BACKGROUND & AIMS:Cholangiocarcinoma (CCA) is a lethal malignancy with limited therapeutic options. We investigated the oncogenic role of poly(ADP-ribose) glycohydrolase (PARG) and evaluated potential therapeutic strategies.
METHODS:A tissue microarray comprising 275 CCA patient samples was analyzed by immunohistochemistry. Liquid chromatography-tandem mass spectrometry was utilized to identify downstream targets of PARG. Transgenic mice (Pargf/f) were employed to establish a spontaneous CCA model via hydrodynamic tail vein injection and biliary instillation. The efficacy of PARG inhibition was assessed in multiple preclinical models, including patient-derived organoids, patient-derived xenografts, orthotopic xenografts, and an immunocompetent syngeneic murine model. Cytometry by time-of-flight analysis was used to profile changes in the tumor microenvironment following PARG inhibition and anti-PD-1 therapy.
RESULTS:PARG was highly expressed in CCA and predicted a dismal prognosis based on analysis of a large patient cohort. Genetic depletion of Parg in spontaneous CCA models induced by two methods, including hydrodynamic tail vein injection and biliary instillation, significantly halted carcinogenesis. PARG inhibition alone showed impressive efficacy and potentiated that of gemcitabine/cisplatin in patient-derived organoid, patient-derived xenograft, and orthotopic models. Mechanistically, PARG dePARylates ITCH, suppressing its autoubiquitination and thereby inhibiting the Hippo pathway, which promotes CCA proliferation and chemoresistance. Moreover, cytometry by time-of-flight analysis revealed crosstalk between the tumor and stroma, which could be suppressed by PARG inhibitors via the TEADs/CXCR4/CXCL12 axis. Combining PD-1 blockade and gemcitabine/cisplatin with PARG inhibitors resulted in a significantly greater reduction in tumor burden, as well as a survival benefit.
CONCLUSIONS:Targeting PARG limits CCA progression, alleviates desmoplasia, and enhances response to both anti-PD-1 therapy and chemotherapy.
IMPACT AND IMPLICATIONS:Little is known about the role of PARG in cholangiocarcinoma (CCA) development and progression. Herein, we show that PARG expression is upregulated and hyperactivated in CCA, promoting tumor cell proliferation, cancer-associated fibroblast recruitment, and resistance to therapy. Pharmacological inhibition of PARG suppresses CCA development and could be an effective therapeutic strategy when combined with chemotherapy and immunotherapy.
