The invasive potential of human melanoma cell lines correlates with their ability to alter fibroblast gene expression in vitro and the stromal microenvironment in vivo

Abstract

The tumor microenvironment is thought to play an important role in invasion and metastasis. Previously, we have shown that signaling from melanoma cells can alter the gene expression profiles of fibroblasts in vitro and in vivo. To investigate whether the capacity to signal fibroblasts and alter host gene expression profiles is correlated to the invasive potential of specific human melanoma cell lines, we assayed changes in gene expression of fibroblasts when cocultured with the human melanoma cell lines BLM, MV3, A2058, SK-mel28 and WM164. Results indicated that the gene expression of key chemokines and cytokines, such as IL-1B, IL-8, IL-6 and CCL2/MCP1, was significantly upregulated in fibroblasts cocultured with the invasive melanoma lines BLM and MV3 compared to fibroblasts cocultured with noninvasive WM164 cells. The results were verified by quantitative RT-PCR as well as by protein assay and supported by immunohistochemistry of human invasive melanoma. Furthermore, a role for fibroblast-secreted IL-1B in the invasion of melanoma was demonstrated in vitro, where siRNA silencing of IL-1B in melanoma-stimulated fibroblasts resulted in a diminution of melanoma invasion. Although CCL2/MCP1, a chemoattractant for macrophages, was shown to be upregulated in fibroblasts cocultured with metastatic melanoma cell lines, immunohistochemical analysis of human melanoma also indicated CCL2/MCP1 production associated with the melanoma. In summary, these experiments indicate that the invasiveness of melanoma can partly be correlated to its ability to stimulate host stromal fibroblasts to give rise to the secretion of chemokines that generate a microenvironment that is conductive for melanoma invasion and metastasis. ' UICCKey words: melanoma; stroma; metastasis; IL-1B; invasion; gene expression; microenvironmentThe capacity for invasion and metastasis is one of the hallmarks of tumor malignancy. The role of host-tumor communication and the tumor microenvironment in tumor cell invasion and metastasis has been recognized as being critical in this process. 1 The complex interaction between invasive tumor cells, stromal cells, lymphocytes and extracellular matrix as represented by the invasive tumor microenvironment is only beginning to be understood. Further investigation in tumor microenvironments will generate new possibilities in terms of identifying key mechanisms of tumor cell invasion and metastasis and potentially therapeutic nodes for attenuating primary tumor metastasis. 2,3 Fibroblasts comprise one of the principal cell types of the stromal compartment, and recent studies have demonstrated that stromal fibroblasts are important in tumor cell migration through the stroma.4,5 Stimulation of resident stromal fibroblasts by the presence of invasive tumor cells gives rise to alterations in the gene and protein expression patterns of these cells, which have been interpreted as proinvasive and prometastatic.6 Upregulation of key chemokine and cytokine expression in stromal fibroblasts in the presence of migrating human m...

Leptin promotes the proliferation and migration of human breast cancer through the extracellular-signal regulated kinase pathway

“…Fibroblast growth with tumor cells resulted in increased production of chemokines whose source was the CAFs themselves. Chemokines such as leptin produced under these 'mixed' conditions promoted tumor promalignancy activities (38)(39)(40). The bidirectional cross-talk between breast cancer cells and CAFs drives tumor progression via leptin signaling (37).…”

Chemokines at the crossroads of tumor-fibroblast interactions that promote malignancy

“…[46, 82, 83, 87, 90 -95]), whose source is often in the CAFs themselves. The chemokines that were produced under the "mixed" conditions were shown to promote promalignancy activities, including angiogenesis, tumor cell migration/ invasion, and proliferation [46,82,83,87,90,92,93]. This indicates that the interactions between the 2 subpopulations are actually bidirectional: the tumor cells induce in the fibroblasts the release of promalignancy chemokines, and these in turn stimulate the proliferation, migration, and invasion of the tumor cells.…”

Loss of stromal caveolin-1 expression in malignant melanoma metastases predicts poor survival

“…The tumor microenvironment, consisting of stromal fibroblasts, immune cells, endothelial cells and extracellular matrix, facilitates tumor cell invasion and metastasis by promoting angiogenesis and lymphangiogenesis. [4][5][6] Cancer-associated fibroblasts are also known to stimulate cancer progression by secreting factors that elevate the threshold for apoptosis and increase proliferation (i.e., IGF-1, PDGF, bFGF and TGFβ). 5,7,8 Caveolins (Cav-1, -2 and -3) are the principal structural proteins coating caveolae, small omega-shaped invaginations of the plasma membrane, measuring 50-100 nm in diameter.…”

“…[4][5][6] Cancer-associated fibroblasts are also known to stimulate cancer progression by secreting factors that elevate the threshold for apoptosis and increase proliferation (i.e., IGF-1, PDGF, bFGF and TGFβ). 5,7,8 Caveolins (Cav-1, -2 and -3) are the principal structural proteins coating caveolae, small omega-shaped invaginations of the plasma membrane, measuring 50-100 nm in diameter. Caveolae participate in vesicular trafficking events and signal transduction processes, and the caveolin family functions as scaffolding proteins to organize and concentrate specific lipids and lipidmodified signaling molecules.…”