Targeting Glycolytic Enzymes in Cancer Cells (Warburg Effect)

Figure 1.

Cancer cells upregulate glycolytic enzymes and rely on aerobic glycolysis (the Warburg effect) to support rapid growth, survival, and metastasis, even when oxygen is available. These same enzymes create multiple therapeutic vulnerabilities, so targeting them can impair tumor metabolism, sensitize tumors to therapy, and modulate the tumor microenvironment. (1-3)

The Warburg effect describes high glucose uptake and conversion of glucose to lactate in the presence of sufficient oxygen, with reduced reliance on oxidative phosphorylation.​ This metabolic shift provides rapid ATP production and abundant intermediates for biosynthesis (nucleotides, lipids, amino acids), supporting uncontrolled proliferation.​ Oncogenes (MYC, PI3K/Akt/mTOR) and hypoxia-inducible factor drive expression of glycolytic genes, integrating metabolism with growth signaling.

Key glycolytic enzymes. Glucose transporters (GLUT1), hexokinase 2 (HK2), phosphofructokinase (PFK), pyruvate kinase M2 (PKM2), lactate dehydrogenase A (LDHA), and pyruvate dehydrogenase kinase (PDK1) are frequently overexpressed in cancer. A high glycolytic flux is associated with an aggressive tumor and poor prognosis.

Enhanced glycolysis supports:

• Fast ATP generation and biosynthesis needed for rapid cell division.

• Maintenance of redox balance (NAD⁺/NADH) and control of reactive oxygen species.

• Acidification of the microenvironment via lactate export, which promotes invasion, angiogenesis, and immune evasion.​

Hypoxia-Inducible Factor-1α (HIF-1α)

HIF-1α serves as the master transcriptional regulator of aerobic glycolysis, upregulating expression of glucose transporters and key glycolytic enzymes under both hypoxic and normoxic conditions in cancer cells.

Glycolysis is co-regulated with glutamine metabolism and other pathways, creating an integrated metabolic network that supports growth and treatment resistance.

Glucose Transporters (GLUT1 and GLUT4)

Glucose transporters facilitate the enhanced glucose uptake characteristic of the Warburg effect, with GLUT1 and GLUT4 significantly overexpressed in cancer cells.

Hexokinase 2 (HK2)

Hexokinase catalyzes the first committed step of glycolysis, phosphorylating glucose toglucose-6-phosphate, with HK2 predominantly expressed in cancer cells.

Phosphofructokinase (PFK)

Phosphofructokinase catalyzes the committed step of glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate, representing a critical rate-limiting enzyme.

Pyruvate Kinase M2 (PKM2)

PKM2 serves as the final rate-limiting enzyme in glycolysis, catalyzing conversion of phosphoenolpyruvate to pyruvate, and possesses non-metabolic “moonlighting” functions when translocated to the nucleus.

Lactate Dehydrogenase A (LDHA)

Lactate dehydrogenase catalyzes the final step of anaerobic glycolysis, converting pyruvate to lactate while regenerating NAD⁺, enabling continued glycolytic flux under the Warburg effect.

Pyruvate Dehydrogenase Kinase (PDK) and Pyruvate Metabolism

PDK phosphorylates and inactivates the pyruvate dehydrogenase complex (PDC), preventing pyruvate conversion to acetyl-CoA and forcing pyruvate toward lactate production—a hallmark of the Warburg effect.

Rationale for targeting glycolytic enzymes.

• Cancer cells are more dependent on glycolysis than most normal tissues, creating a therapeutic window in which inhibition selectively harms tumor cells.​

• Inhibitors of GLUT1, HK2, PFKFB3, PKM2, and LDHA reduce ATP production, disrupt biosynthesis, and can reverse resistance in settings such as breast cancer and pancreatic cancer models.

