Patterns of genomic P2RY8-CRLF2 and CRLF2 transcripts of fusion-positive ALL relapse cases. The 6 different patterns of clonal relation between initial diagnosis (D) and relapse (R) leukemia are depicted. (A) Genomic PCR products for P2RY8-CRLF2 in representative cases. Sample identification is indicated at the top of the figure: ad, nontemplate control; pB, peripheral blood MNCs; and SM, size marker. Cases 1, 3, and 737 harbor the fusion in a major clone at initial diagnosis, and it was either conserved (1), lost (3), or reduced to a minor subclone (737) at relapse. In cases 810, 564, and 243 with a fusion-positive minor subclone at initial diagnosis, the fusion was also either lost (810), preserved (243), or replaced by a different fusion (564) at relapse. Quantification of the genomic P2RY8-CRLF2 fusion (indicated in percentage of leukemia cells at the y-axis; B) and the corresponding CRLF2 transcript levels (fold changes of normalized expression of the samples over the expression in peripheral blood MNCs; C). Sample identification is given at the bottom of the graph.