Differential activity of Cremophor EL and paclitaxel in patients' tumor cells and human carcinoma cell lines in vitro.
BACKGROUND
Previous studies indicate that Cremophor EL (CEL), the excipient for Taxol, a clinical preparation of paclitaxel, has biologic properties per se.


METHODS
The cytotoxic activity of Taxol and its solvents CEL/ethanol, paclitaxel in ethanol, and 14 other cytotoxic drugs was investigated in vitro in 10 human carcinoma cell lines and 183 tumor samples from patients with tumors of various types. Cytotoxicity was determined by the fluorometric microculture cytotoxicity assay.


RESULTS
In the cell lines, Taxol was generally more active than paclitaxel; this may have been due to an additive effect of the diluent. This activity was pronounced in sublines expressing tubulin-associated and P-glycoprotein-mediated drug resistance, indicating involvement of these mechanisms in paclitaxel resistance and their modulation by CEL. Taxol and paclitaxel were highly cross-resistant to other tubulin-active agents, whereas the low cytotoxic effect of CEL seemed unrelated to other drugs. In the samples from patients, Taxol was less active than in the cell lines but showed a differential activity that corresponded reasonably well with that in the clinic. CEL and Taxol were similarly active, indicating that paclitaxel did not add substantially to the activity of Taxol.


CONCLUSIONS
Whereas the cell line data clearly confirmed the well-known properties of paclitaxel, a more valid model using tumor cells from patients demonstrated that CEL significantly contributes to the efficacy of Taxol in vitro. The clinical relevance of this finding remains to be elucidated.
Csóka
K
K
Division of Clinical Pharmacology, Uppsala University, Sweden.
Dhar
S
S
Fridborg
H
H
Larsson
R
R
Nygren
P
P
D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D005990:Glycerol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology*; D013501:Surface-Active Agents / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects*
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D013501:Surface-Active Agents; C000515:cremophor EL; D017239:Paclitaxel; D005990:Glycerol