Discordant pathologic diagnoses of myelodysplastic neoplasms and their implications for registries and therapies

Myelodysplastic neoplasms (MDS) are a collection of hematopoietic disorders with widely variable prognoses and treatment options. Accurate pathologic diagnoses present challenges because of interobserver variability in interpreting morphology and quantifying dysplasia. We compared local clinical site diagnoses with central, adjudicated review from 918 participants enrolled in the ongoing National Heart, Lung, and Blood Institute National MDS Natural History Study, a prospective observational cohort study of participants with suspected MDS or MDS/myeloproliferative neoplasms (MPNs). Locally, 264 (29%) were diagnosed as having MDS, 15 (2%) MDS/MPN overlap, 62 (7%) idiopathic cytopenia of undetermined significance (ICUS), 0 (0%) acute myeloid leukemia (AML) with <30% blasts, and 577 (63%) as other. Approximately one-third of cases were reclassified after central review, with 266 (29%) diagnosed as MDS, 45 (5%) MDS/MPN overlap, 49 (5%) ICUS, 15 (2%) AML with <30%, and 543 (59%) as other. Site miscoding errors accounted for more than half (53%) of the local misdiagnoses, leaving a true misdiagnosis rate of 15% overall, 21% for MDS. Therapies were reported in 37% of patients, including 43% of patients with MDS, 49% of patients with MDS/MPN, and 86% of patients with AML with <30% blasts. Treatment rates were lower (25%) in cases with true discordance in diagnosis compared with those for whom local and central diagnoses agreed (40%), and receipt of inappropriate therapy occurred in 7% of misdiagnosed cases. Discordant diagnoses were frequent, which has implications for the accuracy of study-related and national registries and can lead to inappropriate therapy. This trial was registered at www.clinicaltrials.gov as #NCT05074550.

Case report: Co-existing chronic myeloid leukemia and chronic myelomonocytic leukemia-A clinically important but challenging scenario

Chronic myeloid leukemia (CML) and chronic myelomonocytic leukemia (CMML) are two common myeloid neoplasms with overlapping morphologic features. We report a patient initially diagnosed with CML and treated with Tyrosine kinase inhibitor (TKI) but who then developed persistent monocytosis and worsening thrombocytopenia one year later. Repeat bone marrow biopsies only showed CML at the molecular level. However, markedly hypercellular bone marrow, megakaryocytic dysplasia, and SRSF2, TET2, and RUNX1 mutations by NextGen sequencing pointed to a diagnosis of CMML. For CML patients with persistent monocytosis and cytopenia, a mutational profile by NGS is helpful to exclude or identify the coexisting CMML.

Co-mutation of ASXL1 and SF3B1 Predicts Poorer Overall Survival Than Isolated ASXL1 or SF3B1 Mutations

BACKGROUND/AIM

Mutations in the ASXL transcriptional regulator 1 (ASXL1) and splicing factor 3b subunit 1(SF3B1) genes are commonly observed in myeloid neoplasms and are independent predicative factors for overall survival (OS). Only a few contradictory reports exist on the clinical significance of concurrent ASXL1 and SF3B1 mutations. Previous studies also did not exclude patients with mutations of other genes, which could be confounding factors.

MATERIALS AND METHODS

We identified 69 patients with mutation of only ASXL1, 89 patients with mutation of only SF3B1, and 17 patients with mutations exclusively of both ASXL1 and SF3B1 from our database of 8,285 patients and compared their clinical features and outcomes.

RESULTS

Patients with ASXL1 mutations more frequently had acute myeloid leukemia (22.47%) or clonal cytopenia of unknown significance than patients with SF3B1 mutations (1.45%) or with ASXL1/SF3B1 mutations (11.76%). Patients with SF3B1 or ASXL1/SF3B1 mutations were more frequently diagnosed with myelodysplastic syndrome (75.36% and 64.71%, respectively) than patients with ASXL1 mutations (24.72%). Patients with ASXL1/SF3B1 (23.53%) mutations more frequently had myelodysplastic/myeloid proliferative neoplasm than did patients with ASXL1 mutations (5.62%) or with SF3B1 mutations (15.94%). OS of the ASXL1 mutation-only group was worse than that of the SF3B1 mutation-only group with a hazard ratio of 5.83 (p=0.017). Finally, and most importantly, the OS of the ASXL1/SF3B1 co-mutation group was poorer than that of both single-mutation groups (p=0.005).

