Eucalyptus camaldulensis leaf extract enhances thalidomide efficacy in acute myeloid leukemia cells through modulation of mitochondrial energetics

Abstract

BACKGROUND: Acute myeloid leukemia (AML) is an aggressive hematological malignancy characterized by high relapse rates and poor prognosis. Leukemic stem cells (LSCs), a major driver of therapy resistance, rely predominantly on mitochondrial oxidative phosphorylation (OXPHOS) for survival. Targeting mitochondrial metabolism represents a promising therapeutic strategy. This study investigated the effect of Eucalyptus camaldulensis Dehnh. leaf extract, alone and in combination with thalidomide, on mitochondrial energetics in AML cells. METHODS: An in vitro study was conducted using the human AML Kasumi-1 cell line. Cells were divided into four groups: control, thalidomide-treated, E. camaldulensis extract-treated, and combination-treated groups. The ethanolic extract was characterized by GC-MS and HPLC. Cell viability was assessed using WST-1 assay and IC₅₀ values were calculated. Gene expression of CD34, MFN1, MFN2, OPA1, and IL-6 was quantified by qRT-PCR. ATP levels were measured by ELISA. Mitochondrial length was assessed by transmission electron microscopy. RESULTS: E. camaldulensis extract significantly reduced Kasumi-1 cell viability in a concentration-dependent manner, both alone and in combination with thalidomide. The combination demonstrated an additive cytotoxic effect (CI = 1). The IC₅₀ values were 197.80 µg/mL for thalidomide, 30.26 µg/mL for the extract, and 28.26 µg/mL for the combination. Thalidomide alone or combined significantly downregulated IL-6 expression, while thalidomide increased MFN1 expression. The extract significantly downregulated IL-6 and mitochondrial fusion genes and reduced CD34 expression. Extract treatment decreased ATP levels and shortened mitochondrial length compared with untreated cells (p < 0.05). CONCLUSION: Eucalyptus camaldulensis extract disrupts mitochondrial energetics and LSC-associated pathways in AML cells. Its combination with thalidomide shows additive activity and may represent a complementary strategy to overcome metabolic-driven therapy resistance in AML.