t(2;18) and t(18;22) variant chromosomal translocations in B cell malignancies

Bcl-2 Family Proteins in Development and Treatment of Malignant Diseases

Proteins of Bcl-2 family are key regulators of mitochondrial pathway of apoptosis. Deregulation of apoptosis disrupts the complex and delicate balance between cell proliferation, survival and death and plays an important role in the development of malignant diseases. In addition to uncontrolled proliferation, alterations in apoptotic proteins are frequently associated with resistance of malignant cells to chemotherapy, leading to ineffective treatment with chemotherapy that primarily acts by apoptosis initiation. Despite the progress in combinatory and biologic therapy, response rates for treatment of different malignant diseases are not high enough. Therefore, new anti-cancer agents that selectively kill tumour cells and spare normal tissues are still urgently needed. Progress in biochemistry and cell biology leading to detailed dissection of cell signalling pathways allows development of new therapeutic strategies targeting different proteins involved in malignant transformation and uncontrolled proliferation of malignant cells. Emerging knowledge on molecular mechanisms of apoptosis deregulation in cancer development has revealed Bcl-2 family proteins as potential targets for drugs discovery. Structural analysis of these proteins together with studies of apoptosis mechanisms have outlined strategies for generation of new drugs, resulting in numerous novel chemical entities with mechanism-based activity. Many of the most logical targets for promoting apoptosis of malignant cells are technically challenging, involving often disruption of protein interactions or changes in gene expression, as opposed to traditional pharmaceutical approach that predominantly attacks enzymes. Understanding of the core components of the apoptotic machinery at the molecular and structural levels may lead to new era in cancer therapy where the intrinsic and acquired resistance of malignant cells to apoptosis can be pharmacologically reversed, reinstating natural pathways of cell suicide.

Secondary chromosomal abnormalities predict outcome in pediatric and adult high-stage Burkitt lymphoma

BACKGROUND

Karyotypic abnormalities in sporadic Burkitt lymphoma (BL) have been described extensively. However, to the authors' knowledge, very limited studies have focused on the secondary chromosomal abnormalities in pediatric BL as compared with those of adult BL and on their prognostic impact.

METHODS

A retrospective analysis was performed in all pediatric and adult patients at 2 institutions, with a morphologic diagnosis of BL, pretherapy tumor karyotype available, and t(8;14), t(8;22), or t(2;8) present.

RESULTS

There were 33 children and 37 adults. The majority of the patients (95%) had Stage III/IV disease. There were no statistically significant differences noted in karyotype complexity and the nature of the chromosomal abnormalities between these 2 groups. Abnormalities of chromosomes 13 (13q) and 22 (22q) had a negative impact on prognosis in children. In adults, abnormalities of chromosome 17 appeared to have a negative impact.

CONCLUSIONS

The current findings suggest that karyotypic information can be used for refining risk stratification in patients with BL.

A novel t(2;6)(p12;q23) appearing during transformation of follicular lymphoma with t(18;22)(q21;q11) to diffuse large cell lymphoma

Follicular lymphoma is characterized genetically by t(14;18)(q32;q21), whereas t(18;22)(q21;q11), a rare variant form of t(14;18), has been preferentially observed in chronic lymphocytic leukemia (CLL). We describe here an unusual case of follicular lymphoma with a t(18;22)(q21;q11), that progressed to diffuse large cell lymphoma with a novel t(2;6)(p12;q23). Spectral karyotyping revealed that add(2)(p12) and add(6)(q23) were derived from a t(2;6)(p12;q23). Fluorescence in situ hybridization analysis confirmed rearrangements of the BCL2 gene at 18q21 and the BCL6 gene at 3q27. Our results indicate that a reciprocal translocation involving 6q23 could be implicated in the progression of follicular lymphoma and that t(18;22) may have a specific role in the pathogenesis of follicular lymphoma as well as CLL.

Rapid detection of IgH/BCL2 rearrangement in follicular lymphoma by interphase fluorescence in situ hybridization with bacterial artificial chromosome probes

Follicular lymphomas (FLs) can be difficult to diagnose on aspirated specimens since the architectural pattern is not present. FLs characteristically have rearrangements in the IgH and BCL2 genes resulting from the reciprocal t(14;18) (q32; q21) translocation. Because of the dispersed distribution of breakpoints, fluorescence in situ hybridization (FISH) using genomic probes that span or flank the breakpoints is ideal for detecting this rearrangement in fine-needle aspiration (FNA) biopsies. To develop a set of probes, a bacterial artificial chromosome library was screened and the clones were mapped by fiber FISH. The probes were produced by the direct incorporation of fluorochrome-labeled nucleotides. The colocalization base FISH assay was applied to Cytospin preparations from FNA biopsies of lymph nodes from 26 patients with FL and 10 patients without FL. In those with FL, the percentage of cells with at least one IgH/BCL2 fusion signal ranged from 22% to 100% (mean, 63%), which was statistically significantly higher than that in FL-negative samples (mean, 2.7%). The probes demonstrated a significantly lower cutoff value (7%) in normal controls and effectively reduced the false-positive rate in FL-negative cases. These results were confirmed with fiber FISH assays on the same specimens. This interphase FISH assay is rapid and reliable for detecting rearrangements in the IGH/BCL2 gene, thereby aiding in the diagnosis of FL on FNA biopsy specimens.

B-CLL cells with unusual properties

In studies concerning the interaction of B-CLL cells and Epstein-Barr virus (EBV), we encountered one patient whose cells had several unusual properties. In addition to the B-cell markers, the CLL cells expressed the exclusive T-cell markers CD3 and CD8 and carried a translocation t(18,22)(q21;q11), involving the bcl-2 and Ig lambda loci. The patient represents the 4th reported CLL case with this translocation. The CLL cells could be infected and immortalized by the indigenous and by the prototype B958 virus in vitro. The T-cell markers were not detectable on the established lines. In all experiments the immortalized lines originated from the CLL cells. Their preferential emergence over virus-infected normal B cells may be coupled to the high expression of the bcl-2 gene due to the translocation. In spite of the sensitivity of CLL cells to EBV infection in vitro, no EBNA-positive cells were detected in the ex vivo population. In vitro, we could generate cytotoxic function in T-lymphocyte cultures which acted on autologous EBV-infected CLL cells. Therefore we assume that if such cells emerged in vivo they were eliminated by the T-cell response.

Apparent absence of BCL-2 rearrangement in ten Saudi follicular lymphomas: A preliminary report

Specific chromosomal translocations are often found to be associated with distinct types of human neoplasms. The t(14;18) is considered to be a cytogenetic hallmark of the follicular lymphomas found mostly in American patients. This chromosomal translocation occurs through a 3' untranslated region (either major breakpoint region [mbr] or minor cluster region [mcr]) of the bcl-2 proto-oncogene in chromosome 18 and the JH region of the immunoglobulin (Ig) gene in chromosome 14. In the present study, the polymerase chain reaction (PCR) was used to detect a fusion DNA fragment generated from bcl-2/JH rearrangement either through mbr or mcr in 10 follicular lymphomas in Saudi Arab patients. Surprisingly, none of these cases showed any evidence of bcl-2 gene rearrangement through mbr or mcr. The absence of usual bcl-2/JH recombination in Saudi follicular lymphomas is intriguing and may suggest that the occurrence and mode of bcl-2 gene rearrangement in this lymphoma varies in different patient populations.