Investigation and Control of Strain-Induced Spin-Dependent Current in a DNA Chain: A Piezospintronic Approach.

Molecular systems are good candidates for designing the novel generation of nanoelectronic and nanospintronic devices due to their flexible structures. We have theoretically investigated stain-induced spin transport through a DNA chain to control a piezospintronic component. In the current modeling, we have applied a small strain to a tilted DNA chain connected between two leads and immersed it in a heat bath. The results show that a compressing strain can enhance the spin-dependent current up to 300 nA. Via modulating the control parameters, one can control the spin transport characteristic of a DNA-based material for designing an information storage and transport device.

Light-Driven Modulation of Electrical Current through DNA Sequences: Engineering of a Molecular Optical Switch.

Designing a molecular switch with bistable on/off states is of particular interest in molecular electronics. Motivated by experimental studies of molecular conductors, interplays of photons and electrons and their effects on electrical properties are studied theoretically. We have tried to model a molecular optical switch based on DNA sequences of the hepatitis delta virus and Toxocara canis parasite. The electrical response of chains to the light irradiation was examined to optimize the function of an optical switch. The switch turns on when the amplitude of incident irradiation and its frequency approach to 0.3 at the unit of (ℏc)/(er0) and 2 THz, respectively. We can modulate the switching of the system via the simultaneous variation of effective factors and obtain different islands in the parameter settings. The appearance of different islands in the parameter surface relates to the on/off states of electrical current, which can be verified and estimated through the multifractal analysis.

A ratiometric probe based on Ag2S quantum dots and graphitic carbon nitride nanosheets for the fluorescent detection of Cerium.

Using silver sulfide quantum dots (Ag2S) and graphitic carbon nitride nanosheets (g-C3N4), an effective and facile ratiometric fluorescence sensor for the selective determination of Cerium was developed. The addition of cerium to this probe solution resulted in the fluorescence at 443 nm quenching, while the fluorescence of the Ag2S QDs at 540 nm recovering. The linear response range of this ratiometric sensor for Cerium was from 0.5 × 10 -6 mol L-1 to 3.2 × 10 -5 mol L-1. In this sensing system, not only was the detection limit as low 6.4 × 10 -8 mol L-1, which was as good or better than similar assays, but the sensing system also demonstrated good selectivity in detecting cerium in the presence of interfering substances. The possible mechanism is discussed. Furthermore, this ratiometric fluorescence probe was successfully employed for the detection of Cerium in real samples with satisfactory results. The results were compared with those obtained using inductively coupled plasma optical emission spectrometry (ICP-OES).

A short-term colorectal cancer sphere culture as a relevant tool for human cancer biology investigation.

BACKGROUND: Ex vivo colospheres have been previously characterised as a colorectal cancer (CRC) well-rounded multicellular model, exclusively formed by carcinoma cells, and derived from fresh CRC tissue after mechanical dissociation. The ability to form colospheres was correlated with tumour aggressiveness. Their three-dimensional conformation prompted us to further investigate their potential interest as a preclinical cancer tool. METHODS: Patient-derived CRC xenografts were used to produce numerous colospheres. Mechanism of formation was elucidated by confocal microscopy. Expression analysis of a panel of 64 selected cancer-related genes by real-time qRT-PCR and hierarchical clustering allowed comparison of colospheres with parent xenografts. In vitro and in vivo assays were performed for migration and chemosensitivity studies. RESULTS: Colospheres, formed by tissue remodelling and compaction, remained viable several weeks in floating conditions, escaping anoikis through their strong cell-cell interactions. Colospheres matched the gene expression profile of the parent xenograft tissue. Colosphere-forming cells migrated in collagen I matrix and metastasised when subrenally implanted in nude mice. Besides, the colosphere responses to 5-fluorouracil and irinotecan, two standard drugs in CRC, reproduced those of the in vivo original xenografts. CONCLUSION: Colospheres closely mimic biological characteristics of in vivo CRC tumours. Consequently, they would be relevant ex vivo CRC models.

Effect of sildenafil (Viagra) on memory retention of a passive avoidance response in rats.

