Abstract: This invention relates to modulating cellular apoptosis in an animal by regulating the quantity of functional KILLER/DR5 receptor protein molecules in the target cell(s) of said animal, increasing the effectiveness of certain therapies such as chemotherapy and radiotherapy. Such modulation increases the difference in toxicity response between target cell(s) and non-target cell(s) in response to a therapy or treatment and comprises upregulation of wild-type proteins in cells targeted for increased apoptosis or upregulation of loss-of-function proteins in cells targeted for decreased apoptosis. The methods of this invention comprise administering a nucleic acid sequence encoding a wild-type KILLER/DR5 receptor protein or a nucleic acid sequence encoding a loss-of-function mutant KILLER/DR5 receptor protein to said animal. The pharmaceutical compositions of this invention comprise a loss-of-function KILLER/DR5 receptor protein.

Abstract: The invention relates to a method of conferring radiation sensitivity on a tumor cell comprising administering to the cell an inhibitor of a protein product which participates in the ras signalling pathway, whereby inhibition of the protein product confers radiation sensitivity on the cell.