Nonviral oncogenic antigens and the inflammatory signals driving early cancer development as targets for cancer immunoprevention

Cancer immunoprevention is an emerging field that holds much promise. Within the past 20 years, prophylactic vaccines have been implemented on the population level for the immunoprevention of carcinomas induced by viruses, specifically hepatitis B virus (HBV) and human papillomavirus (HPV) infection. Armed with the success of prophylactic vaccines that prevent viral-induced tumors, the field must overcome its next hurdle: to develop robust prophylactic vaccines that prevent the remaining >80% of human cancers not induced by viral infection. In this review, we discuss some of the most promising non-virus-associated prophylactic vaccines that target endogenous neoantigens, including the earliest oncogene products, altered mucin 1 (MUC1) and a-enolase (ENO1), all of which produce new targets in the earliest stages of nonviral-induced tumorigenesis. We also highlight a novel attenuated Listeria monocytogenes-based vaccine expressing mutant oncogene Kras^G12D ( LM-Kras) effective in a pancreatic cancer model. A novel chimeric human/rat HER-2 plasmid vaccine (HuRT-DNA vaccine) effective in a breast cancer model is also discussed. In addition to prophylactic vaccine developments, this review highlights the potential use of classic drugs, such as aspirin and metformin, as chemopreventive agents that can potentially be used as adjuvants to enhance the anticancer immunogenicity and efficacy of noninfectious prophylactic vaccines by modulating the inflammatory pathways within the early tumor microenvironment (TME) that propels tumorigenesis. Finally, timing of prophylactic vaccine administration is critical to its immunopreventive efficacy, providing a necessary role of current and emerging biomarkers for cancer screening and early cancer detection.