The Pattern of Use of PET/CT Scans in the Clinical Management of Chronic Lymphocytic Leukemia.

BACKGROUND: The study aimed to evaluate the utilization patterns of positron emission tomography/computed tomography (PET/CT) in chronic lymphocytic leukemia (CLL) patients and to investigate whether the results of these scans influenced treatment decisions. PATIENTS: and Methods: In this observational study, we analyzed patients with CLL or small lymphocytic leukemia (SLL) who underwent at least one PET/CT scan from 2007 to 2018. Patients were divided into two groups: (1) patients who had at least one fluorodeoxyglucose-avid PET/CT scan, and (2) patients who had all negative scans. PET/CT results were retrieved from patients' medical files and were revised by an expert radiologist according to visual score scale, SUVmax/SUVliver mean ratio, and the SUVmax. RESULTS: Of the 524 patients, 160 patients (30.5%) had PET/CT scans, and 120 patients met the inclusion criteria. A total of 219 eligible scans were analyzed; 62 of these scans (28.3%) were reported as positive, and 167 of these scans (76.3%) were performed for staging. There was a significant association between PET/CT results and change of therapy (P < .001); however, 62.9% of the positive PET/CT scans were not followed by a change of treatment. Survival time was not different between the two groups. The SUVmax/SUVliver mean ratio was negatively significantly associated with lymphocytes percent (r = -0.237, P = .042) and positively associated with lactate dehydrogenase levels (r = 0.338, P = .008) among CLL patients. CONCLUSION: Despite the fact that the use of surveillance PET/CT for patients with CLL/SLL is not in the guidelines and that it is not useful for disease management, in practice the test is in frequent use in Israel.

Dasatinib response in acute myeloid leukemia is correlated with FLT3/ITD, PTPN11 mutations and a unique gene expression signature.

Novel targeted therapies demonstrate improved survival in specific subgroups (defined by genetic variants) of acute myeloid leukemia (AML) patients, validating the paradigm of molecularly targeted therapy. However, identifying correlations between AML molecular attributes and effective therapies is challenging. Recent advances in high-throughput in vitro drug sensitivity screening applied to primary AML blasts were used to uncover such correlations; however, these methods cannot predict the response of leukemic stem cells (LSCs). Our study aimed to predict in vitro response to targeted therapies, based on molecular markers, with subsequent validation in LSCs. We performed ex vivo sensitivity screening to 46 drugs on 29 primary AML samples at diagnosis or relapse. Using unsupervised hierarchical clustering analysis we identified group with sensitivity to several tyrosine kinase inhibitors (TKIs), including the multi-TKI, dasatinib, and searched for correlations between dasatinib response, exome sequencing and gene expression from our dataset and from the Beat AML dataset. Unsupervised hierarchical clustering analysis of gene expression resulted in clustering of dasatinib responders and non-responders. In vitro response to dasatinib could be predicted based on gene expression (AUC=0.78). Furthermore, mutations in FLT3/ITD and PTPN11 were enriched in the dasatinib sensitive samples as opposed to mutations in TP53 which were enriched in resistant samples. Based on these results, we selected FLT3/ITD AML samples and injected them to NSG-SGM3 mice. Our results demonstrate that in a subgroup of FLT3/ITD AML (4 out of 9) dasatinib significantly inhibits LSC engraftment. In summary we show that dasatinib has an anti-leukemic effect both on bulk blasts and, more importantly, LSCs from a subset of AML patients that can be identified based on mutational and expression profiles. Our data provide a rational basis for clinical trials of dasatinib in a molecularly selected subset of AML patients.

BST-236, a novel cytarabine prodrug for patients with acute leukemia unfit for standard induction: a phase 1/2a study.

