Differential expression of cyclin D3 in ALK+ and ALK− anaplastic large cell lymphoma

As defined in the World Health Organization classification, anaplastic large cell lymphoma (ALCL) is a distinct type of non–Hodgkin lymphoma of T/null cell lineage, a subset of which is associated with translocations involving 2p23 resulting in expression of anaplastic lymphoma kinase (ALK). The most common translocation, the t(2;5)(p23;q35), results in expression of nucleophosmin (NPM)–ALK. NPM-ALK has been shown to activate signal transducer and activator of transcription (STAT) 3, a transcriptional regulator of cyclin D3. In this study, we assessed cyclin D3 expression in 2 ALK+ ALCL cell lines (Karpas 299 and SU-DHL1) and 1 ALK− ALCL cell line (Mac2A) by Western blot analysis. We also assessed cyclin D3 expression in 52 ALCL tumors (32 ALK+, 20 ALK−) by immunohistochemistry using tissue microarrays. These results were compared with phosphorylated (activated) STAT3 (pSTAT3) expression. Both ALK+ ALCL cell lines, but not the ALK− ALCL cell line, expressed cyclin D3 and pSTAT3. Cyclin D3 was expressed in 25 (78%) of 32 ALK+ ALCL tumors and in 4 (20%) of 20 ALK− ALCL tumors ( P < .001, Fisher exact test ). In ALK+ ALCL tumors, the mean percentage of cyclin D3–positive tumor cells was 40.6% compared with 5.1% in ALK− ALCL tumors ( P < .001, Mann-Whitney U test). The percentages of cyclin D3–positive and pSTAT3-positive tumor cells were positively correlated (Spearman R = 0.35, P = .036). We conclude that cyclin D3 is differentially expressed in ALK+ and ALK− ALCL and that high expression levels of cyclin D3 in ALK+ ALCL may be attributable to STAT3 activation.