Nucleotide sequence, transcription map, and mutation analysis of the 13q14 chromosomal region deleted in B-cell chronic lymphocytic leukemia

Abstract

IntroductionB-cell chronic lymphocytic leukemia (B-CLL) represents the most common leukemia in the Western countries with an estimated incidence of 1 per 100 000 per year. The disease is characterized by the monoclonal expansion of B lymphocytes expressing the CD5 marker and exhibiting a long life span, possibly because of a perturbed apoptotic program. 1 Current knowledge of the molecular pathogenesis of B-CLL is limited because no specific genetic alteration has yet been associated with this disease. In particular, B-CLL is not associated with reciprocal balanced chromosomal translocations. 2 Accordingly, none of the proto-oncogenes involved in chromosomal translocations in other mature B cell malignancies, including cyclin D1, 4 Although in a fraction of B-CLL cases, inactivation of the tumor suppressor gene p53 (on chromosome 17p13) and deletions or mutations of the ATM gene (on chromosome 11q22-23) have been reported, 5-9 such lesions were observed in late stages of the disease and may not represent primary tumorigenic events.Chromosome 13q14 deletions (approximately 50% of the patients) 2,10,11 are the commonest chromosomal alterations associated with B-CLL, followed by structural aberrations of chromosome 11q (19% of the cases) and trisomy of chromosome 12 (15%). 2 Moreover, chromosome 13 deletions can be the only cytogenetically detectable abnormality, suggesting an early role in B-CLL pathogenesis. Together, these findings point to the presence in this region of a tumor suppressor gene whose loss or inactivation may be crucial for the leukemogenesis.Deletions of chromosome 13q14 have also been reported in a variety of human tumors, including various other types of lymphoid tumors 12-17 and myeloid leukemias, 18 as well as prostate, 19,20 head and neck, 21 and non-small-cell lung cancers. 22 Although the deleted region of chromosome 13q14 has not yet been defined precisely in most of these neoplasms, these observations suggest that a common tumor suppressor gene may reside on this chromosomal segment.To identify the B-CLL-associated tumor suppressor gene, we previously constructed a high-density contiguous cosmid-based physical map encompassing the deleted interval. 10 This map allowed us to demonstrate that somatic loss at 13q14 occurs in 54% of the patients 10 (and unpublished results) and that the loss is monoallelic in 81% of such cases and biallelic in the remaining 19%. A minimal deleted region (MDR) in B-CLL, spanning less than 300 kilobase (kb) and representing the site of the B-CLLassociated putative tumor suppressor gene, was assigned on our For personal use only. on April 29, 2019. by guest www.bloodjournal.org From physical map in the interval between markers 173a12-82 and 138G4/1.3R. 10 This interval has also been confirmed by other studies. 13 In fact, the MDR exhibits a partial overlap with the regions of deletion as assigned in additional reports, [23][24][25][26] and it includes a locus of 10 kb that was previously defined as a minimal consensus for 13q14 deletion in B-CLL, based on the ...

Role of miR-15/16 in CLL

“…A number of years ago, several laboratories used positional cloning and sequencing of a region of 41 Mb at the deleted region to identify a tumor-suppressor gene at 13q14. 8,9 Detailed genetic analysis of protein-coding genes located in or close to the deleted region, including loss of heterozygosity (LOH) studies, mutation, and expression analysis, failed to show that any of these genes can function as tumor suppressors. And none of these known genes were found inactivated in CLL by mutations or deletions.…”

“…And none of these known genes were found inactivated in CLL by mutations or deletions. [8][9][10][11] In 2001, we generated somatic cell hybrids between mouse and CLLs cells carrying 13q14 deletion and translocation. Analysis of these hybrids revealed that 13q14 tumor-suppressor gene lies within a 30-kb region between exons 2 and 5 of the DLEU2 gene ( Figure 1).…”

“…12 In contrast, expression of several protein-coding genes in the region in CLL was not affected by the 13q14 deletions. 8,9,13 This was the first demonstration of the involvement of non-coding RNA in human disease. 12 The microRNAs are a large family of highly conserved noncoding genes thought to be involved in tissue-specific gene regulation.…”

Mantle cell lymphomas with clonal immunoglobulin V3–21 gene rearrangements exhibit fewer genomic imbalances than mantle cell lymphomas utilizing other immunoglobulin V genes

“…At present, a few candidate genes have been identified in the 13q14 region; however, it is not known if they are disease-related. 17,18 The presence of 13q14 deletions in both chronic lymphocytic leukemia and mantle cell lymphoma may indicate a common genetic component involved in the tumorigenesis of the two malignancies. Another possible mechanism is that different, but closely linked genes may be involved.…”

“…3 Characterization of variable heavy chain (V H ) gene usage has recently been performed in mantle cell lymphoma, revealing that two particular V H gene segments of the immunoglobulin (Ig) locus were preferentially used, namely V H 3-21 (18%) and V H 4-34 (16%). 2,6 Interestingly, the tumor samples with V H 3-21 gene usage almost exclusively expressed lambda light chains, and also in most cases utilized the same V l light chain gene (V l [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. 6 In addition, this group has been shown to have a significantly better prognosis in one report and in other studies displayed a clear tendency towards improved survival compared to mantle cell lymphomas utilizing other V H genes.…”