There has been a flurry of news reports regarding a study recently published in the Proceedings of the National Academy of Sciences that claims scientists may have developed a vaccine that when used in conjunction with other cancer therapies increases the chances of melanoma survival rates.
The researchers developed a so-called cancer vaccine and then decided to look at whether using a combination approach (vaccine + other therapies) would pay dividends. They opted to investigate a molecule called Diprovicim because it is already known that this molecule targets an immune receptor found in mice and humans – TLR1/TLR2.
Mice with an aggressive form of melanoma were first treated with anti-PD-L1 (an immune checkpoint inhibitor that allows the body’s T cells to find and destroy cancer cells). Then they divided the mice into one of three groups: one got the cancer vaccine; one group got the vaccine plus a molecule of Diprovicim; and the rest got the vaccine plus a different molecule. All of the mice got regular intramuscular shots, meaning the injection was not administered at the site of the tumor. This is similar to how many humans receive current vaccinations.
Then the experimenters observed how the mice fared over the course of 54 days. The mice that only got the cancer vaccine did not fare well at all, 0% survived over the observation period. The mice with the cancer vaccine with the different molecule had a survival rate of 25%, only 1 out 4 – likely as a result of the immune checkpoint inhibitor therapy they received. However, the mice that were given the vaccine plus Diprovicim had a survival rate of 100%!
The other incredibly interesting result was that in the mice treated with the vaccine plus Diprovicim, the researchers were unable to re-establish tumors in them. Meaning, just like a regular vaccine, the immune system was trained to recognize and destroy the cancer cells before any melanoma could recur.
The author of the study, Dale Boger, PhD, stated, “It was exciting to see the vaccine working simultaneously with a cancer immunotherapy like anti-PD-L1.”
I have to imagine that there are research teams out there right now ready to see if the vaccine this particular group of researchers developed was the agent that allowed Diprovicim to work so well in these mice. Or if it was a case of the checkpoint inhibitor immunotherapy plus the Diprovicim that did the trick. The researchers noted that using Diprovicim stimulated the immune system, causing it to produce cells called tumor-infiltrating leukocytes.
I’m not convinced the vaccine itself was beneficial in any way (believe me, I am fully onboard with vaccinations when they work but this one makes me wonder – wouldn’t the mice with the vaccine-only have something better than 0% survival if it actually had any therapeutic benefit?). However, I would love to see more research to conclusively demonstrate whether we might be able to formulate a vaccine against melanoma. Or if we can harness the ability of Diprovicim plus immunotherapy to develop a way to stop melanoma before it spreads.