The effects of an intraperitoneal (i.p.) injection of different doses of sildenafil, a cyclic guanosin monophosphate (cGMP) specific phosphodiesterase type 5 (PDE 5) inhibitor, on memory retention of young (2-month-old) and middle aged (12-month-old) male Wistar rats were investigated. Passive avoidance behaviour was studied in a one trial learning, step--through type, passive avoidance task utilizing the natural preference of rats for a dark environment. In each category (young or middle-aged) different groups of rats received vehicle or sildenafil (1, 3, 10, 20 mg*kg(-1), i.p.) immediately after training and one group remained uninjected serwing as control. Retention latencies were measured 48 h later. To asses a possible non-specific proactive effect of sildenafil, the response latencies in a group of rats not receiving foot shock were also tested. The results showed that the post-training i.p. administration of sildenafil did not facilitate retention performance of a passive avoidance response in both young and middle aged rats compared to control or vehicle groups. Also, sildenafil did not affect response latencies in rats not having received the footshock on the training trial, indicating that sildenafil does not show a non-specific proactive affect on retention performance. The comparison of retention time between young and middle aged rats showed that the memory of the latter had been significantly reduced. In conclusion, this study suggests that sildenafil has no effects on memory retention in Wistar rats.

Ex vivo expansion of megakaryocyte precursor cells in autologous stem cell transplantation for relapsed malignant lymphoma.

To evaluate the impact of ex vivo expanded megakaryocyte (MK) progenitors on high-dose chemotherapy-induced thrombocytopenia, we conducted a phase II study in 10 patients with relapsed lymphoma. Two fractions of peripheral blood progenitor cells (PBPC) were cryopreserved, one with enough cells for at least 2 x 10(6) CD34+ cells/kg and a second obtained after CD34+ selection. Ten days before autologous stem cell transplantation, the CD34+ fraction was cultured with MGDF+SCF for 10 days. After BEAM (BCNU, cyclophosphamide, cytarabine, and melphalan) chemotherapy, patients were reinfused with standard PBPC and ex vivo expanded cells. No toxicity was observed after reinfusion. The mean fold expansion was 9.27 for nucleated cells, 2 for CD34+ cells, 676 for CD41+ cells, and 627 for CD61+ cells. The median date of platelet transfusion independence was day 8 (range: 7-12). All patients received at least one platelet transfusion. In conclusion, ex vivo expansion of MK progenitors was feasible and safe, but this procedure did not prevent BEAM-induced thrombocytopenia. Future studies will determine if expansion of higher numbers of CD34+ cells towards the MK-differentiation pathway will translate into a functional effect in terms of shortening of BEAM-induced thrombocytopenia.

Distinct experimental efficacy of anti-Fas/APO-1/CD95 receptor antibody in human tumors.

Ligation of the Fas receptor (FasR) is a key step in apoptosis induction. Using a series of human tumor cells (SNB19, SNB79, 143N2, and SHEP), we observed a distinct efficacy of human anti-FasR antibody with an apparent correlation with Fas cell surface antigen expression. In contrast, all cells studied expressed detectable FasR mRNA transcripts. For all anti-FasR antibody-sensitive tumor cells, we showed a similar efficacy of Mab according to dose fractionation and injection site. We showed that, when injected into nude mice bearing human osteosarcoma 143N2, neuroblastoma SHEP, prostatic cancer PAC120, and the two glioblastomas SNB19 and SNB79, anti-FasR Mab induces significant inhibition of the growth rate of 143N2, SHEP, and PAC120 tumors, but has no efficacy on SNB19 and SNB79 tumors, with a relationship between in vitro and in vivo sensitivity to anti-FasR antibody. Altogether, these results suggest the antitumor potential of anti-FasR antibody in human neoplasms.

Clinical and experimental progression of a new model of human prostate cancer and therapeutic approach.

We report the clinical evolution of a prostate cancer, metastasizing to lungs and bones, recurring locally, and escaping from anti-androgen therapy. Key event of biological progression of the patient's tumor was the coincidence of allelic imbalance accumulation and of bone metastases occurrence. The recurrent tumor was established as the transplantable xenograft PAC120 in nude mice, where it grew locally. PAC120 displayed the same immunophenotype of the original tumor (positive for keratin, vimentin, prostatic acid phosphatase, and Leu-7) and expressed human HOXB9, HOXA4, HER-2/neu, and prostate-specific antigen genes, as detected by reverse transcriptase-polymerase chain reaction. It formed lung micrometastases detected by mRNA expression of human genes. Cytogenetic analysis demonstrated numerous alterations reflecting the tumor evolution. PAC120 was still hormone-dependent; its growth was strongly inhibited by the new gonadotropin-releasing hormone antagonist FE 200486 but weakly by gonadotropin-releasing hormone superagonist D-Trp(6)-luteinizing-hormone releasing hormone (decapeptyl). Tumor growth inhibition induced by anti-hormone therapy was linked to the hormone deprivation degree, more important and more stable with FE 200486 than with D-Trp(6)-luteinizing-hormone releasing hormone. Surgical castration of mice led to tumor regressions but did not prevent late recurrences. Transition to hormone-independent tumors was frequently associated with a mucoid differentiation or with a neuroendocrine-like pattern. Independent variations of mRNA expression of HER-2/neu and prostate-specific antigen were observed in hormone-independent tumors whereas HOXB9 gene expression was constant. In conclusion, PAC120 xenograft, a new model of hormone-dependent prostate cancer retained the progression potential of the original tumor, opening the opportunity to study the hormone dependence escape mechanism.

