Loss of the Polarity Protein Par3 Activates Stat3 Signaling via an aPKC/NF-{kappa}B/IL-6 Axis in Mouse Mammary Cells [Signal Transduction]

February 5th, 2015 by Guyer, R. A., Macara, I. G.

Par3 suppresses tumor growth and metastasis in vivo and cell invasion through matrix in vitro. We propose that Par3 organizes and limits multiple signaling pathways, and that inappropriate activation of these pathways occurs without Par3. Silencing Par3 in conjunction with oncogenic activation promotes invasion and metastasis via constitutive Stat3 activity in mouse models, but the mechanism for this is unknown. We now show that loss of Par3 triggers increased production of Interleukin-6, which induces Stat3 signaling in an autocrine manner. Activation of aPKCι/λ mediates this effect by stimulating NF-κB signaling and IL-6 expression. Our results suggest that Par3 restrains aPKCι/λ activity and thus prevents aPKCι/λ from activating an oncogenic signaling network.