Abstract B092: Tumor infiltrating T-cells from renal cell carcinoma patients recognize neoantigens derived from point and frameshift mutations

Mutation-derived neoantigens are important targets of T-cell mediated reactivity towards tumors. Their unique tumor-restriction poses an advantage compared to shared tumor antigens in that they are in principle both foreign and tumor specific, hence presumably less impacted by T-cell tolerance and for therapeutic applications less prone to mediate immune-related destruction of noncancerous tissue. Moreover, the mutational burden and predicted number of neoantigens correlate to favorable clinical outcome and benefit from immune checkpoint therapy. Neoantigen-reactive T-cells have been detected across a number of solid cancers, ranging from immunogenic tumors such as melanoma and non-small cell lung cancer to less immunogenic tumors such as breast cancer. Renal cell carcinomas (RCCs) are among medium-range mutational burden tumors and present with the highest pan-cancer number and proportion of frameshift mutations, a mutation type considered to be highly immunogenic. However, to our knowledge, yet no reports have described neoantigen-specific T-cells in this malignancy. In this study, the mutational landscape and HLA (human leukocyte antigen) profile of tumors from six renal cell carcinoma patients were analyzed by whole-exome sequencing (WXS) of DNA from tumor fragments (TFs), autologous tumor cell lines (TCLs) and tumor-infiltrating lymphocytes (TILs, germline reference). Hereafter the online MuPeXi tool was used to predict binding of mutated peptide sequences of 9-11mer length to the HLAs of each patient, using a rank score < 2 for selection of peptide binding, hereby creating patient-specific libraries of putative neo-peptides. TILs extracted from the patients tumors were screened for T-cell recognition of the peptide libraries by use of a novel high-throughput platform based on DNA barcode labeled peptide-MHC multimers, and responses were verified by conventional fluorochrome labeled MHC multimers. In four of six patients WXS was performed on both TF and TCL, in two of six patients only on TF. The average mutational burden of the six patients was 271 for TF (range 146–381, n=6) and 289 for TCL (range 182-404, n=4). Prediction of HLA-restricted peptides within the mutated sequences resulted in patient specific libraries of average 269 peptides for TF and TCL combined (range 126-443, n=6). Half of the peptides were predicted from both sources (52%, range 28-74%, n=4) compared to 20% (range 8-31%, n=4) predicted solely from TF and 29% (range 18-41%, n=4) predicted solely from TCL. The proportion of predicted peptides derived from frameshift mutations out of total mutations was 16% (range 7-24%, n=6). A total of 67 neoantigen-specific T-cell responses were detected across all patients by use of a novel high-throughput DNA barcode screening platform, with the number of detected responses ranging from 4-30 and spanning 3-5 HLA restrictions per patient. Of note, we detected a number of T-cell responses towards HLA-C restricted peptides, which have previously been poorly described. For several patients, the number of HLA-C restricted T-cell responses observed was substantially higher than for both HLA-A and -B, highlighting the importance of including this HLA type for neoepitope analyses. In the four patients in whom peptides were predicted from both TF and TCL, the distribution of responses was 37% on TF (range 14-60%, n=4), 36% on TCL (range 29-43%, n=4) and 27% (range 0-43%) on TF+TCL combined. The proportion of responses towards frameshift mutations was 17% (range 0-24%, n=6) of total responses. The identification of neoantigen-specific T-cells within tumors from RCC patients is an important step towards the use of neoantigens as therapeutic targets and predictors of response to immunotherapy in this cancer subtype. Moreover, our study points toward the importance of broad peptide prediction platforms covering multiple sources for WXS and mutational analyses covering both point and frameshift mutations.

Citation Format: Sofie Ramskov, Ulla Kring Hansen, Anne-Mette Bjerregaard, Amalie Kai Bentzen, Marco Donia, Rikke Andersen, Zoltan Szallasi, Inge Marie Stentoft Svane, Aron Charles Eklund, Sine Reker Hadrup. Tumor infiltrating T-cells from renal cell carcinoma patients recognize neoantigens derived from point and frameshift mutations [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B092.

Abstract B039: Peptide-MHC-directed expansion of multifunctional antigen-responsive T-cells

