A227: Nuclear Akt enhances breast cancer stem-like cells through counter-regulation of p21Waf/Cip1 and p27kip1
1Linkoping University, Linkoping, Sweden,2Pomeranian Medical University, Szczecin, Poland,3University of Manitoba, Winnipeg, Canada
Cancer stem-like cells (CSCs) are a rare subpopulation of cancer cells that are capable of propagating the disease and causing cancer recurrence. Our aim is to understand the cellular localization of PKB/Akt kinase and examine whether it influences the maintenance of CSCs
We overexpressed the Akt and Akt-NLS (nuclear localization signal (Akt-NLS) in SKBR3 and MDAMB468 breast cancer cell lines. CSCs surface marker phenotype and cell cycle regulation were measured using flow cytometer upon overexpression. To understand the mechanism of Akt and Akt-NLS in the regulation of CSCs, immunofluroscence, immunoblotting, quantitative real-time PCR and colony formation assay were performed
We found that the Akt-NLS overexpressed cells showed 10-15% increase in the number of CSCs with enhanced ALDH activity, CD44+High and CD24-Low phenotype. This effect was completely reversed in the presence of Akt-specific inhibitor, Triciribine. Furthermore, cells overexpressing Akt or Akt-NLS were less likely to be in the G0/G1 phase of the cell cycle by inactivating p21Waf1/Cip1 and exhibited increased clonogenicity and proliferation
Thus, our data emphasize the importance of the intracellular localization of Akt for stemness in human breast cancer cells. Hence, it allows for the development of simpler protocols to study stemness, clonogenic potency, and for the screening of new chemotherapeutic agents that preferentially target CSCs.