A map of human breast cancer: new players in stromal-immune crosstalk

NR2F1, a Tumor Dormancy Marker, Is Expressed Predominantly in Cancer-Associated Fibroblasts and Is Associated with Suppressed Breast Cancer Cell Proliferation

BACKGROUND

Tumor dormancy is a crucial mechanism responsible for the late recurrence of breast cancer. Thus, we investigated the clinical relevance of the expression of NR2F1, a known dormancy biomarker.

METHODS

A total of 6758 transcriptomes of bulk tumors from multiple breast cancer patient cohorts and two single-cell sequence cohorts were analyzed.

RESULTS

Breast cancer (BC) with high NR2F1 expression enriched TGFβ signaling, multiple metastases, and stem cell-related pathways. Cell proliferation-related gene sets were suppressed, and MKi67 expression was lower in high NR2F1 BC. In tumors with high Nottingham grade, NR2F1 expression was found to be lower. There was no consistent relationship between NR2F1 expression and metastasis or survival. Cancer mutation rates, immune responses, and immune cell infiltrations were lower in high NR2F1 tumors, whereas the infiltration of stromal cells including cancer-associated fibroblasts (CAFs) was higher. NR2F1 was predominantly expressed in CAFs, particularly inflammatory CAFs, rather than in cancer cells, consistently in the two single-cell sequence cohorts.

CONCLUSIONS

NR2F1 expression in breast cancer is associated with tumor dormancy traits, and it is predominantly expressed in CAFs in the tumor microenvironment.

A map of human breast cancer: new players in stromal-immune crosstalk

Prominent accumulation of mesenchymal cells within tumors has long been appreciated, and recent studies suggest molecular and functional diversity of stromal components. In this issue, Wu et al (2020) employed single-cell RNA sequencing of primary human breast tumors and identified new subsets of stromal mesenchymal cells with distinct transcriptional profiles, tissue localization, and associative immune microenvironments.