CD15 and CD15s expression is associated with G1 phase of the cell cycle in glioma cell lines

Overexpression of the tetrasaccharide carbohydrate epitopes, CD15 and CD15s are associated with non-central nervous system malignancies. While CD15 and CD15s expression is rare in gliomas, recent reports suggest that CD15 may serve as a marker for brain tumour stem-like cells. The aim of this study was to determine if this apparent discrepancy may, in part, be explained by temporal expression of CD15 and CD15s at different phases of the cell cycle. We used flow cytometry, immunocytochemistry and a fluorescence cell cycle indicator (FUCCI) system to examine expression in glioblastoma (GBM) cells (UP-007 and SNB-19) and non-neoplastic astrocytes (SC-1800) synchronised via serum starvation, Hydroxyurea and Nocodazole, respectively. CD15 and CD15s expression was significantly increased in glioma cells synchronised to G1 phase compared with non-synchronised cells (p<0.001). This was supported by qualitative results obtained with the (FUCCI) system. Few studies have considered the possibility of cell-cycle dependent CD15 and CD15s expression which may explain the inconsistencies reported in the literature in terms of expression in glioma stem-like cells where cells are more likely in S phase where CD15 and CD15s expression would be low.