Relevance and dynamics of myelofibrosis regarding hematopoietic reconstitution after allogeneic bone marrow transplantation in chronic myelogenous leukemia--a single center experience on 160 patients

Myelofibrosis at diagnosis is associated with the failure of treatment-free remission in CML patients

The management of patients with chronic myeloid leukemia (CML) has been revolutionized by the introduction of tyrosine kinase inhibitors (TKIs), which induce deep molecular responses so that treatment can eventually be discontinued, leading to treatment-free remission (TFR) in a subset of patients. Unfortunately, leukemic stem cells (LSCs) often persist and a fraction of these can again expand in about half of patients that attempt TKI discontinuation. In this study, we show that presence of myelofibrosis (MF) at the time of diagnosis is a factor associating with TFR failure. Fibrotic transformation is governed by the action of several cytokines, and interestingly, some of them have also been described to support LSC persistence. At the cellular level, these could be produced by both malignant cells and by components of the bone marrow (BM) niche, including megakaryocytes (MKs) and mesenchymal stromal cells (MSCs). In our cohort of 57 patients, around 40% presented with MF at diagnosis and the number of blasts in the peripheral blood and BM was significantly elevated in patients with higher grade of MF. Employing a CML transgenic mouse model, we could observe higher levels of alpha-smooth muscle actin (α-SMA) in the BM when compared to control mice. Short-term treatment with the TKI nilotinib, efficiently reduced spleen weight and BCR::ABL1 mRNA levels, while α-SMA expression was only partially reduced. Interestingly, the number of MKs was increased in the spleen of CML mice and elevated in both BM and spleen upon nilotinib treatment. Analysis of human CML-vs healthy donor (HD)-derived MSCs showed an altered expression of gene signatures reflecting fibrosis as well as hematopoietic support, thus suggesting MSCs as a potential player in these two processes. Finally, in our cohort, 12 patients qualified for TKI discontinuation, and here we observed that all patients who failed TFR had BM fibrosis at diagnosis, whereas this was only the case in 25% of patients with achieved TFR, further supporting the link between fibrosis and LSC persistence.

Stromal SPARC contributes to the detrimental fibrotic changes associated with myeloproliferation whereas its deficiency favors myeloid cell expansion

In myeloid malignancies, the neoplastic clone outgrows normal hematopoietic cells toward BM failure. This event is also sustained by detrimental stromal changes, such as BM fibrosis and osteosclerosis, whose occurrence is harbinger of a dismal prognosis. We show that the matricellular protein SPARC contributes to the BM stromal response to myeloproliferation. The degree of SPARC expression in BM stromal elements, including CD146+ mesenchymal stromal cells, correlates with the degree of stromal changes, and the severity of BM failure characterizing the prototypical myeloproliferative neoplasm primary myelofibrosis. Using Sparc−/− mice and BM chimeras, we demonstrate that SPARC contributes to the development of significant stromal fibrosis in a model of thrombopoietin-induced myelofibrosis. We found that SPARC deficiency in the radioresistant BM stroma compartment impairs myelofibrosis but, at the same time, associates with an enhanced reactive myeloproliferative response to thrombopoietin. The link betwen SPARC stromal deficiency and enhanced myeloid cell expansion under a myeloproliferative spur is also supported by the myeloproliferative phenotype resulting from the transplantation of defective Apcmin mutant hematopoietic cells into Sparc−/− but not WT recipient BM stroma. Our results highlight a complex influence of SPARC over the stromal and hematopoietic BM response in myeloproliferative conditions.

The impact of bone marrow fibrosis on the outcome of hematopoietic stem cell transplantation

