PO-440 Development and characterisation of pre-clinical in vitro/in vivo models from disseminated tumour cells of melanoma patients

Abstract

IntroductionWe recently showed that dissemination of few melanoma cells to the lymph nodes is a quantitative risk factor for death from melanoma. However, the analysis of disseminated tumour cells (DTC) is limited by their extremely low frequency, resulting in a lack of in vitro/in vivo models for mechanistic studies of early systemic disease. Therefore, the objective of this study was to develop protocols to expand single DTC from lymph nodes of melanoma patients to establish better preclinical models for adjuvant cancer therapies.Material and methodsSentinel lymph nodes from melanoma patients were cut in halves, disaggregated and analysed for the presence of gp100-positive DTC. The other half was used for diagnostic assessment by histopathology. Single DTC within the lymph node-derived single cell suspension were then propagated under specific sphere forming conditions and expanded by transplantation in immunodeficient mice. DTC based pre-clinical in vitro/in vivo models were then characterised on molecular level and were used for functional analyses. To test drugs on DTC in presence of a human immune system we additionally generated humanised xenograft models.Results and discussionsWe successfully established cell lines and xenografts from DTCs of 17 melanoma patients. We confirmed the origin of the cells by genomic fingerprint and analysed the genomic profile of the expanded cells over various culture and animal passages. DTC cell lines were used for functional analysis and for testing the efficacy of targeted therapies. In addition, we set up a novel preclinical mouse model based on expanded melanoma DTC. For this, we established a human immune system in immunodeficient mice, which were then transplanted with melanoma DTC-derived cells. Interestingly, the presence of a human immune system significantly induced tumour formation, as well as dissemination of melanoma cells and improved the response to a targeted therapy compared to mice without a humanised immune system.ConclusionThe development of DTC based pre-clinical in vitro/in vivo models enables mechanistic studies on DTCs and drug tests against the target cells of adjuvant therapies in the presence of human immune cells. These models may help to identify candidate adjuvant therapies targeting DTCs and to understand mechanisms of drug resistance of currently applied targeted therapies.