Detection of minimal residual cells carrying the t(14;18) by DNA sequence amplification

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.

Detection of chromosomal translocations in leukemia-lymphoma cells by polymerase chain reaction

In recent years many chromosomal translocations involved in leukemia and lymphoma have been defined at the molecular level. In addition to advancing the understanding of pathological mechanisms underlying the transformation process, the cloning and sequencing of the genes altered by the translocations have provided new tools for diagnosis and monitoring of patients. In particular, the polymerase chain reaction (PCR) methodology yields rapid, sensitive and accurate diagnostic and prognostic information. As leukemias carrying certain translocations confer a higher risk of treatment failure, it is important to identify accurately all positive cases in order to give appropriate therapy. An important new initiative in the diagnostical setting and anti-leukemic therapy is the early detection of minimal residual disease (MRD). If MRD, implying an increased risk of relapse, is reliably detected during apparent clinical remission, alternative strategies could be applied early while the malignant cell burden is still minimal. The PCR assays are clearly more sensitive than other methods of MRD detection including morphology, immunophenotyping and cytogenetics; treatment failure is first detectable by PCR followed by cytogenetic relapse and finally clinical disease. PCR assays have been most often used in the MRD analysis of follicular lymphoma with t(14;18), chronic myeloid leukemia and acute lymphoblastic leukemia (ALL) with t(9;22), ALL with t(4;11), and acute myeloid leukemia (AML) with t(8;21) or t(15;17). PCR amplification is applicable to any other translocation provided the translocation is highly associated with the malignancy and the breakpoints are sufficiently clustered; a quickly increasing number of such specific molecular markers are now available for PCR assays. PCR still remains an experimental investigation for the detection of covert disease. However, the clinical relevance of MRD detection should be evaluated separately for each type of leukemia as significant prognostic differences between disease entities were found. This review describes the PCR assays available for the detection of leukemia cells with specific chromosomal translocations and summarizes the experience with the application of PCR techniques in monitoring patients during the course of the disease.

Low-grade lymphomas: new entities and treatment concepts

Therapy for patients with low-grade lymphomas has never been standardized. Recently, new entities have been described which are included in the REAL classification, and whether these entities should be regarded as separate diseases is not yet clear. Regardless, three new developments in the management of patients with low-grade lymphomas deserve special attention for treatment programs in the future. First, it appears that patients with stage I, II, and III low-grade lymphomas may enjoy very prolonged disease-free intervals after treatment with combination chemotherapy and radiation therapy programs. Although investigators disagree on prognostic factors, new features, such as beta 2-microglobulin appear to predict results better than any other feature, and future studies should address this prognostic factor in assessing their results. Second, for patients with advanced stage disease, administration of interferon as maintenance therapy prolongs the disease-free interval, and use of this drug should be further investigated. Finally, molecular studies using PCR for bcl-2 may be clinically relevant in detecting residual disease in patients with follicular lymphomas, and future studies should focus on the value of eliminating the residual disease from blood and marrow.

Detection of major and minor bcr/abl fusion gene transcripts in a patient with acute undifferentiated leukemia secondary to treatment with an alkylating agent

In this paper we describe a patient with bcr/abl positive acute undifferentiated leukemia (AUL) derived from acquired sideroblastic anemia secondary to ifosphamide treatment given for the preceding non-Hodgkin lymphoma of the lung. Cytogenetically, Philadelphia chromosome was not detected through the whole course in this patient, and multiple chromosomal abnormalities including 5q- and monosomy 7 were found at the stage of sideroblastic anemia. The reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed no bcr/abl fusion transcript at the diagnosis of malignant lymphoma. The mRNA encoding the major bcr/abl fusion protein then appeared in the stage of sideroblastic anemia. Finally, the mRNA encoding both major and minor bcr/abl was detected in the stage of AUL transformation. MLL gene rearrangement was not found by RT-PCR analysis at any stage of the disorder. These results may be direct evidence for the induction of the bcr/abl fusion gene by treatment with an alkylating agent (ifosphamide).

Biologic indicators of exposure: are markers associated with oncogenesis useful as biologic markers of effect?

Radiation-induced molecular and cellular alterations play an important role in the transformation of a normal cell into a cancer cell. However, the basic molecular and cellular alterations upon exposure to ionizing irradiation are still poorly understood. Identification of such alterations would be of importance for the assessment of exposure dose, as well as for the assessment of an exposed individual's risk of developing cancer. Extensive studies of the mechanisms of oncogenesis have led to the identification of altered genes, such as proto-oncogenes and tumor suppressor genes as well as other genes intimately involved in cellular proliferation and differentiation, that are more or less frequently associated with a variety of human malignancies. It can be assumed that at least some of these mechanisms are associated with radiation-induced oncogenesis. The longevity of stem cells, particularly those of the hemopoietic system, makes them the prime target cell population to accumulate genetic alterations due to exposure to a variety of agents. Improvements in purification strategies for hemopoietic stem cells, as well as the availability of sensitive techniques such as the polymerase chain reaction (PCR) and flow cytometry analysis, should allow in-depth studies at the molecular and cellular level after exposure to physical and chemical agents.

