In silico Evaluation of PLAC1-fliC As a Chimeric Vaccine against Breast Cancer

Background: Breast cancer is one of the most prevalent cancers among women. Common cancer treatment methods are not effective enough, and there is a need for a more efficient treatment procedure. Cancer vaccine is a novel immunotherapy method that stimulates humoral and/or cellular immunity against cancer. Placenta-specific protein 1 (PLAC1) is a cancer/testis antigen, prevalent in breast cancer and rarely found in normal tissues. FliC as a bacterial adjuvant when fused to PLAC1 can elicit humoral and cellular responses. Therefore, PLAC1-fliC is a chimeric protein, which can be considered a suitable candidate against breast cancer. Methods: ProtParam was used to evaluate physicochemical properties of PLAC1-fliC. Second structures were determined using the GOR V server. PLAC1-fliC three-dimensional structure was modeled by Phyre2, and it was refined using GalaxyWEB. The refined model was submitted to RAMPAGE, PROCHECK, and ProSA-web for validation. Antigenicity and allergenicity of the construct were predicted by ANTIGENpro, VaxiJen, AllergenFP, and SDAP databases. Then MHC‑I- and MHC‑II-binding epitopes of PLAC1-fliC were forecasted by NetMHC 4.0 and NetMHCII 2.3 Servers. Finally, Ellipro and CTLpred were employed to predict B cell and cytotoxic T lymphocytes epitopes. Results: The construct was evaluated as a stable fusion protein, which could be antigenic and could stimulate B and T cells against breast cancer. Conclusion: PLAC1-fliC, as a cancer vaccine candidate, might be suitable and specific for breast cancer, which could evoke humoral and cellular immunity against this type of tumor.