DKK1 expression is down-regulated in the lymph node pre-metastatic niche in esophageal cancer

Lymph node metastasis is a poor prognosis indicator in esophageal cancer. Although tumor spreading currently forms the main basis for therapy selection, the molecular mechanisms underlying the metastatic pathway remain insufficiently understood. Several studies aimed to investigate these mechanisms but focused mainly on regulatory patterns in the tumors themselves and/or the invaded lymph nodes. To date no study has yet investigated the potential changes on transcription level, which take place within the yet non-invaded niche. Here we provide a comprehensive description of these regulations in patients. In this study the transcriptomic profiles of regional lymph nodes were determined for two patient groups: patients classified as pN1 (metastasis) or pN0 (no metastasis) respectively. All investigated lymph nodes, also those from pN1 patients, were still free of metastasis. The gene expression data was obtained via microarray analysis. Top candidates were validated via PCR and immunohistochemistry. The results show that regional lymph nodes of pN1 patients differ decisively from those of pN0 patients even before metastasis has taken place. In the pN0 group distinct immune response patterns were observed. In contrast, lymph nodes of the pN1 group exhibited a clear profile of reduced immune response and reduced proliferation, but increased apoptosis, enhanced hypoplasia and morphological conversion processes. DKK1 was the most significant gene associated with the molecular mechanisms taking place in lymph nodes of patients suffering from metastasis (pN1). We assume that the two molecular profiles observed constitute two different stages of a progressive disease. Finally we suggest that DKK1 might play an important role within the mechanisms leading to lymph node metastasis.

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Otto B, Koenig AM, Tolstonog GV, Jeschke A, Klaetschke K, Vashist YK, Wicklein D, Wagener C, Izbicki JR, Streichert T