Growth factor (GF) signal transduction is now a generally accepted target for antitumor therapy.Various drugs targeting both ligand-binding and tyrosine kinase domains of GF receptors were developed and are successfully used in the treatment of several cancer types.Nevertheless, even the most successful molecular-targeted agents, such as Herceptin(R), are effective only in a limited group of patients with corresponding receptor positive tumors, and a substantial part of them becomes resistant to the treatment in a relatively short time.Quite a convincing number of experimental studies have demonstrated that both primary and acquired resistance to these receptor-targeted drugs is imposed by a constitutive activation of downstream signaling cascades such as PI3K/Akt and NF-kappaB pathways..