We retrospectively analyzed the data of 175 patients who underwent autologous (n = 69) or allogeneic hematopoietic stem cell transplantation (HCT) (n = 106) including 19 (27.5%) and 38 (35.8%) recipients who had bone marrow fibrosis (BMF) prior to transplantation, respectively. We investigated the effects of BMF on engraftment, graft-versus-host disease (GVHD), early posttransplant complications, and survival. Pretransplantation BMF did not delay engraftment and showed no impact either on early posttransplant complications or on the development of acute and/or chronic GVHD. Probability of 1-year overall survival (OS) and progression-free survival (PFS) of autologous HCT recipients were similar, namely 76.7% versus 88.6% (P > .005) and 26.33% versus 16.5% (P > .05) among patients with versus without fibrosis, respectively. In allogeneic HCT recipients, the probability of 1-year OS was 35.2% among patients with versus 48.9% among those without fibrosis (P = .004) PFS at 1 year was inferior among allogeneic HCT recipients with BMF: 27.8% versus 51.2% (P = .0008). Cox regression analysis revealed BMF to be independently associated with age, Sorror comorbidity index, primary disease, and disease status during HCT (P = .045).

Morphologic examination of sequential bone marrow biopsies after nonmyeloablative stem cell transplantation complements molecular studies of donor engraftment

CONTEXT

Nonmyeloablative stem cell transplantation (NMSCT) is a mode of immunotherapy increasingly employed in treating hematologic, lymphoid, and solid tumors. Patients are monitored principally by molecular analysis of donor engraftment.

OBJECTIVE

To determine the role of morphologic examination of bone marrow after NMSCT.

DESIGN

Seventy-three patients undergoing NMSCT under the Campath 1H (humanized anti-CD52 antibody) protocol were studied. Pretransplant and sequential posttransplant bone marrow specimens were evaluated and the findings were correlated with corresponding engraftment data.

RESULTS

Pretransplant bone marrow specimens from 43% of the patients were involved by disease, and these marrow specimens were significantly more cellular than those that were free of disease. Morphologically detectable disease was still present in day 14 posttransplant marrow specimens in more than one half of these patients, but there was no difference in engraftment in those with or without marrow disease. Early posttransplant marrow in nearly one half of the patients showed myeloid hyperplasia and atypical localization of immature myeloid precursors. Marrow cellularity for the first 2 months after NMSCT was significantly lower in those patients receiving stem cells mismatched at 1 to 3 loci as compared with those who received fully matched grafts (mean cellularity, 38.1% vs 54.1% at day 14). Marrow failure without recurrent disease at 3 to 6 months after transplant was detected by engraftment study in only approximately 15% of cases. Similarly, early recurrence of disease was detected first by morphologic examination in 4 of 13 cases before a decline in donor engraftment occurred.

CONCLUSION

Morphologic examination of bone marrow provides additional information that is complementary to donor engraftment analysis for optimal management after NMSCT.

Bone marrow histopathology in the diagnosis of chronic myeloproliferative disorders: A forgotten pearl

Histopathology of bone marrow (BM) biopsies plays a crucial role in the interdisciplinary approach to diagnosis and classification of chronic myeloproliferative disorders (CMPDs). Based on careful clinicopathologic studies, BM features are critical determinants that help to predict overall prognosis, to detect complications such as progression to myelofibrosis and blast crisis, and to assess therapy-related changes. A systematic evaluation of BM histopathology allows an objective identification of cases of (true) essential thrombocythemia (ET) and their separation from (false) ET, which often is the prodromal stage of chronic idiopathic myelofibrosis (CIMF). By follow-up examinations that include BM biopsies, the progression of the disease process is unveiled, which is especially important for patients with initial (early) polycythemia vera and prefibrotic CIMF that may require a different therapeutic approach than the full-blown stages. In conclusion, BM biopsy should be considered as major diagnostic tool for evaluation and follow-up of patients enrolled in prospective studies.

A critical reappraisal of the WHO classification of the chronic myeloproliferative disorders

