08/26/2008

Good prospects for drug/radiation combo

It was a mistery: Why didn't drugs which boost the tumor-killing power of immune cells in lab do well in clincal trials? Now researchers from Rockefeller University describe a way to enhance the ability of these drugs by combining them with radiation therapy.

Drug/radiation combo may help shrink established tumours.

The immune system’s tumor-fighting T cells work best when maximally activated. Scientists have achieved this by blocking molecules that dampen the cells’ activation, or by removing a population of regulatory T cells that block killing ability of tumor-specific T cells. But neither approach has worked well in patients with established tumors.

Combining these two approaches, a new study published online on August 25^th in the Journal of Experimental Medicine, caused small tumors to shrink but had no effect on large tumors. This finding suggested that some quality of large tumors makes them resistant to T cell killing.

Indeed, blood vessels around large tumors lacked proteins required for killer T cells to crawl out of the circulation and into the tumor. Combining the T cell-boosting treatment with radiation therapy – which has been shown to increase the expression of these vessel proteins – was effective in shrinking also large tumors. It remains to be seen whether combining radiation therapy with T cell-boosting drugs will be effective in humans.