Tumor-specific hyperthermia with aptamer-tagged superparamagnetic nanoparticles.

Targeted therapy is a method owing to its limited side effect profile, particularly in cancer treatment. Magnetic hyperthermia, which is induced by nanoparticles (NPs) conjugated with targeting agents, can be useful in combination with chemo- or radiotherapy. In this paper, we constructed dextran-coated ferric oxide NPs conjugated with specific anti-human epidermal growth factor receptor (HER2) aptamer and used them to induce magnetic hyperthermia in cultured cells. The specificity of the tagged NPs was determined by studying their effect relative to that of non-tagged NPs against two cell lines: human adenocarcinoma SK-BR3, overexpressing the HER2 receptor; and U-87 MG, a human glioblastoma epithelial cell line, not expressing HER2. In order to confirm the interaction of the tagged NPs with the cells we used, fluorescence microscopy and fluorescence-activated cell sorting analysis were performed. All of these experiments showed that the aptamer-tagged NPs were highly specific toward the HER2-expressing cells. In addition, a ninetyfold lower dose of the tagged NPs relative to that of the non-tagged NPs was needed to achieve ~50% cell killing by hyperthermia of the SK-BR3 cell line, while for the U-87 MG cells the viability level was close to 100%. These results show that targeted NPs can be applied at substantially lower doses than non-targeted ones to achieve similar effects of hyperthermia, which should greatly limit the side effects of treatment.

Aggregation of spectrin and PKCtheta is an early hallmark of fludarabine/mitoxantrone/dexamethasone-induced apoptosis in Jurkat T and HL60 cells.

It has been shown that changes in spectrin distribution in early apoptosis preceded changes in membrane asymmetry and phosphatidylserine (PS) exposure. PKCtheta was associated with spectrin during these changes, suggesting a possible role of spectrin/PKCtheta aggregation in regulation of early apoptotic events. Here we dissect this hypothesis using Jurkat T and HL60 cell lines as model systems. Immunofluorescent analysis of alphaIIbetaII spectrin arrangement in Jurkat T and HL60 cell lines revealed the redistribution of spectrin and PKCtheta into a polar aggregate in early apoptosis induced by fludarabine/mitoxantrone/dexamethasone (FND). The appearance of an alphaIIbetaII spectrin fraction that was insoluble in a non-ionic detergent (1% Triton X-100) was observed concomitantly with spectrin aggregation. The changes were observed within 2 h after cell exposure to FND, and preceded PS exposure. The changes seem to be restricted to spectrin and not to other cytoskeletal proteins such as actin or vimentin. In studies of the mechanism of these changes, we found that (i) neither changes in apoptosis regulatory genes (e.g., Bcl-2 family proteins) nor changes in cytoskeleton-associated proteins were detected in gene expression profiling of HL60 cells after the first hour of FND treatment, (ii) caspase-3, -7, -8, and -10 had minor involvement in the early apoptotic rearrangement of spectrin/PKCtheta, and (iii) spectrin aggregation was shown to be partially dependent on PKCtheta activity. Our results indicate that spectrin/PKCtheta aggregate formation is related to an early stage in drug-induced apoptosis and possibly may be regulated by PKCtheta activity. These findings indicate that spectrin/PKCtheta aggregation could be considered as a hallmark of early apoptosis and presents the potential to become a useful diagnostic tool for monitoring efficiency of chemotherapy as early as 24 h after treatment.