Splicing Factor SF3B4 Suppresses Pancreatic Cancer Growth and Migration by Inhibiting Autophagy.

[BACKGROUND/AIM] Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, characterized by aggressive progression, profound chemoresistance and unique metabolic adaptations such as elevated autophagy. Although the splicing factor SF3B4 has been reported to function as an oncogene in other malignancies, its role in PDAC remains unclear. This study aimed to elucidate the functional and mechanistic significance of SF3B4 in PDAC.

[MATERIALS AND METHODS] SF3B4 expression in PDAC was analyzed using patient datasets and experimental models. Functional assays including cell proliferation, colony formation, migration, and autophagy analyses were performed in PDAC cells. Reactive oxygen species (ROS) levels were evaluated. Sensitivity to 5-fluorouracil (5-FU) and apoptotic responses were also evaluated.

[RESULTS] SF3B4 acts as a tumor suppressor in PDAC by inhibiting autophagy, a process that this cancer uniquely depends on for survival. SF3B4 overexpression inhibited proliferation, colony formation and migration of PDAC cells. Mechanistically, SF3B4 suppressed autophagic flux, resulting in increased ROS accumulation and subsequent inhibition of tumorigenic phenotypes. Treatment with the antioxidant N-acetylcysteine (NAC) rescued the tumor suppressive effects of SF3B4 overexpression. Moreover, SF3B4 overexpression sensitized PDAC cells to 5-FU, accompanied by enhanced apoptotic responses.

[CONCLUSION] SF3B4 is a context-dependent splicing factor that functions as a tumor suppressor in PDAC by regulating autophagy and redox homeostasis. Targeting the SF3B4-autophagy-ROS axis may represent a promising strategy to suppress PDAC progression and overcome chemoresistance.