After more than a decade of research, Stanford University biologist Irving Weissman believes his tumor-killing drug is ready for human trials.

Speaking to reporter Sarah C. P. Williams for Science Magazine, a publication of the American Association for the Advancement of Science, Weissman said numerous tests have showed that his experimental drug either killed or shrank the cancerous growths implanted into mice.

The drug was tested on a variety of different cancers, including bladder, brain, liver, breast, colon, ovary and prostate growths. In all cases, it succeeded in dramatic reduction or total eradication of the cancer.

It works by tricking cancer cells into shutting down production of a specific protein that camouflages the disease from the host's immune system. The CD47 protein, Weissman said, was discovered in blood cancers, but research has found that it also exists in virtually every other type of human cancer as well.

That's the weak spot, he believes.

While it seems to give hope for a breakthrough in its present state, Weissman's research will have to face a new set of challenges in humans, where cancer has grown organically instead of via implant.

That represents a very different environment where tumors may have additional defenses against immune system attack and unforeseen side effects could emerge, sources told Science Magazine.

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