Persistence of myeloid progenitor cells expressing BCR-ABL mRNA after allogeneic bone marrow transplantation for chronic myelogenous leukemia

Previous studies have shown that tumor-specific bcr-abl mRNA can often be detected by polymerase chain reaction. (PCR) for months to years after allogeneic bone marrow transplantation (BMT) for chronic myelocytic leukemia (CML). Nevertheless, the presence of bcr-abl mRNA by itself does not invariably predict for clinical relapse post-BMT. This has led to the hypothesis that bcr-abl mRNA might be expressed in cells that have lost either proliferative or myeloid differentiation potential. To directly characterize the cells detected by PCR in patients with CML after allogeneic BMT, we first identified five individuals in whom PCR-positive cells could be detected at multiple times post-BMT. Bone marrow samples from these individuals were cultured in vitro and single erythroid, granulocytic, and macrophage colonies, each containing 50 to 100 cells, were examined for the presence of bcr-abl mRNA by PCR. PCR-positive myeloid colonies could be detected in four of five individuals in marrow samples obtained 5 to 56 months post-BMT. Overall, 7 of 135 progenitor cell colonies (5.2%) were found to be PCR-positive. The expression of bcr-abl mRNA appeared to be equally distributed among committed erythroid, macrophage, and granulocyte progenitors. These patients have now been followed-up for an additional 20 to 33 months from the time of progenitor cell PCR analysis but only one of these individuals has been found to have cytogenetic evidence of recurrent Ph+ cells. These results show that long-term persistence of PCR-detectable bcr-abl mRNA after allogeneic BMT can be caused by the persistence of CML-derived clonogenic myeloid precursors that have survived the BMT preparative regimen. These cells continue to have both proliferative and myeloid differentiation capacity in vitro. Nevertheless, these PCR-positive cells do not appear to either expand or differentiate in vivo for prolonged periods, suggesting the presence of mechanisms for suppression of residual clonogenic leukemia cells in vivo.     

Detection of residual leukemia after bone marrow transplant for chronic myeloid leukemia: role of polymerase chain reaction in predicting relapse

We used the polymerase chain reaction (PCR) to detect residual leukemia-specific mRNA in blood and marrow from 37 patients in complete hematologic and cytogenetic remission after allogeneic bone marrow transplant (BMT) for chronic myeloid leukemia (CML). Our two-step PCR method involved the use of "nested primers" in the second step and could detect one K562 cell diluted into 10(5) normal cells. Elaborate measures were taken to exclude false-positive and false-negative results. In nine patients whose blood and marrow were studied simultaneously the results were concordant (two positive and seven negative). Twenty-three patients transplanted in chronic phase (CP) with unmanipulated donor marrow were studied. Blood cells from nine of these patients were studied 3 to 6 months post-BMT and six were PCR positive; three were negative on subsequent studies. Blood cells from 18 patients studied between 8 months and 8 years post-BMT were all PCR negative. Nine patients transplanted in CP with T-cell-depleted marrow cells were studied. Blood from five was positive 3 to 24 months post-BMT; blood from five was negative 3 to 6 years post-BMT. Four patients no longer in first CP were studied after BMT with unmanipulated donor marrow. Blood from all four was positive 5 to 19 months post-BMT. Based on the known clinical results of transplant in these three cohorts we conclude that PCR may be positive within 6 months of BMT in patients who can expect long-lasting remission, whereas PCR positivity later after BMT may indicate that the probability of cure is reduced. Thus, the technique may prove useful for early assessment of new transplant protocols that might inadvertently increase the risk of relapse.     

Molecular quantification of residual disease in chronic myelogenous leukemia after bone marrow transplantation.

Residual disease remains a major problem in the treatment of human neoplasia. To effectively monitor minimal leukemic activity after bone marrow transplantation (BMT), we used a competitive polymerase chain reaction (PCR) amplification technique to quantify expression of the characteristic bcr-abl fusion message in patients with chronic myelogenous leukemia (CML). Quantitative results were obtained between the 0.001% and 0.1% level in control experiments. This represents a significant advantage over cytogenetic and Southern blotting techniques routinely used to diagnose CML, which may not be sensitive below the 1% level. To illustrate the potential clinical usefulness of the quantitative PCR strategy, we compared results of bcr-abl messenger RNA expression with those obtained using cytogenetic and Southern blotting techniques, in a study of consecutive BM and peripheral blood (PB) samples from two CML patients at high risk for relapse after BMT. One patient received a syngeneic transplant during the chronic phase of the disease and relapse was apparent at the molecular level 4.5 months after BMT, while the patient was in complete clinical remission. The second patient was treated with an allogeneic BMT during the accelerated phase of the disease. A slow, but progressive decrease in bcr-abl expression was observed during the first 12 months after BMT, and expression was undetectable thereafter. Our results indicate that the competitive PCR technique can be used to monitor disease activity in patients at high risk of relapse, while the patients are in complete clinical remission, which should facilitate the early detection of relapse or the identification of progressive disappearance of leukemic activity. The approach used may serve as a model for the study of residual disease in an increasing number of other hematologic malignancies that express cancer-specific RNAs.     

