Reabroi S.Kasemsuk T.Saeeng R.Chairoungdua A.Mahidol University2026-06-092026-06-092026-12-01Discover Oncology Vol.17 No.1 (2026)https://repository.li.mahidol.ac.th/handle/123456789/117168Colorectal cancer is the second leading cause of cancer-related mortality worldwide, highlighting the critical need for novel therapeutic strategies. In this study, we investigated the anticancer activity and molecular mechanisms of RS-PP-059, a derivative of 14-deoxy-12-hydroxyandrographolide, in colorectal cancer cells. RS-PP-059 exhibited potent cytotoxicity and selectivity toward HT-29 cells, suppressing viability and clonogenic growth. The compound induced apoptotic cell death, as shown by increased Annexin V-positive cells, PARP-1 cleavage, p53 activation, and γ-H2AX accumulation, indicating DNA damage, and was accompanied by a reduction in total caspase-3 protein levels. Mechanistically, RS-PP-059 triggered endoplasmic reticulum (ER) stress and unfolded protein response (UPR), upregulating key markers including GRP78, IRE1α, CHOP, and spliced XBP1 (XBP1s) at both mRNA and protein levels. Co-treatment with the ER stress inhibitor 4-phenylbutyrate (4-PBA) only partially reversed these effects, suggesting robust ER stress activation by RS-PP-059. In parallel, RS-PP-059 increased intracellular reactive oxygen species (ROS) in a time-dependent manner, accompanied by differential regulation of antioxidant genes with strong induction of HO-1 and suppression of CAT, SOD1, and GPX-1. Importantly, pretreatment with N-acetyl-L-cysteine (NAC) abolished ROS accumulation, ER stress activation, apoptosis, and loss of viability, confirming the ROS-dependent mechanism. In conclusion, our findings demonstrate that RS-PP-059 exerts potent anticancer effects in colorectal cancer cells by promoting ROS-mediated ER stress, leading to DNA damage and apoptosis.NeuroscienceBiochemistry, Genetics and Molecular BiologyMedicineArticleSCOPUS10.1007/s12672-026-05052-72-s2.0-10504066083227306011