Photodynamic therapy is a promising treatment for human brain tumors because of 
the selective retention of certain compounds by tumor cells. Certain lipophilic 
cationic compounds, such as tetraphenylphosphonium (TPP), are selectively taken 
up by a variety of carcinomas. Although preferential retention of TPP has been 
demonstrated for the breast carcinoma cell line MCF-7, this compound had not 
been tested previously on cells derived from nervous system tumors. In the 
present study, tritiated-TPP (3H-TPP) uptake and retention for eight different 
cell cultures of three histologically different types of nervous system tumors 
was measured and the data were compared to a positive control (MCF-7) and 
negative controls (normal African Green monkey kidney epithelium (CV-1) and the 
normal human fibroblast (WI-38) cell lines). Uptake and retention 
characteristics could be grouped by specific pathological tumor types, but 
individual tumor variability was notable. Malignant astrocytoma (grade III/III 
glioblastoma) and malignant neurofibrosarcoma cells showed preferential uptake 
and retention of 3H-TPP relative to meningioma cells and normal controls. A 
clonogenic assay utilizing the cytotoxic lipophilic cationic compound 
dequalinium showed strong retainers of 3H-TPP to be more susceptible to the 
effects of dequalinium than weak retainers. These data demonstrate that certain 
human and experimental animal nervous system tumor cell lines retain lipophilic 
compounds possessing a delocalized positive charge. Lipophilic cationic 
compounds may be useful in the intraoperative delineation of tumor margins and 
in the photodynamic therapy of certain nervous system tumors.