Agents Targeting Glycolytic Enzymes

The five major compounds—curcumin, ivermectin, epigallocatechin gallate (EGCG), sulforaphane, and melatonin—demonstrate significant suppressive effects on glycolytic enzymes central to the Warburg effect, including hypoxia-inducible factor-1α (HIF-1α), glucose transporters (GLUT1/4), hexokinase 2 (HK2), pyruvate kinase M2 (PKM2), and lactate dehydrogenase A (LDHA). The mechanisms and potencies vary considerably, with curcumin and EGCG showing direct enzyme inhibition at micromolar concentrations, ivermectin targeting glucose transporter pathways, sulforaphane modulating PKM2 moonlighting functions, and melatonin acting primarily through HIF-1α inactivation and pyruvate dehydrogenase kinase (PDK) suppression (See Figures 1 & 2).

Curcumin. Curcumin is very powerful blocker of multiple Warburg enzymes at micromolar concentrations! Curcumin decreases glucose uptake and lactate production in several cancer cell lines (lung, breast, cervical, prostate), consistent with Warburg‑effect suppression.

Mechanistically curcumin:

• Inhibits mTOR–HIF‑1α signaling, reducing HIF‑1α activity and expression.

• Curcumin reduces expression of pyruvate kinase M2 (PKM2), a central regulator of the Warburg effect that controls glycolytic flux and anabolic channeling of intermediates in cancer cells.

• Shows selectivity for cancer cells vs HEK293 non‑malignant cells, where glycolysis is less affected at similar concentrations.

• Curcumin downregulates HK2 expression and activity in multiple cancer cell types in a concentration-dependent manner

• Curcumin directly inhibits GLUT1 transport activity.

• Acts synergistically with EGCG.(4-6)

Ivermectin

• Pharmacoproteomic work in ovarian cancer indicates ivermectin inhibits glycolysis, TCA cycle, and oxidative phosphorylation pathways globally, reducing energy metabolism.

• Mechanisms include mitochondrial inhibition and possible reduction of tumor hypoxia, which may indirectly impact HIF‑1α activity, though direct, detailed HIF‑1α/GLUT1/HK data remain sparse.

• Ivermectin inhibits glycolysis by blocking GLUT4-mediated activation of the JAK/STAT signaling pathway.

• In glioma cells, ivermectin reduces protein levels of hexokinase 2 (HK2) and phosphofructokinase‑1 (PFK1)

EGCG (green tea catechin).

• EGCG reduces GLUT1 expression in breast and pancreatic cancer cells; this appears linked to inhibition of HIF‑1α, which regulates GLUTs and multiple glycolytic enzymes.

• EGCG directly inhibits the activity and often mRNA/protein levels of hexokinase (HK), phosphofructokinase (PFK), and lactate dehydrogenase (LDH)

• A EGCG suppresses HIF‑1α protein accumulation (without necessarily lowering its mRNA), in part via interference with PI3K/Akt/mTOR‑dependent translation

• Also reported to lower glycolytic enzyme activity more broadly in tumor microenvironment models.

Sulforaphane

• Sulforaphane reduces expression of central glycolytic enzymes such as hexokinase I/II (HK1/2), pyruvate kinase M2 (PKM2), and lactate dehydrogenase A (LDHA) in cancer cells and tumor tissue

• Sulforaphane suppresses hypoxia‑induced HIF‑1α protein and downstream VEGF expression in colon and gastric cancer cells.

• Through HIF‑1α inhibition, it is expected to reduce expression of HIF‑1 targets such as GLUT1, HK2, and LDHA, though direct measurements of those specific glycolytic genes are more limited than for curcumin or resveratrol.

Melatonin

• Melatonin can redirect tumor metabolism away from glycolysis (“Warburg‑dependent cancer”) toward mitochondrial oxidation and has been shown to reduce HIF‑1‑driven angiogenesis and Warburg signaling in some models.

• Melatonin uniquely targets PDK as its primary mechanism for reversing the Warburg effect. Melatonin inhibits HIF-1α, thereby decreasing PDK activity and disinhibiting PDH, allowing pyruvate to enter mitochondria for conversion to acetyl-CoA. This metabolic shift from cytosolic glycolysis to mitochondrial oxidative phosphorylation restores a more normal cellular phenotype

• In bladder cancer, melatonin represses glycolysis via a PPARγ–ENO1–glycolysis axis, decreasing ENO1 and glycolytic flux.