Distinctive potentiating effects of cisplatin and/or ifosfamide combined with etoposide in human small cell lung carcinoma xenografts.

Combined modalities are currently used for cancer therapy, although their mechanisms of activity remain incompletely deciphered. The design of new drug combinations suffers from our inability to anticipate accurately their efficacy or toxicity. They can be evaluated in vivo, using human tumors grafted into immunodeficient mice, as we did here with combined protocols used in the clinical setting. Xenografts of small cell lung carcinoma (SCLC) from eight patients were used to test the tumor sensitivity to etoposide (VP16; 12-16 mg/kg/days, days 1, 2, and 3), cisplatin (CDDP; 6-9 mg/kg/day, day 1) and ifosfamide (IFO; 90-210 mg/kg/day, days 1, 2, and 3) as single agents and to evaluate the efficacy of the two-drug or three-drug combinations. Five xenografts came from untreated patients (SCLC-61, SCLC-6, SCLC-10, SCLC-41, and SCLC-96) and three after treatment (SCLC-74, SCLC-101, and SCLC-108). p53 was inactivated in all of them. Tumor growth inhibition, growth delay, and the survival rate of tumor-bearing mice reflected individual SCLC chemosensitivity. As single agents, IFO inhibited tumor growth in a dose-dependent manner, whereas CDDP and VP16 had little or no effect. Both CDDP and IFO potentiated VP16, inducing complete regressions in the most sensitive SCLCs; VP16-IFO was more effective than VP16-CDDP, with complete regressions in six versus three of the eight tumors tested, respectively. CDDP-IFO was less effective than VP16-IFO, with three of eight SCLCs giving complete regressions. The three-drug combination led to modest improvement over the best two-drug combination but only for sensitive SCLCs. Because drug-responses distinguished two classes of SCLCs, as sensitive or refractory, MDR1, glutathione S-transferase pi, lung-related multidrug resistance protein, multidrug resistance protein, and topoisomerase IIalpha mRNA expression was studied by semiquantitative reverse transcription. There was no correlation with SCLC sensitivity; topoisomerase IIalpha and multidrug resistance protein was expressed in all cases, lung-related multidrug resistance protein and glutathione S-transferase pie in seven of eight, and MDR1 gene in four of eight. In conclusion, these SCLC xenografts displayed a pattern of chemotherapy response close to that observed in patients. This model confirmed that in two-drug combinations, each component potentiated the effects of the other, with VP16-IFO tending to be the best two-drug combination, both of which were more effective than VP16-CDDP and better tolerated than CDDP-IFO. The addition of a third agent gave a modest, if any, therapeutic benefit in the responders but none in refractory SCLCs. There was no correlation between the extent of response and resistance markers.

Ability of doxorubicin-loaded nanoparticles to overcome multidrug resistance of tumor cells after their capture by macrophages.

PURPOSE: Investigation of the ability of doxorubicin-loaded nanoparticles (NP/Dox) to overcome multidrug resistance (MDR) when they have first been taken up by macrophages. METHODS: The growth inhibition of P388 sensitive (P388) and resistant (P388/ADR) tumor cells was evaluated in a coculture system consisting of wells with two compartments. The tumor cells were seeded into the lower compartment, the macrophages were introduced into the upper part in which the drug preparations were also added. RESULTS: Doxorubicin exerted lower cytotoxicity on tumor cells in coculture compared with direct contact. In P388/ADR, NP/Dox cytotoxicity was far higher than that of free doxorubicin (Dox). Three different formulations of cyclosporin A (either free (CyA), loaded to nanoparticles (NP/CyA) or in a combined formulation with doxorubicin (NP/Dox-CyA)), were added to modulate doxorubicin efficacy. The addition of cyclosporin A to Dox increased drug cytotoxicity. Both CyA added to NP/Dox and NP/Dox-CyA were able to bypass drug resistance. CONCLUSIONS: Despite the barrier role of macrophages, NP/Dox remained far more cytotoxic than Dox against P388/ADR. Both NP/Dox + CyA and NP/Dox-CyA allowed to overcome MDR, but the last one should present greater advantage in vivo by confining both drugs in the same compartment, hence reducing the adverse effects.

