A recent study published by Yuan et al. from MD Anderson Cancer Center showed that natural
Vitamin E (DL-a-tocopherol) enhanced the response rates of cancer immunotherapy by reinvigorating dendritic cells. I am going to break down the overall key highlights of the study.
One is that they reviewed the electronic health records of cancer patients on immunotherapy and determined that one’s taking Vitamin E had improved survival. This led them to try to determine the mechanism in the mouse model.
They discovered that Vitamin E entered the dendritic cells inhibiting a checkpoint within them called SHP1. This resulted in enhanced antigen presentation; as you may know, dendritic cells are involved in presenting foreign or tumor antigens to other immune cells, such as T cells, to activate an immune response. There has been much work on dendritic cell vaccines, which has been disappointing. This is because that is only one part of the activation of the immune response. In addition, like most immune cells, dendritic cells can also be regulatory to inhibit an immune response against cancer. However, in this situation described in the study, Vitamin E leads to an activation of mature dendritic cells presenting tumor antigen, and the overall response is enhanced due to the presence of traditional immunotherapy such as PD-1 CTLA-4 inhibitors. In previous studies, the benefits of Vitamin E were not clear.
Another study to keep in mind was published by Kang et al. in 2014, showing that Vitamin E reduced myeloid-derived suppressor cells (MDSC) and increased the effects of CD8+ T cells against tumors; as you may know from my book that MDSCs are immune cells that inhibit the anti-cancer immune response, essentially protecting cancer. High amounts of MDSC are associated with a poor prognosis and reduce potential response to immunotherapy. In the study by Kang, they showed that Vitamin E reduced the MDSCs, resulting in increased anti- cancer CD8+ T cells infiltrating the tumor. This study gives a different mechanism but adds more data backing the use of Vitamin E in conjunction with immunotherapy.
Indeed, supplementation with Vitamin E should be considered for patients on immunotherapy for cancer. However, not much has been discussed on dosing. The 2014 study showed benefits with dietary Vitamin E, but they also described a much more significant effect when injected into the tumor. They explain that injected Vitamin E can modify the tumor microenvironment to be more receptive to other immunotherapy treatments. As you can see, the theme of injection into the tumor site continues to be the most potent treatment option. Otherwise, a standard dose of 400 IU of natural Vitamin E orally a day is probably helpful.