Long-term disease-free survival after autologous bone marrow transplantation in a primary plasma cell leukaemia: detection of minimal residual disease in the transplant marrow by third-complementarity-determining region-specific probes

Primary plasma cell leukaemia (PPCL) is a rare form of plasma cell neoplasm. Treatments of PPCL have been most disappointing. A patient with PPCL received high-dose melphalan plus total body irradiation and autologous bone marrow transplantation (ABMT). By using third-complementarity-determining region (CDRIII)-specific probes, minimal residual disease (MRD) was detected in remission marrow, collected 1 month before ABMT. MRD was no longer detected by CDRIII-specific probes 6, 19 and 26 months after transplantation. The patient remained in complete remission up to 59 months after ABMT.

Low incidence of mbr bcl-2/JH fusion genes in Hodgkin's disease

Lymph node biopsies from 140 cases of Hodgkin's disease (HD) and from 30 non-malignant lesions were screened for the presence of t(14;18) translocations involving the major breakpoint region (mbr) of the bcl-2 gene and the joining region (JH) of the immunoglobulin heavy chain gene, using a polymerase chain reaction (PCR) assay with subsequent nucleotide sequencing of amplified bcl-2/JH junctional regions. Expression of the bcl-2 protein within the Hodgkin and Reed-Sternberg (HRS) cells was investigated in 86 cases of HD by immunohistochemistry on cryostat or paraffin sections. Although bcl-2 expression could be found in a proportion of neoplastic cells in up to one-third of HD cases, the frequency of t(14;18) gene fusions detected by PCR was low. We identified such gene fusions in only 3 out of 140 (2 per cent) HD cases, one biopsy of which presented with four clonally distinct bcl-2/JH sequences. No t(14;18) was found in any of 30 reactive lymph node lesions. All fusion gene sequences were unique regarding the localization of the chromosome 14 and 18 breakpoints and the extranucleotide N-insertions. None of these gene fusions conformed to t(14;18) breakpoint sequences previously characterized in our laboratories. Our findings point to a mere coincidence in some cases of HD lesions and cells carrying a t(14;18) in the same biopsy and argue against a significant role of bcl-2 in the pathogenesis of HD.

Production of vampire bat plasminogen activator DSPA alpha 1 in CHO and insect cells

Salivary plasminogen activator from the vampire bat Desmodus rotundus (DSPA alpha 1) is a promising new thrombolytic agent. Continuous growth of a stably transfected, methotrexate amplified, dhfr- CHO cell line yields up to 60 mg l-1 of DSPA alpha 1. Utilizing an engineered baculovirus 10 mg l-1 were produced in batches of Sf9 insect cells. Recombinant DSPA alpha 1 is purified from both sources using a one-step purification protocol. Although differences in glycosylation were detected, enzymatic activity and fibrin cofactor dependency are unaffected when DSPA alpha 1 derived from the two expression systems is compared.

Clinical significance of minimal residual disease in leukemia detected by polymerase chain reaction: is molecular remission a milestone for achieving a cure?

Polymerase chain reaction (PCR) technology has been useful in clarifying molecular or minimal residual disease (MRD) status in patients with leukemia. Although PCR has several inherent problems, accumulated data have demonstrated that patients with leukemia harbor PCR-detectable residual disease for a certain period despite clinical remission. This has been for approximately 1 year in childhood acute lymphoblastic leukemia and adult acute promyelocytic leukemia after chemotherapy and for approximately 2 years in chronic myelogenous leukemia after bone marrow transplantation. Ultimately, PCR-undectable residual disease is necessary for achieving cures in most patients. However, it is difficult to make an early prediction of subsequent relapse after obtaining PCR negatively, since the emergence of PCR-detectable disease occurs only several months before clinical relapse. Therefore, PCR negativity is necessary but not sufficient for achieving cures in most patients with leukemia. Periods of persistent PCR-detectable disease will require further investigations for relapse prediction. More accurate serial quantitation would clarify a precise MRD status in leukemia patients and might allow for more accurate prediction of relapse. Since PCR-undectable residual disease is necessary for cures in most patients, it can be proposed that a "molecular remission", defined as PCR-undetectable disease, is a milestone and target for achieving cure by cytoreductive therapy.

