D-Limonene Exhibits Antiproliferative Activity Against Human Colorectal Adenocarcinoma (Caco-2) Cells via Regulation of Inflammatory and Apoptotic Pathways.

Current therapies for colorectal cancer (CRC) are associated with significant side effects and limitations, driving the search for novel therapeutic approaches. This study investigated the antiproliferative potential of D-limonene, a natural compound, on human colorectal adenocarcinoma (Caco-2) cells and analyzed its underlying mechanisms. Caco-2 cells were treated with D-limonene or doxorubicin (DOX) for 24 h. Cell viability was assessed using the MTT assay, with D-limonene and DOX showing IC50 values of 18.6 and 6.4 µM, respectively. In comparison to controls, D-limonene treatment dramatically enhanced the formation of reactive oxygen species (ROS) and decreased cellular antioxidant capacity, as seen by concentration-dependent lower glutathione (GSH) levels. The substance also increased the levels of pro-apoptotic proteins (caspase-3, Bax), tumor suppressor p53, lactate dehydrogenase (LDH), and inflammatory indicators [tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β)]. Furthermore, in a concentration-dependent way, D-limonene therapy decreased the levels of matrix metalloproteinases (MMP2, MMP9), proliferation marker Ki67, and the anti-apoptotic protein Bcl-2. These results imply that the induction of oxidative stress, inflammation, and apoptotic pathways mediates D-limonene's antiproliferative actions in colon cancer cells. Our findings show that D-limonene has therapeutic promise as a natural substitute for the treatment of colorectal cancer.