Contrasting frequencies of antitumor and anti-vaccine T cells in metastases of a melanoma patient vaccinated with a MAGE tumor antigen

Abstract

Melanoma patients have high frequencies of T cells directed against antigens of their tumor. The frequency of these antitumor T cells in the blood is usually well above that of the anti-vaccine T cells observed after vaccination with tumor antigens. In a patient vaccinated with a MAGE-3 antigen presented by HLA-A1, we measured the frequencies of anti-vaccine and antitumor T cells in several metastases to evaluate their respective potential contribution to tumor rejection. The frequency of anti-MAGE-3.A1 T cells was 1.5 x 10(-5) of CD8 T cells in an invaded lymph node, sixfold higher than in the blood. An antitumor cytotoxic T lymphocyte (CTL) recognizing a MAGE-C2 antigen showed a much higher enrichment with a frequency of approximately 10%, 1,000 times higher than its blood frequency. Several other antitumor T clonotypes had frequencies >1%. Similar findings were made on a regressing cutaneous metastasis. Thus, antitumor T cells were approximately 10,000 times more frequent than anti-vaccine T cells inside metastases, representing the majority of T cells present there. This suggests that the anti-vaccine CTLs are not the effectors that kill the bulk of the tumor cells, but that their interaction with the tumor generates conditions enabling the stimulation of large numbers of antitumor CTLs that proceed to destroy the tumor cells. Naive T cells appear to be stimulated in the course of this process as new antitumor clonotypes arise after vaccination.

Figure 1.

Clinical evolution of patient EB81 and timing of vaccinations and blood cell collections.

Figure 2.

Analysis of the invaded lymph node resected in April 2000. (A) Overall structure presented on a cryosection stained with hematoxylin. A circular area of living tumor cells (a) is surrounded by a fibrous band (b). Above, a crescent-shaped region (c) is devoid of tumor cells. Numerous macrophages containing melanin and other inflammatory cells are present in this region (see D). The area on the left part of the section (d) represents the uninvaded part of the lymph node. The stippled ellipse indicates the localization of the area shown in B. The 1-mm holes represent samples collected by laser microdissections for gene expression analysis. (B–F) Paraffin-embedded sections stained with hematoxylin and (B–D) eosin. (B) Higher magnification of an area straddling the living tumor cell region and the fibrous band, which is infiltrated with lymphocytes. Macrophages containing melanin are located at the outer rim of the tumor cell region. The rectangle delineates the area shown in C. (C) Further enlargement of the border between tumor cells (1) and the fibrous band, which contains macrophages with melanin accumulation (2) and lymphocytes (3). (D) Higher magnification of region c (A) with fibroblasts (1), macrophages with melanin (brown-colored; 2), lymphocytes (3), and plasmocytes (4). (E and F) Adjacent sections treated with anti-CD3 (E) and anti-CD8α antibodies (F). T cells infiltrating the tumor are stained in red (immunoperoxidase). Macrophages with melanin are brownish.