Abstract 6808: DOCK1 as a therapeutic target for EGFR resistance in cholangiocarcinoma

Abstract Cholangiocarcinoma (CCA) is an aggressive cancer of the bile ducts, characterized by poor prognosis and limited treatment options due to late-stage diagnosis and resistance to targeted therapies. Mutations in critical pathways, including the Epidermal Growth Factor Receptor (EGFR) and Fibroblast Growth Factor Receptor (FGFR), drive CCA progression, while resistance mechanisms and mutation weaken the effectiveness of available therapies. Dedicator of Cytokinesis 1 (DOCK1), a guanine nucleotide exchange factor, has emerged as a key player in cancer progression, particularly in modulating cell signaling. In this study, we investigated the therapeutic potential of targeting DOCK1 in CCA via modulating EGFR signaling. Our assessment across five distinct patient cohorts demonstrates that DOCK1 is significantly overexpressed in CCA tumors compared to normal cholangiocytes, underscoring its pivotal role in promoting tumor growth and aggressiveness. Pharmacological inhibition of DOCK1 using the small-molecule inhibitors CPYPP and TBOPP, as well as siRNA-mediated knockdown, resulted in a marked reduction in HuCCT1 and EGI1 CCA cell lines proliferation and migration. This was accompanied by an increase in tumor suppressor proteins p53 and p21, along with a decrease in proliferation markers PCNA and cyclin D1. Moreover, siRNA-mediated reduction of DOCK1 expression significantly induced apoptosis and cytotoxicity, accompanied by elevated levels of cleaved caspase-3 and PARP1, highlighting its role in driving cell death resistance in CCA. Furthermore, DOCK1 inhibition disrupted EGF-stimulated EGFR phosphorylation and downstream signaling through Erk1/2, a critical pathway supporting tumor growth, survival, and therapeutic resistance. These findings position DOCK1 as a central enhancer of EGFR-mediated oncogenic signaling, playing a key role in the aggressive phenotype and therapeutic resistance of CCA. Targeting DOCK1 not only suppressed tumor cells proliferation but also enhanced cell death, offering a dual therapeutic advantage. Our study provides strong evidence supporting DOCK1 as a promising therapeutic target and suggests that its inhibition, particularly in combination with EGFR-targeted therapies, could overcome EGFR mutant and drug resistance mechanisms and improve clinical outcomes in CCA. By unveiling this novel therapeutic strategy, our research lays the foundation for advancing more effective and stable treatments for this aggressive and often deadly malignancy. Citation Format: Kishor Pant, Kory Engelstad, Estanislao Peixoto, Ainhoa Lapitz, Jesus M. Banales, Adrian Mansini, Sergio A. Gradilone. DOCK1 as a therapeutic target for EGFR resistance in cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6808.