(A) Basal level of DJ-1 mRNA in non-malignant HUVEC and A2780/CDDP, ES2 and IGROV1 ovarian cancer cells measured by quantitative PCR. The intracellular level of DJ-1 in HUVEC cells was used as a reference and set to 100%. Means ± SD are shown. *p < 0.05 when compared with HUVEC cells. Inset: Representative Western blot images of DJ-1 protein and β-Actin expression in HUVEC, A2780/CDDP, ES2 cells and IGROV1 cells. (B) Representative agarose gel electrophoresis image of free siRNA (lane 1), PPIG4 (lane 2) and siRNA incubated with PPIG4 at the following N/P (PPIG4 amine: siRNA phosphate groups) ratios: 0.5 (lane 3), 1 (lane 4), 2 (lane 5), 4 (lane 6), 8 (lane 7) and 10 (lane 8). An efficient binding of siRNA molecules with PPIG4 retards their gel electrophoretic mobility and prevents siRNA staining by ethidium bromide (lanes 4–8) in comparison to free siRNA (lane 1). (C) Viability of A2780/CDDP cells after incubation for 48 h with (1) non-modified PPIG4-siRNA complexes loaded with scrambled siRNA (1μM), (2) PPIG4-siRNA complexes modified with PEG only and (3) PPIG4-siRNA complexes modified with both PEG and LHRH peptide (siRNA-NP). Means ± SD are shown. *p < 0.05 when compared with cancer cells treated with non-modified PPIG4-siRNA complexes. (D) Size distribution profile of siRNA-NP evaluated by dynamic light scattering.