Cytogenetic and molecular determinants of aggressive form of chronic lymphocytic leukemia

Abstract

Chronic lymphocytic leukemia (CLL) mainly affects people older than 60 years. Accumulation of morphologically mature but dysfunctional B-lymphocytes in the bone marrow, lymph nodes and peripheral blood is a characteristic feature of this disease. Chromosomal aberrations are observed in lymphocytes of most CLL patients. Typical alterations include deletions of 13q14 and 11q, trisomy 12, and deletions of 17p. Altered expression of the genes located within involved regions, i.e. microRNA15/16 (13q14.3), ATM (11q22-q23) or TP53 (17p13) may be associated with the development and progression of the disease. Cryptic mutations may also contribute to leukemogenesis. Among others, they affect TP53, NOTCH1, SF3B1 and BIRC genes.

CLL is a disease with heterogeneous course. There are two clinical forms – indolent and aggressive. The former is characterized by long time to first treatment and demise usually occurs because of coexisting diseases or is associated with leukemia-dependent immunodeficiency. Rapid clinical course and short overall survival, sometimes in spite of appropriate treatment implementation, is typical for aggressive form of CLL. For patients with this form, the moment of treatment initiation and the choice of first-line therapy are especially important, and depend inter alia on prognostic and predictive factors.

Established poor prognostic factors in CLL include chromosomal aberrations, i.e., deletion of 17p or 11q, high ZAP-70 kinase expression, mutations/deletions of TP53, and lack of mutation of immunoglobulin heavy chain variable region genes (IgVH).

In this paper we tried to point out the importance of some of the prognostic and predictive factors used routinely in the diagnostic management of CLL. Prognostic and predictive potential of microRNA expression level and recently described cryptic changes in the TP53, NOTCH1, SF3B1 and BIRC3 have also been presented.