pRb turnover in melanoma cells and normal melanocytes. pRb turnover in melanoma cells and normal melanocytes. Cultures of melanoma cells (501 mel, in A–C) and normal melanocytes (normal, C) were incubated with radioactive medium (35S) for 3 h and were harvested immediately (lanes marked 0) or after a chase with regular medium for the duration of 1, 2, 4, 6, 10, or 18 h, as indicated above each lane. AG1024 (1 μm) and protease inhibitors (MG-132, leupeptin, and pepstatin) were added (+) during the last 1 h of incubation. Radioactive cell extracts were subjected to immunoprecipitation (IP) with anti-pRb (IF8) or control matched mAb (C), and captured proteins were visualized by autoradiography. Maria von Willebrand et al. Cancer Res 2003;63:1420-1429 ©2003 by American Association for Cancer Research