Recombinant Methioninase (rMETase) Synergistically Sensitizes Ivermectin-resistant MCF-7 Breast Cancer Cells 9.9 Fold to Low-dose Ivermectin.

Background/aim: Ivermectin is a widely-used anti-parasitic agent and has shown early promise as an anticancer agent. Recombinant methioninase (rMETase) is a methionine-depleting enzyme targeting the methionine addiction of cancer and has broad efficacy against all tested cancer types. However, the combination efficacy of ivermectin and rMETase on breast cancer cells remains unexplored. The present study aimed to determine the synergistic efficacy of ivermectin and rMETase on MCF-7 human breast cancer cells in vitro.

Materials and methods: The IC₁₀ of ivermectin and IC₅₀ of rMETase were determined on MCF-7 cells using the WST-8 reagent to measure cell viability in vitro. MCF-7 cells were treated with four groups: untreated control; ivermectin alone (4.89 μM, IC₁₀); rMETase alone (2.75 U/ml, IC₅₀); and a combination of ivermectin (4.89 μM) and rMETase (2.75 U/ml). Cell viability was assessed 72 hours after treatment with the WST-8 reagent.

Results: Treatment with ivermectin (4.89 μM) did not significantly reduce the viability of MCF-7 cells. rMETase (2.75 U/ml) alone significantly reduced MCF-7 cell viability compared to the control group. The combination of ivermectin and rMETase resulted in a significantly greater reduction in cell viability than either agent alone, including a 9.9-fold greater efficacy than ivermectin alone, demonstrating synergistic efficacy (p<0.05).

Conclusion: The combination of ivermectin and rMETase had synergistic efficacy against MCF-7 breast cancer cells in vitro. The present findings suggest that the combination of ivermectin and rMETase is a promising strategy for breast cancer requiring further preclinical and clinical evaluation.