BSBM-17 NOVEL VALIDATED PATIENT-DERIVED MODELS OF A RECTAL CANCER BRAIN METASTASIS

Colorectal adenocarcinomas (CRC) rarely metastasize to the brain, however, survival rates in patients with colorectal brain metastases (CBM) are short, with a median survival of only 4 months from diagnosis. Currently, no evidence-based treatment options against these rare brain metastases are available (PMC). Therefore, characterization of these tumors and development of targeted therapies are imperative. Optimal models for neoplasms heighten the notoriously low success rate of bench-to-bedside translation. Historically, brain cancer metastases models are established cell lines grown on plastic and transplanted as xenografts (Valiente; PMC7572582). Genomic drift, lack of genetic accuracy and heterogeneity, caused by serial passaging on plastic and in high-serum media, are frequent limitations of these models. Growth in defined media without serum and as 3-dimensional (3-D) spheroids or organoids is thought to improve the fidelity of cancer cell lines (Lee; PMID:16697959; Lo; PMC820864). Despite significant efforts of large collaborative projects (https://hcmi-searchable-catalog.nci.nih.gov/), 3-D rectal brain cancer metastasis models have not been reported. To address this unmet medical need, we developed 3-D (suspension, organoid) cultures of a rectal adenocarcinoma brain metastasis with moderate to focally poor differentiation. Next-generation sequencing, expression profiling, and immunohistochemistry were performed to validate our models. Our data confirmed that the PDO model contains tumor cells; pathogenic alterations and expression profiles in the models largely match that of the original tumor. Overall, we detected a significant phenotypic overlap with the original tumor sample. Spatial profiling and PDO-derived xenografts are in progress and will facilitate experimental therapeutics. Taken together, our models retained tumor heterogeneity and fidelity from the primary tumor, making this one of the first studies to establish 3-D patient-derived models for disease progression in rectal cancer brain metastases. Collectively, these models will be valuable translational tools for future exploration of targeted therapy, which remains absent in this disease process.