Successful Partnerships: Exploring the Potential of Immunogenic Signals Triggered by TMZ, CX-4945, and Combined Treatment in GL261 Glioblastoma Cells.

BACKGROUND: The relevance of the cancer immune cycle in therapy response implies that successful treatment may trigger the exposure or the release of immunogenic signals. Previous results with the preclinical GL261 glioblastoma (GB) showed that combination treatment of temozolomide (TMZ) + CX-4945 (protein kinase CK2 inhibitor) outperformed single treatments, provided an immune-friendly schedule was followed. Our purpose was to study possible immunogenic signals released in vitro by GB cells. METHODS: GL261 GB cells were treated with TMZ and CX-4945 at different concentrations (25 µM-4 mM) and time frames (12-72 h). Cell viability was measured with Trypan Blue and propidium iodide. Calreticulin exposure was assessed with immunofluorescence, and ATP release was measured with bioluminescence. RESULTS: TMZ showed cytostatic rather than cytotoxic effects, while CX-4945 showed remarkable cytotoxic effects already at low concentrations. Calreticulin exposure after 24 h was detected with TMZ treatment, as well as TMZ/CX-4945 low concentration combined treatment. ATP release was significantly higher with CX-4945, especially at high concentrations, as well as with TMZ/CX-4945. CONCLUSIONS: combined treatment may produce the simultaneous release of two potent immunogenic signals, which can explain the outperformance over single treatments in vivo. A word of caution may be raised since in vitro conditions are not able to mimic pharmacokinetics observed in vivo fully.

Gated Mesoporous Silica Nanocarriers for a "Two-Step" Targeted System to Colonic Tissue.

Colon targeted drug delivery is highly relevant not only to treat colonic local diseases but also for systemic therapies. Mesoporous silica nanoparticles (MSNs) have been demonstrated as useful systems for controlled drug release given their biocompatibility and the possibility of designing gated systems able to release cargo only upon the presence of certain stimuli. We report herein the preparation of three gated MSNs able to deliver their cargo triggered by different stimuli (redox ambient (S1), enzymatic hydrolysis (S2), and a surfactant or being in contact with cell membrane (S3)) and their performance in solution and in vitro with Caco-2 cells. Safranin O dye was used as a model drug to track cargo fate. Studies of cargo permeability in Caco-2 monolayers demonstrated that intracellular safranin O levels were significantly higher in Caco-2 monolayers when using MSNs compared to those of free dye. Internalization assays indicated that S2 nanoparticles were taken up by cells via endocytosis. S2 nanoparticles were selected for in vivo tests in rats. For in vivo assays, capsules were filled with S2 nanoparticles and coated with Eudragit FS 30 D to target colon. The enteric coated capsule containing the MSNs was able to deliver S2 nanoparticles in colon tissue (first step), and then nanoparticles were able to deliver safranin O inside the colonic cells after the enzymatic stimuli (second step). This resulted in high levels of safranin O in colonic tissue combined with low dye levels in plasma and body tissues. The results suggested that this combination of enzyme-responsive gated MSNs and enteric coated capsules may improve the absorption of drugs in colon to treat local diseases with a reduction of systemic effects.

MUC1 aptamer-capped mesoporous silica nanoparticles for controlled drug delivery and radio-imaging applications.

Mucin 1 (MUC1) is a cell surface protein overexpressed in breast cancer. Mesoporous silica nanoparticles (MSNs) loaded with safranin O, functionalized with aminopropyl groups and gated with the negatively charged MUC1 aptamer have been prepared (S1-apMUC1) for specific targeting and cargo release in tumoral versus non-tumoral cells. Confocal microscopy studies showed that the S1-apMUC1 nanoparticles were internalized in MDA-MB-231 breast cancer cells that overexpress MUC1 receptor with subsequent pore opening and cargo release. Interestingly, the MCF-10-A non-tumorigenic breast epithelial cell line that do not overexpress MUC1, showed reduced (S1-apMUC1) internalization. Negligible internalization was also found for S1-ap nanoparticles that contained a scrambled DNA sequence as gatekeeper. S2-apMUC1 nanoparticles (similar to S1-apMUC1 but loaded with doxorubicin) internalized in MDA-MB-231 cells and induced a remarkable reduction in cell viability. Moreover, S1-apMUC1 nanoparticles radio-labeled with 99mTc (S1-apMUC1-Tc) showed a remarkable tumor targeting in in vivo studies with MDA-MB-231 tumor-bearing Balb/c mice.

New phenazine analogues from Streptomyces sp. IFM 11694 with TRAIL resistance-overcoming activities.

