Proliferation Inhibited by Genipin in Human Leukemia K562 Cells: Involvement of Uncoupling Protein 2 in Mitochondrial Damage.

Background: Uncoupling protein 2 (UCP2) is essential for maintaining redox homeostasis and regulating energy metabolism. Abnormal expression of UCP2 has been associated with various tumors, including leukemia. Genipin (GEN), a specific inhibitor of UCP2, has a long history of use in traditional Chinese medicine. However, the precise role and underlying mechanisms of UCP2 in the inhibition of leukemia cells by GEN remain inadequately understood. This study focuses on the expression levels of UCP2 in myeloid leukemia (ML) and investigates the effects of GEN on the proliferation, mitochondrial function, and energy metabolism of the chronic myeloid leukemia (CML) cell line K562.

Methods: The expression of UCP2 in clinical samples and cell lines (HL-60, U937, and K562) was confirmed using real-time quantitative polymerase chain reaction (qPCR) and western blot. The effects of GEN on K562 cell viability, morphology, and apoptosis were assessed through a cell counting kit-8 (CCK-8), Wright-Giemsa staining, and an annexin V-fluorescein isothiocyanate/propidium iodide (FITC/PI) apoptosis detection kit. Additionally, the impact of GEN on mitochondrial function and energy metabolism, including reactive oxygen species (ROS), mitochondrial membrane permeability transition pore (MPTP), lactic acid (LA), oxygen consumption rate (OCR), and adenosine triphosphate (ATP) levels in K562 cells, was also examined.

Results: The results showed that UCP2 was differentially expressed in clinical samples from patients with ML. Among the three cell lines examined, K562 cells exhibited a significantly higher expression level of UCP2. Functionally, GEN markedly inhibited K562 cell viability while promoting K562 cell differentiation and apoptosis. Mechanistically, UCP2 mRNA and protein expression levels were inhibited by GEN in K562 cells in a concentration- and time-dependent manner. Additionally, GEN dramatically increased ROS generation and induced mitochondrial MPTP opening in K562 cells. Furthermore, GEN significantly reduced LA production in K562 cells and markedly increased OCR and ATP production.

Conclusion: The results suggest that UCP2 is differentially expressed in ML patients and cell lines; GEN, a UCP2 inhibitor, induces mitochondrial damage and metabolic remodeling, thereby inhibiting proliferation and promoting apoptosis in K562 cells, and thus could be suggested as an adjuvant of an antitumor metabolic therapy.