Therapeutic vaccines against tumors associated with human papillomaviruses (HPV) should elicit cellular immune responses against early HPV antigens, primarily the oncoproteins E7 and E6. Because of safety concerns, the direct use of an unmodified oncogene is impossible in human DNA vaccination. Therefore, we introduced three point mutations into the pRb-binding site of HPV16 E7 oncogene to eliminate its transformation potential. The resultant gene was denoted E7GGG. The rates of expression and the cellular localization of E7 and E7GGG proteins were comparable. In immunization-challenge experiments, the efficacy of plasmids containing the E7, E7GGG, or fusion genes of HPV16 E7, viz. L1DeltaCE7(1-60) (M. Muller et al., 1997, Virology 234, 93-111), and Sig/E7/LAMP-1 (T. C. Wu et al., 1995, Proc. Natl. Acad. Sci. USA 92, 11671-11675), was compared. While tumors developed in all animals immunized with the wild-type E7 gene, a significant proportion of mice remained tumor-free after vaccination with the E7GGG gene. The fusion gene L1DeltaCE7(1-60) induced negligible protection, but Sig/E7/LAMP-1 conferred the highest protection. Intradermal immunization by gene gun proved superior to i.m. inoculation. In "therapeutic" experiments, a 1-day delay between inoculation of oncogenic cells and the start of DNA immunization resulted in partial therapeutic effect, but a 3-day delay produced a substantially lower immunization effect. A combination of Sig/E7/LAMP-1 and E7GGG genes did not enhance the immune response. These results demonstrate a significant enhancement of HPV16 E7 immunogenicity after mutagenesis of the pRb-binding site, but the mutated E7 gene did not excel the Sig/E7/LAMP-1 fusion gene.

No abstract

The therapy of different advanced-stage malignancies with monoclonal antibodies blocking programmed cell death protein 1 (PD-1)/PD-1 ligand 1 (PD-L1) signaling has had an impressive long-lasting effect in a portion of patients, but in most cases, this therapy was not successful, or a secondary resistance developed. To enhance its efficacy in treated patients, predictive biomarkers are searched for and various combination treatments are intensively investigated. As the downregulation of major histocompatibility complex (MHC) class I molecules is one of the most frequent mechanisms of tumor escape from the host’s immunity, it should be considered in PD-1/PD-L1 checkpoint inhibition. The potential for the use of a PD-1/PD-L1 blockade in the treatment of tumors with aberrant MHC class I expression is discussed, and some strategies of combination therapy are suggested.

As metastasis is a major cause of death in cancer patients, new anti-metastatic strategies are needed to improve cancer therapy outcomes. Numerous pathways have been shown to contribute to migration and invasion of malignant tumors. Aspartate β-hydroxylase (ASPH) is a key player in the malignant transformation of solid tumors by enhancing cell proliferation, migration, and invasion. ASPH also promotes tumor growth by stimulation of angiogenesis and immunosuppression. These effects are mainly achieved via the activation of Notch and SRC signaling pathways. ASPH expression is upregulated by growth factors and hypoxia in different human tumors and its inactivation may have broad clinical impact. Therefore, small molecule inhibitors of ASPH enzymatic activity have been developed and their anti-metastatic effect confirmed in preclinical mouse models. ASPH can also be targeted by monoclonal antibodies and has also been used as a tumor-associated antigen to induce both cluster of differentiation (CD) 8 + and CD4 + T cells in mice. The PAN-301-1 vaccine against ASPH has already been tested in a phase 1 clinical trial in patients with prostate cancer. In summary, ASPH is a promising target for anti-tumor and anti-metastatic therapy based on inactivation of catalytic activity and/or immunotherapy.

Transient expression of foreign genes based on plant viral vectors is a suitable system for the production of relevant immunogens that can be used for the development of a new generation of vaccines against a variety of infectious diseases. In the present study the epitope derived from HPV-16 L2 minor capsid protein (amino acids 108-120) was expressed from Potato virus X (PVX)-based vector pGR106 as N- or C-terminal fusion with the PVX coat protein (PVX CP) in transgenic Nicotiana benthamiana plants. The fusion protein L2 108-120-PVX CP was successfully expressed in plants at a level of 170 mg/kg of fresh leaf tissue. The C-terminal fusion protein PVX CP- L2 108-120 was expressed using mutated vector sequence to avoid homologous recombination at a level of 8 mg/kg of fresh leaf tissue. Immunogenicity of L2 108-120-PVX CP virus-like particles was tested after immunization of mice by subcutaneous injection or tattoo administration. In animal sera the antibodies against the PVX CP and the L2 108-120 epitope were found after both methods of vaccine delivery.