IL-7 mediates up-regulation of cyclins and activates cyclin-dependent kinases due to down-regulation of cyclin dependent kinase inhibitor p27^kip1 in T-ALL cells.

(A,B) T-ALL cells were cultured with IL-7 for the indicated time intervals, lysates were analyzed by SDS-PAGE and immunoblotted with an antibody specific for cyclin D2. Blots were stripped and reprobed sequentially with antibodies specific for cyclin A, cdk6, cdk4, and cdk2. Representative results from 1 among 4 patients studied are shown. (C) From the same samples immunoprecipitations were performed with anti-cdk2–specific antiserum agarose conjugate and in vitro kinase reactions were done by using Histone H1 as exogenous substrate. Reactions were analyzed by 10% SDS-PAGE, transferred to PVDF membrane and exposed to x-ray film. (D) Lysates from the same samples were analyzed by 6% SDS-PAGE, transferred on nitrocellulose membrane, and immunoblotted with mAb specific for Rb. (E,F) Samples from 2 individual patients were cultured for various time intervals in the presence of IL-7 and examined for the expression of p16^INK4, p21^cip1, and p27^kip1 by immunoblot. Representative results from 2 among 6 patients studied are shown.