New role for tRNA and its fragment purified from human urinary bladder carcinoma conditioned medium: Inhibition of endothelial cell growth

The growth of endothelial cells is necessary for angiogenesis, which in tur n is required for later steps of tumor progression. In an attempt to purify new modulators of endothelial cell growth from the conditioned medium of h uman urinary bladder carcinoma cells, we isolated a small and stable oligon ucleotide containing 10 to 16 bases. This oligonucleotide inhibited the gro wth Of endothelial cells in vitro and was identified as a fragment Of trans fer RNA (tRNA). When unfractionated bovine tRNA was added to the cell cultu re, it specifically inhibited growth of endothelial cells, but not smooth m uscle cells, bovine kidney cells, 3T3 fibroblasts, and several cancer cell lines. In contrast, ribosomal RNA, total yeast RNA, and single nucleosides from tRNA hydrolysate had no effect. These results demonstrate a new role f or tRNA and its fragment as a selective endothelial cell inhibitor in vitro . J. Cell. Biochem. 76:109-117, 1999. (C) 1999 Wiley-Liss, Inc.