The incidence of many cancer types is significantly reduced in individuals with Down syndrome1–4 and it is proposed that this broad cancer protection is conferred by the elevated expression of one or more of the 231 supernumerary genes on the extra copy of chromosome 21. One such gene is the Down syndrome candidate region-1 (Dscr1, RCAN1), which encodes a protein that suppresses vascular endothelial growth factor (VEGF)-mediated angiogenic signalling via the calcineurin pathway5–10. Here we show that DSCR1 is elevated in Down syndrome individuals and a mouse model of Down syndrome. Further, we show that the modest elevation in expression afforded by a single extra transgenic copy of Dscr1 is sufficient to confer significant suppression of tumor growth in mice and that such resistance is a consequence of a deficit in tumor angiogenesis arising from suppression of the calcineurin pathway. We also provide evidence that attenuation of calcineurin activity by DSCR1 together with another chromosome 21 gene DYRK1A, may be sufficient to dramatically diminish angiogenesis. These data provide a mechanism for the reduced cancer incidence in Down syndrome and identifies the calcineurin signalling pathway and its regulators DSCR1 and DYRK1A as potential therapeutic targets in cancers arising in all individuals.

In cancer metastasis, various environmental stressors attack the disseminating cells. The successful colonization of cancer cells in secondary sites therefore requires the ability of the cells to avoid the consequences of such exposure to the stressors. Here we show that orthotopic transplantation of a CD44 variant isoform-expressing (CD44v + ) subpopulation of 4T1 breast cancer cells, but not that of a CD44v − subpopulation, in mice results in efficient lung metastasis accompanied by expansion of stem-like cancer cells. such metastasis is dependent on the activity of the cystine transporter xCT, and the stability of this protein is controlled by CD44v. We find that epithelial splicing regulatory protein 1 regulates the expression of CD44v, and knockdown of epithelial splicing regulatory protein 1 in CD44v + cells results in an isoform switch from CD44v to CD44 standard (CD44s), leading to reduced cell surface expression of xCT and suppression of lung colonization. The epithelial splicing regulatory protein 1-CD44v-xCT axis is thus a potential therapeutic target for the prevention of metastasis.

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Tie2 belongs to the receptor tyrosine kinase family and functions as a receptor for Angiopoietin-1 (Ang1). Gene-targeting analyses of either Ang1 or Tie2 in mice reveal a critical role of Ang1-Tie2 signalling in developmental vascular formation. It remains elusive how the Tie2 signalling pathway plays distinct roles in both vascular quiescence and angiogenesis. We demonstrate here that Ang1 bridges Tie2 at cell-cell contacts, resulting in trans-association of Tie2 in the presence of cell-cell contacts. In clear contrast, in isolated cells, extracellular matrix-bound Ang1 locates Tie2 at cell-substratum contacts. Furthermore, Tie2 activated at cell-cell or cell-substratum contacts leads to preferential activation of Akt and Erk, respectively. Microarray analyses and real-time PCR validation clearly show the differential gene expression profile in vascular endothelial cells upon Ang1 stimulation in the presence or absence of cell-cell contacts, implying downstream signalling is dependent upon the spatial localization of Tie2.

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