A pentavalent vaccine comprised of the epitope antigens of the ganglioside lactones GD2L and GD3L, Globo H hexasaccharide 1 (Globo H), fucosyl GM1 and N-propionylated polysialic acid conjugated with the immunostimulant keyhole limpet hemocyanin (KLH), with potential immunostimulating and antineoplastic activity. Vaccination with the pentavalent KLH conjugate vaccine may induce production of IgG and IgM antibodies as well as an antibody-dependent cell-mediated cytotoxicity (ADCC) against tumors expressing any of these antigens. The antigens included in the pentavalent KLH conjugate vaccine are upregulated in a variety of cancer cells. KLH, a natural protein isolated from the marine mollusk keyhole limpet, is an immunostimulant carrier protein.