Gene Test Breakthrough

In the February 17th issue of the journal Nature, Johns Hopkins scientists announced the development of a new technique, called Conversion, that greatly improves the ability to detect genetic mutations associated with hereditary colorectal cancer. Conversion does not replace conventional gene testing techniques, but, by allowing the genes inherited from each parent to be analyzed individually, it dramatically increases the sensitivity of the tests.

As many families with hereditary non-polyposis colorectal cancer (HNPCC) know, genetic testing can be a frustrating experience. Up to 50% of families with histories characteristic of HNPCC that have undergone genetic testing have not received a clear answer about their genetic status because technology has not been sophisticated enough to detect their mutations.

Each person carries two copies of every gene, one inherited from the father, one from the mother. Current gene tests analyze both copies of the potentially mutated genes at the same time. If a portion of one gene was deleted, that deletion mutation could be masked, or hidden, by the normal gene. Conversion separates the two copies of the gene, allowing them to be analyzed individually and thereby "unmasking" the mutated gene.

The Conversion method has only been tested so far on colon cancer mutations, but the technique should be applicable to other hereditary cancers, including breast and kidney cancer.

Testing for HNPCC and FAP (Familial Adenomatous Polyposis) using the Conversion method will be available through Johns Hopkins in conjunction with genetic counseling and risk assessment in the summer of 2000. For more information and updates on availability, please call (410) 955-4041.

PCR (Polymerase Chain Reaction) is a technique used to amplify, or increase, the number of copies of a gene.