GLS and chondrosarcoma: Second, we used the widely used anti-diabetic drug metformin, which, among other effects, indirectly inhibits glutaminase via c-Myc; (Fig. 1),21,22 inhibits complex 1 of the electron transport chain,20 and inhibits mTOR signalling.19 Indeed, a subset of chondrosarcoma cell lines was sensitive to metformin, especially when treated for a longer time period.