SYDNEY, Australia — Scientists at a research institute in Sydney have isolated and patented a gene which they say plays a key role in determining whether or not ordinary cells become cancerous.

The researchers at the Victor Chang Cardiac Research Institute now are looking for the molecule involved in the first step in the signaling pathway used by the gene, which is one of a family known as protein tyrosine phosphatase (PTP).

Executive director Robert Graham said the institute's research program originally had been searching for a gene responsible for the enlargement of heart muscles, a condition that leads to heart failure.

During that work, as described in the Aug. 14 issue of the Journal of Biochemistry and disclosed to the Australian media last week, the researchers accidentally found a gene that seemed to control the excessive growth of cancer cells.

Graham said the gene's role was confirmed in two ways. In the first part of the research, ordinary cells were induced to become cancerous in the laboratory by alteration of the N-RAS oncogene, so that the cells were similar to those found in breast and colon cancer. The PTP family gene was then added to the cells, and they stopped dividing.

In the second part of the research, the PTP family gene was damaged in ordinary cells in the laboratory, and those cells then started to divide uncontrollably.

Graham said the protein expressed by the gene is a major part of the complex chemical signaling that goes on inside cells, and the institute researchers now are working on identifying the first step in the signaling system used by the PTP gene.

The work was funded by grants from the Australian National Heart Foundation, as well as grants from the charitable institutions set up in the wake of the death of the Princess of Wales last year. Graham said the institute has been granted a provisional patent on the gene, giving it one year in which to add additional information.

Although there are a number of research steps to take before the work reaches a clinical stage, Graham said he hopes to attract the support of major drug companies. *