Avaliação do efeito sinérgico na atividade citotóxica de doxorrubicina e glicoevatromonosídeo com as hidroxilas da glicose peracetiladas co-encapsulados em lipossomas fusogênicos de circulação prolongada.

Abstract

Cancer is one of the main causes of death in the world and thus a public health problem. Among treatments available for cancer are the surgery, radiotherapy and chemotherapy. Currently, the combination of two or more antitumor agents has become interesting to achieve a synergistic effect in cancer therapy. Doxorubicin (DXR) is a chemotherapeutic wich has a potent antineoplastic action and has been used in the treatment of various tumors, however its use is limited, mainly due cardiotoxicity. Therefore, nanostructured systems such as liposomes have been developed to carry this durg and target the tumor region, since tumor tissues present enhanced permeability and retention for nanosystems. Cardiac glycosides, such as digitoxin, have recently shown a great antitumor potential despite low therapeutic index which may limit their use. Futhermore, some compounds of this class have low water solubility which makes it difficult to administer. Hence, liposomes, which are systems capable of carrying hydrophilic, lipophilic and amphiphilic drugs, have been as an interesting strategy for delivery these compounds and targeting of the tumor region. The present work consisted in the development of fusogenic long-circulation liposomes containing glucoevatromonoside with the peracetylated glucose hydroxyls (GEVGP) and DXR in the molar ratio of 1: 1 (LpHS-GEVGP+DXR 1:1), the evaluation of the synergism in vitro of this formulation, storage stability study, release profile of GEVGP and DXR form LpHS-GEVGP+DXR 1:1, determination of the selectivity index, cumulative population doubling (CPD), cell cycle and death pathways evaluation. From the results of the present study, LpHS-GEVGP+DXR 1:1 presented adequate chemical and physicochemical properties such as size of 193, 9 ± 9.3 nm, polidispersivity index (PI) of 0.3 ± 0.1, zeta potential of - 2.4 ± 0.5 mV and entrapment percentage (EP) of GEVGP and DXR of 67.5 ± 11.1 and 104.2 ± 12.0, respectively which allowed the molar ratio of 1: 1 to be obtained. This formulation also presented combination index lower than 1 at concentration required to inhibit the growth of 90% (IC90) of three human breast tumor cell lines, such as: MDA-MB-231 (0.52 ± 0.39), MCF-7 (0.36 ± 0.19) and SKBR-3 (0.73 ± 0.40) in SKBR-3). These findings indicate a synergistic cytotoxic effect of the GEVGP and DXR combination encapsulated in liposomes. Moreover, the formulation showed good storage stability for 90 days in terms of mean diameter, PI, zeta potential, EP of GEVGP and DXR and presented reduced release of GEVGP and DXR from LpHS-GEVGP+DXR 1:1 after 24 hours. LpHS-GEVGP+DXR1:1 showed selectivity for the breast tumor cells tested compared to healthy human fibroblasts. Evaluation of CPD demonstrated that cells surviving after treatment with the LpHS-GEVGP+DXR1:1 did not recover the proliferation capacity after 21 days. From the studies of cell cycle and death pathways evaluation, the LpHS-GEVGP+DXR1:1 was able to arrest the cell cycle at G2/M phase and induced low death rates from apoptosis and necrosis, suggesting the existence other death process involved. Thereby the results of the present study suggest that LpHS-GEVGP+ DXR 1:1 may be a promising alternative for breast cancer treatment.