Cloning techniques to identify genes and peptides of tumor-associated antigens have created new possibilities
for the immunotherapy of patients with advanced cancer. Here, we review recent clinical trials of specific cancer vaccines,
mainly HLA-restricted peptides, and epitope-encoding vectors for advanced colorectal cancer (CRC). Many researchers
initially focused on carcinoembryonic antigen (CEA) as an immunologic target antigen that is overexpressed on virtually
all CRCs. A recombinant vaccine containing the CEA gene and dendritic cells (DCs) loaded with CEA peptide was administered
to patients with CEA-elevated CRC. Although CEA-specific responses were detected, the clinical responses
were limited. Recently, new types of clinical trials—namely, a personalized protocol to take into account the immunological
diversity of cytotoxic T cell responses among patients and a novel cancer-testis antigen protocol that uses multiple
peptides derived from genes identified by the cDNA array method—have been introduced. The personalized protocol
seemed to be better than the classical (non-personalized) protocol in terms of clinical response and survival. Novel cancertestis
antigen protocols that use multiple CRC-derived peptides were recently conducted in patients with advanced CRC.
The preliminary study yielded promising results regarding specific T cell responses to peptides and survival benefits. In
this review, we summarize these results and discuss future perspectives.
Keywords: Active specific cancer vaccine, cancer-specific peptide vaccine, colorectal cancer (CRC), personalized peptide vaccine, tumor-associated antigens, immunotherapy, "cancer vaccines", colorectal cancer, carcinoembryonic antigen (CEA), immunologic target antigen, clinical trials, cytotoxic, cancer-testis, "multiple
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