Tumor Microenvironment and Checkpoint Molecules in Primary Cutaneous Diffuse Large B-Cell Lymphoma—New Therapeutic Targets. (July 2017)

• Record Type: Journal Article
• Authors: Mitteldorf, Christina; Berisha, Arbeneshe; Pfaltz, Monique C.; Broekaert, Sigrid M.C.; Schön, Michael P.; Kerl, Katrin; Kempf, Werner
• Is Part Of: American journal of surgical pathology. Volume 41:Number 7(2017)
• Publication Date: 2017-07
• Subjects: primary cutaneous diffuse large B-cell lymphoma -- PD-L1 -- CD33 -- tumor microenvironment -- checkpoint molecules; Pathology, Surgical -- Periodicals; 617.0705
• DOI: 10.1097/PAS.0000000000000851
• Languages: English
• ISSNs: 0147-5185

Abstract

Abstract : Programmed death ligand 1 (PD-L1) is expressed by 20% to 57% of systemic diffuse large B cell lymphomas (DLBCLs). PD-L1 expression in primary cutaneous DLBCL (pcDLBCL) has not been studied so far. Sixteen paraffin-embedded tissue samples of pcDLBCL (13 leg type [LT], 3 others [OT]) were investigated for PD-1, PD-L1, and CD33 expression and the cellular composition of the tumor microenvironment, focusing on myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages. Membrane-bound PD-L1 expression by the tumor cells was observed in all samples, albeit to a variable extent (19.9%). As expected, most DLBCL-LT (10 cases) were classified as activated B cell like type, with a higher PD-L1 score (21.9%) compared with that of the germinal center B cell like type (7.7%). The surrounding infiltrate consisted predominately of CD163(+) M2 rather than CD68(+) macrophages (CD68:CD163=1:4 to 6). Moreover, a considerable proportion of CD33(+) MDSCs with PD-L1 coexpression was admixed. Tumor cells expressed CD33 to variable degrees (2% to 60%). The number of MDSCs or M2 macrophages did not correlate with pcDLBCL subtypes LT or OT. T cells were only a minor component of the tumor microenvironment. We propose that PD-L1(+) tumor cells and PD-L1(+) MDSCs shield the tumor against PD-1(+) tumor-infiltrating lymphocytes, consequently leading to inhibition and diminution of tumor-infiltrating lymphocytes. Moreover, we found a polarization to M2 macrophages, which may contribute to the poor prognosis of DLBCL patients. Thus, targeting of tumor cells and MDSCs using anti-PD-1/anti-PD-L1 or anti-CD33 antibodies might be a worthwhile new approach to treat this aggressive form of cutaneous B-cell lymphoma.