Differential oxidative and pro-apoptotic response of cancer and normal cells to an anti-inflammatory agent CLEFMA

Abstract

Selective killing of cancer cells by chemotherapy has been an age old challenge, but certain unique features of cancer cells allow discriminatory response between cancer and normal cells. The objectives of this study was to investigate pro-oxidant and apoptotic effects of CLEFMA, an anti-inflammatory compound with anticancer activity, in lung cancer cells versus normal lung fibroblasts and to establish its maximum tolerated dose (MTD) in mice. We found that CLEFMA preferentially induced reactive oxygen species (ROS)-mediated apoptosis in H441, H1650 and H226 cancer cells, but spared normal CCL151 and MRC9 fibroblasts. Immunoblotting studies revealed that CLEFMA-induced apoptosis is associated with p53 phosphorylation in cancer cells which was not observed in CLEFMA treated normal fibroblasts. CLEFMA showed no effect on NF-κB p-65 expression in the normal lung fibroblasts, whereas its translocation to nucleus was inhibited in cancer cells. Furthermore, CLEFMA treatment also inhibited the DNA-binding activity of NF-κB p65 in H441cancer cells, but not in normal CCL151 cells. Preclinical toxicology studies in CD31 mice showed that CLEFMA was not toxic when injected daily for 7 days or injected weekly for 4 weeks. Based on survival data, MTD of CLEFMA was estimated as 30 mg/kg bodyweight. We conclude that CLEFMA exploits the biochemical differences in cancer and normal cells and selectively induces ROS in cancer cells. Secondly, CLEFMA can be safely administered in vivo because its known dose necessary for in vivo efficacy as anti-inflammatory and anti-tumor agent (0.4 mg/kg) is 75 times lower than its MTD.