Expression of the alternatively spliced soluble RAGE variant suppresses metastatic pathways and tumor development

The Receptor for Advanced Glycation End‐products (RAGE) has been implicated in cancer pathogenesis in studies from human subjects and from the reduction of tumor growth and metastases from the administration of soluble RAGE (sRAGE) in mice. The endogenous generation of human sRAGE occurs by alternative splicing, primarily from inclusion of intron 9 of the RAGE gene (RAGEint9), altering the reading frame and deleting the transmembrane and cytoplasmic domains. We tested the hypothesis RAGEint9 modulates tumor properties by generating cancer cells stably expressing RAGEint9. RAGEint9 transfection suppressed RAGE‐ligand stimulated MAP kinase signaling, as phosphorylation of p44/42 and p38 was reduced ≈3‐fold compared to vector‐control cells (p<0.0001). Nuclear activation of NF‐kB, assessed by gel shift assays, was reduced ≈4‐fold in RAGEint9 vs. control cells (p<0.0001). We examined the impact of RAGEint9 on the expression and activity of the matrix metalloproteinase, MMP‐9. Antigen levels of MMP‐9 were ≈5‐fold lower in RAGEint9 vs. control, (p<0.0001), with activation of MMP‐9 completely blocked in RAGEint9 vs. control cells. Finally, tumor properties were reduced in RAGEint9 expressing cells compared to controls as assessed by migration assays (50% reduction, p<0.0001), and the formation of tumors in the soft agar assays (≈4‐fold reduction, p<0.0001). These data suggest RAGEint9 generation may be an endogenous mechanism for protection against tumor growth and/or its metastatic potential. Thus, RAGEint9 measurement may be a valuable clinical tool for predicting individuals at increased risk for cancer.