The genetic variability of a tumor could be a predictor for its aggressiveness: the greater the variability in gene expression, the more aggressive the tumor is likely to be. This is the hypothesis that the centro nacional de investigaciones oncologicas (cnio (CNIO) Structural Biology and Biocomputing Programme, led by Dr. Alfonso Valencia, is testing, after their findings on chronic lymphocytic leukemia (CLL), published online on January 28, 2015 in an open-access article in the journal Genome Medicine. The team analyzed gene expression in two cohorts of patients with CLL, the most common blood cancer in adults that is characterized by an overproduction of B-lymphocytes in the bone marrow and the lymph nodes. This cancer is classified into two subtypes with very different clinical outcomes: on one hand, patients with IgVH gene mutations have a good prognosis --the illness is less aggressive, it progresses very slowly and usually doesn't require treatment-- and survive for more than 20 years; on the other hand, patients with non-mutated CLL have a more aggressive disease that progresses faster, and has an average survival rate of under 10 years. The researchers examined a total of 70 mutated and 52 non-mutated CLL samples, as well as 20 control samples taken from healthy individuals. In light of their findings, the team concludes that non-mutated leukemia, i.e., the more aggressive type, shows increased gene expression variability across individuals; whereas gene expression variability is lower in the less aggressive, mutated leukemia. These observations were further validated by comparing them against a second sample group consisting of 24 mutated and 36 non-mutated CLL samples.
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