Dear Yaying Pan

Cancer vaccines hold great promise for treating cancer and preventing recurrence, potentially becoming a crucial part of future cancer immunotherapies. But there are major challenges making it difficult to develop effective cancer vaccines.

A. Cancer cells often express antigens that are not specific to the tumor and can also be found on normal cells, leading to unwanted side effects. So, one must search for unique tumor-specific antigens, and tumor-associated antigens, to target only the cancer cells.

B. The tumor microenvironment (TME) can evolve, making it difficult for the immune system to effectively target cancer cells. So, one has to find ways to neutralize immunosuppressive molecules within the TME and enhance the activation of immune cells to target the tumor.

C. The immune system can sometimes mount a weak or poorly targeted response against cancer. So, one must optimize vaccine formulations, adjuvants that are used to enhance immune responses, and the delivery methods to stimulate strong and, more important, the specific T-cell responses against the tumor.

D. Tumor heterogeneity is another major hurdle making it difficult to target all tumor cells with a single vaccine.

E. You will observe that not all cancer patients respond well to cancer vaccines. Moreover, personalized vaccines, which are tailored to individual tumor profiles, can be challenging to produce on a large scale.

Some personalized vaccines, like those based on mRNA technology, are being developed and may become available to certain patient populations in the coming years. Additionally, preventive vaccines targeting viral infections that can cause cancer are already available and are effective, for instance the HPV vaccine and HBV vaccine. Research is also ongoing to develop preventive vaccines for other cancer types, such as ovarian cancer.

It would be good to have a single, universal cancer vaccine, but it is unlikely. Therefore, we should focus on personalized and preventive cancer vaccines which offer significant promise for future cancer prevention and treatment.

Regards,

Malcolm Nobre