Endocrine Abstracts

Solid tumours are very complex tissues comprising not only cancer cells, but also non-malignant stromal cells such as endothelial cells, fibroblasts, immune cells and extracellular matrix, forming the so called tumour microenvironment. In the last few years, it has become more and more evident the pivotal role of the tumour microenvironment in modulating cancer progression and metastasis. Tumour microenvironment has thus become a potential therapeutic target. To obtain an experimental model resembling the in vivo conditions of the succinate dehydrogenase B subunit (SDHB)-mutated paragangliomas (PGL), we evaluated the effects of SDHB silencing on metabolism and proliferation in the human neuroblastoma cell line (SK-N-AS), cultured alone or in association with human fibroblasts. Silencing, verified by Western Blot and densitometry analysis, caused a 70% decrease in protein expression, an almost complete loss of the complex specific enzymatic activity and a significant increase in HIF1α and HIF2α expression, thus resembling the in vivo tumor cell phenotype. When compared to wild type SK-N-AS cells, SDHB silenced cells showed an altered metabolism characterised by an unexpected significant decrease in glucose uptake and by an increase of lactate uptake. Moreover, silenced cells showed a significant increase in cell proliferation and metalloproteinase activity. When co-cultured with human fibroblasts, control cells showed a significant decrease in glucose uptake and a significant increase in cell proliferation vs their mono-cultured counterparts. These effects were even more strikingly evident in co-cultured silenced cells which showed a 70% decrease in glucose uptake and a 92% increase in cell proliferation vs their mono-cultured counterparts. Our data demonstrate, for the first time, that SDHB impairment causes a metabolic and functional derangement of neural crest-derived tumour cells and that microenvironment, here represented by fibroblasts, strongly affects their tumour metabolism and growth capacity.

Disclosure: Fondazione Cassa di Risparmio di Pistoia e Pescia (Prot. 2013.0375).

Ente Cassa di Risparmio di Firenze research fellowship (Prot.2013.0503).