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

[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 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 (1×10 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 (IC) values. To evaluate synergy, cells were treated with each drug alone or double or triple combinations at their respective IC 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 IC 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 IC 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 IC 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.