Response of chronic myelogenous leukemia patients to COAP-splenectomy. A Southwest Oncology Group study

Splenic red pulp macrophages provide a niche for CML stem cells and induce therapy resistance

Disease progression and relapse of chronic myeloid leukemia (CML) are caused by therapy resistant leukemia stem cells (LSCs), and cure relies on their eradication. The microenvironment in the bone marrow (BM) is known to contribute to LSC maintenance and resistance. Although leukemic infiltration of the spleen is a hallmark of CML, it is unknown whether spleen cells form a niche that maintains LSCs. Here, we demonstrate that LSCs preferentially accumulate in the spleen and contribute to disease progression. Spleen LSCs were located in the red pulp close to red pulp macrophages (RPM) in CML patients and in a murine CML model. Pharmacologic and genetic depletion of RPM reduced LSCs and decreased their cell cycling activity in the spleen. Gene expression analysis revealed enriched stemness and decreased myeloid lineage differentiation in spleen leukemic stem and progenitor cells (LSPCs). These results demonstrate that splenic RPM form a niche that maintains CML LSCs in a quiescent state, resulting in disease progression and resistance to therapy.

Identification of human chronic myelogenous leukemia progenitor cells with hemangioblastic characteristics

Overwhelming evidence from leukemia research has shown that the clonal population of neoplastic cells exhibits marked heterogeneity with respect to proliferation and differentiation. There are rare stem cells within the leukemic population that possess extensive proliferation and self-renewal capacity not found in the majority of the leukemic cells. These leukemic stem cells are necessary and sufficient to maintain the leukemia. Interestingly, the BCR/ABL fusion gene, which is present in chronic myelogenous leukemia (CML), was also detected in the endothelial cells of patients with CML, suggesting that CML might originate from hemangioblastic progenitor cells that can give rise to both blood cells and endothelial cells. Here we isolated fetal liver kinase-1-positive (Flk1+) cells carrying the BCR/ABL fusion gene from the bone marrow of 17 Philadelphia chromosome-positive (Ph+) patients with CML and found that these cells could differentiate into malignant blood cells and phenotypically defined endothelial cells at the single-cell level. These findings provide direct evidence for the first time that rearrangement of the BCR/ABL gene might happen at or even before the level of hemangioblastic progenitor cells, thus resulting in detection of the BCR/ABL fusion gene in both blood and endothelial cells.

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

Chronic myelogenous leukemia: laboratory diagnosis and monitoring

Rapid developments have occurred both in laboratory medicine and in therapeutic interventions for the management of patients with chronic myelogenous leukemia (CML). With a wide array of laboratory tests available, selecting the appropriate test for a specific diagnostic or therapeutic setting has become increasingly difficult. In this review, we first discuss, from the point of view of laboratory medicine, the advantages and disadvantages of several commonly used laboratory assays, including cytogenetics, fluorescence in situ hybridization (FISH), and qualitative and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We then discuss, from the point of view of clinical care, the test(s) of choice for the most common clinical scenarios, including diagnosis and monitoring of the therapeutic response and minimal residual disease in patients treated with different therapies. The purpose of this review is to help clinicians and laboratory physicians select appropriate tests for the diagnosis and monitoring of CML, with the ultimate goal of improving the cost-effective usage of clinical laboratories and improving patient care.

Splenectomy in chronic myeloid leukemia and myelofibrosis with myeloid metaplasia

Myelofibrosis with myeloid metaplasia (MMM) is a collective term that describes the related disorders AMM, PPMM, and PTMM. The chronic myeloid disorders include chronic myeloid leukemia, polycythemia vera, essential thrombocythemia, and agnogenic myeloid metaplasia (myelofibrosis). These disorders display varying propensities for pathologic enlargement of the spleen which can lead to mechanical discomfort, hypercatabolic symptoms, anemia, thrombocytopenia, and portal hypertension. Splenectomy has been found to be of little benefit in the early stages of chronic myeloid leukemia. Similarly, the benefit of splenectomy in advanced cases is limited to symptomatic palliation and treatment of delayed engraftment after allogeneic bone marrow transplantation. Although polycythemia vera and essential thrombocythemia are also characterized by splenomegaly, splenectomy is not considered a therapeutic option in the absence of transformation of the disease into myelofibrosis with myeloid metaplasia. Splenectomy has been studied most in myelofibrosis with myeloid metaplasia. Although there is no clear survival advantage to splenectomy in this disorder, the surgical procedure can result in substantial palliation of mechanical discomfort, hypercatabolic symptoms, portal hypertension, and anemia. However, the procedure is associated with an approximately 9% mortality rate, and the postsplenectomy occurrence of extreme thrombocytosis, hepatomegaly, and leukemic transformation is of major concern.

Splenectomy in the accelerated or blastic phase of chronic myelogenous leukemia: a single-institution, 25-year experience

BACKGROUND

Patients in the accelerated or blastic phases of chronic myelogenous leukemia (CML) often have painful splenomegaly and secondary thrombocytopenia. We tested the hypothesis that splenectomy can be performed with minimal complications in advanced CML, thereby alleviating pain, reversing thrombocytopenia, and minimizing transfusion requirements.