High-dose cytarabine is the backbone of acute myeloid leukemia (AML) treatment. Nevertheless, its use in older patients is considerably limited due to increased toxicity. BST-236 (INN aspacytarabine) is a novel cytarabine prodrug designed to deliver high-dose cytarabine to target cells with reduced systemic exposure to free cytarabine. This phase 1/2a dose-escalation study was designed to evaluate BST-236 safety, pharmacokinetics, and efficacy in older or unfit-for-intensive-therapy patients with acute leukemia. Twenty-six patients, unfit for standard therapy, who were either relapsed/refractory or newly diagnosed, received BST-236 in 6 dose-escalating cohorts (range 0.3 to 6 g/m2 per day). BST-236 was administered intravenously once daily over 60 minutes for 6 consecutive days. The median age was 76.5 (26 to 90), with 84.6% of patients ≥70 years. BST-236 was safe and well tolerated. The maximal tolerated dose was 6 g/m2 per day. Overall response rate was 29.6%. A subgroup analysis of newly diagnosed patients with AML, de novo or secondary to myelodysplastic syndrome, unfit for standard induction (median age 78), demonstrated overall response of 45.5%. The median overall survival was 6.5 months and was not reached in patients achieving complete remission. The findings of this phase 1/2 study suggest that BST-236 safely delivers high and efficacious cytarabine doses to older patients who are unfit for standard induction and lays the foundation for further studies of BST-236 in AML. This trial was registered at www.clinicaltrials.gov as #NCT02544438.

Loss of the histone methyltransferase EZH2 induces resistance to multiple drugs in acute myeloid leukemia.

In acute myeloid leukemia (AML), therapy resistance frequently occurs, leading to high mortality among patients. However, the mechanisms that render leukemic cells drug resistant remain largely undefined. Here, we identified loss of the histone methyltransferase EZH2 and subsequent reduction of histone H3K27 trimethylation as a novel pathway of acquired resistance to tyrosine kinase inhibitors (TKIs) and cytotoxic drugs in AML. Low EZH2 protein levels correlated with poor prognosis in AML patients. Suppression of EZH2 protein expression induced chemoresistance of AML cell lines and primary cells in vitro and in vivo. Low EZH2 levels resulted in derepression of HOX genes, and knockdown of HOXB7 and HOXA9 in the resistant cells was sufficient to improve sensitivity to TKIs and cytotoxic drugs. The endogenous loss of EZH2 expression in resistant cells and primary blasts from a subset of relapsed AML patients resulted from enhanced CDK1-dependent phosphorylation of EZH2 at Thr487. This interaction was stabilized by heat shock protein 90 (HSP90) and followed by proteasomal degradation of EZH2 in drug-resistant cells. Accordingly, inhibitors of HSP90, CDK1 and the proteasome prevented EZH2 degradation, decreased HOX gene expression and restored drug sensitivity. Finally, patients with reduced EZH2 levels at progression to standard therapy responded to the combination of bortezomib and cytarabine, concomitant with the re-establishment of EZH2 expression and blast clearance. These data suggest restoration of EZH2 protein as a viable approach to overcome treatment resistance in this AML patient population.

The ability to cross the blood-cerebrospinal fluid barrier is a generic property of acute lymphoblastic leukemia blasts.

Prevention of central nervous system (CNS) relapse is critical for cure of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Despite this, mechanisms of CNS infiltration are poorly understood, and the timing, frequency, and properties of BCP-ALL blasts entering the CNS compartment are unknown. We investigated the CNS-engrafting potential of BCP-ALL cells xenotransplanted into immunodeficient NOD.Cg- ITALIC! Prkdc (ITALIC! scid) ITALIC! Il2rg (ITALIC! tm1Wjl)/SzJ mice. CNS engraftment was seen in 23 of 29 diagnostic samples (79%): 2 of 2 from patients with overt CNS disease and 21 of 27 from patients thought to be CNS negative by diagnostic lumbar puncture. Histologic findings mimic human pathology and demonstrate that leukemic cells transit the blood-cerebrospinal fluid barrier situated close to the dural sinuses, the site of recently discovered CNS lymphatics. Retrieval of blasts from the CNS showed no evidence for chemokine receptor-mediated selective trafficking. The high frequency of infiltration and lack of selective trafficking led us to postulate that CNS tropism is a generic property of leukemic cells. To test this, we performed serial dilution experiments which showed CNS engraftment in 5 of 6 mice after transplant of as few as 10 leukemic cells. Clonal tracking techniques confirmed the polyclonal nature of CNS-infiltrating cells, with multiple clones engrafting in both the CNS and periphery. Overall, these findings suggest that subclinical seeding of the CNS is likely to be present in most BCP-ALL patients at original diagnosis, and efforts to prevent CNS relapse should concentrate on effective eradication of disease from this site rather than targeting entry mechanisms.

Ruxolitinib treatment for myelofibrosis: Efficacy and tolerability in routine practice.

