Expression of RTKs in ALL and normal lymphopoiesis. (A) Heat map of mean quantitative RTK protein expression data on n = 106 ALL samples representing different immunological and genetic ALL subtypes determined by quantitative sandwich ELISA performed in duplicate. Color scale bar indicates amount of RTK protein (femtogram) per microgram protein lysate using recombinant proteins as internal standards. (B) RTK surface expression in hematopoietic progenitor cells from bone marrow of ALL patients in complete remission determined by FACS of progenitor subpopulations in comparison with primary ALL samples (denoted as ALL). Pro-B and pre-B progenitors as defined in supplemental Figure 1D. Color scale indicates receptor surface expression as percentage of total cell population. cALL, common ALL; CLP, common lymphoid progenitor; HSC, hematopoietic stem cell.