Höfundar:
Teitur Sævarsson, Berglind Einarsdóttir
Introduction
Cutaneous melanoma tumors can only form if they evade immune surveillance. During immune evasion, melanoma cells change their phenotype to become impervious to the host’s immune response. Melanoma biology is largely dictated by the Microthalmia-associated transcription factor (MITF), but its role in immune evasion remains poorly defined. Preliminary data from our lab suggests MITF might affect the expression of immunosuppressive factors in human melanoma cells stimulated with IFN-γ. We aim to characterize the molecular mechanism and biological impact of this effect.
Methods
MITF expression of the human melanoma cell line 624Mel was knocked down via siRNA transfection, and cells were subsequently stimulated with IFN-γ. Expression of PD-L1 and IDO1 was analyzed on the mRNA level via qPCR, and PD-L1 protein expression was analyzed via FACS. Exosome-bound PD-L1 was analyzed via ELISA, and a panel of 18 immune modulatory cytokines was analyzed via Luminex.
Results
PD-L1 expression was significantly increased on both mRNA and protein level in MITF low 624Mel cells following IFN-γ stimulation. Similarly, IDO expression was significantly increased on the mRNA level. There was significantly increased secretion of CCL2, CXCL10, and IL-10 in MITF low cells stimulated with IFN-γ, whilst significantly increased secretion of IL-8 and CXCL11 was noted in MITF low cells w/o IFN-γ stimulation. PD-L1 was not detected on exosomes derived from 624Mel cells.
Conclusions
MITF low melanoma cells appear capable of increased expression of known immunosuppressive factors, indicating the potential immune evasive capabilities of melanoma cells.