Clonal analysis of Hodgkin's disease shows absence of TCR/Ig gene rearrangement, compared with T-cell-rich B-cell lymphoma and incipient adult T-cell leukemia/lymphoma

To better characterize the clonality and pathogenesis of Hodgkin's disease (HD), we used polymerase chain reaction (PCR) and Southern blot to analyze the rearrangement of immunoglobulin (Ig) and T-cell receptor (TCR) genes, the bcl-2 oncogene, and the Epstein-Barr virus (EBV) genotype. In situ hybridization studies of EBV were also done. Twenty-six cases of HD were compared with 15 cases of non-specific lymphadenitis, 7 with incipient adult T-cell leukemia/lymphoma (ATLL), and 4 T-cell rich B-cell lymphomas (TRBL), all of which histologically resembled HD. EBV genes were detected in 20 of 26 HD patients (77%) and in 7 of 15 patients with non-specific lymphadenitis (47%), 5 of 7 with incipient ATLL (71%), and 1 of 4 with TRBL (25%). In contrast to specimens of non-specific lymphadenitis, TRBL, and incipient ATLL, only one EBV genotype was evident in the specimens of HD. EBV latent membrane protein (LMP) was detected immunologically in 16 of 26 HD patients (62%), one of four TRBL (25%) and one of seven incipient ATLL (14%), but it was not evident in non-specific lymphadenitis. The LMP positive cases showed amplified EBV genomes. Only one of the 26 cases of HD had a bcl-2 gene rearrangement by PCR, but this was not seen in any other disease. The bcl-2 protein was detected immunologically in seven of the 26 HD patients (27%) and in one of the seven incipient ATLL cases (14%). EBV has been reported to upregulate bcl-2 expression, but in this study the presence of bcl-2 protein did not correlate with the presence of the t(14;18) translocation or EBV-LMP. All TRBLs showed rearrangement of the immunoglobulin genes by PCR and/or Southern blot, and the giant cells were of B-cell type. All incipient ATLLs displayed rearrangement of the TCR genes, and the giant cells were of T-cell origin. In seven of 26 HD cases, the giant cells were weakly stained with T-cell antibodies, in another seven positive with B-cell antibodies and in 18 instances polyclonally positive for both kappa and lambda. However, PCR and Southern blot displayed only two cases of TCR gene rearrangement, while two others had very weak rearrangements of immunoglobulin gene positive only by PCR. Thus the T and B-cell genotype did not correlate with the T and B-cell phenotype recorded in these cases. The absence of Ig and TCR gene rearrangements seems to be common in HD, compared with in TRBL and incipient ATLL.

BCL2 translocation frequency rises with age in humans

The background frequency of t(14;18) (q32;q21) chromosomal translocations at the locus associated with B-cell leukemia/lymphoma-2 (BCL2) was determined from a survey of the peripheral blood lymphocytes (PBLs) of 53 living individuals and from tissues of 31 autopsies by using a nested PCR assay. The translocation was detected in 55% of PBLs and 35% of autopsied spleens with a frequency of between less than 1 to 853 translocations per million cells. Translocations copurified with B lymphocytes. The frequency of translocations significantly increased with age in PBLs and spleens, as does human risk for lymphoma. Average translocation frequency was more than 40 times greater in the spleen and 13 times greater in the peripheral blood in the oldest individuals (61 yr and older) compared with the youngest individuals (20 yr or younger). Particular t(14;18)-bearing clones persisted over a period of 5 months in two individuals. These findings demonstrate that clones harboring the oncogenic t(14;18) chromosomal translocation are commonly present in normal humans, that such clones are long-lived, and that they rise in frequency with age. A multihit model of lymphomagenesis involving t(14;18) translocation followed by antigen stimulation is proposed.

Polymerase chain reaction (PCR) approach for the evaluation of minimal residual disease in acute leukemia

Evaluation of minimal residual disease (MRD) in different forms of acute leukemias is an expanding field of experimental hematology. Several strategies and techniques, including cytomorphology, immunophenotype and karyotype, have been applied to evaluate MRD, but molecular biology has provided more sensitive and accurate tools to detect the neoplastic clones. This concise review summarizes some of the technical aspects and pitfalls associated with different molecular approaches such as the analysis of clonospecific DNA sequences in lymphoid malignancies and the demonstration of chimeric genomic products generated by chromosomal translocations. The feasibility, specificity and clinical relevance of all these studies will be briefly discussed.

Polymerase chain reaction-based methods for the detection of mutations in oncogenes and tumor suppressor genes

Altered expression of oncogenes and tumor suppressor genes, the normal function of which is to regulate cell growth and differentiation, represents a central event in the pathogenesis of human cancer. Aberrant expression of these genes is often a result of a mutational event. In vitro amplification of DNA with the polymerase chain reaction (PCR) has enormously increased the sensitivity of the methods to detect mutations. These PCR-based techniques have thus become invaluable in the elucidation of the mechanisms of carcinogenesis as well as in molecular genetics. In addition, the precise definition of a mutation at the molecular level can be a very valuable adjunct to the diagnosis and classification of malignancies as well as to their prognostic assessment. In this article several PCR-based strategies are outlined, their applicability in the detection of different types of mutations is discussed, and finally the application of these techniques in fresh and archival tissues is presented.

