EP4 Antagonism by E7046 diminishes Myeloid immunosuppression and synergizes with Treg-reducing IL-2-Diphtheria toxin fusion protein in restoring anti-tumor immunity

Abstract

Reprogramming of immunosuppressive tumor microenvironment (TME) by targeting alternatively activated tumor associated macrophages (M2TAM), myeloid-derived suppressor cells (MDSC), and regulatory T cells (Tregs), represents a promising strategy for developing novel cancer immunotherapy. Prostaglandin E2 (PGE2), an arachidonic acid pathway metabolite and mediator of chronic inflammation, has emerged as a powerful immunosuppressor in the TME through engagement with one or more of its 4 receptors (EP1-EP4). We have developed E7046, an orally bioavailable EP4-specific antagonist and show here that E7046 has specific and potent inhibitory activity on PGE2-mediated pro-tumor myeloid cell differentiation and activation. E7046 treatment reduced the growth or even rejected established tumors in vivo in a manner dependent on both myeloid and CD8+ T cells. Furthermore, co-administration of E7046 and E7777, an IL-2-diphtheria toxin fusion protein that preferentially kills Tregs, synergistically disrupted the myeloid and Treg immunosuppressive networks, resulting in effective and durable anti-tumor immune responses in mouse tumor models. In the TME, E7046 and E7777 markedly increased ratios of CD8+granzymeB+ cytotoxic T cells (CTLs)/live Tregs and of M1-like/M2TAM, and converted a chronic inflammation phenotype into acute inflammation, shown by substantial induction of STAT1/IRF-1 and IFNγ-controlled genes. Notably, E7046 also showed synergistic anti-tumor activity when combined with anti-CTLA-4 antibodies, which have been reported to diminish intratumoral Tregs. Our studies thus reveal a specific myeloid cell differentiation-modifying activity by EP4 blockade and a novel combination of E7046 and E7777 as a means to synergistically mitigate both myeloid and Treg-derived immunosuppression for cancer treatment in preclinical models.

Role of prostanoids in gastrointestinal cancer

“…Therefore, deletion of EP4 in myeloid cells resulted in a reduction of tumor burden in Apc Min/+ mice (130). An EP4 antagonist, E7046, has also been shown to shift TAMs from M2 to M1 macrophages and to enhance the antitumor effect of anti-CTLA-4 antibodies in syngeneic murine models of cancer (103). In vitro studies showed that PGE 2 promoted M2 macrophage polarization via a CREB/CRTC pathway in bone marrow-derived macrophages (131) and eliminates CD8 + T cells by inducing PD-L1 expression in TAMs (106).…”

“…Moreover, PGE 2 promoted tumor progression via inducing the development of MDSCs from bone marrow myeloid progenitor cells, whereas inhibition of PGE 2 signaling by deletion of EP2 or its antagonists blocked this differentiation in mice with implanted 4T1 murine mammary carcinoma tumors (102). An EP4 antagonist, E7046, has been shown to reduce tumor-infiltrating MDSCs and to enhance the antitumor effect of anti-CTLA-4 antibodies in syngeneic mouse models of cancer (103), indicating that EP4 mediates the effect of PGE 2 on MDSCs. An in vitro study showed that PGE 2 blocked differentiation of monocytes into DCs and promoted MDSC development (104).…”

Modulation of the secretion of mesenchymal stem cell immunoregulatory factors by hydrolyzed fish collagen

“…6A) (30). EP4 is the receptor for PGE2, an important transmembrane G protein-coupled receptor in macrophages (31). The results of the RT-qPCR analysis demonstrated that HFC-induced BMSCs significantly increased the expression levels of EP4 mRNA compared with RAW264.7 alone.…”

Prostaglandin E2/EP Signaling in the Tumor Microenvironment of Colorectal Cancer

“…Zhang et al also demonstrated that the expression of the M2 phenotype marker, Ym1, was decreased in the myeloid-specific EP4 knockout mice [52]. Albu et al reported that the EP4 antagonist, E7046, reduced M2-like macrophages [53]. Barminko et al also reported that EP4 signaling could induce the transition from M1 to M2 phenotype [54].…”