Identification and Characterization of T-Cell Epitopes Deduced from RGS5, a Novel Broadly Expressed Tumor Antigen

Abstract

Purpose: Identification of tumor-associated antigens and advances in tumor immunology resulted in the development of vaccination strategies to treat patients with malignant diseases. In a novel experimental approach that combined comparative mRNA expression analysis of defined cell types with the characterization of MHC ligands by mass spectrometry, we found that regulator of G protein signaling 5 (RGS5) is extensively up-regulated in a broad variety of malignant cells, and we identified two HLA-A2^and HLA-A3^binding peptides derived from the RGS5 protein. Interestingly, RGS5 was recently shown to be involved in tumor angiogenesis. Experimental Design: We used monocyte-derived dendritic cells pulsed with these novel antigenic peptides or transfected with RGS5-mRNA for the in vitro induction of CTLs, generated from healthy donors, to analyze the presentation of RGS5-deduced epitopes by malignant cells. Results: The generated CTL lines elicited an antigen-specific and HLA-restricted cytolytic activity against tumor cells endogenously expressing the RGS5 protein. Furthermore, we were able to induce RGS5-specific CTLs using peripheral blood mononuclear cells from a patient with acute myeloid leukemia capable of recognizing the autologous leukemic blasts while sparing nonmalignant cells. Conclusions: These results indicate that the RGS5 peptides represent interesting candidates for the development of cancer vaccines designed to target malignant cells and tumor vessels.

Spontaneous Peripheral T-cell Responses toward the Tumor-Associated Antigen Cyclin D1 in Patients with Clear Cell Renal Cell Carcinoma

“…This finding is in agreement with previously published data on rare T-cell responses in patients with ccRCC (15), even though ADFP-and C-MET-specific T cells could be expanded from the blood of healthy donors (33,34). RGS-5 overexpression did not result in detectable RGS-5-specific T-cell responses in our cohort, although such responses were reported in the blood of healthy donors and patients with acute myeloid leukemia (42). In contrast, we detected cyclin D1-specific CD8 þ T cells in the blood of 5 of 6 patients with HLA-A2 þ ccRCC, whose tumors overexpressed Cyclin D1.…”

Vascular normalization in Rgs5-deficient tumours promotes immune destruction

“…Studies are under way to elucidate pathways regulated by RGS5 in tumour pericytes for pharmacotherapeutic intervention in combination with immune therapy. Recognition that RGS5 is a broadly expressed tumour antigen 25 and is also vesselassociated in numerous tumours (for example, astrocytomas and insulinomas 10 , renal cell carcinoma 26 and hepatocellular carcinoma 27 ) confirms its general importance in tumorigenesis and expands potential therapeutic opportunities.…”

Leukemia-associated antigens and their relevance to the immunotherapy of acute myeloid leukemia

“…16 This peptide sequence also encompasses the HLA-DP5-restricted WT1 337-347 epitope 70 as well as the WT1 333-347 epitope, which can be recognized by CD4 þ regulatory T cells in the context of HLA-DR4. 71 Other WT1 helper epitopes with direct relevance to AML immunotherapy are WT1 427-445 and WT1 [122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140] . 69 The latter contains another immunogenic CD4 þ T-cell epitope, WT1 [124][125][126][127][128][129][130][131][132][133][134][135][136][137][138] , and the HLA-A*0201-restricted CD8 þ T-cell epitope, WT1 [126][127][128][129][130][131][132][133][134] , 16 and is thus capable of stimulating a combined CD8 þ /CD4 þ WT1-specific T-cell immune response.…”