Correlation of t(14;18) translocation breakpoint site with clinical characteristics in follicular lymphoma

BACKGROUND

t(14;18)(q32;q21) translocation is an important genetic feature of follicular lymphoma resulting in antiapoptotic B-cell lymphoma 2 (BCL2) protein overexpression. On chromosome 18 breakpoint-site variation is high but does not affect BCL2. Breakpoint most commonly occurs at major breakpoint region (MBR) but may happen at minor cluster region (mcr) and between MBR and mcr at 3'MBR and 5'mcr. The aim of this study was to analyze the correlation of t(14;18)(q32;q21) breakpoint site with clinical characteristics in follicular lymphoma.

PATIENTS AND METHODS

We included patients diagnosed with follicular lymphoma who received at least 1 cycle of systemic treatment and had the t(14;18)(q32;q21) translocation detected by polymerase chain reaction (PCR) at MBR, mcr or 3'MBR prior to first treatment. Among patients with different breakpoints, sex, age, disease grade, stage, B-symptoms, follicular lymphoma international prognostic index (FLIPI), presence of bulky disease, progression free survival and overall survival were compared.

RESULTS

Of 84 patients, 63 had breakpoint at MBR, 17 at mcr and 4 at 3'MBR. At diagnosis, the MBR group had a significantly lower disease stage than the mcr group. Although not significant, in the MBR group we found a higher progression-free survival (PFS) and overall survival (OS), lower grade, age, FLIPI, and less B-symptoms.

CONCLUSIONS

Compared to patients with mcr breakpoint, those with MBR breakpoint seem to be characterised by more favourable clinical characteristics. However, a larger study would be required to support our observation.

Simultaneous Quantification of t(14;18) and HPRT Exon 2/3 Deletions in Human Lymphocytes

Specific recurring chromosomal translocations and deletions are found in a variety of cancers. In hematopoietic malignancies, many of these chromosomal aberrations result from mistakes involving V(D)J recombination. V(D)J recombination is required for the formation of functional T-cell receptor genes in T-cells and antibody genes in B-cells. This is an inherently dangerous process, however, because double-strand breaks are introduced into the chromosomes. Molecular evidence indicates that failure of the fidelity of this process results in the activation of proto-oncogenes or the inactivation of tumor suppressor genes. Here we describe sensitive, quantitative PCR assays for the measurement of such events in human lymphocytes. One assay measures the frequency of t(14;18) translocations that result in the dysfunctional regulation of the anti-apoptotic gene BCL-2. The other assay measures the frequency of a deletion caused by illegitimate V(D)J recombination in the X-linked HPRT gene.

MRD Detection in B-Cell Non-Hodgkin Lymphomas Using Ig Gene Rearrangements and Chromosomal Translocations as Targets for Real-Time Quantitative PCR

Minimal residual disease (MRD) diagnostics is of high clinical relevance in patients with indolent B-cell non-Hodgkin lymphomas (B-NHL) and serves as a surrogate parameter to evaluate treatment effectiveness and long-term prognosis. MRD diagnostics performed by real-time quantitative PCR (RQ-PCR) is still the gold standard and currently the most sensitive and the most broadly applied method in follicular lymphoma (FL) and mantle cell lymphoma (MCL). Alternatively, droplet digital PCR (ddPCR) can be used for MRD monitoring in multiple myeloma, mantle cell lymphoma, and follicular lymphoma with comparable sensitivity, accuracy, and reproducibility.The most broadly applicable MRD target in B-NHL is the junctional regions of the rearranged immunoglobulin heavy chain gene (IGHV). Chromosomal translocations like the t(14;18) translocation in FL and t(11;14) translocation in MCL can be used as MRD target in selected lymphoma subtypes. In patients with B-cell chronic lymphocytic leukemia, both flow-cytometry and RQ-PCR are equally suited for MRD assessment as long as a sensitivity of 10^-4 shall be achieved.MRD diagnostics targeting the IGHV gene is complex and requires extensive knowledge and experience because the junctional regions of each lymphoma have to be identified before the patient-specific RQ-PCR assays can be designed for MRD monitoring. In addition, the presence and load of somatic hypermutation (SHM) within the rearranged IG heavy variable (IGHV) gene occurring as during B-cell development of germinal center and post-germinal center lymphomas may hamper appropriate primer binding leading to false-negative results. The translocations mentioned above have the advantage that consensus forward primers and probes, both placed in the breakpoint regions of chromosome 18 in FL and chromosome 11 in MCL, can be used in combination with a reverse primer placed in the IGH joining region of chromosome 14. RQ-PCR-based methods can reach a good sensitivity (≤10^-4). This chapter provides all relevant background information and technical aspects for the complete laboratory process from detection of the clonal IGHV gene rearrangement and the chromosomal translocations at diagnosis to the actual MRD measurements in clinical follow-up samples of B-NHL. However, it should be noted that MRD diagnostics for clinical treatment protocols has to be accompanied by regular international quality control rounds to ensure the reproducibility and reliability of the MRD results.

