Person:

Bhere, Deepak

Developing therapeutics that target multiple receptor signaling pathways in tumors is critical as therapies targeting single specific biomarker/pathway have shown limited efficacy in patients with cancer. In this study, we extensively characterized a bi-functional molecule comprising of epidermal growth factor receptor (EGFR) targeted nanobody (ENb) and death receptor (DR) targeted ligand TRAIL (ENb-TRAIL). We show that ENb-TRAIL has therapeutic efficacy in tumor cells from different cancer types which do not respond to either EGFR antagonist or DR agonist monotherapies. Utilizing pharmacological inhibition, genetic loss of function and FRET studies, we show that ENb-TRAIL blocks EGFR signalling via the binding of ENb to EGFR which in turn induces DR5 clustering at the plasma membrane and thereby primes tumor cells to caspase-mediated apoptosis. In vivo, using a clinically relevant orthotopic resection model of primary glioblastoma and engineered stem cells (SC) expressing ENb-TRAIL, we show that the treatment with synthetic extracellular matrix (sECM) encapsulated SC-ENb-TRAIL alleviates tumor burden and significantly increases survival. This study is the first to report novel mechanistic insights into simultaneous targeting of receptor-mediated proliferation and cell death signaling pathways in different tumor types and presents a promising approach for translation into the clinical setting.

Summary Tumor-propagating cells (TPCs) share self-renewal properties with normal stem cells and drive continued tumor growth. However, mechanisms regulating TPC self-renewal are largely unknown, especially in embryonal rhabdomyosarcoma (ERMS)—a common pediatric cancer of muscle. Here, we used a zebrafish transgenic model of ERMS to identify a role for intracellular NOTCH1 (ICN1) in increasing TPCs by 23-fold. ICN1 expanded TPCs by enabling the de-differentiation of zebrafish ERMS cells into self-renewing myf5+ TPCs, breaking the rigid differentiation hierarchies reported in normal muscle. ICN1 also had conserved roles in regulating human ERMS self-renewal and growth. Mechanistically, ICN1 up-regulated expression of SNAIL1, a transcriptional repressor, to increase TPC number in human ERMS and to block muscle differentiation through suppressing MEF2C, a myogenic differentiation transcription factor. Our data implicate the NOTCH1/SNAI1/MEF2C signaling axis as a major determinant of TPC self-renewal and differentiation in ERMS, raising hope of therapeutically targeting this pathway in the future.