Effects of the tyrosine kinase inhibitor imatinib mesylate (STI571) on bone marrow features in patients with chronic myelogenous leukemia

Preliminary data are available about bone marrow (BM) changes in patients with chronic myeloid leukemia (CML) who received the molecularly targeted and highly effective tyrosine kinase inhibitor Imatinib mesylate (STI571). This review is focused on a systematic assessment of BM features detectable at different stages of CML (stable, accelerated, blastic) following long-term (more than 10 months) treatment. By applying enzyme- and immunohistochemistry including monoclonal antibodies visualizing proliferating cell nuclear antigen (PCNA) and apoptosis (anti-apostatin), a more elaborate insight into alterations affecting hematopoiesis and the stroma compartment was gained. In patients with stable-phase CML therapy resulted in a significant reduction in cellularity, neutrophil granulopoiesis and number of megakaryocytes, accompanied by a retrieval of erythroid precursors. In patients with Imatinib as the only treatment morphometric analysis of CD61+ megakaryopoiesis was in keeping with a significant decrease in maturation defects implying a lesser amount of atypical micromegakaryocytes almost consistent with normalization. Moreover, a reduction of the initially enhanced (CD34+) microvessel density was detectable associated with a decrease in luminal distension. Regression of marked to moderate myelofibrosis was recognizable in about 70% of patients especially in the accelerated and blastic phases. The amount of myeloblasts, CD34+ progenitor cells and lysozyme-expressing immature myelomonocytic cells declined with treatment, but recurred in about 19% of patients that developed a leukemic relapse after 21+/-6 months of therapy. Data on proliferative activity and apoptosis in general supported in vitro findings concerning the inhibitory effect of this agent on growth associated with a tendency for stimulated apoptosis, at least in responding patients.     

Angiogenesis and the role of bone marrow endothelial cells in haematological malignancies

Increased microvessel density (MVD) has been observed in the bone marrow (BM) of patients with multiple myeloma (MM), acute lymphoblastic leukaemia, acute myeloid leukaemia, and myelodysplastic and myeloproliferative syndrome. The MVD is the net result of cumulative phases of angiogenesis and angio-regression and is as such not an indicator of the ongoing angiogenesis at the time of biopsy. There is, therefore, a need for additional methods that allow the estimation of ongoing angiogenesis. Double immunostainings for CD34 and Ki-67 can be used on paraffin-embedded tissue to determine the endothelial proliferation fraction. The BM endothelial cells, as a component of the BM stroma, have a close interaction with the malignant cells. In MM, for example, they are involved in the specific homing and are a source of paracrine growth factors. Targeting the BM microvessels will not only influence the nutrient and oxygen supply, but will in addition reduce the growth stimuli provided by the EC.     

Therapy-related changes of the bone marrow in chronic idiopathic myelofibrosis

In chronic myeloproliferative disorders (CMPDs) a conflict of opinion exists regarding therapy-induced bone marrow (BM) changes and the evolution of myelofibrosis during the lengthy course of the disease. For a more elaborate study of these features chronic idiopathic myelofibrosis (IMF) seems to be a most suitable condition. Therefore this review is focused on this CMPD and amongst other findings analyzes data from a series of 340 patients with a long follow-up including 893 biopsies (median interval of 32 months). The ensuing results were compared with those communicated in the relevant literature. In addition to a control group of 153 patients with IMF who received only symptomatic treatment, therapy groups included busulfan, hydroxyurea, interferon and various combinations. In all groups hypoplasia of a varying degree was a frequent finding (6%) and often accompanied by a patchy arrangement of hematopoiesis. Most conspicuous was a gelatinous edema showing a tendency to develop a discrete reticulin fibrosis (scleredema). Aplasia developed in 7.7% of patients, usually at terminal stages of the disease independently of treatment. Minimal to moderate maturation defects of hematopoiesis involved especially megakaryocytes and erythroid precursors, but overt myelodysplastic features were most prominent following hydroxyurea and busulfan therapy. Acceleration and blastic crisis were characterized not only by increasing dysplastic changes, but also by the appearance of blasts including CD34+ cells. Semiquantitative grading of the fiber content revealed that 183 patients (54%) without or with moderate fibrosis at the beginning showed a significant progression and therefore contrasted with the 66 patients with a stable state. Following this calculation no relevant differences in the evolution of myelofibrosis were evident in the various therapy groups especially not following interferon treatment. In a few patients a regression was found which was accompanied by a severe hypoplasia or aplasia compatible with a myelo-ablative effect. In conclusion, peculiar BM changes, in particular conspicuously expressed myelodysplastic features are consistent with therapy-related lesions. Development of myelofibrosis in IMF is obviously due to disease progression unrelated to stage at diagnosis and not significantly influenced by treatment modalities.     

