Tumour signalling and progression is strongly dependent on the tumour microenvironment, comprising components like extracellular matrix, surrounding stromal cells and signalling molecules including secreted proteins. However, little is known whether extracellular amino acids correlate with specific growth behaviour of defined melanoma cell lines. It was the aim of this study to identify components of a possible cross talk between slow and fast-growing melanoma cells.
We have investigated the amino acid composition as well as acetate and pyruvate of the secretome of human melanoma cells representing early slow growth phase (WM35, WM278, WM793b and VM21) and rapid growth phase of metastatic cells (A375, 518a2, 6F and WM8). Subsequently, amino acid profiles were evaluated by multivariate data analysis, i.e. principle component analysis and partial least squares regression. Significant changes in the amino acid composition of media were analysed for biological significance with proliferation, migration and invasion assays.
Proliferation assays and a principle component analysis revealed a stringent difference between the fast and slow growing melanoma cells. Upon inhibition of the mevalonate pathway, glutamic acid and alanine were identified as the central difference in the conditional media. Supplementing media with glutamic acid and the combination with alanine significantly accelerated the proliferation, migration and invasion of early stage melanoma cells, but not metastatic cells. Interestingly, co-culture of early stage and metastatic melanoma cells further corroborate these findings, indicating cross talk between tumour cells.
Our results confirm for the first time that amino acid profiles from conditional media differ between stage dependent growth and treatment. Hence, changes in amino acid composition of media from melanoma cells derived from different disease states reflect a stage dependent adaptation with functional consequences on proliferation, migration, aggressiveness and survival. Thus, identification of glutamic acid mediated signalling may open pharmacological targeting in early melanoma stages.
Clinical trial identification
Legal entity responsible for the study
Work was funded by the Austrian Science Fund FWF (P-22385), Herzfeldeŕsche Familienstiftung and the Science Funds of the Major of the City of Vienna, all to Martin Hohenegger. Alexandra Hofer was funded the Austrian research funding association (FFG) under the scope of the COMET program within the research project “Industrial Methods for Process Analytical Chemistry - From Measurement Technologies to Information Systems (imPACts)” (contract # 843546).
All authors have declared no conflicts of interest.