We found that knocking down expression of PLK-1 using siRNA not only reduced the amount of PLK-1 protein (Fig. 2a, b), but also decreased the viability of both H295R and SW-13 to levels close to that of the positive control, UBB1, after siRNA knockdown (Fig. 2c), demonstrating that the ACC cell lines were very sensitive to the loss of PLK-1. Here, PLK1 is linked to adrenal cortex carcinoma.