Ruxolitinib has been shown in two randomized clinical trials to be effective in alleviating systemic symptoms and reducing spleen size in patients with myelofibrosis (MF). We retrospectively evaluated efficacy and tolerability of ruxolitinib in a cohort of unselected MF patients treated in routine clinical practice. One hundred and two patients who began ruxolitinib therapy were identified in 13 participating centers. Ninety three of the patients receiving ruxolitinib for at least 3 months were evaluated for treatment efficacy and toxicity. Median age at ruxolitinib initiation was 67 years. Indications for treatment were constitutional symptoms (15%), symptomatic splenomegaly (6%) or both (76%). Two patients received ruxolitinib for other indications. The median initial ruxolitinib dose was 30mg/day. Median duration of therapy was 11 months. Eighty two patients (88.2%) responded to therapy, 76 (84.4%) patients had improvement in constitutional symptoms and 60 patients (70.6%) had reduction in spleen length. While on ruxolitinib, 30% of patients had grade 3-4 anemia and 12.9% of patients had grade 3-4 thrombocytopenia. Thirteen patients (14%) discontinued therapy. This analysis of a cohort of MF patients treated with ruxolitinib in routine clinical practice demonstrates the efficacy and tolerability of this drug outside of a highly monitored clinical trial setting.

Role of CXCR4 in the pathogenesis of acute myeloid leukemia.

The Chemokine receptor CXCR4 and its ligand stromal derived factor-1 (SDF-1/CXCL12) are important players involved in cross-talk between leukemia cells and the bone marrow (BM) microenvironment. CXCR4 expression is associated with poor prognosis in AML patients with and without the mutated FLT3 gene.CXCL12 which is constrictively secreted from the BM stroma and AML cells is critical for the survival and retention of AML cells within the BM. In vitro, CXCR4 antagonists were shown to inhibit the migration of AML cells in response to CXCL12. In addition, such antagonists were shown to inhibit the survival and colony forming potential of AML cells and abrogate the protective effects of stromal cells on chemotherapy-induced apoptosis in AML cells. In vivo, using immune deficient mouse models, CXCR4 antagonists were found to induce the mobilization of AML cells and progenitor cells into the circulation and enhance anti leukemic effects of chemotherapy. The hypothesis that CXCL12/CXCR4 interactions contribute to the resistance of AML cells to signal transduction inhibitor- and chemotherapy-induced apoptosis is currently being tested in a series of Phase I/II studies in humans.

High response rate for treatment with gemtuzumab ozogamicin and cytarabine in elderly patients with acute myeloid leukemia and favorable and intermediate-I cytogenetic risk.

UNLABELLED: Recent studies have reevaluated whether gemtuzumab ozogamicin (GO) improves the outcome of acute myeloid leukemia (AML) in elderly patients. Over 5 years, we treated 16 elderly patients with AML with GO and cytarabine. A high response rate, prolonged survival, and low toxicity were observed in the favorable and intermediate-I genetic groups of AML. Our study raises the issue about the optimal protocol for these patients. BACKGROUND: The benefit of gemtuzumab ozogamicin (GO) in combination with chemotherapy as frontline therapy in patients with acute myeloid leukemia (AML) is still debated. PATIENTS AND METHODS: We evaluated the safety and efficacy of low-dose GO with cytarabine in elderly patients with newly diagnosed AML. Over the past 5 years, we have treated 16 elderly patients with AML (64-82 years) with GO (3 mg/m(2)) followed by continuous infusion of cytarabine (100 mg/m(2)) for 7 days. RESULTS: Complete remission (CR) was achieved in 68.8% of patients; however, this was true only in patients in the favorable or intermediate-I cytogenetic risk groups. Of the 12 patients with AML in the favorable and intermediate-I genetic groups, 11 (91.7%) achieved CR. By comparison, of all 4 patients in the intermediate-II or adverse genetic groups, none of the patients achieved CR (P = .003). The median disease-free survival and overall survival (OS) was 10.9 and 18.8 months, respectively, for patients who achieved CR. The estimated median survival was 15 months in the favorable and intermediate-I cytogenetic groups and only 4.4 months in the intermediate-II and unfavorable risk groups (P = .008). The toxicity profile was also manageable in patients with AML who were mainly older than 70 years with good performance status (PS). The 8-week mortality rate was 6.25%, which is relatively low in this high-risk group of patients. These data are in line with results from 2 randomized trials suggesting that the addition of low-dose GO should be further investigated to reevaluate its role in selected elderly patients with AML and raises the issue of the optimal protocol.

