Figure 8. PGMI-004A treatment results in increased 3-PG and decreased 2-PG levels, and reduced cell proliferation of primary leukemia cells from human patients, as well as attenuated tumor growth in xenograft nude mice in vivo.
(A–B) Tumor growth (A) and tumor size (B) in xenograft nude mice injected with H1299 cells were compared between the group of mice treated with PGMI-004A and the control group treated with vehicle control. p values were determined by a two-tailed Student’s t test.
(C) PGAM1 protein expression (lower) and enzyme activity (upper) levels were examined using primary leukemia cells from diverse human patients with AML, CML and B-ALL and compared to control peripheral blood cells from healthy donors.
(D) Effect of PGMI-004A treatment on 3-PG (left) and 2-PG (right) levels in human primary leukemia cells isolated from peripheral blood samples from a representative AML patient.
(E) Effect of PGMI-004A treatment on cell viability (left), PGAM1 activity (middle) and lactate production (right) in human primary leukemia cells from a representative CML patient.
(F–G) Effect of methyl-2-PG treatment on decreased cell viability (F; G left) and lactate production (G right) in PGMI-004A-treated human primary leukemia cells from AML patients.
(H–I) PGMI-004A shows no toxicity in treatment (120h) of peripheral blood cells (H) and CD34+ cells isolated from bone marrow samples (I) from representative healthy human donors.
(J) Proposed model: role of PGAM1 in cancer cell metabolism.
Left: PGAM1 activity is upregulated in cancer cells to promote glycolysis and keep the intracellular 3-PG levels low, which in turn permits high levels of the PPP and biosynthesis to fulfill the request of rapidly growing tumors. PGAM1 also maintains the physiological levels of 2-PG to sustain PHGDH activity, which diverts 3-PG from glycolysis to serine synthesis and contributes to maintaining relatively low levels of 3-PG in cancer cells. These effects in concert provide a metabolic advantage to cancer cell proliferation and tumor growth.
Right: When PGAM1 is inhibited, 3-PG levels are elevated, which in turn inhibit 6PGD and consequently the oxidative PPP and anabolic biosynthesis. At the same time, 2-PG is decreased to levels below the physiological concentrations, leading to decreased PHGDH activity, which facilitates 3-PG accumulation. Such metabolic changes result in attenuated cell proliferation and tumor development.
The error bars represent mean values +/− SD from three replicates of each sample (*: 0.01<p<0.05; **: 0.01<p<0.01; ***: p<0.001; n.s.: not significant).