Fig. 3.

The Hippo pathway mediates the reciprocal regulation of cell proliferation by contact inhibition and mitogenic signaling. Cell-cell contact inhibits cell proliferation through stimulation of the Hippo pathway. Mitogenic growth factors stimulate proliferation by well-known signaling mechanisms, but also counteract the growth inhibitory effects of the Hippo signaling pathway. Thus, the Hippo pathway can coordinate classic mitogenic signaling with the physical state of the cells in a tissue. TJ, tight junction; RTK, receptor tyrosine kinase; GPCR, G-protein-coupled receptor.