Expression of a dominant negative mutant of mitogen-activated protein kinase kinase 4 (MKK4), a direct activator of JNK/SAPK, prevented T/P-induced JNK/SAPK activation.     ///    "In addition, inhibition of phosphoinositide-3 OH kinase (PI-3 kinase), a promoting survival factor, potentiated the effect of T/P on JNK/SAPK activation. "    ///    These findings indicate that activation of JNK/SAPK by T/P is related to apoptosis rather than cell proliferation and transformation..     ///    "Interestingly, expression of T/P was shown to initiate an apoptotic response that was enhanced by treatment of cells with the PI-3 kinase inhibitor LY294002, suggesting that T/P mediated cell death through activation of JNK/SAPK signalling pathway. "    ///    The oncogenic TEL/PDGFR beta fusion protein induces cell death through JNK/SAPK pathway..     ///    "This activation was abrogated when the T/P-expressing cells were treated with a specific inhibitor of the PDGFR beta tyrosine kinase, indicating that the activity of the PDGFR beta part of the fusion protein was involved in JNK/SAPK activation. "