The JAK/STAT pathway begins with the activation of a membrane bound cytokine receptor by interferon or another cytokine. The activated receptor recruits and activates intracellular tyrosine kinases of the JAK family. Active JAKs phosphorylate STAT proteins, which then dimerize, enter the nucleus and activate gene transcription. Genes activated by the JAK/STAT pathway include genes that activate proliferation, such as MYC and CCND2, which encodes Cyclin D2. The JAK/STAT pathway is overactivated in many cancers by various mechanisms such as overexpression of the genes that code for the cytokine receptors. In addition, the JAK/STAT pathway can be activated by proto-oncoproteins of other pathways, e.g. by the EGF receptor.