The CCR9-CCL25 axis mediates melanoma metastasis to the small intestine.

摘要

BackgroundHuman cutaneous melanoma preferentially metastasizes to the small intestine for reasons that are unclear. Previous studies have shown that thymus-expressed cytokine (CCL25) mediates chemotaxis of CCR9 lymphocytes to the small intestine. Integrin alpha and beta are known to have a role in cellular adhesion, which is an important component of metastasis.ObjectiveTo determine the mechanism of lymphocyte trafficking and tumor cell metastasis in melanoma cells that metastasize to the small intestine.Design and interventionThis study included tumor specimens from patients who had undergone surgical resection for metastatic melanoma at either the John Wayne Cancer Institute or the Sydney Cancer Center between 1996 and 2005. Paraffin-embedded archival tissue from tumor specimens were obtained for primary melanomas (n=23), distant metastases (n = 198) and small intestinal metastases (n = 23). Quantitative reverse-transcription-PCR assays, flow cytometryand immunohistochemistry were usedto assess CCR9 and CCL25 expression in the specimens. Flow cytometry was used to assess expression of integrin alpha and beta.Outcome measuresExpression of CCR9, CCL25 and integrin a and (3 were the main outcome measures.ResultsIn total, 88 of 102 paraffin-em bedded specimens of small intestinal melanoma metastases expressed CCR9, as did all 8 melanoma cell lines derived from small intestinal metastases. There was no CCR9 expression in specimens derived from melanoma patients who had undergone surgical resection for isolated metastases to other organs. CCL25 expression was upregulatedin small intestinal melanoma metastases, and in vitro migration and invasion studies showed migration of CCR9-positive melanoma cells in response to CCL25. This response was inhibited by anti-CCR9 antibody and by CCR9 short interfering RNA. Flow cytometry analysis verified CCR9 expression in small intestinal melanoma metastases and showed associated alpha and beta integrin expression.ConclusionThis study shows that CCL25 initiates the migrationand invasion of CCR9-expressing melanoma cells, which results in preferential metastasis to the small intestine, thus, validating the role of the CCR9-CCL25 axis in metastasis of cutaneous melanoma to this specific location.