Object: The aim of this study was to develop an improved animal model for brain tumor study. The need for better and more relevant brain tumor models is generally acknowledged. Glioma tissue can be cultured directly from the biopsy specimen as tumor spheroids. Using such precultured tissue, a new in vivo model for studying human gliomas was established.
Methods: Precultured small tumor spheroids (< 300 microm) prepared from cell lines or tumor biopsy fragments were injected into the brains of immunodeficient rats by using a 5-microl Hamilton syringe that had a piston in the needle. Tumors could be established by injecting a single spheroid derived from the U-87MG cell line, whereas inoculation of 10 spheroids resulted in a tumor take comparable to that attained with injection of 10(6) single cells. Biopsy specimens obtained from six patients who underwent surgery for glioblastoma multiforme were cultured as organotypic spheroids for 11 to 18 days before inoculation into the rats. The animals were killed 3 months after spheroid implantation. Microscopic examination revealed tumor growth in 87.5 to 100% of the animals inoculated with tumor spheroids from all but one of the tumor biopsy specimens. Extensive invasion and cell migration along the nerve tracts of the corpus callosum was found in tumors that originated from four of the six biopsy specimens.
Conclusions: This approach, in which spheroids from precultured biopsy specimens are injected into the brains of immunodeficient animals, provides new means for experimental studies of human malignant brain tumors in a clinically relevant animal model.