A conjugate of octamer-binding transcription factor 4 and toll-like receptor 7 agonist prevents the growth and metastasis of testis embryonic carcinoma.

Guimiao Lin,Xiaomei Wang,Gaixia Xu,Wanxian Yi,Marie Chia-Mi Lin,Guangyi Jin,Zhiming Cai,Chuanxia Zhang,Xiaomei Zhu,Yuwen Diao,Yu Liu

doi:10.1186/s12967-015-0524-y

Abstract

BackgroundThe immune non-recognition is often the underlying cause of failure in tumor immunotherapeutic. This is because most tumor-related antigens are poorly immunogenic, and fail to arouse an efficient immune response against cancers. Here we synthesized a novel TLR7 agonist, and developed a safe and effective immunotherapeutic vaccine by conjugating this TLR7 agonist with the pluripotency antigen OCT4.MethodsPurified recombinant OCT4 protein was covalently linked with a novel TLR7 agonist to form a TLR7-OCT4 conjugate (T7-OCT4). After conjugation, the in vitro release of IL-12 and IFN-γ was observed in spleen lymphocytes. Mice were immunized with TLR7-OCT4, and the release of IFN-γ, the percentages of CD3+/CD8+ T cells and the OCT4-specific cytotoxicity rates were measured. The immunized mice were challenged with mouse embryonic carcinoma (EC), and the tumor volume and tumor weight were determined. Blood routine examination was performed to evaluate the biosafety of TLR7 agonist and TLR7-OCT4 conjugate in mice.ResultsT7-OCT4 conjugate significantly increased the in vitro release of IL-12 and IFN-γ by mouse spleen lymphocytes. In addition, the release of IFN-γ, the percentages of CD3+/CD8+ T cells and the tumor-specific cytotoxicity rates in immunized mice were significantly higher. Importantly, in EC xenografted mice, immunization with T7-OCT4 conjugate decreased the growth of the tumor dramatically up to 90 %, as compared to mice immunized with OCT4 protein or TLR7 agonist alone. Furthermore, blood routine examination demonstrated that no abnormalities of the blood cells and components in the blood fluids were detected by T7-OCT4 and TLR7 agonist injections.ConclusionsOur results showed that conjugating OCT4 protein to the novel TLR7 agonist produced a vaccine which is effective and safe in preventing tumor growth in mice. Our results suggest that this type of vaccine formulation has great potentiality in preventive vaccines against OCT4 expressing tumors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0524-y) contains supplementary material, which is available to authorized users.

Highlights

The immune non-recognition is often the underlying cause of failure in tumor immunotherapeutic
Conjugation of TLR7 agonist to recombinant OCT4 protein TLR7 agonist (T7) could be coupled to proteins and peptides antigens through the amide banding commonly used in peptide chemistry
OCT4 and T7 + OCT4 did not cause significant change in IL-12 at concentrations of 0.1 μM and 0.5 μM, and did not cause significant change in IFNγ release at concentrations of 0.1 μM, OCT4 and T7 + OCT4 at 1.0 μM caused a significant increase of IL12 (p < 0.01) and IFN- γ (p < 0.0001) release. This is possibly due to the non-specific immune response caused by high concentration of OCT4 antigen. These results suggested that TLR7-OCT4 conjugate (T7-OCT4) at the concentrations of 0.1-1.0 μM could effectively stimulate lymphocytes immune response

Summary

Introduction

The immune non-recognition is often the underlying cause of failure in tumor immunotherapeutic. This is because most tumor-related antigens are poorly immunogenic, and fail to arouse an efficient immune response against cancers. OCT4 (Octamer-binding transcription factor 4), known as POU5F1, is a member of the mammalian POU family of transcriptional factors. It functions as a key regulator of the self-renewal and pluripotency of embryonic stem (ES) cells [1]. OCT4 has been reported to be highly expressed in many tumors, such as carcinomas of breast [2], testis, bladder [3], germ-cell tumors, and in cancer stem cells [4]. OCT4 is highly expressed in tumor cells, but is either absent or at very low level in a variety of normal cells [8], indicating that it is a potential tumor stem cell biomarker and an ideal target in cancer therapy [9]

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Results

Conclusion