A cancer vaccine composed of an immunogenic peptide derived from the Ras homolog family member C (RhoC; Rho-related GTP-binding protein RhoC) that is emulsified in the immunoadjuvant montanide ISA-51, with potential immunomodulating and antineoplastic activities. Upon subcutaneous administration, onilcamotide may stimulate the host immune system to mount a humoral and cytotoxic T-lymphocyte (CTL) response against tumor cells expressing RhoC, which results in tumor cell lysis. RhoC, a tumor-associated antigen (TAA) that is overexpressed in a variety of tumor cell types, is associated with increased metastatic potential.