Inducing anti-tumor cytokines and an immune response in melanoma by inhibition of MIA using the peptide AR71.

Background: Malignant melanoma is known for its aggressive metastatic spread and suppression of the host immune system. Immunosuppression in melanoma is mediated in part by the protein melanoma inhibitory activity (MIA).

Objectives: In this study, we assessed the in vitro and in vivo efficacy of the MIA-inhibitory peptide AR71 in the inhibition of MIA-induced immunosuppression. This follows a previous study that revealed an increase in CD3-positive cells and cleaved caspase-3 in an in vivo model of hepatic metastasis after MIA inhibition.

Materials And Methods: We used Multiplex-ELISAs and qRT-PCR for determining changes in cytokine expression in vitro and in vivo and calcein release assays for determining immune cell response in vitro.

Results: By evaluating the serum levels of tumor-associated cytokines of the melanoma-bearing mice, we found beneficial decreases of several cytokines, including TNF-alpha, after AR71 treatment. Additionally, we demonstrated an increase of anti-tumor lymphokine-activated killer (LAK) cell cytotoxicity in the presence of the MIA inhibitor AR71. Stimulation of anti-tumor immune responses by AR71 could be observed via increased numbers of NK cells in the metastases-bearing murine livers in vivo.

Conclusion: In summary, inhibition of MIA activity results in reduced immunosuppression in vitro and in vivo.