[1376] CD317 Is Over-Expressed in B-CLL and Promotes Cell Growth In Vitro

Shunyou Gong, Ebenezer S Osei, David Kaplan, Youhai Chen, Howard Meyerson. University Hospitals Case Medical Center and Case Western Reserve University School of Medicine, Cleveland, OH; University of Pennsylvania Perelman School of Medicine, Philadelphia, PA

Background: CD317 is originally identified as a GPI-anchored membrane protein over-expressed on multiple myeloma cells. HM1.24, the monoclonal antibody against CD317, is in clinical trials as an immunotherapy reagent. We evaluated the expression of CD317 in B-cell chronic lymphocytic leukemia (B-CLL) to determine if HM1.24 might be of use as a therapeutic agent in B-CLL. Additionally, due to its potential impact on cell growth, we also evaluated the biological significance of CD317 over-expression in a B cell line using lentivirus-mediated RNA interference (RNAi). To our knowledge, neither the expression of CD317 in B-CLL, nor the biological significance of CD317 over-expression in lymphoid malignancies, has been systemically studied.
Design: The peripheral blood or bone marrow specimens from 27 B-CLL patients were stained with anti-CD317-PE and other lymphoid markers, and then analyzed by flow cytometry. The mean fluorescence intensity (MFI) of CD317 on B-CLL cells was compared with expression on normal B lymphocytes. Over- or down-expression was evaluated by fold MFI change. To evaluate the biologic significance of CD317 over-expression, we used RNAi to knock down CD317 in sp2/0, a B-cell line with constitutively high level of CD317 expression. Growth curves of cultured CD317 RNAi sp2/0 cells were compared to that of mock-infected sp2/0 cells.
Results: Among 27 B-CLL cases, 19 (70%) of them had clearly detectable over-expression of CD317 (MFI increased 50% or higher, compared to that of normal B cells). The over-expression of CD317 in B-CLL was statistically significant as the MFI increase in B-CLL was 2.2 +/- 1.5 fold (P=0.0018, Student's t-test), compared to normal B cells. In the cell growth experiments, the CD317 RNAi sp2/0 cells grew at a significantly slower speed than mock infected control cells. The growth rate of CD317 RNAi sp2/0 cells was 2.8 +/- 0.3 times slower than the control cells (p<0.001, Student's t-test).
Conclusions: CD317 is over-expressed in most B-CLLs suggesting that anti-CD317 immunotherapy may be effective in B-CLL. Knockdown of CD317 in cultured cells lead to decreased cell growth. Therefore, it would be of interest to evaluate whether B-CLLs with over-expression of CD317 have a more rapid growth in vivo, and whether CD317 over-expression in B-CLL has an impact on prognosis.
Category: Hematopathology

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 210, Monday Morning

 

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