Predictive value of TP53 fluorescence in situ hybridization in cytogenetic subgroups of acute myeloid leukemia.

Acute myeloid leukemia (AML) with a complex karyotype (CK) has frequent alterations in TP53 and a very poor prognosis. We examined whether a prompt and simple fluorescence in situ hybridization (FISH) analysis for 17p13 deletion at diagnosis has a predictive value for response to therapy and overall survival in subgroups of AML. In 15 patients with a normal karyotype the TP53 FISH analysis was normal, whereas in 16 patients with CK 75% had only one copy of the TP53 allele. The deletion was also detected in 33% of six patients with monosomy or partial monosomy of chromosome 5, 7, 9, or 12. This loss of TP53 correlated significantly with a poor response to chemotherapy, and the median survival time of these patients was shorter. TP53 FISH analysis carried out at diagnosis has a predictive value with respect to chemotherapy response and can therefore facilitate a rapid decision on treatment strategies.

Tyrosine kinase inhibitors induced immune thrombocytopenia in chronic myeloid leukemia?

The outcome and quality of life of chronic myeloid leukemia (CML) patients has remarkably changed with the treatment of tyrosine kinase inhibitors (TKIs). Currently, hematopoietic stem cell transplantation (HSCT) is considered mainly as a third line salvage therapy in cases of TKIs resistance or intolerance. Here we describe a patient with chronic phase CML who developed both resistance and late occurrence of s severe thrombo-cytopenia on first and second generation TKIs and eventually underwent HSCT. Although the mechanism of the myelosuppression is not fully understood, we showed for the first time the development of dose dependent platelet antibodies in the presence of TKIs, suggesting the possibility of TKIs induced thrombocytopenia. Our case emphasizes that late development of severe myelosuppression during imatinib treatment is probably an important indication for consideration of early HSCT.

Can inhibition of the SDF-1/CXCR4 axis eradicate acute leukemia?

Poor prognosis of acute leukemia with current treatments is mainly due to the relapse of the disease following chemotherapy. In the last decade, an emerging concept has proposed that the leukemia stem cells (LSCs) and their interactions with the BM microenvironment are the major cause of the acute leukemia relapse. Adhesion to the stromal niche is crucial for LSCs as it directly supports self-renewal, proliferation, arrest of differentiation and protects from damaging chemo-agents. One of the key players in this crosstalk between leukemic cells and the BM stroma niche is the chemokine SDF-1. SDF-1 regulates the process of homing and engraftment of LSCs into the BM and inhibition of its receptor CXCR4 induces leukemic cell mobilization into the circulation. However, besides its chemotactic and adhesive functions, SDF-1 is also a pleiotropic cytokine that regulates leukemic cell proliferation as well as their program of differentiation. CXCR4 antagonists are used in combination with chemotherapy in preclinical and clinical studies, which demonstrate that blocking CXCR4 is a novel promising approach of therapy. In this review, we focus on the multifaceted SDF-1/CXCR4 axis in acute leukemia and discuss how targeting this pathway could provide potential interest to eradicate the LSCs.

Mesenchymal stromal cells revert multiple myeloma cells to less differentiated phenotype by the combined activities of adhesive interactions and interleukin-6.

Multiple myeloma is characterized by the malignant growth of immunoglobulin producing plasma cells, predominantly in the bone marrow. The effects of primary human mesenchymal stromal cells on the differentiation phenotype of multiple myeloma cells were studied by co-culture experiments. The incubation of multiple myeloma cells with bone marrow-derived mesenchymal stromal cells resulted in significant reduction of the expression of the predominant plasma cell differentiation markers CD38 and CD138, and cell surface immunoglobulin light chain. While the down-regulation of CD138 by stromal cells was completely dependent on their adhesive interactions with the multiple myeloma cells, interleukin-6 induced specific down-regulation of CD38. Mesenchymal stromal cells or their conditioned media inhibited the growth of multiple myeloma cell line, thereby reducing the overall amounts of secreted light chains. Analysis of primary multiple myeloma bone marrow samples reveled that the expression of CD38 on multiple myeloma cells was not affected by adhesive interactions. The ex vivo propagation of primary multiple myeloma cells resulted in significant increase in their differentiation markers. Overall, the data indicate that the bone marrow-derived mesenchymal stromal cells revert multiple myeloma cells to less differentiated phenotype by the combined activities of adhesive interactions and interleukin-6.

