ILT3.Fc–CD166 Interaction Induces Inactivation of p70 S6 Kinase and Inhibits Tumor Cell Growth

Abstract

The blockade of immune checkpoints by anti-receptor and/or anti-ligand mAb is one of the most promising approaches to cancer immunotherapy. The interaction between Ig-like transcript 3 (ILT3), a marker of tolerogenic dendritic cells, also known as LILRB4/LIR5/CD85k, and its still unidentified ligand on the surface of activated human T cells is potentially important for immune checkpoint blockade. To identify the ILT3 ligand, we generated mAb by immunizing mice with Jurkat acute T cell leukemia, which binds ILT3.Fc to its membrane. Flow cytometry, mass spectrometry, and Biacore studies demonstrated that the ILT3 ligand is a CD166/activated leukocyte cell adhesion molecule. Knockdown of CD166 in primary human T cells by nucleofection abolished the capacity of ILT3.Fc to inhibit CD4 T cell proliferation and to induce the generation of CD8CD28 T suppressor cells. CD166 displays strong heterophilic interaction with CD6 and weaker homophilic CD166-CD166 cell adhesion interaction. ILT3.Fc inhibited the growth of CD166 tumor cell lines (TCL) derived from lymphoid malignancies in vitro and in vivo. CRISPR-Cas9-based knockout of CD166 from TCL abrogated ILT3.Fc binding and its tumor-inhibitory effect. The mechanism underlying the effect of ILT3.Fc on tumor cell growth involves inhibition of the p70S6K signaling pathway. Blockade of CD166 by ILT3.Fc inhibited progression of human TCL in NOD.Cg-Prkdc Il-2rg/SzJ mice, suggesting its potential immunotherapeutic value.

Multifaceted effects of soluble human CD6 in experimental cancer models

“…Similar to shCD6, chimeric soluble ILT3 (ILT3.Fc) inhibited in vitro T cell proliferation and differentiation to Treg, and also tumor cell growth and migration in an ALCAM-dependent manner cells. 27 These observations support the targeting of ALCAM for immunotherapeutic purposes in cancer. On this basis, we tested the efficacy of sustained smCD6 delivery by means of AAV-based gene transfer-a successful strategy in several preclinical models and in recent clinical cancer trials.…”

“…in vitro tumor cell growth and migration assays Tumor cell proliferation was monitored as reported elsewhere. 27 Wound healing technique was used to assess tumor cell migration. 28 on October 12, 2020 by guest.…”

“…41 48-51 The contribution of ALCAM to tumor progression through the fine-tuning of homophilic adhesive cell-to-cell interactions between cancer cells and with stromal and/ or endothelial cells has been reported. 34 48 However, heterophilic ALCAM interactions with Gal-1, Gal-3 and Gal-8 5 52 or the Ig-like transcript 3 (ILT3)-an inhibitory receptor expressed by cells of myelomonocytic origin and a marker of tolerogenic dendritic cells 27 -may also play a role. Similar to shCD6, chimeric soluble ILT3 (ILT3.Fc) inhibited in vitro T cell proliferation and differentiation to Treg, and also tumor cell growth and migration in an ALCAM-dependent manner cells.…”

Phagocytosis checkpoints as new targets for cancer immunotherapy

“…Anti-LILRB4 antibodies reactivate T cells and blocked development of monocytic leukemia. 77 Although it was demonstrated that ApoE binding can activate LILRB4, 77 and LILRB4 interaction with CD166 mediates its inhibitory effect on tumor cells, 85 further investigations are needed to clarify whether LILRB4 on monocytic cells can directly bind and act on a surface protein (ideally an immune inhibitory receptor) on T cells.…”

The Role of Osteomacs in Regulating Stem Cell Function and the Hematopoietic Niche

“…It is capable of mediating both CD166-CD166 homophilic interactions as well as heterophilic interactions with CD6 (Degen, van Kempen et al 1998). Recently, CD85k has been identified as a ligand which binds to CD166 and in turn blocks tumor growth in CD166+ tumor cell lines (Xu, Chang et al 2018). In hematopoiesis, CD166 is an important functional marker of HSC and is critical for the competence of the niche , Chitteti, Cheng et al 2013, Chitteti, Kobayashi et al 2014.…”