Mimicking the tumour microenvironment of chronic lymphocytic leukaemia in vitro critically depends on the type of B-cell receptor stimulation.

Background: The B-cell receptor (BCR) has a key role in the cross-talk between chronic lymphocytic leukaemia (CLL) cells and the tissue microenvironment, which favours disease progression by promoting proliferation and drug resistance. In vitro studies on downstream signalling and functional effects of CLL BCR ligation often report contradictory results, in part owing to the lack of a standardised stimulation protocol. Our aim was to define a biologically relevant and robust in vitro stimulation method with regard to cellular phenotypic and transcriptional responses.

Methods: We evaluated mRNA (FOS, MYC, LPL) and protein (CD54, CD19, CD62L, CD184) expression of genes modulated by BCR triggering in immunoglobulin heavy-chain variable region genes (IGHV)-mutated and -unmutated CLL cells, after stimulation using soluble or immobilised anti-IgM antibodies from different suppliers.

Results: The effect of BCR stimulation on gene and protein expression was comparable in all CLL patients, irrespective of IGHV mutation status. However, immobilised anti-IgM stimulation elicited clear and robust changes in gene and protein expression, whereas the response to soluble anti-IgM was far less obvious.

Conclusions: These data indicate that the method of BCR stimulation is of major importance regarding responsiveness of CLL cells in the context of the tumour microenvironment, whereas genetic differences in the BCR pathway are less critical.