Dynamic Phenotypic Transition of Breast Cancer Cells In Vitro Revealed by Self-floating Cell Culture

Abstract

Background: Breast tumor heterogeneity leads to phenotypic diversity, such as tumor-initiating and metastatic properties and drug sensitivity. Materials and Methods: We found that a self-floating cell (SFC) culture enriches a drug-resistant subpopulation in a HER2-positive breast cancer cell line. SFCs were analyzed for cancer stem cell markers, gene expression profiles, and sensitivity for anticancer drugs. Results: SFCs expressed cancer stem cell markers, such as aldehyde dehydrogenase (ALDH) activity and elevated HER2 autophosphorylation. Gene expression profiles of SFCs showed a dramatic difference compared to those of parental or forced floating cells. SFCs also expressed CD133, a marker of drug resistance, and resisted cytotoxic drugs by drug efflux transporters. In contrast, HER2 kinase inhibitors efficiently reduced SFC viability. Conclusion: SFCs enrich drug-resistant subpopulations even in vitro and might reflect the highly plastic nature of breast cancer cells even in vitro.