CDKN1B and acute lymphoblastic leukemia: Western blot analysis with anti-SIRT1 (D1D7) rabbit monoclonal antibody (CST, #9475) and anti-SIRT1 (07–131) rabbit polyclonal antibody (Sigma-Aldrich, #07–131) revealed that SIRT1 KO T-ALL cells expressed the expected SIRT1 mutant protein with the in-frame deletion of exon 4 and that SIRT1 deficiency upregulated p27 protein expression but had little effect on p27 mRNA levels (Fig. 5e-f).