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Tumor evolutionary directed graphs and the history of chronic lymphocytic leukemia.

Research paper by Jiguang J Wang, Hossein H Khiabanian, Davide D Rossi, Giulia G Fabbri, Valter V Gattei, Francesco F Forconi, Luca L Laurenti, Roberto R Marasca, Giovanni G Del Poeta, Robin R Foà, Laura L Pasqualucci, Gianluca G Gaidano, Raul R Rabadan

Indexed on: 17 Dec '14Published on: 17 Dec '14Published in: eLife



Abstract

Cancer is a clonal evolutionary process, caused by successive accumulation of genetic alterations providing milestones of tumor initiation, progression, dissemination, and/or resistance to certain therapeutic regimes. To unravel these milestones we propose a framework, tumor evolutionary directed graphs (TEDG), which is able to characterize the history of genetic alterations by integrating longitudinal and cross-sectional genomic data. We applied TEDG to a chronic lymphocytic leukemia (CLL) cohort of 70 patients spanning 12 years and show that: (a) the evolution of CLL follows a time-ordered process represented as a global flow in TEDG that proceeds from initiating events to late events; (b) there are two distinct and mutually exclusive evolutionary paths of CLL evolution; (c) higher fitness clones are present in later stages of the disease, indicating a progressive clonal replacement with more aggressive clones. Our results suggest that TEDG may constitute an effective framework to recapitulate the evolutionary history of tumors.