Detection of Brain Tumor Invasion and Micrometastasis in... : Neurosurgery (original) (raw)

Experimental Studies

Detection of Brain Tumor Invasion and Micrometastasis in Vivo by Expression of Enhanced Green Fluorescent Protein

MacDonald, Tobey J. MD; Tabrizi, Peyman MD; Shimada, Hiroyuki MD, PhD; Zlokovic, Berislav V. MD, PhD; Laug, Walter E. MD

Departments of Pediatrics (TJM, WEL), Neurosurgery (PT, BVZ), and Pathology (HS), Division of Hematology-Oncology, the Neil Bogart Memorial Laboratories, Childrens Hospital of Los Angeles (TJM, HS, WEL); and the Norris Cancer Center (PT, BVZ), University of Southern California School of Medicine, Los Angeles, California

Received, March 27, 1998. Accepted, June 4, 1998.

Reprint requests: Walter E. Laug, M.D., Division of Hematology-Oncology, Childrens Hospital of Los Angeles, 4650 Sunset Boulevard, M/S 54, Los Angeles, CA 90027.

Abstract

OBJECTIVE:

To determine whether fluorescence from human brain tumor cells transfected with the enhanced green fluorescent protein (EGFP) gene in vitro and xenotransplanted into the brain of nude mice would permit the detection of brain tumor invasion and metastasis in vivo.

METHODS:

Daoy medulloblastoma cells were transfected with a long terminal repeat-based retroviral vector containing the EGFP gene. Stable EGFP-expressing clones were isolated and stereotactically injected into the frontal cortex of nude mice. Four weeks later, whole brain sections were examined using fluorescence microscopy, immunohistochemistry, and routine hematoxylin and eosin staining for the visualization and detection of tumor cell invasion and metastasis.

RESULTS:

We demonstrate that EGFP-transduced Daoy cells maintain stable high-level EGFP expression in the central nervous system during their growth in vivo. EGFP fluorescence clearly demarcated the primary tumor margins and readily allowed for the visualization of distant micrometastases and local invasion on the single-cell level. Small metastatic and locally invasive foci, including those immediately adjacent to the tumor's leading invasive edge, were virtually undetectable by routine hematoxylin and eosin staining and immunohistochemistry. EGFP expression also persisted in vitro after cell reculture from brain tissue extracts.

CONCLUSION:

We show, for the first time, that EGFP-transduced human brain tumor cells can be visualized by fluorescence microscopy after intracerebral implantation. This method is superior to routine hematoxylin and eosin staining and immunohistochemistry for the detection and study of physiologically relevant patterns of brain tumor invasion and metastasis in vivo.