Genes and Proteins Associated with the Tumor Microenvironment Are Differentially Expressed in Cured Versus Primary Chemotherapy-Refractory Diffuse Large B-Cell Lymphoma.

Background: The aim of this study was to identify possible differences in gene expression profiles (GEP) between two clinically very different patient populations, cured versus primary chemotherapy-refractory diffuse large B-cell lymphoma (DLBCL).

Material and methods: Tumor samples from 37 patients with de novo DLBCL, stage II-IV, either in continuous primary complete remission (n=24) or with progressive disease during primary treatment (n=13) were selected from a larger study cohort and examined with respect to GEP using spotted 55K oligonucleotide arrays. Formalin fixed paraffin-embedded tissue for immunohistochemical analysis was available in 33 of 37 cases, and was used for confirmation on protein level.

Results: The top 86 genes with the greatest statistical ability of discriminating the two patient groups were chosen for further analysis. Seventy-nine were over-expressed in the cured cohort, many of them coding for proteins expressed in the tumor microenvironment: CD68, several proteolytic enzymes and proteins involved in remodelling of extra cellular matrix and inflammation. Furthermore, MHC class I molecules, CD3δ, NK transcript 4, and ICAM-1 were overexpressed indicating an enhanced immunological reaction. Immunohistochemistry showed that the frequency of cells expressing CD68, defining the macrophage population, was higher in the cured cohort and that expression of lysozyme, cathepsin D, UPAR, and ICAM-1, was mainly seen within the reactive cells. Tumor infiltrating CD8+ T-cells were more frequent within the cured cohort, corresponding to the increased MHC class I expression seen within this group.

Conclusions: In DLBCL, genes coding for antigens present in the tumor microenvironment are differentially expressed in patients with cured vs. chemotherapy-refractory disease. Our findings suggest that a reactive microenvironment, including tumor infiltrating T-cells and macrophages, may have impact on outcome of chemotherapy in DLBCL.