[1264] Immunohistologic Features and Epigenetic Signatures Correlate with Disease Progression in Chronic Lymphocytic Leukemia.

Julia T Geyer, Wayne Tam, Daniel M Knowles, Sharon Barouk, George K Turi, Yi-Fang Liu, Ari Melnick, Rita Shaknovich, Attilio Orazi. Weill Cornell Medical College, New York; Winthrop University Hospital, Mineola

Background: Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in Western countries. 2-8% of patients transform to aggressive lymphoma (Richter's transformation, RT). The pathogenesis of RT is poorly understood. Over the course of the disease, many CLL cases develop atypical morphologic features, such as expanded proliferation centers (PC) and increased numbers of large cells (LC). It is currently unclear if these features represent evolution of "typical" CLL into more aggressive lymphoma. The goal of our study was to characterize disease progression in CLL.
Design: 33 biopsies from 29 patients were selected. Cases were divided into 4 groups based on morphology and Ki-67 staining: typical CLL (n=12, G1), CLL with expanded PCs (n=12, G2), CLL with increased number of LCs (n=6, G3) and RT (n=3, G4). Immunohistochemical stains for Tcl-1, Mcl-1, VEGF, c-MYC, AID, MUM-1, p27, p53 and ZAP70 were performed. Methylation analysis was performed using HELP assay and Roche NimbleGen custom human promoter array in 10 cases. Laboratory values and clinical follow-up were collected. Results were analysed with the Student's t test, chi square test and moderated t-test.
Results: Based on immunohistochemical stains, G3 had significanly higher Ki-67, p53, MUM-1, c-MYC, AID and lower Tcl-1 and p27, compared to G1 and G2. Tcl-1 was significantly lower in G4 compared to the other cases. The CBC values were not significantly different between the groups. Epigenetic analysis showed that 61 genes were differentially methylated between G1 and G2, mainly involving the VEGF pathway, while 65 genes were different between G2 and G3, involving the p38 MAPK pathway. Many members of NF-kB pathway had methylation changes in all groups. 7 of 27 patients with available follow-up (26%) had an aggressive clinical course. Of these, 9% were in G1, 22% in G2, 40% in G3 and 67% in G4. The difference between G1 and G2 vs G4 was statistically significant.
Conclusions: Expanded PCs and increased LCs seen in "accelerated phase" CLL (groups 2 and 3) correlated with immunohistochemical markers of increased proliferative activity, such as Ki-67, c-MYC and MUM-1 or genetic instability, such as AID and p53. Epigenetic profiling showed that different grades of CLL may have distinct methylation signatures related to important signal transduction pathways, confirming morphology as a potentially valid method of case stratification. Thus, it appears that specific biological pathways are deregulated during CLL progression.
Category: Hematopathology

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 167, Wednesday Morning

 

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