A composite MyD88/CD40 switch synergistically activates mouse and human dendritic cells for enhanced antitumor efficacy

Abstract

The in vivo therapeutic efficacy of DC-based cancer vaccines is limited by suboptimal DC maturation protocols. Although delivery of TLR adjuvants systemically boosts DC-based cancer vaccine efficacy, it could also increase toxicity. Here, we have engineered a drug-inducible, composite activation receptor for DCs (referred to herein as DC-CAR) comprising the TLR adaptor MyD88, the CD40 cytoplasmic region, and 2 ligand-binding FKBP12 domains. Administration of a lipid-permeant dimerizing ligand (AP1903) induced oligomerization and activation of this fusion protein, which we termed iMyD88/CD40. AP1903 administration to vaccinated mice enabled prolonged and targeted activation of iMyD88/CD40-modified DCs. Compared with conventionally matured DCs, AP1903-activated iMyD88/CD40-DCs had increased activation of proinflammatory MAPKs. AP1903-activated iMyD88/CD40-transduced human or mouse DCs also produced higher levels of Th1 cytokines, showed improved migration in vivo, and enhanced both antigen-specific CD8 + T cell responses and innate NK cell responses. Furthermore, treatment with AP1903 in vaccinated mice led to robust antitumor immunity against preestablished E.G7-OVA lymphomas and aggressive B16.F10 tumors. Thus, the iMyD88/ CD40 unified "switch" effectively and safely replaced exogenous adjuvant cocktails, allowing remote and sustained DC activation in vivo. DC "licensing" through iMyD88/CD40 may represent a mechanism by which to exploit the natural synergy between the TLR and CD40 signaling pathways in DCs using a single small molecule drug and could augment the efficacy of antitumor DC-based vaccines.

Strategies for enhancing adoptive T-cell immunotherapy against solid tumors using engineered cytokine signaling and other modalities

“…An alternative, but similar approach keeps the signaling molecules separate, with only costimulatory signaling regulated with a dimerizing small molecule drug [99]. In this strategy, T-cells express a CAR with a zeta endodomain engineered to recognize the PSCA receptor and co-express a separate molecule comprising MyD88 and CD40 endodomains linked to FKBP12 ligand-binding domains [100]. When the inducer drug AP1903 is added, the MyD88/CD40 domain oligomerizes and successfully signals to produce costimulation [101].…”

Cancer Vaccination, Will You Have To Pay The Toll?

“…These results demonstrate that TLR4 activation by HBHA is important in the E.G7 thymoma model, and that both MyD88 and TRIF arms were necessary. In support of this result, another study by Narayanan et al, utilizing an E.G7-OVA lymphoma model, showed that MyD88 and CD40 signaling were required for DC-dependent antitumor activity [36].…”

Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer

“…MyD88 is an adapter protein used by TLR7 and TLR9, as well as most TLRs, to activate the NF-κB pathway. MyD88 has been proposed to be a rate-limiting component during TLR stimulation (Narayanan et al 2011). In agreement with our results, a report indicates that dual stimulation of MyD88-dependent TLR pathways can result in impaired activation of NF-κB in murine BM-derived macrophages (Bagchi et al 2007).…”