Figure 3. Precise oncoantigen classification (A). Validated class I, II and III oncoantigens present in various tumor compartments currently targeted by our therapeutic vaccines (B). Comp,53 (black ♌) and Angiomotin 1,54 (red Y) are validated class I oncoantigens expressed on tumor extracellular matrix and on tumor vasculature respectively (left panel). ErbB-2,55 (blue Y), Epsin, (brown E), Claudin,53 (green C) and CSPG4,56 (purple f ) are class II oncoantigens expressed on tumor cell membrane (middle panel). The protein product of the NPM-ALK translocation,57 (ALK, purple ♒) and BIRC5,53 (orange b) are class III oncoantigens present in the cytoplasm and nucleus of carcinomas and lymphomas (right panel). Several additional molecule endowed with the properties of oncoantigens have been validated in immunization assay by other laboratories.58 On the Search for Fresh Oncoantigens The “rite of passage” that marks a tumor antigen to become a verified oncoantigen has two phases: (A) The disclosure of a functional role of the molecule in fostering the transformed phenotype of a given (human) neoplasm, i.e. the “onco” portion of the oncoantigen definition; (B) The evidence that the immune system recognizes the molecule and mounts an effective response affecting tumor progression, i.e. the “antigen” part. The identification of oncoantigens moves from the consideration that the progression of carcinogenesis requires the activation of specific genes and may be altered when these are inhibited. The characterization of genes differentially activated during cancer progression should lead to the identification of prominent targets against which to trigger the immune response. Microarray trans- cription analysis highlights several gene signatures that differentiate successive stages of tumor progression in transgenic mice. Of the transcripts upregulated going from pre-neoplasia to overt cancer, only those that have an ortholog in humans, low expression in normal human tissues, and a high and homogeneous expression in human cancers are selected as “putative” oncoantigens.53 The most promising are those that may be targeted by both antibodies and T cells. They are then validated by immunizing cancer-prone transgenic mice with DNA vaccines targeting them.53,55 For a provisional inventory of putative and verified oncoantigens see reference 52. In many cases vaccines targeting oncoantigens afford cancer- prone genetically engineered mice a life-long protection. By contrast, in the management of minimal residual disease or in the presence of recurrences and metastases, their potential is limited.52,58,60 Greater efficacy could be achieved by targeting oncoantigens expressed by cancer initiating cells (CIC) respons- ible for the progression, metastasis, resistance to therapy, and recurrence of many kinds of tumors. To identify oncoantigens expressed by CIC of mammary cancer we are performing a comparative transcriptomic analysis of the bulk of tumor cells from transgenic mice with that of CIC-enriched serial sphere passages of the same tumor cells.61 Subsequent integration of these mouse data with those from human breast cancer will allow the selection of oncoantigens involved in the maintenance of the CIC-like features of mouse and human cancer. Fresh DNA www.landesbioscience.com OncoImmunology 321