Evaluation of stem-like side population cells in a recurrent nasopharyngeal carcinoma cell line

Abstract

BackgroundSide population (SP) assay identifies cells with dye/drug extrusion ability, a characteristic of stem cells. Here, we determined if SP cells exist in a verified cell line originating from recurrent nasopharyngeal carcinoma (NPC) and a xenograft established from recurrent metastatic NPC. These cells were evaluated for stem-like properties via functional assays as well as for tumourigenicity.MethodsWe used Hoechst 33342 to identify the SP from non-SP (NSP) cells in HK1 NPC cell line and xeno-284 NPC xenograft. The cells were assayed for in vitro characteristics of cancer stem cells (CSC), gene expression and tumourigenicity ability. Student’s t test was used to test for significance.ResultsFive to ten percent and less than 0.5% of HK1 and xeno-284 NPC cells, respectively, were SP cells. Fumitremorgin C (FTC), as opposed to verapamil, was effective in causing the cells to retain Hoechst 33342 dye. HK1 SP cells formed more holoclones, had more aldehyde dehydrogenase (ALDH) activity, divided asymmetrically and contained slow-proliferating cells. ABCG2, SOX2, TERT, MYC, Hedgehog, Notch, TGFβ and Wnt signalling pathway genes were significantly upregulated in the SP cells. However, despite these differences in vitro, both HK1 SP and NSP cells had an overall similar tumourigenic potential in vivo.ConclusionsHK1 SP cells were ABCG2-specific as confirmed by FTC inhibition and gene expression data. Despite data from in vitro and gene expression experiments suggesting stem-like features, there was no significant difference in tumourigenic potential between SP and NSP cells. We conclude that SP assay alone is not sufficient to identify CSCs in HK1 cells. Our work also suggests the presence of a stem-cell like population among NPC cells which do not display increased tumourigenicity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12935-014-0101-0) contains supplementary material, which is available to authorized users.

β-Catenin is important for cancer stem cell generation and tumorigenic activity in nasopharyngeal carcinoma

“…Nasopharyngeal CSCs have been evaluated by analyzing the number of side population (SP) cells, which appear as a dimly stained subgroup by extruding the Hoechst 33342 dye [12][13][14], as well as the expressions of octamer-binding transcription factor 3/4 (Oct3/4), sexdetermining region Y-box 2 (Sox2), c-myc, and Nanog [14]. Sufficient evidence has demonstrated that Oct3/4, Sox2, c-myc, and Nanog function as reprograming factors which can efficiently transform terminally differentiated cells into induced pluripotent stem cells [15].…”

Expression of CD44, CD44v9, ABCG2, CD24, Bmi‑1 and ALDH1 in stage I and II oral squamous cell carcinoma and their association with clinicopathological factors

“…This phenotype has been isolated from several primary tumors and cancer cell lines, including those of the lung, esophagus, nasopharynx, and oral cavity (8)(9)(10). Furthermore, ABCG2 expression has been found in solid tumors of hepatocellular, lung, pancreas, and head and neck squamous carcinomas (HNSCC) (8)(9)(10). ABCG2 plays a critical role in the maintenance of the stem cell phenotype and multidrug resistance of cancer cells (7).…”

“…A recent study suggested that the ABCG2-positive side population cells with the ability to exclude Hoechst 33342 and the possession of cancer stem-like properties may play an important role in oral carcinogenesis (9). Increasing evidence suggests ABCG2 is a marker in CSC and plays a central role in tumorigenesis (8)(9)(10).…”

“…Little is known regarding the biology or behavior of CD44, CD44V9, ABCG2, CD24, BMI-1, ALDH1 of stage I and II OSCC. We would choose those CSC marker among many reports considered important for survival rates including esophageal, lung, gastric, colorectal, and head and neck cancer (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)21,22). And the significance of expression of those markers in stage I and II OSCC remains to be determined.…”

Modeling nasopharyngeal carcinoma in three dimensions

“…5). In addition, it was previously observed that HK1 contained a subset of cells termed side population (SP) cells, which were enriched with CSC-associated genes (101). A separate study identified certain CSC genes to be responsible for the formation of spheroids in HK1 (97).…”