Interleukin 8 (IL-8) is mitogenic and chemotactic for endothelial cells. Within a neoplasm, IL-8 is secreted by inflammatory and neoplastic cells. The highly metastatic PC-3M-LN4 cell line ...overexpresses IL-8 relative to the poorly metastatic PC-3P cell line. We evaluated whether IL-8 expression by human prostate cancer growing within the prostate of athymic nude mice regulates tumor angiogenesis, growth, and metastasis. PC-3P cells were transfected with the full-length sense IL-8 cDNA, whereas PC-3M-LN4 cells were transfected with the full-sequence antisense IL-8 cDNA. Control cells were transfected with the neomycin resistance gene (Neo). In vitro, sense-transfected PC-3P cells overexpressed IL-8-specific mRNA and protein, which resulted in up-regulation of matrix metalloproteinase 9 (MMP-9) mRNA, and collagenase activity, resulting in increased invasion through Matrigel. After antisense transfection of the PC-3M-LN4 cells, IL-8 and MMP-9 expression, collagenase activity, and invasion were markedly reduced relative to controls. After orthotopic implantation, the sense-transfected PC-3P cells were highly tumorigenic and metastatic, with significantly increased neovascularity and IL-8 expression compared with either PC-3P cells or controls. Antisense transfection significantly reduced the expression of IL-8 and MMP-9 and tumor-induced neovascularity, resulting in inhibition of tumorigenicity and metastasis. These results demonstrate that IL-8 expression regulates angiogenesis in prostate cancer, in part by induction of MMP-9 expression, and subsequently regulates the growth and metastasis of human prostate cancer.
Host immunity affects tumor metastasis but the corresponding cellular and molecular mechanisms are not entirely clear. Here, we show that a subset of B lymphocytes (termed B-1 population), but not ...other lymphocytes, has prometastatic effects on melanoma cells in vivo through a direct heterotypic cell-cell interaction. In the classic B16 mouse melanoma model, one mechanism underlying this phenomenon is a specific up-regulation and subsequent homophilic interaction mediated by the cell surface glycoprotein MUC18 (also known as melanoma cell adhesion molecule). Presence of B-1 lymphocytes in a panel of tumor samples from melanoma patients directly correlates with MUC18 expression in melanoma cells, indicating that the same protein interaction exists in humans. These results suggest a new but as yet unrecognized functional role for host B-1 lymphocytes in tumor metastasis and establish a biochemical basis for such observations. Our findings support the counterintuitive central hypothesis in which a primitive layer of the immune system actually contributes to tumor progression and metastasis in a mouse model and in melanoma patients. Given that monoclonal antibodies against MUC18 are in preclinical development but the reason for their antitumor activity is not well understood, these translational results are relevant in the setting of human melanoma and perhaps of other cancers.
An inflammatory tumor microenvironment fosters tumor growth, angiogenesis and metastatic progression. Platelet-activating factor (PAF) is an inflammatory biolipid produced from membrane ...glycerophospholipids. Through the activity of its G-protein coupled receptor, PAF triggers a variety of pathological reactions including tumor neo-angiogenesis. Several groups have demonstrated that inhibiting PAF-PAF receptor pathway at the level of a ligand or receptor results in an effective inhibition of experimental tumor growth and metastasis. In particular, our group has recently demonstrated that PAF receptor antagonists can effectively inhibit the metastatic potential of human melanoma cells in nude mice. Furthermore, we showed that PAF stimulated the phosphorylation of CREB and ATF-1 in metastatic melanoma cells, which resulted in overexpression of MMP-2 and MT1-MMP. Our data indicate that PAF acts as a promoter of melanoma metastasis in vivo. Since only metastatic melanoma cells overexpress CREB/ATF-1, we propose that these cells are better equipped to respond to PAF within the tumor microenvironment when compared to their non-metastatic counterparts.
In recent years, the incidence of cutaneous melanoma has increased more than that of any other cancer. Dacarbazine is considered the gold standard for treatment, having a response rate of 15% to 20%, ...but most responses are not sustained. Previously, we have shown that short exposure of primary cutaneous melanoma cells to dacarbazine resulted in the upregulation of interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The purpose of the present study was to determine how long-term exposure of melanoma cells to dacarbazine would affect their tumorigenic and metastatic potential in vivo.
The primary cutaneous melanoma cell lines SB2 and MeWo were repeatedly exposed in vitro to increasing concentrations of dacarbazine, and dacarbazine-resistant cell lines SB2-D and MeWo-D were selected and examined for their ability to grow and metastasize in nude mice.
The dacarbazine-resistant cell lines SB2-D and MeWo-D exhibited increased tumor growth and metastatic behavior in vivo. This increase could be explained by the activation of RAF, MEK, and ERK, which led to the upregulation of IL-8 and VEGF. More IL-8, VEGF, matrix metalloproteinase-2 (MMP-2), and microvessel density (CD-31) were found in tumors produced by SB2-D and MeWo-D in vivo than in those produced by their parental counterparts. No mutations were observed in BRAF.
Our results have significant clinical implications. Treatment of melanoma patients with dacarbazine could select for a more aggressive melanoma phenotype. We propose that combination treatment with anti-VEGF/IL-8 or MEK inhibitors may potentiate the therapeutic effects of dacarbazine.
