Acute myeloid leukaemia expressing the leucocyte integrin CD11b-a new leukaemic syndrome with poor prognosis: result of an ECOG database analysis. Eastern Cooperative Oncology Group

Comprehensive analysis of clinical prognostic features and tumor microenvironment landscape of CD11b+CD64+ patients with acute myeloid leukemia

BACKGROUND

Immunophenotyping surface molecules detected in the clinic are mainly applied in diagnostic confirmation and subtyping. However, the immunomodulatory molecules CD11b and CD64, are highly associated with leukemogenesis. Hence, the prognostic value of them and their potential biological functions merit further investigation.

METHODS

Flow cytometry was operated to detect immunophenotypic molecules from AML bone marrow samples. Multivariate cox regression, Kaplan-Meier analyses, and nomogram were conducted to predict survival. Transcriptomic data, lymphocyte subsets, and immunohistochemical staining were incorporated to identify potential biological functions of prognostic immunophenotype in acute myeloid leukemia (AML).

RESULTS

We classified 315 newly diagnosed AML patients of our center based on the expression of CD11b and CD64. The CD11b+CD64+ populations were identified as independent risk factors for overall survival and event-free survival of AML, exhibiting specific clinicopathological features. The predictive models based on CD11b+CD64+ showed high classification performance. In addition, the CD11b+CD64+ subset, characterized by high inhibitory immune checkpoints, M2-macrophage infiltration, low anti-tumor effector cells infiltration, as well as abnormal somatic mutation landscape, presented a distinctive tumor microenvironmental landscape. The CD11b+CD64+ population showd a higher expression of BCL2, and the drug sensitivity indicated that they presented a lower half-maximal inhibitory concentration value for BCL2 inhibitor, and could benefit more from the above medicine.

CONCLUSIONS

This work might be of benefit to enhanced understanding of CD11b+CD64+ in the prognosis and leukemogenesis, and yielded novel biomarkers to guide immunotherapy and targeted therapy for AML.

Independent prognostic impact of CD15 on complete remission achievement in patients with acute myeloid leukemia

The prognostic role of CD15 in acute myeloid leukemia (AML) has been tested in different studies with conflicting results. To address this issue, we retrospectively evaluated a cohort of 460 AML patients of all ages with the exclusion of acute promyelocytic leukemia (M/F 243/217, median age 50.6 years [range 0.9-81.2]) intensively treated at our institute between January 1999 and December 2010. CD15 positivity was found in 171 of 406 evaluable patients (42.1%). Complete remission (CR) was achieved by 334 patients (72.6%), while 82 (17.8%) were resistant and 44 (9.6%) died during induction: the median CR duration was 15.5 months (range 0.6-176.0), with 2-year disease-free survival rate of 45.1% (95% confidence interval 39.6-50.6). The median overall survival was 14.4 months (range 0.3-177.0), with 2-year overall survival rate of 42.2% (95% confidence interval 37.5-46.9). At univariate analysis for CR achievement, age < 60 years (P < .001), World Health Organization classification (P = .045), low-risk karyotype (P < .001), no high-risk karyotype (P = .006), positivity for AML-ETO (P = .004)/CBFβ-MYH11 (P = .003)/CD15 (P = .006)/CD11b (P = .013), negativity for FLT3-ITD (P = .001), Hb > 8 g/dL (P = .020), and white blood cell < 50 × 10⁹ /L (P = .034) had a favorable impact. At a multivariate logistic regression model, CD15 positivity (P = .002), age < 60 years (P = .008), white blood cell < 50 × 10⁹ /L (P = .017), and low-risk/no high-risk karyotype (P = .026/P = .025) retained an independent prognostic role on CR achievement. The baseline assessment of CD15 positivity appears to have a role in the risk evaluation for CR achievement in AML patients undergoing intensive chemotherapy and should be assessed in prospective studies together with other clinical and biologic features already reported.

Erythropoietin protects the tubular basement membrane by promoting the bone marrow to release extracellular vesicles containing tPA-targeting miR-144

Renal fibrosis is an inevitable outcome of chronic kidney disease (CKD). Erythropoietin (EPO) has been recently reported to be able to mitigate renal fibrosis. The mechanism underlying the protective effect of EPO, however, remains elusive. In the present study, employing a mouse model of renal tubulointerstitial fibrosis induced by unilateral ureteral obstruction (UUO), we demonstrated that EPO markedly reduced the disruption of the tubular basement membrane (TBM) through attenuating the activation of tissue plasminogen activator (tPA) and matrix metalloproteinase 9 (MMP9), the major matrix proteolytic network in the obstructed kidney. Instead of acting directly on tPA in the kidney, EPO strongly increased the level of circulating microRNA (miR)-144, which was delivered to the injured renal fibroblasts via extracellular vesicles (EVs) to target the tPA 3′-untranslated region and suppress tPA expression. The protective effect of EPO on mouse TBM was inhibited by miR-144 antagomir. Furthermore, in vitro results confirmed that EPO could stimulate bone marrow-derived Sca-1+CD44+CD11b−CD19− cells to secrete miR-144-containing EVs, which markedly suppressed tPA expression, as well as metalloproteinase 9 (MMP9) level and activity, in cultured renal fibroblasts. In conclusion, our study provides the first evidence that EPO protects mouse renal TBM through promoting bone marrow cells to generate and secrete miR-144, which, in turn, is efficiently delivered into the mouse kidney via EVs to inhibit the activation of the tPA/MMP9-mediated proteolytic network. This finding thus suggests that EPO, a hormone widely used to treat anemia in CKD, is a potential therapeutic strategy for renal fibrosis.

Prognostic Value of CD11b Expression Level for Acute Myeloid Leukemia Patients: A Meta-Analysis

BACKGROUND

Study results on the prognostic value of CD11b for acute myeloid leukemia (AML) patients are inconsistent. An up-to-date meta-analysis was conducted to assess the prognostic value of CD11b expression level for AML patients.

