A Novel Ruthenium(II) Complex and its Synergistic Anti-Leukemia Activity with GidA Protein via Dual-Pathway Apoptosis

This study demonstrates the effective anticancer activity of a semi-synthetic complex integrating the GidA protein and the ruthenium(II) complex against K562 human leukemia cells. Monotherapy evaluation revealed exceptional cytotoxicity, with half-maximal inhibitory concentration values of 0.058 μg/mL for GidA (a novel topoisomerase II inhibitor) and 14.1 μg/mL for Ru(II). Subsequently, isobologram analysis of six combination ratios identified profound synergy in formulations with elevated Ru(II) concentrations (combinations 4 and 5; sum of the fractional inhibitory concentration=0.17-0.86). All these synergistic complexes induced up to 73.91% apoptosis, exceeding single-agent efficacy (p<0.01), while minimizing necrosis (<20%). Besides, mechanistic studies revealed dual pathways: Ru(II) triggered reactive oxygen species-dependent apoptosis (2.8-fold reactive oxygen species surge at 30 min; p<0.01), while GidA operated via reactive oxygen species-independent mechanisms. This semi-synthetic complex may involve Ru(II), potentially mediated by transferrin receptor overexpression for targeted uptake. Also, combination 5 (4×Ru(II):1×GidA) emerged as the lead candidate, reducing effective doses and potentially mitigating resistance. Overall, these findings establish GidA-Ru(II) complexes as first-in-class dual-mechanism agents with high translational potential for refractory leukemia, offering a strategic solution to chemotherapy limitations through rational synergy.