Immunotherapy has transformed treatment of patients with advanced metastatic melanoma. Efficacy of immunotherapy is dependent on the interaction of tumour cells with immune cells, and may be mediated by cytokines. Two cytokines, IFNγ and TNFα, are expressed by cytotoxic T cells in the tumour microenvironment, but their effects on melanoma cells are not clear.
In this study, we assessed the impact of IFNγ and TNFα on the expression of various melanoma-associated immune regulatory factors and on melanoma cell cycle. We also examined the influence of melanoma genotype on melanoma response to IFNγ and TNFα.
Melanoma cells comprising three distinct genotypes, 1) BRAF mutant, 2) NRAS mutant, and 3) BRAF and NRAS wild type, were treated for 72h with TNFα, IFNγ or 0.1% BSA (as control). Cells were analysed for cell cycle progression and membrane expression of immune regulators including the nerve growth factor receptor (NGFR), PD-L1, PD-L2, HLA-ABC and HLA-DR by flow cytometry.
We observed that IFNγ and TNFα induced differential expression of markers on melanoma cells. IFNγ showed stronger induction of PD-L1, PD-L2, HLA-ABC and HLA-DR compared to TNFα. Moreover, comparison between NRAS and BRAF mutant cells revealed that IFNγ induced higher expression of PD-L2 in the BRAF-mutant cells.
Cell cycle analysis showed more cell death in BRAF-mutant cells in response to IFNγ compared to TNFα treatment.
We are currently expanding our investigation to include more melanoma cells in order to establish a link between melanoma genotype and response to IFNγ and TNFα.