CONCLUSION

ASXL1/SF3B1 co-mutations portend worse OS than isolated ASXL1 or SF3B1 mutations, which might be due to abnormalities in both the epigenetic-regulatory and RNA-splicing pathways or because two genes instead of one are mutated.

Clinicopathologic characteristics, genetic features, and treatment options for acute lymphoblastic leukemia with JAK2 rearrangement-A 10-case study and literature review

JAK2 rearrangement (JAK2-R) in acute lymphoblastic leukemia (ALL) is rare and often categorized as B-ALL with BCR::ABL1-like features based on the World Health Organization classification. We report 10 patients with JAK2-R ALL, 9 males and 1 female, with a median age 40.5 years. Eight patients presented with marked leukocytosis (median WBC, 63 × 10 ⁹/L) and hypercellular (>95%) bone marrow with increased lymphoblasts (72%-95%). There was no evidence of bone marrow fibrosis or hypereosinophilia. Immunophenotypic analysis showed 9 B-cell and 1 T-cell neoplasms. Using fluorescence in situ hybridization (FISH) and RNA sequencing analysis, JAK2 partners were identified for 7 cases and included PCM1 (n=4), ETV6 (n=2) and BCR (n=1). All patients received upfront polychemotherapy. Additionally, 2 patients received ruxolitinib, 2 received allogeneic stem cell transplant, and 1 received CAR-T therapy. The 1- and 3-year overall survival rates were 55.6% and 22.2%, respectively. A literature review identified 24 B-ALL and 4 T-ALL cases with JAK2-R reported, including 16 males, 6 females and 6 gender not stated. Many JAK2 partner-genes were reported with the most common being PAX5 (n=7), ETV6 (n=4), BCR (n=3) and PCM1 (n=2). Survival data or 13 reported cases showed 1- and 3-year overall survival rates of 41.7% and 41.7%, respectively. In summary, JAK2-R ALL occurs more often in adult males, are mostly of B-cell lineage, and associated with an aggressive clinical course. Absence of eosinophilia and bone marrow fibrosis and no evidence of preexisting/concurrent JAK2-R myeloid neoplasms distinguish JAK2-R ALL from other myeloid/lymphoid neoplasms with eosinophilia and JAK2-R.

Clinical Response to Upfront Targeted Tyrosine Kinase Inhibitors among Patients with Myeloid/Lymphoid Neoplasms with Eosinophilia and Tyrosine Kinase Gene Fusion

INTRODUCTION

Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusion (MLN-TK) is an entity encompassed of a heterogeneous group of rare hematopoietic neoplasms that are driven by gene fusion involving PDGDRA/B, FGFR1, JAK2, FLT3 or ETV6::ABL1. Though patients presenting with chronic phase MLN-TK with PDGFRA fusion display a favorable outcome in response to upfront TK inhibitor (TKI) therapy, the outcomes of MLNs driven by other TK fusions are not well described. In this study, we aimed to critically analyze the treatment outcomes of patients with MLN-TK, focusing on the role of upfront TKIs in both chronic- and blast-phase diseases.

METHODS

The retrospective study included patients with confirmed MLN-TK from 3 centers and assessed demographic and clinical variables, treatment, and outcomes.

