HPI/AMF inhibition halts the development of the aggressive phenotype of breast cancer stem cells.

Cancer stem cells are responsible for tumor recurrence and metastasis. A new highly reproducible procedure for human breast cancer MCF-7 stem cells (BCSC) isolation and selection was developed by using a combination of hypoxia/hypoglycemia plus taxol and adriamycin for 24 h. The BCSC enriched fraction (i) expressed (2–15 times) the typical stemness protein markers CD44 +, ALDH1A3 and Oct 3/4; (ii) increased its clonogenicity index (20-times), invasiveness profile (> 70%), migration capacity (100%) and ability to form mammospheres, compared to its non-metastatic MCF-7 counterpart. This isolation and selection protocol was successful to obtain stem cell enriched fractions from A549, SiHa and medulloblastoma cells. Since the secretion of HPI/AMF cytokine seems involved in metastasis, the effects of erytrose-4-phosphate (E4P) and 6-phosphogluconate (6PG), potent HPI inhibitors, on the acquisition of the breast stem cell-like phenotype were also evaluated. The presence of E4P during the BCSC selection deterred the development of the stemness phenotype, whereas both extracellular E4P (5–250 nM) and 6PG (1 μM) as well as siRNA HPI/AMF depressed the BCSC invasiveness ability (> 90%), clonogenicity index (> 90%) and contents (50–96%) of stemness (CD44, ALDH1A), pluripotency (p38 MAPK, Oct3/4, wnt/β-catenin) and EMT (SNAIL, MMP-1, vimentin) markers. The cytokine inhibitor repertaxin (10 nM) or the anti-IL-8 or anti-TGF-β monoclonal antibodies (10 μg/mL) did not significantly affect the BCSC metastatic phenotype. E4P also diminished (75%) the formation and growth of MCF-7 stem cell mammospheres. These results suggested that E4P by directly interacting with extracellular HPI/AMF may be an effective strategy to deter BCSC growth and progression. [ABSTRACT FROM AUTHOR]