Ononitol Monohydrate—A Glycoside Potentially Inhibit HT-115 Human Colorectal Cancer Cell Proliferation through COX-2/PGE-2 Inflammatory Axis Regulations

We aimed to inhibit HT-115 human colorectal cancer cell proliferation using ononitol monohydrate (OMH), a bioactive principle isolated from Cassia tora (L.). The cytotoxicity of OMH has been assayed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), cell and nuclear morphology, and apoptosis mechanisms have been analyzed using real-time PCR. Higher doses of OMH potentially inhibit 84% of HT-115 cell viability: we observed that the IC50 level was 3.2 &micro:M in 24 h and 1.5 &micro:M in 48 h. The treatment with 3.2 &micro:M of OMH for 48 h characteristically showed 64% apoptotic cells and 3% necrotic cells, confirmed by propidium iodide and acridine orange/ethidium bromide (AO/ErBr) staining. We found the overexpression of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE-2) in the control HT-115 cells, which was directly associated with colorectal tumorigenesis. However, 3.2 &micro:M of OMH treatment to HT-115 cells for 48 h significantly reduced inflammatory genes, such as TNF-&alpha:/IL-1&beta: and COX-2/PGE-2. The downregulation of COX-2 and PGE-2 was more significant with the 3.2 &micro:M dose when compared to the 1.5 &micro:M dose of OMH. Additionally, the protein levels of COX-2 and PGE-2 were decreased in the 3.2 &micro:M OMH-treated cells compared to the control. We found significantly (p &le: 0.01) increased mRNA expression levels of tumor-suppressor genes, such as pRb2, Cdkn1a, p53, and caspase-3, and decreased Bcl-2, mdm2, and PCNA after 48 h was confirmed with apoptotic stimulation. In conclusion, the antiproliferative effect of OMH via the early suppression of protumorigenic inflammatory agents TNF-&alpha:/IL-1&beta:, COX-2/PGE-2 expression, and the increased expression levels of tumor-suppressor genes Cdkn1a and pRb2, which enhanced the activation of Bax and p53.