RESULTS

Forty-two patients with confirmed MLN-TK [PDGFRA (n = 22), PDGFRB (n = 4), FGFR1(n = 10), JAK2 (n = 2); and FLT3 (n = 3)] were included. Fifteen of 25 (60%) chronic-phased patients received upfront TKI therapy had a long-term remission. Nine of 16 (60%) blast-phase patients with upfront TKIs also achieved complete remission and remained alive at a median follow-up of 20 months. All 3 patients with blast phase disease who received upfront chemotherapy without positive response did not respond to subsequent TKI therapy, emphasizing the importance of initiating TKI therapy early. Upfront TKI therapy was associated with longer overall survival in univariate analyses (HR, 0.054 [95% CI, 0.007-0.42]) and multivariate analyses (HR, 0.03 [95% CI, 0.002-0.47]).

CONCLUSION

The outcomes of upfront TKI therapy are excellent for MLN-TK in both chronic and blast phases, regardless of gene abnormalities.

MPN-521 Somatic Mutational Landscape and Clinical Response to Upfront Targeted Tyrosine Kinase Inhibitors Among Patients With Myeloid and Lymphoid Neoplasms With Eosinophilia and Rearrangements of PDGFRA, PDGFRB, FGFR1, JAK2, or FLT3

CONTEXT

In 2016, WHO put together a category of myeloid and lymphoid neoplasms with eosinophilia (MLN-Eo) with rearrangement of PDGFRA, PDGFRB, FGFR1, or PCM1-JAK2. Gene fusions involving FLT3 and JAK2 are considered potential provisional entities. Here, we describe the mutational landscape of MLN-Eo and clinical outcomes of upfront targeted TK inhibitor (TKI) therapy.

DESIGN

We retrospectively reviewed clinical and molecular data on patients with MLN-Eos. Next-generation sequencing was performed using a customized or commercially available panel.

RESULTS

Twenty-three patients had PDGFRA fusion or activating mutations; 4 PDGFRB fusion; 8 FGFR1 fusion; 2 JAK2 fusion; and 4 FLT3 fusion. Twelve (92%) had at least one other coexisting mutation. At least 2 patients harbored TET2, RUNX1, TP53, and PTPN11 mutations. Pathogenic PTPN11 mutation was present in all activating PDGFRA mutations but absent in other cases. Among 23 patients with the chronic-phase disease, 14 (61%) received upfront TKI. None transformed into blastic phase. Six patients with disease in the de novo blastic phase received upfront TKI and achieved complete remission. Upfront TKI use was associated with longer overall survival (OS) in univariate analysis (HR 0.065, 95% CI, 0.008-0.50. P =.008). The improved OS remained significant in a multivariate analysis (HR 0.043, 95% CI, 0.003-0.63, p = 0.021) when adjusted for sex, age, hypereosinophilia, PDGFRA/B fusion, complex cytogenetics, the blastic- phase, and transplant status.

CONCLUSIONS

Patients with MLN-Eo have high frequency of secondary somatic mutations like other myeloid malignancies. TKI therapies are associated with excellent outcomes and should be used in the upfront setting.

The Application of NextGen Sequencing in the Diagnosis of Myeloid Neoplasms in Myeloma Patients With Cytopenia

BACKGROUND

Multiple myeloma (MM) is an incurable clonal neoplasm that usually requires long-term treatment, which may result in secondary cytopenia(s) and myeloid neoplasms. We investigated the landscape of mutations detected by NextGen sequencing (NGS) in myeloma patients with cytopenia.

METHODS AND MATERIALS

MM patients (n = 196) with cytopenia(s) and NGS results were identified and divided into 4 groups: 1) patients with myeloma only and no myeloid neoplasms; 2) patients with myeloid neoplasms but no myeloma; 3) patients with concurrent myeloma and myeloid neoplasms; and 4) patients with no myeloma or myelodysplasia.

RESULTS

The most frequently mutated genes were TP53, DNMT3A, TET2, ASXL1, and KRAS. TP53 mutations were predominantly found among patients with myeloid neoplasms with or without concomitant MM. SF3B1 and TET, the genes most commonly mutated in myelodysplastic syndromes, were less frequently identified among MM patients. ASXL1 mutations were more commonly associated with myeloid neoplasms, whereas KRAS and DNMT3A mutations were more closely associated with MM than myeloid neoplasms. RUNX1 mutations showed closer association with myeloid neoplasms. Fifty-eight patients harbored clonal myeloid gene mutations but no overt morphologic or cytogenetic abnormalities, of which 7 patients had myelodysplastic syndromes that was missed by the original pathologists. Thrombocytopenia appeared to be a more reliable marker than anemia or neutropenia to trigger work-up for myeloid neoplasms.

