Identification of putative pathogenic microRNA and its downstream targets in anaplastic lymphoma kinase–negative anaplastic large cell lymphoma

Anaplastic large cell lymphomas (ALCL) are tumors of T/null-cell lineage characterized by uniform CD30 expression. The 2008 World Health Organization classification subdivided ALCLs into 2 groups: anaplastic lymphoma kinase (ALK)-positive (established entity) and ALK-negative (proposed new entity) ALCL. The genetic basis for the pathogenesis of newly categorized ALK- ALCL is poorly understood. In this study, we used microRNA microarray analysis to identify differentially expressed microRNAs in ALK+ and ALK- ALCL. ALK- ALCL showed significantly higher expression of miR-155 (0.888 ± 0.228) compared with ALK+ ALCL (0.0565 ± 0.009) on microarray and by quantitative real-time polymerase chain reaction in ALK- ALCL compared with ALK+ ALCL (P < .05) with a strong correlation between the 2 platforms (R = 0.9, P < .0003). A novel in situ hybridization method allows direct visualization of expression patterns and relative quantitation of miR-155 (mean score, 2.3 versus 1.3; P = .01) for the first time in tissue sections of ALCL. Among computationally predicted targets of miR-155, we identified ZNF652 (r = -0.57, P = .05), BACH1 (r = 0.88, P = .02), RBAK (r = 0.81, P = .05), TRIM32 (r = 0.92, P = .01), E2F2 (r = 0.81, P = .05), and TP53INP1 (r = -0.31, P = .03) as genes whose expression by quantitative real-time polymerase chain reaction correlated significantly with the level of miR-155 in ALCL tumor tissue.