Major and minor breakpoint sites of chromosomal translocation t(14;18) in subtypes of non-Hodgkin's lymphomas

The frequencies of major breakpoint region (MBR) and minor cluster region (MCR) breakpoint sites of t(14;18) were examined by polymerase chain reaction and Southern blotting in 50 non-Hodgkin's lymphomas with cytogenetic evidence of t(14;18). A translocation breakpoint was detected in 41 cases (82%). The MBR was involved in 66%, and the MCR in 16% of the cases. Most cases in the present series were lymphomas with a follicular or diffuse growth pattern, 38 being of the centroblastic/centrocytic type and eight of the centroblastic type. The series also included four lymphomas of probable non-follicular center cell origin. MBR and/or MCR breakpoints were found in all studied lymphoma subtypes and in the majority of these most of the breakpoints were in the MBR and a minor portion of the breakpoints in the MCR. Our results suggest that a breakpoint site is not related to growth pattern or neoplastic cell type in follicular center cell lymphomas with t(14;18).

Intensive conventional-dose chemotherapy for stage IV low-grade lymphoma: high remission rates and reversion to negative of peripheral blood bcl-2 rearrangement

BACKGROUND

Advanced-stage low-grade lymphoma is characterized by initial responsiveness to many conventional therapies but ultimate relapse. Intensive therapy approaches with non-cross-resistant regimens have not been extensively explored. The polymerase chain reaction (PCR) can be used to monitor for the presence of cells with rearrangement of bcl-2, and provides a sensitive and stringent parameter of disease activity and treatment response that may have clinical utility.

PATIENTS AND METHODS

From 1988 to 1992, 138 evaluable patients were treated with 3 sequential chemotherapy regimens, as well as with interferon alfa 2b (IFN) in combination with corticosteroids. Nineteen patients had serial PCR monitoring for bcl-2 rearrangement.

RESULTS

Among a subset of 58 patients who had an initial phase of IFN plus prednisone, the response rate was 59%, mostly partial remissions (PR). With the chemotherapy program, 65% have achieved complete remission to date, and 30% PR. By PCR analysis, 13 of 19 tested achieved negative status ('molecular remission'), a much higher frequency of molecular remission than has been seen with standard therapies, and these molecular remissions appear to correlate with a lower likelihood of relapse.

CONCLUSIONS

Intensive conventional-dose chemotherapy can achieve high rates of remission, even when monitored by the stringent PCR technique.

Quantitation of follicular non-Hodgkin's lymphoma cells carrying t(14;18) in a patient before and after allogeneic bone marrow transplantation

BACKGROUND

A competitive PCR method was developed, enabling accurate quantitation of residual lymphoma cells carrying the t(14;18) in blood and bone marrow samples of follicular non-Hodgkin's lymphoma (NHL) patients during treatment.

PATIENTS AND METHODS

A patient with residual lymphoma cells received an allogeneic bone marrow transplantation (BMT). Since BMT, the patient has been in continuing clinical complete remission.

RESULTS

Using the competitive PCR and two-step PCR method, we were able to demonstrate a gradual decline in the number of lymphoma cells within consecutive patient blood and bone marrow samples after BMT.

CONCLUSIONS

The competitive PCR is a suitable method for the detection of minimal residual disease. Further research might reveal the clinical relevance of data obtained by this method.

The polymerase chain reaction in diagnosing lymphoid disorders

The application of PCR to lymphoid diagnosis has come a long way in a few years. The technique brings the advantage of rapidity and (relative) ease of use, as well as being inexpensive. Whilst the range of chromosomal abnormalities thus detectable is at present small, the adaptation of PCR to the detection and monitoring of clones is becoming increasingly useful.

Hematogenous spread of malignant melanoma cells in different stages of disease

Patients with malignant melanoma and distant metastases generally have an unfavorable prognosis, with a median survival of about 6 months. The mechanisms of hematogenous spread and implantation of melanoma cells are, however, poorly understood, because the standard diagnostic methods are not sensitive enough to detect oligocellular micrometastases. Recently a method using reverse transcription and polymerase chain reaction to determine tyrosinase mRNA in peripheral blood, which indicates the presence of circulating melanoma cells, has been developed. We utilized this assay to examine blood samples of 56 patients with malignant melanoma in different stages of disease. In one of 10 patients in stage I (localized disease) and in six of 17 patients with regional lymph nodes metastases (stage II) tyrosinase mRNA was detected. Tyrosinase transcripts were found in all 29 patients with distant metastases (stage III). Interestingly, tyrosinase mRNA was also detected in six patients with metastatic amelanotic malignant melanoma. In contrast, tyrosinase mRNA was not detectable in any of 39 healthy subjects or 17 patients with other malignancies. These findings may be helpful to define a patient group at high risk for systemic spread of disease.