Bone marrow angiogenesis and angiogenic factors in multiple myeloma treated with novel agents

Introduction. An increased bone marrow (BM) angiogenesis is associated with poor outcome in multiple myeloma (MM). Objective. Angiogenesis study in MM treated with novel antimyeloma agents: thalidomide, lenalidomide, bortezomib, and with dexamethasone. Patients and methods. Forty-four patients with MM (14 newly diagnosed, 30 refractory/relapsed) were treated with novel agents at our institution. A BM biopsy was obtained before the initiation of therapy in 19. Angiogenesis was assessed by microvessel density (MVD) estimation in BM biopsies stained with the monoclonal anti-CD34 antibody, and by serum levels of angiogenic factors (VEGF, bFGF, and HGF) and cytokines (IL-6 and TNF-α). Results. A positive correlation was found between BM plasma cell involvement and MVD estimation (p = 0.01). However, MVD was not significantly correlated with either disease phase (p = 0.065) or response to therapy (p = 0.79). Neither baseline serum levels of angiogenic cytokines correlated to response to treatment. No significant correlation was found between BM MVD and serum levels of angiogenic cytokines. Serum levels of angiogenic cytokines before and after therapy showed a significant increase of bFGF (p = 0.008). Conclusion. There is no relationship between MVD estimation and baseline serum levels of angiogenic cytokines, neither between each of them and response to therapy.     

Digital image analysis and stereology of angiogenesis in polypoid and nonpolypoid colorectal adenomas

OBJECTIVE: To evaluate 3-dimensional parameters and bidimensional microvascular quantification in the different morphologic presentations of colorectal adenomas. STUDY DESIGN: A study was carried out, including 102 neoplastic colorectal lesions obtained by endoscopy or surgical resection. For the analysis of angiogenesis, immunohistochemistry, digital image analysis, microvascular quantification and stereology were used. RESULTS: Microvascular quantification, volume and microvascular length estimate rose gradually with high grade dysplasia as compared to the low grade ones (P < .001). There was no significant difference in angiogenesis between polypoid and nonpolypoid colorectal adenomas in terms of quantification and microvascular length estimate. CONCLUSION: The use of digital image analysis and stereology added greater objectivity and effectiveness to angiogenic evaluation because they allowed accurate segmentation of hypervascular areas, representation of the characteristic 3-dimensional morphology of the vascular supply and identification of differences in microvascularization in the developmental stages of colorectal cancer. However, no significant relation could be found between macroscopic type and angiogenesis, suggesting that angiogenesis may contribute little to morphogenesis of colorectal adenomas.     

兔VX2肺外周肿瘤超声造影特征与CD31和CD34微血管密度的相关性研究

摘要 目的：探讨兔VX2肺外周肿瘤超声造影特征与CD31和CD34微血管密度的相关性研究。方法：15只雌性新西兰白兔进行VX2 肺肿瘤模型，总共有30个VX2 癌植入15只兔子的肺中。通过高倍镜分析不同期VX2肿瘤的MVD。通过双重免疫荧光化学染色分析不同生长期VX2肿瘤Ki67和CD31阳性表达。分析肿瘤形态学组织病理学结果与微血管分布和CEUS结果之间的相关性。结果：随着生长周期的进展，VX2肿瘤的MVD增大（P<0.05）。随着生长周期的进展，VX2肿瘤内Ki67和CD31的阳性表达率增加（P<0.05）。CEUS显示VX2 肿瘤在早期动脉期有明显的外周增强和短暂的内部增强。肺外周VX2 肿瘤中 PI和CD31 MVD值之间呈显著正相关性（r=0.734，P<0.05）。CD31 MVD和CD34 MVD之间呈负相关（r=-0.691，P<0.05）。PI和CD34 MVD值之间不存在显著相关性（r=-0.412，P>0.05）。结论：与CD34 MVD 相比，CD31 MVD 可以更有效地评估肿瘤血管生成。CEUS作为一种无创成像方法，可以有效评估兔周围型肺癌的肿瘤血管生成情况。     

