Encapsulação do paclitaxel em lipossomas recobertos com folato aumenta a captação celular e o efeito antitumoral em modelo experimental de tumor de mama

Abstract

Paclitaxel (PTX) is an effective chemotherapeutic agent widely used in breast cancer treatment. Nevertheless, the low solubility of the drug and the side effects of commercialformulations available limit their clinic use. In other to overcome this drawback, PTX-loaded folate-coated long circulating and pH-sensitive liposomes (SpHL-folate-PTX) were developed by our group. Then, in this study, the physicochemical characterization and in vitro and in vivo biological behavior of this formulation against tumor line MDA-MB-231 (human breast) were evaluated. SAXS studies under high hydration conditions evidenced that the PTX inclusion in the lipidic bilayer leads to shifts in the supramolecular organization of the dioleylphosphatidylethanolamine (DOPE) molecules, however, it did not affect the pHsensitivity of the liposomal formulation. The morphological and physicochemical analysis of the system demonstrated a nanometric dispersion suitable for intravenous administration. Biodistribution studies showed high uptake in liver, spleen, and kidneys, as a greater tumor uptake compared to contralateral muscle in all timeframes with a higher tumor-muscle ratio observed for the group treated with SpHL-folate-PTX. Cellular uptake assay, in vitro, showed a higher delivery of PTX into the cells by SpHLF-PTX which leads to a superior cytotoxicity whit apoptosis process the main cell death pathway. The cell cycle evaluation showed an expressive increase of cells with a stop at G0/G1 phase after treatment SpHL-folate-PTX when compared to PTX prepared in Cremophor and ethanol (PTX:Cr+Et) and SpHL-PTX, that present the most of cells at G2/M phase. Antitumor activity in vivo showed a significant reduction in the tumor growth and a lower uptake by 99mTc-BBN in scintigraphic images for SpHL-folate-PTX group compared to PTX:Cr+Et e SpHL-PTX, which suggest a higher efficacy of this formulation. Histomorphometric analyzes demonstrated an increase in the necrosis and inflammation areas in the animals treated with SpHL-folate-PTX. A decreasing in the proliferative cells and a higher percentage of apoptotic cells were observed by immunohistochemical analyses after the treatment with SpHL-folate-PTX. Therefore, the presented data confirmed the potential of SpHL-folate-PTX as an alternative antitumor therapy, especially for breast cancer.