Perturbation of the TRF gene expression by two different siRNA species. Each of the three TRF genes was individually knocked down in HepG2 cells by either of the two different siRNAs specific to each of them, and changes in expression levels of 21 TRF genes were measured by qRT-PCR. The average ΔΔC _T , SD and P values were obtained from triplicated experiments. Correlation coefficients were calculated on the basis of average ΔΔC _T values.