Novel Syngeneic Cell Lines for Studying High-Risk BRAFV600E-Driven Colorectal Cancer In Vivo

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• BRAFV600E-driven colorectal cancer (CRC) presents poor prognosis and short-lived responses to current therapies.
• Combining anti-EGFR antibodies with BRAF/MEK/ERK pathway blockade offers new treatment avenues but faces challenges due to tumor heterogeneity.
• There is a critical need for immunocompetent mouse models that accurately reflect CRC disease onset and drug responses for preclinical research.

Purpose of the Study:

• To generate and characterize novel cell lines from BRAFV600E-driven colorectal cancer (CRC) metastases.
• To assess the responses of these cell lines to clinically relevant targeted therapies, including RAF inhibitors (RAFi) and EGFR inhibitors.
• To establish a preclinical tool for studying tumor heterogeneity, drug resistance, and the tumor microenvironment in BRAFV600E-driven CRC.

Main Methods:

• Generation of three cell lines (NaJa lines) from peritoneal metastases of orthotopically transplanted organoids with BRAFV600E, Trp53R172H, and Apc mutations.
• Comprehensive characterization using RNA sequencing, whole exome sequencing, and functional assays to determine ground state and drug responses.
• In vivo studies involving re-transplantation into syngeneic mice to evaluate tumor growth and microenvironment.

Main Results:

• The NaJa cell lines exhibited distinct differentiation states and heterogeneous responses to RAF inhibitors (encorafenib, exarafenib), mirroring clinical CRC heterogeneity.
• Resistance to RAFi was overcome by the EGFR-family inhibitor afatinib.
• RAFi treatment modulated the expression of antigen presentation machinery, cytokines, and other immunomodulatory factors.
• Transplanted NaJa lines formed aggressive tumors with distinct microenvironments reflecting their differentiation states.

Conclusions:

• The NaJa cell lines provide a valuable and unique preclinical tool for investigating tumor heterogeneity and drug resistance in BRAFV600E-driven CRC.
• These models facilitate the study of the complex interplay between tumor cells, stroma, and immune cells in the context of targeted therapy and immuno-oncology.
• The findings support further research into novel therapeutic strategies for BRAFV600E-driven CRC by integrating targeted agents and immunotherapy.