Decoding the role of Netrin-1 receptor shedding during cancer cell survival
Biochemistry
Final Report Abstract
Once cancer cells spread from the primary tumor and metastasize to distant organs, patient survival rate decreases drastically. This multistage process whereby cancer cells escape from the primary tumor into distant tissues is strongly influenced by the tumor microenvironment (TME), which is composed of the extracellular matrix and noncancerous cells including stromal cells. Here, I discovered mesenchymal stromal cell (MSCs) that when educated with highly invasive breast cancer cell conditioned media, promote cancer cell invasion. RNAseq and LC-MS/MS identified the neuronal guidance molecule Netrin-1 (NET1) to be highly up-regulated in cancer cell educated MSCs and that elevation of NET1 is triggered by pro-inflammatory cytokines such as TNFa and IL-6. Based on the dependence receptor hypothesis, in which NET1 receptors induce apoptosis in the absence of their ligand, I initially hypothesized that cancer cells pursue a survival strategy by upregulating NET1 and eliminating NET1 receptors after ligand signaling and that inducing apoptosis in cancer cells by scavenging NET1 and blocking receptor shedding represents a promising treatment strategy. Indeed, I observed enhanced shedding of the NET1 receptor neogenin in cancer cells by Metalloproteases namely ADAM17. But unlike hypothesized in the literature, I could not find any evidence for a NET1-receptor induced cancer cell survival function and blocking NET1 receptor shedding did not induce apoptosis in cancer cells. Instead, I discovered that NET1 and its receptor neogenin are indispensable for TME- induced cancer cell invasion in breast cancer and melanoma. In fact, NET1 guides chemokines in particular CCL5 to their receptor CCR5 and co-receptor neogenin to form a pro-invasive super-complex. Thus, I hypothesize that I discovered a universal pro-invasive super-complex and signalling network triggered during inflammation, which might play a functional role not only in cancer but in viral infections, obesity, rheumatoid arthritis, and more. I am preparing two separate manuscripts for publication. The first manuscript represents a biochemical and structural study about the interaction of NET1, its receptors and Metalloproteases (ADAMs). For the first time, we show that a ligand, here NET1 facilitates shedding of its own receptor neogenin, which will be of particular interest to the protease community. Moreover, we can support our data with novel structural insights about the formation of a ternary complex formed by NET1, neogenin and ADAM10 and -17. The second manuscript will highlight the finding of a cytokine driven NET1-chemokine guidance system that promotes cell invasion. Here, I show for the first time that chemokines are guided by NET1 and that neogenin together with CCR5 serves as a novel chemokine co-receptor. I hypothesize that this novel identified pro-invasive super-complex plays an important role not only in cancer, but in many other inflammatory-driven diseases such as infectious diseases, obesity and rheumatoid arthritis. This study will draw new light on the role of the NET1 signalling axis and prove invaluable for the NET1 community.
