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Bone Marrow Research
Volume 2011 (2011), Article ID 524845, 8 pages
Research Article

Factors Influencing the Abundance of the Side Population in a Human Myeloma Cell Line

1The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China
2Faculty of Pharmacy, The University of Sydney, Sydney, NSW 2006, Australia
3Institute of Haematology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
4Centenary Institute of Cancer Medicine and Cell Biology, The University of Sydney, Sydney, NSW 2006, Australia
5Faculty of Medicine, The University of New South Wales, Sydney, NSW 2052, Australia
6Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Received 21 March 2011; Accepted 26 July 2011

Academic Editor: Ignazio Majolino

Copyright © 2011 Sui-Lin Mo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Side population (SP) refers to a group of cells, which is capable to efflux Hoechst 33342, a DNA-binding dye. SP cells exist both in normal and tumor tissues. Although SP abundance has been used as an indicator for disease prognostic and drug screening in many research projects, few studies have systematically examined the factors influencing SP analysis. In this study we aim to develop a more thorough understanding of the multiple factors involved in SP analysis including Hoechst 33342 staining and cell culture. RPMI-8226, a high SP percentage (SP%) human myeloma cell line was employed here. The results showed that SP% was subject to staining conditions including: viable cell proportion, dye concentration, staining cell density, incubation duration, staining volume, and mix interval. In addition, SP% was highest in day one after passage, while dropped steadily over time. This study shows that both staining conditions and culture duration can significantly affect SP%. In this case, any conclusions based on SP% should be interpreted cautiously. The relation between culture duration and SP% suggests that the incidence of SP cells may be related to cell proliferation and cell cycle phase. Maintaining these technical variables consistently is essential in SP research.