New method for the detection of reactive oxygen species in anti-tumoural activity of adriamycin: A comparison between hypoxic and normoxic cells

Tumour hypoxia plays a role in chemoresistance in several human tumours. However, how hyperbaric oxygen leads to chemotherapeutic gain is unclear. This study investigates the relation of reactive oxygen species (ROS) generation with anti-tumoural effect of adriamycin (ADR) on CCRF-CEM cells under hypoxic (2% O₂) and normoxic (21% O₂) conditions. A new method was used to measure intracellular ROS variations through the fluorescence lifetime of 1-pyrenebutyric acid. At 24 h, ADR, probably via semiquinone radical, enhances ROS levels in normoxic cells compared to hypoxic cells. Long-term studies show that ROS are also generated by a second mechanism related to cell functions perturbation. ADR arrests the cell cycle progression both under hypoxia and normoxia, indicating that oxygen and ROS does not influence the DNA damaging activity of ADR. The findings reveal that moderate improvement of ADR cytotoxicity results from higher ROS formation in normoxic cells, leading to elevated induction of cell death.