Mice genetically altered to grow malignant tumors will give researchers a more accurate picture of how cancer develops, says a spokesman for Du Pont, which will begin selling the mice next year.

The mouse, called "OncoMouse," will be sold to government and university laboratories, the giant chemical company announced Tuesday.The mice may enable researchers to accelerate the screening of new and existing chemicals and methods to either treat or prevent cancer, Du Pont spokeman Roger Morris said in a telephone interview Tuesday from the company's headquarters in Wilmington, Del.

Another potential use for the mice would be to test substances to determine if they cause cancer, a process that usually takes about two years and $2 million per substance, he said.

The animals were developed by Harvard University, and Du Pont has commercial rights to the animals under an agreement with Harvard, Morris said.

In April, Harvard received the first U.S. patent granted for an animal for the genetically engineered mouse, which contains a gene that makes it more susceptible to cancer.