METHODS

Electronic databases including PubMed, Embase, Cochrane Library, Web of Science and Chinese BioMedical Literature Database (CBM) were searched to identify studies that investigated the association between CD11b expression level and prognosis of AML patients. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for overall survival (OS) and disease-free survival (DFS) and pooled odds ratio (OR) with 95% CI for complete remission rate (CRR) were calculated using Revman 5.3 and Stata 11.0.

RESULTS

13 total studies with 2619 patients were included in this meta-analysis. Results of the meta-analysis showed that CD11b positivity was associated with lower CRR (OR = 0.44; 95% CI, 0.25-0.79; p = 0.006) and shorter OS (HR = 0.66; 95% CI, 0.55-0.80; p < 0.0001), but did not affect DFS (HR = 0.67; 95% CI, 0.31-1.48; p = 0.32). Subgroup analysis by ethnicity, cut-off value for CD11b positivity, treatment, subtype and sample preparation method showed no significant interaction between these factors with the prognostic value of CD11b expression level for AML patients. Sensitivity analysis yielded consistent results with the main meta-analysis.

CONCLUSION

CD11b positivity could predict a poor prognosis for AML patients. Thus, CD11b expression level might be considered a prognostic biomarker for AML patients.

Correlation of CD11b and CD56 expression in adult acute myeloid leukemia with cytogenetic risk groups and prognosis

Among other phenotypic markers, CD11b expression has been considered as an unfavorable prognostic factor, both in terms of overall survival (OS), disease-free survival (DFS), and attainment and duration of complete remissions (CRs) in adult patients with acute myeloid leukemia (AML). Recently, some groups have restricted its prognostic impact to poor prognostic karyotypic risk groups. The aim of this study was to retrospectively analyze the prevalence of CD11b and of CD56 expression in blast cells of 158 AML patients [excluding those with t(15;17)] stratified according to their cytogenetic risk and to correlate these phenotypic characteristics with OS, DFS, and CR. CD11b was more frequently expressed in intermediate and unfavorable cytogenetic prognostic groups (38.9 and 35.5 %, respectively) than in the favorable group (9.5 %). No differences were observed in CD56 expression according to the cytogenetic risk groups. When OS, DFS, and CR were analyzed according to these two markers, no statistical differences were recorded in any cytogenetic risk group. In conclusion, although CD11b was more frequently expressed in blast cells of patients with intermediate and unfavorable cytogenetic risk groups, this feature did not translate into different clinical outcome. Similarly, CD56 positivity did not have any influence on the prognosis of these patients.

Spontaneous cell fusion of acute leukemia cells and macrophages observed in cells with leukemic potential

Cell fusion plays a well-recognized physiological role during development, while its function during progression is still unclear. Here, we show that acute myeloid leukemia (AML) cells spontaneously fused with murine host cells in vivo. AML cells fused in most cases with mouse macrophages. Other targets of AML cell fusion were dendritic and endothelial cells. Cytogenetic and molecular analysis revealed that successive recipients conserved detectable amounts of parental DNA. Moreover, in a mouse AML1-ETO model where female AML1-ETO-leukemic cells, expressing CD45.2, were injected in congenic CD45.1 male mice AML cells, we found hybrid cells expressing both allelic types of CD45 and XXY set of sexual chromosomes. More importantly, the fusion protein AML1-ETO was transferred in the hybrid cells. When sorted hybrid cells were reinjected in a secondary recipient, they gave rise to leukemia with 100% penetrance and similar time of onset of leukemic cells. Our data indicate that in vivo fusion of cancer cells with host cells may be a mechanism of gene transfer for cancer dissemination and suggest that fused cells may be used to identify still unrecognized leukemogenic genes that are conserved in hybrid cells and able to perpetuate leukemia in vivo.

β2 integrin-derived signals induce cell survival and proliferation of AML blasts by activating a Syk/STAT signaling axis

Spleen tyrosine kinase (Syk) induces cell survival and proliferation in a high proportion of acute myeloid leukemia (AML) blasts, but the underlying molecular events of Syk signaling have not been investigated. Proteomic techniques have allowed us to identify the multiprotein complex that is nucleated by constitutively active Syk in AML cells. This complex differs from the B-lymphoid Syk interactome with respect to several proteins, especially the integrin receptor Mac-1, the Fc-γ receptor I (FcγRI), and the transcription factors STAT3 and STAT5. We show in several AML cell line models that tonic signals derived from the Fc-γ chain lead to Syk-dependent activation of STAT3 and STAT5, which in turn induces cell survival and proliferation. Moreover, stimulation of Mac-1 or FcγRI intensifies the constitutive Syk-mediated STAT3/5 activation in AML cells, a scenario likely to take place in the bone marrow niche. In accordance with these findings, we observed that β2 integrins, including Mac-1, trigger proliferation of AML cells in an AML cell/stroma coculture model. Taken together, we identified an oncogenic integrin/Syk/STAT3/5 signaling axis that might serve as a therapeutic target of AML in the future.

CD11b expression correlates with monosomal karyotype and predicts an extremely poor prognosis in cytogenetically unfavorable acute myeloid leukemia

Several cytogenetic features, including monosomal karyotype (MK), have been associated with unfavorable prognosis in acute myeloid leukemia (AML). However, little is known about the prognostic significance of immunophenotypes in AML patients with unfavorable-risk cytogenetics. We evaluated immunophenotypes, cytogenetics, clinical features and survival outcomes in 233 uniformly treated AML patients who harbored unfavorable cytogenetics. CD11b expression was observed in 145 (70%) of 208 patients and emerged as an independent prognostic factor for inferior overall survival in multivariate analysis (p=0.024). MK and age ≥ 60 years were predictors for lower complete remission rate (p=0.017, p<0.0001, respectively) and shorter overall survival (p=0.024, p<0.0001), while complex karyotype (CK) predicted a shorter overall survival (p=0.013). CD11b expression was strongly correlated with MK and identified a subset of patients with MK who had extremely poor overall survival. We proposed a prognostic scoring model using CD11b positivity, age ≥ 60 years, the presence of MK and the presence of CK to classify the patients into distinct risk groups. We identified the poor prognosis of CD11b expression and validated the adverse influence of MK, CK and age ≥ 60 years in cytogenetically unfavorable AML patients. Our proposed scoring model may be adapted in clinical practice to further the stratification of this high-risk population.

