The epidermal growth factor receptor (EGFR) deregulations play a central role in cancer progression. EGFR generates extra- and intracellular signals through various pathways, including its release in the tumor microenvironment through extracellular vesicles, as well as the nuclear EGFR signaling. That ultimately results in oncogenic signals promoting the tumor aggressiveness. Our previous report showed that sortilin, a member of the VPS10P sorting proteins, is associated with EGFR to allow its secretion through exosomes in non-small cell lung cancer (NSCLC) cells. Furthermore, sortilin is mainly present in the Golgi which is an essential compartment involved in the EGFR bypass towards the nucleus. Therefore, our aim is to investigate the potential role of sortilin in EGFR nuclear translocation.
EGFR and sortilin translocation into the nucleus has been validated by proximity ligation assay and confocal microscopy analysis. Moreover, to study the sortilin function in the EGFR nuclear translocation, we resorted to the NSCLC cell line A549 in which the sortilin expression was silenced using a shRNA delivery. Subcellular fractionations and nuclear protein extractions were performed to study the impact of the sortilin loss on the EGF-induced EGFR nuclear translocation.
EGF stimulation highly increases the nuclear translocation of the EGFR and sortilin complex. Interestingly, sortilin depletion significantly decreases the EGF-induced EGFR nuclear translocation in the A549 cells. Strikingly, sortilin-depleted cells exhibit an overexpression of EGFR target genes (MYC, ABCG2, AURKA and CCND1) compared to the control cells. These results suggest that the overexpression of the EGFR target genes is independent of EGFR nuclear translocation in sortilin-depleted cells. Thus, we analyze the activation of the known transcription factors directly involved in the control of EGFR up-regulated genes to determine whether they are activated in sortilin-depleted cells. Moreover, to better understand the sortilin-dependent EGFR nuclear translocation, we compare functional properties (proliferation,
migration and angiogenesis assays) of sortilin-depleted and control cells.
Altogether, our findings suggest a key role of sortilin in the regulation of the EGFR nuclear transport, towards the control of target genes that are widely involved in cancer progression.
Citation Format: Hussein Al Akhrass, Thomas Naves, Marie-Odile Jauberteau, François Vincent, Fabrice Lalloué. Sortilin controls the EGFR nuclear translocation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3327. doi:10.1158/1538-7445.AM2017-3327