Myeloid mixed chimerism is associated with relapse in bcr-abl positive patients after unmanipulated allogeneic bone marrow transplantation for chronic myelogenous leukemia

BACKGROUND AND OBJECTIVE: Although bcr-abl polymerase chain reaction (PCR) positivity after bone marrow transplantation (BMT) for chronic myelogenous leukemia (CML) is significantly related to relapse, the predictive value of the assay is not very high and therefore most investigators consider that qualitative RT-PCR data alone are too imprecise to enable clinical decisions to be taken in individual cases. To define the clinical outcome of bcr-abl positive patients after unmanipulated BMT better, we sought the origin of hematopoiesis and traced its evolution over time. DESIGN AND METHODS: Forty-nine patients received allogeneic BMT for CML (39 in chronic phase and 10 in accelerated phase/blast crisis). Median follow-up was 61 months (range 4-92). mRNA and DNA were used to assess bcr-abl and chimerism status respectively. Quantitative VNTR-PCR on total cells and lymphoid or myeloid population allowed us to assign and measure the origin of hematopoiesis. RESULTS: Both bcr-abl positivity and the presence of mixed chimerism (MC) were significantly associated with relapse (p = 0.0009 and p < 0.0001 respectively). Relapse was observed in one of 39 patients with complete donor chimerism and in 6 of 9 patients with MC. These six cases showed increasing levels of host hemopoiesis and bcr-abl positivity in the CD15-positive population prior to relapse. The other three cases had decreasing or stable low-level MC which was restricted to the T-cells as well as bcr-abl negativity. INTERPRETATION AND CONCLUSIONS: Whereas the simple detection of bcr-abl fails to identify patients who will relapse with certainty, the assessment of MC by VNTR-PCR does identify patients headed to relapse. Confirmation of myeloid involvement and increasing levels over time further elucidates the clinical outcome of bcr-abl positive patients after BMT.     

Allogeneic cell therapy with donor peripheral blood cells and recombinant human interleukin-2 to treat leukemia relapse after allogeneic bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) is the only effective treatment for hematologic malignancies resistant to conventional chemotherapy. Until recently, no cure existed for patients who relapsed post-BMT. We present our long-term observations on remission induction, after relapse post-BMT, by allogeneic cell therapy (allo-CT) and the feasibility of remission induction in allo-CT-resistant patients by activation of antileukemia effector cells with recombinant human interleukin-2 (rhIL-2) in vitro and in vivo. The longest observation of successful allo-CT (event-free survival, greater than 8 years) was made in a patient with resistant pre-B lymphoblastic leukemia who received infusions with graded increments of donor (female) peripheral blood lymphocytes (PBL) as soon as bulky hematologic and extramedullary relapse was noticed early post-BMT. The patient is currently without evidence of residual host (male) cells as determined by polymerase chain reaction (PCR). Of 17 patients with acute and chronic leukemia in relapse after BMT, 10 were reinduced into complete remission. Four patients with cytogenetic relapse responded to allo-CT alone, while five of six patients with overt hematologic relapse responded only after additional activation of donor with rhIL-2. Allo-CT can, therefore, successfully reverse chemoradiotherapy-resistant relapse of both acute and chronic leukemia. Moreover, in patients resistant to donor lymphocyte infusion, remission can be accomplished by additionally activating donor PBL in vitro and/or in vivo with rhIL-2. Based on our observations, after BMT, allo-CT should be considered the treatment of choice for patients with hematologic malignancies resistant to conventional anticancer modalities. Allogeneic activated cell therapy (allo ACT) should be considered for patients with tumor cells resistant to allo-CT. Although allo-CT, followed if indicated by allo-ACT, can be effective for patients with overt hematologic relapse, reversal of persistent minimal residual disease or documented molecular/cytogenetic relapse early after BMT may also be considered as a possible indication for allo-CT.     

