Tumour angiogenesis is reduced in the Tc1 mouse model of Down’s syndrome

Abstract

Down's syndrome is caused by the presence of an extra copy of chromosome 21 (a state known as trisomy), and it is known that the growth of certain tumours is reduced in this genetic disorder. A study of a mouse model of Down's syndrome points to an antitumour mechanism, the inhibition of tumour angiogenesis by the overexpression of four genes, two putative anti-angiogenic genes (ADAMTS1 and ERG) and two novel endothelial cell-specific genes not previously linked with angiogenesis (JAM-B and PTTG1IP). Down's syndrome is caused by trisomy of chromosome 21, and it is known that the growth of certain tumours is reduced in this genetic disorder. Using a mouse model of Down's syndrome, several individual genes on chromosome 21 are now being proposed to mediate the effect on tumour growth and angiogenesis. Down’s syndrome (DS) is a genetic disorder caused by full or partial trisomy of human chromosome 21 and presents with many clinical phenotypes including a reduced incidence of solid tumours1,2. Recent work with the Ts65Dn model of DS, which has orthologues of about 50% of the genes on chromosome 21 (Hsa21), has indicated that three copies of the ETS2 (ref. 3) or DS candidate region 1 (DSCR1) genes4 (a previously known suppressor of angiogenesis5,6) is sufficient to inhibit tumour growth. Here we use the Tc1 transchromosomic mouse model of DS7 to dissect the contribution of extra copies of genes on Hsa21 to tumour angiogenesis. This mouse expresses roughly 81% of Hsa21 genes but not the human DSCR1 region. We transplanted B16F0 and Lewis lung carcinoma tumour cells into Tc1 mice and showed that growth of these tumours was substantially reduced compared with wild-type littermate controls. Furthermore, tumour angiogenesis was significantly repressed in Tc1 mice. In particular, in vitro and in vivo angiogenic responses to vascular endothelial growth factor (VEGF) were inhibited. Examination of the genes on the segment of Hsa21 in Tc1 mice identified putative anti-angiogenic genes (ADAMTS18,9and ERG10) and novel endothelial cell-specific genes11, never previously shown to be involved in angiogenesis (JAM-B12 and PTTG1IP), that, when overexpressed, are responsible for inhibiting angiogenic responses to VEGF. Three copies of these genes within the stromal compartment reduced tumour angiogenesis, explaining the reduced tumour growth in DS. Furthermore, we expect that, in addition to the candidate genes that we show to be involved in the repression of angiogenesis, the Tc1 mouse model of DS will permit the identification of other endothelium-specific anti-angiogenic targets relevant to a broad spectrum of cancer patients.