Androgen-independent growth of LNCaP prostate cancer cells is mediated by gain-of-function mutant p53.

Mutations of p53 are common in hormone-refractory prostate cancer (CaP), suggesting the possibility that these mutations may be involved in the progression of CaP to androgen-independent (AI) growth. However, at present no direct evidence has been presented linking p53 mutations with AI growth of CaP. We established five stably transfected LNCaP cell lines: four containing gain-of-function (GOF) mutant p53 alleles (G245S, R248W, R273H, and R273C) and one containing a non-GOF p53 mutant allele (P151S). The four GOF p53 sublines were able to grow under androgen-depleted conditions, whereas the LNCaP parental line, vector-only line, and the non-GOF line were unable to grow. To investigate the mechanism of the AI growth displayed by the GOF p53 mutants, Western blotting or ELISA were used to examine the expression of the androgen receptor (AR), the AR-regulated prostate-specific antigen (PSA), as well as Akt and Bcl-2 under androgen-depleted conditions. On androgen ablation, the levels of AR decreased in the four GOF p53 sublines compared with the control lines. This decreased AR expression was accompanied by attenuated receptor activity, because a decrease in prostate-specific antigen levels compared with parental LNCaP cells was also observed. Levels of phosphorylated Akt increased in both the GOF p53 sublines and the control lines. Bcl-2 remains unchanged or showed reduced expression in all of the cell lines in the absence of androgen compared to the presence of androgen. These observations suggest that GOF p53 mutants mediate the AI growth of LNCaP cells in an AR-independent fashion, and that both Akt and Bcl-2 are not involved in this process.