Cloning of a breakpoint cluster region at band 3q27 involved in human non-Hodgkin's lymphoma

In a previous cytogenetic analysis, we showed the recurrence of translocations involving band 3q27 and immunoglobulin gene regions in 20 out of 319 patients with non-Hodgkin's lymphoma (NHL). We report here the molecular cloning of the translocation breakpoint from tumor cells of a patient (LAR) with t(3;14)(q27;q32) and the isolation of DNA probes which identify a major translocation cluster region (MTC) at band 3q27. A DNA library from LAR tumor cells was screened with a JH probe and several clones were identified corresponding either to a somatic rearrangement of JGH genes (V4-D2-J6-C mu clonal rearrangement) or to the t(3;14). Analysis of the t(3;14) breakpoint showed that chromosome 3 material was translocated to an inverted 14q32 VH-containing fragment which was itself translocated to the J3 gene. Chromosome 3-assigned probes were used to investigate local DNA rearrangements in a series of NHL with 3q27 translocations. Rearrangements were detected in 13 of 17 patients including 9 of 11 with t(3;14)(q27;q32), 1 of 2 with t(2;3)(p12;q27), 1 of 2 with t(3;22)(q27;q11), and 2 of 2 NHL with translocations not involving an IG gene, namely, t(3;4)(q27;p11) and t(3;7)(q27;p12). The finding of this MTC should be useful for diagnostic and prognostic studies and for the identification of a novel oncogene at band 3q27 involved in the development of B cell NHL.

Detection of chimaerism after bone marrow transplantation using the double amplification refractory mutation system

We have developed a highly sensitive double amplification refractory mutation system (double ARMS) for the detection of extremely low levels of mixed chimaerism after bone marrow transplantation. The system we chose for double ARMS analysis is a highly polymorphic region 5' to the human delta-globin gene. Double ARMS analysis was found to correlate well with an established minisatellite system and was shown to demonstrate a very low level of mixed chimaerism in cases undetectable by the latter method.

Minimal residual disease status in pre-B acute lymphoblastic leukemia patients after chemotherapy and bone marrow transplantation: assessment of the anti-leukemic effects of chemotherapy and BMT

We prospectively analyzed minimal residual disease (MRD) in four patients with B-cell precursor acute lymphoblastic leukemia who had been in complete remission for more than one year after chemotherapy and allogenic or autologous bone marrow transplantation (BMT). MRD was quantitatively estimated using polymerase chain reaction amplification to detect the complementarity-determining region III of the immunoglobulin heavy chain gene at limiting dilution DNA samples. Our study showed that remission induction chemotherapy reduced at most 2-logs of leukemia cells, and that subsequent consolidation chemotherapy induced further reduction of leukemia cells. In two cases, 10(-5) levels of MRD were detected two months after BMT. However, no MRD was detected four months after BMT. We also showed the effectiveness of ex vivo purging with anti-CALLA monoclonal antibodies which eliminated at least 2-logs of leukemia cells in autologous BMT. Our results suggest that this detection system is useful for assessing the reduction of the original leukemia clone, and that the presence of MRD within three months after BMT is not related to clinical outcome.

Comparative clinical evaluation of biochemical and genomic tumor markers

The clinical utilities of established biochemical tumor markers and of emerging genomic markers are compared by six formal criteria: [1] tests negative in health or benign disease, [2] produced exclusively by specific tumor cells, [3] present frequently in the targeted malignancy, [4] detectable in occult disease, [5] degree of expression reflects tumor burden and prognosis, and [6] degree of expression correlates with therapeutic result. Evaluation of eight widely accepted marker systems combining a biochemical indicator with a specific cancer, on the one hand, and five representative genomic marker-target combinations involving chromosomal translocation, gene amplification and mutation, on the other hand, produces three main conclusions: First, specified applications are sufficiently well documented for the best biochemical markers to now tailor analytical performance goals to these uses. Second, further clinical trials of genomic markers are needed to document the useful linkage of specific indicators with specific clinical problems. Third, the different profiles of marker characteristics defining the two classes of indicators suggest some mutually complementary uses.

