Title : Targeting tumor-associated antigens through variable epitope libraries: Antitumor activity in breast cancer and acute myeloid leukemia
Abstract:
Background: Tumor-associated antigens (TAAs) represent attractive targets for cancer immunotherapy; however, tumor heterogeneity and immune escape remain major challenges for antigen-specific vaccination. Variable Epitope Libraries (VELs) are highly diverse collections of mutated antigenic sequences designed to expand the repertoire of epitopes available for immune recognition. Here, we evaluated the therapeutic antitumor activity of mono- and multi-antigenic VELs derived from different TAAs in murine models of triple-negative breast cancer (TNBC) and acute myeloid leukemia (AML).
Methods: Four synthetic peptide-based VELs were evaluated: three mono-antigenic libraries derived from mesothelin (MESL), MUC-1 (ML), and p53 (PL), administered individually or as an equimolar mixture, and a multi-antigenic library incorporating epitopes from multiple TAAs, including mesothelin, MUC-1, and p53 (SPVP). Therapeutic efficacy was assessed in syngeneic BALB/c mouse models of TNBC (4T1) and AML (WEHI-3) (n=6/group). For the 4T1 model, 10,000 viable tumor cells were orthotopically implanted into the mammary fat pad, whereas AML was established by intravenous administration of 300,000 viable WEHI-3 cells. Five days after tumor implantation, mice received a single intrasplenic immunization with 100 μg of the corresponding VEL. In the 4T1 model, tumor growth was monitored by serial caliper measurements, and tumor volume was estimated as V=(L×W²)/2. Pulmonary macrometastases were quantified after Bouin's solution perfusion. In the WEHI-3 model, therapeutic efficacy was evaluated by survival.
Results: Therapeutic vaccination with VELs showed significant antitumor activity in both experimental models. In the 4T1 model, VEL-vaccinated groups exhibited significantly reduced primary tumor development and fewer pulmonary macrometastases compared with untreated controls. In the WEHI-3 model, VEL vaccination significantly prolonged survival. Antitumor activity was observed following vaccination with mono-antigenic VELs, their equimolar combination, and the multi-antigenic SPVP construct.
Conclusion: These findings demonstrate that therapeutic vaccination with TAA-derived VELs can exert significant antitumor effects in both solid and hematological murine tumor models. The activity observed with mono-antigenic, combined, and multi-antigenic VEL formulations supports further investigation of antigenically diversified epitope libraries as a potential platform for cancer immunotherapy.