Chronic myelogenous leukemia (CML) invariably progresses to blast crisis, which represents the most proliferative phase of the disease. The BCR-ABL1 oncogene stimulates growth and survival pathways ...by phosphorylating numerous substrates, including various Src family members. Here we describe up-regulation, in contrast to activation, of the ubiquitously expressed Src kinase, Fyn, by BCR-ABL1. In a tissue microarray, Fyn expression was significantly increased in CML blast crisis compared with chronic phase. Cells overexpressing BCR-ABL1 in vitro and in vivo display an up-regulation of Fyn protein and mRNA. Knockdown of Fyn with shRNA slows leukemia cell growth, inhibits clonogenicity, and leads to increased sensitivity to imatinib, indicating that Fyn mediates CML cell proliferation. In severe combined immunodeficient (SCID) mice injected with Fyn shRNA–expressing cells, myeloid-derived cell numbers dropped by 50% and death from leukemia was delayed. Taken together, these results encourage the development of therapies targeting Fyn expression.
Most studies accept a multistep pathogenic process in melanoma that may include the phases of benign nevi and dysplastic nevi, melanoma, and metastatic melanoma. Dysregulation of cellular ...proliferation and apoptosis is probably involved in melanoma progression and response to therapy. We have studied the expression of galectin-3, a beta-galactoside-binding protein involved in apoptosis, angiogenesis, and cell proliferation, in a large series of melanocytic lesions, and correlated the expression with clinical and histologic features.
Tissue microarray blocks of 94 melanocytic lesions were semiquantitatively evaluated by immunohistochemistry for the cytoplasmic or nuclear expression of galectin-3.
Primary and metastatic melanomas expressed galectin-3 at a significantly higher level than nevi in both cytoplasm and nuclei (P<0.0073). There was a significant association between anatomic source (as indirect indication of level of sun-exposure) and cytoplasmic and nuclear expression. Lymph node and visceral metastases had a higher level of expression than s.c. lesions (P<0.004). Interestingly, there was an almost significant finding of worse survival in those patients with lesions showing higher levels of cytoplasmic than nuclear galectin-3 expression (log-rank test, P=0.06).
Melanocytes accumulate galectin-3 with tumor progression, particularly in the nucleus. The strong association of cytoplasmic and nuclear expression in lesions of sun-exposed areas suggests an involvement of UV light in activation of galectin-3.
Cellular adhesion molecules of the cadherin, integrin, and immunoglobulin superfamilies are important to both growth and metastasis of many cancers, including malignant melanoma. Malignant melanoma ...is an excellent model for studying these molecules, due in part to a sequential series of five defineable stages. As the malignant phenotype of melanoma cells changes from the noninvasive radial growth phase to the vertical growth phase, which has high metastatic potential, so does the repertoire of the cellular adhesion molecules expressed on the cells surface. The cellular adhesion molecule MCAM/MUC18 confers metastatic potential and increased tumorigenicity to melanoma cells. MCAM/MUC18 mediates homotypic and heterotypic adhesion between melanoma cells and endothelial cells, respectively. Both types of interaction may promote metastasis at different stages in the metastasis cascade. We developed a fully humanized antibody to MCAM/MUC18 (ABX-MA1) that blocked melanoma metastasis in vivo. Furthermore, ABX-MA1 blocked the homotypic interaction between melanoma cells and endothelial cells as well as the promoter and collagenase activity of MMP-2. During melanoma progression the loss of E-cadherin expression disrupts normal homeostasis in the skin by freeing melanoma cells from structural and functional regulation by keratinocytes. The loss of functional E-cadherin is parallelled by a gain in N-cadherin function that mediates homotypic interaction between melanoma cells, facilitates gap-junctional formation with fibroblasts and endothelial cells and promotes melanoma cell migration and survival. In addition, loss of E-cadherin may affect the beta-catenin/wnt signaling pathways, resulting in deregulation of genes involved in growth and metastasis. The integrin family member alpha(v)beta(3) is widely expressed on melanoma cells in the vertical growth phase. When alpha(v)beta(3) is expressed in melanoma cells in the radial growth phase, this integrin is associated with increased tumor growth in vivo. alpha(v)beta(3) may also promote melanoma invasion, through an interaction with MMP-2, and transendothelial migration, via a heterotypic melanomaendothelial cell interaction. This review summarizes recent knowledge on how changes in these adhesion molecules contribute to the acquisition of the metastatic phenotype in human melanoma.
The embryonic morphogen Nodal, a member of the transforming growth factor-β superfamily, is not expressed in the majority of normal adult tissues. However, a growing body of evidence indicates that ...Nodal expression re-emerges in a number of human cancers, including melanoma, glioma, endometrial, and prostate cancers. Reactivation of Nodal signaling in these tumors contributes to their aggressiveness. Strizzi and colleagues, in a paper published in this issue of Breast Cancer Research, investigate the clinical significance of Nodal expression in breast cancer. They report that Nodal expression is significantly greater in malignant versus benign breast disease. More importantly, Nodal levels correlated with grading, staging, and lymph node involvement, independent of the estrogen receptor/progesterone receptor or HER2 status. Collectively, these data suggest that Nodal could serve as a potential biomarker for invasive disease and a potential therapeutic target in breast cancer.
We previously demonstrated that expression of the cell surface adhesion molecule MCAM/MUC18 correlates directly with the metastatic potential of human melanoma cells. In addition, the progression of ...human melanoma towards the metastatic phenotype is associated with loss of expression of the tyrosine-kinase receptor c-KIT. This review summarizes our recent data demonstrating that the expression of both genes is regulated by the AP-2 transcription factor. Moreover, we have observed a loss of AP-2 expression in metastatic melanoma cells. Re-expression of AP-2 in the highly metastatic A375SM cells decreased their tumorigenicity and inhibited their metastatic potential in nude mice. MCAM/MUC18 mRNA and protein expression was significantly downregulated while c-KIT expression was upregulated in the AP-2 transfected cells. Since AP-2 also regulates other genes that are involved in the progression of human melanoma such as E-cadherin, MMP-2, p21WAF-1, HER-2, BCL-2, and insulin like growth factor receptor-1, we propose that loss of AP-2 is a crucial event in the development of malignant melanoma.
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