Available online 21 August 2020, 107636



Hypoxia reduces bleomycin cytotoxicity on intact hepatoma cells.

Efficacy of bleomycin electrochemotherapy is reduced 5.3-fold in hypoxia.

Cytotoxicity of bleomycin can be modulated 1–2 h after cell electroporation.


Bleomycin, which is the most widely used drugs in electrochemotherapy, requires oxygen to be able to make single- or double-strand brakes in DNA. However, the concentration of oxygen in tumours can be lower than 1%. The aim of this study was to find out whether oxygen concentration in the medium in which cells loaded with bleomycin are incubated, affects the effectiveness of electrochemotherapy in vitro. Experiments were carried out on mouse hepatoma MH-22A cells. Cells were loaded with bleomycin by using a single square-wave electric pulse (2 kV/cm, 100 μs) under normoxic conditions, seeded into Petri dishes, and grown under normoxic and hypoxic conditions. Cell viability was determined by means of a colony-forming assay. We demonstrated that when cells loaded with bleomycin were incubated in hypoxia (0.2% O2), up to 5.3-fold higher concentrations of bleomycin were needed to kill them in comparison with cells grown in normoxia (18.7% O2).




activated bleomycin

hepatocellular carcinoma


media acclimatization

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