Regulation of cyclin D3 and CDK4 expression by Notch1 in T-cell lymphomas. (A) Protein extract from spleens of 2 wild-type FVB mice (WT) and 3 Top-Notch leukemic (tTA-N^ic) mice were used to analyze the expression of cyclin D3, CDK4, and Notch-1. GAPDH was used as a loading control. (B) Protein extracts from spleens of 2 wild-type FVB mice (WT) and 2 MIG-N^ic leukemic mice were used to determine cyclin D3, CDK4, and Notch-1 expression, as indicated. GAPDH was used as a loading control. (C) E μ-tTA/TOP-Notch mice were generated as previously described.^36,37  Samples prepared for regression analysis were prepared as described in Table S1. Left panel shows the RT-PCR performed on primary tumor samples and on transplanted samples from mice undergoing doxycycline regression for different lengths of time (0, 3, and 24 hours). Notch transcripts were analyzed, and β-actin was used as a positive control. Right panel shows Western blot analysis performed using total cell lysate for detection of cyclin D3 and CDK4 from primary tumor samples and transplanted samples from mice undergoing doxycycline regression for various lengths of time (0 and 24 hours).