Anne Marie Asemissen

Quantitative DNA Methylation Analysis of FOXP3 as a New Method for Counting Regulatory T Cells in Peripheral Blood and Solid Tissue

Regulatory T-cells (Treg) have been the focus of immunologic research due to their role in establishing tolerance for harmless antigens versus allowing immune responses against foes. Increased Treg frequencies measured by mRNA expression or protein synthesis of the Treg marker FOXP3 were found in various cancers, indicating that dysregulation of Treg levels contributes to tumor establishment. Furthermore, they constitute a key target of immunomodulatory therapies in cancer as well as transplantation settings. One core obstacle for understanding the role of Treg, thus far, is the inability of FOXP3 mRNA or protein detection methods to differentiate between Treg and activated T cells. These difficulties are aggravated by the technical demands of sample logistics and processing. Based on Treg-specific DNA demethylation within the FOXP3 locus, we present a novel method for monitoring Treg in human peripheral blood and solid tissues. We found that Treg numbers are significantly increased in the peripheral blood of patients with interleukin 2-treated melanoma and in formalin-fixed tissue from patients with lung and colon carcinomas. Conversely, we show that immunosuppressive therapy including therapeutic antibodies leads to a significant reduction of Treg from the peripheral blood of transplantation patients. In addition, Treg numbers are predictively elevated in the peripheral blood of patients with various solid tumors. Although our data generally correspond to data obtained with gene expression and protein-based methods, the results are less fluctuating and more specific to Treg. The assay presented here measures Treg robustly in blood and solid tissues regardless of conservation levels, promising fast screening of Treg in various clinical settings.

A clinical and immunologic phase 2 trial of Wilms tumor gene product 1 (WT1) peptide vaccination in patients with AML and MDS

This study investigated the immunogenicity of Wilms tumor gene product 1 (WT1)-peptide vaccination in WT1-expressing acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) patients without curative treatment option. Vaccination consisted of granulocyte-macrophage colony-stimulating factor subcutaneously days 1 to 4, and WT1.126-134 peptide and 1 mg keyhole limpet hemocyanin on day 3. The initial 9 patients received 4 vaccinations biweekly, then monthly, and the subsequent 10 patients received continual biweekly vaccination. Seventeen AML patients and 2 refractory anemia with excess blasts patients received a median of 11 vaccinations. Treatment was well tolerated. Objective responses in AML patients were 10 stable diseases (SDs) including 4 SDs with more than 50% blast reduction and 2 with hematologic improvement. An additional 4 patients had clinical benefit after initial progression, including 1 complete remission and 3 SDs. WT1 mRNA levels decreased at least 3-fold from baseline in 35% of patients. In 8 of 18 patients, WT1-tetramer(+) T cells increased in blood and in 8 of 17 patients in bone marrow, with a median frequency in bone marrow of 0.18% at baseline and 0.41% in week 18. This WT1 vaccination study provides immunologic, molecular, and preliminary evidence of potential clinical efficacy in AML patients, warranting further investigations.

Sunitinib Treatment for Patients with Advanced Clear-Cell Renal-Cell Carcinoma after Progression on Sorafenib

Background: Sorafenib and sunitinib are tyrosine kinase inhibitors with largely overlapping specificities, approved for the treatment of metastatic renal-cell carcinoma (RCC). It was unclear whether the similarities of the two drugs would lead to complete cross-resistance, or whether sequential application would be efficacious. Methods: Patients with metastatic RCC and progression on sorafenib treatment were treated with repeated cycles of sunitinib, 50 mg for 4 weeks, followed by a 2-week break. Response (Response Evaluation Criteria in Solid Tumors, RECIST) was assessed every second cycle. Results: A total of 22 patients with progression on sorafenib were accrued. Initially, sorafenib treatment was efficacious in all patients, with 7 showing partial response (PR) and 15 stable disease (SD), and subsequent disease progression. With 4 PRs (18%) and 12 SD (55%) a disease control rate of 73% was achieved. The median progression-free survival (PFS) on sunitinib was 21.5 weeks; median overall survival (OS) was not reached. Estimated 1-year PFS and OS were 31 and 60%, respectively. There was no apparent relationship between response to sorafenib and outcome on sunitinib. Conclusion: In our cohort of patients with RCC and progression after initial efficacy of sorafenib, the efficacy data of second-line sunitinib were close to published results of first-line treatment, suggesting limited clinically relevant cross-resistance.