Two new phenazine derivatives, aotaphenazine (1) and 5,10-dihydrophencomycin (2), were isolated from the ethyl acetate extract of Streptomyces sp. IFM 11694. In addition, the known 1-phenazinecarboxylic acid (3), phencomycin (4) and 1,6-phenazinedicarboxylic acid (5) were identified. The structures of the isolated compounds (1-5) were characterized by spectroscopic methods including NMR and mass spectrometry data. Compound 1 showed the ability to overcome tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance at concentration of 12.5 µM. Aotaphenazine (1) enhanced the levels of apoptosis inducing proteins DR4, DR5, p53 and also decreased the levels of cell survival protein Bcl-2 in TRAIL-resistant human gastric adenocarcinoma (AGS) cells in a dose-dependent manner.

In vitro antiproliferative and apoptosis-inducing properties of a mononuclear copper(II) complex with dppz ligand, in two genotypically different breast cancer cell lines.

In the background that there is concerted effort to discover newer metal-based cancer chemotherapeutic agents that could overcome the limitations in cisplatin and that copper, a biocompatible and redox-active metal, offers potential as alternative to cisplatin, the present study was undertaken to investigate the in vitro anti-proliferative properties of the mononuclear copper(II)complex [Cu(L)(diimine)] + where LH = 2-[(2-dimethylaminoethylimino)methyl]phenol and diimine = dipyrido[3,2-a:2',3'-c]phenazine (dppz) using breast cancer cell lines MCF-7 (ER(+ve) and p53(WT)) and MDA-MB-231(ER(-ve) and p53(mutant)) when cisplatin was used as positive control. The complex affected the viability of both the cell lines in dose-as well as duration-dependent manner as revealed in the MTT assay. The 24 and 48 h IC50 of the complex were several times lesser than those of cisplatin, and within this huge difference the efficacy of the complex was much superior with MCF-7 cell compared to MDA-MB-231 cell. The cell death was preferentially apoptosis, though necrosis also occurred to a certain extent. These inferences were substantiated by AO/EB fluorescent staining, Hoechst staining, assessment of mitochondrial transmembrane potential, comet assay for DNA damage, DCFH assay for reactive oxygen species (ROS) generation and Western blot of apoptosis-related proteins. Thus, the copper(II) dppz complex under investigation is much more efficient than cisplatin in affecting viability of the breast cancer cells. The underlying mechanism appears to be DNA damage-primed (in view of the known intercalation mode of binding of the complex with DNA) and ROS-associated mitochondria-mediated intrinsic apoptosis to a great extent but necrosis also has a role to a certain extent, which may also be a PARP-mediated cell death independent of apoptosis. Within the purview of this conclusion, the results indicate that the ER and/or p53 genotypes have a bearing on the efficacy of the complex as a cytotoxic agent since the response in the ER(-ve) and p53(mutant) MDA-MB-231 cell was not so prominent as in ER(+ve) and p53(WT) MCF-7 cell. Taken together, the complex has been shown to be a potential DNA damaging agent and, in the light of the superiority of the complex over cisplatin, we are further investigating the possibility of targeted nano-delivery of the complex to the tumor cells. When tested on a normal cell, 3T3, Cu(II)dppz was found to affect its viability but at concentrations very high compared to those for the breast cancer cells. Yet, this is a cause of concern and, therefore, we are working out a strategy for targeted delivery of this complex to the cancer cells only.

Preclinical anti-tumor activity of XR5944 in combination with carboplatin or doxorubicin in non-small-cell lung carcinoma.

XR5944 (MLN944) is a novel bis-phenazine currently in phase I clinical trials that has demonstrated potent cytotoxic activity against a variety of tumor models. The combinations of XR5944 with carboplatin or doxorubicin were investigated in COR-L23/P human non-small-cell lung carcinoma (NSCLC) cells in vitro and the corresponding xenografts in vivo. In vitro cytotoxicity was evaluated by the sulforhodamine B assay and the drug interactions following simultaneous or sequential exposure were determined using median-effect analysis to calculate combination indices (CIs). XR5944 demonstrated potent cytotoxicity compared to either carboplatin or doxorubicin in COR-L23/P cells. Simultaneous or sequential exposure of XR5944 followed by carboplatin led to a synergistic response (CI<1), whereas the reverse order of addition showed an additive or antagonistic response (CI< or =1). Sequential administration of doxorubicin followed by XR5944 demonstrated marginally improved cytotoxicity (CI=1.31-0.77) than other schedules (CI=1.50-1.22) relative to individual drugs. Anti-tumor activity against COR-L23/P xenografts in nude mice was enhanced by administration of XR5944 (2 or 5 mg/kg) immediately before carboplatin (50 mg/kg) compared to single-agent treatment at the same doses. Improved efficacy was also observed by sequential administration of 7 mg/kg doxorubicin 48 h before 2.5 or 5 mg/kg XR5944. No additional toxicity was observed with combinations compared to single-agent treatment alone as determined by body weights. These data suggest that combinations of XR5944 with carboplatin or doxorubicin are of significant interest for clinical use, and that the schedule of administration may be important for achieving clinical efficacy over single-agent therapy.

