The present invention relates to the treatment of cancer and to the prevention of cancer growth and/or metastasis. In particular, the invention relates to cellular and acellular vaccines containing C3d, a proteolytic product of complement (C3), and methods of enhancing a host immune response (e.g., a T cell mediated immune response) against cancers using same. Compositions and methods of the invention find use, alone or in conjunction with other cancer therapies, in treating lymphoma and/or cancers that develop and/or persist by evading host immune surveillance and/or responses (e.g., T-cell mediated immune responses). Compositions and methods of the invention find use in both clinical and research settings, for example, within the fields of biology, immunology, medicine, and oncology.