Abstract
Apoptosis is intimately connected to cell cycle regulation via the Retinoblastoma (Rb)-E2F pathway and thereby serves an essential role in tumor suppression by eliminating aberrant hyperproliferative cells. Upon loss of Rb activity, an apoptotic response can be elicited through both p53-dependent and p53-independent mechanisms. While much of this apoptotic response has been attributed to the p19ARF/p53 pathway, increasing evidence has supported the role of protein tyrosine phosphatases (PTPs) in contributing to the initiation of the Rb-E2F-associated apoptotic response. One protein tyrosine phosphatase, PTP-1B, which is induced by the Rb-E2F pathway, has been shown to contribute to a p53-independent apoptotic pathway by inactivating focal adhesion kinase. This report identifies two additional PTPs, SHP-2 and PTP-PEST, that are also directly activated by the Rb-E2F pathway and which can contribute to signal transduction during p53-independent apoptosis.