CONCLUSION

NGS could greatly help with diagnosing myeloid neoplasms in MM patients with cytopenia(s). The depicted gene landscape may facilitate our daily interpretation of NextGen sequencing (NGS).

Comparison of SF3B1/DNMT3A Comutations With DNMT3A or SF3B1 Mutation Alone in Myelodysplastic Syndrome and Clonal Cytopenia of Undetermined Significance

OBJECTIVES

To compare the clinical significance of SF3B1/DNMT3A Comutations with SF3B1 or DNMT3A mutation alone in myelodysplastic syndrome (MDS) and clonal cytopenia of undetermined significance (CCUS).

METHODS

We identified and compared 31 patients with only DNMT3A mutation, 48 patients with only SF3B1 mutation, and 16 patients with only SF3B1/DNMT3A comutations.

RESULTS

SF3B1/DNMT3A comutations were found to be more common in MDS, whereas DNMT3A mutation alone was more common in CCUS. The patients with SF3B1/DNMT3A comutations were less likely to have poor cytogenetics than patients with DNMT3A mutation alone. Patients with SF3B1/DNMT3A comutations showed significantly longer median survival time and better overall survival than patients with DNMT3A mutation alone.

CONCLUSIONS

Patients with SF3B1/DNMT3A comutations appear to have better clinical outcomes than patients with isolated DNMT3A mutation. These findings suggest that the favorable prognosis of SF3B1 mutation in is not abrogated by the concurrent presence of a DNMT3A mutation.

Does SF3B1/TET2 Double Mutation Portend Better or Worse Prognosis Than Isolated SF3B1 or TET2 Mutation?

BACKGROUND

Mutations in splicing factor 3b subunit 1 (SF3B1) have been reported to be associated with a favorable prognosis, while the prognostic impact of tet methylcytosine dioxygenase 2 (TET2) mutations is still controversial. The clinical significance of combined SF3B1 and TET2 mutation is even more uncertain. In this study, the clinical consequences of concurrent double SF3B1/TET2 mutation were compared with isolated SF3B1 or TET2 mutation.

MATERIALS AND METHODS

The demographics, diagnosis, cytogenetic abnormalities, and overall survival time of 130 patients with isolated SF3B1 (n=48) or TET2 mutation (n=54), or double SF3B1/TET2 mutation (n=28) were compared by next-generation sequencing.

RESULTS

Patients with double mutation were found to be significantly older than patients with isolated TET2 mutation. Patients with double mutation or isolated SF3B1 mutation were less likely to be diagnosed with acute myeloid leukemia than patients with isolated TET2 mutation. Patients with myelodysplasia had a higher percentage of double or isolated SF3B1 mutation, while patients with myeloproliferative neoplasms had a higher percentage of isolated TET2 mutation. Patients with double mutation more frequently had increased ring sideroblasts similarly to patients with isolated SF3B1 mutation. The percentage of patients with normal cytogenetics or good cytogenetic abnormalities was significantly higher in patients with double mutation than those with isolated mutation. Finally, in patients with myelodysplasia and normal cytogenetics, the median survival time in those with double mutation was significantly longer than in those with isolated SF3B1 mutation, even though the overall survival curve was not statistically significant.

CONCLUSION

TET2 mutation appeared not to have additional effects when combined with SF3B1, and patients with double mutation appeared to have at least as, good as or even better prognosis than patients with isolated mutation.

TP53 and IDH2 Somatic Mutations Are Associated With Inferior Overall Survival After Allogeneic Hematopoietic Cell Transplantation for Myelodysplastic Syndrome

BACKGROUND

Next-generation sequencing has identified somatic mutations that are prognostic of cancer.