Quantitation of follicular non-Hodgkin's lymphoma cells carrying t(14;18) by competitive polymerase chain reaction

A competitive polymerase chain reaction (PCR) technique was developed to quantify residual malignant cells in the peripheral blood and bone marrow of patients with low-grade follicular non-Hodgkin's lymphoma carrying a translocation between chromosomes 14 and 18. Artificial segments were constructed imitating a translocation between chromosome 14 and 18. These artificial translocation segments were used as competitor molecules in the quantitative PCR. Serial dilutions of a known amount of patient-derived translocation segments were coamplified with a fixed number of competitor molecules, and a patient specific calibration curve was constructed. Several patient samples were coamplified with an equal number of competitor molecules and the number of t(14;18) translocations within the samples was calculated by comparison with the calibration curve. The method was demonstrated on samples of four follicular non-Hodgkin's lymphoma (NHL) patients. In a patient transplanted with allogeneic bone marrow declining numbers of residual lymphoma cells were observed. We conclude that the method is accurate, relatively fast and the general principle of this method can be applied to all malignancies with characteristic abnormalities on DNA or RNA level that are detectable by PCR.

Lymphoblast colony-culture assay in acute lymphoblastic leukemia: a quantitative approach

Lymphoblast colony-culture of adult acute lymphoblastic leukemia (ALL) was studied to explore its clinical implication. Among 13 marrow cultures from ALL patients with full-blown disease, 11 developed leukemic colonies. A type of colony, very similar to a lymphoblastic colony and possibly T-cell in origin, could be found in four cultures of the six control marrows. To minimize the difficulty in differentiating a leukemic blast colony and a normal lymphocyte colony, based solely on morphology, a quantitative approach was used. Since both the mean of blast colony count and the mean of blast percentage of leukemic marrow were significantly higher than those of the control group, mean value plus two standard deviations of the control group were defined arbitrarily as upper normal limits. The defined normal range was then used to examine the relationship between results of the cultures and clinical outcome for the ALL patients. Early relapse or incomplete remission following chemotherapy could be predicted in four patients by these quantitative colony-culture assays 0.5-2 months before full-blown disease. The low colony count and low blast percentage in the colony-culture assay of the fifth patient is compatible with the clinical observation of continuous remission. One culture, growing clusters only, had an increased blast percentage; this correlated well with cytogenetic relapse two months later. In summary, the quantitative colony-culture assay could detect morphologically unidentifiable leukemic cells in ALL patients with early relapse or incomplete remission. This quantitative colony-culture system, though not ultrasensitive in the detection of minimal residual leukemic cells, was of potential value as a prognostic assay.

Peripheral blood stem cell transplantations: past, present and future

Since the first successful attempt in 1985, peripheral blood stem cell transplants are increasingly performed worldwide and should now be considered as an essential therapeutic weapon against onco-hematological diseases. Their development has benefited greatly from a rapid concomitant advance of experimental knowledge regarding the nature of hematopoietic progenitor cells. For this reason and also for technical ones, until now these transplants generally have been autotransplants. Although one of the main reasons to use blood rather than bone marrow-derived stem cells was that they might carry less risk of relapse than autologous bone marrow cells, the lack of clinical randomized trials and/or the short follow-up make conclusions difficult so far in terms of disease-free and overall survival. Probably the risk of relapse also depends on the type of disease, on prior chemotherapies, on the type of peripheral stem cell mobilization regimen and on the number of blood-derived cells transplanted. Nevertheless, there are several major clinical indications for autologous blood stem cell transplant: acute nonlymphoblastic leukemias (ANLL), low-grade non-Hodgkin's lymphomas, multiple myeloma, some solid tumors, and even chronic myeloid leukemia. Now well-demonstrated advantages add a socioeconomic interest to this technique. The speed of post-transplant hematopoietic recovery induces a briefer hospitalization and a lower cost of the procedure, which represents "per se" important progress. Furthermore, the increasing use of hematopoietic growth factor(s) at time of blood-derived cell mobilization should increase the safety of the procedure. Also new trends are currently being developed: autotransplants with purified peripheral CD34+ cells; addition of adjuvant immunotherapy to induce graft-versus-tumor effect, which is lacking in autotransplant; and transplants using allogenic umbilical cord blood progenitors. Allogenic blood cell transplants might also be developed, provided that blood cells would be less likely to cause graft-versus-host disease (GVHD) than bone marrow, which is still not verified. Finally, the use of blood-derived cells as a vehicle for gene therapy should develop greatly in the near future.

Detection of bcl-2/JH rearrangement in follicular and diffuse lymphoma: concordant results of peripheral blood and bone marrow analysis at diagnosis

The capacity to detect t(14;18) breakpoints in non-Hodgkin's lymphoma (NHL) peripheral blood and bone marrow was studied by DNA PCR. We studied 33 patients with follicular lymphoma (FL) (Working Formulation subtypes B, C, D) and 38 patients with intermediate-grade NHL (subtypes F, G). In the FL subgroup, 86% of the morphologically-positive bone marrow patients had amplifiable t(14;18) breakpoints by PCR. Remarkably, of 19 FL patients with 'negative' bone marrows, 11 (58%) were PCR-positive. In addition, half of the early clinical stage patients (I and II) had detectable breakpoints in their bone marrow DNA. Samples from NHL patients with intermediate-grade disease exhibit the same phenomena but at a considerably lower frequency. Paired peripheral blood and bone marrow samples were available at diagnosis in a subset of 56 patients. The concordance between bone marrow and peripheral blood PCR findings was high, with peripheral blood of 55/56 showing the same PCR results as the corresponding bone marrow.

