Ferulic acid enhances the radiation sensitivity of lung and liver carcinoma cells by collapsing redox homeostasis: mechanistic involvement of Akt/p38 MAPK signalling pathway.

The major drawback of anticancer therapy is the development of resistance against drugs and radiation at the later phase of treatment which may lead to recurrences of the disease. Therefore, strategy was taken to enhance radiation sensitivity of lung (A549) and liver (HepG2) carcinoma cells by treatment with ferulic acid (FA) prior to irradiation. FA pre-treatment initially decreased reactive oxygen species (ROS) level in carcinoma cells which induced reductive stress and cytostasis. To overcome this stress, cellular mechanism increased the Keap1 level to down-regulate nuclear localisation of Nrf2 and its dependent antioxidant system. The antioxidant system reached the lowest level after 3 and 6 h of FA treatment in A549 and HepG2 cells respectively. As endogenous ROS were still being generated at same rate, ROS level was clearly higher than control which changed the reductive stress to oxidative stress. Exposure to γ-radiation in this condition further increased ROS level and caused radio-sensitisation of carcinoma cells. Combination of irradiation (IR) and FA activated mitochondrial apoptotic pathway and concomitantly inhibited the cell cycle progression and survival pathway over the IR group. Moreover, the combination treatment showed significant tumour regression, caspase 3 activation and nuclear fragmentation in tumour tissue compared to radiation alone. In contrast, FA pre-treatment protected peripheral blood mononuclear cells (PBMC) and normal lung fibroblast WI38 cells from radiation damage. Together, combination treatment offers effective strategy of killing cancer cells and demonstrates its potential for increasing the efficacy of radio-therapy.