Identification of a Highly Immunogenic HLA-A*01-Binding T Cell Epitope of WT1

Purpose: The transcription factor Wilms tumor protein 1 (WT1) belongs to a new generation of tumor antigens, as it is essential for tumor cell proliferation and is highly expressed in various hematologic and solid malignancies. The aim of this study was to apply a modified reverse immunology strategy to identify immunogenic epitopes of WT1 which could be useful for immunotherapy. Experimental Design: Potential HLA-A*01 epitopes predicted by a MHC binding algorithm were screened for recognition by peripheral blood mononuclear cells (PBMC) from patients with spontaneous T cell responses using intracellular cytokine cytometry. Epitope processing was shown by proteasomal cleavage. Epitope-specific T cells were generated from CD4+CD25+ regulatory T cell–depleted PBMC. Results: One of five predicted HLA-A*01-binding candidate epitopes showed high immunogenicity as 5 of 14 patients with hematologic malignancies had WT1.317-327–reactive T cells ranging from 0.4% to 1.5% of CD3+CD8+ T cells. Proteasomal degradation assays indicated the cleavage of WT1.317-327. The depletion of regulatory T cells from PBMCs enabled the rapid expansion of WT1.317-327–specific CTL, whereas no CTL could be generated from unfractionated PBMC. WT1.317-327–specific CTL efficiently lysed an autologous WT1-expressing tumor cell line but not HLA-A*01–negative WT1-expressing tumor cells. Immunogenicity of the epitope across histologies was verified by the demonstration of spontaneous ex vivo WT1.317-327–specific T cell responses in two of six patients with HLA-A*01–positive melanoma or lung cancer. Conclusion: In this study, a modified reverse immunology strategy was employed to identify a first immunogenic HLA-A*01–restricted T cell epitope of the tumor antigen WT1, which is of considerable interest for use in vaccination trials.

Immunomodulatory effects of sorafenib on peripheral immune effector cells in metastatic renal cell carcinoma

BACKGROUND Tyrosine kinase inhibitors (TKI) such as sorafenib have substantially improved the prognosis of metastatic renal cell carcinoma (mRCC) patients, but long-term remissions have only been reached with immunotherapy. Sequencing or combining TKI treatment with immunotherapy may represent an attractive therapeutic concept. However, in vitro data have shown that TKI may not only affect tumour cells, but also inhibit signalling in immune effector cells. Therefore, we asked whether sorafenib had an influence on peripheral immune effector cells in a cohort of 35 mRCC patients receiving sorafenib treatment. METHODS Peripheral blood (pB) samples were analysed at baseline and after 8 weeks of treatment. IL-10 and TGF-ß mRNA levels were quantified by RT-PCR; regulatory T cell (Treg) counts and intracellular cytokine responses (TNF-α, IFN-γ, IL-10 and TGF-ß) of mononuclear cell subsets were determined by flow cytometry after in vitro stimulation with PMA/ionomycin. RESULTS Sorafenib did not alter the elevated TGF-ß and IL-10 mRNA levels or elevated frequencies of IL-10 and TGF-ß producing monocytes and had no influence on type 1 cytokine responses in pB. CD4+CD25(high) FOXP3+/CD3+ T cells, likely representing Treg cells, decreased during sorafenib therapy. CONCLUSIONS In vivo, sorafenib treatment was associated with a decrease in frequency of Treg cells without influencing the function of peripheral immune effector cells. Therefore, although sorafenib did not convert the immunosuppressive phenotype associated with mRCC, it seemed to be a possible candidate for combination with immunotherapy.

Vaccination strategies in patients with renal cell carcinoma

Although new treatment options for patients with advanced renal cell cancer (RCC) have been developed within recent years, vaccination is still a promising emerging treatment option. An increasing number of tumor-associated antigens (TAA) available for RCC are currently used and analyzed for their efficacy for antigen-specific vaccine strategies. Recently, antigen-specific vaccination with dendritic cells in patients with metastatic RCC was shown to induce cytotoxic T cell response associated with objective clinical responses in some of the patients. Furthermore, current studies focus on the development of more effective vaccine regimes, such as the application of polyvalent, HLA-independent RNA coding for multiple TAA and adjuvants. First results demonstrate promising clinical and immunological efficacy. The efficacy of antigen-specific vaccination might be improved by a combination of tyrosine kinase inhibitors, since sunitinib was shown to promote T cell induction following vaccination in a mouse model and elimination of regulatory T cells.

