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Malignant melanoma is the most aggressive form of skin cancer and its incidence has doubled in the last two decades. It represents only 4% of skin cancer cases per year, but causes as many as 74% of skin cancer deaths. Early detection of malignant melanoma is associated with survival rates of up to 90%, but later detection (stage III to stage IV) is associated with survival rates of only 10%. Dysregulation of microRNA (miRNA) expression has been linked to tumor development and progression by functioning either as a tumor suppressor, an oncogene or a metastasis regulator in multiple cancer types. To understand the role of miRNA in the pathogenesis of malignant melanoma and identify biomarkers of metastasis, miRNA expression profiles in skin punches from 33 metastatic melanoma patients and 14 normal healthy donors were compared. We identified a cluster of 14 miRNAs on the X chromosome, termed the miR-506-514 cluster, which was consistently overexpressed in nearly all melanomas tested (30-60 fold, P<0.001), regardless of mutations in N-ras or B-raf. Inhibition of the expression of this cluster as a whole, or one of its sub-clusters (Sub-cluster A) consisting of six mature miRNAs, led to significant inhibition of cell growth, induction of apoptosis, decreased invasiveness and decreased colony formation in soft agar across multiple melanoma cell lines. Sub-cluster A of the miR-506-514 cluster was critical for maintaining the cancer phenotype, but the overexpression of the full cluster was necessary for melanocyte transformation. Our results provide new insights into the functional role of this miRNA cluster in melanoma, and suggest new approaches to treat or diagnose this disease.

Increased intracellular adhesion molecule 1 (ICAM-1) expression and enhanced monocyte recruitment to the endothelium are critical steps in the early development of atherosclerosis. The 15-lipoxygenase 1 (15-LOX1) pathway can generate several proinflammatory eicosanoids that are known to enhance ICAM-1 expression within the vascular endothelium. Oxidative stress can exacerbate endothelial cell inflammatory responses by modifying arachidonic acid metabolism through the 15-LOX1 pathway. Because selenium (Se) influences the oxidant status of cells and can modify the expression of eicosanoids, we investigated the role of this micronutrient in modifying ICAM-1 expression as a consequence of enhanced 15-LOX1 activity. Se supplementation reduced ICAM-1 expression in bovine aortic endothelial cells, an effect that was reversed with 15-LOX1 overexpression or treatment with exogenous 15-hydroperoxyoctadecadienoic acid (15-HPETE). ICAM-1 expression increased proportionately when intracellular15-HPETE levels were allowed to accumulate. However, changes in intracellular 15-HETE levels did not seem to affect ICAM-1 expression regardless of Se status. Our results indicate that Se supplementation can reduce 15-HPETE-induced expression of ICAM-1 by controlling the intracellular accumulation of this fatty acid hydroperoxide in endothelial cells.

Breast cancer development is associated with gene amplification and over expression that is believed to have a causative role in oncogenesis. Previous studies have demonstrated that over expression of TC-1(C8orf4) mRNA occurs in approximately 50% of breast cancer cell lines and primary tumor specimens. Here, we show that TC-1 has transforming properties in human mammary epithelial (HME) cells and its expression is mechanistically linked to FGFR signaling cascades. In vitro experiments demonstrate that TC-1 over expression mediates both anchorage-independent and growth factor-independent proliferation of HME cells. TC-1 was down regulated by the FGFR inhibitor PD173074 in the breast cancer cell line SUM-52 that also has an FGFR2 gene amplification and over expression. Furthermore, forced expression of FGFR2 in HME cells increased the level of expression of endogenous TC-1 mRNA. TC-1 has been implicated as a modulator of Wnt/beta-catenin signaling in 293 cells and in gastric cancer cells. However, while we did find increased expression of a subset of beta-catenin target genes in TC-1 over expressing cells, we did not find an association of TC-1 with global expression of beta-catenin target genes in our cells. Taken together, our data suggest that TC-1 over expression is transforming and may link with the FGFR pathway in a subset of breast cancer., ((c) 2007 Wiley-Liss, Inc.)

We have recently shown that an amphiregulin-mediated autocrine loop is responsible for growth factor-independent proliferation, motility, and invasive capacity of some aggressive breast cancer cells, such as the SUM149 breast cancer cell line. In the present study, we investigated the mechanisms by which amphiregulin activation of the epidermal growth factor receptor (EGFR) regulates these altered phenotypes. Bioinformatic analysis of gene expression networks regulated by amphiregulin implicated interleukin-1alpha (IL-1alpha) and IL-1beta as key mediators of amphiregulin's biological effects. The bioinformatic data were validated in experiments which showed that amphiregulin, but not epidermal growth factor, results in transcriptional up-regulation of IL-1alpha and IL-1beta. Both IL-1alpha and IL-1beta are synthesized and secreted by SUM149 breast cancer cells, as well as MCF10A cells engineered to express amphiregulin or MCF10A cells cultured in the presence of amphiregulin. Furthermore, EGFR, activated by amphiregulin but not epidermal growth factor, results in the prompt activation of the transcription factor nuclear factor-kappaB (NF-kappaB), which is required for transcriptional activation of IL-1. Once synthesized and secreted from the cells, IL-1 further activates NF-kappaB, and inhibition of IL-1 with the IL-1 receptor antagonist results in loss of NF-kappaB DNA binding activity and inhibition of cell proliferation. However, SUM149 cells can proliferate in the presence of IL-1 when EGFR activity is inhibited. Thus, in aggressive breast cancer cells, such as the SUM149 cells, or in normal human mammary epithelial cells growing in the presence of amphiregulin, EGFR signaling is integrated with NF-kappaB activation and IL-1 synthesis, which cooperate to regulate the growth and invasive capacity of the cells.