Minimal residual disease is more common in patients who have mixed T- cell chimerism after bone marrow transplantation for chronic myelogenous leukemia

Determining both lymphoid chimerism and the presence of minimal residual disease after allogeneic bone marrow transplantation (BMT) for chronic myelogenous leukemia (CML) could be helpful to the understanding of the biology of leukemic relapse in this disease. We prospectively investigated 32 patients with CML post-BMT by assessing T- cell chimerism and minimal residual disease using sensitive polymerase chain reaction (PCR) methodologies. Patients were studied between 1 and 24 months post-BMT. Thirty patients received a T-cell-depleted marrow grafts and 2 received unmanipulated marrow. All but 1 patient were conditioned with total body irradiation (TBI)+thiotepa+cyclophosphamide (Cy). The other patient received TBI+Cy as conditioning. The T cells were exclusively of donor origin in 12 of 16 patients who were tested at 1 month post-BMT, but were mixed chimeric in 11 of these patients by > or = 3 months. Once mixed T-cell chimerism was documented, no patient returned to having all donor T-cells. At a median follow-up of 12 months, minimal residual disease was present in 18 of 22 patients with mixed T-cell chimerism and in 3 of 10 patients with full donor chimerism. The actuarial molecular relapse rate at 24 months for the two groups is 91% and 33%, respectively (P < .02). The finding of BCR- ABL mRNA within the first 6 months of transplant or on two consecutive assays was highly predictive of subsequent cytogenetic or hematologic relapse (P = .032 and P < .02, respectively). Ten patients, 9 with mixed T-cell chimerism, have relapsed (4 clinical, 6 cytogenetic) at a median of 12 months post-BMT. These data suggest that mixed T-cell chimerism may be a marker for abrogation of graft-versus-leukemia activity that is thought to be pivotal in eradicating minimal residual disease after BMT for CML.     

Cytogenetic analysis of chimerism and leukemia relapse in chronic myelogenous leukemia patients after T cell-depleted bone marrow transplantation

Serial cytogenetic studies were performed on 64 patients with chronic myelogenous leukemia (CML) after T cell-depleted allogeneic bone marrow transplantation (BMT). Forty patients with CML in chronic phase (CP) received cytoreduction followed by BMT with HLA-matched T cell-depleted allogeneic marrow. The remaining 24 patients were transplanted in second chronic, accelerated, or blastic phase, or received T cell-depleted grafts with a dose of T cells added back. The Y chromosome and autosomal heteromorphisms were used to distinguish between donor and host cells. Mixed hematopoietic chimerism (presence of donor and host cells) was identified in 90% of patients in first CP. The Philadelphia (Ph) chromosome reappeared in 16 of the 40 first CP CML patients. As expected, patients who had detectable Ph chromosome positive cells at any time during the posttransplant period had a high likelihood of subsequent clinical relapse. Transient disappearance of the Ph positive clone was rarely observed, and was followed by reappearance of the Ph chromosome or clinical relapse. A subset of engrafted patients with greater than 25% host cells within 3 months post-BMT had a significantly shorter survival time free of cytogenetic or clinical relapse compared with other patients. In patients who had received donor T cells added to the T cell-depleted graft, there was a higher proportion of complete chimerism. Clonal progression of Ph positive as well as negative cells was observed and may be the result of radiation induced breakage. Serial cytogenetic studies of patients post-BMT can provide useful information regarding the biologic and clinical behavior of CML.     

Prognostic significance of genetic markers in chronic myelogenous leukemia patients after bone marrow transplantation

Chronic myelogenous leukemia (CML) is a malignant disease of hematopoietic stem cell with a biphasic or triphasic clinical course and most often, with a fatal outcome. Significant progress in improving outcome for patients with CML has been achieved over past years. This can be attributed to marked improvement in therapeutic protocols and increased use of bone marrow transplantation (BMT) which remains the most effective option for long-term disease control of patient with CML. The residual leukemic activity in patients after BMT remains a central clinical question. To effectively monitor minimal residual disease leukemic activity after BMT, molecular genetic techniques are currently utilized in conjunction with cytogenetic assays. Because the clinical significance of detection minimal residual disease in CML remains to be determined, we performed cytogenetic analysis and PCR amplification technique in 37 Ph+ CML patients. All patients received transplants for CML in Bratislava between years 1992 and 1999. Our results suggest that PCR positivity after transplant is of limited prognostic significance for particular individuals and can be used to identified groups of individuals at elevated risk of relapse.     

Evaluation of remission state in chronic myeloid leukemia patients after bone marrow transplantation using cytogenetic and molecular genetic approaches

The remission state of 13 Philadelphia positive chronic myeloid leukemia patients was studied after bone marrow transplantation (BMT) by cytogenetic and Southern blot analysis of the breakpoint cluster region (BCR) gene. Eight of 13 patients showed neither clinical nor genetic evidence of residual disease. In two patients hematological relapse was confirmed by cytogenetic and molecular analysis. Evidence for residual leukemic cells in otherwise complete remission was obtained genetically in three patients. One of the latter cases revealed BCR rearrangement despite negative cytogenetic findings, while in another patient cytogenetic relapse was observed without demonstrable rearrangement within the major BCR. Our results may indicate that cytogenetic and molecular genetic methods complement rather than replace each other for the detection of residual CML cells after BMT.     

