21.   Chemotherapy is a nonspecific approach to killing cancer cells.

22.   Doctors suspect that air bubbles produced by the machine may block blood flow through minute vessels inside the skull, killing brain cells.

23.   Doxil is a chemotherapy drug wrapped inside a fatty layer that helps the drug find and kill cancer cells over time while minimizing damage to healthy tissue.

24.   Drugs cannot reach places where blood does not circulate, and radiation fails in these zones because it needs oxygen to kill cells.

25.   Different cells send signals, flag down messages, kill other cells or eat the remains of conquered pathogens.

26.   Doctors would give patients chemicals that kill cancer cells but take out healthy ones, too.

27.   Eventually they kill the cell, perhaps by simply blocking its molecular traffic.

28.   For example, in sub-lethal doses, the toxin has been seen to enter and kill tumor cells.

29.   For prostate cancer, for example, scientists might add a gene that would kill prostate cells on command.

30.   For decades, cancer treatment has involved highly toxic medicine that killed cancer cells but also killed some healthy cells.