PDF file - 233K, Definition of criteria for SKIL culture evaluation: Three examples are shown to illustrate the definition of SKIL culture criteria. (A) Criterion III, one patient (IV-B-16-St) with a clear population of TAA-specific CD8+ T cells in SKIL cultures, which produce high levels of IFNg upon encounter of both the defined gp100 peptides and naturally processed gp100 presented by a HLA-A*02:01 positive melanoma cell line (Mel624). Moderate amounts of IL-2 are produced and minimal production of IL-5, representing a clear IFNg dominant cytokine profile. (B) Criterion II, a patient (IV-B-11-Ro) with TAA-specific CD8+ T cells in SKIL cultures which produce high levels of IFNg and IL-2 upon encounter of the gp100 peptide, but fail to recognize the naturally processed gp100. (C) Criterion I, a patient (IV-A-07-Th) with a population of TAA-specific CD8+ T cells in SKIL cultures, recognizing the g100-154 peptide, but not the naturally processed gp100. Furthermore, those TAA-specific CD8+ T cells do not produce IFNg but produce elevated levels of IL-5 instead, indicating that the immune system is skewed towards tumor tolerance
ARTICLE ABSTRACT
The identification of responding patients early during treatment would improve the capability to develop effective new immunotherapies more rapidly. Here, we describe a bioassay that may link early T-cell–mediated immune responses to later clinical benefits. This bioassay rests upon the tenet of immunotherapy that tumor-specific effector T cells capable of invading peripheral tissue can recognize tumor antigens and exert cytotoxic functions there. To show its utility, we conducted a retrospective study of a large cohort of metastatic melanoma patients (n = 91) enrolled in dendritic cell (DC)-based vaccination protocols to examine a hypothesized correlation of posttreatment skin-infiltrating lymphocytes (SKIL) with overall survival (OS). Stringent immunologic criteria were defined to identify long-term survivors. The presence of tumor-associated antigen (TAA)-specific CD8+ T cell populations within SKILs (criterion I) was highly predictive for long-term survival. Further restriction by selecting for the presence of TAA-specific CD8+ T cells specifically recognizing tumor peptide (criterion II) was also associated with improved OS. Recognition of naturally processed antigen (criterion III) maximized the accuracy of the test, with a median OS of 24.1 versus 9.9 months (P = 0.001). Our results show that detailed characterization of SKILs can permit an accurate selection of metastatic melanoma patients who benefit most from DC-based vaccination. This simple and robust bioassay integrates multiple aspects of cellular functions that mediate effective immune responses, thereby offering an effective tool to rapidly identify patients who are responding to immunotherapy at an early stage of treatment. Cancer Res; 72(23); 6102–10. ©2012 AACR.
