3,3′-Diindolylmethane Augments 5-Fluorouracil-InducedGrowth Suppression in Gastric Cancer Cells through Suppression of the Akt/GSK-3β and WNT/Beta-Catenin

Gastric cancer (GC) is one of the most lethal cancers in South Korea, and it is a cancer of concern worldwide. 5-fluorouracil (5-Fu) is commonly used as the first-line therapy for advanced GC; however, its side effects often limit the dosage range and impair patients' quality of life. Due to the limitations of current chemotherapy, new anticancer therapies are urgently needed. 3,3 '-diindolylmethane (DIM) has been reported to have the ability to protect against various types of cancer. Our study aimed to elucidate the anticancer effect of DIM in GC when treated with the chemotherapeutic agent 5-Fu. In our results, combined treatment with DIM and 5-Fu resulted in higher apoptosis and lower cell proliferation than treatment with 5-Fu in SNU484 and SNU638 cell lines. Furthermore, when DIM and 5-Fu were administered together, cell invasion was diminished by mediated E-cadherin, MMP-9, and uPA; p-Akt and p-GSK-3 beta levels were reduced more significantly than when 5-Fu was administered alone. Moreover, in the Wnt signaling pathway, combined treatment of DIM and 5-Fu diminished beta-catenin levels in the nucleus and inhibited cyclin D1and c-Myc protein levels. The Akt inhibitor, wortmannin, further inhibited the levels of beta-catenin and c-Myc that were inhibited by DIM and 5-Fu. Furthermore, an animal xenograft model demonstrated that DIM combined with 5-Fu considerably reduced tumor growth without any toxic effects by regulating the Akt/GSK-3 beta and beta-catenin levels. Our findings suggest that DIM significantly potentiates the anticancer effects of 5-Fu by targeting the Akt/GSK-3 beta and WNT/beta-catenin because the combination therapy is more effective than 5-Fu alone, thereby offering an innovative potential therapy for patients with GC.