Following the introduction of the WHO classification of chronic myeloproliferative disorders (MPDs), after approximately 5 years, a critical reappraisal appears to be warranted. Retrospective clinico-pathological evaluations conducted in the meantime, as well as the detection of new biomarkers, may aid in testing the validity of these new criteria. Based on a large series of patients with chronic myeloid leukemia (CML), an analysis of bone marrow (BM) features and risk classifications revealed that the fiber content exerted a most important and independent impact on prognosis. This finding was also supported in a prospective randomized study and therefore myelofibrosis should be included in any staging system in CML related to survival. Moreover, it is important to emphasize the dynamics of the disease process in MPDs, especially in polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF). Latent-stage PV is difficult to recognize when adhering to the proposed limits for hemoglobin (or red cell mass) without regarding the erythropoietin (EPO) level, endogenous erythroid colonies (EECs) or BM histopathology. Initial PV may firstly present with complications and, when accompanied by a high platelet count, mimics essential thrombocythemia (ET). Consequently, BM morphology and EPO level should be entered as major diagnostic criteria for PV. To document more accurately the progress of disease, a simplified scoring system concerning myelofibrosis has to be included in the histological description of CIMF. The diagnostic guidelines of BM features in ET should be improved because, usually, there is neither a significant proliferation nor left-shifting of the granulo- and erythropoiesis detectable and no relevant increase in reticulin. A comparison of clinical data and BM morphology reveals that biomarkers (EPO, EECs, PRV-1, JAK2) show an overlapping pattern of positivity between the different subtypes of MPDs.

Morphology of the bone marrow after stem cell transplantation

In many haematological conditions the only curative option is stem cell (SCT) or bone marrow (BM) transplantation. Little information exists about BM morphology following non-ablative engraftment. During the pretransplantation period and depending on the kind of pretreatment, there may be hypoplasia, residual disease and varying degrees of fibrosis. In the post-transplantation period, after 1-3 weeks of transfusion-dependent pancytopenia, the first signs of successful engraftment are indicated by the recurrence of neutrophils, monocytes and erythrocytes in the peripheral blood. In the BM there is slow regeneration of erythropoiesis, followed by the other lineages of haematopoiesis and increase in reticulin fibres or even a resolution of fibrosis. Diagnostic problems arise when neoplastic lympho- or haematopoiesis are maintained following transplantation. Moreover, there may be a significant graft versus tumour response reaction or an already relapsing disease needing aggressive treatment. On the other hand, a conspicuous dyshaematopoiesis should not be mistaken as representing a myelodysplastic syndrome. The presence of granulomas being treatment-related or a manifestation of intercurrent granulomatous disease has to be considered. More advanced knowledge of the histological features of regenerating BM will certainly aid the recognition of relapsing disease and is needed for the adequate reporting of post-transplant alterations associated with a successful or failing engraftment.

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.

Activation of transforming growth factor-beta1/p38/Smad3 signaling in stromal cells requires reactive oxygen species-mediated MMP-2 activity during bone marrow damage

Dose-escalated chemotherapy has proven utility in a variety of treatment settings, including preparative regimens before bone marrow or hematopoietic stem cell transplantation. However, the potential damage imposed by aggressive regimens on the marrow microenvironment warrants further investigation. In the present study, we tested the hypothesis that dose-escalated chemotherapy, with etoposide as a model chemotherapeutic agent, activates the transforming growth factor beta-1 (TGF-beta1) signaling pathway in bone marrow stromal cells. After high-dose etoposide exposure in vitro, Smad3 protein was phosphorylated in a time-and dose-dependent manner in marrow-derived stromal cells, coincident with the release of active and latent TGF-beta1 from the extracellular matrix. Phosphorylation was modulated by p38 kinase, with translocation of Smad3 from the cytoplasm to the nucleus subsequent to its phosphorylation. Etoposide induced activation of TGF-beta1 followed the generation of reactive oxygen species and required matrix metalloproteinase-2 (MMP-2) protein availability. Chemotherapy effects were diminished in MMP-2(-/-) knockout stromal cells and TGF-beta1 knockdown small interfering RNA-transfected stromal cells, in which phosphorylation of Smad3 was negligible after etoposide exposure. Stable transfection of a human MMP-2 cDNA into bone marrow stromal cells resulted in elevated phosphorylation of Smad3 during chemotherapy. These data suggest TGF-beta1/p38/Smad3 signaling cascades are activated in bone marrow stromal cells after dose-escalated chemotherapy and may contribute to chemotherapy-induced alterations of the marrow microenvironment.

