Mutation Analysis Used to Diagnose Leukemia

Mutation analysis offers prognostic and predictive information for B-cell chronic lymphocytic leukemia (B-CLL).

P53 is a tumor-suppressor gene that stops cell division when DNA damage is present. When the p53 gene does not function normally, genetic mutations that can occur in dividing cells remain unchecked, thereby leading to the accumulation of abnormal, malignant cells. Mutations in p53 are present in more than 50% of all human cancers, including colon, breast, lung, bladder, brain, liver, and hematologic malignancies. Based on p53 mutation analysis, Genzyme Corp. (Cambridge, MA, USA) has now developed a diagnostic test for B-CLL.

A significant number of patients with B-CLL have a dysfunctional p53 gene caused by mutations and deletions, and this number increases as the disease progresses. Studies show that p53 is a poor prognostic factor in B-CLL. Currently, physicians generally test for p53 deletions using fluorescense in-situ hybridization (FISH). FISH detects a deletion of a fragment of chromosome 17 that bears the p53 gene. However, B-CLL patients may have a p53 deletion, mutation, or both. Genzyme's new test is a gene-sequencing assay that detects specific mutations in the p53 gene with a higher degree of sensitivity than FISH alone, thereby providing more comprehensive diagnostic information for high-risk patients.

With the new availability of the p53 mutation analysis, Genzyme is expanding its diagnostic menu for B-CLL patients. The company also offers a minimal residual disease test, which detects very low levels of disease in B-CLL patients.

Chronic lymphocytic leukemia (CLL) is the most prevalent form of adult leukemia, and is characterized by the accumulation of functionally immature white blood cells (lymphocytes) in the bone marrow, blood, lymph tissue, and other organs. About 95% of CLL cases involve cancerous B cells. Because these B cells have a longer than normal life span, they begin to build up and "crowd out” the normal, healthy blood cells. The accumulation of functionally immature cells in the bone marrow can become fatal.

Genzyme has also introduced an important new test to monitor drug resistance in chronic myeloid leukemia patients who are treated with Gleevec (imatinib mesylate) and has launched two new molecular tests for acute myelogenous leukemia (AML). "The availability of these new tests are just the beginning of Genzyme's commitment to deliver life-saving targeted medicine,” said Mara Aspinall, president of Genzyme Genetics, the business unit of Genzyme Corporation focused on the research, development, and provision of complex testing services. "We will continue to develop innovative testing that helps physicians select appropriate therapies for their patients.”



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