Some breast tumors metastasize aggressively whereas others remain in a state of metastatic dormancy for months or even years. The mechanism governing such metastatic dormancy remains largely unknown. Through high-parametric single-cell mapping in mice, we identified a discrete population of CD39+PD-1+CD8+ T cells present both in primary tumors and in dormant metastasis, which was hardly found in aggressively metastasizing tumors. Using blocking antibodies, we found that dormancy depended on TNF α and IFN γ . Of note, immunotherapy reduced the number of dormant cancer cells in the lungs. Adoptive transfer of purified CD39+PD-1+CD8+ T cells prevented metastatic outgrowth. In human breast cancer, the frequency of CD39+PD-1+CD8+ but not of total CD8+ T cells correlated with delayed metastatic relapse after resection (disease-free survival), thus underlining the biological relevance of CD39+PD-1+CD8+ T cells for controlling experimental and human breast cancer. Furthermore, density of CD39+PD-1+CD8+ T cells may serve as a novel biomarker and may serve as a potential immunotherapy target. Thus, we discovered that a primary breast tumor primes a systemic, CD39+PD-1+CD8+ T cell response that is essential for metastatic dormancy in the lungs. ### Competing Interest Statement The authors have declared no competing interest.

Download data

• Downloaded 758 times
• Download rankings, all-time:
  • Site-wide: 49,088
  • In cancer biology: 1,308
• Year to date:
  • Site-wide: 123,879
• Since beginning of last month:
  • Site-wide: 68,227

Altmetric data

Downloads over time

Distribution of downloads per paper, site-wide