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Cancers in which epigenetic changes, such as hypermethylation of DNA, lead to drug resistance cause the cancer to become unresponsive to existing chemotherapeutic treatments. The epigenetic drug – 5-aza-2’-deoxycytidine (decitabine, DAC) – is a potent hypomethylating agent, but its effect is transient due to its instability. Previous studies have shown that loading DAC into nanogel significantly enhances its antiproliferative effect (compared to DAC in solution) in drug-resistant breast cancer cells (MCF-7/ADR). Further, the previous studies demonstrated changes in the membrane lipid profile of resistant cells following treatment with DAC either as solution or in nanogels. The objective of the present study was to compare the stability of DAC as solution and DAC encapsulated in nanogel, determine the effect of duration of DAC and DAC-nanogel pretreatment on the antiproliferative activity of subsequent chemotherapeutic agent addition, and to visualize and quantify the effect of DAC and DAC-nanogel pretreatment on uptake of poly dl-lactide co-glycolide (PLGA)-based nanoparticle in MCF-7/ADR cells. An increase in the stability of DAC when encapsulated in nanogel could be a mechanism contributing to the sustained effect of DAC. DAC-nanogel’s sustained effect and its effectiveness at altering the membrane lipid profile to reduce resistance could cause a longer DAC-nanogel pretreatment time to increase the antiproliferative effect of subsequent chemotherapeutic agent addition. Additionally, the membrane lipid profile altering effects of DAC and DAC-nanogel could cause DAC and DAC-nanogel pretreatment to increase uptake of nanoparticles in MCF-7/ADR cells. The stability of DAC was assessed in mouse plasma at physiological conditions using mass spectrometry. DAC in solution was found to be less stable than DAC in nanogel. The effect of durations of 3-days and 5-days of DAC-nanogel treatments on the subsequent efficacy of chemotherapeutic agent, paclitaxel was assessed in MCF-7/ADR cells using a MTS assay. The DAC-nanogel had a greater effect with a longer duration of pretreatment time as determined by the dose-response curve, IC50, and IC70. The effect of DAC or DAC-nanogel pretreatment of a 3-day duration on subsequent uptake of nanoparticles was visualized with confocal microscopy and the differences in uptake were quantified. Increase in uptake of nanoparticles was seen in both DAC and DAC-nanogel with DAC alone having a greater effect. Overall, this study shows that increased DAC stability is a contributing factor to the increased efficacy and sustained effect of DAC-nanogel, the effect of DAC-nanogel on subsequent anticancer drug antiproliferative activity is significantly increased with a longer duration of pretreatment, and DAC and DAC-nanogel pretreatment cause a greater uptake of subsequent nanoparticle addition than in cells without any pretreatment. |
