Dual Oncogenic Mechanisms of Clonorchis sinensis-Derived Csi-miR-125a in Promoting Cholangiocarcinoma Progression via BAK1 Targeting and ERK Activation

Cholangiocarcinoma (CCA) is an aggressive malignancy with a poor prognosis that is strongly associated with chronic Clonorchis sinensis (C. sinensis, Cs) infection; however, its underlying molecular mechanisms remain elusive. Recent studies suggest that C. sinensis-derived extracellular vesicles (CsEVs) play a crucial role in host–parasite interactions and in shaping the tumor microenvironment during infection. Acting as key delivery vehicles, these CsEVs can transfer specific functional molecules, such as microRNAs (miRNAs), to host cholangiocytes, thereby modulating cellular behaviors—a process that may represent a significant pathway in parasite-induced carcinogenesis. Despite this, the specific miRNAs shuttled by CsEVs and their concrete functions and mechanisms in driving CCA proliferation and metastasis remain largely unexplored. To this end, we investigated Csi-miR-125a, a miRNA abundantly expressed in CsEVs, aiming to systematically elucidate its dual regulatory functions in CCA progression. Our findings offer novel mechanistic insights into host–parasite crosstalk, further the understanding of CCA pathogenesis, and point to potential therapeutic avenues. Using gain-and loss-of-function approaches in RBE and HuCCT1 cell lines, we demonstrated that Csi-miR-125a promotes cell proliferation by accelerating cell-cycle progression and suppressing apoptosis through direct targeting of BAK1. Concurrently, Csi-miR-125a enhances the migratory and invasive capacities of CCA cells via activation of the ERK signaling pathway. In a BALB/c nude mouse lung metastasis model, CsEVs depleted of Csi-miR-125a significantly inhibited pulmonary metastasis. Collectively, This study found that Csi-miR-125a derived from C. sinensis can regulate apoptosis and cell cycle progression by targeting BAK1, thereby promoting the proliferation of cholangiocarcinoma cells; meanwhile, it enhances cell migration and invasion by activating the ERK signaling pathway. These results suggest that Csi-miR-125a participates in and promotes the malignant progression of CCA. However, given its high homology with human endogenous miR-125a, its function may partially overlap with host endogenous miRNAs, rather than representing a completely independent carcinogenic effect. These findings provide mechanistic insights into host–parasite interactions during C. sinensis infection and lay a theoretical foundation for subsequent targeted intervention studies.