Anti-proliferative and immunomodulatory properties of kaffir lime leaves and bioactive compounds on macrophages co-cultured with squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the seventh most common cancer worldwide. Late-stage patients have a significant chance of local recurrence and distant metastasis, as well as poor prognosis. Therapeutic goals for patients must be improved and personalized to reduce adverse effects. This study explored the anti-proliferative activity and immunomodulation potential of the constituents of crude kaffir lime leaf extract (lupeol, citronellal and citronellol) under co-culture. Results showed high cytotoxicity to human SCC15 cell line but not to human monocyte-derived macrophages. Treatment with crude extract and the contained compounds also suppressed cell migration and colony formation of SCC15 compared to the untreated control group, while high levels of intracellular ROS production were detected in the treatment group of SCC15. The Muse(TM) cell analyzer revealed cell cycle arrest at G2/M phase and apoptosis induction. Inhibition of Bcl-2 and activation of Bax, leading to induction of the downstream caspase-dependent death pathway were confirmed by Western blot analysis. Co-culture with activated macrophages, kaffir lime extract and its constituents enhanced the development of pro-inflammatory (M1) macrophages and boosted TNF-alpha production, resulting in SCC15 apoptosis. Findings revealed novel potential activities of kaffir lime leaf extracts and their constituents in inducing M1 polarization against SCC15, as well as direct anti-proliferative activity.

Automated summary

This study investigated the anti-proliferative activity and immunomodulation potential of crude kaffir lime leaf extract constituents in co-culture. Results demonstrated high cytotoxicity to the SCC15 cell line but not to macrophages, as well as suppression of cell migration and colony formation. Treatment induced cell cycle arrest and apoptosis, mediated by Bcl-2 inhibition and Bax activation. Co-culture with activated macrophages and kaffir lime extract enhanced pro-inflammatory macrophage development and TNF-alpha production, leading to SCC15 apoptosis. The findings suggest novel potential activities of kaffir lime leaf extracts in inducing M1 polarization and direct anti-proliferative effects against SCC15.