Contact-Inhibited ERK Signaling is Determined by Cellular-Resolution Western Blotting.

Extracellular signal-regulated kinase (ERK) signaling is essential to regulated cell behaviors, including cell proliferation, differentiation, and apoptosis. The influence of cell-cell contacts on ERK signaling is central to epithelial cells, yet few studies have sought to understand the same in cancer cells, particularly with single-cell resolution. To acquire both phenotypic (cell-contact state) and proteomic profile (ERK phosphorylation) on the same HeLa cells, we prepend high-content, whole-cell imaging prior to endpoint cellular-resolution western blot analyses for hundreds of cancer cells cultured on chip. By indexing the phosphorylation level of ERK in each cell or cell-contact cluster to the imaged cell-contact state, we compare ERK signaling between isolated and in-contact cells. We observe attenuated (∼2×) ERK signaling in HeLa cells which are in contact