Functional properties and antigen specificity of expanded T-cells are crucial for the efficacy of adoptive cell transfer-based therapies in cancer. Most current strategies involve nonspecific expansion of bulk tumor-infiltrating lymphocytes, often providing growth preference to co-infiltrated virus specific T-cells and driving an exhausted phenotype of the expanded T-cell product.A potential way to resolve this challenge, is the use of artificial antigen-presenting scaffolds providing both an antigen specific stimulation through peptide-MHC interaction and additional the required co-stimulatory and growth signals through associated stimulatory molecules and cytokines. We have designed such antigen-presenting scaffolds; build on a dextran-polysaccharide, carrying both peptide-MHC and relevant stimulatory molecules. The artificial antigen-presenting scaffolds interacts specifically with T-cells based on recognition of the peptide-MHC molecule and effectively expand and functionally stimulate specific T-cells in a peptide-MHC-directed fashion, while leaving all other T-cell specificities untouched. Results from in vitro experiments have showed that antigen specific CD8 T-cells stimulated with these artificial antigen-presenting scaffolds express a less differentiated phenotype and low PD-1 expression, associated with high proliferation potential and enhanced antitumor effect in vivo. Furthermore, this expansion strategy provides a high frequency of multifunctional antigen specific CD8 T-cells expressing IFN-γ, TNF-α, and CD107a upon target recognition and provide improved cancer cell killing over IL2-driven expansion of tumor-infiltrating lymphocytes. Furthermore, the current strategy allows for simultaneous expansion of numerous different T-cell populations, required to generate T-cell products with broad recognition profiles based on the personal cancer-antigen and mutational profile. All of these characteristics are of significant importance for in vivo tumor cell killing following adoptive transfer of expanded T-cell products. Thus, the present strategy represents an optimized method for expansion of cancer-restricted T-cells for adoptive cell therapy.

Citation Format: Vibeke Mindahl Rafa, Mona Bodenhöfer, Amalie Kai Bentzen, Tripti Tamhane, Marco Donia, Inge Marie Stentoft Svane, Søren Nyboe Jakobsen, Christian Schmess, Sine Reker Hadrup. Peptide-MHC-directed expansion of multifunctional antigen-responsive T-cells [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B039.

Abstract A079: Secreted IL-12p70 from long-term activated dendritic cells is lost concomitant with their apoptosis and release of IL-10

The intimate balance between peripheral tolerance and adaptive immunity has profound implications in several disease settings. Interleukin-12 (IL-12) plays a major role in immunity to intracellular pathogens and cancer by controlling IFNγ-dependent adaptive immunity. The transient production of the bioactive IL-12p70 heterodimer and the concurrent expression of interleukin-10 (IL-10) serves as a myeloid checkpoint to avoid immunopathology. Here, long-term exposure to inflammatory stimuli was evaluated on monocyte-derived dendritic cells (DCs) activated with lipopolysaccharide (LPS) and gamma interferon (IFNγ). The secretion of IFNγ from co-cultures with allogeneic T-cells present in peripheral blood mononuclear cells from healthy volunteers served as a measure of T-cell activation.The secretion of IFNγ from co-cultures was progressively lost as exposure of DCs to inflammatory stimuli was extended from one up to four days prior to co-culture or following IL-12p70 antibody-mediated blockade. Most pronounced was the 12-fold reduction (N = 9 donor pairs) seen with four-day activated DCs. Furthermore, at four days of activation, a significant fraction of DCs underwent apoptosis concomitant with their increased release of IL-10 and a striking 10-fold drop in levels of IL-12p70 as compared with DCs activated one, two or three days. Furthermore, after four days of activation, DC-derived IL-12p70 was inversely correlated with IL-10 and with IFNγ derived from co-cultures. It is currently an open question whether IL-12p70 naturally degrades after four days of activation or whether apoptotic DCs actively stimulate the degradation of IL-12p70.

Citation Format: Morten Hansen, Laura Stentoft Carstensen, Andreas Obers, Inge Marie Stentoft Svane. Secreted IL-12p70 from long-term activated dendritic cells is lost concomitant with their apoptosis and release of IL-10 [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A079.

Abstract B154: Differential effects of corticosteroids and anti-TNF on tumor-specific immune responses— Implications for the management of irAEs

Background: Up to 60% of patients treated with cancer immunotherapy develop severe or life threatening immune-related adverse events (irAEs). Immunosuppression with high doses of corticosteroids or, in refractory cases, with tumor necrosis factor (TNF) antagonists, are the mainstay of treatment for irAEs. It is currently unknown what is the impact of corticosteroids and anti-TNF on the activity of antitumor T-cells. Methods: The influence of clinically relevant doses of dexamethasone (corresponding to an oral dose of 10 to 125 mg prednisolone) and infliximab (anti-TNF) on the activation and killing capacity of tumor-infiltrating lymphocytes (TILs) was tested in vitro. Results: Overall, dexamethasone at low or intermediate/high dose impaired the activation (respectively -46% and -62% in n=8) and tumor-killing ability (respectively -48% and -53% in n=6) of tumor-specific TILs. In contrast, a standard clinical dose of infliximab only had a minor effect on T-cell activation and tumor killing (respectively -20% in n=8 and -10% in n=6). A brief resting following exposure to dexamethasone was sufficient to rescue the in vitro activity of TILs. Conclusions: Clinically relevant doses of infliximab only influenced to a lesser extent the activity of tumor-specific TILs in vitro, whereas even low doses of corticosteroids markedly impaired the antitumor activity of TILs. These data support steroid-sparing strategies and early initiation of anti-TNF for the treatment of irAEs in immuno-oncology.

Citation Format: Marco Donia, Troels H. Borch, Haja D. Radic, Christopher Chamberlain, Aishwarya Gokuldass, Inge Marie Stentoft Svane, Arianna Draghi. Differential effects of corticosteroids and anti-TNF on tumor-specific immune responses— Implications for the management of irAEs [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B154.