Abstract 3227: Differential expression of T cell co-inhibitory receptors: KLRG1 alignment with cytotoxicity and adaptive resistance mechanisms

Introduction: KLRG1 is a lymphocyte co-inhibitory, or immune checkpoint, receptor expressed predominantly on late-differentiated effector and effector memory CD8+ T and NK cells.

Methods: We studied KLRG1 expression in human blood and tumor samples from available genomic datasets.

Results: KLRG1 is differentially expressed from CTLA-4 and PD-1, with predominant expression on cytotoxic CD8 T and NK cells over CD4 T cells. Within the CD8+ T cell population, KLRG1 expression, unlike CTLA-4 and PD-1 expression, is linked to greater antigen-driven differentiation states, with increased expression on CD45RO+CCR7- T effector memory (TEM) and CD45RA+CCR7- T effector memory RA (TEMRA) cells compared to CD45RA+CCR7+ naïve T cells (TN) and CD45RO+CCR7+ central memory T cells (TCM). The cytotoxic potential of CD8+ T cells, as assessed by the presence of cytokine and cytotoxic molecules IFNg, TNFa, perforin and granzyme B, is aligned with KLRG1, but not CTLA-4 or PD-1, expression. In single cell RNAseq analyses, KLRG1+ TILS accounted for 16-48% of CD8+ TILS, a frequency similar to that of PD-1+ TILS, in renal cell carcinoma, hepatocellular carcinoma, melanoma, ovarian cancer, HNSCC, and astrocytoma. KLRG1 expression was numerically increased post-treatment in 20/21 (95%) of datasets, statistically significant in 10/21 (48%), in response to a range of treatments including radiotherapy, chemotherapy, endocrine therapy, and immunotherapies (including ipilimumab, nivolumab, and pidilizumab), over periods of time ranging from 1-25 weeks.

Conclusions: In human blood and tumor samples, KLRG1 expression is aligned with cytotoxic T and NK cell differentiation, and upregulated in human tumor samples after a variety of therapies, potentially contributing to adaptive resistance. The upregulation of KLRG1 could contribute to limited efficacy and adaptive resistance that develops with current immunotherapies, and suggests KLRG1 blockade may work efficaciously, including as a neo-adjuvant therapy.

Citation Format: Steven A. Greenberg, Evan Thompson, Stefano V. Gulla. Differential expression of T cell co-inhibitory receptors: KLRG1 alignment with cytotoxicity and adaptive resistance mechanisms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3227.

Co-inhibitory T cell receptor KLRG1: human cancer expression and efficacy of neutralization in murine cancer models

Background

KLRG1 is a lymphocyte co-inhibitory, or immune checkpoint, receptor expressed predominantly on late-differentiated effector and effector memory CD8+ T and NK cells. Targeting of KLRG1 neutralization in murine cancer models has not previously been reported.

Methods

We studied KLRG1 expression in human blood and tumor samples from available genomic datasets. Anti-KLRG1 neutralizing antibody was studied in the murine 4T1 breast cancer as monotherapy, and in the MC38 colon cancer and B16F10 melanoma models as combination therapy with anti-PD-1 antibody.

Results

In human blood and tumor samples, KLRG1 expression is aligned with cytotoxic T and NK cell differentiation, and upregulated in human tumor samples after a variety of therapies, potentially contributing to adaptive resistance. In in vivo murine models, anti-KLRG1 antibody monotherapy in the 4T1 breast cancer model reduced lung metastases (decreased lung weights p=0.04; decreased nodule count p=0.002), while anti-KLRG1 + anti-PD-1 combination therapy in the MC38 colon cancer and B16F10 melanoma models produced synergistic benefit greater than anti-PD-1 alone for tumor volume (MC38 p=0.01; B16F10 p=0.007) and survival (MC38 p=0.02; B16F10 p=0.002).

Conclusions

These studies provide the first evidence that inhibition of the KLRG1 pathway enhances immune control of cancer in murine models, and provide target validation for KLRG1 targeting of human cancer. The mechanism of efficacy of KLRG1 blockade in murine models remains to be determined.

Abstract LB-301: Inhibition of the co-inhibitory receptor KLRG1 reduces murine 4T1 breast cancer metastasis and MC38 colon cancer primary tumor growth and mortality

Introduction

Targeting of lymphocyte co-inhibitory receptors, such as CTLA-4, PD-1, Lag-3, and Tim-3, has gained intense interest for treatment of cancer. KLRG1 is also a lymphocyte co-inhibitory receptor, expressed predominantly on effector memory CD8+ T cells and NK cells, whose ligands E- and N-cadherin are differentially expressed during epithelial-mesenchymal transition. Targeting of KLRG1 in murine cancer models has not previously been published.

