Researchers at the BC Cancer Agency have identified a never before seen mutation (or DNA spelling mistake), in the two most common types of non-Hodgkin’s lymphoma. No other types of lymphoma or other cancers have been found to contain this particular mutation.

What makes this discovery especially significant is the recurrence of this mutation at the same site in a gene called EZH2. Usually mutations are observed in different sites in individual tumours, rather than affecting exactly the same part of the gene. This means the mutation can be considered a marker for the sub-types of lymphoma studied and will aid in diagnosis and predicting treatment outcome.

Even more important, this could potentially lead to specifically targeted medications that treat the lymphoma cells but would be less likely to produce side effects because the patient’s normal cells would be unaffected.

Using the same high-throughput DNA sequencing techniques that were recently used to sequence a breast cancer genome, researchers studied cancer cells from more than 20 lymphoma patients. In total, the DNA sequence of thousands of genes in malignant cells from 31 patients with diffuse large B cell lymphoma and the entire DNA in all the chromosomes of the malignant cells of one patient with follicular lymphoma. 

When the mutation was found at exactly the same position in many of these cases, further lymphoma patients’ malignant cells were examined and were found to be mutated in the same way in almost one quarter of the cases. This is one of the most frequently mutated single genes ever found in lymphomas.

About Lymphoma
Lymphoma is the fifth most common cancer in Canada, and there is an estimated 1,000 new cases diagnosed every year in B.C. It is the fastest growing cancer in North America with a three percent annual increase in incidence.

Lymphomas are cancers that originate from white blood cells known as B-lymphocytes that circulate in the lymph vessels throughout the body. A diagnosis of lymphoma is made when a small piece of the lymphoma (a biopsy) is surgically removed. The tissue can provide clues to what type of lymphoma is present and how the patient will respond to treatment.

This study focused on two of the most common types of non-Hodgkin’s lymphomas, diffuse large B-cell lymphoma and follicular lymphoma, which are named for their appearance under the microscope. Diffuse large B cell lymphoma is an aggressive cancer that can only be cured in about 65 percent of patients and requires strong doses of chemotherapy. Follicular lymphoma is a more slowly growing cancer that cannot be cured, but it can be kept in check for long periods of time with relatively mild chemotherapy.