Chokeberry (Aronia melanocarpa) fruit extract abrogates melanoma progression through boosting up IFN-γ-producing cells

[Display omitted] •Chokeberry extract (CE) delays melanoma onset and abrogates its progression in mice.•Infiltration of immune cells in the TME is increased after CE treatment.•CE treatment upregulates IFN-γ – producing immune cells in the TME.•CE treatment decreases proportion of tumor – promoting cells in the TME.•CE does not kill tumor cells, but affects immune cells to fight against melanoma. Chokeberry has exhibited cardioprotective, anti-bacterial, immunomodulating and anti-cancer properties. Chokeberry extract (CE) was tested in the model of melanoma induced by B16 cells inoculation in C57BL/6 mice. CE treatment that began 7 days before inoculation and continued through the observation period, delayed melanoma appearance and increased infiltration of immune cells in the tumor microenvironment (TME). Levels of TNF, perforin, granzyme B and IL-1β did not differ between the CE-treated and control animals, but the TME of CE-treated mice contained more IFN-γ-producing cells and a lesser frequency of CCR5-expressing MDSC. In vitro, CE displayed no direct cytotoxicity to B16 cells. However, splenocytes isolated from CE-treated animals exerted strong cytotoxic effect on B16 cells in vitro. Neutralization of IFN-γ diminished the observed B16 death, suggesting that this effect was mediated mainly by splenocyte-derived IFN-γ. In conclusion, pre-treatment with CE stimulated the anti-tumor immune response by enhancing IFN-γ-producing cells to act against melanoma.