The Ku70-SIX1-GPT2 axis regulates alpha-ketoglutarate metabolism to drive progression of prostate cancer.

Sine oculis homeobox homolog 1 (SIX1) is a new identified cancer driver in the development of prostate cancer (PC). However, the upstream regulatory mechanisms for SIX1 reactivation in cancer remains elusive. Here, we found that Ku70 robustly interacts with SIX1 in the nucleus of PC cells. The HD domain of SIX1 and the DBD domain of Ku70 are required for formation of Ku70-SIX1 complex. 20 groups of hydrogen bonds were identified in this complex by molecular dynamics simulation. Depletion of Ku70/SIX1 notably abrogates the proliferation and migration of PC. Further studies revealed that SIX1 is recruited to the promoter region on glutamate-pyruvate transaminase 2 (GPT2). Ku70 enhances the SIX1-mediated transcriptional activation on GPT2, thereby facilitating the generation of alpha-ketoglutarate (α-KG). In addition, formation of the Ku70-SIX1 complex promotes GPT2-dependent cell proliferation and migration in PC. Moreover, the expression of GPT2 is upregulated and strongly correlated with the expression of Ku70/SIX1 in PC tissues. In summary, our findings not only provide insight into the mechanistic interactions between Ku70 and SIX1, but also highlight the significance of the Ku70-SIX1-GPT2 axis for α-KG metabolism and PC carcinogenesis.