Metabolic Reprogramming of Mesenchymal Stem Cells upon Co-Cultivation with Primary CLL Cells Determined By Mass Spectrometry-Based Proteomics

Chronic lyhocytic leukemia displays a strong dependency on tumor-stroma interactions. CLL cells were found to rapidly die when cultivated in vitro, whereas co-cultivation with mesenchymal stromal cells promotes cell proliferation and ensures leukemia cell survival. It is therefore of great interest to obtain a thourough picture of the exact molecular players involved in this critical interplay. While a number of protagonists are already well described, there are still unresoved issues concerning the effect of stromal cells on the metabolism of CLL cells.

In this study we co-cultivated for one week primary CLL cells obtained from peripheral blood with mesenchymal cells (hMSC). Subsequently, hMSC were lysed and fractionated to obtain cytoplamic, nuclear and secreted proteins. To allow comparative analyses, B-cells from healthy individuals and hMSC were co-cultivated.

Mass spectrometry-based proteomic analysis resulted in the identification and relative quantification of more than 3700 proteins. Comparative analyses between co-cultures with CLL and healthy B-cells showed that already at a ratio of 0.25% CLL cells could induce a significant proteomic alteration in hMSC. Furthermore, hMSC were found to undergo a metabolic change upon co-cultivation with CLL cells, an effect which was most pronounced in the secreted protein fraction. Annotation analyses according to gene ontology revealed that proteins related to "generation of precursor metaboites" were significantly up-regulated in hMSC upon co-culture with CLL cells. This indicated that these stromal cells "feed" the leukemia cells by producing and secreting high energy metabolite, satisfying the elevated metabolic demands of the CLL cells.

Revealing the metabolic interactions between CLL cells and surrounding stromal cells by mass spetrometry-based methods should contribute to the development of innovative treatment strategies.