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Dendritic cells (DCs) are being explored as a therapeutic vaccine for cancers. However, their immunogenic potential is limited by the presence of immunosuppressive factors. Among these factors is the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO). In this study, we have investigated the safety, immunogenicity and clinical response of IDO-silenced DC vaccine in four patients with gynecological cancers. DCs were transfected with IDO small interfering RNA and mRNA encoding human telomerase reverse transcriptase (hTERT) or survivin, two universal tumour antigens. Silencing of IDO in DCs did not affect the expression of the co-stimulatory molecules CD80 and CD86, but enhanced the expression of the CCR7 and CD40 molecules. IDO-silenced DCs showed superior potency to activate allogeneic T cells compared to their IDO-positive counterparts. The immunisation with this novel DC cancer vaccine was well tolerated and all patients developed delayed-type hypersensitivity skin reaction and specific T-cell response against hTERT and survivin tumour antigens. Perhaps most importantly, the immune response seen in the patients was related to objective clinical response. Thus, IDO silencing can enhance the immunogenic function of DCs in vitro and in vivo. Overall, the data provide proof-of-principle that immunisation with IDO-silenced DC vaccine is safe and effective in inducing antitumour immunity.

The availability of several complete genome sequences and large numbers of expressed sequences, has led to the development of bioinformatic strategies for large-scale predictions of natural antisense transcripts. In the past two years, this has given at least 1,600 human pairs and 2,500 murine pairs of natural antisense transcripts. However, due to limitations in bioinformatic search tools, experimental validation of the predicted antisense transcripts is crucial. This has been performed only for a small fraction of the large number of predicted natural antisense transcripts. Additionally, bioinformatic approaches will not allow systematic identification of natural antisense transcripts in specific cell or tissue types. More recently, an experimental approach for identification of sense-antisense transcript pairs has been developed. The principle of the strategy is based upon the selection of double-stranded cDNAs as a result of hybridization between first-strand cDNAs that should be generated in the presence of actinomycin D. This experimental strategy allows systematic analysis of sense and antisense partners in any cell or tissue type.

The identification of immunogenic antigens for serological testing and vaccine development is a major challenge facing cancer immunology research. To study the humoral immune response in patients with breast cancer, a T7 phage display cDNA library from an invasive ductal breast carcinoma was panned on patient serum IgG antibodies. By monitoring the selection with an immunoscreening technique, positive phage-displayed cDNA products reacting with breast cancer patient IgG antibodies were selected. Sequence analysis identified immunogenic antigens such as the cytochrome oxidase I, sp100 and Ran GTPase activating protein. Additionally, immunogenic uncharacterized gene products were also identified. Both the known and unknown immunoselected gene products should offer an additional source for cancer gene discovery for diagnostic testing and vaccine development.

Peptide and cDNA phage display libraries can be used to determine the specificities of antibodies present in the whole sera of patients where information about the parental antigens is unknown. In this respect, patient serum antibody binding ligands have been identified. Such ligands would facilitate the design of diagnostic assays and therapeutic vaccines. In the case of cancer, this novel technology is expected to improve our understanding of the immune responses against tumour cells and to discriminate between autoantigen and true tumour specific antigens. Here, we review work on how peptide and cDNA phage display libraries can be used to address the specificity of the immune responses in patients with autoimmune diseases and cancer.

Inhibition of gene expression is an important experimental method to determine the function of genes, and could have a great impact upon the treatment of diseases in which gene products are involved. Catalytic RNAs (ribozymes) with endoribonuclease activity are RNA molecules that site-specifically cleave other RNAs, and thus have tremendous potential as novel therapeutic agents. The capacity of these agents to suppress gene expression in a wide range of systems strengthens the importance of this novel gene-based therapy, and indicate that preformed ribozymes may be useful as pharmaceuticals.