K562 cells.

(A) Growth curves for p16^INK4a-transduced (K/p16), empty vector–transduced (K/pBN), and untransduced K562 cells. The p16^INK4a-transduced and empty vector–transduced cells, but not the parental cells, were cultured in the presence of G418. The results are from the 1 experiment (out of 4) in which the p16^INK4a-transduced cells showed any significant growth. (B) Western blot analysis of untransduced K562 cells (lane 1), K562 cells transduced with p16 (lane 2), and cells transduced with empty vector (lane 3) after 16 passages. The results show expression of p16^INK4a by the p16^INK4a-transduced cells. Expression of p16^INK4a (lane 2) results in loss of the hyperphosphorylated forms of pRB and p107 and in reductions in the expression levels of p107, p130, and E2F-1.