Detection of Immunoglobulin Gene Rearrangement in B Cell Neoplasias by Polymerase Chain Reaction Gene Amplification

Immunoglobulin Heavy Chain Gene Rearrangement in B-Cell Non-Hodgkin's Lymphomas Detected by the Polymerase Chain Reaction

Aims and background

Immunoglobulin heavy chain gene rearrangement serves as a marker of clonality and cell lineage in B-cell lymphoproliferative disorders. In this study we used the polymerase chain reaction (PCR) to detect clonal rearrangements of the immunoglobulin heavy chain gene in a group of patients with B-cell lymphomas.

Methods

DNA was extracted from frozen tissue of 40 B-cell non-Hodgkin's lymphomas and subjected to PCR amplification using primers that recognize conserved sequences of the variable and joining regions of the immunoglobulin heavy chain gene.

Results

Monoclonal rearrangements were detected in 23 of 40 malignant B-cell lymphomas. No clonal rearrangements were detected in the 10 control cases.

Conclusions

We conclude that this PCR-based technique may provide a simplified and rapid approach for the detection of clonal immunoglobulin heavy chain gene rearrangements in B-cell lymphomas without recourse to Southern blotting, which can be reserved for cases in which PCR is negative.

Phenotypic and molecular analysis of six human cell lines derived from patients with plasma cell dyscrasia

Cell lines RPMI 8226, JJN3, U266 B1, NCI-H929 (all EBV-) and ARH77 and HS-Sultan (both EBV+) have been extensively characterized in this study. EBV- lines expressed the phenotype (CD138-, CD19+, CD20+) whereas EBV+ were (CD138+, CD19-, CD20-). CD56 expression was restricted to EBV- cell lines, with the exception of U266 B1, whereas PCA-1 was strongly expressed on five of the six cell lines. Only EBV+ cell lines bound peanut-agglutinin (PNA). However, all cell lines bound the lectin Jacalin that binds the same receptor as PNA, irrespective of the receptors sialylation status. By RT-PCR and direct sequencing of their IgH V/D/J domains, ARH77 was demonstrated to use the germline sequence VH4-34/dm1/JH6b, whereas no arrangement was demonstrated for RPMI 8226, suggesting IgH gene deletion or mutation. HLA class I and II antigens were detected using HLA typing on all cell lines warranting their use as suitable targets for HLA-restricted cytotoxic T cells. By sensitive RT-PCR, mRNA for IL-6, IL-6R and TNFbeta was found expressed in all cell lines. IL-1 mRNA expression was predominantly associated with the EBV+ phenotype. Although mRNA for IL-3 and GM-CSF was never detected, transcripts for c-kit ligand and, more commonly, its receptor were. Likewise GM-CSF, M-CSF and erythropoietin mRNA transcripts were detected in the majority of cell lines.

Application of polymerase chain reaction to detect rearrangement of immunoglobulin heavy chain genes in lymphoproliferative disease

As part of our routine work-up in the diagnosis of lymphoproliferative disease, we used a rapid polymerase chain reaction (PCR) assay to amplify the DNA fragments of the framework 3 (FR3) region of the immunoglobulin heavy (IgH) chain genes. The assay does not involve hybridization, nested priming, or sequencing of the amplified PCR product. It was performed on 66 specimens of B-cell lymphoproliferative disease, including acute lymphoblastic leukemia, chronic lymphocytic leukemia, multiple myeloma, hairy cell leukemia and follicular lymphoma. Twenty-six specimens of negative controls, including acute myeloid leukemia, chronic myeloid leukemia in myeloid transformation and idiopathic thrombocytopenic purpura, were also analyzed. The assay was performed with 77% sensitivity and 100% specificity. The standard IgH chain gene rearrangement by Southern blot analysis is reserved for the remaining negative cases if clinically indicated.

Clonality analysis of B-lymphoid proliferations using the polymerase chain reaction

BACKGROUND

Polymerase chain reaction (PCR) based assays are becoming more reliable, simpler, and faster alternatives to traditional Southern blot hybridization (SBH) analysis for the detection of clonal immunoglobulin heavy chain (IgH) gene rearrangements. However, a variety of technical approaches have been reported with markedly different results.

METHODS

We analyzed the frozen tissue of 147 neoplastic and hyperplastic lesions on which SBH had previously been performed. Semi-nested and single-step PCR methods were compared. Consensus primers to the joining segments and the framework region (FR) III of the variable segments of the IgH gene were used. All PCR products were analyzed by polyacrylamide gel electrophoresis (PAGE). Thirteen samples were re-analyzed using a denaturing gradient gel electrophoresis (DGGE) system.