METHODS

We reviewed the records of 53 patients in the accelerated or blastic phases of CML who underwent splenectomy between 1970 and 1995 at the U. T. M. D. Anderson Cancer Center.

RESULTS

Twenty-eight patients were in accelerated phase and 25 in blastic phase at the time of splenectomy. The most common indications for splenectomy were symptomatic splenomegaly (median splenic weight, 1000 gm; range, 120 to 6700 gm) or thrombocytopenia (platelet count less than 100,000/microliter) or both. There was 1 death within 30 days of splenectomy. The preoperative platelet count increased 3.72-fold +/- 0.53-fold (mean +/- SEM) by postoperative day 7 (p < 0.001; paired t test). Patients with transfusion-dependent thrombocytopenia had significantly fewer platelet and red blood cell transfusions in the 6 months after splenectomy than in the 6 months before splenectomy (p = 0.016; sign test).

CONCLUSIONS

Splenectomy can be performed with minimal morbidity and mortality in advanced CML, thereby relieving symptomatic splenomegaly, reversing thrombocytopenia, and minimizing transfusion requirements.

Chemotherapy of chronic haematological malignancies

After years of stagnation in the treatment of chronic haematological malignancies, some interesting agents have emerged which might improve the prognosis of these diseases. For chronic leukaemias of lymphoid lineage, three new chemical agents, all purine analogues, seem to be of particular interest. Pentostatin is a specific inhibitor of ADA and has been shown to be highly efficient in producing CR in patients with HCL. Its relative merit compared with IFN-alpha for the treatment of HCL is being studied in ongoing randomized trials. Pentostatin is also active in B-CLL and promising activities have been demonstrated in T- or B-PLL and ATCL. Fludarabine is an analogue of adenine which is resistant to the deamination of ADA. It has been reported to be highly active for patients with both pretreated or non-treated B-CLL. CR rates of 13% with overall response rates of 57% can be achieved, even in heavily pretreated patients. Its activity in the other lymphoid malignancies is not yet known. CdA, a substrate analogue of ADA, has also produced encouraging results in B-CLL, HCL and T cell malignancies, and in some patients with just one single course. Thus far, experience with this drug comes from one institution and requires further confirmation. For chronic myeloproliferative diseases, little progress has yet been made. Although IFN-alpha seems to be active in CML and to result in cytogenetic remissions in bone marrow, a definite advantage of this biological agent over conventional chemotherapy as regards survival and life quality has not yet been proven. Allogeneic bone marrow transplantation is beneficial for those patients who are eligible. No remarkable advances have been made in the treatment of myeloproliferative disorders except for the development of an antiplatelet drug, anagrelide. This agent seems to be highly effective in controlling thrombocytosis. The relative merit of this agent as compared with IFN-alpha, as well as the impact of this agent on the survival and on life-quality of patients with myeloproliferative disorders, have yet to be defined.

Unexpected splenic nodules in leukemic patients

We reviewed a series of five splenectomy specimens from patients with various leukemias (three cases of chronic myelocytic leukemia, one case of acute myelocytic leukemia, and one case of hairy cell leukemia). In addition to diffuse red pulp disease, we unexpectedly encountered nodules grossly in each of the specimens. These represented sea blue histiocytosis (one case), focal hairy cell leukemia (one case), localized blast transformation (one case), and concentrated foci of treated leukemia (two cases), with a prominence of immature granulocytic precursors on a background of trilineage hyperplasia. These cases are reported because they are unusual and because they furnish interesting correlates of gross and microscopic anatomy.

[Splenectomy: surgical indications in malignant hematologic diseases]

Indications for splenectomy in malignant hematological diseases are discussed for relief of symptoms (splenomegaly, cytopenias), for staging (M. Hodgkin) or improvement of survival (hairy cell leukemia). The role of splenectomies is also evaluated for Non-Hodgkin lymphomas, chronic lymphatic leukemia, myelofibrosis and for chronic myeloic leukemia.

Busulphan versus combination chemotherapy for initial treatment of chronic granulocytic leukaemia

In a pilot study, 21 consecutive and previously untreated adults with chronic granulocytic leukaemia received either busulphan (group 1: n = 11) or a combination of the epipodophyllotoxin VP16-213 with cytosine arabinoside and doxorubicin (group 2: n = 10). Using a standardised protocol, objective response, defined as a granulocyte count consistently less than 10 X 10(9)/1 with no clinical evidence of the disease, was achieved in 45 and 40% of the patients, respectively, and median survivals were 89 and 107 weeks (p greater than 0.05). Although there was no difference in morbidity, the study was discontinued because the combination chemotherapy was more complex to administer, was associated with greater patient inconvenience, and offered no advantage over single-agent therapy in managing the stable phase of chronic granulocytic leukaemia.