Volatile oil of Teucrium alopecurus sensitizes colon cancer cells to TRAIL-induced cell death

TNF-related apoptosis-inducing ligand (TRAIL/Apo2L), a member of cytokine family, is known to selectively induce apoptosis in cancer cells. However, developing resistance to TRAIL is a major obstacle in cancer therapy. In this study, the in vitro effect of Teucrium alopecurus (TA) essential oil on inhibition of cancer cell growth and enhancing TRAIL-induced apoptosis were investigated in colon cancer cells. Untreated tumor cell lines are used as controls. TA induced cell death and increased the anticancer effects of TRAIL as observed by cell toxicity, live/dead assay, cleavage of caspases and PARP. Furthermore, the mechanism of anticancer potentiating effect of TA was found to be linked with the upregulation of death receptors (DRs) and reduced expression of TRAIL decoy receptors (DcRs). TA also down-regulated antiapoptotic proteins and induced p53 in colon cancer cells. In addition, we observed upregulation of MAPK signalling pathway (p38 kinase, JNK, ERK) and increased expression of C/EBP homologous transcription factor (CHOP) and specificity protein 1 (SP1) by TA. These findings demonstrate the potent anticancer effect of bioactive constituents of Teucrium alopecurus essential oil.