Breast Cancer Disseminated Tumor Cells: Do They Stay and Fight or Run and Hide?

Many solid tumors including breast cancer can exhibit early dissemination and dormancy-in which cancer cells spread early in the disease process and survive long periods without detectable growth. These early disseminated tumor cells sometimes reactivate and lead to incurable metastatic disease years or even decades after curative-intent therapy for the primary tumor. We are just beginning to understand the role of the immune system in this process in part because of improvements in immunocompetent models as well as technological advances such as single-cell genomics and spatial transcriptomics. In this issue of Cancer Research, Bushnell and colleagues showed that NK cells are important in this context. The authors found that disseminated tumor cells and quiescent cells express higher levels of MHC 1 but are resistant to NK-cell-mediated immunity. The proposed mechanism involves the STING pathway and transcription factors Sox2 and Bach1. As other studies have highlighted the importance of T-cell immunity, this work reaffirms the importance and diversity of immune regulation of dormancy and suggests the need for future studies to flesh out mechanistic details and predict when each type of immunity is most important. See related article by Bushnell et al., p. 3337.