Correlation between tumor regression and T cell responses in melanoma patients vaccinated with a MAGE antigen

Abstract

The cancer-germline gene MAGE-3 codes for tumor-specific antigens recognized on many tumors by T lymphocytes. A MAGE-3 antigen presented by HLA-A1 has been used in several vaccination trials on metastatic melanoma patients. Only a small minority of patients have shown evidence of tumor regression. Attempts to correlate the tumor rejections with the cytotoxic T lymphocyte (CTL) response against the vaccine have been hampered by the low level of these responses. In noncancerous individuals, the frequency of the T cell precursors against antigen MAGE-3.A1 is Ϸ4 ؋ 10 ؊7 CD8 T cells. The diversity of the T cell receptor repertoire of these anti-MAGE-3.A1 precursors was analyzed in one individual. The results indicate that it is very likely that the repertoire comprises >100 clonotypes. On this basis, it is possible to use not only the frequency of CTL precursors in the blood but also the presence of dominant clonotypes to ascertain in patients the existence of anti-MAGE-3.A1 responses as low as 10 ؊6 of CD8. With this approach, we observed a correlation between tumor regression and anti-MAGE-3.A1 CTL responses in patients vaccinated with a recombinant virus encoding the antigen and also in patients vaccinated with peptide-pulsed dendritic cells. In contrast, for patients showing tumor regression after vaccination with peptide alone, CTL responses were almost never observed. It is possible that even those CTL responses that are below our present detection level can trigger a sequence of events that leads to tumor regression. S hared tumor-specific antigens encoded by cancer-germline genes such as those of the MAGE family have been used for therapeutic vaccination of cancer patients. A number of small clinical trials on metastatic melanoma patients have been performed with the MAGE-3 168-176 antigen EVDPIGHLY, which is presented by HLA-A1 (1, 2). Evidence of tumor regression was observed in Ϸ20% of the patients, but clinical benefit was limited to Ϸ10% of the patients.Our initial work suggested that in most vaccinated patients, even in those who displayed tumor regression, it was difficult to ascertain the existence of an antivaccine T cell response. We nevertheless felt that it was crucial to know whether low-level responses had occurred and whether such cytotoxic T lymphocyte (CTL) responses showed a correlation with tumor regression to understand why most patients failed to show any evidence of regression. We therefore developed a sensitive approach based on in vitro restimulation of blood lymphocytes with the antigenic peptide over 2 weeks, followed by labeling with tetramers. To evaluate precursor frequencies, these mixed lymphocyte-peptide cultures were conducted under limiting dilution conditions. Cells that were labeled with the tetramer were cloned, the lytic specificity of the clones was verified, and their diversity was analyzed by T cell receptor (TCR) sequencing (3).As the interpretation of these analyses was based on both the frequency and the diversity of the anti-MAGE-3.A1 CTL clones, it was necessary t...

Vaccination of a Melanoma Patient with Mature Dendritic Cells Pulsed with MAGE-3 Peptides Triggers the Activity of Nonvaccine Anti-Tumor Cells

“…1B). Similar very low frequencies have been observed previously in noncancerous individuals (30). After vaccination, the frequency increased steadily, reaching a value of 5.6 ϫ 10 Ϫ6 after nine vaccinations.…”

Frequent occurrence of high affinity T cells against MELOE‐1 makes this antigen an attractive target for melanoma immunotherapy

“…Nonetheless, frequencies of MAGE-3/A1-specific T cells have been evaluated in healthy donors by a limiting dilution approach [15] and reveal a frequency as low as 2 in 1 Â 10 7 CD8 1 T cells. This frequency ranged between 7 in 1 Â 10 7 and 3 in 1 Â 10 3 in patients who were immune responders to a vaccination with a recombinant virus encoding the antigen, while this frequency remains around 5 in 1 Â 10 7 in non-responder patients [27]. The only other study reporting a high frequency of lymphocytes specific for a tumorspecific antigen dealt with NY-ESO-1-specific CTL frequencies (around 2 in 1 Â 10 4 CD8 1 T cells) observed in only one melanoma patient [28].…”

A Phase I-II Study of α-Galactosylceramide-Pulsed IL-2/GM-CSF-Cultured Peripheral Blood Mononuclear Cells in Patients with Advanced and Recurrent Non-Small Cell Lung Cancer

“…At present, a correlation between the induction of immune responses during various immunotherapy and the clinical outcome of treated patients remains controversial (35)(36)(37)(38). This dispute could be due to the variation of the quality of immunological assays among investigators, variable levels of tumor burden, and the different criteria used for measuring clinical responses by tumor immunotherapy.…”