gms | German Medical Science

Objective: The cancer stem cell hypothesis postulates that a small population of cancer cells possess self-renewal characteristics and is responsible for initiating and maintaining tumour growth. Several putative markers have been described to identify and isolate the cancer stem cell population in glioblastoma. However, these markers are still inadequate to specifically identify glioma stem cells. Nevertheless, there is an increasing interest in studying stem cell properties in glioblastoma cells as potential therapeutic targets. Therefore, we aimed to investigate a set of key stemness - and progenitor genes in established glioblastoma cell lines.

Method: RNA was isolated from 5 cell lines: U87 as a commercially available established glioblastoma cell line, Gl36 as a tumor derived primary glioblastoma cell line, HES2 (human embryonic stem cells), NPC (neuronal progenitor cells) as positive control and hDF (human dermal fibroblasts) as a negative control. After cDNA synthesis PCR was performed in order to investigate a set of stemness genes (Nanog, Oct4, Klf4, Lin28 and cMyc) as well as neuronal progenitor genes (Sox1, Pax6, Olig2, CD133). The PCR bands were evaluated semiquantitatively by densitometry. Experiments were performed in triplicates. Protein expression was confirmed by Western blot analysis and cell stainings.

Results: A subset of stemness and progenitor genes is differentially expressed in both investigated tumor cell lines. GI36 cells showed expression of Oct4, Klf4, and Lin28, whereas Oct4 and Pax6 were identified in U87 cells. Overall, Pax6 was the only detectable neuronal progenitor marker in both tumor cell lines. Furthermore, cMyc was expressed in both tumor cell lines, while neither of them showed any signs of CD133. The expression profile was verified by Western blots and immunocytochemistry.

Conclusions: Our results show the expression of a subset of stemness and neuronal progenitor genes in two glioblastoma cell lines. These findings are in line with previously published data showing the expression of stemness genes in primary tumor cell lines. The latter ones lost parts of their stemness gene expression after serial passaging. Interestingly, we found a distinct expression pattern in an established glioblastoma cell line compared to a primary cell line, emphasizing the caution necessary when extrapolating results derived from established cell lines.