Amplification of the 8p11-12 region occurs in 15-20% of breast cancers, but the driving oncogene at this locus has yet to be definitively identified. We mapped the 8p11-12 amplicon in breast cancer cell lines and primary human breast cancers and identified the candidate oncogene human Sm-like protein (hLsm1, LSM1) based on increases in copy number and expression level relative to human mammary epithelial cells. To examine the oncogenic role of LSM1, we overexpressed this gene in MCF10A mammary epithelial cells and inhibited its production in the SUM44 breast cancer cell line, which has a natural amplification and overexpression of LSM1. Our data confirmed that LSM1 is an oncogene from the 8p11-12 amplicon by showing that hLsm1 overexpression induced growth factor-independent proliferation and soft agar colony formation in MCF10A cells, and hLsm1 inhibition in SUM44 cells dramatically reduced soft agar growth. Little is known about hLsm1 function other than its involvement in mRNA degradation; therefore, we used expression microarray analysis to investigate how hLsm1 affects cell transformation in MCF10A and SUM44 cells. We identified numerous genes altered following hLsm1 overexpression common to SUM44 breast cancer cells that play important roles in cell cycle regulation, cell proliferation and other cancer-promoting processes. Future work will continue to characterize these important changes to achieve a more complete understanding of the mechanism of hLsm1's effect on cancer progression.

The 8p11-p12 genomic region is amplified in 15% of breast cancers and harbors several candidate oncogenes. However, functional evidence for a transforming role for these genes is lacking. We identified 21 genes from this region as potential oncogenes based on statistical association between copy number and expression. We further showed that three of these genes (LSM1, BAG4, and C8orf4) induce transformed phenotypes when overexpressed in MCF-10A cells, and overexpression of these genes in combination influences the growth factor independence phenotype and the ability of the cells to grow under anchorage-independent conditions. Thus, LSM1, BAG4, and C8orf4 are breast cancer oncogenes that can work in combination to influence the transformed phenotype in human mammary epithelial cells.

Low selenium (Se) status increases angiogenesis by inducing the production of vascular endothelial growth factor (VEGF); however, the mechanism responsible for VEGF up-regulation has yet to be characterized. Se's ability to control cellular oxidative state through its incorporation into selenoproteins such as thioredoxin reductase (TrxR) may explain previous studies that connect Se status to tumor angiogenesis. Therefore, the focus of this study was to determine if altered VEGF expression and angiogenesis due to decreased Se levels are influenced by reduced TrxR activity. We found that chemical inhibition of TrxR in Se-sufficient endothelial cells (ECs) was associated with increases in VEGF and VEGF receptor expression, cell migration, proliferation, and angiogenesis to levels similar to those seen in Se-deficient ECs. Specific inhibition of glutathione peroxidase did not affect pro-angiogenic responses, indicating a unique role of the TrxR system during low Se status. These data correlate changes in TrxR activity with changes in VEGF expression and angiogenic development in ECs, which is significant because minimal mechanistic data exist that explain the role of Se in cancer prevention. Understanding the importance of the tumor microenvironment in contributing to angiogenic regulation has the potential to significantly impact breast cancer chemoprevention strategies by focusing on maintaining proper EC function within the mammary gland.

Lactation is considered the final phase of the mammalian reproductive cycle, and the mammary gland provides milk for nourishment and disease resistance to the newborn. However, the cellular and soluble immune components associated with mammary tissues and secretion also can play an important role in protecting the gland from infectious diseases, such as mastitis. Mastitis can affect essentially all lactating mammals, but is especially problematic for dairy cattle. The most recent estimates from the National Mastitis Council suggest that mastitis affects one third of all dairy cows and will cost the dairy industry over 2 billion dollars annually in the United States in lost profits (National Mastitis Council (1996) Current Concepts in Bovine Mastitis, National Mastitis Council, Madison, WI). The overall impact of mastitis on the quality and quantity of milk produced for human consumption has provided the impetus to better understand the pathophysiology of the mammary gland and develop ways to enhance disease resistance through immunoregulation. As such, the bovine species has played a critical and prominent role in our current understanding of mammary gland immunobiology. This paper provides a comprehensive overview of mammary gland immunity and how the stage of lactation can impact important host defenses While this review emphasizes the bovine system, comparisons to humans and other domestic mammals will be addressed as well.