RESUMO
In recent years, cancer stem cells have become a hotspot for global researchers. Cancer stem cell theory deems that cells with self-renewal and differentiation potential play a key role in tumor resistance and relapse. These cells are named cancer stem cells. At present, the sorting methods include the side population cell sorting technique, screening techniques based on cell surface special markers, tumor sphere cultures, label retaining cell, ALDEFLUOR assays and so on. Side population cells are a small part of cells with the capacity of efflux DNA fluorescent dye Hoechst 33342 and present a low staining intensity in flow cytometry plot. Side population cells are rich in cancer stem cells, and its sorting method has been considered simple and effective in cancer stem cell research.