CD25 expression status improves prognostic risk classification in AML independent of established biomarkers: ECOG phase 3 trial, E1900

We determined the prognostic relevance of CD25 (IL-2 receptor-α) expression in 657 patients (≤ 60 years) with de novo acute myeloid leukemia (AML) treated in the Eastern Cooperative Oncology Group trial, E1900. We identified CD25(POS) myeloblasts in 87 patients (13%), of whom 92% had intermediate-risk cytogenetics. CD25 expression correlated with expression of stem cell antigen CD123. In multivariate analysis, controlled for prognostic baseline characteristics and daunorubicin dose, CD25(POS) patients had inferior complete remission rates (P = .0005) and overall survival (P < .0001) compared with CD25(NEG) cases. In a subset of 396 patients, we integrated CD25 expression with somatic mutation status to determine whether CD25 impacted outcome independent of prognostic mutations. CD25 was positively correlated with internal tandem duplications in FLT3 (FLT3-ITD), DNMT3A, and NPM1 mutations. The adverse prognostic impact of FLT3-ITD(POS) AML was restricted to CD25(POS) patients. CD25 expression improved AML prognostication independent of integrated, cytogenetic and mutational data, such that it reallocated 11% of patients with intermediate-risk disease to the unfavorable-risk group. Gene expression analysis revealed that CD25(POS) status correlated with the expression of previously reported leukemia stem cell signatures. We conclude that CD25(POS) status provides prognostic relevance in AML independent of known biomarkers and is correlated with stem cell gene-expression signatures associated with adverse outcome in AML.

Epigenetic regulation of cellular adhesion in cancer

Epigenetics describes the development and maintenance of stable heritable gene expression patterns, which allow cells to show different phenotypes despite of a commonly shared genetic code. The increasing knowledge in this field during the last decades reveals its importance for many physiological processes like differentiation, embryogenesis and parental imprinting, but also for some diseases such as cancer. Recent data have shown that the complexity of carcinogenesis can no longer be explained solely on the basis of genetic changes, but epigenomic alterations such as changes of the DNA methylation pattern and/or post-translational histone modifications and changes of microRNA expression need to be equally considered. Such epigenetic alterations may cause permanent changes in gene expression patterns and may therefore essentially contribute to some of the known phenotypic characteristics of cancer cells like the loss of growth control, altered intercellular communication and enhanced motility. The two latter may essentially be associated with the downregulation of cellular adhesion molecules, which may therefore be relevant in the context of cancer invasiveness and prognosis. The targeted modification of the epigenome may therefore open new horizons within the increasingly important field of epigenetic therapeutics-particularly in view of the regulation of cellular adhesion with particular attention to tumor cell invasion and metastasis.

Failure of three novel regimens to improve outcome for patients with relapsed or refractory acute myeloid leukaemia: a report from the Eastern Cooperative Oncology Group

The treatment of relapsed acute myeloid leukaemia (AML) remains unsatisfactory. We conducted a phase II randomized trial where patients received intermediate-dose cytarabine for 4 d followed by gemtuzumab ozogamicin on day 5 (Arm A), or combined with liposomal daunorubicin for 3 d (Arm B), or cytarabine given for 5 d combined with cyclophosphamide for 3 d and topotecan by continuous infusion for 5 d (Arm C). Eligible patients had primary refractory AML, a first relapse after a remission of <1 year, or a second or greater relapse. The primary objective of this trial was attainment of a conventional complete remission (CR) or a CR without platelet recovery (CRp) in at least 40% of patients. The CR/CRp rates for the 82 eligible patients were 3/26 (12%) in Arm A, 2/29 (7%) in Arm B, and 1/27 (4%) in Arm C. No patients who had relapsed within 6 months of initial CR or who had suffered multiple relapses responded. More than 95% of patients subsequently died of AML. No unexpected toxicities were encountered. We conclude that none of these three regimens were effective enough in the treatment of high-risk relapsed or refractory AML to warrant further study. This trial was registered at http://www.clinicaltrials.gov as #NCT00005962.

Antibodies to CD11b, CD68, and lectin label neutrophils rather than microglia in traumatic and ischemic brain lesions

Resident quiescent microglia have been thought to respond rapidly to various pathologic events in the brain by proliferating and producing many bioactive substances, including proinflammatory cytokines and nitric oxide (NO). In this study, we investigated the reaction of microglia in traumatic and ischemic lesions caused by stab wounds and the transient 90-min occlusion of middle cerebral artery in a mature rat brain. Although many Iba1(+) resident microglia underwent apoptotic degeneration in the lesion core within 24 hr after the onset of the brain insult as revealed by TUNEL staining, numerous small, round, isolectin B4(+)/CD11b(+)/CD68(+) cells were localized in the lesion core. These small, round cells with diameters of 7-9 mum and polymorph nuclei expressed neutrophil-specific elastase, alkaline phosphatase, and platelet-activating factor receptor. Accordingly, they were not activated microglia but neutrophils. Immunohistochemical staining with antibodies to inducible NO synthase (iNOS) showed that most iNOS(+) cells were neutrophils. The results from spatial and kinetic analyses using RT-PCR and immunoblotting were consistent with the immunohistochemical observations. These results suggest the necessity of reevaluating the traditional view on the roles of activated microglia in severe neuropathologic events. Note that the traditional microglial markers isolectin B4, CD11b, and CD68 are not specific for microglia, particularly in a pathologic brain.

