A novel DDIT3 activator dehydroevodiamine effectively inhibits tumor growth and tumor cell stemness in pancreatic cancer.

[BACKGROUND] The existence of pancreatic cancer stem cells (PCSCs) results in limited survival benefits from current treatment options. There is a scarcity of effective agents for treating pancreatic cancer patients. Dehydroevodiamine (DeHE), a quinazoline alkaloid isolated from the traditional Chinese herb Evodiae fructus, exhibited potent inhibition of pancreatic ductal adenocarcinoma (PDAC) cell proliferation and tumor growth both in vitro and in vivo.

[METHODS] The cytotoxic effect of DeHE on PDAC cells was assessed using CCK-8 and colony formation assays. The antitumor efficacy of DeHE were appraised in human PANC-1 xenograft mouse model. Sphere formation assay and flow cytometry were employed to quantify the tumor stemness. RNA-Seq analysis, drug affinity responsive target stability assay (DARTS), and RNA interference transfection were conducted to elucidate potential signaling pathways. Western blotting and immunohistochemistry were utilized to assess protein expression levels.

[RESULTS] DeHE effectively inhibited PDAC cell proliferation and tumor growth in vitro and in vivo, and exhibited a better safety profile compared to the clinical drug gemcitabine (GEM). DeHE inhibited PCSCs, as evidenced by its suppression of self-renewal capabilities of PCSCs, reduced the proportion of ALDH cells and downregulated stemness-associated proteins (Nanog, Sox-2, and Oct-4) both in vitro and in vivo. Furthermore, there is potential involvement of DDIT3 and its downstream DDIT3/TRIB3/AKT/mTOR pathway in the suppression of stemness characteristics within DeHE-treated PDAC cells. Additionally, results from the DARTS assay indicated that DeHE interacts with DDIT3, safeguarding it against degradation mediated by pronase. Notably, the inhibitory capabilities of DeHE on PDAC cell proliferation and tumor stemness were partially restored by siDDIT3 or the AKT activator SC-79.

[CONCLUSION] In summary, our study has identified DeHE, a novel antitumor natural product, as an activator of DDIT3 with the ability to suppress the AKT/mTOR pathway. This pathway is intricately linked to tumor cell proliferation and stemness characteristics in PDAC. These findings suggest that DeHE holds potential as a promising candidate for the development of innovative anticancer therapeutics.