MAPK1 and B-cell chronic lymphocytic leukemia: The analysis revealed three main groups of intracellular proteins common to all the CLL analyzed samples and directly correlated with quantitative data, and also well‐known intracellular signaling pathways: (a) B‐cell activation pathways: as receptors of the complement system, scavenger receptors, and chemokine receptors (SCAF1, RPB1 and CXCR4, respectively); (b) BCR‐associated intracellular signaling pathways: BTK, PLCy2, LYN, SYK, and ZAP70; (c) Transcription factors related to B‐cell differentiation and proliferation: p21 (CDKN1A), ERK2 (see Fig. 5 and Table S6).