Anticancer effect of linalool via cancer-specific hydroxyl radical generation in human colon cancer

AIM To investigate the anticancer mechanisms of the monoterpenoid alcohol linalool in human colon cancer cells. METHODS The cytotoxic effect of linalool on the human colon cancer cell lines and a human fibroblast cell line was examined using the WST-8 assay. The apoptosis-inducing effect of linalool was measured using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry with Annexin V. Oxidative stress was investigated by staining for diphenyl-1-pyrenylphosphine, which is a cellular lipid peroxidation marker, and electron spin resonance spectroscopy. Sixteen SCID mice xenografted with human cancer cells were randomized into 3 groups for in vivo analysis: control and low-dose and high-dose linalool groups. The control group was administered tap water orally every 3 d. The linalool treatment groups were administered 100 or 200 μg/kg linalool solution orally for the same period. All mice were sacrificed under anesthesia 21 d after tumor inoculation, and tumors and organs were collected for immunohistochemistry using an anti-4-hydroxynonenal antibody. Tumor weights were measured and compared between groups. RESULTS Linalool induced apoptosis of cancer cells in vitro, following the cancer-specific induction of oxidative stress, which was measured based on spontaneous hydroxyl radical production and delayed lipid peroxidation. Mice in the high-dose linalool group exhibited a 55% reduction in mean xenograft tumor weight compared with mice in the control group (P < 0.05). In addition, tumor-specific lipid peroxidation was observed in the in vivo model. CONCLUSION Linalool exhibited an anticancer effect via cancer-specific oxidative stress, and this agent has potential for application in colon cancer therapy.