Abstract 4180: Rewiring the cytokine network in melanoma

Abstract

Malignant melanoma is one of the most aggressive types of malignancies in humans resulting in 50,000 deaths worldwide annually. Fortuitously, malignant melanoma is highly immunogenic and it is now well established that the host immune system can detect and kill melanoma. T helper type-1 lymphocytes (TH1) play a pivotal role in inducing and maintaining anti-tumour immune responses. In melanoma patients, it has been observed that higher number of TH1 cells in the tumour micro-environment lead to better prognosis. In this study, using an autochthonous zebrafish melanoma model, when we forced the expression of interferon gamma (IFNg) locally in the tumour microenvironment, thereby potentially enhancing TH1 differentiation, we observed an inflammatory response against melanoma that eventually lead to complete tumour regression. Using transposon mediated BAC transgenesis, we have generated a Tg(cd4:mcherry) reporter line labelling CD4+ cells in zebrafish. By driving Human NRASQ61L in zebrafish melanocytes we have modelled melanoma in zebrafish and later when these fish developed tumours we forced the expression of IFNg in melanoma cells using a tamoxifen inducible LSL/CreERT2 system driven by mitfa minimal promoter. Experiments were performed using animals with and without CreERT2. Following tamoxifen administration, we observed a loss of pigmentation in all the IFNg induced tumours (n = 12) by 2 weeks post induction which gradually increased over the study period. Whereas no loss of pigmentation was observed in control tumours (n = 12) throughout the study period. At 9 weeks post induction, the study was terminated and tumours were analysed using histology. In tumours were IFNg was induced, we observed that the tumour tissue was now replaced with fibrotic tissue accompanied by a marked lymphocyte infiltration and patches of necrosis. However, new tumour nodules were also observed to develop in the vicinity of regressing nodules which are unpigmented and potentially hypo-immunogenic. We observed no signs of tumour regression in control tumours. Although preliminary, our data is very exciting and promising as it will open new avenues for developing combinatorial therapies in melanoma. Using a high throughput in-vivo model system such as zebrafish, it is an exciting proposition to test the impact of combining anti-PD1/PDL1 inhibitors with various cytokines/chemokines in inducing effective and sustained tumour regression in melanoma. Citation Format: Raghavendar Nagaraju, Christopher Dee, Helen Young, Jorge Barriuso, Christopher Secombes, Adam Hurlstone. Rewiring the cytokine network in melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4180.