Downregulation of Id1 by small interfering RNA in prostate cancer PC3 cells in vivo and in vitro.

Overexpression of helix-loop-helix protein-Id1 in prostate cancer correlates with tumor differentiation, and may play a key role in the development of prostate cancer. Hence, we inactivated the Id1 gene in prostate cancer cells in vitro and in vivo to determine whether the Id1 gene has therapeutic potential in the treatment of prostate cancer. A modified small interfering RNA (siRNA) was used to inactivate the Id1 gene in androgen-independent prostate cancer cell line PC3 and its xenografts in nude mice.