The Role of Threonyl-tRNA Synthetase in Regulating Autophagy in Ovarian Cancer

Autophagy is the process by which lysosomes degrade and recycle damaged proteins and organelles in order to promote cell survival under situations of nutrient deprivation and homeostatic stress. Studies in the Lounsbury Lab have identified threonyl-tRNA synthetase (TARS) as a potential regulator in the autophagy pathway. This study tests the hypotheses that TARS independently inhibits the process of autophagy within human ovarian cancer cells and that blocking TARS signaling increases markers of autophagy within tumors in a mouse model of ovarian cancer. Ovarian cancer cells were cultured and transfected with siRNA to reduce TARS levels and quantitative Western blotting was employed to test the effects of TARS knockdown during amino acid starvation or mTOR inhibition. Changes were detected using antibodies against TARS, the positive autophagy markers p-AMPK and p-ULK, and the protein p62. TARS knockdown by siRNA was successful (pin vivoeffects of TARS activity on autophagy, mice were injected subcutaneously with ID-8 ovarian cancer cells. After three weeks, the animals were treated three times per week with either vehicle control or the TARS inhibitor BC194. Tumor sections were analyzed by immunohistochemistry to detect TARS, autophagy, and inflammatory markers. Tumors treated with BC194 were larger and showed increased levels of TARS. The results of this study have strong implications for the potential to identify a novel therapeutic target in ovarian cancer treatment