MM cell death in a dose and time dependent manner but do not affect neither normal cell HUV-EC-C nor the tumoral cells MES-S, Jurkat and 1301, at least in the studied conditions. These results suggest that the potent antitumoral activity of JBD57 observed against MM cells could be potentially useful in the treatment of multiple myeloma.

Chronic Treatment with Resveratrol Induces Redox Stress- and Ataxia Telangiectasia-mutated (ATM)-dependent Senescence in p53-positive Cancer Cells

The induction of senescence, an irreversible growth arrest, in cancer cells is regarded as a mean to halt tumor progression. The phytoalexin resveratrol (RV) is known to possess a variety of cancer-preventive, -therapeutic, and -chemosensitizing properties. We report here that chronic treatment with RV in a subapoptotic concentration induces senescence-like growth arrest in tumor cells. In contrast to the widely accepted antioxidant property of RV, we demonstrate that one causative stimulus for senescence induction by chronic RV is an increased level of reactive oxygen species (ROS). The ROS formed upon RV exposure include hydrogen peroxide and superoxide and originate largely from mitochondria. Consistently, co-incubation with the antioxidant N-acetyl cysteine interfered with RV-mediated reactivation of the senescence program. Molecular mediators on the way from increased ROS levels to the observed growth arrest include p38 MAPK, p53, and p21. Moreover, we provide evidence that RV-initiated replication stress, apparent by activation of the ataxia telangiectasia-mutated kinase pathway, is associated with increased ROS levels and senescence induction. This is the first report linking cell cycle effects with a pro-oxidant and pro-senescent effect of RV in cancer cells.

Identification of a Dominant Negative Functional Domain on DAPK-1 That Degrades DAPK-1 Protein and Stimulates TNFR-1-mediated Apoptosis

DAPK-1 is a stress-activated tumor suppressor protein that plays a role in both proapoptotic or antiapoptotic signal transduction pathways. To define mechanisms of DAPK-1 protein regulation, we have determined that DAPK-1 protein has a long half-life, and therefore its activity is primarily regulated at the protein level. Changes in DAPK-1 protein levels occur by a cathepsin B-dependent pathway, prompting us to evaluate whether cathepsin B plays positive or negative role in DAPK-1 function. The transfection of p55-TNFR-1 induced complex formation between DAPK-1 and cathepsin B. Depletion of cathepsin B protein using small interfering RNA stimulated TNFR-1 dependent apoptosis. The minimal binding region on DAPK-1 for cathepsin B was mapped to amino acids 836-947. The transfection of the DAPK-1-(836-947) miniprotein acted in a dominant negative manner inducing endogenous DAPK-1 protein degradation in a TNFR-1-dependent manner. These data suggest that DAPK-1 forms a multiprotein survival complex with cathepsin B countering the rate of TNFR-1-dependent apoptosis and highlights the importance of developing DAPK-1 inhibitors as agents to sensitize cells to stress-induced apoptosis.

Coordinate Suppression of ERBB2 and ERBB3 by Enforced Expression of Micro-RNA miR-125a or miR-125b

Deregulation of micro-RNAs (miRNAs) is emerging as a major aspect of cancer etiology because their capacity to direct the translation and stability of targeted transcripts can dramatically influence cellular physiology. To explore the potential of exogenously applied miRNAs to suppress oncogenic proteins, the ERBB oncogene family was chosen with a bioinformatics search identifying targeting seed sequences for miR-125a and miR-125b within the 3'-untranslated regions of both ERBB2 and ERBB3. Using the human breast cancer cell line SKBR3 as a model for ERBB2 and ERBB3 dependence, infection of these cells with retroviral constructs expressing either miR-125a or miR-125b resulted in suppression of ERBB2 and ERBB3 at both the transcript and protein level. Luciferase constructs containing the 3' 3'-untranslated regions of ERBB2 and ERBB3 demonstrated approximately 35% less activity in miR-125a- and miR-125b-expressing cells relative to controls. Additionally, phosphorylation of ERK1/2 and AKT was suppressed in SKBR3 cells overexpressing either miR-125a or miR-125b. Consistent with suppression of both ERBB2 and ERBB3 signaling, miR-125a-or miR-125b-overexpressing SKBR3 cells were impaired in their anchorage-dependent growth and exhibited reduced migration and invasion capacities. Parallel studies performed on MCF10A cells demonstrated that miR-125a or miR-125b overexpression produced only marginal influences on the growth and migration of these non-transformed human mammary epithelial cells. These results illustrate the feasibility of using miRNAs as a therapeutic strategy to suppress oncogene expression and function.