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Int J Clin Exp Pathol 2012;5(6):503-511

Original Article
Morphoproteomics provides support for TGF-β pathway signaling in the
osteoclastogenesis and immune dysregulation of osteolytic Langerhans cell histiocytosis

Alexandrescu S, Tatevian N, Czerniak BA, Covinsky M, Burns N, Brown RE

Department of Pathology, University of Texas at Houston – Health Science Center; Department of Pathology, MD Anderson Cancer Center,
Houston, TX, USA

Received May 20, 2012; Accepted June 25, 2012; Epub July 29, 2012; Published August 15, 2012

Abstract: Langerhans cell histiocytosis (LCH) has a challenging and still unclear pathogenesis. A body of literature points to impaired
maturation of the lesional dendritic cells, and to immune dysregulation in the form of increased FoxP3 cells. Various cytokine abnormalities
such as expression of transforming growth factor (TGF)-β have been reported, as well as abnormalities in lipid content in LCH cells.
Morphoproteomic techniques were applied to identify the signal transduction pathways that could influence histogenesis and immune
regulation in osteolytic LCH. Five pediatric cases of osteolytic LCH were examined, using antibodies against CD1a, S100, CD68, CD8, FoxP3,
phosphorylated (p)-STAT3 (Tyr705), protein kinase C (PKC)-α, phospholipase (PL)D1, fatty acid synthase (FASN), and zinc finger protein, Gli2.
Positive and negative controls were performed. A FoxP3(+)/CD8(+) cell ratio was calculated by counting the FoxP3+ and CD8+ cells in 10 high
power fields for each case. There is induction of sonic hedgehog (SHH) mediators consistent with TGF-β signaling pathway through Smad3-
dependent activation of Gli2, findings supported by the plasmalemmal and cytoplasmic expression of PKC-α and PLD1, and nuclear
expression of Gli2, in lesional cells. The FoxP3+/CD8+ cell ratio is increased, ranging from 1.7-7.94. There is moderate cytoplasmic
expression of FASN in most of the Langerhans cells, a finding that supports previously published phospholipid abnormalities in LCH and is
consistent with PKC-α/PLD1/TGF-β signaling. With our study, we strongly suggest that the TGF-β cell signaling pathway is a major player in the
pathogenesis of LCH, leading to non-canonical induction of nuclear Gli2 expression, thereby contributing to osteoclastogenesis in LCH
histiocytes. It could also cause a state of immune frustration in LCH, by inducing the transformation of CD4(+)CD25(-) cells into CD4(+)/FoxP3
(+) cells. This coincides with the clinical evidence of a response to thalidomide in patients with osteolytic LCH, given its reported ability to
reduce TGF-beta 1 and FoxP3 cells. Such TGF-β signaling in osteoclastogenesis and immune dysregulation, and the presence of FASN in the
majority of cells, have additional therapeutic implications for osteolytic LCH. (IJCEP1205007).

Keywords: Morphoproteomics, TGF-β, signaling pathway, osteoclastogenesis, histogenesis, Langerhans cell histiocytosis

Address all correspondence to:
Dr. Robert E Brown
Department of Pathology and Laboratory Medicine
University of Texas – Houston, 6431 Fannin Street
Houston, TX 77030, USA.
Tel: (713)500-5332
E-mail: Robert.Brown@uth.tmc.edu