An in vitro Model for Immunomodulation in Melanoma


PA 361/22-1 (2015-2017)


The tumour microenvironment is characterised by inflammation, hypoxia and acidic pH. These features in turn contribute to immunosuppression and to the metastatic potential of tumour cells. A major mechanism of tumour-induced immune suppression is through the differentiation of Myeloid Derived Suppressor Cells (MDSCs), levels of which have been shown to relate to duration of survival of late-stage melanoma patients. Acidic pH, hypoxia and inflammatory cytokines play important roles in the differentiation of myeloid cells to suppressive MDSCs, but at present only a rudimentary understanding of these mechanisms exists. This project will investigate the role of pH regulatory proteins and heat shock proteins (hsps) on the differentiation and effector function of MDSCs. These two groups of proteins play crucial roles in the maintenance of numerous metabolic processes required by cancer cells generally, but also those involved in the differentiation of MDSCs. Despite the aforementioned features of the tumour microenvironment, the culture of tumour cell lines is conventionally performed under atmospheric oxygen and in medium with a neutral pH, which does not accurately reflect the conditions found in vivo.

This study will employ a wholly human experimental culture model consisting of reduced oxygen tension, acidic pH and fibroblast stromal cells. In this model, long-term established and early-passage melanoma cell lines will be tested with MDSC precursors derived from healthy individuals and melanoma patients. Comparing the results from this experimental model with those produced from conventional cell culture, the metastatic potential (stem-like phenotype, 3D culture models) of tumour cell lines and their ability to induce MDSC differentiation will be tested. MDSCs will be tested for their suppressive activity and the mechanisms of differentiation and suppression. The effect of inhibiting hsps and pH regulatory proteins will be tested in both culture models. The results of this study will: reveal the role of hsps and pH regulatory proteins in melanoma-mediated immune suppression; uncover the influence of tumour microenvironmental features on the aforementioned immune suppression, and contribute to the development of better in vitro culture models. This study is intended to uncover plausible novel drug targets in the treatment of cancer.