SLC6A8 and neoplasm: In line with our in vitro results, the mice injected with SLC6A8-functional tumor cells (MDA-MB-231/shNC) had bigger tumor burden than the ones injected with SLC6A8-silenced tumor cells (MDA-MB-231/shSlc6a8), and exogenous addition of creatine could notably promote tumor growth in SLC6A8-functional tumors rather than in SLC6A8-functional loss tumors (Fig. 8a-c).