Article
Multicolor labeling of EGFR-amplified glioblastoma cells allows for tracking of individual cell clones in vitro and in vivo
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Published: | May 21, 2013 |
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Objective: The current study aimed at analyzing the molecular requirements for tumor initiation of EGFR-amplified, EGFRvIII-positive glioblastoma (GBM) cells in vitro and in vivo.
Method: GBM-derived EGFR-amplified, EGFRvIII-positive BS153 cells were analyzed for their tumor-initiating capacity in vitro in soft agar assays and in vivo in a xenograft mouse model using NMRI/Foxn1nu-mice. For tracking of individual cell clones, the cells were labeled using a recently described lentivirus-based method called RGB-marking (Weber et al, Nature Medicine, 2011). Labeled cells were subsequently implanted into nude mice and the resulting tumors analyzed by fluorescence microscopy and immunohistochemistry.
Results: EGFR-amplified, EGFRvIII-positive cells developed anchorage-independent spheroids in vitro, pointing towards their ability to serve as a novel in vivo model of EGFR-amplified GBM. When analyzed for their tumor-initiating capacity in vivo, we found that mice injected with BS153 developed symptoms due to tumor burden within eight weeks. Markedly, the experimental tumors displayed an unusual, invasive morphology, probably attributed to EGFR overexpression. Fluorescent in vitro-RGB-marking of BS153 produced individually labeled single cells resulting in hundreds of differently colored cell clones. Surprisingly, when implanted into nude mice, tumors developed with only a limited number of colors (<10) indicating that only a restricted number of cells have the ability to initiate tumors in vivo.
Conclusions: We present a novel, EGFR-amplified in vitro and in vivo model system that allows for the analysis of the impact of EGFR amplification on EGFR-directed therapies in a natively amplified background. Furthermore, by tracking individually labeled cell clones in vivo, we are able to determine the molecular requirements for tumor initiation in the context of EGFR amplification.