Expression of MAC-1 (CD11b) in acute myeloid leukemia (AML) is associated with an unfavorable prognosis

There is evidence to suggest, that cellular adhesion molecules and receptors could play a role in leukemia, e.g., through altered adhesive qualities of leukemic blasts. We have studied the expression of the beta2-integrin Mac-1 (CD11b) on mononuclear cells in 48 patients with AML at first diagnosis by flow cytometry using a direct fluorescein-conjugated antibody. A case was defined as positive if more than 20% of the cells expressed Mac-1. Within the FAB types, we observed a high expression rate in cases with M5 (100% MAC-1+ cases, 73% MAC-1+ cells), M4 (75% MAC-1+ cases, 48% MAC-1+ cells) and in cases with FAB-M1 with 71% MAC-1+ cases and 29% MAC-1+ cells. Separating our patients' cohort in cytogenetic risk groups, we could detect significant higher proportions of MAC-1+, cases (88% vs. 27%, P = 0.005) and cells (51% vs. 16%, P = 0.015) with poor cytogenetic risk compared to the favorable risk group. For clinical evaluations only patients treated according to the protocols of the German AML Cooperative Group (AML-CG) were included (n = 29, cases with AML-M3 were excluded). More MAC-1+ cases and cells were found in the "non-responders" group (n = 8) compared to the "responders" group (n = 24). We can conclude that AML cases with high MAC-1 expression are characterized by a worse prognosis. Evaluation of MAC-1 expression in AML might therefore contribute clinically important data with respect to develop new therapies that influence the interactions between integrins like MAC-1 on leukemic cells and endothelial or immunoreactive cells.

A surrogate marker profile for PML/RAR alpha expressing acute promyelocytic leukemia and the association of immunophenotypic markers with morphologic and molecular subtypes

BACKGROUND

The availability of genotype-specific therapy for PML/RAR alpha(pos) acute promyelocytic leukemia (APL) requires that this disease be precisely diagnosed. Immunophenotypic characteristics heretofore proclaimed as reliably characterizing APL (HLA-DR(low), CD34(low), P-glycoprotein(low) myeloid phenotype) do not differentiate from APL-like immune profiles unassociated with the PML/RAR alpha fusion transcript.

METHODS

To establish a surrogate marker profile for APL, we explored 19 potentially predictive markers compared with differentiated acute myeloid leukemia using the classification tree approach with recursive partitioning.

RESULTS

In a test group of 58 APL patients, the most predictive immune profile was HLA-DR(low), CD11a(low) (alpha(L) subunit of the leukocyte integrin LFA-1), CD18(low) (beta(2) subunit of LFA-1). APL cells always expressed CD117 (c-kit) but lacked the progenitor antigen CD133 and the more mature myeloid antigen, CD11b (alpha(M) leukocyte integrin). This antigen pattern was validated in 90 additional APL patients. M3v APLs (n = 30) had more leukemic promyelocytes expressing the T-cell antigen, CD2 (P < 0.0001) or the stem cell marker, CD34 (P = 0.0003) and demonstrated higher fluorescence intensity for the binding of antibody to the common leukocyte antigen, CD45 (P = 0.0008) than M3 (n = 102). S-form APL (n = 45) had a higher percent of cells expressing CD2 or CD34 (P < 0.0001 for both) or the neural cell adhesion molecule CD56 (P = 0.001) than L-form APL (n = 66).

CONCLUSIONS

PML/RAR alpha(pos) APL cells typically lack leukocyte integrins. HLA-DR(low), CD11a(low), CD18(low) is a reliable surrogate antigen expression profile for PML/RAR alpha(pos) APL, irrespective of morphology and transcript isoform.

Acute Monocytic Leukemia (French-American-British classification M5) Does Not Have a Worse Prognosis Than Other Subtypes of Acute Myeloid Leukemia: A Report From the Eastern Cooperative Oncology Group

Purpose

Acute monocytic leukemia is a distinct subtype of acute myeloid leukemia (AML) with characteristic biologic and clinical features. This study was designed to compare the outcome of patients with M5 to that of other subtypes of AML, and to identify differences in M5a and M5b.

Patients and Methods

We reviewed all patients with AML M5 entered in three clinical trials for newly diagnosed AML conducted by the Eastern Cooperative Oncology Group between 1989 and 1998. Eighty-one patients, 21 with M5a and 60 with M5b, were identified.

Results

The complete remission rate was 62% for all patients with M5; 52% for patients with M5a and 65% for patients with M5b (P = .3), and 60% for the 1,122 patients with non-M5 AML entered on the same clinical trials (P = .8 for M5 v non-M5). The 3-year disease-free survival was 26% for all M5 patients; 18% for M5a and 28% for M5b (P = .31), and 33% for non-M5 patients (P = .13 for M5 v non-M5). The 3-year overall survival was 31% for all M5 patients; 33% for M5a and 30% for M5b (P = .65), and 30% for non-M5 (P = .74 for M5 v non-M5). The karyotypes of patients with AML M5 were heterogeneous. CD11b was the only leukemic cell antigen expressed differently in M5a (53%) compared to M5b (77%) to a significant degree (P = .02).

Conclusion

AML M5 represents an immunologically heterogeneous population similar to non-M5 AML with a prognosis that is not dependent on morphology. The disease-free survival and overall survival of patients with M5a, M5b, and non-M5 appear not to differ with currently available therapy.

The prognostic significance of antigen expression in leukaemia

Numerous immunophenotypic features have been examined for their potential prognostic significance in predicting treatment outcome in leukaemias. These include immunophenotypic subgroups of acute lymphoblastic leukaemia (ALL) and immature acute myeloid leukaemia, expression of individual surface antigens or combined immunophenotypic features, and more recently, molecules mediating the multidrug resistance phenotype or being involved in the regulation of drug-induced apoptosis. Most previous studies investigating the prognostic significance of antigen expression in leukaemia have not used the information provided by multiparameter flow cytometry and have chosen rather arbitrary cut-off points for marker positivity. Moreover, given significant associations between immunophenotypic features and genetic abnormalities in leukaemic cells, immunophenotyping as an independent predictor of treatment outcome has been questioned. Thus, except for lineage assignment of leukaemic blasts and definition of maturational status in ALL, information provided by immunophenotyping is currently not applied to risk-classification systems or used for planning patient treatment in leukaemia. We review some of the recent findings regarding the prognostic impact of distinct immunophenotypic features in acute leukaemias and myelodysplastic syndrome.

