1). After 24 h, ConA at concentrations of 5, 25, and 50 μg/ml inhibited BrdU incorporation by 47.66 ± 2.79%, 72.45 ± 1.95%, and 87.58 ± 2.16%, respectively, in MOLT-4 cultures (Fig.

1A), and 39.12 ± 2.69%, 61.18 ± 3.68%, and 78.95 ± 2.66%, respectively, in HL-60 cultures (Fig. 1B). Leukemic cell cultures exposed to ConBr showed an inhibition of BrdU incorporation equal to 47.78 ± 4.52%, 69.31 ± 3.53%, and 86.60 ± 1.80% for MOLT-4 cells treated at 5, 25, and 50 μg/mL, respectively, and 28.65 ± 2.95%, 58.10 ± 3.01%, and 66.81 ± 3.49% for HL-60 cells treated at 5, 25, and 50 μg/mL, respectively. PD0325901 cell line The positive control, etoposide, strongly inhibited the BrdU incorporation, as expected. Etoposide exhibited A1210477 potent cytotoxicity against HL-60 and MOLT-4 cell lines, as expected. The results presented in Fig. 2 demonstrate that ConA and ConBr are not cytotoxic for normal cells (PBMC) at 200 μg/ml using MTT assay. Fig. 3A and B show the effects of ConA and ConBr on DNA damage index and frequency (tailed cells) as measured by DNA damage in leukemic cells according to the alkaline version of the comet

assay. In both cell line cultures exposed to ConA and ConBr, the treated cells clearly show a significant increase in the means of DNA damage index (p < 0.001) and tailed cells (p < 0.001) at all evaluated concentrations. Etoposide, used as the positive control, induced a significant increase in DNA damage and frequency when compared to the negative control, or vehicle (data not shown). While attempting to determine the mechanism responsible for their antiproliferative effects, both the induction of apoptosis or necrosis and the DNA integrity of cells that were treated with lectins were assayed. After 24 h, more than 90% of the counted HL-60 and MOLT-4 cells in the control groups were uniformly green, viable, and had normal morphology ( Fig. 4). As shown in Fig. 4A and B, both lectins reduced the number of viable cells in a concentration-dependent manner after 24 h of exposure at each evaluated concentration

(p < 0.001) in leukemic cell cultures (MOLT-4 and HL-60). However, the effect on cell viability was more pronounced in cultures Calpain treated with ConA. The mechanism of induction of cell death in leukemic cells appears to be the same among the tested lectins. The antiproliferative capacity of both lectins seems to be predominately related to the apoptosis activation rather than necrosis. At the highest tested concentration, MOLT-4 and HL-60 cells exposed to ConA and ConBr showed that more than 60% of analyzed cells shared apoptotic features. These features include condensed or fragmented chromatin, blebs, and apoptotic bodies. The increase in the population of necrotic cells was smaller, achieving 25.33 ± 0.59% and 21.99 ± 1.14% when MOLT-4-treated with 50 μg/mL of ConA and ConBr, respectively.