Integration of multiple signaling pathway activities resolves K-RAS/N-RAS mutation paradox in colon epithelial cell response to inflammatory cytokine stimulation.

Colon tumors frequently harbor mutation in K-RAS and/or N-RAS, members of a GTPase family operating as a central hub for multiple key signaling pathways. While these proteins are strongly homologous, they exhibit diverse downstream effects on cell behavior. Utilizing an isogenic panel of human colon carcinoma cells bearing oncogenic mutations in K-RAS and/or N-RAS, we observed that K-RAS and double mutants similarly yield elevated apoptosis in response to treatment with TNFalpha compared to N-RAS mutants. Regardless, and in surprising contrast, key phospho-protein signals were more similar between N-RAS and dual mutants. This apparent contradiction could not be explained by any of the key signals individually, but a multi-pathway model constructed from the single-mutant cell line data was able to predict the behavior of the dual-mutant cell line. This success arises from a quantitative integration of multiple pro-apoptotic (pIkappaBalpha, pERK2) and pro-survival (pJNK, pHSP27) signals in manner not easily discerned from intuitive inspection.