Atividade antitumoral e antiviral de lectinas de leguminosas (tribo Phaseoleae, subtribo Diocleineae): ConBr, ConM, DLasiL e DSclerL

Abstract

Several compounds isolated from plants, including proteins called lectins, have exhibited many types of biological activities. These proteins are specific recognizing and binding to carbohydrates found onto the cell surface. During the last decades, lectins have become promising sources for antitumor and antiviral studies. This study aimed to investigate legumineous lectins, ConBr (Canavalia brasiliensis), ConM (Canavalia maritima), DLasiL (Dioclea lasiocarpa) and DSclerL (Dioclea sclerocarpa) as potential anti-cancer and anti-viral agents, as well as studying structurally DLasiL using fluorescence, circular dichroism and its initial mechanism of anticancer activity. DLasiL lectin was characterized showing 237 amino acid residues with high similarity to lectin from the Diocleinae subtribe. Electron paramagnetic resonance of DLasiL showed a typical signal for manganese (Mn+2), while ICP-MS provided its actual amount along with calcium (Ca2+), whose values were below those found for the other lectins. Intrinsic fluorescence studies using three quenchers showed a better accessibility of neutral species to tryptophans of DLasiL, while extrinsic fluorescence using bis-ANS exhibited a dose-dependent conformational changes promoted by sugars. Circular dichroism showed very expressive thermal stability of DLasiL with mid-point for thermal denaturation at 72 °C. These lectins were used to treat human ovarian carcinoma (A2780), Human Lung Carcinoma (A549), Human Breast Carcinoma (MCF7), Human Prostate Carcinoma (PC3) and cell viability was determined. These proteins showed potent activity on inhibiting cell growth at nanomolar concentrations. Among these lectins, DLasiL was the most effective showing potent cytotoxicity against A2780 cell line with IC50 of 52 nM. The mechanism of cytotoxicity action of DLasiL was investigated by specific apoptosis assay. Cell cycle studies showed DLasiL causes significant changes in the levels of S and G2/M. A virus screening investigation was carried out showing promissing antiviral activity.