A donor-derived, off-the-shelf, microbiome therapeutic cancer peptide vaccine composed of three bacterial onco-mimics, immunogenic microbiome-derived peptides that are highly homologous to tumor-associated antigens (TAAs), that are obtained and selected from the human gut microbiome and are specific for brain tumors, including glioblastoma, with potential immunomodulating and antineoplastic activities. The three microbiome-derived bacterial antigens in EO2401 mimic three TAAs that are highly expressed by brain tumors. Upon administration of microbiome-derived peptide vaccine EO2401, the peptides are taken up by and presented on dendritic cells (DCs) to T-cells. As the presented antigens display molecular mimicry with selected TAAs on brain cancer cells, a memory T-cell and cytotoxic T-lymphocyte (CTL)-mediated immune response may be mounted against the TAAs expressed on the brain cancer cells, thereby eradicating the brain cancer cells.