Antitumoral effects of squamocin on parental and multidrug resistant MCF7 (human breast adenocarcinoma) cell lines.

The antiproliferative effects of squamocin, one of the easiest annonaceous acetogenins to obtain, were studied in the parental (MCF7-S) and the multidrug resistant (MCF7-R) human breast adenocarcinoma cell lines. Squamocin inhibited proliferation of both cell lines identically, by blocking the cell cycle in the G1-phase. This inhibition was reversible in the long term. Squamocin decreased the ATP pool in both MCF7 cell lines, but did not seem to induce apoptosis. Cytotoxic activity of adriamycin was not restored in MCF7-R Pgp expressing cells by squamocin addition.

Synthesis of self-immolative glucuronide-based prodrugs of a phenol mustard.

The design and synthesis of the mustard pro-prodrugs which can be used in ADEPT is reported. Prodrugs 1 and 2 include a glucuronide group which is connected to the drug via an aromatic and/or aliphatic bis-carbamate spacer. The design of these new prodrugs takes advantage of a spontaneous 1,6-elimination and/or an intramolecular cyclization reaction after enzymatic cleavage. Thus, enzymatic-catalyzed hydrolysis of the glucuronyl moiety of 1 by Escherichia coli beta-glucuronidase results in the liberation of the parent mustard drug 20 with formation of CO2, 2-nitro-4-hydroxymethylphenol 19 and dimethylimidazolidinone 21. Surprisingly, prodrug 2 was not cleaved under the same conditions. According to in vitro experiments, prodrugs 1 and 2 were approximately 50- and 80-fold less cytotoxic than the parent drug and, when treated with beta-glucuronidase, the level of cytotoxic activity of 1 became comparable to that of the drug. Stability of 1 in phosphate buffer was satisfactory. These results demonstrate that 1 is a prodrug that can be specifically activated to release the cytotoxic agent.

Reversion of multidrug resistance with polyalkylcyanoacrylate nanoparticles: towards a mechanism of action.

Polyalkylcyanoacrylate (PACA) nanoparticles loaded with doxorubicin allowed multidrug resistance to be overcome in vitro. However, increased cytotoxicity is not always correlated with an increased level of intracellular drug. Although we have previously shown that PACA nanoparticles are not endocytosed by tumour cells, we report here that a direct interaction between nanoparticles and cells is a necessary requirement for overcoming resistance. In addition, the results showed that the degradation products of PACA (mainly polycyanoacrylic acid) in the presence of doxorubicin are able to increase both accumulation and cytotoxicity, thus suggesting the formation of a doxorubicin-polycyanoacrylic acid ion pair. It is therefore concluded that resistance is overcome as a result of both the adsorption of nanoparticles to the cell surface and increased doxorubicin diffusion by the accumulation of an ion pair at the plasma membrane.

Uptake of doxorubicin from loaded nanoparticles in multidrug-resistant leukemic murine cells.

Previous studies have clearly demonstrated that polyisobutylcyanoacrylate (PIBCA) doxorubicin-loaded nanoparticles (NS-Dox PIBCA) can overcome the resistance of P388/ADR cells. In the present paper, we found that overcoming multidrug resistance with the aid of doxorubicin (Dox) loaded onto these nanoparticles was associated with an increased intracellular drug content. Indeed, after a 6-h incubation period, the amount of cell-associated drug was 5 times higher when the cells were incubated with NS-Dox PIBCA as compared with free Dox. Further experiments, such as uptake studies in the presence of cytochalasin B or efflux studies, indicated a possible mechanism of nanoparticle/cell interaction. These results suggested that nanoparticles did not enter the cells by an endocytic process, in contrast to a previous hypothesis.

Experience with doxorubicin-bound polyisohexylcyanoacrylate nanoparticles on murine alveolar echinococcosis of the liver.

The parasiticidal properties of doxorubicin against the metacestode of Echinococcus multilocularis were investigated after binding of that drug to polyisohexylcyanoacrylate nanoparticles, a colloidal biodegradable drug carrier. A reduction of the hepatic parasite development and a reduced viability of the metacestode were observed in mice injected with 5 mg kg-1 body weight-1, but 7.5 mg kg-1 body weight-1 did not appear more efficient. Free doxorubicin or unbound nanoparticles had no antiparasitic activity.