Abstract

The aim of the present study was to investigate the effects of recombinant interleukin (rIL)-2 treatment on paclitaxel (PLX) pharmacokinetics in the plasma and tissue of Lewis lung carcinoma-bearing mice (lung tissues and s.c. tumors). PLX pharmacokinetics studies were conducted after oral and i.v. administration of 15 and 4 mg/kg, respectively, either alone or after 3 days of rIL-2 pretreatment. The noncompartmental approach was used to determine the mean pharmacokinetic parameters using WinNonlin software (Pharsight, Mountain View, CA). The influence of rIL-2 pretreatment on physiological P-glycoprotein (P-gp) expression in lung and intestine was investigated by Western blot analysis. After oral administration of PLX, areas under the curve (AUC) in plasma, lung, and s.c. tumors were significantly higher (2.98, 2.66, and 3.41-fold, respectively) in the rIL-2 + PLX group as compared with the PLX group. However, no significant effect of rIL-2 pretreatment was observed in plasma or lung following i.v. administration of PLX. PLX AUC in s.c. tumors was significantly higher (1.37-fold) with rIL-2 pretreatment as compared with the PLX-alone group after i.v. injection. Pretreatment with rIL-2 appeared to have no effect on PLX plasma terminal half-life when PLX was administered orally or i.v. However, prolongation of PLX terminal half-life estimated from lung and s.c. tumors data had been observed. Increased PLX tissue absorption in the rIL-2-pretreated group may be explained by a decrease of P-gp expression in the intestines and lung or decreased functionality due to rIL-2. Oral administration allowed the targeted tissues a much higher PLX exposure as compared with i.v. administration.