(Ivanhoe Newswire) -- A one-two punch may be the best way to shrink
tumors.
A new study may help explain why anti-cancer drugs, which boost the
tumor-killing power of immune cells, haven’t done well in clinical trials. The
report shows a way to enhance how these drugs shrink well-established tumors.
The immune system’s tumor-fighting T cells work best when they are activated to
their maximum. This happens by blocking molecules that dampen the cells’
activation, or by removing some regulatory T cells that stop the killing ability
of tumor-specific T cells. However, these approaches haven’t worked well in
patients with established tumors.
The new research shows combining these two techniques in mice shrank small
tumors but had no effect on large ones. This suggests the quality of some large
tumors makes them resistant to T cell killing. Data shows the blood vessels
around large tumors don’t have the proteins required for killer T cells to get
out of the circulation and into the tumor.
Researchers say combining the T cell-boosting treatment with radiation therapy
-- which can increase the expression of these vessel proteins -- shrank large
tumors. However, it is still not known whether this combination will work in
humans.
SOURCE: Journal of Experimental Medicine, published online August 25, 2008
