Culture Supernatants from Lactobacillus plantarum Induce Necrosis on a Human Promyelocytic Leukemia Cell Line

Aims: Lactic acid bacteria (LAB) are known to have antitumoral properties, although the intrinsic mechanisms responsible for the execution of this activity are poorly understood. Here, we investigated the ability of concentrated supernatants from Lactobacillus plantarum to promote cell death in a human promyelocytic cell line. Methods and Results: We aim to test the hypothesis that concentrated supernatants from Lact. plantarum at 5, 50 or 100 μg/ml for 24 h exert cytotoxic effects on HL-60 cells. Accumulation of reactive oxygen species (ROS) was diminished and nuclear staining with Hoechst 33342 and propidium iodide (PI) determined a necrotic induction in a concentrationdependent sequence. Concentrated supernatants did not modify or reduced the activity of caspase-3. The assessment of phosphatidylserine externalization by annexin V/PI double staining led to a necrotic state, but the treatment did not produce a dissipation of mitochondrial membrane potential (ΔΨm), whereas cell cycle analysis revealed that concentrated supernatants failed to significantly enhance the population of HL-60 cells in the hypodiploid (sub-G1) fraction. Conclusions: Concentrated supernatants from Lact. plantarum are capable of inducing necrosis rather than apoptosis at high doses in a promyelocytic cell line. Significance and Impact of the Study: Here, we demonstrate the cytotoxic properties of concentrated supernatants from Lact. plantarum on a tumor cell line, and then, to open the possibility to analyze the chemical composition to elucidate the bioactive molecules.