Fungal immunomodulatory proteins skew macrophages towards a pro-inflammatory and tumour inhibitory phenotype

BACKGROUND: Tumour-associated macrophages (TAMs) are associated with poor clinical outcome in cancer patients, making them key targets in immunotherapy. TAMs mainly consist of anti-inflammatory M2 macrophages promoting tumour growth, metastasis and immunosuppression. Fungal immunomodulatory protein from Nectria haematococca (FIP-nha) is a potential anti-tumour agent, notably inhibiting tumour cells and exerting immunomodulatory activity on macrophages. However, the anti-tumour activity of FIP-nha via TAMs modulation is still unclear. Here, the immunomodulatory activity of rFIP-nha on M1 and M2 macrophages was explored, as well as its anti-tumour activity via macrophage modulation, using M2 macrophages as TAM representatives, through an intricate co-culture design with A549 lung cancer cells. METHODS: THP-1-monocyte derived M2 macrophages were treated with rFIP-nha and analysed phenotypically. Subsequently, rFIP-nha treated M2 macrophages were co-cultured with A549 cells to investigate anti-tumour activity via macrophage modulation. RESULTS: rFIP-nha exposure decreased macrophages phagocytosis activity, enhanced IL-1β, IL-12 and IL-10 cytokine secretion, and modulated specific cell surface markers for M2 (CD163 and CD206) towards those that are typical for M1 (CD68 and CD80) polarization. rFIP-nha treated M2 macrophages polarized towards a tumour inhibitory phenotype which, when co-cultured with A549 cells, resulted in greater reduction of tumour cell proliferation compared to A549 cells co-cultured with M2 or M1 macrophages. Moreover, rFIP-nha exacerbated tumour inhibition and cell death. CONCLUSION: rFIP-nha inhibited tumour growth in two distinct ways, by targeting tumour cells directly and by directing macrophage polarization towards a tumour inhibitory phenotype. This dual bioactivity makes FIP-nha interesting as an additive support in cancer immunotherapy.