Anchorage-Independent Growth of Pocket Protein-Deficient Murine Fibroblasts Requires Bypass of G₂ Arrest and Can Be Accomplished by Expression of TBX2

Mouse embryonic fibroblasts (MEFs) deficient for pocket proteins (i.e., pRB/p107-, pRB/p130-, or pRB/p107/p130-deficient MEFs) have lost proper G1 control and are refractory to RasV12-induced senescence. However, pocket protein-deficient MEFs expressing RasV12 were unable to exhibit anchorage-independent growth or to form tumors in nude mice. We show that depending on the level of pocket proteins, loss of adhesion induces G1 and G2 arrest, which...