• Melatonin reduces glucose uptake and modifies GLUT1 transporter expression in prostate cancer cells. Docking simulation studies demonstrate that melatonin interacts at the same location in GLUT1 where glucose binds. Glucose concentration and competitive GLUT1 ligands affect cellular melatonin concentration, supporting direct GLUT1 interaction.

• Additional work shows melatonin can reduce glycolysis and increase pyruvate dehydrogenase activity in ovarian cancer, further opposing the Warburg effect.

Resveratrol

• Resveratrol reduces expression and/or activity of several rate‑limiting glycolytic enzymes, including hexokinase 2 (HK2), phosphofructokinase (PFK isoforms), pyruvate kinase M2 (PKM2), phosphoglycerate kinase 1 (PGK1) and lactate dehydrogenase A (LDH‑A) in multiple cancer cell lines

• Resveratrol reduces glucose uptake and glycolysis by modulating GLUT1, PFK1, HIF‑1α, ROS, and the CaMKKβ–AMPK pathway.

• Resveratrol decreases glucose uptake and lactate production by inhibiting GLUT1 via AKT/mTOR‑dependent signaling

Vitamin D

• Vitamin D signaling intersects with hypoxia pathways: calcitriol can reduce HIF1A and EPAS1 mRNA translation via changes in ribosomal association and AKT signaling in hepatoma cells.

• This suggests a potential to down‑tune HIF‑driven glycolytic gene expression; direct, systematic profiling of GLUT1/HK2/LDHA under calcitriol is, however, less robust than for curcumin, resveratrol, or metformin.

Metformin

• Metformin activates AMPK and has repeatedly been shown to inhibit HIF‑1α activation under hypoxia, thereby opposing upregulation of multiple glycolytic enzymes.

• In oral squamous carcinoma, metformin increased pyruvate dehydrogenase (PDH) activity and suppressed HIF‑1α, reducing the Warburg shift of pyruvate toward lactate and promoting entry into the TCA cycle.

• Metformin plus 5‑FU can further inhibit the Warburg phenomenon in tumor cells.

Figure 2. Ranking of Agents Targeting Glycolytic Enzymes (Warburg Effect)

Figure 3. Relative comparison on key Warburg targets of major repurposed agents

Qualitative comparison of preclinical evidence for suppressing Warburg‑related drivers

Medical Disclaimer: The discussion of repurposed medications and nutraceuticals in this article is intended to review the scientific literature and does not constitute a recommendation for self-treatment. Decisions regarding the use of off-label therapies should be made in consultation with a qualified healthcare professional familiar with the patient’s medical history and current treatment plan. Please see the full Medical Disclaimer on the introductory page to Marik’s Cancer & Metabolic Healing Playbook.

References

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2. Kumar R, Mishra A, Gautam P, Feroz Z, Vijayaraghavalu S, Likos EM, et al. Metabolic Pathways, Enzymes, and Metabolites: Opportunities in Cancer Therapy. Cancers (Basel). 2022;14(21).

3. Seyfried TN, Lee DC, Duraj T, Ta NL, Mukherjee P, Kiebish M, et al. The Warburg hypothesis and the emergence of the mitochondrial metabolic theory of cancer. J Bioenerg Biomembr. 2025;57(2-3):57–83.

4. Manikandan R, Beulaja M, Arulvasu C, Sellamuthu S, Dinesh D, Prabhu D, et al. Synergistic anticancer activity of curcumin and catechin: an in vitro study using human cancer cell lines. Microsc Res Tech. 2012;75(2):112–6.

5. Somers-Edgar TJ, Scandlyn MJ, Stuart EC, Le Nedelec MJ, Valentine SP, Rosengren RJ. The combination of epigallocatechin gallate and curcumin suppresses ER alpha-breast cancer cell growth in vitro and in vivo. Int J Cancer. 2008;122(9):1966–71.

6. Kondo A, Takeda T, Li B, Tsuiji K, Kitamura M, Wong TF, et al. Epigallocatechin-3-gallate potentiates curcumin’s ability to suppress uterine leiomyosarcoma cell growth and induce apoptosis. Int J Clin Oncol. 2013;18(3):380–8.