Engraftment of human blood malignancies to the turkey embryo: a robust new in vivo model.

Xenografting of human blood malignancies to immunodeficient SCID mice is a powerful research tool. We evaluate here whether the immunodeficient turkey embryo can also serve as a xenograft host for human blood malignancies. Human leukemia, lymphoma and myeloma lines engrafted robustly into medullary and extramedullary tissues of turkey embryos as detected by PCR, FACS and histology in 8-10 days. Four of eleven patient AML samples also engrafted the bone marrow. Grafts of two lines responded to chemotherapy with doxorubicin. The turkey embryo therefore has the potential to be a complementary xenograft model for the study of human blood malignancies.

Functional CXCR4-expressing microparticles and SDF-1 correlate with circulating acute myelogenous leukemia cells.

Stromal cell-derived factor-1 (SDF-1/CXCL12) and its receptor CXCR4 are implicated in the pathogenesis and prognosis of acute myelogenous leukemia (AML). Cellular microparticles, submicron vesicles shed from the plasma membrane of various cells, are also associated with human pathology. In the present study, we investigated the putative relationships between the SDF-1/CXCR4 axis and microparticles in AML. We detected CXCR4-expressing microparticles (CXCR4(+) microparticles) in the peripheral blood and bone marrow plasma samples of normal donors and newly diagnosed adult AML patients. In samples from AML patients, levels of CXCR4(+) microparticles and total SDF-1 were elevated compared with normal individuals. The majority of CXCR4(+) microparticles in AML patients were CD45(+), whereas in normal individuals, they were mostly CD41(+). Importantly, we found a strong correlation between the levels of CXCR4(+) microparticle and WBC count in the peripheral blood and bone marrow plasma obtained from the AML patients. Of interest, levels of functional, noncleaved SDF-1 were reduced in these patients compared with normal individuals and also strongly correlated with the WBC count. Furthermore, our data indicate NH(2)-terminal truncation of the CXCR4 molecule in the microparticles of AML patients. However, such microparticles were capable of transferring the CXCR4 molecule to AML-derived HL-60 cells, enhancing their migration to SDF-1 in vitro and increasing their homing to the bone marrow of irradiated NOD/SCID/beta2m(null) mice. The CXCR4 antagonist AMD3100 reduced these effects. Our findings suggest that functional CXCR4(+) microparticles and SDF-1 are involved in the progression of AML. We propose that their levels are potentially valuable as an additional diagnostic AML variable.

Motility, proliferation, and egress to the circulation of human AML cells are elastase dependent in NOD/SCID chimeric mice.

The role of the proteolytic enzyme elastase in motility and proliferation of leukemic human acute myeloblastic leukemia (AML) cells is currently unknown. We report a correlation between abnormally high levels of elastase in the blood of AML patients and the number of leukemic blast cells in the circulation. In AML cells, we observed expression of cell-surface elastase, which was regulated by the chemokine stromal cell-derived factor-1 (SDF-1). In vitro inhibition of elastase prevented SDF-1-induced cell polarization, podia formation, and reduced migration of human AML cells as well as their adhesion. Elastase inhibition also significantly impaired in vivo homing of most human AML cells to the bone marrow (BM) of nonobese diabetic-severe combined immunodeficient (NOD/SCID)/beta-2 microglobulin knock-out (B2m null) mice that underwent transplantation. Moreover, in vitro proliferation of AML cells was elastase dependent. In contrast, treatment with elastase inhibitor enhanced the proliferation rate of human cord blood CD34+ cells, including primitive CD34+/CD38- cells, and their in vivo homing. Finally, NOD/SCID mice previously engrafted with human AML cells and treated with elastase inhibitor had significantly reduced egress of leukemic cells into the circulation. Taken together, our data demonstrate that human AML cells constitutively secrete and express SDF-1-dependent cell-surface elastase, which regulates their migration and proliferation.

CXCR4 regulates migration and development of human acute myelogenous leukemia stem cells in transplanted NOD/SCID mice.

