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Introduction Melanoma regression, either through adoptive T cell therapy (ATT) or T cell checkpoint inhibitors blocking CTLA4 or PD-1/PD-1 ligand, correlated with increased frequencies of neoantigen-specific T cells, as deduced [...], In successful cancer immunotherapy, T cell responses appear to be directed toward neoantigens created by somatic mutations; however, direct evidence that neoantigen-specific T cells cause regression of established cancer is lacking. Here, we generated T cells expressing a mutation-specific transgenic T cell receptor (TCR) to target different immunogenic mutations in cyclin-dependent kinase 4 (CDK4) that naturally occur in human melanoma. Two mutant CDK4 isoforms (R24C, R24L) similarly stimulated T cell responses in vitro and were analyzed as therapeutic targets for TCR gene therapy. In a syngeneic HLA-A2-transgenic mouse model of large established tumors, we found that both mutations differed dramatically as targets for TCR-modified T cells in vivo. While T cells expanded efficiently and produced IFN- γ in response to R24L, R24C failed to induce an effective antitumor response. Such differences in neoantigen quality might explain why cancer immunotherapy induces tumor regression in some individuals, while others do not respond, despite similar mutational load. We confirmed the validity of the in vivo model by showing that the melan-A- specific (MART-1-specific) TCR DMF5 induces rejection of tumors expressing analog, but not native, MART-1 epitopes. The described model allows identification of those neoantigens in human cancer that serve as suitable T cell targets and may help to predict clinical efficacy.

Author(s): Thomas Kammertoens [1, 2]; Christian Friese [1, 2]; Ainhoa Arina [3]; Christian Idel [4]; Dana Briesemeister [1, 2]; Michael Rothe [1, 2]; Andranik Ivanov [5, 6]; Anna Szymborska [2]; [...]

Suicide gene therapy systems such as the herpes simplex thymidine kinase/ganciclovir system (TK/GCV) may kill cancer cells by apoptosis through as yet undefined mechanisms. Here we show that TK/GCV treatment induces p53 accumulation and increases cell surface expression of CD95 and tumor necrosis factor receptor, which is likely to involve p53-mediated translocation of CD95 to the cell surface. TK/GCV-induced apoptosis involves CD95-L-independent CD95 aggregation leading to the formation of a Fas-associated death domain protein (FADD) and caspase-8-containing, death-inducing signaling complex. Dominant negative FADD, the caspase-8 inhibitor zIETD-fmk [Z-Ile-Glu(OMe)-Thr-Asp(OMe)-fluoromethylketone], and zVAD-fmk (Z-Val-Ala-Asp-fluoromethylketone) partially abrogate TK/GCV-induced apoptosis. In addition to apoptosis induction, TK/GCV treatment strongly sensitizes for CD95-L-, TNF-, and TNF-related, apoptosis-inducing, ligand (TRAIL)induced cell death in constitutively resistant cells. These findings may be used to increase the efficacy of TK/GCV and other suicide gene therapy systems for the treatment of cancer.

In lymphopenic mice, T cells become activated and undergo lymphopenia-induced proliferation (LIP). However, not all T cells are equally sensitive to lymphopenia. Several lymphopenia-insensitive T cell clones were described and their non-responsiveness was mainly attributed to clone-specific properties. Here, we provide evidence for an additional, host-dependent mechanism restraining LIP of lymphopenia-insensitive CD4+ T cells. We show that such cells undergo LIP in lymphopenic mice lacking IFN-γ receptor (IFN-γR) expression, a process, which is promoted by the autocrine action of T cell-derived IFN-γ. Additionally, LIP of lymphopenia-insensitive CD4+ T cells requires an intact microflora and is accompanied by the massive accumulation of IL-6 and dendritic cells (DCs). Consistent with these results, IL-6 neutralization and the DC-specific restoration of IFN-γR expression are both sufficient to restrict LIP. Hence, the insensitivity of CD4+ T cells to lymphopenia relies on cell-intrinsic properties and a complex interplay between the commensal microflora, IL-6, IFN-γR+ DCs, and T cell-derived IFN-γ. [ABSTRACT FROM AUTHOR]

