1.   Drug companies have long sought to develop drugs that take advantage of tumor suppressor genes because such drugs might work in a wide variety of cancers.

2.   In their collaboration, the companies will aim for drugs that target cells with defective tumor suppressor genes, which prevent tumors from developing.

3.   Rather, they will look to kill cells that are missing a tumor suppressor gene, indicating that they are or may become cancerous.

4.   Scientists call them tumor suppressor genes because the genes prevent cells from becoming malignant.

5.   The company will take animals that already lack a functioning tumor suppressor gene and delete other genes.

6.   The mutation, he said, involves a deletion of genetic material that destroys the functioning of a tumor suppressor gene.

7.   The method depends on first infecting the cells with a tumor gene that makes them divide.

8.   The new tumor suppressor gene, by contrast, seems to take phosphates off proteins and slow cell growth.

9.   The tumor gene can be completely excised from the cells after they have divided.

10.   The traditional view is that cancer is caused by a series of mutations in tumor suppressor genes.