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Mol Cancer Ther. 2003 Mar;2(3):245-54.

Interleukin-4 receptor-targeted cytotoxin therapy of androgen-dependent and -independent prostate carcinoma in xenograft models.

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Laboratory of Molecular Tumor Biology, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.


Prostate cancer is the most commonly diagnosed solid tumors in United States men. Survival with advanced prostate cancer is dismal because of a lack of effective treatments. Overexpression of interleukin 4 receptors (IL-4R) on prostate carcinoma cells makes them suitable targets for the interleukin 4 (IL-4) fused Pseudomonas exotoxin, IL-4 cytotoxin (IL4-CTx). Androgen-dependent (LNCaP) and -independent (DU145) human prostate cancer cell lines overexpress IL-4Rs and are exquisitely sensitive to IL4-CTx. Using LNCaP and DU145 cell lines, IC(50) values of 4.5 +/- 2.0 and 6.5 +/- 0.5 ng/ml, respectively, were obtained for IL4-CTx in protein synthesis inhibition assays. Primary cultures established from prostate tumor biopsies were equally sensitive to the cytotoxic effects of IL4-CTx. Reverse transcription-PCR analysis, although not quantitative, indicated the presence of mRNA for IL-4Ralpha, a primary subunit of the IL-4R receptor complex in prostate carcinoma cell lines, primary cultures, benign prostatic hyperplasia, and prostate carcinoma tissues. Immunohistochemistry studies revealed the presence of IL-4R in benign prostatic hyperplasia and prostate carcinomas. Five daily (QD) injections of IL4-CTx (100 micro g/kg) administered i.v., i.p., or intratumoral (i.t.) caused several complete responses in nude mice with s.c. DU145 and LNCaP tumors. i.t. injections of IL4-CTx elicited tumor regression in a dose-dependent manner with complete responses occurring in 100% of the animals when treated with IL4-CTx (500 micro g/kg) given five QD injections. Administration of IL4-CTx i.t. (500 micro g/kg) either 10 times QD or six injections on alternate days elicited complete responses in 40% of mice with DU145 tumors that were three times larger (67 mm(2)) on initiation of treatments. IL4-CTx appeared to be well tolerated. On the basis of these results, combining i.t. injections of IL4-CTx with systemic administration may provide an effective strategy for treating patients with advanced, refractory prostate cancer.

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