Fig. 1.

Ritanserin shows cytotoxic activity in lung tumor cells. (A) Ritanserin is a 5-HT₂R inverse agonist with known activity against lipid (DGKα) and protein (FER) kinases. Ketanserin is a 5-HT₂R inverse agonist that lacks DGKα/FER inhibitory activity and serves as a negative control. (B) Cell viability dose-response curves for NSCLC (A549, H1650) and SCLC (H82) tumor cells treated with ritanserin or ketanserin at the indicated concentrations for 2 days. (C) Time course of cell viability in tumor cells treated with 25 µM ritanserin, 25 µM ketanserin, or 1 µM staurosporine for 4 days. Staurosporine is a pan-kinase inhibitor and was included as a positive control of tumor cell death. All experiments were performed in triplicate and data are from two independent biologic replicates performed on separate days (n = 6). Statistical significance was calculated with respect to ketanserin treatment. Data are shown as means ± S.E.M. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001. 5-HT₂R, 5-HT₂ receptor.