Epidermal Growth Factor Receptor (EGFR) is a cell surface protein with tyrosine kinase activity, and a major effector of extracellular signals promoting cell growth and survival, as well as tissue differentiation and homeostasis. EGFR is also considered a proto-oncogene, since its aberrant/constitutive activation is responsible for cancer cell growth and invasive properties; furthermore, its upregulation leads to resistance to targeted therapies in human solid tumors.

Due to its major impact in cell functions, EGFR is subject to several regulatory mechanisms, at transcriptional, post-transcriptional, and post-translational levels. Moreover, a range of EGFR-interacting proteins controls its activation, trafficking and intracellular signaling. In particular, EGFR cross-talks with other plasma membrane receptors. For instance, we have recently demonstrated that the release of inflammatory cytokines can trigger a feed-back intracellular cascade sustaining the EGFR pathway. Moreover, we found that cell surface co-receptors, the Neuropilins, play a major role in EGFR regulation, with potential relevance for cancer therapy. Neuropilins are mainly known as co-receptors for extracellular signals, such as VEGF and Semaphorins. Intriguingly, Neuropilin-1 (NRP1) has also been found to mediate the internalization of micro-RNAs found in the extracellular space (and circulating plasma); once in the cytosol, these miRNAs are enabled to inactivate specific gene transcripts.

This novel function could represent an important mechanism of EGFR regulation, since multiple players of this signaling pathway are targeted by miRNAs. Prompted by these preliminary data, in this project we aim at elucidating novel mechanisms regulating EGFR signaling, via the cross-talk with other membrane receptor pathways, such as inflammatory cytokines, or the Neuropilins and their extracellular ligands, including circulating miRNAs.

Our experimental models will employ normal and tumor cells dependent on the EGFR pathway. We will study 3D models growing in suspension, such as spheroids of epithelial cells and patient-derived tumor organoids, available to the labs. Based on supportive evidence at cellular level, the relevance of the investigated mechanisms will be further validated in mouse models. In particular, we postulate a specific role of Interleukin1-Receptor (IL1R) signaling to enhance the EGFR pathway. Moreover, we implicate NRP1/NRP2 and their ligands in the regulation of EGFR expression in different cell types, and for rescuing cancer cell viability in response to oncogene-targeted therapies. Notably, secreted miRNAs circulating in body fluids may be captured and internalized by cell surface receptors, such as NRP1, and we will study whether such mechanism can effectively regulate mRNA transcripts encoding EGFR or other components of this pathway.

Investigating the crosstalk between EGFR and other membrane receptors is expected to unveil novel regulatory mechanisms controlling tissue development and homeostasis, as well as to advance our understanding of signaling escape mechanisms jeopardizing the efficacy of cancer therapy. In translational perspective, we will assay the therapeutic combination of EGFR-blockade and IL1R inhibitors. Moreover, since NRP1 and NRP2 cell surface receptors have been found to regulate EGFR expression and signaling, their combined targeting with inhibitors and extracellular ligands could improve the efficacy of EGFR inhibitors in cancer treatment and prevent the onset of drug-resistance, as recently validated in our preliminary studies.

Finally, interfering with the activity of circulating miRNAs that impact on the EGFR signaling pathway could represent a powerful approach for designing innovative tools for cancer therapy. Our project may also lead to the identification of EGFR-regulating miRNAs found in plasma that could represent diagnostic/prognostic markers for cancer patients. In sum, we aim at the characterization of novel mechanisms controlling the EGFR pathway, via the cross-talk with other membrane receptors and their extracellular ligands. We anticipate that this new knowledge could be exploited for tackling issues relevant for personalized medicine.

Partners:

• Università Cattolica del Sacro Cuore - Italy (Coordinator)
• Università degli Studi di Bologna - Italy
• Università degli Studi di Roma "La Sapienza" - Italy