Rapid analysis of vessel elements (RAVE): a tool for studying physiologic, pathologic and tumor angiogenesis

Quantification of microvascular network structure is important in a myriad of emerging research fields including microvessel remodeling in response to ischemia and drug therapy, tumor angiogenesis, and retinopathy. To mitigate analyst-specific variation in measurements and to ensure that measurements represent actual changes in vessel network structure and morphology, a reliable and automatic tool for quantifying microvascular network architecture is needed. Moreover, an analysis tool capable of acquiring and processing large data sets will facilitate advanced computational analysis and simulation of microvascular growth and remodeling processes and enable more high throughput discovery. To this end, we have produced an automatic and rapid vessel detection and quantification system using a MATLAB graphical user interface (GUI) that vastly reduces time spent on analysis and greatly increases repeatability. Analysis yields numerical measures of vessel volume fraction, vessel length density, fractal dimension (a measure of tortuosity), and radii of murine vascular networks. Because our GUI is open sourced to all, it can be easily modified to measure parameters such as percent coverage of non-endothelial cells, number of loops in a vascular bed, amount of perfusion and two-dimensional branch angle. Importantly, the GUI is compatible with standard fluorescent staining and imaging protocols, but also has utility analyzing brightfield vascular images, obtained, for example, in dorsal skinfold chambers. A manually measured image can be typically completed in 20 minutes to 1 hour. In stark comparison, using our GUI, image analysis time is reduced to around 1 minute. This drastic reduction in analysis time coupled with increased repeatability makes this tool valuable for all vessel research especially those requiring rapid and reproducible results, such as anti-angiogenic drug screening.     

Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis

To examine the role of endothelial heparan sulfate during angiogenesis, we generated mice bearing an endothelial-targeted deletion in the biosynthetic enzyme N-acetylglucosamine N-deacetylase/N-sulfotransferase 1 (Ndst1). Physiological angiogenesis during cutaneous wound repair was unaffected, as was growth and reproductive capacity of the mice. In contrast, pathological angiogenesis in experimental tumors was altered, resulting in smaller tumors and reduced microvascular density and branching. To simulate the angiogenic environment of the tumor, endothelial cells were isolated and propagated in vitro with proangiogenic growth factors. Binding of FGF-2 and VEGF(164) to cells and to purified heparan sulfate was dramatically reduced. Mutant endothelial cells also exhibited altered sprouting responses to FGF-2 and VEGF(164), reduced Erk phosphorylation, and an increase in apoptosis in branching assays. Corresponding changes in growth factor binding to tumor endothelium and apoptosis were also observed in vivo. These findings demonstrate a cell-autonomous effect of heparan sulfate on endothelial cell growth in the context of tumor angiogenesis.     

Bone marrow biopsy (BMB). II. Bone marrow biopsy in myeloproliferative disorders

The myeloproliferative disorders (MPD) are a domain in which the bone marrow biopsy (BMB) greatly proved its utility. We have studied the histology of the bone marrow (BM) in all the four entities of MPD: chronic myeloid leukemia (CML) with its subtype, chronic megakaryocytic granulocytic myelosis (CMGM), polycythemia vera (PV), hemorrhagic thrombocythemia (HT) and myeloid metaplasia with myelofibrosis (MMM). The work presents in short some of the clinical and hematologic characters of MPD with special stress upon the histologic modifications of BM, either specific or common to all MPD entities, underlying also the criteria for differential diagnosis.     

