Detection, Isolation, and Characterization of α-fetoprotein-specific T Cell Populations and Clones Using MHC Class I Multimer Magnetic Sorting

Identification of α-fetoprotein-specific T-cell receptors for hepatocellular carcinoma immunotherapy

Hepatocellular carcinoma (HCC) is the major form of liver cancer for which there is no effective therapy. Genetic modification with T-cell receptors (TCRs) specific for HCC-associated antigens, such as α-fetoprotein (AFP), can potentially redirect human T cells to specifically recognize and kill HCC tumor cells to achieve antitumor effects. In this study, using lentivector and peptide immunization, we identified a population of cluster of differentiation 8 (CD8) T cells in human leukocyte antigen (HLA)-A2 transgenic AAD mice that recognized AFP₁₅₈ epitope on human HCC cells. Adoptive transfer of the AFP₁₅₈ -specific mouse CD8 T cells eradicated HepG2 tumor xenografts as large as 2 cm in diameter in immunocompromised nonobese diabetic severe combined immunodeficient gamma knockout (NSG) mice. We then established T-cell hybridoma clones from the AFP₁₅₈ -specific mouse CD8 T cells and identified three sets of paired TCR genes out of five hybridomas. Expression of the murine TCR genes redirected primary human T cells to bind HLA-A2/AFP₁₅₈ tetramer. TCR gene-engineered human T (TCR-T) cells also specifically recognized HLA-A2⁺ AFP⁺ HepG2 HCC tumor cells and produced effector cytokines. Importantly, the TCR-T cells could specifically kill HLA-A2⁺ AFP⁺ HepG2 tumor cells without significant toxicity to normal primary hepatocytes in vitro. Adoptive transfer of the AFP-specific TCR-T cells could eradicate HepG2 tumors in NSG mice.

CONCLUSION

We have identified AFP-specific murine TCR genes that can redirect human T cells to specifically recognize and kill HCC tumor cells, and those AFP₁₅₈ -specific TCRs have a great potential to engineer a patient's autologous T cells to treat HCC tumors. (Hepatology 2018).

Differential biodistribution of oncolytic poxvirus administered systemically in an autochthonous model of hepatocellular carcinoma

BACKGROUND

Preclinical studies have demonstrated that, unlike oncolytic adenoviruses, oncolytic vaccinia viruses can reach implanted tumors upon systemic injection. However, the biodistribution of this oncolytic agent in in situ autochthonous tumor models remains poorly characterized. In the present study, we assessed this biodistribution in a model of mouse hepatocellular carcinoma (HCC) obtained after injection of the carcinogen diethylnitrosamine (DEN).

METHODS

Twelve months after DEN administration, histology, quantitative reverse transcription-polymerase chain reaction, in situ hybridization and viral titration were used to characterize tumors, as well as to assess the viral load of the livers upon either intravenous or intraperitoineal injection.

RESULTS

The results obtained showed that the architecture of the liver was lost, with a noticeable absence of sinusoids, as well as the presence of steatosis and α-fetoprotein-positive HCC tumor nodules. Bioluminescence imaging and measures of the infective virus load demonstrated that intravenous injection of 10(8)  plaque-forming units of the recombinant vaccinia virus led to a predominant transduction of the liver, whereas intraperitoneal injection resulted in a lower level of liver transduction accompanied by an increased infection of the lungs, spleen, kidneys and bowels. Immunohistochemical analysis of liver sections of animals injected intravenously with the virus revealed a preferential localization of vaccinia-specific immunoreactivity in the tumors.

CONCLUSIONS

The findings of the present study emphasize the importance of the route of administration of the vector and highlight the relevance of systemic injection of oncolytic vaccinia virus in the context of hepatocellular carcinoma.

Immunotherapy of hepatocellular carcinoma: is there a place for regulatory T-lymphocyte depletion?

Immunotherapy represents a potential therapeutic option for patients with hepatocellular carcinoma (HCC), especially as secondary treatment to prevent recurrence. It has been shown that a patient's survival is directly correlated to the type and number of tumor-infiltrating immune cells, indicating that immune responses have a direct effect on the clinical course of the disease. We have assessed the potential of immunotherapy against HCC in preclinical models of low tumor burden. An antigen-specific strategy targeting α-fetoprotein, and consisting of immunization with a DNA-based synthetic vector (DNAmAFP/704), was tested on an autochthonous model of chemical hepatocarcinogenesis and led to an important (65%) reduction of the tumor burden. A nonspecific approach of CD25(+) T-cell depletion by injection of PC61 antibody was also tested on an orthotopic HCC model and led to a significant protection against tumor development. Antigen-specific immunotherapy and Treg depletion are promising strategies in physiologically relevant HCC preclinical models. Future clinical trials will demonstrate if a combination of Treg depletion with an antigen-specific immunotherapy will also translate into clinical responses in HCC patients.

AFP-specific immunotherapy impairs growth of autochthonous hepatocellular carcinoma in mice

BACKGROUND AND AIMS

In this study, we have assessed the potential of antigen-specific immunotherapy against hepatocellular carcinoma (HCC) in conditions of low tumour burden, in an autochthonous HCC model.

METHODS

Diethylnitrosamine (DEN) injected into infant mice results in the development of multi-nodular HCC in which alpha-fetoprotein (AFP) is re-expressed. DEN-injected animals received an antigen-specific immunization with a synthetic vector consisting of a low dose of AFP-encoding plasmid formulated with the amphiphilic block copolymer 704 (DNAmAFP/704). Animals were treated at 4 and 5 months, before macroscopic nodules were detected, and were sacrificed at 8 months. The tumour burden, as well as liver histology, was assessed. AFP and MHC class I molecule expression in the nodules were monitored by qRT-PCR.

RESULTS

The AFP-specific immunotherapy led to a significant (65%) reduction in tumour size. The reduced expression of AFP and MHC class I molecules was measured in the remaining nodules taken from the DNAmAFP/704-treated group.

CONCLUSIONS

This is the first study demonstrating the relevance of antigen-specific immunotherapy in an autochthonous HCC model. In this context, we validated the use of an anti-tumour immunotherapy based on vaccination with nanoparticles consisting of low dose antigen-encoding DNA formulated with a block copolymer. Our results demonstrate the potential of this strategy as adjuvant immunotherapy to reduce the recurrence risk after local treatment of HCC patients.