The transfer of T cell receptor (TCR) genes can be used to induce immune reactivity toward defined antigens to which endogenous T cells are insufficiently reactive. This approach, which is called TCR gene therapy, is being developed to target tumors and pathogens, and its clinical testing has commenced in patients with cancer. In this study we show that lethal cytokine-driven autoimmune pathology can occur in mouse models of TCR gene therapy under conditions that closely mimic the clinical setting. We show that the pairing of introduced and endogenous TCR chains in TCR gene-modified T cells leads to the formation of self-reactive TCRs that are responsible for the observed autoimmunity. Furthermore, we demonstrate that adjustments in the design of gene therapy vectors and target T cell populations can be used to reduce the risk of TCR gene therapy-induced autoimmune pathology.

BACKGROUND: Cancers are known to elude the immune system, for example, by MHC loss, FAS up-regulation, or increased secretion of TGF-beta. Recently, ligands of coinhibitory receptors like programmed cell death ligand-1 (PD-L1, B7-H1) have come to attention for their role in tumor immune escape. Various tumors have been tested for PD-L1 expression, and conflicting results were obtained regarding its correlative impact on patient survival. This study aimed to determine the prognostic relevance of PD-L1 expression for the survival of melanoma patients. METHODS: Paraffin-embedded nevi, primary melanoma, and in-transit, lymph node, and distant organ metastases from a set of 63 stages III-IV melanoma patients referred to the Netherlands Cancer Institute between 2000 and 2004 for a sentinelnode procedure or systemic therapy were studied. A large effort was invested in validating specific PD-L1 staining. In addition to immunological factors such as T-cell infiltration (CD8, CD4, and regulatory T cells), TGF-beta and MHC-I expression were assessed. RESULTS: Longitudinal analysis revealed no relevant PD-L1 expression on primary melanoma compared with metastatic disease. No significant correlations with prognosis were found regarding immunological factors, whereas known prognostic markers such as Breslow thickness and sex could be confirmed. Analyses of the overall survival of our patient cohort did not reveal a negative association with PD-L1 expression. CONCLUSIONS: Correlation of overall survival with PD-L1 expression by melanoma cells remains controversial, and future clinical studies should focus on antibody validation and time of analysis in respect to disease progression.

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