ALBERT

Description: Abstract 3969 Objective: Although many strategies have been explored to overcome the multidrug resistance (MDR) in leukemia which has rendered many currently available chemotherapeutic drugs ineffective, the results have been disappointing to the obstacle. The aim of this study was to investigate whether the new strategy of combining drug-loaded nanoparticles (Nps) and ultrasound (US) would show useful effects on the reversal of MDR in human leukemia cell line K562/A02. Methods: In this study, daunorubicin (DNR), a frequently chemotherapeutic agent known to cause DNA damage and induce apoptosis and cell death, was loaded on the TiO2 Nps which is chemically stable, environmental friendly, and shows weak or non cytotoxic to apply as the nano-drug carrier. The MDR leukemia K562/A02 cells were treated with the DNR-loaded TiO2 Nps drug carrier and US exposure. Then, we examined the effectiveness of delivering DNR into the MDR leukemia K562/A02 cells with the electrochemical studies, observed the bio-effects on the cell viability by MTT assays, investigated the induced apoptosis, and assessed the reversal ability and the mechanism of MDR by combining the drug-loaded Nps and US. Results: We observed good biocompatibility of the therapeutic approach. When the K562/A02 cells were incubated with DNR only, the cathodic current decreased by only 10% normalized to the DNR (10 μg/mL) standard, indicating less DNR was absorbed by the MDR cells. The cathodic current decreased by 39% and 63% in the presence of US or DNR-loaded TiO2 Nps, respectively. In comparison, when the cells were treated by the novel strategy of US mediated drug-loaded Nps crossing cell membranes, the cathodic current of DNR in the supernatant decreased greatly by 82% and became the minimal, which suggesting the least amount of DNR remained outside the MDR cells in this case and the largest uptake into the cells by this new strategy. These observations demonstrated that the remarkable synergistic effect of the novel strategy facilitated the accumulation of DNR in the MDR K562/A02 cells. In addition, our MTT assay illustrated comparative sensitization of the MDR K562/A02 cells under the treatment of US or drug-loaded Nps, but especially enhanced effect by combining drug-loaded Nps and US. The resisting fold of the MDR leukemia K562/A02 became obviously lower, decreasing from 58.71 to 16.69. The fresh evidence from caspase-3 immunocytochemistry demonstrated that the strategy could induce the apoptosis in the cells as well. Conclusion: It was therefore concluded that the strategy could have good reversal ability of MDR in tumor. These findings reveal that the reversal of MDR in tumor by US mediated drug-loaded Nps crossing cell membranes could represent promising approach in cancer therapy. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 3479 Daunorubicin (DNR) with a broad spectrum of anti-tumor activity is limited due to the serious side-effects in the clinical application. The aim of this study was to explore the novel pH-responsive drug delivery system (DDS) based on titanium dioxide (TiO2) nanoparticles (Nps) for its potential roles to enable more intelligently controlled release, enhance chemotherapeutic efficiency, and reduce the side-effects of DNR. DNR was loaded onto the TiO2 Nps by forming (six-membered chelate) complexes with transition metal Ti to contract DNR-TiO2 nanocomposites as DDS. The encapsulation efficiency and loading efficiency of DNR loaded TiO2 Nps were assessed and calculated as 65.46±6.82% and 20.63±3.55%, respectively.The DNR was released from the DDS much more rapidly at pH 5.0 and 6.0 than at pH 7.4. The release behavior is a desirable characteristic for tumor-targeted drug delivery. Most DNR will remain in the carrier for a considerable time period at normal physiological conditions (pH 7.4), indicating the potential for the prolonged DNR retention time in the blood circulation and thereby greatly reducing the side effects to the normal tissues. On the other hand, once the DNR loaded TiO2 Nps are taken up by tumor cells via endocytotic process, a faster release may occur at lower local pH, i.e, inside the endosome and lysosome of cancer cells ((pH 4.5∼6.5), leading to the significant improvement in cancer treatment efficacy. The DNR- TiO2 nanocomposites as DDS induced the remarkable improvement in the anti-tumor activity, which were demonstrated by the flow cytometry, MTT assay and nuclear DAPI staining. Furthermore, the possible signaling pathway was explored by Western blot. For instance, in human leukemia cells (K562 cells), our observations demonstrated that the DDS could obviously increase the intracellular concentration of DNR and enhance its potential anti-tumor efficiency through inducing apoptosis in a caspase-dependent manner, indicating that DNR-TiO2 nanocomposites could act as an efficient DDS importing DNR into target cancer cells. These findings revealed that such ‘smart' DNR delivery strategy represent a promising approach in hematologic malignancy therapy. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4856 Objective: The multidrug resistance (MDR) in leukemia is a major chemotherapy obstacle, rendering many currently available chemotherapeutic drugs ineffective. The aim of this study was to explore the new strategy to early diagnose the MDR by electrochemical biosensor based on carbon nanotubes–drug supramolecular interaction. Methods: The carbon nanotubes modified glassy carbon electrodes (CNTs/GCE) as a sensor were directly immersed into the cells suspension of the sensitive leukemia cells K562 and/or its MDR cells K562/A02 to detect the response of the electrochemical probe of daunorubicin (DNR) residues after incubated with cells. Results: The fresh evidence from the electrochemical studies based on CNTs/GCE demonstrated that the homogeneous, label-free strategy could directly measure the function of cell membrane transporters in MDR cancer cells, identify the cancer cell phenotype (sensitive or MDR). The cathodic peak current showed good linear response to the changes of the fraction of MDR with a correlation coefficient of 0.995 when we further took the different ratios of the sensitive leukemia cells K562 and its MDR ones K562/A02 as the model of MDR levels to simulate the MDR occurrence in leukemia. Then, we can easily predict the MDR fraction based on the calibration curve of the cathodic peak current versus the fraction of MDR according to the obtained peak current. Conclusion: These results indicated that the biosensing assay could provide a powerful tool for assessment of MDR in leukemia. The new electrochemical biosensor based on carbon nanotubes–drug supramolecular interaction could represent promising approach in the rapid diagnosis of MDR in leukemia. Disclosures: No relevant conflicts of interest to declare.