RESULTS

The overall concordance between SBH and semi-nested PCR assays was 80.2%. In the non-Hodgkin's lymphoma (NHL) group, 75% of the cases with IgH rearrangements by SBH were found to be monoclonal by PCR. Regardless of type of lesion, 71.7% of the cases with IgH rearrangements by SBH were found to be clonal by PCR. The concordance between the semi-nested and single-step procedures was 87.1%. DGGE was helpful in clarifying the results for cases in which the PAGE analysis was difficult to interpret.

CONCLUSIONS

PCR analysis of IgH gene rearrangements was found to be an efficient technique for the initial determination of clonality in lymphoid proliferations. The single-step method had an advantage over the semi-nested method because of its simplicity and speed. The DGGE system was useful for the assessment of clonality in cases with equivocal results after PAGE. However, a combination of these techniques in specific cases may achieve higher specificity and sensitivity.

Multiple myeloma, high-dose treatment and autologous stem cell transplantation--current status

High-dose chemo-radiotherapy with autologous stem cell transplantation (ASCT) has introduced the concept of complete remission for multiple myeloma, and can improve survival and life quality for selected groups of myeloma patients. A number of prognostic factors have been identified, where ASCT in early disease, i.e. as part of front-line treatment, seems to be of particular importance for a favourable outcome. Even so, most myeloma patients will not be cured by high-dose therapy, but new strategies such as repeated autografting and post-graft alpha-interferon maintenance treatment seem to add additional advantages with respect to survival and freedom of disease progression. The technical development has enabled efficient in vitro myeloma cell depletion of the autograft as well as highly sensitive detection of minimal residual disease after treatment, but the clinical significance of these issues remains to be determined, and this question is addressed in ongoing gene marking studies. The application of novel therapeutic principles, e.g. gene therapy and immunotherapy, might further ameliorate the outcome for patients with multiple myeloma.

Molecular genetics and lymphoproliferative disorders

Clonality of T- and B-cell lymphoproliferative disorders can be determined by gene rearrangement studies when morphology and surface immunostaining are nondiagnostic. TcR and lg gene rearrangements have been demonstrated in many different hematologic disorders and TcR gene rearrangement has been particularly useful in the diagnosis of patients with CD8 large granular lymphocyte leukemias. TcR gene rearrangement may also be useful to distinguish Hodgkin's disease from T-cell non-Hodgkin's lymphoma. Gene rearrangement is usually performed by Southern analysis, and it is beneficial to run multiple enzyme-probe combinations to maximize the detection of clonal rearrangements. More recently, several laboratories have begun to use polymerase chain reaction (PCR) for gene rearrangement analysis. PCR offers an improved turnaround time, eliminates partial digestion artifacts, and allows for the use of paraffin embedded material. In addition to rearrangements of the TcR and lg genes, analysis of alterations in other genes such as bcl-1, bcl-2, bcl-6, and c-myc are also useful as clonal markers and aid in the classification of lymphomas.

Genetic changes: relevance for diagnosis and detection of minimal residual disease in acute lymphoblastic leukaemia

Cure can now be achieved in a proportion of patients with ALL. However, relapse and eventual treatment failure occur in many cases receiving identical treatment, presumably as a result of failure to eradicate MRD. While for many years marrow morphology has been the standard by which leukaemic remission has been assessed, more sensitive techniques have been developed for detection of MRD including immunophenotypic analysis, and as discussed in this chapter, methods which detect leukemia-associated clonal genetic changes at the karyotypic and genomic levels. Table 10 lists the applicability and sensitivity of various markers used in MRD analysis in ALL. It is apparent that of the karyotypic and molecular approaches described, only PCR-based strategies for detection of either leukaemia-specific translocations or clonal Ag receptor rearrangements are reliably applicable to a high proportion of both B- and T-ALL at sufficiently high sensitivity. Initial clinical studies of patients undergoing therapy for ALL using a variety of PCR-based methods suggest that in some cases a persistent or increasing level of residual disease may be predictive for clinical relapse, although a number of technical factors and the phenomena of oligo-clonality and clonal evolution may limit the usefulness of this analysis in a few instances. From current available data it appears that in order to define the potential predictive value of PCR detection of MRD a large number of patients will need to be prospectively assessed over several years at multiple time points during and after therapy, preferably using more than one semi-quantitative PCR approach. In addition to reliable prediction of clinical relapse allowing appropriate individual treatment modification, progress in the molecular detection of MRD in ALL is also likely to be of benefit in the assessment of the efficacy of autograft purging and the evaluation of new therapeutic strategies such as the use of biological response modifiers to eliminate a low tumour burden.

