Antitumor Activity and Immunostimulant Properties of Liposomes Containing Rosemary Extract on a Mouse Model of Colorectal Cancer.

Background: Rosemary (Ros) is a member of the Lamiaceae family known for its antitumor properties. However, its low water solubility and impaired bioavailability are limiting factors when using rosemary extract. Liposomes are synthetic vesicles that offer permeability, improved bioavailability, and lack of immunogenicity and toxicity, making them ideal for delivering various drugs.

Objective: To prepare liposomes (HSPC/Chol/mPEG2000-DSPE) containing rosemary alcoholic extract (LipRos) and evaluate its antitumor properties in a mouse model of colorectal cancer (CRC).

Methods: LipRos were prepared and characterized. CRC was induced in Balb/c mice by subcutaneous injection of C26 cells, and tumor size was monitored continuously. The MTT assay was performed to evaluate cytotoxicity, and liver and kidney function tests were conducted to assess safety. The expression of the pro-apoptotic gene B-cell-lymphoma-2 (Bcl-2), the anti-apoptotic gene Bcl-2-associated-X-protein (Bax), and the expression of cytokines Tumor-necrosis-factor-alpha (TNF-α), Transforming-growth-factor-beta (TGF-β), and Interferon-gamma (IFN-γ) were investigated using real-time PCR. Flow cytometry was used to evaluate the count of cytotoxic (CTL) and regulatory T lymphocytes (Tregs) in spleen and tumor tissue.

Results: The results showed that the size of liposomal formulations and their encapsulation efficiency were 113.4 nm and 85%, respectively. The MTT assay demonstrated insignificant cytotoxicity of LipRos on splenocytes, and the tumor size was significantly reduced in the LipRos group (P=0.00045). LipRos also significantly decreased Bcl-2 gene expression (P=0.0086), increased Bax and IFN-γ gene expression (P=0.031), and enhanced the infiltration of CTLs in tumor tissue (P=0.023).

Conclusion: This study showed that PEGylated (Poly-Ethylene-Glycol) liposomes containing rosemary extract exhibit an antitumor effect on C26 colorectal cancer cells through multiple mechanisms. These findings can be utilized in future studies.