Then, 50 μL of treated cell suspension were collected and incubated with JC-1 (10 μL/mL) for 30 min in the dark followed by washing two times with PBS. The cells were fixed with 4% paraformaldehyde (10 μL), mounted PCI-32765 purchase on glass slides, and fluorescence was observed using an epifluorescence microscope (Carl Zeiss, Gottingen, Germany), at 1000× magnification under oil immersion with filters

for LP 515 nm emission and BP 450–490 nm excitement. A minimum of 200 cells was counted in every sample. Cells with high potential of mitochondrial membrane were stained in red, while cells with low membrane potential were stained in green. All data are presented as mean ± S.D. The IC50 values were obtained by nonlinear regression with 95% confidence interval using the SigmaPlot software (Systal Software Inc., San Jose, USA). The differences between experimental groups were determined using one-way analysis

of variance (ANOVA) followed by the Newman–Keuls test at significance level of 1%. Cytotoxicity of BlL on cell lines was evaluated after 72 h using MTT assay. BlL exhibited cytotoxic activity against all tumor cell lines with IC50 values of 11.75 ± 0.035, GSI-IX cell line 6.63 ± 0.052 and 15.42 ± 0.060 μg/mL for Hep-2, NCI-H292 and K562, respectively. Etoposide was used as a positive control and showed IC50 values of 6.10 ± 0.19, 2.75 ± 0.10 and 4.48 ± 0.23 μg/mL for Hep-2, NCI-H292 and K562, respectively. Cytotoxic activity against non-tumorigenic cell line was not observed. The involvement

of apoptosis induction on K562 (chronic myelocytic leukemia) death was verified by evaluation of phosphatidylserine externalization using the Annexin V-FITC kit and epifluorescence microscope. We observed that after treatment with BlL (15.42 μg/mL), the number of cells in early apoptosis (Ann Vpos/PIneg) corresponded to 70.5% (Fig. 1a). Treatment with BlL exhibited values less than 1% of late apoptotic cells (AnnVpos/PIpos) and values less than 2% of cell necrosis (AnnVneg/PIpos). Fig. 1b also shows that the treatment of K562 cells with BlL caused mitochondrial membrane potential loss, as the epifluorescence microscopy analysis determined that BlL treatment induced a significant increase Liothyronine Sodium in cells with depolarized mitochondria (63.8%) as compared to control cells, as measured by JC-1 incorporation. Uncontrolled proliferation and decreased apoptotic signals are attributes of oncogenic transformation (Hill et al., 2003), and activation of apoptosis constitutes a fundamental mechanism by which drugs may kill tumor cells (Debatin, 2004). Therefore, compounds with the ability to induce apoptosis in tumor cells have potential as anticancer agents (Reed, 2003). MTT assay demonstrated that BlL showed a significant cytotoxic effect indicating that the activity of this lectin was not specific to a particular tumor cell type.