A t(4;13)(q21;q14) translocation in B-cell chronic lymphocytic leukemia causing concomitant homozygous DLEU2/miR15a/miR16-1 and heterozygous ARHGAP24 deletions

13q14 deletion is the most recurrent chromosomal aberration reported in B-CLL, having a favorable prognostic significance when occurring as the sole cytogenetic alteration. However, its clinical outcome is also related to the deletion size and number of cells with the del(13)(q14) deletion. In 10% of cases, 13q14 deletion arises following a translocation event with multiple partner chromosomes, whose oncogenic impact has not been investigated so far due to the assumption of a possible role as a passenger mutation. Here, we describe a t(4;13)(q21;q14) translocation occurring in a B-CLL case from the diagnosis to spontaneous regression. FISH and SNP-array analyses revealed a heterozygous deletion at 4q21, leading to the loss of the Rho GTPase Activating Protein 24 (ARHGAP24) tumor suppressor gene, down-regulated in the patient RNA, in addition to the homozygous deletion at 13q14 involving DLEU2/miR15a/miR16-1 genes. Interestingly, targeted Next Generation Sequencing analysis of 54 genes related to B-CLL indicated no additional somatic mutation in the patient, underlining the relevance of this t(4;13)(q21;q14) aberration in the leukemogenic process. In all tested RNA samples, RT-qPCR experiments assessed the downregulation of the PCNA, MKI67, and TOP2A proliferation factor genes, and the BCL2 anti-apoptotic gene as well as the up-regulation of TP53 and CDKN1A tumor suppressors, indicating a low proliferation potential of the cells harboring the aberration. In addition, RNA-seq analyses identified four chimeric transcripts (ATG4B::PTMA, OAZ1::PTMA, ZFP36::PTMA, and PIM3::BRD1), two of which (ATG4B::PTMA and ZFP36::PTMA) failed to be detected at the remission, suggesting a possible transcriptional remodeling during the disease course. Overall, our results indicate a favorable prognostic impact of the described chromosomal aberration, as it arises a permissive molecular landscape to the spontaneous B-CLL regression in the patient, highlighting ARHGAP24 as a potentially relevant concurrent alteration to the 13q14 deletion in delineating B-CLL disease evolution.

Mutation status and immunoglobulin gene rearrangements in patients from northwest and central region of Spain with chronic lymphocytic leukemia

The aim of this study was to investigate the frequency and mutation status of the immunoglobulin heavy variable chain (IGHV) in a cohort of 224 patients from northwest and central region of Spain diagnosed with chronic lymphocytic leukemia (CLL), and to correlate it with cytogenetic abnormalities, overall survival (OS) and time to first treatment (TTFT). 125 patients had mutated IGHV, while 99 had unmutated IGHV. The most frequently used IGHV family was IGHV3, followed by IGHV1 and IGHV4. The regions IGHV3-30, IGHV1-69, IGHV3-23, and IGHV4-34 were the most commonly used. Only 3.1% of the patients belonged to the subfamily IGHV3-21 and we failed to demonstrate a worse clinical outcome in this subgroup. The IGHV4 family appeared more frequently with mutated pattern, similar to IGHV3-23 and IGHV3-74. By contrast, IGHV1-69 was expressed at a higher frequency in unmutated CLL patients. All the cases from IGHV3-11 and almost all from IGHV5-51 subfamily belonged to the group of unmutated CLL.