Ashna Babli

Cancer stem cells (CSCs) represent a critical subpopulation driving tumor initiation, progression, metastasis, and therapeutic resistance. Their remarkable plasticity and ability to self-renew underlie cancer’s resilience and recurrence following conventional treatments. Recent advances in liquid biopsy technology have transformed cancer diagnostics by enabling the minimally invasive detection and dynamic monitoring of tumor-derived materials, including circulating tumor cells, cell-free nucleic acids, and exosomes. This review synthesizes the current landscape of CSC biomarkers, encompassing classical surface markers, epigenetic and metabolic signatures, and emerging multi-omic molecular profiles. We assess how these biomarkers are integrated into advanced liquid biopsy platforms, evaluating their diagnostic sensitivity and specificity as well as their clinical utility in tracking CSC dynamics throughout cancer progression and therapy. Technical challenges such as isolating rare CSC populations and distinguishing CSC-specific signals from normal stem cells are addressed, alongside developments in single-cell analysis, computational modeling, and multiplexed marker assays enhancing biomarker precision. Furthermore, we highlight the tumor microenvironment’s role in modulating CSC phenotypes and implications for biomarker reliability. By bridging foundational CSC biology with cutting-edge technologies in liquid biopsy, this review outlines translational strategies to better detect, characterize, and target CSCs, ultimately striving to improve outcomes by overcoming therapeutic resistance and reducing cancer relapse.