A decade ago, researchers at Stanford University School of Medicine found an abnormally high concentration of a specific protein called CD47 when analyzing leukemia cells. Normally found on healthy blood cells, these CD47 proteins function as “do not kill” flags for passing immune cells known as macrophages.
What this meant was that the leukemia cells were hiding from our immune system by masking themselves with a common bodily protein — they were pretending to be healthy living cells. At first, this was simply seen as a clever form of molecular camouflage. But CD47 is turning out to have implications on a far grander scale.
Fast forward to the present, and the same Stanford researchers are gearing up for potentially groundbreaking human trials surrounding this discovery. Amazingly, CD47 was found in high concentration not just on leukemia cells but “on every single primary tumor that [was] tested,” according to Stanford biologist Irving Weissman.
The implication of the research is that not just leukemia but also breast, ovary, colon, brain, bladder, liver, and prostate cancers all wear this same form of camouflage. Figure out how to break it, and there's your common cure.
Excitingly, this is exactly what scientists are aiming to accomplish right now, and so far, the results are more than promising.
By developing an anti-CD47 antibody, researchers have already successfully blocked cancer's “do not kill” flag in human tumors transplanted into mice. The results varied by tumor type, but it was always a positive outcome.
In bladder tumors, the anti-CD47 antibody reduced cancer migration to lymph nodes by 90%.
In colon cancer trials, tumors shrank in size by an average of 68%. And in breast cancer, the antibody eliminated cancer entirely.
Of course, as with any drug this early in development, there are two very important questions left to be answered. First is whether or not these results will transfer over to a more complex human system. Targeting a tumor implanted into a rodent's leg is an ideally isolated environment; the human body is not.
Second is the matter of safety and side effects. There is strong warrant for toxicity concern here considering the fact that CD47 is so commonly found in our bodies. While anti-CD47 antigens seem to be more attracted to the high concentrations of the protein on cancer cells, they will still disturb healthy functioning cells containing the protein.
When treating leukemia with the drug, researchers found a temporary decrease in red blood cells, meaning the macrophages were now viewing them as foreign intruders. Fortunately, the mice were able to compensate and replace these cells without any adverse effects.
If toxicity levels are as limited in human trials, anti-CD47 antigens could be the most significant medical discovery since penicillin. At this point, though, we'll have to wait and see.