PATIENTS AND METHODS

We evaluated the incidence and prognostic significance of somatic mutations in 89 myelodysplastic syndrome (MDS) patients who received an allogeneic hematopoietic cell transplantation. Next-generation sequencing was performed on paraffin embedded bone marrow, which was obtained at a median of 31 days before initiating the preparative regimen.

RESULTS

The 3 most common subtypes of MDS were refractory anemia with excess blasts (RAEB)-1 (35%), RAEB-2 (29%), and refractory cytopenia with multilineage dysplasia (18%). Most patients (91%) received a myeloablative regimen of fludarabine with intravenous busulfan. Somatic mutations (> 0) were identified in 39 (44%) of analyzed samples. The 6 most commonly identified gene mutations were ASXL1 (8%), DNMT3A (8%), RUNX1 (7%), KRAS (6%), IDH2 (4%), and TP53 (4%). The low incidence of mutations in our study sample might be explained by tissue source and stringent variant-calling methodology. Moreover, we speculate that the low incidence of mutations might, perhaps, also be explained by previous azacitidine treatment in 82% of cases. Multivariate analysis identified TP53 (hazard ratio [HR], 3.82; 95% confidence interval [CI], 1.12-13.09; P = .03) and IDH2 mutations (HR, 4.74; 95% CI, 1.33-16.91; P = .02) as predictors of inferior 3-year overall survival.

CONCLUSION

This study furthers implementation of clinical genomics in MDS and identifies TP53 and IDH2 as targets for pre- or post-transplant therapy.

Flow cytometric identification of immunophenotypically aberrant T-cell clusters on skin shave biopsy specimens from patients with mycosis fungoides

OBJECTIVES

To assess the ability of flow cytometry (FC) to detect putative neoplastic T-cell subsets on skin shave biopsy (SSB) specimens from patients with mycosis fungoides (MF) and to study the immunophenotype of skin-infiltrating tumor cells in MF.

METHODS

SSB specimens from patients with suspected MF were bisected and submitted for both FC and routine histopathology. Six-dimensional gating strategies were applied to identify putative neoplastic cells, independently from their expected immunophenotype.

RESULTS

Aberrant T cells were detected by FC in 18 of 33 SBB specimens, of which all had clinicomorphologic features of MF. Of the remaining 15 SSB specimens, six had clinicomorphologic features of MF and nine were diagnosed with benign inflammatory dermatoses. Unexpectedly, CD26 was aberrantly overexpressed in 11 (73%) and lost in three (20%) of 15 SSB specimens from patients with MF where this antigen was evaluated. Other detected aberrancies included CD3 dim- (13/18 [72%]), CD7 dim- (15/18 [83%]), and CD4-/CD8- (3/18 [17%]).

CONCLUSIONS

FC is capable of identifying putative neoplastic cells on SSB specimens from patients with MF. Bright homogeneous CD26 expression is a common and previously undescribed immunophenotypic aberrancy on MF skin infiltrates.

A close association of autoimmune-mediated processes and autoimmune disorders with chronic myelomonocytic leukemia: observation from a single institution

Chronic myelomonocytic leukemia (CMML), a clonal hematopoietic stem cell disease, may be linked to immune-mediated processes and/or autoimmune disorders (AID), although the exact pathogens are still elusive. We retrospectively analyzed 123 CMML patients in our institution. Twenty-four CMML patients (19.5%) had at least one immune-mediated disorder, most commonly idiopathic thrombocytopenic purpura, gout and psoriasis. Four of these 24 patients (15%) had more than one AID. We found that, in contrast to the general population with a prevalence rate of 3.2-5.2%, newly diagnosed CMML patients demonstrated a high prevalence and variety of immune-mediated processes and/or AID. When we compared the results with those of myelodysplastic syndromes published in the literature, the prevalence of AID in these two groups of patients is similar. Our results also showed that the presence of cytogenetic abnormalities was less in CMML patients with AID (6 of 21; 28.6%) than in those without AID (37 of 94; 39.4%), although there was no statistical significance (p = 0.334). A multicenter large cohort study of CMML with AID is recommended to illustrate the molecular relationship between the two distinct groups.

