Melanoma immunotherapy using mature DCs expressing the constitutive proteasome

Abstract

Background. Many cancers, including melanoma, exclusively express constitutive proteasomes (cPs) and are unable to express immunoproteasomes (iPs). In contrast, mature DCs used for immunotherapy exclusively express iPs. Since proteasomes generate peptides presented by HLA class I molecules, we hypothesized that mature melanoma antigen-loaded DCs engineered to process antigens through cPs would be superior inducers of antimelanoma immunity in vivo.Methods. Subjects with metastatic melanoma were vaccinated with mature DCs transfected with RNAs encoding melanoma antigens MART1, MAGE-3, gp100, and tyrosinase. These DCs were derived from monocytes that were untransfected (Arm A; n = 4), transfected with control siRNA (Arm B; n = 3), or transfected with siRNAs targeting the 3 inducible iP subunits (Arm C; n = 5).Results. Vaccination stimulated antigen-specific T cell responses in all subjects, which peaked after 3-4 vaccinations, but remained elevated in Arm C subjects. Also in Arm C, circulating melanoma cell levels (as detected by quantitative PCR) fell, and T cell lytic activity against autologous melanoma was induced. In HLA-A2 + subjects, CD8 + T cells that bound tetramers loaded with cP-derived melanoma antigenic peptides were found in the peripheral blood only in Arm C subjects. Of 2 subjects with active disease (both in Arm C), one had a partial clinical response, while the other, who exhibited diffuse dermal and soft tissue metastases, had a complete response. Conclusion.These results suggest that the efficacy of melanoma DC-based immunotherapy is enhanced when tumor antigen-loaded DCs used for vaccination express cPs.Trial registration. Clinicaltrials.gov NCT00672542.Funding.

The proteasome immunosubunits, PA28 and ER‐aminopeptidase 1 protect melanoma cells from efficient MART‐126‐35‐specific T‐cell recognition

“…β2i/MECL-1 and PA28 act via the reduction of N-and C-terminal cleavages, whereas ERAP1 destroys MART-1 peptides. Thus, the sum of different IFN-γ-inducible activities is responsible for reduced MART-1 [26][27][28][29][30][31][32][33][34][35] epitope generation and interferes with the recognition of melanoma cells by specific cytotoxic T lymphocytes as well as the DC-dependent activation of MART-1 [26][27][28][29][30][31][32][33][34][35] epitope-specific T cells after antigen transfer [43]. Overall, our findings suggest that detailed analysis of epitope processing should precede the design of tumor antigen-specific immunotherapy.…”

Pathways and therapeutic targets in melanoma

“…Patients vaccinated with cPs-expressing DCs had lower levels of circulating melanoma cells and enhanced melanoma-directed T-cell-lytic activity, which was of a longer duration compared to patients in control arms of the study. Of the five patients vaccinated with cPs-expressing DCs, one had a complete response, and one had a partial response [273]. …”

Intranasal mRNA nanoparticle vaccination induces prophylactic and therapeutic anti-tumor immunity

“…Promising results emerging from recent clinical trials [7][8][9] supports the notion that this is a strategy that can be translated to humans and is amenable to commercialization. However, this process involves harvesting cells from patients via leukapheresis, generating DCs in vitro from adherent monocytes, loading them with mRNA, maturing them in vitro and re-injecting these mRNA-loaded DCs back into the patient.…”