The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 participate in the retention of normal hematopoietic stem cells within the bone marrow (BM) and their release into the circulation. Homing and engraftment of human stem cells in immunodeficient mice are dependent on cell surface CXCR4 expression and the production of BM SDF-1, which acts also as a survival factor for both human and murine stem cells. However, the role of SDF-1/CXCR4 interactions in the control of human acute myelogenous leukemia (AML) cell trafficking and disease progression is poorly understood. In this study, we report that although some AML cells do not express surface CXCR4, all AML cells tested express internal CXCR4 and SDF-1. Culture of AML cells with SDF-1 promoted their survival, whereas addition of neutralizing CXCR4 antibodies, SDF-1 antibodies, or AMD3100 significantly decreased it. Pretreatment of primary human AML cells with neutralizing CXCR4 antibodies blocked their homing into the BM and spleen of transplanted NOD/SCID/B2m(null) mice. Furthermore, weekly administrations of antihuman CXCR4 to mice previously engrafted with primary AML cells led to a dramatic decrease in the levels of human AML cells in the BM, blood, and spleen in a dose- and time-dependent manner. Interestingly, the same treatment did not affect significantly the levels of normal human progenitors engrafted into NOD/SCID mice. Taken together, our findings demonstrated the importance of the SDF-1/CXCR4 axis in the regulation of in vivo motility and development of human AML stem cells and identified CXCR4 neutralization as a potential treatment for AML.

Restoration of C/EBPalpha expression in a BCR-ABL+ cell line induces terminal granulocytic differentiation.

The transcription factor C/EBPalpha plays a critical role in the process of granulocytic differentiation. Recently, mutations that abrogated transcriptional activation of C/EBPalpha were detected in acute myeloid leukemia patient samples. Moreover, the progression of chronic myelogenous leukemia (CML) to blast crisis in patients was correlated with down-modulation of C/EBPalpha. The KCL22 cell line, derived from BCR-ABL+ CML in blast crisis, expressed wild-type C/EBPepsilon protein but not a functional C/EBPalpha, -beta, and -gamma. Restoration of C/EBPalpha expression in KCL22 cells triggered a profound proliferative arrest, a block in the G2/M phase of the cell cycle and a gradual increase in apoptosis. Within 3 days of inducing expression of C/EBPalpha, a remarkable neutrophilic differentiation of the KCL22 blast cells occurred as shown by morphologic changes, induction of expression of CD11b, primary, secondary, and tertiary granule proteins, and granulocyte colony-stimulating factor receptor. Using high density oligonucleotide microarrays, the gene expression profile of KCL22 cells stably transfected with C/EBPalpha was compared with that of empty vector, and we identified genes not previously known to be regulated by C/EBPalpha. These included the up-regulation of those genes important for regulation of hematopoietic stem cell homing, granulocytic differentiation, and cell cycle, whereas down-regulation occurred for genes coding for signaling molecules and transcription factors that are implicated in regulation of proliferation and differentiation of hematopoietic cells. Our study showed that restoration of C/EBPalpha expression in BCR-ABL+ leukemic cells in blast crisis is sufficient for rapid neutrophil differentiation suggesting a potential therapeutic role for ectopic transfer of C/EBPalpha in acute phase of CML.

C/EBP-beta, C/EBP-delta, PU.1, AML1 genes: mutational analysis in 381 samples of hematopoietic and solid malignancies.

Mutations of transcription factors are associated with the pathogenesis of cancer. Genomic DNA from 381 cancers and cell lines representing leukemias, lymphomas and a variety of solid tumors were examined for mutations of genes coding for the C/EBP-beta, C/EBP-alpha, PU.1, and AML1 transcription factors using single strand conformation polymorphism (SSCP) and direct DNA sequencing. Mutation of C/EBP-beta (a chronic myelogenous leukemia cell line, Kcl22) and C/EBP-delta (a Burkitt's lymphoma cell line, Raji) were found. Interestingly, the sample with a C/EBP-beta alterations had two missense (P236L and G252A) and two silent mutations in a highly conserved region of the gene. The C/EBP-delta alteration in Raji was a missense mutation (A177G). These findings suggest that mutations of the C/EBP-beta, C/EBP-delta, PU.1, and AML1 rarely contribute to the development of hematopoietic or solid cancers.