Droplet Digital PCR for Minimal Residual Disease Detection in Mature Lymphoproliferative Disorders

Minimal residual disease (MRD) detection has a powerful prognostic relevance for response evaluation and prediction of relapse in hematological malignancies. Real-time quantitative PCR (qPCR) has become the settled and standardized method for MRD assessment in lymphoid disorders. However, qPCR is a relative quantification approach, since it requires a reference standard curve. Droplet digital^TM PCR (ddPCR^TM) allows a reliable absolute tumor burden quantification withdrawing the need for preparing, for each experiment, a tumor-specific standard curve. We have recently shown that ddPCR has a good concordance with qPCR and could be a feasible and reliable tool for MRD monitoring in mature lymphoproliferative disorders. In this chapter we describe the experimental workflow, from the detection of the clonal molecular marker to the MRD monitoring by ddPCR, in patients affected by multiple myeloma, mantle cell lymphoma and follicular lymphoma. However, standardization programs among different laboratories are needed in order to ensure the reliability and reproducibility of ddPCR-based MRD results.

The BCL2 E17 and SP66 antibodies discriminate 2 immunophenotypically and genetically distinct subgroups of conventionally BCL2-"negative" grade 1/2 follicular lymphomas

Follicular lymphoma (FL) is characterized by the translocation t(14;18)(q32;q21) resulting in constitutive overexpression of BCL2. However, in 10% to 15% of FL grade 1/2, immunohistochemical staining for BCL2 remains negative. To analyze the incidence of BCL2 negativity and the underlying molecular mechanisms in FL grade 1/2, BCL2 expression was investigated with 3 antibodies (clones 100D5, E17, SP66). The presence of a break in the BCL2 locus was determined by fluorescence in situ hybridization. The region of the BCL2 gene where the epitope of the standard BCL2 antibody resides was sequenced. Twenty-two (9.2%) of 240 identified cases of FL grade 1/2 were negative with the standard BCL2 antibody. Of these, 12 cases (55%) carried a break in the BCL2 gene locus, which, in all but one case, correlated with BCL2 expression using the alternative antibodies E17 and SP66 and with missense mutations of BCL2. Ten (45%) of the 22 cases had an intact BCL2 gene locus; 2 cases carried a BCL6/IGH translocation. All 10 cases were negative for the E17/SP66 antibodies and showed a wild-type sequence of BCL2. Six of these showed an aberrant phenotype, with CD10 negativity (30%) or CD23 expression (30%). In summary, the alternative E17/SP66 antibodies identify 2 immunohistochemically and genetically distinct subgroups of BCL2-"negative" FL grade 1/2.

Breast systemic follicular lymphoma in a man: a case report

INTRODUCTION

Breast involvement by non-Hodgkin lymphoma is particularly rare in men. We describe the case of a patient with a rapidly growing, painless gynecomastia-like nodule in the left breast. On ultrasonography, the nodule was suspicious for breast carcinoma.

CASE PRESENTATION

A breast biopsy from a 54-year-old Caucasian man showed the morphoimmunophenotypical features of grade 3 follicular lymphoma. Moreover, fluorescence in situ hybridization analysis showed a t(14,18) translocation suggesting breast involvement by a systemic lymphoma rather than a primary breast lymphoma. The histological diagnosis was subsequently confirmed after nodule excision. Mediastinal and abdominal node involvement was then identified on computed tomography and positron emission tomography scans during staging examinations. Our patient was treated with chemotherapy. After three years our patient experienced a right retro-areolar relapse. He then received two further cycles of chemotherapy but developed a myeloid acute leukemia and, as a result of this, he subsequently died.

CONCLUSIONS

The rarity of breast lymphomas, especially in men, and the problems related to the therapeutic choices with these tumors require molecular techniques in association with classical histological diagnosis.