RUNX1 and breast cancer: In addition, when the expression of the tumor suppressor runt-related transcription factor 1 (RUNX1), a key factor in the onset and metastasis of BC, is suppressed in normal-like mammary epithelial MCF10A cells, ts-19 (32-nt ValCAC type II tsRNA) and ts-29 (24-nt TyrGTA type II tsRNA) are significantly downregulated, while ts-46 (33-nt HisGTG type II tsRNA) is upregulated.