Newer
photosensitizers continue to be sought for
photodynamic therapy of
bladder cancer particularly since local rather than systemic application is desired. Recent studies have indicated that a cationic
dye,
PH1008, a 13,17-N,N,N-dimethylethylethanolamine
ester of
protoporphyrin, sensitizes the photolysis of red blood cells. The study described in this report was designed to investigate the plasma membrane partitioning of
PH1008 model
lipid system and to compare partitioning of
PH1008 in normal transitional cells and
bladder cancer cells in vitro. Partition coefficient (Kp) values characterizing the distribution of
PH1008 between aqueous
buffer and normal and malignant transitional cells were 3.4 +/- 0.7 x 10(4) (CRL-7881) and 9.5 +/- 1.4 x 10(4) (HTB-9), resulting in a 20% difference in membrane
photosensitizer concentration at a particular
photosensitizer concentration. Significantly higher (2-5 fold) differences are observed between
tumor and surrounding normal tissue for systemically delivered
photofrin II. Cell-bound
drug was 30-fold (CRL-7881) and 80-fold (HTB-9) more fluorescent when compared to aqueous
buffer. The combined effects of partitioning and bound fluorescence suggest that a 3.2-fold increase in fluorescence of transformed vs. normal bladder urothelium exists. This difference in fluorescence suggests that
PH1008 might be more useful as a diagnostic tool than as a phototherapeutic agent.