Researchers at the MRC Laboratory of Medical Sciences, working with Imperial College London and the UCL Genetics Institute, have built a detailed spatial map of breast tumors that reveals distinct neighborhoods of dormant, or quiescent, cancer cells tucked inside protective pockets of surrounding tissue. The findings, published in the journal Genome Medicine, help explain a long-standing puzzle in oncology: why cancer can resurface years after a patient appears to be cancer-free.
Unlike rapidly dividing tumor cells, quiescent cells essentially go into hibernation, which lets them evade chemotherapy drugs designed to target actively dividing cells and then reactivate later. The team found these dormant cells are frequently surrounded by specific immune cells known as CXCL10-positive macrophages and by a type of connective-tissue cell called myofibroblastic cancer-associated fibroblasts, forming what the researchers describe as a protective shield around the sleeping cells, according to a ScienceDaily account of the study.
Combining two mapping techniques
To build the map, the researchers combined single-cell RNA sequencing, which reveals which genes are active inside individual cells, with spatial transcriptomics, a newer technique that preserves information about where each cell sits relative to its neighbors within the tumor. The analysis drew on publicly available tumor datasets rather than newly collected patient tissue. Because the study is observational — describing patterns in existing data rather than testing an intervention — the researchers say they cannot yet establish whether the surrounding cells actively cause dormancy or simply accumulate around cells that are dormant for other reasons.
Quiescent cancer cells are very dangerous ... they can hide from chemotherapy and remain dormant.
Dr. Alexis Barr, MRC Laboratory of Medical Sciences
Dr. Maria Secrier of the UCL Genetics Institute, who worked on the computational side of the analysis, said the team "found cells that resemble therapy-resistant cells already residing in the tumor before treatment" — suggesting some tumors may harbor the seeds of future relapse from the outset, rather than developing resistance only after drug exposure. The researchers have floated the idea that therapies targeting the complement immune pathway might be able to disrupt the protective niches around dormant cells, though they caution this remains a hypothesis that has not yet been tested experimentally.
The authors say the next phase of work will need to test these ideas directly in the lab, and eventually explore combination therapies that target both the fast-dividing majority of a tumor and the dormant minority hiding in its protective niches — an approach that, if it pans out, could take years to reach clinical trials. For now, the study adds molecular detail to a mechanism doctors have long suspected but struggled to visualize directly: that surviving cancer cells are not scattered randomly through a tumor but sheltered in specific, mappable neighborhoods.
