Exploring the Role and Targeting of Nuclear EGFR in Triple-Negative Breast Cancer

Among breast cancer subtypes, triple-negative breast cancers overexpressing epidermal growth factor receptor (EGFR) have some of the most aggressive phenotypes and poorest prognoses. EGFR contributes to oncogenic signaling and in triple-negative breast cancer (TNBC) has been observed to traffic to the nucleus where it acts as a co-regulator of transcription among other activities. Targeting of EGFR via inhibition of its receptor tyrosine kinase activity or antibody therapies have proven ineffective in treating triple-negative breast cancers. An alternative method to target EGFR is by inhibiting its retrograde trafficking. Sorting nexin 1 (SNX1) binds to EGFR at the early endosome and is implicated in retrograde trafficking given its membrane bending functions and its homologue in yeast’s role in the retromer complex. Our lab has developed a peptide that inhibits this interaction called cSNX1.3. Treatment with cSNX1.3 results in a regression of EGFR-driven tumors in mice and a loss of viability in TNBC cells. However, it also causes an induction of interleukin 6 (IL-6) and causes changes in the expression of keratin 14. I have performed chromatin immunoprecipitations to determine if EGFR is binding to the promoters of keratin 14 and IL-6 in response to ligand activation, and if this is inhibited following cSNX1.3 treatment. Signal transducer and activator of transcription 3 and 5 (STAT3 and STAT5) binding were also evaluated, given that they are known to bind to EGFR and allow for its regulation of gene expression. These experiments have revealed an alternative pattern of STAT5 and EGFR binding. They also reveal that cSNX1.3 may act independently of ligand-activation of EGFR to regulate gene expression. Ultimately, however these findings confirmed that EGFR is binding to the promoters of keratin 14 and IL-6 following ligand-activation and retrograde trafficking to the nucleus. cSNX1.3 is able to decrease this binding substantially. Given that nuclear EGFR is related to poor prognoses, this reduction of nuclear EGFR activity following cSNX1.3 treatment points to targeting nuclear EGFR localization via inhibition of the SNX1-EGFR interaction as a novel and promising potential therapeutic considering its in vivo and in vitro effects.Release after 05/18/202