Mixed chimerism of bone marrow vessels (endothelial cells, myofibroblasts) following allogeneic transplantation for chronic myelogenous leukemia

Experimental findings support the hypothesis that within the functional network of the bone marrow (BM) microenvironment the endothelial cells (ECs) exert a pivotal role as gatekeepers by controlling the trafficking and homing of progenitor cells. However, little information is available concerning the origin of ECs after allogeneic bone marrow transplantation (BMT) in CML. To determine the extent of mixed chimerism (MCh) a simultaneous immunohistochemical and fluorescence in-situ hybridization (FISH) study was performed on BM biopsies derived from patients following sex-mismatched BMT with full unmanipulated BM. ECs were identified by their staining with CD34 and the myofibroblasts (MFs) of large vessels were labeled by an antibody against alpha-smooth muscle actin. For sex-typing and demonstration of the bcr/abl fusion product appropriate commercially available probes and detection systems were applied. Contrasting a total congruence of labeling in control samples five patients showed donor type ECs in the early posttransplant period in about 20%. In the remaining four patients the amount of donor type ECs increased slightly after the third month up to 30%. A total of 26 MFs could be identified lining large capillaries and arterioles that exclusively revealed a host origin. Following successful engraftment only very few of the persistent host-derived ECs also displayed the bcr/abl gene. In five patients, a conversion of MCh from donor to host type ECs was recognizable during the evolution of leukemic relapse. This finding was accompanied by a bcr/abl rearrangement of about 10% of these cells. In conclusion, following myelo-ablative therapy, a survival of a considerable number of ECs and MFs of the vessel walls has been found implying persistence of host-derived vascular structures of the BM stroma. However, in only a small proportion bcr/abl+ ECs and thus minimal residual disease was detectable. Evolution of leukemic relapse was characterized by conversion of MCh with almost total loss of donor type ECs and increase in number of bcr/abl+ ECs.

Mixed chimerism of bone marrow CD34+ progenitor cells (genotyping, bcr/abl analysis) after allogeneic transplantation for chronic myelogenous leukemia

BACKGROUND

Although CD34 progenitors play a crucial role during bone marrow transplantation (BMT), there is only scant knowledge concerning their lineage-restricted mixed chimerism (MCh).

METHODS

An immunohistochemical and fluorescence in situ hybridization study was performed on bone marrow biopsies derived from 11 patients with chronic myelogenous leukemia after sex-mismatched BMT to quantify the CD34 cell population and their expression. After proper identification by a lineage-specific monoclonal antibody, X chromosome- and Y chromosome-specific probes were used for sex typing and for labeling of the locus commercially available detection systems were applied.

RESULTS

After successful engraftment, 241 progenitor cells were identified at days 9 to 586 of the posttransplant period. Overall incidence of MCh was 24% with a tendency to decline after day 100 to 15%. The gene was detectable in only 10% of these precursors and decreased to less than 4% after more than 6 months. Approximately 0.5 to 5.5 years after BMT in six patients, a manifest leukemic relapse occurred, which was accompanied by a conversion of donor-to-host-type progenitors. This phenomenon involved up to 94% of the 303 evaluable CD34 cells and also included a retrieval of the translocation gene in approximately 50% of this population.

CONCLUSION

The lineage-restricted MCh of progenitors after BMT is in keeping with the assumption that leukemic (bcr/abl ) precursors represent only a fraction of the total host-derived (chimeric) CD34 cells. These residual clonally transformed progenitors survive myeloablative treatment and thus may be the source for a later relapse.

Dynamics of CD34+ progenitor cells following allogeneic bone marrow transplantation in Ph1+CML--an immunohistochemical study on 113 patients with sequential trephine biopsies

