BTK and mantle cell lymphoma: To functionally characterize the BCR signaling in MCL, the phosphorylation status of nine proteins downstream of the BCR signaling, namely SYK, LCK, BTK, PLCγ2, p38, ERK1/2, AKT, NF-κB p65 and STAT5, were analyzed at the single-cell level in PBMC samples collected from 30 MCL patients at diagnosis or prior to therapy (Table S1) using phospho-specific flow cytometry combined with fluorescent cell barcoding (Figure S1).