Comments on the 2001 WHO proposal for the classification of haematopoietic neoplasms

In the preface, the World Health Organization (WHO) classification vows to offer pathologists, oncologists and geneticists worldwide a system of classification for human neoplasms based on histopathological and genetic features. Standardization of nomenclature and agreed-upon criteria for definition of the various types of cancer are felt to be a prerequisite for progress in clinical oncology, multicentre therapy trials and comparative studies in different countries. In fact, the WHO effort represents the first worldwide comprehensive consensus classification of the haematological malignancies. Consensus was reached among a subgroup of investigators, carefully selected for their experience and contributions to existing classifications. In the present climate of daily new discoveries that yield a constant stream of fascinating insights into the biology of leukaemias and lymphomas and, above all, resulting in an explosion of potential therapeutic targets, the WHO system has taken the stand of compiling established classification approaches and providing order to known facts. This furnishes an essential skeleton upon which to build in the future. The WHO committee decided that sorting neoplasms according to prognosis was neither practical nor necessary and could be misleading. While justifiable at the present time, it is important to realize that the classifications of the haematological malignancies are a moving target and that the trend is to move away from currently accepted gold standards, such as morphological evaluations, in favour of genetic characterizations, especially those with therapeutic relevance. The goal of this chapter is to fill in some gaps that, as per the author's opinion, exist in the WHO classification, predominantly, where it concerns the role of immunophenotyping as a complementary discipline for genotyping through its potential to generate surrogate marker profiles for molecular lesions. By introducing some state-of-the-art classification modalities, some of which are still awaiting confirmation, this chapter also aims to spark excitement and provide a glimpse at the future.

The clinical significance of soluble CD86 levels in patients with acute myeloid leukemia and myelodysplastic syndrome

BACKGROUND

Levels of the soluble form of CD86 (sCD86) are elevated in a proportion of patients with leukemia. Although it is a potential modulator of antitumor responses, the significance of sCD86 in patients with hematologic malignancies is unknown.

METHODS

The authors evaluated sCD86 levels by enzyme-linked immunosorbent assay in patients with acute myeloid leukemia (AML) (n = 57 patients) and patients with myelodysplastic syndrome (MDS) (n = 40 patients) and analyzed the relation between sCD86 levels and various clinical parameters.

RESULTS

Levels of sCD86 were elevated (> 2.32 ng/mL) relative to normal donors (0.22-2.32 ng/mL; n = 51 patients) in 25% of patients with AML and in 27% of patients with MDS. Patients with AML who had elevated sCD86 levels had significantly lower complete remission (CR) rates compared with patients with AML who had normal sCD86 levels. In multivariate analysis using sCD86 as a continuous variable and including the interaction of age and sCD86 as a variable, sCD86 was a significant prognostic factor (P = 0.014) independent of cytogenetics. Further analysis demonstrated that, in patients with AML age 60 years and younger, but not in patients older than 60 years, elevated sCD86 levels were associated with significantly shorter survival (P = 0.04). There was no correlation between sCD86 levels and CR rates or survival in patients with MDS.

CONCLUSIONS

The presence in patients with AML of elevated levels of circulating sCD86 were associated with lower CR rates and poor survival. The prognostic significance of sCD86 was independent of cytogenetics but was modulated by age, in that it was independently significant only in younger patients. The results suggest that sCD86 may play a role in modulating immune responses associated with the progression of AML.

Low expression of the myeloid differentiation antigen CD65s, a feature of poorly differentiated AML in older adults: study of 711 patients enrolled in ECOG trials

CD65s appears when the progenitor antigen CD34 disappears, suggesting that this sialylated carbohydrate antigen marks a turning point in normal myeloid differentiation. We characterized acute myeloid leukemia (AML) with low CD65s expression (CD65s(low) AML) in 711 patients entered on seven Eastern Cooperative Oncology Group AML treatment trials (1986-1999). Of those, 198 (28%) qualified as having CD65s(low) AML. Morphologically, CD65s(low) AML was more common in FAB subgroups with minimal differentiation, M0/M1 (P=<0.0001). Early precursor antigens CD34, CD117 and terminal transferase were more frequent in CD65s(low) than CD65s(high) AML (P=<0.0001). Myeloperoxidase was present in fewer CD65s(low) myeloblasts, and the more mature myeloid antigens, CD15 and CD11b, were rarely detected (P=<0.0001). Yet, the two diagnoses did not differ in the distribution of cytogenetic prognostic groups or the occurrence of the multidrug-resistance mediator, P-glycoprotein. CD65s(low) AML patients were significantly older than CD65s(high) cases (P<0.0001). Furthermore, the incidence of CD65s(low) cases increased with age, from 20% in patients under the age of 50 years to 67% in patients older than 80 years (P<0.0001). Overall, complete remission (CR) rate and overall survival were comparable in CD65s(low) and CD65s(high) AML. However, among patients >55 years of age, CD65s(low) AML had a decreased CR rate of 33 vs 44% in CD65s(high) AML (P=0.055). Thus, CD65s(low) AML represents immunophenotypically undifferentiated disease and occurs predominantly in older adults. Although not statistically significant, the observed association between low CD65s expression and decreased CR rate only in patients over the age of 55 is intriguing.

Immunophenotyping is an independent factor for risk stratification in AML

BACKGROUND

Chromosomal abnormalities are one of the most important prognostic factors in acute myeloid leukemia (AML). However, only a limited number of patients have such informative chromosomal abnormalities. The prognostic value of immunophenotyping in this disease is still unclear.

METHODS

Seven hundred and eighty-three newly diagnosed AML patients treated in the German SHG-AML trials in 1991 and 1996 were analyzed with a panel of 33 antibodies. Expression was correlated to overall survival, complete remission-rate, and complete remission duration, and tested in a multivariate analysis including other clinical and biological markers.

RESULTS

With a median follow-up of 4.3 years, patients with AML blasts negative for CD9, CD11b, CD13, CD34, and CD41, or positive for CD15, CD33, CD38, CD64, and MPO had superior overall survival. This effect was associated with a significantly higher complete remission rate (CD13, CD34, CD41, and CD64) or a longer complete remission duration (CD9, CD11b, and CD64). Cox-regression analysis, including cytogenetic, morphologic, and biologic parameters showed CD9, CD13, CD34, and CD64 as independent factors for overall survival. These markers were used for a prognostic score. Patients were pooled in three groups with highly significant differences of overall survival. The prognostic relevance of this score was confirmed in patients with normal karyotype and/or in younger patients </= 60 years.