Expression of the proliferation-associated nuclear protein MIB-1 and its relationship with microvascular density in bone marrow biopsies of patients with myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a group of disorders characterized by dysplastic hemopoiesis and an increased risk of leukemic transformation. The process of angiogenesis has been implicated in the pathogenesis and evolution of MDS. In this study the proliferative activity and extent of angiogenesis was examined in bone marrow samples from 54 patients with MDS in relation to clinicopathologic features. Cellular proliferation and microvascular density (MVD) were examined immunohistochemically, using the monoclonal antibody MIB-1 (Ki-67) and an anti-CD34 monoclonal antibody respectively. Serum concentrations of interleukin-6 (IL-6) were measured by ELISA. The results showed that the MIB-1 Labeling Index (MIB-1 LI), MVD and IL-6 increased significantly with advancing severity of disease. Among the MDS-FAB subtypes, MIB-1 LI, MVD and IL-6 were significantly higher in RAEB-t, RAEB and CMML in comparison to RA and RARS (p < 0.0001 in all cases). Similarly, MIB-1 and MVD were increased in patients with score 3 in comparison to scores 0 and 1 in the IPSS system (p < 0.05). All parameters studied were significantly higher in patients versus controls. We conclude that cellular proliferative activity and angiogenesis are associated with disease progression in MDS patients.     

Mucosal microvascular organization of the rat colon

The mucosal microvascular architecture of the rat colon is described from vascular casts and intravital microscopy. Arterial break-up into the mucosal capillary bed invariably occurs at the submucosal/mucosal interface. The mucosal capillaries drain into venules only at the opposing, luminal aspect, i.e., mucosal venules transverse the mucosa without receiving further capillary tributaries. Intravital microscopy of luminal flow confirmed cast predictions. Further, capillary flow was unusually unidirectional, i.e., rarely static or reversible. The possible functional importance of this particular microvascular architecture to water absorption in the colon is discussed.     

Ultrastructural localization of the vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) receptor-2 (FLK-1, KDR) in normal mouse kidney and in the hyperpermeable vessels induced by VPF/VEGF-expressing tumors and adenoviral vectors.

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) interacts with two high-affinity tyrosine kinase receptors, VEGFR-1 and VEGFR-2, to increase microvascular permeability and induce angiogenesis. Both receptors are selectively expressed by vascular endothelial cells and are strikingly increased in tumor vessels. We used a specific antibody to localize VEGFR-2 (FLK-1, KDR) in microvascular endothelium of normal mouse kidneys and in the microvessels induced by the TA3/St mammary tumor or by infection with an adenoviral vector engineered to express VPF/VEGF. A pre-embedding method was employed at the light and electron microscopic levels using either nanogold or peroxidase as reporters. Equivalent staining was observed on both the luminal and abluminal surfaces of tumor- and adenovirus-induced vascular endothelium, but plasma membranes at interendothelial junctions were spared except at sites connected to vesiculovacuolar organelles (VVOs). VEGFR-2 was also localized to the membranes and stomatal diaphragms of some VVOs. This staining distribution is consistent with a model in which VPF/VEGF increases microvascular permeability by opening VVOs to allow the transendothelial cell passage of plasma and plasma proteins.     

Assessment of vascularity in histological sections: effects of methodology and value as an index of angiogenesis in breast tumours

The aims of this study were to (a) determine how the quantification of blood vessels in histological sections (vascularity) is affected by the methodology used and (b) assess the value of vascularity as an index of angiogenesis by comparing tumour and normal breast tissue. Archival specimens of breast, lung and oral carcinoma, oral dysplasia and normal breast tissue were used to test the effects of the following experimental variables on vascularity: pretreatment of the sections (enzymatic digestion, heating), endothelial markers (von Willebrand factor and CD31 antibodies), method of quantification (highest microvascular density, average microvascular density and microvascular volume) and interobserver variations. All the variables examined significantly affected the estimated vascularity; this depended on the type of tissue and method used. The pretreatment of the sections before staining was the most important variable, altering the vascularity ranking of the tumours. Vascularity in breast tumours was similar to that of the normal breast intralobular stroma, suggesting that an area of high microvascular density in the tumour does not necessarily represent tumour-induced angiogenesis. Contradictory results have been published regarding the value of vascularity as a tumour prognostic factor. Our results suggest that statistically significant differences in vascularity values are most likely to arise from failure to optimize the staining protocol and from the method used to assess vascularity. © 1998 Chapman & Hall     

Blood microcirculation and angiogenesis in wound healing by first and second intentions

Local reaction of the microvascular bed and angiogenesis of closed and infected open wounds have been studied in 72 rats. Selective contrasting of the functioning microvessels was achieved by means of intravenous injection of peroxidases, as tracers. The dynamics of microcirculatory disorders and the periods of capillary circulation recovery in the wound within 1-20 days after the injury were described. The principal resemblance of the alterations of the microvascular bed in closed and infected open wounds was established.     

