Next, treatment of p27−/−(Δ51) cells with calpain inhibitor (Calpain Inh), a competitive inhibitor of the Ca2+-dependent neutral cysteine protease, exhibited an remarkable positive effect on PHLPP2 protein accumulation (Fig. 2h), revealing that protease calpain might participate p27 regulation of PHLPP2 abundance in human BC cells. The gene discussed is CDKN1B; the disease is breast cancer.