Concurrence of B-lymphoblastic leukemia and myeloproliferative neoplasm with copy neutral loss of heterozygosity at chromosome 1p harboring a MPL W515S mutation

B-lymphoblastic leukemia (B-ALL) is a neoplasm of precursors committed to B-cell lineage, whereas myeloproliferative neoplasm (MPN) is a clonal proliferation derived from myeloid stem cells. Concurrent B-ALL with MPN is uncommon except in the presence of abnormalities of the PDGFRA, PDGFRB, or FGFR1 genes or the BCR-ABL1 fusion gene. Herein, we describe a rare concurrence, B-ALL with MPN without the aforementioned genetic aberrations, in a 64-year-old male patient. The patient was initially diagnosed with B-ALL with normal karyotype and responded well to aggressive chemotherapy but had sustained leukocytosis and splenomegaly. The posttreatment restaging bone marrow was free of B-ALL but remained hypercellular with myeloid predominance. Using a single nucleotide polymorphism microarray study, we identified a copy neutral loss of heterozygosity at the terminus of 1p in the bone marrow samples taken at diagnosis and again at remission, 49% and 100%, respectively. Several additional genetic abnormalities were present in the initial marrow sample but not in the remission marrow samples. Retrospective molecular studies detected a MPL W515S homozygous mutation in both the initial and remission marrows for B-ALL, at 30-40% and 80% dosage effect, respectively. In summary, we present a case of concurrent B-ALL and MPN and demonstrate a stepwise cytogenetic and molecular approach to the final diagnosis.

Fibrosis and subsequent cytopenias are associated with basic fibroblast growth factor-deficient pluripotent mesenchymal stromal cells in large granular lymphocyte leukemia

Cytopenias occur frequently in systemic lupus erythematosus, rheumatoid arthritis, Felty's syndrome, and large granular lymphocyte (LGL) leukemia, but the bone marrow microenvironment has not been systematically studied. In LGL leukemia (n = 24), retrospective analysis of bone marrow (BM) histopathology revealed severe fibrosis in 15 of 24 patients (63%) in association with the presence of cytopenias, occurrence of autoimmune diseases, and splenomegaly, but was undetectable in control cases with B cell malignancies (n = 11). Fibrosis severity correlated with T cell LGL cell numbers in the BM, but not in the periphery, suggesting deregulation is limited to the BM microenvironment. To identify fibrosis-initiating populations, primary mesenchymal stromal cultures (MSCs) from patients were characterized and found to display proliferation kinetics and overabundant collagen deposition, but displayed normal telomere lengths and osteoblastogenic, chondrogenic, and adipogenic differentiation potentials. To determine the effect of fibrosis on healthy hematopoietic progenitor cells (HPCs), bioartificial matrixes from rat tail or purified human collagen were found to suppress HPC differentiation and proliferation. The ability of patient MSCs to support healthy HSC proliferation was significantly impaired, but could be rescued with collagenase pretreatment. Clustering analysis confirmed the undifferentiated state of patient MSCs, and pathway analysis revealed an inverse relationship between cell division and profibrotic ontologies associated with reduced basic fibroblast growth factor production, which was confirmed by ELISA. Reconstitution with exogenous basic fibroblast growth factor normalized patient MSC proliferation, collagen deposition, and HPC supportive function, suggesting LGL BM infiltration and secondary accumulation of MSC-derived collagen is responsible for hematopoietic failure in autoimmune-associated cytopenias in LGL leukemia.

