Therapeutic application of extracellular vesicular EGFR isoform D as a co-drug to target squamous cell cancers with tyrosine kinase inhibitors.

Targeting wild-type epidermal growth factor receptor (EGFR) using tyrosine kinase inhibitors (TKIs) never achieved its purported success in cancers such as head and neck squamous cell carcinoma, which are largely EGFR-dependent. We had previously shown that exceptional responders to TKIs have a genetic aberration that results in overexpression of an EGFR splice variant, isoform D (IsoD). IsoD lacks an integral transmembrane and kinase domain and is secreted in extracellular vesicles (EVs) in TKI-sensitive patient-derived cultures. Remarkably, the exquisite sensitivity to TKIs could be transferred to TKI-resistant tumor cells, and IsoD protein in the EV is necessary and sufficient to transfer the phenotype in vitro and in vivo across multiple models and drugs. This drug response requires an intact endocytic mechanism, binding to full-length EGFR, and signaling through Src-phosphorylation within the endosomal compartment. We propose a therapeutic strategy using EVs containing EGFR IsoD as a co-drug to expand the use of TKI therapy to EGFR-driven cancers.
Competing Interests: Declaration of interests N.G.I. has/had a consulting or advisory role in PairX Therapeutics, Verimmune therapeutics, and Invivo surgical; received honoraria from Agilent, and research funding from Merck, all of which are outside this submitted work. D.S.W.T. received honoraria from Bristol-Myers Squibb, Takeda Pharmaceuticals, Novartis, Roche, and Pfizer; has consulting or advisory role in Novartis, Merck, Loxo Oncology, AstraZeneca, Roche, and Pfizer and received research funding from Novartis (Inst), GlaxoSmithKline (Inst), and AstraZeneca (Inst), outside this submitted work. N.G.I., D.S.W.T., S.Y.T., H.S.L., F.T.C., and D.M.R.-J. are listed as co-inventors on the patent application entitled “Method of Modulating Sensitivity To Tyrosine Kinase Inhibitor” (International Publication: WO2022045976A1), which describes a significant proportion of the data here.
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