More on CD47 as a Potentially Broad Cancer Therapy Target
All commonalities in cancer are interesting, as part of the high cost of dealing with cancer is based on the many, many different varieties and the great variability of its biochemistry even between individual tumors. Anything that is common between many types of cancer and between tumors offers a possibility of a lower-cost and broader therapy. The cell surface marker CD47 has shown up of late as a possible commonality, and work continues to see whether a therapy can be built on this:
A decade ago, [researchers] discovered that leukemia cells produce higher levels of a protein called CD47 than do healthy cells. CD47 [is] also displayed on healthy blood cells; it's a marker that blocks the immune system from destroying them as they circulate. Cancers take advantage of this flag to trick the immune system into ignoring them. In the past few years, [researchers] showed that blocking CD47 with an antibody cured some cases of lymphomas and leukemias in mice by stimulating the immune system to recognize the cancer cells as invaders. Now, [researchers] have shown that the CD47-blocking antibody may have a far wider impact than just blood cancers."What we've shown is that CD47 isn't just important on leukemias and lymphomas. It's on every single human primary tumor that we tested." Moreover, [the scientists] found that cancer cells always had higher levels of CD47 than did healthy cells. How much CD47 a tumor made could predict the survival odds of a patient. To determine whether [targeting] CD47 was beneficial, the scientists exposed tumor cells to macrophages, a type of immune cell, and anti-CD47 molecules in petri dishes. Without the drug, the macrophages ignored the cancerous cells. But when the CD47 was [targeted], the macrophages engulfed and destroyed cancer cells from all tumor types.
Next, the team transplanted human tumors into the feet of mice, where tumors can be easily monitored. When they treated the rodents with anti-CD47, the tumors shrank and did not spread to the rest of the body. In mice given human bladder cancer tumors, for example, 10 of 10 untreated mice had cancer that spread to their lymph nodes. Only one of 10 mice treated with anti-CD47 had a lymph node with signs of cancer. Moreover, the implanted tumor often got smaller after treatment - colon cancers transplanted into the mice shrank to less than one-third of their original size, on average.
Link: http://news.sciencemag.org/sciencenow/2012/03/one-drug-to-shrink-all-tumors.html