Pathophysiology of cytopenias in an autoimmune lymphoproliferative disease linked to bone marrow fibrosis (P3165)

Large Granular Lymphocyte (LGL) leukemia is associated with unexplained cytopenias, autoimmune features, and CD57+CD8+perforin+ T-cell lympoproliferation. Like many autoimmune disorders, the pathophysiology of cytopenias in LGL leukemia is unknown. Bone marrow (BM) pathology from 24 LGL leukemia patients was retrospectively studied using H&E, reticulin, and trichrome-stained sections, and revealed that BM fibrosis was present in 21 out of 24 patients (88%). Fibrosis, a previously undefined complication, was significantly associated with splenomegaly, the presence of cytopenias, and coexistance of autoimmune diseases. LGL cell numbers in the BM, but not peripheral blood, was associated with fibrosis severity. Colony forming assays in the presence of exogenous bioartificial collagen matrix using healthy bone marrow mononuclear cells (BM-MNCs) revealed a direct inhibitory effect of collagen on progenitor growth. Consistent with microarray analysis, primary mesenchymal stromal cultures (MSCs) from LGL leukemia BM displayed heightened collagen deposition. In co-culture assays, collagen matrix produced by LGL MSCs directly inhibited healthy hematopoietic progenitor growth support. This study demonstrates that excessive collagen matrix deposition by deregulated MSCs may result from the local BM accumulation of activated CD8+ LGL leukemia T-cells. Therefore, BM fibrosis should be explored as a mechanism for secondary cytopenias associated with autoimmune diseases.

Abstract 4944: Combined treatment of BTK and PI3K inhibitors synergistically disrupts BCR-signaling, overcomes microenviroment-mediated survival and drug resistance in mantle cell lymphoma

Mantle cell lymphoma (MCL) is recognized as an aggressive lymphoma characterized by overexpression of cyclin D1 as a result of t (11:14) translocation. It carries poor prognosis due to the emergence of drug resistance and currently no effective cure is available for this disease. Dynamic interactions between the lymphoma cell and its microenvironment play a critical role in lymphoma development and response to therapy. Recently, inhibitors of BCR signaling have become an area of substantial clinical interest. B-cell receptor (BCR) provides essential growth and survival signals to lymphomas. We therefore studied the role of BCR signal pathways in stroma mediated survival and drug resistance of mental cell lymphoma.

We demonstrate that all mantle cell lymphoma cell lines and primary MCL cells express key BCR downstream signaling molecules, BTK (Bruton's tyrosine kinase), AKT and ERK, in activated (phosphorylated) form. Phosphorylation statutes of pBTK, pAKT and pERK are further up regulated upon adhesion to lymph node stroma cells. Cell adhesion between lymphoma cells and tumor stroma cells is essential for tumor cell survival and drug resistance. Inhibition of BTK by PCI 32765 or PI3Kδ by CAL101 abolishes intrinsic as well as stroma induced activation of BTK, AKT, ERK. It also significantly disrupts tumor - stromal cell adhesion and induces cell apoptosis. Moreover, combined treatment of PCI 32765 and CAL101 synergetically inhibit BCR signaling and induce cell apoptosis in absence and presence of HK stroma cells.

CXCR4 has been reported to play a critical role in lymphoma cell homing, migration, and adhesion. We evaluated CXCR4 expression upon MCL adhesion to stroma cells. We demonstrate that the CXCR4 level was significantly increased in Jeko-1 and HBL2 cell lines and primary MCL cells when co-cultured with HK stroma cells. The stroma cells-induced CXCR4 increase was significantly abolished by BCR signaling inhibitors, PCI 32765 and Cal101.

We further explored the effect of those inhibitors on cyclin D1. We show that cyclin D1 is constitutively expressed in MCL cell lines and primary MCL cells and that its expression was further increased when co-cultured with HK stoma cells. Both PCI 32765 and Cal101 decreased intrinsic cyclin D1 expression in the absence and presence of HK cells. Furthermore, combined treatment of PCI 32765 and Cal101 more strikingly attenuated cyclin D1 expression than either agent alone.

Collectively, Our study demonstrates (1) the constitutive expression and biological function of BCR signaling in MCL, (2) the essential role of BCR signaling in microenvironment (stroma cell) mediated MCL survival, adhesion and drug resistance, and (3) the therapeutic potential of using novel BCR inhibitors, PCI 32765 and Cal101, in single or combine for MCL therapy.