An Ex Vivo Model for Anti-Angiogenic Drug Testing on Intact Microvascular Networks

New models of angiogenesis that mimic the complexity of real microvascular networks are needed. Recently, our laboratory demonstrated that cultured rat mesentery tissues contain viable microvascular networks and could be used to probe pericyte-endothelial cell interactions. The objective of this study was to demonstrate the efficacy of the rat mesentery culture model for anti-angiogenic drug testing by time-lapse quantification of network growth. Mesenteric windows were harvested from adult rats, secured in place with an insert, and cultured for 3 days according to 3 experimental groups: 1) 10% serum (angiogenesis control), 2) 10% serum + sunitinib (SU11248), and 3) 10% serum + bevacizumab. Labeling with FITC conjugated BSI-lectin on Day 0 and 3 identified endothelial cells along blood and lymphatic microvascular networks. Comparison between day 0 (before) and 3 (after) in networks stimulated by 10% serum demonstrated a dramatic increase in vascular density and capillary sprouting. Growing networks contained proliferating endothelial cells and NG2+ vascular pericytes. Media supplementation with sunitinib (SU11248) or bevacizumab both inhibited the network angiogenic responses. The comparison of the same networks before and after treatment enabled the identification of tissue specific responses. Our results establish, for the first time, the ability to evaluate an anti-angiogenic drug based on time-lapse imaging on an intact microvascular network in an ex vivo scenario.     

Angiogenesis and Antiangiogenesis in Triple-Negative Breast cancer

Several data support a central role for angiogenesis in breast cancer growth and metastasis. Observational studies have demonstrated that microvascular density (MVD) is a prognostic factor in invasive breast cancer, whereas others reached the opposite conclusion. Vascular endothelial growth factor is the most important angiogenic factor with proven significance in breast cancer, as it has been assessed in both experimental and clinical studies. Triple-negative breast cancer (TNBC) is a type of breast cancer which lacks estrogen, progesterone, and HER-2/neu receptors. MVD in both basal-like and TNBC is significantly higher than in non–basal-like and non-TNBC. In breast cancer and other malignancies, the development of agents that inhibit tumor angiogenesis has been an active area of investigation. In TNBC, clinical trials combining targeted agents and chemotherapy have failed to show substantial survival improvement. There is evidence that patients with TNBC may have a greater probability of obtaining some kind of clinical efficacy benefit from bevacizumab-based therapy.     

Tumour‐associated macrophages correlate with microvascular bed extension in colorectal cancer patients

Tumour‐associated macrophages (TAMs) represent pivotal components of tumour microenvironment promoting angiogenesis, tumour progression and invasion. In colorectal cancer (CRC), there are no conclusive data about the role of TAMs in angiogenesis‐mediated tumour progression. In this study, we aimed to evaluate a correlation between TAMs, TAM immunostained area (TAMIA) microvascular density (MVD), endothelial area (EA) and cancer cells positive to VEGF‐A (CCP‐VEGF‐A) in primary tumour tissue of locally advanced CRC patients undergone to radical surgery. A series of 76 patients with CRC were selected and evaluated by immunohistochemistry and image analysis. An anti‐CD68 antibody was employed to assess TAMs and TAMIA expression, an anti‐CD34 antibody was utilized to detect MVD and EA expression, whereas an anti‐VEGF‐A antibody was used to detect CCP‐VEGF‐A; then, tumour sections were evaluated by image analysis methods. The mean ± S.D. of TAMs, MVD and CCP‐VEGF‐A was 65.58 ± 21.14, 28.53 ± 7.75 and 63% ± 37%, respectively; the mean ± S.D. of TAMIA and EA was 438.37 ± 124.14μ² and 186.73 ± 67.22μ², respectively. A significant correlation was found between TAMs, TAMIA, MVD and EA each other (r ranging from 0.69 to 0.84; P ranging from 0.000 to 0.004). The high level of expression of TAMs and TAMIA in tumour tissue and the significant correlation with both MVD and EA illustrate that TAMs could represent a marker that plays an important role in promoting angiogenesis‐mediated CRC. In this context, novel agents killing TAMs might be evaluated in clinical trials as a new anti‐angiogenic approach.     

