(A) Detection of CDK4 and cyclin D1 by immunoblotting. Lane 1, BFCE primary cells; Lanes 2 and 3, BFCE-K4DT cells. (B) Detection of telomerase activity by TRAP assay. Lane 1, 1 kb ladder marker; lane 2, CHAPS buffer as a negative control; lane 3, 293T cells as a positive control; lane 4, BFCE primary cells; lane 5 and 6, BFCE-K4DT cells. The 6-bp ladders were detectable in lanes of positive control and BFCE-K4DT cells. Each experiment was performed in duplicates after cloning (primary cells: 2 times passage, K4DT cells: 15 times passage) and representative data were shown here.