The B-cell receptor controls fitness of MYC-driven lymphoma cells via GSK3β inhibition

Item Type:	Article
Title:	The B-cell receptor controls fitness of MYC-driven lymphoma cells via GSK3β inhibition
Creators Name:	Varano, G. and Raffel, S. and Sormani, M. and Zanardi, F. and Lonardi, S. and Zasada, C. and Perucho, L. and Petrocelli, V. and Haake, A. and Lee, A.K. and Bugatti, M. and Paul, U. and Van Anken, E. and Pasqualucci, L. and Rabadan, R. and Siebert, R. and Kempa, S. and Ponzoni, M. and Facchetti, F. and Rajewsky, K. and Casola, S.
Abstract:	Similar to resting mature B cells, where the B-cell antigen receptor (BCR) controls cellular survival, surface BCR expression is conserved in most mature B-cell lymphomas. The identification of activating BCR mutations and the growth disadvantage upon BCR knockdown of cells of certain lymphoma entities has led to the view that BCR signalling is required for tumour cell survival. Consequently, the BCR signalling machinery has become an established target in the therapy of B-cell malignancies. Here we study the effects of BCR ablation on MYC-driven mouse B-cell lymphomas and compare them with observations in human Burkitt lymphoma. Whereas BCR ablation does not, per se, significantly affect lymphoma growth, BCR-negative (BCR(-)) tumour cells rapidly disappear in the presence of their BCR-expressing (BCR(+)) counterparts in vitro and in vivo. This requires neither cellular contact nor factors released by BCR(+) tumour cells. Instead, BCR loss induces the rewiring of central carbon metabolism, increasing the sensitivity of receptor-less lymphoma cells to nutrient restriction. The BCR attenuates glycogen synthase kinase 3 beta (GSK3β) activity to support MYC-controlled gene expression. BCR(-) tumour cells exhibit increased GSK3β activity and are rescued from their competitive growth disadvantage by GSK3β inhibition. BCR(-) lymphoma variants that restore competitive fitness normalize GSK3β activity after constitutive activation of the MAPK pathway, commonly through Ras mutations. Similarly, in Burkitt lymphoma, activating RAS mutations may propagate immunoglobulin-crippled tumour cells, which usually represent a minority of the tumour bulk. Thus, while BCR expression enhances lymphoma cell fitness, BCR-targeted therapies may profit from combinations with drugs targeting BCR(-) tumour cells.
Keywords:	B-Lymphocytes, Burkitt Lymphoma, Carbon, Gene Expression Regulation, Neoplastic, Genes, myc, Genes, ras, Genetic Fitness, Glycogen Synthase Kinase 3 Beta, Lymphoma, MAP Kinase Signaling System, Mutation, Receptors, Antigen, B-Cell, Tumor Cells, Cultured, Animals, Mice
Source:	Nature
ISSN:	0028-0836
Publisher:	Nature Publishing Group
Volume:	546
Number:	7657
Page Range:	302-306
Date:	8 June 2017
Official Publication:	https://doi.org/10.1038/nature22353
PubMed:	View item in PubMed

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