Molecular analysis of tumor recurrence using established cancer stem cell-line and drug discovery

Despite advances in adjuvant therapy for colorectal cancer, tumor relapses, often driven by minimal residual disease, remain a formidable clinical challenge. The cancer stem cell hypothesis provides a key framework for understanding this problem, positing that a small, therapy-resistant subpopulation of cells drives recurrence. To elucidate the role of these cells, we developed LGR5-specific monoclonal antibodies and a high-sensitivity immunofluorescence method to visualize the stem cell marker LGR5 in clinical tumors. Furthermore, we established a unique colorectal cancer cell line, PLR123, which maintains robust stem cell properties, and developed an in vitro model to study tumor recurrence. Through analyses including single-cell RNA sequencing and small molecule screening, we identified the RNA Polymerase I inhibitor BMH-21 as a compound that effectively suppresses recurrence both in vitro and in vivo. This article comprehensively reviews our series of studies on understanding the mechanisms of cancer stem cell-driven resistance and offers insights supporting the development of novel therapies aimed at preventing tumor relapses.