ARS | Publication request: Metastasis genetics, epigenetics, and the tumor microenvironment

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 8, 2011
Publication Date: June 26, 2011
Citation: Welch, D., Beck, B.H. 2011. Metastasis genetics, epigenetics, and the tumor microenvironment [abstract]. New Concepts of Metastasis, June 25-28, 2011, Lisbon, Portugal. p.2.

Technical Abstract: KISS1 is a member of a family of genes known as metastasis suppressors, defined by their ability to block metastasis without blocking primary tumor development and growth. KISS1 re-expression in multiple metastatic cell lines of diverse cellular origin suppresses metastasis; yet, still allows completion of steps of metastasis antecedent to colonization. Disseminated KISS1-expressing cells apparently remain dormant for extended periods. Secretion of full-length KISS1 or kisspeptins (proteolytic fragments of KISS1; KP) is required for metastasis suppression, but an autocrine feedback loop does not explain the findings because none of the tumor cell lines suppressed for metastasis by KISS1/KP express endogenously the G-protein coupled receptor, KISS1R. As a result, we hypothesized that KISS1 could operate via a paracrine mechanism with lung stromal cells. In support of this hypothesis, KISS1R was detected by RTQ-PCR and immunofluorescence in primary cultures derived from lung or skin (lung 8-fold more than skin). To begin exploring whether a KISS1/KP-KISS1R signaling axis might exist, full-length KISS1 or a mutant form of KISS1 which had a deleted signal sequence (designated Delta SS) were transfected into metastatic C8161.9 human melanoma cells. C8161.9 Delta SS cells colonized multiple tissues at a level equivalent to parental or empty-vector-transfected cells. Co-culture of C8161.9Vec, C8161.9KISS1 or C8161.9 Delta SS with primary cell cultures isolated from orthotopic tissue (i.e., skin) resulted in equivalent growth, but reduced (approximately 20%) growth occurred when co-cultured with ectopic (i.e., lung) cultures. Growth differences were exacerbated when KISS1 was expressed (~60% inhibition). To test directly paracrine feedback, lung or skin primary cultures were exposed to conditioned media (CM) collected from C8161.9Vec, C8161.9KISS1 or C8161.9 Delta SS cultures. After 24-48 hr, cell-free medium was collected from the skin (SCM) or lung (LCM) stromal cell cultures, added to C8161.9Vec or C8161.9KISS1 cells. Tumor cells exposed to SCM were not growth inhibited; however, C8161.9Vec and C8161.9KISS1 cells exposed to LCM were significantly (P<0.05) growth inhibited (38-42%, respectively). Although the majority of cells in the primary culture were fibroblasts, the overwhelming majority of immunofluorescence labeled KISS1R-positive cells were macrophages (F4/80+), especially alveolar Macrophage. Performing the same experiments with alveolar Macrophage-enriched cultures resulted in 35% growth inhibition (p<0.05) for the C8161.9Vec cells and a remarkable 80% (p<0.05) growth inhibition for C8161.9KISS1 cells. Since KISS1R is expressed by other tissue-derived macrophages (e.g., bone marrow, spleen, liver), the data suggest that KISS1 may suppress metastasis by paracrine signaling through macrophage populations. Taken together, the data begin to explain why KISS1-expressing cells grow in selected tumor microenvironments. Supported by RO1-CA134981, NFCR Center for Metastasis Research, Susan G. Komen for the Cure, Kansas Bioscience Authority and METAvivor.