Ubiquitin-modified hepatitis B virus core antigen effectively facilitates antigen presentation and enhances cytotoxic T lymphocyte activity via the cytoplasmic transduction peptide in vitro

Ubiquitin: A double-edged sword in hepatitis B virus-induced hepatocellular carcinoma

Hepatitis B virus is one of the leading causes behind the neoplastic transformation of liver tissue and associated mortality. Despite the availability of many therapies and vaccines, the pathogenic landscape of the virus remains elusive; urging the development of novel strategies based on the fundamental infectious and transformative modalities of the virus-host interactome. Ubiquitination is a widely observed post-translational modification of several proteins, which either regulates the proteins' turnover or impacts their functionalities. In recent years, ample amount of literature has accumulated regarding the ubiquitination dynamics of the HBV proteins as well as the host proteins during HBV infection and carcinogenesis; with direct and detailed characterization of the involvement of HBV in these processes. Interestingly, while many of these ubiquitination events restrict HBV life cycle and carcinogenesis, several others promote the emergence of hepatocarcinoma by putting the virus in an advantageous position. This review sums up the snowballing literature on ubiquitination-mediated regulation of the host-HBV crosstalk, with special emphasis on its influence on the establishment and progression of hepatocellular carcinoma on a molecular level. With the advent of cutting-edge ubiquitination-targeted therapeutic approaches, the findings emanating from this review may potentiate the identification of novel anti-HBV targets for the formulation of novel anticancer strategies to control the HBV-induced hepato-carcinogenic process on a global scale.

Effect of CTP-mediated PTEN on 5637 bladder cancer cells and the underlying molecular mechanism

OBJECTIVE

The aim of the present study was to explore the effect of cytoplasmic transduction peptide (CTP)-phosphatase and tensin homolog (PTEN) on the proliferation, cell cycle, apoptosis, migration and invasion of bladder cancer cells and the underlying molecular mechanism.

METHODS

A eukaryotic expression vector, pTT5-CTP-PTEN, was constructed. The constructed vector was transfected into HEK 293-6E cells to express a fusion protein, CTP-PTEN. The fusion protein was purified. 5637 bladder cancer cells were cocultured with purified CTP-PTEN fusion protein. Target gene expression, protein expression, cell proliferation, cell cycle, apoptosis, cell invasion and cell migration were examined by reverse transcription polymerase chain reaction (RT-PCR), western blot, MTT assay, flow cytometry, Transwell assay, and cell scratch assay, respectively.

RESULTS

Both PTEN and CTP-PTEN fusion protein inhibited the proliferation, cell cycle, invasion and migration of bladder cancer cells and promoted the apoptosis of bladder cancer cells. The effect of CTP-PTEN was more significant.

CONCLUSIONS

The fused expression of CTP and PTEN significantly increased the penetrability of the tumor suppressor gene PTEN into cancer cells. The CTP-PTEN fusion protein exhibited a significant carcinostatic effect on 5637 bladder cancer cells.

Feasibility of dendritic cell-based vaccine against glioblastoma by using cytoplasmic transduction peptide (CTP)-fused protein antigens combined with anti-PD1

Recent clinical trials utilizing antigen-pulsed dendritic cells (DCs) have demonstrated increased survival of vaccinated cancer patients. Besides, the cytoplasmic transduction peptide (CTP) not only has an excellent transcellular efficiency but also shows a strong tendency to remain in the cytoplasm after transduction, without migrating into the nucleus. In this study, we investigated the effectiveness of immunotherapy against malignant gliomas using DCs pulsed with CTP-fused protein antigens combined with programmed cell death protein 1 blockade (anti-PD1). The expression of tumor associated antigen (WT1 and BIRC5) and PDL1 on glioblastoma (GBM) target cells was confirmed by western blot. The effect of CTP-fused protein antigens on mature DCs (VaxDCs) was determined. The immunophenotypes of VaxDCs pulsed with CTP-fused protein antigens was confirmed by flow cytometry and the cytokine production levels of T helper polarization were measured by enzyme-linked immunosorbent (ELISA) assay. The IFN-γ-enzyme linked immunospot and lactate dehydrogenase release assays were performed to estimate the cytotoxic activity of antigen-specific cytotoxic T lymphocytes (CTLs), stimulated by VaxDCs pulsed with CTP-fused protein antigens and anti-PD1, against malignant glioma cells expressing target antigens. VaxDCs pulsed with CTP-fused protein antigens showed enhanced expression of major histocompatibility complex (MHC) and co-stimulatory markers of DCs and resulted in Th1 cytokine polarization. The increase in the number of IFN-γ+ effector T cells paralleled with the enhanced percent specific lysis of GBM targets cells by antigen-specific CTLs. Our study suggested that using CTP-fused protein antigens for DC vaccine preparation along with PD1 blockade could be an effective immunotherapy strategy for GBM.

Vaccination with ubiquitin-hepatitis B core antigen-cytoplasmic transduction peptide enhances the hepatitis B virus-specific cytotoxic T-lymphocyte immune response and inhibits hepatitis B virus replication in transgenic mice

Chronic hepatitis B virus (HBV) infection is characterized by functionally impaired type 1 T-helper cell (Thl) immunity and poor HBV‑specific T‑cell responses. Ubiquitin (Ub), a highly conserved small regulatory protein, commonly serves as a signal for target proteins that are recognized and degraded in proteasomes. The rapid degradation of Ub‑mediated antigens results in efficient stimulation of cell‑mediated immune responses. Thus, the Ub‑HBV core antigen (HBcAg)‑cytoplasmic transduction peptide (CTP) fusion protein was designed for specific delivery of a foreign modified antigen to the cytoplasm of antigen‑presenting cells. HBV transgenic mice were used to determine whether Ub‑HBcAg‑CTP would restore HBV‑specific immune responses and anti‑viral immunity in these animals. The results demonstrated that synthesized Ub‑HBcAg‑CTP not only significantly increased the levels of interleukin‑2 and interferon (IFN)‑γ compared with those in the HBcAg‑CTP, IFN‑α, Ub‑HBcAg, HBcAg and phosphate‑buffered saline groups, but additionally induced the highest IFN‑γ+ CD8+ T‑cell numbers and HBV‑specific cytotoxic T lymphocyte (CTL) responses, indicating a strong immune response. In addition, enhancement of specific CTL activity provoked by the fusion protein reduced hepatitis B surface antigen (HBsAg) and HBV DNA serum levels and diminished the expression of HBsAg and HBcAg in liver tissue of HBV transgenic mice, suggesting that there was a therapeutic effect. In conclusion, the present study provided evidence that Ub‑HBcAg‑CTP activated the Th1‑dependent immunity, triggered functional T cell responses and subsequently inhibited viral replication in HBV transgenic mice. These observations suggested that the fusion protein may represent an innovative and promising candidate for active immunotherapy during chronic and persistent HBV.