Fig. 1.

Identification of CRLF2 in B-ALL. (A) Tumor-derived cDNA is packaged into retroviral particles that are used to infect BaF3 cells. Integrants (gray) survive in puromycin selection. Surviving clones (black) are isolated after IL3 withdrawal and their integrated cDNAs are sequenced and repackaged within retrovirus and confirmed. (B) IHC using anti-CRLF2 antibody and interphase FISH. ALL-73 has no detectable CRLF2 expression by IHC, whereas both ALL-74 and ALL-76 have visible expression and surface localization. (Left) FISH demonstrates 2 fusions of the CRLF2 (yellow) and IGH (green) probes in ALL-74, consistent with a reciprocal translocation, but not in ALL-73. (Right) FISH shows one probe centromeric to CRLF2 (yellow) lost in ALL-76, consistent with an intrachromosomal deletion.