gms | German Medical Science

Objective: Glioblastoma is the most common and aggressive primary brain malignancy. Stem-like tumor cells have been shown to more closely resemble the patient tumor. However, they vary markedly regarding growth and marker expression. Therefore the aim of the following study was to carefully characterize SLGC-lines based on their in vitro self renewal potential, in vivo tumorigenicity and expression of the surrogate marker AC133.

Method: Neural colony-forming cell assay (NCFCA) was performed in a collagen matrix on 7 SLGC lines to quantify their self renewal potential. Then 104 cells of each cell line were implanted orthotopically into non-obese diabetic immunodeficient (NOD SCID) mice and monitored for a period of 8 weeks (short-term). In addition, for 5/7 cell lines observation period was prolonged (long-term) and for 3/7 SLGCs the implanted cell number was increased to 106 cells/mouse. Cryosections of the brains were analyzed for tumorigenicity, invasiveness, neoangiogenesis and proliferative potential. Furthermore DiI-labeled SLGC tumorspheres were implanted into a cranial window chamber in nude mice. Tumor growth, cell migration and angiogenesis were monitored using a fluorescence intravital microscope (IVM) during a 17-days observation period.

Results: Neural colony forming assay (NCFCA) revealed clonogenicity ranging from 0,13% to 18%. Concordantly, in our short-term approach 4/5 highly clonogenic cell lines developed tumors with 100% penetrance resulting in a decreased symptom-free survival. Tumor penetrance was associated with a higher AC133 content. In our long-term approach and after implanting increased cell numbers even AC133low cell lines developed tumors. However, the latter were less dense and more infiltrative. In contrast, superficial implantation in the window chamber model revealed an aberrant vascular network with microvascular proliferation for all SGLC lines but was not able to delineate growth differences observed after intracranial implantation.

Conclusions: Our findings indicate distinct types of SLGCs differing in their clonogenicity, AC133 content and tumorigenicity. Furthermore the length of the observation period needs to be taken into account when planning in vivo experiments with SLGCs.