Abstract PO025: GM-CSF neutralization enhances the efficacy of chemotherapy in an orthotopic murine model of cholangiocarcinoma

Abstract

Abstract Introduction: With current effective treatments in cholangiocarcinoma (CCA) lacking, we expounded on our prior work highlighting the critical role of the granulocyte-macrophage-colony stimulating factor ligand/receptor (GM-CSF/GM-CSFRα) signaling pathway by evaluating GM-CSF neutralization combined with first-line chemotherapy in a novel murine model of CCA. Methods: Resected CCA specimens were used to construct a human tissue macro-array. Immunohistochemistry (IHC) staining for GM-CSFRα and digital quantification of staining intensity was performed. A novel syngeneic CCA cell line derived from spontaneous murine CCA from LSL-KrasG12D; Tp53Flox/Flox −; Alb-Cre (KPPC) mice was surgically injected into the left hepatic lobes of C57BL/6J mice. Disease onset and extent of progression was monitored over time using ultrasonography (US) in groups of mice enrolled into treatment with vehicle, gemcitabine, anti-GM-CSF, and gemcitabine plus anti-GM-CSF. Mice were sacrificed at predetermined endpoints for flow cytometry analysis. Results: IHC analysis and digital quantification of resected human tumors demonstrated that CCA expresses significantly higher levels of GM-CSFRα (p<0.01) compared to uninvolved normal liver. Mice injected with a novel syngeneic CCA cell line expressing high levels of GM-CSF protein uniformly developed tumors fourteen days after orthotopic implantation. Histopathological evaluation of orthotopic CCA tumors demonstrated faithful recapitulation of both spontaneous murine and human disease with marked development of malignant biliary ductal epithelium (CK7), desmoplastic stroma (Sirius red, trichrome), and prominent inflammatory leukocytic infiltrate (CD45). Flow cytometry analysis of end-stage orthotopically implanted tumors demonstrated a progressive expansion of myeloid cells (70.7% CD11b+) compared to CD8+ (0.8%) and CD4+ (2.0%) T cells, indicative of a highly immunosuppressive tumor immune microenvironment. Combination therapy with GM-CSF neutralization and chemotherapy significantly reduced tumor size as screened via US compared to vehicle (p<0.0001), anti-GM-CSF (p<0.01), and chemotherapy alone (p<0.01). In addition, combination therapy reduced the rate of tumor growth compared to each of the three other treatment groups (all p<0.0001). Finally, tumor weights were significantly reduced in the combination therapy group versus the vehicle (p<0.0001), anti-GM-CSF (p<0.001), and chemotherapy alone (p<0.05) cohorts. Conclusion: Human CCA demonstrates elevated levels of GM-CSFRα compared to normal liver. Neutralization of GM-CSF in combination with chemotherapy reduced tumor growth and weight in a novel murine model of CCA. Targeting the GM-CSF/GM-CSFRα pathway represents an innovative means of improving tumor control in CCA. Citation Format: Yatee A Dave, Paul R Burchard, Nicholas A Ullman, Mary Georger, Luis I Ruffolo, Brian A Belt, David C Linehan. GM-CSF neutralization enhances the efficacy of chemotherapy in an orthotopic murine model of cholangiocarcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr PO025.