Abstract
Advanced colorectal carcinoma is currently incurable, and new therapies are urgently needed. We report that phosphotyrosine‐dependent Eph receptor signaling sustains colorectal carcinoma cell survival, thereby uncovering a survival pathway active in colorectal carcinoma cells. We find that genetic and biochemical inhibition of Eph tyrosine kinase activity or depletion of the Eph ligand EphrinB2 reproducibly induces colorectal carcinoma cell death by autophagy. Spautin and 3‐methyladenine, inhibitors of early steps in the autophagic pathway, significantly reduce autophagy‐mediated cell death that follows inhibition of phosphotyrosine‐dependent Eph signaling in colorectal cancer cells. A small‐molecule inhibitor of the Eph kinase, NVP‐BHG712 or its regioisomer NVP‐Iso, reduces human colorectal cancer cell growth in vitro and tumor growth in mice. Colorectal cancers express the EphrinB ligand and its Eph receptors at significantly higher levels than numerous other cancer types, supporting Eph signaling inhibition as a potential new strategy for the broad treatment of colorectal carcinoma.
Highlights
Despite reduced incidence from screening, polypectomy, and other interventions, colorectal cancer remains a leading cause of cancer death (Welch and Robertson, 2016)
We examined the expression of EphrinB2 ligand and the EphrinB2 signaling receptors (EphB1, EphB2, EphB3, EphB4, and EphA4) (Kania and Klein, 2016; Noberini et al, 2012b) in colorectal carcinoma
Based on the RNA sequencing results from TCGA (The Cancer Genome Atlas) database, we determined that colorectal cancer tissues (n = 269) express significantly higher mRNA levels of EphrinB2, EphB1, EphB2, EphB3, and EphB4 than all other cancers surveyed (n = 3345; stomach n = 413; breast n = 901; lung adenocarcinoma n = 465; lung squamous cell carcinoma n = 407; hepatocellular carcinoma n = 132; ovarian n = 253; melanoma n = 82; uterine n = 365 and prostate n = 327), but lower levels of EphA4 (Fig. 1A)
Summary
Despite reduced incidence from screening, polypectomy, and other interventions, colorectal cancer remains a leading cause of cancer death (Welch and Robertson, 2016). Lineage-tracing experiments have shown that the leucine-rich repeat-containing G-protein-coupled receptor-5-positive (Lgr5+) intestinal stem cells, which normally reside at the bottom of the intestinal crypt, are the cells of origin of intestinal adenomas, the precursors of colorectal cancer (Barker et al, 2007; Schepers et al, 2012).
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