Decreased expression of pigment epithelium derived factor (PEDF), an inhibitor of angiogenesis, in placentas of unexplained stillbirths

Normal placental vascular development depends upon the complex interactions between angiogenic inducers and inhibitors within the placenta. Alterations within the placental microenvironment can promote an imbalance in angiogenic mediators which may be associated with adverse perinatal outcomes. The purpose of this study was to investigate the placentas of infants with unexplained stillbirth as compared to live-born infants and to determine whether alterations in angiogenic inducer vascular endothelial growth factor (VEGF) or inhibitor pigment epithelium-derived factor (PEDF) are associated with altered angiogenesis, vascular remodeling and stillbirth. Placentas of 22 unexplained stillbirths and 44 age-matched live-born controls were scored for microvascular density (MVD), vasculopathy and microvascular permeability. A subset was scored for expression of angiogenic inducer VEGF and inhibitor pigment epithelium-derived factor. Stillborn placentas demonstrated higher MVD than controls (mean+SD: 116.6+/-46.3 v. 60.8+/-13.5, respectively, p<0.001). Vasculopathy was present in 10/22 (45%) stillbirths compared to 0/44 (0%) controls (p<0.001); increased vascular permeability was present in 15/22 (68%) cases and 5/44 (11%) controls (p<0.001). PEDF expression was significantly lower in stillborn placentas (1.7+/-0.3) than live-born controls (3.6+/-0.8, p<0.01) while VEGF expression was similar (3.3+/-0.7 v. 3.7+/-0.4, respectively, p>0.05). In conclusion, we found that unexplained stillbirth is associated with loss of angiogenic inhibitor PEDF, vasculopathy and heightened angiogenesis in the placenta.     

Effect of distension on ADH-induced osmotic water flow in toad urinary bladder

Summary We recently described a method by which the resistance to water flow of the luminal membrane of ADH-stimulated toad bladder can be quantitatively distinguished from that of barriers lying in series with it. This method requires estimates of both total bladder water permeability (assessed by transbladder osmotic water flow at constant gradient) and luminal membrane water permeability (assessed by quantitation of the frequency of ADH-induced luminal membrane particle aggregates). In the present study we examined the effect of bladder distension on transepithelial osmotic water flow before and during maximal ADH stimulation. Base-line water flow was unaffected by bladder distension, but hormonally stimulated flow increased systematically as bladders became more distended. Distension had no effect on the frequency of ADH-induced intramembranous particle aggregates. By comparing the relationships between aggregate frequency and hormonally induced water permeability in distended and undistended bladders, we found that distension appeared to enhance ADH-stimulated water flow by decreasing the resistance of the series permeability barrier while the apparent water permeability associated with each single luminal membrane aggregate was unaffected. In that bladder distension causes tissue thinning, the series resistance limiting ADH-stimulated water flow appears to be accounted for by deformable barriers within the bladder tissue itself, probably unstirred layers of water.     

In vitro generation of effector cells cytotoxic to autologous targets from chronic myeloid leukemia patients in remission

Summary Peripheral blood lymphocytes (PBL) from chronic myeloid leukemia (CML) patients in remission were stimulated in vitro, in a 3-cell assay with autologous leukemic cells or autologous bone marrow (BM) cells alone, or each in combination with allogeneic PBL. The responder cells were used as effectors in a 4-h ⁵¹Cr release cytotoxicity assay using autologous targets such as leukemic cells, BM cells, phytohemagglutinin-induced lymphoblasts, and allogeneic K562 (erythroblastoid leukemic cell line) target cells. Sensitization of lymphocytes from CML patients with either autologous leukemic cells or BM cells generated cytotoxic cells (CTCs) capable of killing both the targets. These results suggested that in CML, the PBL may have been sensitized to myeloid maturation-related antigens in vivo, which, on secondary stimulation in vitro, may result in differentiation of CTCs cytotoxic to immature myeloid cells, either from autologous leukemic cells or autologous BM. The inability of PBL from patients with oral cancers to lyse autologous BM cells upon in vitro stimulation, supported this possibility. Clonogenic assays conducted to assess the colony forming potential of BM cells which had interacted with CTCs indicated that there was about 37% reduction in committed granulocyte stem cell colony formation without an appreciable change in committed granulocyte/monocyte stem cell units and clusters. Therefore, since the BM toxicity of the CTCs is not very high, these cells may have a potential clinical use in CML.