PIAS1 and breast carcinoma: Reference material comprised human breast cancer MDA-MB-231 cells where the abundance of endogenous PIAS1 was decreased by PIAS1 RNAi knockdown (samples 1 and 2), left unchanged (sample 3), or increased by overexpression (sample 4) to provide increasing cellular concentrations of PIAS1 (Fig 2A and 2B).