IL-17R deletion predicts high-grade colorectal cancer and poor clinical outcomes

The IL-17 receptor (IL-17R) has a perplexing role in cancer, which may be explained by its yin-yang signaling pathways. Recently, the critical role of IL-17R in maintaining basal levels of A20—a key negative regulator of NF-κB and JNK-c-Jun pathways has been demonstrated in cancer cell lines. Cross-cancer analyses of somatic copy number alterations in IL-17RA, IL-17RC and A20 genes reveal that IL-17RA-deletion is common in colorectal cancer (CRC) patients, representing 24, 26, 37 and 49% of stage I, II, III and IV of patients, respectively, and mutually exclusive with patients displaying microsatellite instability. Importantly, patients with IL-17R-deletion or concurrent deletions of A20 show significantly reduced overall survival. Analysis of multiple published microarray studies confirms that IL-17RA expression is significantly reduced in CRC samples compared to normal counterparts, and its level is closely associated with A20 expression. Analyses of RNAseq data indicate that tumors with IL-17R-deletion express strong molecular markers of tumor invasion, growth and metastasis. Notably, approximately 20 genes responsible for protein synthesis and mitochondrial metabolism are inversely correlated with both IL-17RA and A20. Immunohistochemistry staining in human colorectal tissue arrays further reveals that high-grade tumors have significantly reduced IL-17RA staining compared to low-grade tumors. Thus, collective evidence strongly supports a previously unrecognized CRC-promoting mechanism triggered by IL-17RA-deletion and highlights its utility as a prognostic marker in CRC.