Methods

We constructed an anti-mouse KLRG1 antibody that neutralized the interaction of KLRG1 with its ligands. Anti-KLRG1 antibody was administered as a monotherapy in a murine metastatic tumor model (4T1 murine breast cancer) and as combination therapy with anti-PD-1 (clone RMP1-14) in a murine primary tumor growth model (MC38 murine colon cancer).

Results

In the 4T1 murine breast cancer model, anti-KLRG1 antibody reduced lung metastases compared to control antibody as measured by mean lung weights (0.28 g vs. 0.47 g; p=0.04) and nodule count (10.7 vs. 30.1; p=0.002). In the MC38 model, primary tumor growth was inhibited by anti-KLRG1 + anti-PD-1 antibody greater than anti-KLRG1 antibody or anti-PD-1 antibody or control antibody (day 13 tumor volume 582 vs. 1259 vs. 1279 vs. 1461 mm3, respectively). Combination therapy anti-KLRG1 + anti-PD-1 produced synergistic benefit significantly greater than that of anti-PD-1 alone for tumor volume (p=0.01) and survival (p=0.02; day 18 survival 60% of mice alive treated with combination therapy compared to 0% alive treated with anti-PD-1 alone). Ex vivo KLRG1 blockade with anti-human KLRG1 antibodies resulted in human CD8+ T cell proliferation and proinflammatory cytokine secretion.

Conclusions

Anti-KLRG1 neutralizing antibody demonstrates efficacy in inhibiting metastases in the murine 4T1 breast cancer model and reducing primary tumor volume and improving survival as synergistic combination therapy with anti-PD-1 in the murine MC38 colon cancer model. Anti-KLRG1 blockade with anti-human KLRG1 antibodies results in activation of CD8+ T cells. These data suggest that anti-KLRG1 treatment is a promising new approach for cancer immunotherapy.

Citation Format: Steven A. Greenberg, Stefano V. Gulla, Evan Thompson. Inhibition of the co-inhibitory receptor KLRG1 reduces murine 4T1 breast cancer metastasis and MC38 colon cancer primary tumor growth and mortality [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-301.

Dynamic conformational responses of a human cannabinoid receptor-1 helix domain to its membrane environment

The influence of membrane environment on human cannabinoid 1 (hCB(1)) receptor transmembrane helix (TMH) conformational dynamics was investigated by solid-state NMR and site-directed spin labeling/EPR with a synthetic peptide, hCB(1)(T377-E416), corresponding to the receptor's C-terminal component, i.e., TMH7 and its intracellular alpha-helical extension (H8) (TMH7/H8). Solid-state NMR experiments with mechanically aligned hCB(1)(T377-E416) specifically (2)H- or (15)N-labeled at Ala380 and reconstituted in membrane-mimetic dimyristoylphosphocholine (DMPC) or 1-palmitoyl-2-oleoyl-sn-glycerophosphocholine (POPC) bilayers demonstrate that the conformation of the TMH7/H8 peptide is more heterogeneous in the thinner DMPC bilayer than in the thicker POPC bilayer. As revealed by EPR studies on hCB(1)(T377-E416) spin-labeled at Cys382 and reconstituted into the phospholipid bilayers, the spin label partitions actively between hydrophobic and hydrophilic environments. In the DMPC bilayer, the hydrophobic component dominates, regardless of temperature. Mobility parameters (DeltaH(0)(-1)) are 0.3 and 0.73 G for the peptide in the DMPC or POPC bilayer environment, respectively. Interspin distances of doubly labeled hCB(1)(T377-E416) peptide reconstituted into a TFE/H(2)O mixture or a POPC or DMPC bilayer were estimated to be 10.6 +/- 0.5, 16.8 +/- 1, and 11.6 +/- 0.8 A, respectively. The extent of coupling (>or=50%) between spin labels located at i and i + 4 in a TFE/H(2)O mixture or a POPC bilayer is indicative of an alpha-helical TMH conformation, whereas the much lower coupling (14%) when the peptide is in a DMPC bilayer suggests a high degree of peptide conformational heterogeneity. These data demonstrate that hCB(1)(T377-E416) backbone dynamics as well as spin-label rotameric freedom are sensitive to and altered by the peptide's phospholipid bilayer environment, which exerts a dynamic influence on the conformation of a TMH critical to signal transmission by the hCB(1) receptor.