Figure 6
From: Role of Bruton’s tyrosine kinase (BTK) in growth and metastasis of INA6 myeloma cells
Expression of CXCR4 and BTK is linked, and both genes are underexpressed in MM cells from focal lesions compared with random-site aspirates from the same patients. (a) Expression of CXCR4 and BTK was analyzed from cells of paired samples of focal lesions and random BM. Distributions of the differences for each pairwise comparison of each gene (CXCR4, P<7.58 × 10−13; BTK, P<1.58 × 10−7) are presented as box-and-whisker plots. Lower and upper edges of the boxes correspond to the first and third quartiles, respectively. The thicker bars in the middle represent the median, and the whiskers extend to the minimum and maximum values. (b) Plasma cells from random BM aspirates of patients with MM were analyzed for expression of BTK; samples were stratified according to the proportion of cells (⩽25% or >25%) with CXCR4 on their surfaces. (c) A model of intratumoral heterogeneity in myelomatous bone. Expression of BTK and CXCR4 in MM cells growing in interstitial BM is variable and is affected by interactions with matrix proteins and stromal cells. Prolonged persistence of MM cells in focal lesions results in mixed populations. BTK and CXCR4 expression impacts adherence and proliferative and metastatic behavior of these cells. BTK is essential for homing of MM cells from the circulation to the bone.
