Chronic Lymphoid leukemia (CLL)

Identification of tumour associated genes in Chronic Lymphoid leukemia (CLL) by suppression subtractive hybridization. CLL is the second most common type of leukemia in adults in the Western world. The hallmark feature of CLL are an increased frequency of circulating clonal leukemic B cells that express CD19, CD23, CD5, and have low levels of surface immunoglobulin (sIg). There is evidence that genetic components contribute to the aetiology of CLL but no definitive susceptibility genes have been identified. Genome-wide association studies have identified seven genetic variations (SNPs) associated with an increased risk of CLL, however their precise role in CLL pathogenesis is not known.
Functional gene differences between B-CLL cells and normal B cells have been studied by several groups using DNA microarray platforms. Seventy-two genes were identified as significantly up-regulated or down regulated in diseased B-CLL cells. Microarray is a robust method for identifying abnormally expressed genes, but it can identify only known genes and sometimes its reproducibility is compromised depending on array platforms and control samples.

Suppression subtraction hybridization (SSH) is an unbiased method for comparing gene expressions of two tissues or samples. The method identifies genes that are exclusively expressed by a particular group of cells and has been successfully used to identify genes expressed in breast cancer, lung adenocarcinoma, melanoma and other cancers. The advantage of the technique is that novel genes can be identified in addition to known genes. SSH has not previously been used for analysing expressed genes in CLL, but our lab has successfully used SSH method in other settings and will now use it to identify genes that are exclusively expressed in B-CLL cells. We will use blood samples stored in our tissue bank as a source of B-CLL cells and normal B-cells that will be isolated using the FACSAria II cell sorter and subjected to SSH. We will then compare molecular profiles of leukemic and normal B cells at different time points for each patient to identify novel genes involved in the transformation of asymptomatic CLL into aggressive disease.

This project is a joint research effort with Associate Professor Stuart Berzins’ group who are studying other immune cells that may have an important role in the development and progression of CLL.