THE ANTIPARASITIC IVERMECTIN SYNERGIZES WITH IMMUNE CHECKPOINT INHIBITORS IN A METASTATIC COLORECTAL CANCER MODEL REFRACTORY TO IMMUNOTHERAPY

LLAVONA C; SOLERNÓ LM; SAUD ZY; GONZÁLEZ MORÁN F; SOBOL NT; MARTINEZ G; LEDESMA M; GOTTARDO MF; SEGATORI VI; ALONSO DF; GARONA J

Congreso; VI INTERNATIONAL CONGRESS IN TRANSLATIONAL MEDICINE; 2023

Immunotherapies based on immune checkpoint inhibitors (ICIs) have revolutionized the management of colorectal cancer (CCR). However, its therapeutic benefits are limited to a small subset of patients with immunoreactive and DNA mismatch repair (MMR)-deficient tumors. Considering its potential impact on immunogenic cell death (ICD) and reversal of drug resistance, antiparasitic ivermectin (IVM) has been proposed as a repurposed drug in cancer. The aim of this work was to explore the antineoplastic effect of IVM in combination with α-PD-1-based ICI, using the metastatic CT-26 model, a murine KRASmut and MMR-proficient CRC cell line refractory to immuno-chemotherapy. In vitro, CT-26 cell line showed a high sensitivity to IVM, obtaining an IC50 of 10.9 μM after a 72h-exposure. Treatment with low concentrations of IVM was associated with a reduction in tumor chemotaxis and colony-formation ability, impaired tumor cell metabolism, and increased secretion of proinflammatory/immunostimulatory molecules such as IL-2, IL-6, and TNF-α, assessed by flow cytometry and ELISA. A comprehensive proteomic analysis using mass spectrometry (MS-MS nano-HPLC Orbitrap) was conducted, revealing the effect of IVM on 1312 proteins. 25 differentially expressed proteins were found between control and IVM-treated group (17 up- and 8 down-regulated), these being involved in processes such as immune evasion, cell proliferation, and cell cycle regulation. In vivo, CT-26 cells were injected i.v. in immunocompetent BALB/c mice, and at day 7, after confirming metastatic colonization in the lung by histological studies, they were subjected to different treatments: saline vehicle, IVM (5mg/kg i.p.), α- PD-1 (10 mg/kg i.p.) and IVM + α-PD-1. Although IVM and α-PD-1 monotherapies reduced the metastatic burden by 85% and 63%, respectively, the combined therapy completely inhibited the formation of metastatic macronodules (> 2 mm) in the lung, without overt signs of toxicity. S.c. preimmunization using ex vivo-treated CT-26 cells with high cytotoxic IVM concentrations one week prior to i.v. re-challenge with viable cells led to full protection against CRC lung metastases, postulating ICD as a possible mechanism of action (p