Regression of Extensive Pulmonary Metastases in Mice by Adoptive Transfer of Antigen-Specific CD8+ CTL Reactive Against Tumor Cells Expressing a Naturally Occurring Rejection Epitope

Abstract

In this study, we developed a mouse model of adoptive immunotherapy reflecting immune recognition of syngeneic tumor cells naturally expressing an endogenous rejection Ag. Specifically, in a pulmonary metastases model, we examined the potency and maintenance of an antitumor CD8+ CTL response in vivo, as well as its effectiveness against an “extensive” tumor burden. The approach taken was to first generate tumor-specific CTL from mice challenged with the CMS4 sarcoma coadministered with anti-CTLA4 mAb, which has been shown to facilitate the induction of Ag-specific T cell responses in vivo. An H-2Ld-restricted nonamer peptide, derived from an endogenous murine leukemia provirus was identified as a CMS4-reactive CTL epitope based upon the following: CTL cross-recognition of another syngeneic tumor cell line (CT26 colon carcinoma) previously characterized to express that gene product; sensitization of Ag-negative lymphoblasts or P815 targets with the peptide; and by cold target inhibition assays. In vivo, the adoptive transfer of CMS4-reactive CTL (≥1 × 106) resulted in nearly the complete regression of 3-day established lung metastases. Furthermore, mice that rejected CMS4 following a single adoptive transfer of CTL displayed antitumor activity to a rechallenge 45 days later, not only in the lung, but also at a s.c. distal site. Lastly, the adoptive transfer of CTL to mice harboring extensive pulmonary metastases (>150 nodules) led to a substantial reduction in tumor burden. Overall, these data suggest that the adoptive transfer of tumor-specific CTL may have therapeutic potential for malignancies that proliferate in or metastasize to the lung.

The Fas/Fas Ligand Pathway Is Important for Optimal Tumor Regression in a Mouse Model of CTL Adoptive Immunotherapy of Experimental CMS4 Lung Metastases

“…administration. CMS4-reactive CTL lines can be produced in mice (9) using an anti-CTLA4 mAb-based strategy (11,12). In vivo, we showed that the adoptive transfer of these CTL resulted in nearly complete regression of 3-day established experimental lung metastases, with half-maximal antitumor activity observed between 3-10 ϫ 10 4 CTL/mouse.…”

“…Furthermore, the potential relevance of the animal model would be further enriched if it were based on immune recognition of malignant cells naturally expressing tumor rejection Ag, as it would better mirror what occurs in human neoplasia. To that end, we have developed a syngeneic mouse model of CTL adoptive immunotherapy against experimental pulmonary metastases in both minimal (i.e., day 3 tumor-bearing mice) and extensive (day 10 tumor-bearing mice) disease settings (9). The model consisted of the CMS4 sarcoma, a solid tumor of BALB/c (H-2 d ) origin (10) that grows aggressively in naive, syngeneic hosts (9) either as an s.c. tumor or as a metastasis in the lung following i.v.…”

Immunogenicity and safety profiles of genetic vaccines against human Her-2/neu in cynomolgus monkeys

“…26,27 Several vaccine strategies using HLA-A2-binding Her-2/neu CTL epitope peptide were reported to be safe and effective in eliciting CTL responses even in Her-2/neu-expressing cancer patients. 28,29 However, it is difficult to directly measure CTL activity in nonhuman primates, because little information is available on MHC class I-binding epitope peptide.…”

Trafficking of tumor peptide‐specific cytotoxic T lymphocytes into the tumor microcirculation

“…Cells adhered within the first 5 min reached a maximum at 60 min [tumor vs. normal 20 (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) vs. 1 (1-2)] and were elevated for the duration of the study period. Neither population adhered to the endothelium of the normal microcirculation.…”

“…3,[17][18][19] The effector cells used in adoptive cellular therapy range from ex vivo tumor-draining lymph node cells specifically or nonspecifically activated 20 to antigen-specific CTLs reactive to tumor cells naturally expressing appropriate peptide epitopes via MHC molecules. 21 CTLs mediating MHC-restricted tumor cell killing are particularly attractive as effector cells for adoptive therapy, with the therapeutic potency being governed by their binding affinity, number and specificity.…”