Conclusion and prospect
Lipid adjuvants have made remarkable achievements in the treatment of cancer, and their good immunogenicity, safety and controllability have been proved. In this review, we summarized two roles in adjuvants of lipids: delivery carrier and immune stimulants. According to the new understanding of current immune cell biology, we can create new lipids with immunogenicity, or carry out structural modification based on the preexisting lipids to obtain more optimized products, to further reduce the clinical dosage of drugs and improve the compliance of cancer patients.
Furthermore, due to the complexity of the human environment, especially the variability of the tumor environment, it is not only need to consider the internal association between the carriers and antigens, but also the influence of the biological characteristics in vivo[93]. A new platform must be developed to respond to the structure and biological characteristics of the target cells to overcome the complex mechanism of immunosuppression in tumor microenvironments. Based on the key parameters such as surface charge, membrane fluidity, andin vivo transfection rate, new lipid materials or functionalized liposomes will be added to establish a new liposome delivery platform. Using this platform to deliver antigens and immune stimulants and promote the cross presentation of antigens is a development direction of cancer vaccines in the future.
Whereas, the safety and stability of new materials are the keys to the successful establishment of the delivery platform [7]. Liposome cancer vaccine has no long-term safety record and needs to be further verified. The cancer vaccine containing lipid adjuvant is amazing in clinical trials, the existing experimental data were only for individual types of tumors, and there is still a lack of extensive and comprehensive clinical trial data, which indicates that it is still a long way to go from laboratory to clinical application. At the same time, the induction data of this new adjuvant in vivo andin vitro were not consistent, so an efficient and simple method should be established to visualize the immune response, that is, to monitor the changes of the number, function, and immune behavior of immune cells in vivo [94]. Only by solving all the above problems, the application of lipid adjuvants in cancer vaccines can support the future demand.