Functional Genomics Approach Identifies Novel Signaling Regulators of TGF alpha Ectodomain Shedding

摘要

Ectodomain shedding of cell-surface precursor proteins by metalloproteases generates important cellular signalingmolecules. Of importance for disease is the release of ligands that activate the EGFR, such as TGF alpha, which is mostly carried out by ADAM17 [a member of the A-disintegrin and metalloprotease (ADAM) domain family]. EGFR ligand shedding has been linked to many diseases, in particular cancer development, growth and metastasis, as well as resistance to cancer therapeutics. Excessive EGFR ligand release can outcompete therapeutic EGFR inhibition or the inhibition of other growth factor pathways by providing bypass signaling via EGFR activation. Drugging metalloproteases directly have failed clinically because it indiscriminately affected shedding of numerous substrates. It is therefore essential to identify regulators for EGFR ligand cleavage. Here, integration of a functional shRNA genomic screen, computational network analysis, and dedicated validation tests succeeded in identifying several key signaling pathways as novel regulators of TGFa shedding in cancer cells. Most notably, a cluster of genes with NFkB pathway regulatory functions was found to strongly influence TGF alpha release, albeit independent of their NFkB regulatory functions. Inflammatory regulators thus also govern cancer cell growth-promoting ectodomain cleavage, lending mechanistic understanding to the well-known connection between inflammation and cancer. (C) 2017 AACR.