The cell growth and survival can be regulated by cytokine induced signals. Nevertheless, the molecular mechanisms of signal transduction from cytokine receptors to mediators of cell growth and apoptosis are not well characterized. STAT (signal transducer and activator of transcription) proteins can be activated by protein tyrosine kinases (PTK) in response to a variety of cytokines. We have shown that STAT activation induces expression of caspases which may cause cells undergo apoptosis. A hypothesis is proposed that PTKSTAT signaling pathways can regulate induction of apoptosis in response to cytokines and other extracellular signals.