“Furthermore, costunolide inhibited promoter activity of glutaminase 1 (GLS1), the first rate-limiting enzyme in glutaminolysis, and reduced mRNA and protein expression of GLS1 in HCT116 cells, The GLS1 inhibitor BPTES , similar to costunolide, significantly reduced intracellular levels of α-KG and ATP and inhibited proliferation in HCT116 cells.”