Circulating monocytes and tumor-associated macrophages express recombined immunoglobulins in glioblastoma patients.

BACKGROUND: Glioblastoma is the most common and malignant brain tumor in adults. Glioblastoma is usually fatal 12-15 months after diagnosis and the current possibilities in therapy are mostly only palliative. Therefore, new forms of diagnosis and therapy are urgently needed. Since tumor-associated macrophages are key players in tumor progression and survival there is large potential in investigating their immunological characteristics in glioblastoma patients. Recent evidence shows the expression of variable immunoglobulins and TCRαß in subpopulations of monocytes, in vitro polarized macrophages and macrophages in the tumor microenvironment. We set out to investigate the immunoglobulin sequences of circulating monocytes and tumor-associated macrophages from glioblastoma patients to evaluate their potential as novel diagnostic or therapeutic targets. RESULTS: We routinely find consistent expression of immunoglobulins in tumor-associated macrophages (TAM) and circulating monocytes from all glioblastoma patients analyzed in this study. However, the immunoglobulin repertoires of circulating monocytes and TAM are generally more restricted compared to B cells. Furthermore, the immunoglobulin expression in the macrophage populations negatively correlates with the tumor volume. Interestingly, the comparison of somatic mutations, V-chain usage, CDR3-length and the distribution of used heavy chain genes on the locus of chromosome 14 of the immunoglobulins from myeloid to B cells revealed virtually no differences. CONCLUSIONS: The investigation of the immunoglobulin repertoires from TAM and circulating monocytes in glioblastoma-patients revealed a negative correlation to the tumor volume, which could not be detected in the immunoglobulin repertoires of the patients' B lymphocytes. Furthermore, the immunoglobulin repertoires of monocytes were more diverse than the repertoires of the macrophages in the tumor microenvironment from the same patients suggesting a tumor-specific immune response which could be advantageous for the use as diagnostic or therapeutic target.

Expression of combinatorial immunoglobulins in macrophages in the tumor microenvironment.

Recent evidence indicates the presence of macrophage subpopulations that express the TCRαß in chronic inflammatory diseases such as tuberculosis and atherosclerosis and in the tumor microenvironment. Here, we demonstrate that a second subpopulation of macrophages expresses rearranged heavy and light chain immunoglobulins. We identify immunoglobulin expression in human and murine monocytes, in ex vivo differentiated macrophages and macrophages from the tumor microenvironment of five randomly selected distinct human tumor entities. The immunoglobulin heavy and light chains are expressed in a small macrophage subfraction (~3-5%) as combinatorial and individual-specific immune receptors. Using Sanger sequencing and deep sequencing, we routinely find markedly restricted Ig repertoires in monocytes/macrophages compared to normal B cells. Furthermore, we report the complete Ig heavy and light chain sequences of a fully functional immunoglobulin from a single tumor-associated macrophage. These results demonstrate that Ig expression is a defining feature of monocytes and also macrophages in the tumor microenvironment and thus reveal an as yet unrecognized modus operandi of host defense in professional phagocytes.

A combinatorial αß T cell receptor expressed by macrophages in the tumor microenvironment.

Recent evidence indicates the presence of macrophage subpopulations that express the TCRαß in two major inflammatory diseases, tuberculosis and atherosclerosis. Inflammation is also a well-established attribute of cancer progression and macrophages are one of the major immune cells that infiltrate tumors. Here, we demonstrate that the macrophage-TCRαß is expressed in the tumor microenvironment of human and murine malignancies. We identify TCRαß+ macrophages in each case of four randomly selected distinct human tumor entities. In human tumor tissues, the TCRαß expressed by macrophages in the tumor microenvironment is a combinatorial and individual-specific immune receptor. Furthermore, we routinely find TCRαß+ macrophage subpopulations in experimental tumors (TS/A, mammary adenocarcinoma) which we induced both in normal mice and mice deficient in the macrophage receptor stabilin-1. Expression of the combinatorial murine tumor macrophage TCRαß is individual-specific and independent of stabilin-1. These results demonstrate that TCRαß expression is a characteristic feature of macrophages in the tumor microenvironment and identify an as yet unrecognized flexible element in the macrophage-based host response to tumors.

Vascular architecture as a diagnostic marker for differentiation of World Health Organization thymoma subtypes and thymic carcinoma.

AIMS: Thymomas and thymic squamous cell carcinomas (TSQCCs) are rare thymic epithelial tumours. Data on angiogenesis and vascular phenotype in these tumours are limited, and no study has taken histological World Health Organization (WHO) subtypes into account. The aim of this study was to compare vascularization, pericytes coverage and expression of angiogenic growth factors in different WHO-defined subtypes of thymoma METHODS AND RESULTS: Vascular density, diameter and architecture and expression of α-smooth muscle actin (SMA), platelet-derived growth factor (PDGF) receptor-ß (PDGFRß), vascular endothelial growth factor (VEGF) receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) were investigated in WHO type A, AB, B1, B2 and B3 thymomas and TSQCCs, by the use of immunostaining, quantitative morphometry, and tumour vessel isolation by trypsin digestion. Expression levels of angiopoietin 1 (Ang-1), angiopoietin 2 (Ang-2), VEGF-A, PDGF-B and Hif-1α were examined by quantitative reverse transcription polymerase chain reaction. A and AB thymomas were characterized by a dense network of capillary-like vessels with tight pericyte coverage, whereas B thymomas showed a loose vascular network with increasing vascular diameters and increasing expression of SMA and PDGFRß from B1 to B3 thymomas and TSQCCs. VEGFR1 and VEGFR2 were expressed in vessels of all analysed tumour entities, and at higher levels in epithelial cells of A and B3 thymomas and TSQCCs. mRNA of Ang-2, but not of Ang-1, was significantly up-regulated in all thymoma subtypes, with the highest levels being found in A thymomas. In TSQCCs, Ang-1 and VEGF were the predominantly up-regulated growth factors. Hif-1α was only up-regulated in B3 thymomas and TSQCCs. CONCLUSION: Thymomas and TSQCCs differ significantly in their vascular architecture and expression of key angiogenic growth factors. The findings could help to improve the differential diagnosis of difficult-to-classify thymic epithelial tumours, and indicate different mechanisms of tumour angiogenesis and functional differences of tumour vessels of major thymoma subtypes and TSQCCs.