KIF5B-RET Oncoprotein Signals through a Multi-kinase Signaling Hub

Gene fusions are increasingly recognized as important cancer drivers. The KIF5B-RET gene has been identified as a primary driver in a subset of lung adenocarcinomas. Targeting human KIF5B-RET to epithelia in Drosophila directed multiple aspects of transformation, including hyperproliferation, epithelial-to-mesenchymal transition, invasion, and extension of striking invadopodia-like processes. The KIF5B-RET-transformed human bronchial cell line showed similar aspects of transformation, including invadopodia-like processes. Through a combination of genetic and biochemical studies, we demonstrate that the kinesin and kinase domains of KIF5B-RET act together to establish an emergent microtubule and RAB-vesicle-dependent RET-SRC-EGFR-FGFR signaling hub. We demonstrate that drugs designed to inhibit RET alone work poorly in KIF5B-RET-transformed cells. However, combining the RET inhibitor sorafenib with drugs that target EGFR, microtubules, or FGFR led to strong efficacy in both Drosophila and human cell line KIF5B-RET models. This work demonstrates the utility of exploring the full biology of fusions to identify rational therapeutic strategies.