CD8-depleted donor lymphocyte infusion as treatment for relapsed chronic myelogenous leukemia after allogeneic bone marrow transplantation

Donor lymphocyte infusions can reinduce complete remission in the majority of patients with chronic myelogenous leukemia (CML) who relapse into chronic phase after allogeneic bone marrow transplantation (BMT). Such infusions are associated with a high incidence of graft- versus-host disease (GVHD) and marrow aplasia. BMT using selective depletion of CD8+ lymphocytes from donor cells reduces the incidence of GVHD without an increase in leukemia relapse. We hypothesized that infusion of CD8-depleted donor peripheral blood lymphocytes could also reinduce complete remissions with a lesser potential to produce symptomatic GVHD in patients with CML who relapsed after allogeneic BMT. Ten patients with Ph(+) CML who relapsed a median of 353 days after BMT (range, 82 to 1,096 days) received donor lymphocyte infusions depleted of CD8+ cells. Nine patients received a single infusion and 1 received two infusions. Four patients were treated while in chronic phase with clonal evolution, 2 during accelerated phase, 3 during blast crisis, and 1 in a cytogenetic relapse. A mean of 0.9 +/- 0.3 x 10(8) mononuclear cells/kg were infused, containing 0.6 +/- 0.4 x 10(6) CD3+CD8+ cells/kg. Six patients achieved hematologic and cytogenetic remission at 4, 8, 11, 15, 39, and 54 weeks after lymphocyte infusion. Two patients developed > or = grade II acute GVHD, and 1 patient developed mild chronic GVHD. We conclude that donor lymphocyte infusions depleted of CD8+ cells can induce remissions with a low rate of severe acute GVHD in patients with CML who relapse after allogeneic BMT, supporting the hypothesis that CD8+ lymphocytes are important effectors of GVHD, but may not be essential for the graft-versus- leukemia effect against this disease. Further controlled studies are required to confirm these preliminary observations.     

Biological importance of residual leukaemic cells after BMT for CML: does the polymerase chain reaction help?

The fate of the leukaemic clone after bone marrow transplantation (BMT) for patients with chronic myeloid leukaemia (CML) may determine the long-term prognosis. Several groups have reported the use of the polymerase chain reaction (PCR), a highly sensitive technique for detecting residual leukaemia, to study blood and bone marrow of patients in apparent cytogenetic and clinical remission at various intervals after BMT. The limitations of the technique relate to the need in CML to use mRNA rather than DNA as test material, the undefined sensitivity of the assay, the lack of knowledge of cell lineage when the test is positive and the high risk with present techniques of false positive and false negative findings. These points notwithstanding, the collected data suggest that most longterm survivors have no evidence of leukaemia detectable by PCR; in contrast many of the patients transplanted within the last 5 years do have evidence of residual leukaemia. This suggests that in a significant number of patients the leukaemic clone may survive for several years after BMT before it is eradicated (or falls below the threshold for detection by PCR). If this is confirmed the finding of residual leukaemia by PCR in the first few years post-BMT would have limited prognostic significance.     

Apparent decrease and elimination of BCR/ABL mRNA-expressing residual cells in patients with chronic myelogenous leukemia after allogeneic bone marrow transplantation

Summary A modified two-step polymerase chain reaction (PCR) was used for the amplification of BCR/ABL mRNA in 16 patients with Philadelphia chromosomepositive (Ph+) chronic myelogenous leukemia (CML) following allogeneic bone marrow transplantation (BMT). At different intervals after BMT, patient cells were assessed for the presence of BCR/ABL mRNA by two subsequent rounds of PCR amplification; this procedure increased the sensitivity for the detection of one Ph+ cell in 10^4–5 to one cell in 10^5–6. Eight of 16 patients were negative by two-step PCR 1–39 months after BMT, suggesting an elimination of Ph-positive cells or a decrease below the threshold of detection. Although five patients showed negative results by the one-step PCR only, they were tested positive when nested primers were used, indicating a substantial decrease in the amount of BCR/ABL target mRNA compared with earlier pre- or post-transplant analyses. One patient who was still PCR positive 27 months after BMT became negative 12 months later. Persistence of BCR/ABL mRNA-expressing cells correlated with subsequent clinical relapse only when the transplantation was performed during blast crisis. All patients who underwent transplantation in chronic phase, including those with BCR rearrangement by PCR, are in clinical and hematological remission between 24 and 95 months after BMT. We conclude that aggressive chemotherapy combined with total body irradiation is unable to completely eradicate the malignant clone in all CML patients, and it might be speculated that other mechanisms (e.g., graft versus host reaction [GVHD] or graft versus leukemia effect [GVL]) may effectively eliminate residual leukemic cells.The studies were supported by grant Do 176/5-1 from theDeutsche Forschungsgemeinschaft