Polyphyllin II inhibits thyroid cancer cell growth by simultaneously inhibiting glycolysis and oxidative phosphorylation.

Background: Thyroid cancer is the most common malignancy of the endocrine system, and effective treatments for metastatic disease are still lacking. Targeting both glycolysis and oxidative phosphorylation (OXPHOS) simultaneously represents a novel approach to cancer therapy. While polyphyllin has been shown to modulate cellular metabolism in various cancers, its role in thyroid cancer remains unexplored. Purpose: This study aimed to explore the antitumor effects and underlying mechanisms of polyphyllin in thyroid cancer. Methods: Thyroid cancer cells were treated with varying concentrations of Polyphyllin I, II, VI, and VII. Cell viability was assessed using the CCK-8 assay to identify the most effective polyphyllin compound and its optimal dosage. Colony formation and EdU incorporation assay were performed to evaluate cell proliferation, while Transwell assays were used to assess cell invasion. Cell migration ability was examined using the wound healing assay. The effect of Polyphyllin II on OXPHOS was evaluated using an extracellular oxygen consumption rate (OCR) assay kit. Glucose uptake, lactate production, glycolysis-related protein expression, and the extracellular acidification rate (ECAR) were measured to assess the effects of Polyphyllin II on glycolysis in thyroid cancer cells. Flow cytometry and western blotting were conducted to detect apoptosis. Results: Polyphyllin I, II, VI, and VII all inhibit the proliferation of thyroid cancer cells, with Polyphyllin II showing the most potent inhibitory effect. Polyphyllin II suppresses cell proliferation, invasion, and migration of thyroid cancer cells, while also promoting apoptosis. Mechanism studies reveal that Polyphyllin II inhibits extracellular OCR, basal respiration, maximum respiration, ATP-linked respiration, spare respiration capacity, glucose uptake, lactate production, glycolytic rate-limiting enzymes, and the ECAR in thyroid cancer cells. Conclusion: Polyphyllin II simultaneously inhibits glycolysis and OXPHOS, thereby suppressing the invasion, migration, and proliferation of thyroid cancer cells, while also promoting apoptosis.