Scientists have created a detailed map of breast tumors, revealing that dormant cancer cells are often protected by surrounding immune and connective tissue cells.

Researchers from the MRC Laboratory of Medical Sciences, Imperial College London, and the UCL Genetics Institute have mapped the cellular structure of breast tumors. Their findings, published in Genome Medicine, show that dormant cancer cells often reside in specific regions surrounded by immune and connective tissue cells that may act as protective shields against treatment.

Dormant Cells and Treatment Resistance

Breast tumors contain both rapidly dividing cells and 'quiescent' or dormant cells that can survive standard treatments like chemotherapy, which typically target fast-growing cells. The study found that these dormant cells often exist within the tumor before any treatment is administered, suggesting that some therapy-resistant characteristics are present from the outset.

Protective Microenvironments

The research team identified that dormant cancer cells are frequently located near CXCL10-positive macrophages and myofibroblastic cancer-associated fibroblasts. These surrounding cells may form a physical or biological barrier that prevents treatments or immune cells from reaching the inactive cancer cells. Scientists are now investigating whether these supporting cells actively maintain the dormant state or if the cancer cells manipulate their environment to survive.

Future Therapeutic Implications

The study suggests that future cancer therapies may need to target both the proliferative and dormant regions of a tumor to prevent relapse. Researchers observed increased activity in the complement pathway within these dormant niches, indicating a potential target for new drug combinations. While these findings provide a new understanding of tumor evolution, the team notes that these concepts still require experimental testing.