RB1 and lung cancer: Next, to test whether the negative regulation of stathmin by RB1 occurs in general, not in a cell context-dependent, we analyzed the protein levels of RB1 and stathmin in a panel of lung cancer cell lines, including wildtype RB1 expressing cells (A549, HCC827, H1975, and H1650) and RB1-null cells (H446 and H82).