Immunoglobulin and T-cell receptor delta gene rearrangements are rarely found in myelodysplastic syndromes in chronic phase

Clonality, in MDS, can only be assessed in patients with chromosomal rearrangements or in females heterozygote for X chromosome restricted polymorphisms. "Illegitimate" rearrangements of the immunoglobulin heavy chain (IgH) gene and incomplete rearrangements involving V delta 2 and D delta 3 segments of the T-cell receptor delta (TcR delta) gene are seen in some cases of AML, and AML post-SMD, and can be detected by a sensitive PCR method. In order to analyse clonality in additional cases in MDS, we looked for Ig H and TcR delta gene rearrangement by PCR in 95 cases of MDS. A rearrangement of the Ig H gene was seen in 2 of the 95 patients: in the circulating blood of 2 of the 36 cases of chronic myelomonocytic leukaemia (CMML) and in none of the marrow samples of the other 59 MDS. A rearrangement of the TcR delta gene (involving V delta 2 and D delta 3 segments) was seen in three cases (in the circulating blood of two other CMLL patients, and in the bone marrow of another MDS patient). Twenty-five of the 90 cases of MDS with negative PCR findings, in addition to the five cases with positive PCR findings underwent Southern blot analysis of Ig H and TcR delta genes, and PCR analysis of V delta 1 and J delta 1 segments of the TcR delta gene. Those examinations were normal in all the cases tested. In patients with positive PCR findings for Ig H or V delta 2 D delta 3 rearrangements, the proportion of rearranged cells was evaluated at 1-5% in four cases, and 5-10% in the remaining patient. Because the analysis was performed on total circulating leukocytes or total nucleated marrow cells, the nature of the clonal population in positive cases (lymphoid cells? myeloid cells? blasts?) could not be determined. From a practical point of view, Ig H and TcR delta gene rearrangements seem to very rare in MDS, and cannot be used as clonality markers in most cases.

Detection of tumor contamination of peripheral stem cells in patients with lymphoma using cell culture and polymerase chain reaction technology

The important question of whether residual tumor in the bone marrow or peripheral blood stem cell graft contributes to relapse in autologous bone marrow transplantation in patients with non-Hodgkin's lymphoma can be addressed only if there is an accurate and sensitive measurement of tumor cell contamination of the graft. Assays utilizing DNA amplification based on the polymerase chain reaction (PCR) are highly sensitive. Tumor-specific primers and probes can be designed for the clonally rearranged Ig or T cell antigen receptor genes in the original tumors, and these can then be used to detect minimal residual disease in subsequent specimens. Specific translocations can also be exploited as tumor markers, and the t(14;18) translocation has been widely employed for detecting tumor cells in blood and bone marrow samples. Lymphoma cells have also been grown successfully in tissue culture, and the detection of tumor contamination of autologous grafts has been associated with a poorer prognosis in patients with intermediate- or high-grade lymphoma. It is of interest to compare the sensitivity of tumor detection and the predictive value for patient survival of the PCR-based and culture-based assays. The information obtained may help to determine whether minimal tumor contamination of an autologous graft is clinically significant and, if so, the assay(s) that should be employed.

Immature and differentiated neoplastic populations in acute lymphoid leukemia of childhood: biological and clinical implications

Despite significant improvement in the therapy for acute lymphoid leukemia (ALL) of childhood, approximately 30% of patients relapse. Unfortunately, since no successful treatment for recurrent disease has been developed, the majority of these patients die. Recently, we presented evidence consistent with the presence of a limited program of differentiation in B-precursor ALL that is reminiscent of normal B-cell development. We found that ALL cell populations consist of both a subpopulation of progenitors with the immunophenotype of normal B-cell precursors that has self-renewal capability and a second subpopulation with a more mature early B-cell immunophenotype that is without self-renewal capability but can proliferate to a limited extent. In our recent studies we were able to grow the progenitor cells in the ALL blast colony assay and establish their leukemic origin using the polymerase chain reaction. Our results suggest that these progenitors are the cells that sustain the disease. We hypothesize that these cells may remain quiescent, for a time, and either eventually die or regain proliferative capability and cause relapse. Further studies aimed both at detecting residual ALL and determining changes in their biology may provide an understanding of the mechanisms of relapse in this disease.