Phenylacetate inhibits protein isoprenylation and growth of the androgen-independent LNCaP prostate cancer cells transfected with the T24 Ha-ras oncogene

R Danesi, D Nardini, F Basolo, M Del Tacca, D Samid and CE Myers

Scuola Superiore di Studi Universitari e di Perfezionamento S. Anna, Universita di Pisa, Italy. mbxdanesi@mail.cnuce.cnr.it

The refractoriness of prostate cancer to androgen suppression is the landmark of clinically aggressive disease. In this study, the androgen- dependent LNCaP prostate cancer cells were transfected with the mutated c-Ha-ras gene from the T24 human bladder cancer. The derivative clone overexpressing T24-ras (LNCaP(T24-ras)) proliferated in androgen- depleted medium and showed increased growth. Protein isoprenylation and p21ras farnesylation in LNCaP(T24-ras) cells were tested in the presence of phenylacetate to document a possible relationship with the drug-induced inhibition of cell proliferation. Phenylacetate is a differentiation inducer that down-regulates in vitro the expression of the myc oncogene and activates the human peroxisome proliferator- activated nuclear receptor involved in cell growth regulation. The drug inhibited protein isoprenylation and p21ras farnesylation in LNCaP(T24- ras) cells; IC50 values were 3.1 and 3.3 mM, respectively, compared with controls. The drug reduced the cellular levels of endogenous farnesyl-PP (mean IC50 = 3.5 mM) and inhibited activation of the p21ras downstream target, p42(MAPK)/ERK2. LNCaP(T24-ras) was more sensitive than the parental line to both growth inhibition (mean IC50 = 3.01 and 7.1 mM, respectively) and apoptosis by phenylacetate. Exogenous farnesyl- and geranylgeranyl-PP indeed reduced the effects of the drug on proliferation and apoptosis in LNCaP(T24-ras) cells. In conclusion, the inhibition of protein isoprenylation and p21ras farnesylation by phenylacetate resulted in increased chemosensitivity of the androgen- independent LNCaP(T24-ras) cells compared with LNCaP, and this effect might contribute to the pharmacological activity of the drug.

Volume 49, Issue 6, pp. 972-979, 06/01/1996
Copyright © 1996 by American Society for Pharmacology and Experimental Therapeutics

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