Figure 6. GnRH agonists do not sensitize p53-null PC3 cells to the antiproliferative/proapoptotic activity of docetaxel.

(A) Western blot analysis was performed to confirm the absence of p53 expression in PC3 cells. It is shown that p53 is expressed in DU145 cells while it is absent in PC3 cells. (B) Western blot analysis performed on whole cells extracts shows that treatment of PC3 cells with GnRH-A (10⁻⁶ mol/L, for 24–48 hours) does not affect the expression of either the proapoptotic (Bax) or the antiapoptotic (Bcl-2) protein. One representative of three different experiments is shown. (C) PC3 cells were pretreated with GnRH-A (10⁻⁶ mol/L) for 24 and then with docetaxel (10 nmol/L) for different time intervals (48–72 hours). Cells were then counted by hemocytometer. Pretreatment of the cells with GnRH-A does not potentiate the antiproliferative effect of docetaxel at all time intervals considered. (D) At the end of the treatments (as described in C), cell viability was measured by Trypan Blue exclusion assay. The number of dead cells was measured by counting Trypan Blue staining cells. Data are expressed as percent of stained cells/total cells. Docetaxel significantly increases the number of dead cells; pretreatment of the cells with GnRH-A does not potentiate the cytotoxic activity of docetaxel at any time interval considered. Each experimental group consisted of six replicates and each experiment was repeated three times. Data represent means ± SEM. *P<0.05 versus C (untreated controls).