Stromal restraints to cancer are critical determinants of disease but they remain incompletely understood. Here, we report a novel mechanism for host surveillance against cancer contributed by fibroblast-specific protein 1 (FSP1) +/ S100A4+ firoblasts.Mechanistic studies of fibrosarcoma formation caused by subcutaneous injection of the carcinogen methylcholanthrene (MCA) had suggested that IFNγ- receptor signaling may restrict MCA g diffusion by inducing expression of collagen (foreign body reaction). We tested the hypothesis that this reaction encapsulated MCA and limited carcinogenesis by determining whether its ability to induce fibrosarcomas was impaired in the absence of proliferating fibroblasts. We found that FSP1+/S100A4+ fibroblasts accumulated around the carcinogen where they produced collagens, encapsulating MCA and protecting epithelial cells from DNA damage. Ablation of these cells at the site of MCA injection by local administration of ganciclovir in FSP-TK transgenic mice altered tumor morphology to an epithelial phenotype, indicating that, in the absence of encapsulating fibroblasts, MCA targeted epithelial cells. Notably, we showed that destruction of the fibrous capsule around the MCA by local injection of collagenase induced rapid tumor development in mice that were otherwise durably tumor free. Our findings demonstrate that the FSP1+/S100A4+ fibroblasts prevent epithelial malignancy and that collagen encapsulation of carcinogens protects against tumor development. Together, this study provides a novel mechanism for host surveillance against cancer. [ABSTRACT FROM AUTHOR]

In lymphopenic mice, T cells become activated and undergo lymphopenia-induced proliferation (LIP). However, not all T cells are equally sensitive to lymphopenia. Several lymphopenia-insensitive T cell clones were described and their non-responsiveness was mainly attributed to clone-specific properties. Here, we provide evidence for an additional, host-dependent mechanism restraining LIP of lymphopenia-insensitive CD4 + T cells. We show that such cells undergo LIP in lymphopenic mice lacking IFN-γ receptor (IFN-γR) expression, a process, which is promoted by the autocrine action of T cell-derived IFN-γ. Additionally, LIP of lymphopenia-insensitive CD4 + T cells requires an intact microflora and is accompanied by the massive accumulation of IL-6 and dendritic cells (DCs). Consistent with these results, IL-6 neutralization and the DC-specific restoration of IFN-γR expression are both sufficient to restrict LIP. Hence, the insensitivity of CD4 + T cells to lymphopenia relies on cell-intrinsic properties and a complex interplay between the commensal microflora, IL-6, IFN-γR + DCs, and T cell-derived IFN-γ.

Interleukin 4 (IL-4) was shown to be tumor-promoting in full carcinogenesis studies using 3-methylcholanthrene (MCA). Because heretofore the role of IL-4 in DMBA/TPA (9,10-dimethyl-1,2-benz-anthracene/12-O-tetradecanoylphorbol-13-acetate) two-stage carcinogenesis was not studied, we performed such experiments using either IL-4(-/-) or IL-4Rα(-/-) mice. We found that IL-4Rα(-/-) but not IL-4(-/-) mice have enhanced papilloma formation, suggesting that IL-13 may be involved. Indeed, IL-13(-/-) mice developed more papillomas after exposure to DMBA/TPA than their heterozygous IL-13-competent littermate controls. However, when tested in a full carcinogenesis experiment, exposure of mice to 25 μg of MCA, both IL-13(-/-) and IL-13(+/-) mice led to the same incidence of tumors. While IL-4 enhances MCA carcinogenesis, it does not play a measurable role in our DMBA/TPA carcinogenesis experiments. Conversely, IL-13 does not affect MCA carcinogenesis but protects mice from DMBA/TPA carcinogenesis. One possible explanation is that IL-4 and IL-13, although they share a common IL-4Rα chain, regulate signaling in target cells differently by employing distinct JAK/STAT-mediated signaling pathways downstream of IL-13 or IL-4 receptor complexes, resulting in different inflammatory transcriptional programs. Taken together, our results indicate that the course of DMBA/TPA- and MCA-induced carcinogenesis is affected differently by IL-4 versus IL-13-mediated inflammatory cascades., (© 2013 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.)

It is thought that tumor rejection by CD8(+) T-cell effectors is primarily mediated by direct killing. We show that rejection of different tumors (fibrosarcoma, ras-transformed fibroblasts, colon carcinoma, and plasmacytoma) by CD8(+) T cells is always preceded by inhibition of tumor-induced angiogenesis. Angiostasis and tumor rejection were observed in perforin but not in IFN-gamma-deficient mice. Furthermore, adoptive transfer of tumor-specific CD8(+) T cells from IFN-gamma-competent mice inhibited angiogenesis of lung metastases in comparison to those from IFN-gamma gene-deficient mice. Taken together with our previous findings, we conclude that IFN-gamma-dependent antiangiogenesis is a general mechanism involved in tumor rejection by CD4(+) and CD8(+) T-cell effectors.