Review. Colon cancer vaccines: an update

Despite advances in research and treatment modalities, colorectal cancer still accounts for around half a million deaths yearly worldwide. Traditional and even newer pharmaceutical therapeutic regimens are limited in terms of tolerance, efficacy and cross-resistance. Additional non-cross resistant therapies with non-overlapping toxicities are needed to improve the outcome for patients with colorectal cancer. Cancer vaccines, designed to activate immune effectors (T-cells and antibodies) to prevent recurrence or treat advanced cancers, have now demonstrated clinical benefit in prostate cancer and lymphoma. Because immune effector infiltration into colon tumours is associated with improved clinical outcome, vaccines intended to activate immune responses against colon cancer have generated significant interest. This review discusses data supportive of the immune responsiveness of colorectal cancer, as well as the current status of colon cancer vaccines under development including those based on whole tumour cells or lysates, peptide or protein antigens, anti-idiotype antibodies, viral vectors, and dendritic cells. We also discuss challenges to colon cancer vaccine development, such as tumour associated mechanisms for immune evasion, and how future strategies may address these challenges.