As shown in Fig. 4g, degradation rates of Hsp90 and PHLPP2 was much faster in p27+/+ (Flag-calpain 1) (half-life: 4.3 and 2.4 h) in comparison to p27+/+ (Vector) cells (half-life: 10.0 and 5.4 h), revealing that calpain 1 is critical for promoting Hsp90 degradation and subsequent reducing PHLPP2 protein stability in human BC cells. This evidence concerns the gene CDKN1B and breast cancer.