Western blot analysis of Ki-67 in equal amounts of cell lysates. Samples were incubated in Ki-67 monoclonal antibody (Product # MA5-47446) using a dilution of 1:10,000 (green). [1] protein standard (red), [2] rapidly growing HeLa cell cultures, [3] rapidly growing HEK293 cell cultures. Strong double bands larger than the 250 kDa standard correspond to full length 345 kDa and 395 kDa Ki67 isoforms, while smaller proteolytic fragments of these isoforms are also invariably detected on the blot.