Peptide vaccination after repeated resection of metastases can induce a prolonged relapse-free interval in melanoma patients

This pilot study was carried out to gain a first insight into the effects of peptide vaccination in melanoma patients in the high‐risk adjuvant disease setting. From the adjuvant peptide vaccination studies carried out in our institution since 1998, we identified all melanoma patients with a history of at least 3 completely resected metastases during the year preceding enrollment into the trial and describe the clinical and immunologic observations. Out of a total of 44 patients with resected cutaneous melanoma entered into adjuvant peptide vaccination trials, 9 patients were identified with more than 3 metastases in the year before vaccination. After initiation of vaccination, 2 patients remained relapse‐free for 27 and 42+ months, 2 patients experienced single or several initial relapses and subsequent relapse‐free intervals of 18 and 65+ months, whereas 5 patients progressed. In both patients with relapse after prolonged relapse‐free intervals, the relapses were initially confined to the small intestine and could be resected. Induction or boosting of functional tyrosinase peptide‐specific T cells was noted in 6 of 8 patients, including all 4 patients with prolonged relapse‐free intervals. In conclusion, adjuvant peptide vaccination was associated with cessation of recurrences in 4 of 9 patients, of whom all 4 had an immunologic response to the vaccine.

Specific central memory T cells in the bone marrow of patients immunized against tyrosinase peptides.

The goal of vaccination against tumors is the induction of effector T cells mediating tumor destruction and memory T cells providing long-term immunity. Several previous studies in patients vaccinated with major histocompatibility complex (MHC) class I peptides failed to show induction of central memory T cells, which are considered important to provide long-term memory. This study examined the subset composition and function of specific T cells generated by immunization with MHC class I binding tyrosinase peptides in combination with the adjuvants granulocyte-macrophage colony-stimulating factor and keyhole limpet hemocyanin in peripheral blood (PB) and bone marrow (BM) of melanoma patients. Most of the tyrosinase-specific T cells in PB had a CD45RA+CCR7− effector phenotype. In contrast to this, a large subset of tyrosinase-specific T cells in BM were memory T cells, including CD45RA−CCR7+ central and CD45RA−CCR7− effector memory T cells. BM tyrosinase-specific T cells were functional, because they produced interferon-γ and had a high proliferative potential. This study suggests that peptide vaccination can generate a fully functional memory T-cell response characterized by central and effector memory phenotypes, proliferative potential, and BM tropism.

Identification of an immunogenic HLA-A*0201-binding T-cell epitope of the transcription factor PAX2.

PAX2 is a transcription factor and member of the highly conserved family of paired box genes. PAX2 is aberrantly expressed in a variety of solid and hematologic malignancies. PAX2 regulates the transcription factor Wilms tumor gene 1, which is a promising target of cancer immunotherapy. The aim of this study was to apply a modified reverse immunology strategy to identify immunogenic epitopes of PAX2 which could be useful for cancer immunotherapy. Thirteen potential HLA-A*0201 epitopes were predicted by a major histocompatibility complex binding algorithm (SYFPEITHI) and a proteasome cleavage algorithm (PAProC) and screened for recognition by T cells from HLA-A*02-positive cancer patients using intracellular cytokine cytometry. Epitope-specific T cells were generated from CD4+CD25+ regulatory T-cell–depleted peripheral blood mononuclear cell. Nine of 20 colorectal cancer patients, 1 of 13 renal cell carcinoma patients, and 2 of 17 lymphoma patients had a spontaneous CD8+ T-cell response toward at least 1 of 6 PAX2 peptide pools. None of the 20 healthy subjects showed reactivity toward PAX2. PAX2.337-345 (TLPGYPPHV)-specific T cells could repeatedly be generated, which specifically lysed the PAX2 expressing colorectal tumor cell line SW480. In this study, a modified reverse immunology strategy was employed to identify a first immunogenic HLA-A*0201 restricted T-cell epitope and natural ligand of the tumor antigen PAX2. Thus, PAX2 is another embryonic transcription factor, which is of potential interest as immunotherapy target antigen.