Compared with cotransfection with the control miVP2con vector, co-transfection with three out of four anti-cHsp90alpha and two out of three anti-cHsp90beta miRNA vectors resulted in a significant decrease in the number of EGFP-positive cells. According to their higher gene-silencing effects on cHsp90 transcription, two anti-cHsp90alpha miRNAs (micHsh90alpha1 and micHsh90alpha3) and one anti-cHsp90beta miRNA (micHsp90beta9) were selected for a stable transfection study.