Detection of BCR/ABL transcripts in chronic myeloid leukaemia by polymerase chain reaction and DNA enzyme immunoassay: a DNA probe assay without DNA labelling

The detection of the t(9;22) translocation, typical of chronic myeloid leukaemia (CML), can be accomplished by cytogenetical detection of Philadelphia (Ph1) chromosome or by molecular analysis of the bcr/abl fusion gene with nucleic acid probes after amplification by polymerase chain reaction (PCR). PCR-based approaches are now widely used for follow up of CML patients during therapy or after bone marrow transplantation (BMT). We describe here a microtitre, colorimetric assay (DNA Enzyme Immunoassay, DEIA) for analysis of t(9;22) translocation after enzymatical amplification of RNA from CML patients. This assay is based on the use of a monoclonal antibody specifically reacting with double stranded DNA, i.e. with hybridized DNA. The assay represents a nonisotopic alternative to other current hybridization assays and requires no modifications of primers, probe or target DNA.

Bone marrow purging for autologous bone marrow transplantation

High dose therapy with the resulting myeloablation rescued by infusion of autologous bone marrow (ABMT) has become a major treatment option for an increasing number of patients with hematologic and solid tumors. ABMT has several potential advantages over allogeneic transplantation. However, the major obstacle to the use of ABMT is that the infusion of occult tumor cells harbored within the harvested marrow would result in more rapid relapse of disease. To minimize the effects of the infusion of significant numbers of malignant cells, marrow for ABMT is obtained when the patient is either in complete remission or when there is no histologic evidence of bone marrow infiltration of disease. There is increasing evidence that minimal numbers of malignant cells can be detected within the remission marrow of these patients, particularly when assessed by sensitive clonogenic assays or polymerase chain reaction amplification. A variety of methods, pharmacologic and immunologic have been developed to "purge" malignant cells from the marrow. The aim of purging is to eliminate any contaminating malignant cells and leave intact the hematopoietic stem cells that are necessary for engraftment. Although the rationale for removing any contaminating cells from the autologous marrow appears compelling, the issue of purging remains highly controversial. Intense argument persists as to whether attempts to remove residual tumor cells from the harvested bone marrow have contributed to improving disease-free survival in these patients. To date there have been no clinical trials testing the efficacy of purging by comparison of infusion of purged versus unpurged autologous bone marrow. This is due primarily to the large number of patients that would be required for such studies.

Polymerase chain reaction facilitates archival autopsy studies of sickle cell disease

Archival autopsy studies of sickle cell disease have often been hampered by inadequate documentation of the genotype. Although the polymerase chain reaction (PCR) has been applied to the prenatal diagnosis of sickle cell disease, its use has not been reported in archival studies of sickle cell disease. In this study, DNAs from formalin-fixed, paraffin-embedded archival tissues were amplified by PCR and analyzed by dot-blot hybridization using allele-specific oligonucleotides. These S and C genotypes for 9 of 10 archival specimens studied blindly were correctly identified by PCR. The tenth specimen consistently failed to amplify by PCR, yielding no result. These data demonstrate the utility of PCR for retrospective identification of the genotype of sickle cell disease. This application of PCR will significantly expand the number of autopsy cases suitable for retrospective studies of the morbidity and mortality of sickle cell disease.

Chromosomal approaches to hematopoietic oncogenesis

Cytogenetic studies have provided an important approach to the identification of genes involved in the development of human leukemias and lymphomas and the "mutational" mechanisms leading to the altered function of these genes. Molecular dissection of chromosome translocations, in both lymphoid and myeloid tumors, has been particularly productive. Involvement of the c-myc gene has been demonstrated in both B cell and T cell tumors through association with an immunoglobulin or T cell receptor locus, respectively, and more than a dozen previously unknown "oncogenes" have been identified in other lymphoid tumor subgroups and are "activated" by a similar mechanism or by formation of a "fusion" gene with a locus on a different chromosome. In myeloid tumors, dissection of the translocation in Philadelphia chromosome positive leukemias has demonstrated involvement of the abl oncogene; other genes, both known and previously unknown, are beginning to be identified in translocations that characterize other classes of myeloid leukemia. These kinds of studies are being extended to search for tumor suppressor genes in association with chromosomal deletions, and some of the new molecular data are already being usefully applied in clinical diagnosis and management. Ultimately, there may also be specific therapies developed from these recent findings, but the recognition of how many different genes are involved has also indicated that no single, simple answer will be forthcoming.