CONCLUSIONS

Immunophenotyping is not only helpful for diagnosis but is of independent significance for prognosis, and may be useful for risk stratification in AML patients.

Expression of CD117 and CD11b in bone marrow can differentiate acute promyelocytic leukemia from recovering benign myeloid proliferation

The morphologic characteristics of bone marrow aspirates from patients recovering from acute agranulocytosis may be closely similar to the pattern observed in cases of acute promyelocytic leukemia (APL). The clinical manifestation also can be ambiguous in a substantial number of cases. The immunophenotypic features of bone marrow from 5 patients recovering from acute agranulocytosis, showing an increase in the percentage of promyelocytes (26%-66%), were compared with the immunophenotype of 31 consecutive patients with APL whose diagnosis was confirmed by PML-RAR alpha gene rearrangement. All markers were similarly expressed, except for CD117 and CD11b. CD117 was positive in 24 (77%) of the APL cases and in none of the acute agranulocytosis cases. On the other hand, CD11b was positive in 5 (100%) of the acute agranulocytosis cases and in only 2 (6%) of the APL cases. Thus, the CD117-CD11b+ phenotype was detected in all patients recovering from agranulocytosis and in only 1 (3%) of 31 APL cases. Therefore, we suggest that the combination of both markers is helpful in the differentiation of APL from recovering benign myeloid proliferation.

Differential response to stem cell factor and Flt3 ligand by the FAB subtype in acute myeloid leukemia clonogenic cells

Proliferative response of blast clonogenic cells to various hematopoietic growth factors (HGF), including stem cell factor (SCF) and flt3 ligand (FL) was investigated in 100 patients with acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML) in myeloid crisis (MC). The frequency of spontaneous colony formation was significantly high in CML in MC (55%) and AML French-American-British (FAB) subtype M4 (48%) compared with M2 (16%). No spontaneous colony was formed in any of the patients with M1 and M3. The frequency of proliferative response to various HGF alone and in combination according to FAB subtype and CML in MC was as follows: that to granulocyte colony-stimulating factor (G-CSF) was lowest in M1 and CML in MC (50%) compared with other FAB subtypes (>or=86%), that to granulocyte-macrophage CSF (GM-CSF) was lowest in CML in MC (44%) compared with FAB subtypes (>or=74%), and that to interleukin-3 (IL-3) was lowest in CML in MC (30%) compared with FAB subtypes (>or=78%). SCF and FL stimulated blast colony formation in 11% and 17% of patients with M3, respectively, but there was no response to both, and in 60% and 57% of patients with CML in MC, respectively, with 14% showing a response to both. The frequency of proliferative response to both SCF and FL increased in the order of M1 (33%), M2 (63%), M4-5 (95%), and M6 (100%). The results are summarized as follows: absence of spontaneous colony formation and response to HGF other than SCF and FL, designated as HGF-dependent growth (M3); spontaneous colony formation and lowest response to HGF, designated as autonomous growth (CML in MC); and spontaneous colony formation and highest response to HGF including SCF and FL, designated as autocrine growth (M4-6). M1 and M2 were intermediate between CML in MC and M4-6. The relation between in vitro growth pattern of blast clonogenic cells and prognosis in AML FAB subtype and CML in MC is discussed.

Expression of co-stimulatory and adhesion molecules and chemokine or apoptosis receptors on acute myeloid leukaemia: high CD40 and CD11a expression correlates with poor prognosis

The expression of adhesion and co-stimulatory molecules, and chemokine and death receptors such as tumour necrosis factor (TNF) and FAS on acute myeloid leukaemia (AML) may influence the biology of the disease and response to chemotherapy and immunotherapy. In this study, we analysed the expression of these molecules in 99 AML patients using monoclonal antibodies and flow cytometry, and correlated the expression with French-American-British (FAB) classification and survival. The following molecules were studied: the co-stimulatory molecules CD80, CD86 and CD40; the adhesion molecules CD11a-c, CD31, CD43, CD50, CD54, CD102, CD58 and CD62L; the chemokine receptor CXCR4; and the death receptors TNFR1 and TNFR2 and FAS. The expression of all molecules was significantly higher in the M4/M5 FAB subgroups except for CD80, CD43, CD54 and CD62L. The AML M3 subgroup had a significant lower expression of CD11a (P = 0.02) and CD11c (P = 0.03). Five-year survival was significantly shorter in cases of high CD40 expression [> 20% positive cells, relative risk (RR) 2.56, P = 0.02] or high CD11a expression (> 80% positive cells, RR 2.6, P = 0.03). This effect was most prominently present in the AML M4/M5 FAB subgroups. We conclude that the expression levels of adhesion and co-stimulatory molecules, CXCR4 and apoptosis-receptors are predominantly FAB subtype-related with high CD40 and CD11a expression as poor prognostic factors.

Significant association between expression of the CD11b surface molecule and favorable outcome for patients with acute myeloblastic leukemia

The expression of several myeloid and non-lineage associated surface antigens in 70 patients with acute myeloblastic leukemia was investigated in relation to patient and disease characteristics, response to therapy, and prognosis. A leukocyte integrin, CD11b, was the only antigen that showed a significant association with complete remission (CR) duration and survival (P < .025). The mean survival for CD11b+ patients was longer than for CD11b- patients (578 +/- 76 versus 397 +/- 7 days, respectively). CR duration was 897 +/- 84 for CD11b+ patients and 366 +/- 71 for CD11b- patients. Multivariate analysis confirmed the predictive value of CD11b expression for longer survival (relative risk, 3.2; P = .02) and CR duration (relative risk, 3.2; P = .03). CR rate was also significantly higher in CD11b+ patients (77.3%) than in CD11b- patients (46.1%) (P = .01). Survival and remission duration were not influenced by expression of other surface markers including CD13, CD14, CD33, CD34, CD71, CD38, and HLA-DR or by other variables including French-American-British subtype, age, and leukocyte count. Extramedullary disease (EXD) was associated with the presence of both CD13 and CD14 expression (P < .04) but occurred less frequently in CD13+ cases. CD13 expression occurred more frequently in female patients (P = .03). CD38 expression was associated with lower platelet count and an increase in the number of blasts (P < .02).

