Thymol-loaded liposomes effectively induced apoptosis and decreased EGFR expression in colorectal cancer cells

Background: Colorectal cancer (CRC) is one of the most common and deadly cancers worldwide. Different factors, such as environmental and genetic factors and lifestyle, affect it. Owing to the presence of phenolic, alkaloid, antioxidant, and terpenoid compounds, herbal compounds can be effective in the treatment of various cancers. Thymol is a natural monoterpene phenol that is abundant in some plants and exerts several biological effects. The aim of this study was to investigate the apoptotic, anti-proliferative effect and EGFR gene expression under the influence of thymol-loaded nanoliposome in SW84 and SW111 cell lines derived from colorectal cancer.

Materials and methods: The lipid thin-film hydration method was used to synthesize thymol-loaded liposomes, and their characterization was performed using TEM, DLS, and HPLC analyses. SW84 and SW1111 cells were treated with thymol- and thymol-loaded liposomes at different doses, the inhibition of cell proliferation was evaluated using an MTT assay, the rate of apoptosis induction was assessed using flow cytometry, and EGFR gene expression was measured using real-time PCR.

Results: The nanoparticles produced were spherical, uniform, and 200 ± 10 nm in size. HPLC analysis showed that approximately 98% thymol was loaded into the nanoliposome. The results of the MTT assay showed that thymol and thymol-nanoliposomes decreased the proliferation of SW84 and SW1111 cells in a concentration-dependent manner. The IC50 of thymol and thymol-nanoliposomes were 18 and 14.2 µg/ml for the SW48 cell line (P = 0.04) and 10.5 and 6.4 µg/ml for the SW1116 cell line (P = 0.001). Thymol-nanoliposomes significantly inhibited the proliferation of cancer cells compared to free thymol. Flow cytometry showed an increase in the percentage of apoptotic cells, especially in the thymol-nanoliposome group in the treated cells. Real-time PCR results also showed that thymol and thymol-nanoliposome both caused a decrease in the expression of EGFR genes in both cell lines, but this effect of decreasing gene expression was significantly higher in the thymol-nanoliposome group.

Conclusions: Our results showed that thymol-nanoliposomes reduced proliferation, increased apoptosis, and decreased EGFR expression in colorectal cancer-derived cell lines.