[1179] Differential Expression of L-Plastin in Primary Mediastinal Large B-Cell Lymphoma (PMBCL) and Classical Hodgkin Lymphoma (cHL)

MD Chiselite, V Basrur, D Fermin, K Conlon, J Teruya-Feldstein, KSJ Elenitoba-Johnson, MS Lim. University of Michigan, Ann Arbor, MI; Memorial Sloan-Kettering Cancer Center, New York, NY

Background: PMBCL is a rare subtype of extranodal diffuse large B-cell lymphoma (DLBCL) that is difficult to distinguish from other types of DLBCL and cHL. Recent studies reveal similar gene expression profiles in PMBCL and cHL suggesting a common cell of origin. We hypothesized that quantitative mass spectrometry-based proteomic strategies would be useful in identifying potential protein biomarkers that may help in the distinction of these lymphomas.
Design: We performed proteomic analysis of three cell lines: PMBCL (Karpas 1106P), cHL (L428) and DLBCL (SUDHL-9) using a differential isotopic strategy, iTRAQ (isobaric tag for relative and absolute quantitation) and tandem mass spectrometry. After normalization, quantitative data were subjected to false discovery rate (FDR) calculation to identify differentially expressed proteins through Mixture Modeling. Significantly differentially expressed proteins were scored at a false discovery rate (FDR) cut-off of 0.13. L-plastin was selected and validated by immunoblotting (clone LPL4A.1, NeoMarkers, Fremont, CA) on PMBCL and cHL cell lines and immunohistochemistry of tissue microarrays (TMAs) of PMBCL (n=37), cHL (n=94) and NLPHL (n=16).
Results: Several proteins that have been previously reported to be differentially expressed between cHL and PMBCL were identified including Fascin, Galectin-1, Galectin-3, STAT1 and SWAP70. We selected one protein, L-plastin for validation. Western blotting showed high L-plastin expression in the PMBCL cell lines K1106P and MedB1, relative to cHL cell lines confirming the mass spectrometry data. The prevalence of L-plastin expression in TMAs was as follows:

L-plastin	(-)	weak(+)	mod/strong(+)
PMBCL	1/37	4/37	32/37
cHL	32/94	37/94	25/94
NLPHL	1/16	3/16	12/16

Conclusions: We identified L-plastin, a 65 kDa leukocyte-specific actin bundling protein to be differentially expressed in PMBCL and cHL. The strong expression of L-plastin in 32/37 (86%) of tissue samples of PMBCL and 25/94 (27%) cHL suggest that it may be useful in the distinction of these two neoplasms (P<0.0001). This study demonstrates the utility of large-scale mass spectrometry-based proteomics for the discovery of proteins that may serve as potential diagnostic marker panels for the distinction of PMBCL and cHL, as well as candidate therapeutic targets.
Category: Hematopathology

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 176, Monday Morning