Ex vivo characterization of XR11576 (MLN576) against ovarian cancer and other solid tumors.

XR11576 (MLN576) is a novel monophenazine with a mechanism of action that includes interaction with both topoisomerase (Topo) I and II. The aim of this study was to evaluate its cytotoxicity against fresh tumor cells taken from patients with a variety of solid tumors. Cells were obtained from 89 patients and exposed for 6 days to XR11576 alone, or in combination with doxorubicin, cisplatin, treosulfan, paclitaxel or vinorelbine. Cell survival was measured using the ATP-Tumor Chemosensitivity Assay (ATP-TCA). Immunohistochemical staining of Topo I, Topo IIalpha and MDR1 was performed on paraffin-embedded blocks in those tumors for which tissue was available (n = 49). Overall, the median IC90 and IC50 values of XR11576 in tumor-derived cells were 242 and 110 nM, respectively. In all samples XR11576 was more potent than the other cytotoxics tested. Breast and gynecological malignancies were most sensitive to XR11576, while the potency of this compound was slightly attenuated in gastrointestinal tumors, in which the median IC90 and IC50 values were 308 and 212 nM, respectively. Cases of synergism were identified when combining XR11576 with vinorelbine (nine of 30 samples) and doxorubicin (12 of 38 samples), while the addition of paclitaxel resulted in an antagonistic effect (CI50>1.2) in 38 of 42 tumors. A very modest correlation by linear regression analysis was found between the intensity of MDR1 staining and the IC50 of XR11576 (r = 0.311, p = 0.0312), but not with the IC90 (r = 0.247, NS). These data support the rapid introduction of XR11576 to clinical trials and suggest that it may be effective against a broad spectrum of tumor types.

In vitro and in vivo characterization of XR11576, a novel, orally active, dual inhibitor of topoisomerase I and II.

XR11576, a novel phenazine, was developed as an inhibitor of both topoisomerase I and II. This study characterized the ability of XR11576 to inhibit both enzymes, and determined its in vitro and in vivo antitumor efficacy against a number of murine and human tumor models. XR11576 was a potent inhibitor of purified topoisomerase I and IIalpha, and exhibited similar potency for both enzymes. The compound stabilized enzyme-DNA cleavable complexes indicating that it acted as a topoisomerase poison. The DNA cleavage patterns obtained with XR11576 were different from those induced by camptothecin and etoposide, which are topoisomerase I and II poisons, respectively. XR11576 demonstrated potent cytotoxic activity against a variety of human and murine tumor cell lines (IC50=6-47 nM). Its activity profile was comparable to or better than that of many widely used anticancer drugs. Moreover, XR11576 was unaffected by multidrug resistance (MDR) mediated by overexpression of either P-glycoprotein or MDR-associated protein, or by down-regulation of topoisomerase II. The latter property supports the dual inhibitory mechanism of action of the compound. XR11576 exhibited a similar pharmacokinetic profile in mice and rats after either i.v. or p.o. administration. In vivo XR11576 showed marked efficacy against a number of tumors including sensitive (H69/P) and multidrug-resistant (H69/LX4) small cell lung cancer and the relatively refractory MC26 and HT29 colon carcinomas following i.v. and p.o. administration. The efficacy of XR11576 was at least comparable to that of TAS-103, originally proposed as a dual inhibitor of topoisomerase I and II. These results suggest that XR11576 is a promising new antitumor agent with oral and i.v. activity, and warrants further development.

A novel antitumor compound, NC-190, induces topoisomerase II-dependent DNA cleavage and DNA fragmentation.

A novel benzophenazine derivative, NC-190, is a potent antitumor compound. NC-190 has been shown to inhibit the DNA strand-passing activity of DNA topoisomerase II. We investigated further the mode of action of NC-190 against DNA topoisomerase II and DNA fragmentation. NC-190 inhibited the decatenation activity of purified topoisomerase II, but had only a weak inhibitory effect against topoisomerase I. A topoisomerase II-dependent DNA cleavage assay showed that NC-190 inhibited the enzyme activity by stabilizing a topoisomerase II-DNA cleavable complex. NC-190 induced growth inhibition, protein-linked DNA breaks, and DNA fragmentation in cultured HL-60 cells in a dose-dependent manner. These activities of NC-190 in HL-60 cells were comparable to those of etoposide (VP-16). These results demonstrate a good correlation among growth inhibition, topoisomerase II-dependent DNA cleavage, and DNA fragmentation induced by NC-190. A DNA unwinding assay showed that NC-190 had intercalating activity, but its activity appeared to be weaker than those of ethidium bromide and adriamycin. These results indicate that the mechanism by which NC-190 exhibits antitumor activity may be the inhibition of topoisomerase II.