S1. RUNX1 mRNA is decreased during breast cancer progression. S2. RUNX1 does not change cell proliferation. S3. RUNX1 represses tumor growth in mammary fat pad. S4. Gate for MCF10AT1 sorting. S5. CD24high Cells have high RUNX1 expression in MCF10AT1 cells. S6. Loss of RUNX1 promotes stemness in MCF10A and MCF7 cells. S7. Overexpression RUNX1 in MCF10CA1a cells does not change BCSC population. S8. Zeb1 is expressed at low level in MCF10CA1a cells. S9. Schematic diagram of ChIP qPCR primers and amplicons over Zeb1 for ChIP-qPCR. S10. Knockdown Zeb1 in MCF10AT1 ns cells does not change cancer stem cell phenotypes.
ARTICLE ABSTRACT
Breast cancer remains the most common malignant disease in women worldwide. Despite advances in detection and therapies, studies are still needed to understand the mechanisms underlying this cancer. Cancer stem cells (CSC) play an important role in tumor formation, growth, drug resistance, and recurrence. Here, it is demonstrated that the transcription factor RUNX1, well known as essential for hematopoietic differentiation, represses the breast cancer stem cell (BCSC) phenotype and suppresses tumor growth in vivo. The current studies show that BCSCs sorted from premalignant breast cancer cells exhibit decreased RUNX1 levels, whereas ectopic expression of RUNX1 suppresses tumorsphere formation and reduces the BCSC population. RUNX1 ectopic expression in breast cancer cells reduces migration, invasion, and in vivo tumor growth (57%) in mouse mammary fat pad. Mechanistically, RUNX1 functions to suppress breast cancer tumor growth through repression of CSC activity and direct inhibition of ZEB1 expression. Consistent with these cellular and biochemical results, clinical findings using patient specimens reveal that the highest RUNX1 levels occur in normal mammary epithelial cells and that low RUNX1 expression in tumors is associated with poor patient survival.
The key finding that RUNX1 represses stemness in several breast cancer cell lines points to the importance of RUNX1 in other solid tumors where RUNX1 may regulate CSC properties.
