14q deletions are associated with trisomy 12, NOTCH1 mutations and unmutated IGHV genes in chronic lymphocytic leukemia and small lymphocytic lymphoma

Deletions of the long arm of chromosome 14 [del(14q)] are rare but recurrently observed in mature B-cell neoplasms, particularly in chronic lymphocytic leukemia (CLL). To further characterize this aberration, we studied 81 cases with del(14q): 54 of CLL and 27 of small lymphocytic lymphoma (SLL), the largest reported series to date. Using karyotype and fluorescence in situ hybridization (FISH), the most frequent additional abnormality was trisomy 12 (tri12), observed in 28/79 (35%) cases, followed by del13q14 (12/79, 15%), delTP53 (11/80, 14%) delATM (5/79, 6%), and del6q21 (3/76, 4%). IGHV genes were unmutated in 41/53 (77%) patients, with a high frequency of IGHV1-69 (21/52, 40%). NOTCH1 gene was mutated in 14/45 (31%) patients. There was no significant difference in cytogenetic and molecular abnormalities between CLL and SLL. Investigations using FISH and SNP-array demonstrated the heterogeneous size of the 14q deletions. However, a group with the same del(14)(q24.1q32.33) was identified in 48% of cases. In this group, tri12 (P = 0.004) and NOTCH1 mutations (P = 0.02) were significantly more frequent than in the other patients. In CLL patients with del(14q), median treatment-free survival (TFS) was 27 months. In conclusion, del(14q) is associated with tri12 and with pejorative prognostic factors: unmutated IGHV genes (with over-representation of the IGHV1-69 repertoire), NOTCH1 mutations, and a short TFS.

Sex chromosome loss may represent a disease-associated clonal population in chronic lymphocytic leukemia

Whether sex chromosome loss (SCL) is an age-related phenomenon or a cytogenetic marker of hematological disease is unclear. To address this issue in chronic lymphocytic leukemia (CLL), we investigated 20 cases with X or Y chromosome loss detected by conventional cytogenetics (CC). The frequency of SCL was low in CLL (2.3%). It was the sole abnormality, as detected by CC, in 10/20 (50%) patients. Fluorescence in situ hybridization (FISH) analyses confirmed SCL in all patients tested, present in 5-88% of cells (median: 68%). Deletions of 13q were observed by FISH in 16/20 (80%) patients. Compared with CLL without SCL, SCL was significantly associated with 13q deletion, especially when bi-allelic (P = 0.04). Co-hybridization analyses showed that SCL could be a concomitant, primary or secondary change, or be present in an independent clone. FISH analyses were performed on blood sub-populations isolated by Ficoll or flow cytometry. Comparing mononuclear cells (including CLL cells) and polynuclear cells separated by Ficoll, a maximum of 2% of polynuclear cells were found with SCL, whereas mononuclear cells exhibited a significantly higher loss frequency (range: 6-87%) (P = 0.03). Comparing B-cells (including CLL cells) and T-cells sorted by flow cytometry, the proportion of B-CD19+ cells with SCL was significantly higher (range: 88-96%) than that observed in T-CD3+ cells (range: 2-6%) (P = 0.008). We conclude that SCL has to be considered as a clonal aberration in CLL that may participate in the oncogenic process.