Fibromodulin as a novel tumor-associated antigen (TAA) in chronic lymphocytic leukemia (CLL), which allows expansion of specific CD8+ autologous T lymphocytes

Abstract

Fibromodulin (FMOD) was shown to be highly overexpressed in chronic lymphocytic leukemia (CLL) cells compared with normal B lymphocytes by gene expression profiling. Therefore FMOD might serve as potential tumor-associated antigen (TAA) in CLL, enabling expansion of FMOD-specific T cells. In CLL samples derived from 16 different patients, high expression of FMOD by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was detectable in contrast to normal B lymphocytes. We used unpulsed native CLL cells and CD40 ligand (CD40L)-stimulated CLL cells as antigen-presenting cells (APCs) to expand autologous T cells from 13 patients. The number of T cells during 4 weeks of in vitro culture increased 2- to 3.5-fold and the number of T cells recognizing FMOD peptides bound to HLA-A2 dimers increased 10-fold. The expanded T cells also were able to secrete interferon-gamma (IFN-gamma) upon recognition of the antigen demonstrated by IFN-gamma ELISPOT assays. T cells not only recognized HLA-A2-binding FMOD peptides presented by transporter-associated with antigen-processing (TAP)-deficient T2 cells, but also FMOD overexpressing autologous CLL cells in an HLA-A2-restricted manner. In summary, FMOD was shown for the first time to be naturally processed and presented as TAA in primary CLL cells, enabling the expansion of autologous tumor-specific T cells.