Cao et al. BMC Cancer 2010, 10:68 http://www.biomedcentral.com/1471-2407/10/68 R E S E A R C H A R T I C L E Open Access Pluripotency-associated genes in human nasopharyngeal carcinoma CNE-2 cells are reactivated by a unique epigenetic sub-microenvironment Jun-Xia Cao1,2*, Yu-Xin Cui3, Zi-Jie Long4, Zhong-Min Dai5, Ji-Yan Lin6, Yi Liang1, Fei-Meng Zheng1, Yi-Xin Zeng1, Quentin Liu1,4* Abstract Background: There is increasing evidence that cancers contain their own stem-like cells, and particular attention has been paid to one subset of cancer-stem cells termed side population (SP). Stem cells under normal physical conditions are tightly controlled by their microenvironment, however, the regulatory role of the microenvironment surrounding cancer stem cells is not well characterized yet. In this study we found that the phenotype of SP can be “generated” by macrophage-like cells under conditioned culture. Furthermore the gene regulation pathway involved in cellular reprogramming process was investigated. Methods: The selection and identification of SP in 50 CNE-2 single cell clones were performed by flow cytometry. The transwell assay and immunofluorescence staining were used to measure migration and cancer stem cell characters of non-SP single clone cells cultured with conditioned medium respectively. The subtraction suppression hybridization (SSH) technique and northern blotting analysis was applied to explore the pluripotency-associated genes under a unique epigenetic sub-microenvironment. Results: Among 50 clones, only one did not possess SP subpopulation while others did. The non-SP cells induced by macrophage-like cells showed more aggressive characters, which increased cell migration compared with the control cells and showed some fraction of SP phenotype. These cells expressed distinguished level of pluripotency- associated genes such as ADP-ribosylation factor-like 6 interacting protein (ARMER), poly (rC) binding protein 1 (PCBP1) and pyruvate dehydrogenase E1-b subunit (PDHB) when subjected to the environment. Conclusion: To our knowledge, this is the first study to demonstrate that non-SP single-clone cells can be induced to generate a SP phenotype when they are cultured with conditioned medium of macrophage-like cells, which is associated with the reactivation of pluripotency-associated genes. Background The hypothesis of cancer stem cell (CSC) suggests that neoplastic clones are maintained exclusively by a small subpopulation of cells that give rise to phenotypically diverse cancer cells [1-3]. CSCs were first identified in 1990s in hematological malignancies, mainly acute mye- logenous leukemia (AML) and also in other subtypes like AML M0, M1, M2, M4, and M5, chronic myeloid * Correspondence: jun-xia.cao@jax.org; liuq9@mail.sysu.edu.cn 1State Key Laboratory of Oncology in South China, Cancer Center, Sun Yat- sen University, 650 Dongfeng Road, Guangzhou 510060, PR China leukemia (CML), acute lymphoblastic leukemia (ALL), and multiple myeloma [4,5]. This subset of cancer cells was also found in solid tumors in the breast, brain, lung, prostrate, testis, ovary, stomach, colon, skin, liver and pancreas [6-11]. Thus, there is overwhelming evidence that certain pathways which regulate or maintain the extensive proliferative and self-renewal potential of the tumor clone are present in CSC. It is known that niches control stem cell function, thus it may seem counterintuitive that CSCs would be located within these regulatory microenvironments. © 2010 Cao et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.