Juglone-Bearing Thiopyrano[2,3-d]thiazoles Induce Apoptosis in Colorectal Adenocarcinoma Cells

Colorectal cancer is a major global health challenge, with current treatments limited by toxicity and resistance. Thiazole derivatives, known for their bioactivity, are emerging as promising alternatives. Juglone (5-hydroxy-1,4-naphthoquinone) is a naturally occurring compound with known anticancer properties, and its incorporation into thiopyrano[2,3-d]thiazole scaffolds may enhance their therapeutic potential. This study examined the cytotoxicity of thiopyrano[2,3-d]thiazoles and their effects on apoptosis in colorectal cancer cells. Les-6547 and Les-6557 increased the population of ROS-positive HT-29 cancer cells approximately 10-fold compared with control cells (36.3% and 38.5% vs. 3.8%, respectively), potentially contributing to various downstream effects. Elevated ROS levels were associated with cell cycle arrest, inhibition of DNA biosynthesis, and reduced cell proliferation. A significant shift in the cell cycle distribution was observed, with an increase in S-phase (from 17.3% in the control to 34.7% to 51.3% for Les-6547 and Les-6557, respectively) and G2/M phase (from 24.3% to 39.9% and 28.8%). Additionally, Les-6547 and Les-6557 inhibited DNA biosynthesis in HT-29 cells, with IC₅₀ values of 2.21 µM and 2.91 µM, respectively. Additionally, ROS generation may initiate the intrinsic apoptotic pathway. <b>Les-6547</b> and <b>Les-6557</b> activated both intrinsic and extrinsic apoptotic pathways, demonstrated by notable increases in the activity of caspase 3/7, 8, 9, and 10. This study provides a robust basis for investigating the detailed molecular mechanisms of action and therapeutic potential of Les-6547 and Les-6557.