Is myelodysplastic related acute myelogenous leukemia a distinct entity from de novo acute myelogenous leukemia? Potential for targeted therapies

Acute myelogenous leukemia (AML) can be separated by whether the presentation was proceeded by a myelodysplastic (MDS related AML) or developed de novo (dAML). Clinically, MDS related AML (mAML) has been considered to have a worse prognosis that dAML. The objective of this literature review was to identify unique biologic features of mAML. Compared to dAML, mAML is characterized by an altered immunophenotype (increased frequency of CD34, CD11b and CD25), lack of leukemic progenitor cell suppression due to TGFbeta1, increased bcl-2 expression, presence of inducible nitric oxide synthase, lower levels or mrp transcripts and increased expression of p53. Possible interpretations of these differences between mAML and dAML are presented. Implications for mAML directed therapy are discussed.

Endothelial cell activation by myeloblasts: molecular mechanisms of leukostasis and leukemic cell dissemination

Leukostasis and tissue infiltration by leukemic cells are poorly understood life-threatening complications of acute leukemia. This study has tested the hypothesis that adhesion receptors and cytokines secreted by blast cells play central roles in these reactions. Immunophenotypic studies showed that acute myeloid leukemia (AML) cells (n = 78) of the M0 to M5 subtypes of the French-American-British Cooperative Group expressed various amounts of adhesion receptors, including CD11a, b, c/CD18, CD49d, e, f/CD29, CD54, sCD15, and L-selectin. The presence of functional adhesion receptors was evaluated using a nonstatic adhesion assay. The number of blast cells attached to unactivated endothelium increased by 7 to 31 times after a 6-hour exposure of endothelium to tumor necrosis factor (TNF)-alpha. Inhibition studies showed that multiple adhesion receptors--including L-selectin, E-selectin, VCAM-1, and CD11/CD18--were involved in blast cell adhesion to TNF-alpha-activated endothelium. Leukemic cells were then cocultured at 37 degrees C on unactivated endothelial cell monolayers for time periods up to 24 hours. A time-dependent increase in the number of blasts attached to the endothelium and a concomitant induction of ICAM-1, VCAM-1, and E-selectin were observed. Additional experiments revealed that endothelial cell activation by leukemic myeloblasts was caused by cytokine secretion by blast cells, in particular TNF-alpha and IL-1 beta, and direct contacts between adhesion receptors expressed by blast cells and endothelial cells. Thus, leukemic cells have the ability to generate conditions that promote their own adhesion to vascular endothelium, a property that may have important implications for the pathophysiology of leukostasis and tissue infiltration by leukemic blast cells. (Blood. 2001;97:2121-2129)

Rare adult acute lymphocytic leukemia with CD56 expression in the ECOG experience shows unexpected phenotypic and genotypic heterogeneity

Expression of CD56, a marker of natural killer (NK) cells, in acute lymphocytic leukemia (ALL) is rare and, to date, has been described only in non-B lineage ALL. Among 194 patients with CD56 analysis on the ongoing Eastern Cooperative Oncology Group (ECOG) ALL trial, E2993, 6 cases of CD56+ ALL were found (3.1%) with a median of 95% of blast cells expressing CD56, compared with a median of 1% of blast cells in CD56- ALL (P = 0.0001). FAB-L2 characteristics dominated, without granulation. Blast cells from four CD56+ patients expressed T-cell antigens at variable levels of maturation. A clonal rearrangement of the T-cell receptor beta (TCRbeta) gene was detected only in one patient. TCRbeta variable gene usage studies in this and one other CD56+ ALL patient demonstrated a significantly perturbed usage pattern in both patients when compared with control lymphocytes. The two remaining cases typed as early pre-B ALL (CD19+, CD10+), with one case co-expressing CD7. Cytogenetically, 4 patients were normal, 1 complex abnormal, and 1 Philadelphia chromosome positive. Epstein-Barr virus (EBV) sequences were detected in one T- and both B-lymphoid cases. Our data suggest that CD56 is expressed at a precursor stage common to the T- and the B-cell lineage.

Adhesion molecule expression, clinical features and therapy outcome in childhood acute lymphoblastic leukemia

In view of the relevance of adhesion molecule expression for the mechanisms of homing, trafficking and spreading of malignant cells, we have investigated the expression of surface adhesion molecules in lymphoblasts from 57 acute lymphoblastic leukemia (ALL) cases and tried to correlate the adhesive phenotype with immunological typing, prognostic factors at diagnosis and clinical follow-up. Blasts from all cases expressed adhesion molecules at high rates. Beta1 integrin chain (CD18) was consistently found on blasts from most ALL cases: among integrins of the beta2 family. LFA-1 was detected in 58% of cases, in the virtual absence of other alpha chains. CD54 and CD58 were expressed in variable proportions by ALL blasts and CD44 was detected in the majority of the malignant cells, whereas the CD62L selectin was only present in 24% of cases. B-lineage ALL's displayed similar adhesion molecule phenotypes irrespective of maturational stages of the leukemic cells. We found a significantly reduced expression of beta2 alphaL integrins in the hybrid ALL cases (CD13 and/or CD33 positive). However, these cases did not show differences in clinical presentation and behaviour in comparison with patients of other groups. We did not find a significant correlation between adhesion molecule expression and well established risk factors (age, white blood cell count, central nervous system involvement, chromosomal abnormalities), with the exception of splenomegaly, that was significantly associated with CD18 expression. In the follow-up, no evidence of significant correlation between adhesive phenotype and adverse events such as leukemic relapse and death was found. In conclusion, although expression of adhesion molecules on lymphoblasts confirms the phenotypic heterogeneity of ALL, it appears that this is not relevant for the clinical aspects of the disease and for prognosis.

