In Vitro Anti-Proliferative and Cisplatin-Modulating Effects of Cedrus libani A. Rich Leaf Essential Oil on H460 and HT-29 Human Cancer Cell Lines

Abstract

Cedrus libani A. Rich is a coniferous tree native to the eastern Mediterranean region that is known for exhibiting pharmacological properties. In the present study, we investigated the anti-proliferative effect of C. libani leaf essential oil (EO) against H460 and HT-29, as well as evaluated its chemo-modulatory effect with cisplatin (CIS). The EO chemical profile was analyzed via GC-MS. Cell viability was assessed using MTT, while trypan blue exclusion and Annexin V/Propidium Iodide staining were employed to detect cell death. Colony biomass and wound closure were evaluated using crystal violet staining and a scratch assay, respectively. Nuclear morphology and reactive oxygen species (ROS) were assessed using DAPI staining and an NBT assay, respectively. EO and CIS individually reduced cell viability in a time- and concentration-dependent manner with combination treatments demonstrating synergistic/additive/antagonistic interactions depending on the combination ratio, cell line and time point. EO alone does not exhibit significant cell death, whereas CIS demonstrated significant apoptosis and necrosis. The combination (IC50:IC50) enhanced cell death, particularly in HT-29. Both EO and CIS reduced colony biomass and wound closure, with the combination showing higher inhibitory effect on colony biomass in both cell lines and enhanced wound closure inhibitory effect in HT-29 but reduced effect in H460.. CIS and combination caused more notable nuclear alterations compared to EO alone, whereas an early increase in NBT reduction followed by a subsequent decrease was observed for individual treatments as well as the combination. This study provides insights into the antiproliferative and chemo-modulatory potential of C. libani leaf essential oil, although further studies are needed to elucidate the underlying molecular mechanisms.