The Chance of Small Interfering RNAs as Eligible Candidates for a Personalized Treatment of Prostate Cancer

Background: Prostate cancer is one of the leading malignant tumors in men. Current therapies are associated with severe side effects making it problematic for many multi-morbid patients to receive treatment. Prostate specific antigen, serum response factor (SRF), signal transducer and activator of transcription-3 (STAT3), hypoxia-inducible factor-1α (HIF-1α), HIF-2α, E2F1 and Survivin are well known proteins being overexpressed in cancer cells, expediting cell growth and also demonstrated in prostate cancer cells. Targeting these genes using the RNA-Interference pathway could be a new approach for prostate cancer therapy with fewer side effects. Methods: Three prostate cancer cell lines were cultured under standard conditions and transfected with three different concentrations (25 nM, 50 nM, 100 nM) of specific small interfering RNAs (siRNAs) targeting SRF, STAT3, HIF1α, HIF2α, E2F1 and Survivin in a non-viral manner. Cells treated with non-specific siRNA (SCR-siRNA) served as control. Changes of messenger RNA (mRNA) levels were determined using quantitative real-time polymerase chain reaction (qRT-PCR). The analysis of the effect of siRNA on the number of cells was detected using CASY cell counter system. Results: Transfections of the PC-3 cell line with specific siRNA especially against Survivin, E2F1, HIF1α- and HIF2α-siRNA resulted in a significant reduction of intracellular mRNA concentration together with a significant decreased number of cells. In the LnCAP and DU-145 cell lines Survivin and E2F1 showed similar effects. The impact of silencing STAT3 or SRF showed little influence on the amount of cells in all three cell lines. Conclusions: This study shows that RNAi succeeds in silencing gene expression and reducing the number of cells in differing dimensions depending on the transfected cell line and used siRNA. Keywords: E2F1, hypoxia-induced factors, RNA-interference, serum response factor, survivin, STAT3.