The current understanding of the Warburg effect consists of an increase in aerobic glycolysis in cancer cells. The connection between glycolysis and PPP/biosynthesis is based upon a model in which glycolytic intermediates can be diverted into PPP and biosynthesis pathways as precursors. However, it remains unclear how cancer cells coordinate glycolysis and biosynthesis to fulfill the request of rapidly growing tumors. We found that glycolytic enzyme phosphoglycerate mutase 1 (PGAM1), commonly upregulated in human cancers including leukemias due to loss of TP53, regulates anabolic biosynthesis by controlling intracellular levels of its substrate 3-phosphoglycerate (3-PG) and product 2-phosphoglycerate (2-PG). Our co-crystal structure based analysis revealed that 3-PG binds to and inhibits 6-phosphogluconate dehydrogenase in the oxidative pentose phosphate pathway (PPP) as a competitive inhibitor, while 2-PG activates 3-phosphoglycerate dehydrogenase (PHGDH) to provide feedback control of 3-PG levels. Inhibition of PGAM1 by shRNA results in increased 3-PG and decreased 2-PG levels in cancer and leukemia cells, leading to significantly decreased glycolysis, PPP flux and biosynthesis, as well as attenuated cell proliferation and tumor growth. These findings uncover that PGAM1 controls the intracellular 3-PG and 2-PG levels to serve as a novel link between glycolysis, biosynthesis, cancer/leukemia cell proliferation and tumor development.
Moreover, we found that PGAM1 protein expression and enzyme activity levels are commonly upregulated in diverse human leukemia cell lines, as well as in primary leukemia cells from human AML, CML and B-ALL patients. We screened and developed novel small molecule PGAM1 inhibitor (PGMI)-004A, which effectively inhibits PGAM1 enzyme activity, resulting in aberrant leukemia cell metabolism with reduced glycolysis and PPP/anabolic biosynthesis, as well as attenuated cell proliferation in diverse human leukemia cell lines, but not control normal human proliferating cells including human dermal fibroblasts and human foreskin fibroblasts. In addition, PGMI-004A treatment attenuates tumor growth in xenograft nude mice with minimal toxicity in vivo. Furthermore, PGMI-004A inhibits cell proliferation of primary leukemia cells from human AML, CML and B-ALL patients, but not control CD34+ cells isolated from bone marrow samples or mononucleocytes isolated from peripheral blood samples from healthy donors, suggesting minimal toxicity of PGMI-004A in human cells.
Together, our findings demonstrate that PGAM1 regulates the concentrations of glycolytic metabolites 3-PG and 2-PG, which function as signaling molecules to directly affect the catalytic activity of enzymes involved in PPP and biosynthesis, representing a novel, additional link between glycolysis, PPP and biosynthesis. PGAM1 is commonly upregulated in human leukemia cells and important for cell metabolism and proliferation, representing a promising therapeutic target in treatment of leukemias. Small molecule inhibitor of PGAM1, PGMI-004A exhibits promising efficacy and minimal toxicity in treatment of xenograft nude mice and human primary leukemia cells, providing “proof of principle” for the development of PGAM1 inhibitors as anti-leukemia agents.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.