gms | German Medical Science

Objective: Cancer stem cells represent a population of tumorigenic cells responsible for tumor development and growth. CD133 antigen has been described as a potential stem cell marker in human glioma that might act as biomarker to identify such a tumorigenic population. Due to their high resistance to most chemotherapeutic drugs and relatively high radioresistance, glioma stem cells might play a pivotal role in tumor recurrence and progression after radiochemotherapy. Immunohistochemical and conventional PCR findings indicated a correlation between glioma grade and the presence of CD133+ cells. Therefore, final treatment failure may occur due to a clonal accumulation of these CD133-positive cells. In order to further elucidate the role of glioma stem cells in gliomagenesis, tumor maintenance and tumor recurrence we investigated the expression levels of CD133 in different glioma patient cohorts using real-time RT-PCR.

Method: 71 tumor samples were collected from low- and high-grade glioma patients. Based on tumor grading and treatment the samples were divided into 7 subgroups (peritumoral control brain tissue, diffuse glioma, anaplastic glioma, secondary glioblastoma ± chemotherapy, primary glioblastoma ± chemotherapy). Tumor samples were snap frozen and processed for RNA and protein isolation. The quantitative expression of CD133 mRNA was assessed using real-time PCR (Qiagen Rotor-Gene Q cycler). Moreover, the results were verified by immunocytochemistry and Western Blot.

Results: The expression of CD133 mRNA in primary (mean ± SEM: 0.18±0.06) and secondary glioblastoma (0.20±0.07) prior to chemotherapy was significantly higher than in control brain tissue (0.06±0.01), diffuse glioma (0.07±0.002) and anaplastic glioma (0.05±0.01) (p<0.04). However, the CD133 expression level of patients with recurrent glioblastoma after chemotherapeutic treatment was lower than in the untreated group (primary glioblastoma (0.15±0.04) and secondary glioblastoma (0.09±0.02).

Conclusions: The results obtained in this study partially corroborate the previously published data on CD133 expression in glioblastoma based on immunohistochemical findings. However, the level of CD133 expression does not differ between gliomas WHO°II and WHO°III tumors. Quantitative PCR seems to be more sensitive compared to the other methods. WHO°IV gliomas exhibit higher CD133 expression than lower grades. Moreover, our results show that the amount of CD133+ cells slightly decreased after radiochemotherapy.