Abstract
Cancer immunotherapy has revolutionized clinical oncology; however, the inherent complexity and heterogeneity of cancer present substantial challenges to achieving broad therapeutic efficacy. Tumor heterogeneity manifests not only among different patients but also within individual tumors, further complicating personalized treatment approaches. Single-cell sequencing technologies encompassing genomics, transcriptomics, epigenomics, proteomics, and spatial omics have significantly enhanced our ability to dissect tumor heterogeneity at single-cell resolution with multi-layered depth. These approaches have illuminated tumor biology, immune escape mechanisms, treatment resistance, and patient-specific immune response mechanisms, thereby substantially advancing precision oncology strategies. This review systematically examines recent advances in single-cell multi-omics technologies across various cancer research areas, emphasizing their transformative impacts on understanding tumor heterogeneity, immunotherapy, minimal residual disease monitoring, and neoantigen discovery. Additionally, we discuss current technical and analytical limitations and unresolved questions associated with single-cell technologies. We anticipate single-cell multi-omics technologies will become central to precision oncology, facilitating truly personalized therapeutic interventions.