Triple Combination of Recombinant Methioninase and the Anti-parasitic Drugs Ivermectin, and Chloroquine Selectively Eradicates Pancreatic Cancer Cells While Sparing Normal Fibroblasts

Abstract

Background/aim: Pancreatic cancer is a recalcitrant disease which often presents with few symptoms in the early stages and is frequently diagnosed with distant metastases, limiting treatment options and resulting in a poor prognosis. Recombinant methioninase (rMETase), which targets cancer-specific methionine addiction, has shown synergistic efficacy with numerous types of chemotherapy against all major cancer types. Ivermectin and chloroquine, anti-parasitic drugs, are showing promise against cancer. The present study investigates in vitro the potential synergy of rMETase combined with ivermectin and chloroquine, two agents with multiple anticancer mechanisms, as a novel treatment strategy for metastatic pancreatic cancer.

Materials and methods: The human pancreatic-cancer cell line MiaPaCa-2 and normal human fibroblasts Hs27 were cultured in 96-well plates (1×10³ cells/well) for 24 h. Cell viability was assessed using the WST-8 reagent following 72-h treatment with rMETase, ivermectin, or chloroquine to determine their 30% inhibitory concentration (IC₃₀) values. To evaluate synergy, cells were treated with each drug alone or double or triple combinations at their respective IC₃₀ concentrations. Additionally, to evaluate the optimal order of the combination therapy, MiaPaCa-2 cells were divided into four groups and sequentially treated for 72 h as follows: (1) untreated control; (2) the triple-drug combination therapy alone; (3) rMETase followed by the triple-drug combination therapy; (4) the triple-drug combination therapy followed by rMETase.

Results: The IC₃₀ value of rMETase was 0.39 U/ml, ivermectin was 4.41 μM, and chloroquine was 3.29 μM on MiaPaCa-2 cells. The triple combination of these agents at their IC₃₀ concentrations significantly inhibited MiaPaCa-2 cell growth compared to monotherapies or dual combinations, indicating a synergistic efficacy. In contrast, the same combination had minimal impact on Hs27 cells at the IC₃₀ values determined for MiaPaCa-2. Regarding the treatment sequence, triple-drug combination therapy and triple-drug combination treatment followed by rMETase treatment significantly inhibited cell proliferation more than rMETase followed by the triple-drug combination treatment.

Conclusion: The combination of rMETase, ivermectin, and chloroquine exhibited a selective cytotoxic synergy against pancreatic-cancer cells while sparing normal fibroblasts. Furthermore, the order of treatment may also affect efficacy. This triple combination treatment may offer a novel and effective first-line therapeutic approach for pancreatic cancer.

Keywords: Hoffman effect; Recombinant methioninase (rMETase); chloroquine; combination treatment; ivermectin; methionine addiction; normal fibroblasts; pancreatic cancer; synergy.