Immunophenotyping of leukemia

Modern immunophenotyping of hematological malignancies by flow cytometry is assisted by a wide array of easily accessible monoclonal antibodies, by antibodies conjugated to diverse fluorochromes, and by reliable techniques for cell membrane permeabilization. Simultaneous assessment of multiple surface and intracellular markers at diagnosis reduces the number of cells required, helps the identification of the malignant cells and determines the degree of immunophenotypic heterogeneity of the malignant cell population. A few critical markers are sufficient to establish the lineage association in the majority of cases of acute and chronic leukemias and lymphomas. More extensive immunophenotyping can provide information about the cells' stage of differentiation, assess the expression of prognostically important features, and determine clonality. The identification of leukemia-associated immunophenotypes can be used for monitoring minimal residual disease during therapy. The presence of cells expressing these phenotypes in patients who are in clinical remission is associated with an increased risk of relapse.

The use of flow cytometry in the diagnosis and monitoring of malignant hematological disorders

Flow cytometry is a modality with ever increasing application in modern hematological practice. This is due to the rapidity of obtaining results, ease of use and increasing power to detect abnormal populations of cells. The major uses of flow cytometry in malignant hematology are in the diagnosis, classification and monitoring of diseases such as leukemia, lymphoma and myeloma. The technique is now used also to detect disease-specific populations of cells in paroxysmal nocturnal hemoglobinuria. This review describes the use of flow cytometry in many disease states.

Adult de novo acute myeloid leukemias with MLL rearrangements

MLL gene rearrangements identify a subgroup of acute leukemias with a bad prognosis. Fifty-one adult patients with de novo AML were screened for MLL rearrangements by Southern blot. An unexpected high frequency of AML-M2 according to the FAB classification was found. The most striking morphologic features of these cases were the scarcity of Auer rods and granulocytic dysplasia. Morphologic traits could be helpful in distinguishing molecular groups of AML-M2.

Treatment of Refractory and Relapsed Acute Myelogenous Leukemia With Combination Chemotherapy Plus the Multidrug Resistance Modulator PSC 833 (Valspodar)

A potential mechanism of chemotherapy resistance in acute myeloid leukemia (AML) is the multidrug resistance (MDR-1) gene product P-glycoprotein (P-gp), which is often overexpressed in myeloblasts from refractory or relapsed AML. In a multicenter phase II clinical trial, 37 patients with these poor risk forms of AML were treated with PSC 833 (Valspodar; Novartis Pharmaceutical Corporation, East Hanover, NJ), a potent inhibitor of the MDR-1 efflux pump, plus mitoxantrone, etoposide, and cytarabine (PSC-MEC). Pharmacokinetic (PK) interactions of etoposide and mitoxantrone with PSC were anticipated, measured in comparison with historical controls without PSC, and showed a 57% decrease in etoposide clearance (P = .001) and a 1.8-fold longer beta half-life for mitoxantrone in plasma (P < .05). The doses of mitoxantrone and etoposide were substantially reduced to compensate for these interactions and clinical toxicity and in Cohort II were well tolerated at dose levels of 4 mg/m2mitoxantrone, 40 mg/m2 etoposide, and 1 g/m2 C daily for 5 days. Overall, postchemotherapy marrow hypoplasia was achieved in 33 patients. Twelve patients (32%) achieved complete remission, four achieved partial remission, and 21 failed therapy. The PK observations correlated with enhanced toxicity. The probability of an infectious early death was 36% (4 of 11) in patients with high PK parameters for either drug versus 5% (1 of 20) in those with lower PK parameters (P = .04). P-gp function was assessed in 19 patients using rhodamine-123 efflux and its inhibition by PSC. The median percentage of blasts expressing P-gp was increased (49%) for leukemic cells with PSC-inhibitable rhodamine efflux compared with 17% in cases lacking PSC-inhibitable efflux (P = .004). PSC-MEC was relatively well tolerated in these patients with poor-risk AML, and had encouraging antileukemic effects. The Eastern Cooperative Oncology Group is currently testing this regimen versus standard MEC chemotherapy in a phase III trial, E2995, in a similar patient population.

Treatment of Refractory and Relapsed Acute Myelogenous Leukemia With Combination Chemotherapy Plus the Multidrug Resistance Modulator PSC 833 (Valspodar)

A potential mechanism of chemotherapy resistance in acute myeloid leukemia (AML) is the multidrug resistance (MDR-1) gene product P-glycoprotein (P-gp), which is often overexpressed in myeloblasts from refractory or relapsed AML. In a multicenter phase II clinical trial, 37 patients with these poor risk forms of AML were treated with PSC 833 (Valspodar; Novartis Pharmaceutical Corporation, East Hanover, NJ), a potent inhibitor of the MDR-1 efflux pump, plus mitoxantrone, etoposide, and cytarabine (PSC-MEC). Pharmacokinetic (PK) interactions of etoposide and mitoxantrone with PSC were anticipated, measured in comparison with historical controls without PSC, and showed a 57% decrease in etoposide clearance (P = .001) and a 1.8-fold longer beta half-life for mitoxantrone in plasma (P &lt; .05). The doses of mitoxantrone and etoposide were substantially reduced to compensate for these interactions and clinical toxicity and in Cohort II were well tolerated at dose levels of 4 mg/m2mitoxantrone, 40 mg/m2 etoposide, and 1 g/m2 C daily for 5 days. Overall, postchemotherapy marrow hypoplasia was achieved in 33 patients. Twelve patients (32%) achieved complete remission, four achieved partial remission, and 21 failed therapy. The PK observations correlated with enhanced toxicity. The probability of an infectious early death was 36% (4 of 11) in patients with high PK parameters for either drug versus 5% (1 of 20) in those with lower PK parameters (P = .04). P-gp function was assessed in 19 patients using rhodamine-123 efflux and its inhibition by PSC. The median percentage of blasts expressing P-gp was increased (49%) for leukemic cells with PSC-inhibitable rhodamine efflux compared with 17% in cases lacking PSC-inhibitable efflux (P = .004). PSC-MEC was relatively well tolerated in these patients with poor-risk AML, and had encouraging antileukemic effects. The Eastern Cooperative Oncology Group is currently testing this regimen versus standard MEC chemotherapy in a phase III trial, E2995, in a similar patient population.