A retrospective immunohistological and morphometric study was performed on bone marrow trephine biopsies derived from 113 patients with Philadelphia chromosome-positive chronic myeloid leukemia (Ph(1+)-CML) before and at standardized intervals following allogeneic transplantation (BMT) with full unmanipulated marrow specimens. The purpose of this investigation was to quantify CD34+ progenitor cells and to determine their dynamics during the post-transplant period. Moreover, we tried to correlate their number with corresponding changes in the amount of nucleated erythroid precursors and megakaryocytes including pro- and megakaryoblasts and the fiber content. Monitoring the quantity of precursors after BMT revealed a very rapid recovery in comparison to a control group. However, a more detailed evaluation showed that at day 22 +/- 6 a higher number of progenitor cells was significantly associated with an earlier independence for platelet transfusion and also with a more pronounced growth of erythro- and megakaryopoiesis including their precursor cells. Furthermore, a slight increase in the density of the fibrous matrix (reticulin fibers) was present in these patients that were characterized by a more favorable engraftment. The latter feature sheds some light on the complex pathomechanisms of homing and differentiation of progenitors. In confirmation with in vitro findings, this phenomenon is dependent on proper anchoring sites to the fibrous bone marrow stroma. Finally, the size of a full BM graft exerted a distinctive influence on the number of CD34+ precursors in the early post-transplant period. In conclusion, the present study has validated a number of BM features by focusing on the CD34+ progenitor cells and associated hematopoietic reconstitution including reticulin fibers and precursor cells of the erythroid and megakaryocyte lineage, which are not readily evaluable by fluorescence-activated cell sorting (FACS) analysis.

Comparative effects of interferon and hydroxyurea on bone marrow fibrosis in chronic myelogenous leukemia

Therapy-related changes of the bone marrow fiber content remain a controversial issue in hematopathology. This conflict of opinion firstly depends on difficulties to determine the quantity of fibers exactly (semiquantitative grading, morphometry, reference to cellularity). Secondly, the appropriate selection of patients with specific monotherapies including hydroxyurea (HU) and interferon-alpha (IFN) seems to present some problems. Finally, assessment of myelofibrosis is further biased by the different endpoints of sequential examinations. The latter shortcoming can be improved upon by the calculation of the myelofibrosis progression/regression index which describes the ratio between difference of fiber density and observation time. Using strictly defined therapeutic regimens and intervals between sequential trephine biopsies a stimulating effect of IFN administration on bone marrow fibrosis in Ph1+-chronic myelogenous leukemia (CML) has been found. This result is comparable with the failure of this agent to improve myelofibrosis (and splenomegaly) in a considerable number of patients with allied subtypes of chronic myeloproliferative disorders. This is in contrast to the effect HU exerts which is a more fibrolytic or even stabilizing influence on bone marrow fibrosis. This phenomenon is readily demonstrable by the assessment of dynamic features (myelofibrosis progression index). In addition, patients showing a rapid progression of myelofibrosis during IFN and HU treatment of Ph1+-CML are generally associated with a poor risk outcome and a significant worsening of survival.

Bone marrow features improve prognostic efficiency in multivariate risk classification of chronic-phase Ph(1+) chronic myelogenous leukemia: a multicenter trial

PURPOSE

Multivariate risk classifications for chronic (stable)-phase Ph(1+) chronic myelogenous leukemia (CML) are generally focused on hematologic variables, and the putative prognostic property of bone morphology has been neglected or even contested so far.

PATIENTS AND METHODS

A total of 510 consecutively recruited patients in first chronic phase Ph(1+) CML and pretreatment bone marrow biopsy specimens were entered onto this multicenter observational trial to evaluate the effect of bone marrow histopathology. According to generally accepted criteria, patients with any signs of accelerated disease were excluded. Treatment modalities included administration of interferon alfa-2b (IFN) and chemotherapy with hydroxyurea (HU) or busulfan. Immunohistochemical and morphometric techniques were applied to identify marrow cells and to quantify fiber density. Patients were separated into learning and validation samples, and classification and regression tree (CART) analysis was performed to establish a prognostic decision tree.

RESULTS

CART analysis of the validation sample (123 patients with HU therapy) revealed the amount of erythroid precursors in the bone marrow, myelofibrosis, and splenomegaly as the most important prognostic features. Three risk profiles with significantly different survival patterns were established, with median survival times ranging from 33 to 108 months (two-sided log-rank test, P =.0001). The new score was confirmed by application to the learning sample with IFN therapy (two-sided log-rank test, P =.0002). Furthermore, risk status defined by the new score was significantly correlated with the occurrence of blast transformation.

CONCLUSION

Our data strongly implicate that prognostic classification of chronic-phase Ph(1+) CML can be significantly improved by the inclusion of morphologic parameters. The variables of the presented scoring system may be easily assessed by routinely processed aspirates and bone marrow trephines.