The activity of TSL aqueous extracts against small-cell lung cancer is mainly through inhibition of the expression of cyclin D1 and cyclin-dependent kinase 4 (CDK4) in H441 cells (lung adenocarcinoma) and H661 cells (lung large cell carcinoma) (IC50 of 0.20 and 0.12 mg/mL, respectively) and the blockade of the cell cycle in the G1 phase. This evidence concerns the gene CDK4 and small cell lung carcinoma.