The use of reverse transcriptase-polymerase chain reaction (RT-PCR) to investigate specific gene expression in multidrug-resistant cells

Expression of specific genes at the level of mRNA can be studied using techniques such as Northern blot, slot/dot blot, RNase protection assay, in situ hybridisation and RT-PCR. In this article these methods of analysis are compared; RT-PCR offers higher levels of specificity and sensitivity than traditional methods of RNA analysis and as such has become the method of choice for the study of gene expression. The RT-PCR technique is described in detail with sections dealing with RNA extraction, choice of primers (including the use of cDNA sequence data bases), PCR and RT-PCR protocols in addition to the limitations of the method. The study of one particular mRNA transcript (MDR1) using RT-PCR is discussed in detail. Recently described methods for quantitation of PCR products are discussed. Quantitative PCR would appear to offer a method of studying gene expression in a more extensive way than has been possible to date.

Clonal Ig-gene rearrangement in some cases of gastric RLH detected by PCR method

Clonal immunoglobulin (Ig) heavy chain gene rearrangement in gastric reactive lymphoid hyperplasia (RLH) cases was investigated by means of the 'double' polymerase chain reaction (PCR) using formalin-fixed and paraffin-embedded tissue. Rearranged DNA sequences, formed by combinations of variable (VH) and joining (JH) regions, were amplified with oligomeric primers. One microgram of DNA extracted from formalin-fixed and paraffin-embedded tissue was applied as the 'first PCR' template and one ten-thousandth of the first PCR product was used as the 'second PCR' template. As a control study for the double PCR method, DNA isolated from frank B cell gastric malignant lymphomas was assessed. Clear single bands between 100 and 150 base pair markers in length were evident on agarose gel electrophoresis in 10 out of 13 cases (76.9%) of malignant lymphomas while 2 out of 22 cases (9%) of RLHs revealed clear single bands of the same length, suggesting malignant lymphomas; however, no histologic features of malignant lymphomas were present. It is concluded that even gastric RLH cases satisfying histopathologic criteria for benign lymphoid hyperplasia may contain occult monoclonal B cell populations suggesting a continuous and progressive spectrum of lesions contributing to B cell neoplasia.

The detection of specific gene rearrangements in non-Hodgkin's lymphoma using the polymerase chain reaction

Characteristic gene rearrangements are present in most non-Hodgkin's lymphomas (NHL). These are usually detected by Southern blotting techniques. In this study, the ability of the polymerase chain reaction (PCR) to detect the t(14;18) chromosomal translocation and immunoglobulin heavy chain (IgH) gene rearrangement was evaluated. DNA from 14 follicular and 42 diffuse B-cell lymphomas was examined using oligonucleotide primers specific for opposing sides of the IgH gene rearrangement on chromosome 14 (towards conserved VH and JH sequences) and opposing sides of the t(14;18) chromosomal translocation (towards the major breakpoint region of the bcl-2 gene on chromosome 18 and conserved JH sequence on chromosome 14). The t(14;18) translocation was detected in 57% of follicular lymphomas and 21% of diffuse B-cell lymphomas. Clonal IgH gene rearrangements using PCR were detected in 50% follicular and 52% of the diffuse lymphomas. Either or both of these rearrangements were detected in 93% follicular and in 59% of diffuse lymphomas. PCR is a rapid and easy technique that can detect the abnormal rearrangement of the bcl-2 gene and clonal IgH rearrangement, indicating the presence of lymphoma. This may be of benefit in monitoring response to therapy and in predicting prognosis in this disease.

Expression of the bcl-2 oncogene product and chromosomal translocation t(14;18) in Hodgkin's disease

The B-cell lymphoma/leukemia oncogene bcl-2 takes part in crucial regulatory events in B-cell maturation and differentiation. The reciprocal chromosomal translocation t(14;18), leading to overexpression of this oncogene, can be found in the majority of follicular lymphomas and much less frequently in B-cell leukemias and diffuse lymphomas. We have studied the expression of this protein in different subtypes of Hodgkin's disease using monoclonal antibodies directed against a formalin-resistant epitope of the bcl-2 protein and also have investigated these cases by polymerase chain reaction for evidence of the t(14;18) translocation. We were particularly interested to determine whether nodular paragranuloma (lymphocyte-predominant, nodular), which differs from other subtypes of Hodgkin's disease by virtue of the B-cell nature of its malignant cell population, is characterized by expression of the bcl-2 protein. Our data indicate that only a small number of nodular paragranulomas express the bcl-2 protein and that the expression is not specific for this type of Hodgkin's disease. In a smaller number of cases this expression of bcl-2 could be explained by the presence of the translocation t(14;18).