Citation Format: Jiangchuan Tao, Tint Lwin, Xiaohong Zhao, Bijal Shah, Ling Zhang, Lynn Moscinski, William Dalton, Eduardo M. Sotomayor, Jianguo Tao. Combined treatment of BTK and PI3K inhibitors synergistically disrupts BCR-signaling, overcomes microenviroment-mediated survival and drug resistance in mantle cell lymphoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4944. doi:10.1158/1538-7445.AM2013-4944

Natural history and clinical prognosis of in situ mantle cell lymphoma

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Background: In-Situ Mantle Cell Lymphoma is a rare clinical entity that presents with involvement limited to the mantle zone of secondary follicles. Its true incidence may be underestimated and its natural history and clinical behavior remains poorly characterized given the small number of representative cases available in the literature. Current guidelines for patients diagnosed with In-Situ Mantle Cell Lymphoma advocate staging studies and close follow-up with treatment based on the clinical behavior of the disease. Methods: Database review of 204 patients diagnosed with Mantle Cell Lymphoma at Moffitt Cancer Center between May 1992 and December 2010 Results: Three cases of In-Situ Mantle Cell Lymphoma were found and analyzed. Patients 1 & 2 had disease isolated to a single lymph node at diagnosis. In these cases, there were long latency periods of 5 and 9 years between initial resection of a single nodal site and later presentation with active, diffuse disease. Neither patient received therapy until progression with more advanced disease. Patient 2, who had a 9-year latency period was found to have complex cytogenetics suggesting evolution of the malignant clone during this prolonged latency period. Patient 3 presented with in situ disease in an inguinal node in conjunction with diffuse extranodal lung and forehead involvement, all noted at the time of diagnosis. Patient 1 obtained remission with Bendamustine & Rituxamab. Patient 2 obtained remission with HyperCVAD and Autologous HSCT consolidation. Patient 3 obtained remission after R-CHOP. Patients 1 & 2, both with long latency periods remain alive and free of disease, while patient 3 relapsed with extranodal disease 3 years after initial therapy. Conclusions: The natural history of In Situ-Mantle Cell Lymphoma varies with prolonged latency periods present in some patients. The genetic profile of the lymphoma may evolve during these latency periods portending a more aggressive clinical course at progression. Patients with newly diagnosed In-Situ Mantle Cell Lymphoma with no other evidence of active disease should be followed expectantly with therapy reserved for those patients whose disease progresses during followup.

Unusual primary presentations of mantle cell lymphoma in the urinary tract and testes

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Background: The initial clinical presentation of Mantle Cell Lymphoma is protean, ranging from single sites of indolent disease followed for years without therapy to aggressive disseminated disease that requires treatment within weeks of diagnosis. While many cases of Mantle Cell Lymphoma present with disseminated disease, other patients may present with symptoms related to a primary extranodal site of disease. The majority of these primary extranodal cases are diagnosed in the gastrointestinal tract, other cases have been noted in the skin, conjunctiva, testes and male genitourinary tract. Methods: Database review of 204 patients diagnosed with Mantle Cell Lymphoma at Moffitt Cancer Center between May 1992 and December 2010. Results: Three cases of Mantle Cell Lymphoma presented with symptoms related to primary extranodal sites in the urinary tract and male genital organs. Two cases of testicular involvement presented with gradual enlargement of the testes. In patient 1, the orchiectomy specimen harbored both seminoma and mantle cell lymphoma. Low level bone marrow involvement by mantle cell lymphoma was present and in the presence of indolent features he was treated for his primary seminoma and followed expectantly for mantle cell lymphoma. In patient 2, orchiectomy revealed a pleomorphic variant of mantle cell lymphoma with no other sites of disease on staging workup. He was treated with 6 cycles of R-CHOP and prophylactic IT methotrexate with a complete remission. A third patient presented with obstructive urinary symptoms and was found to have mantle cell lymphoma of the prostate. Additional staging revealed diffuse lymphadenopathy, colon and bone marrow involvement. A complete remission was obtained with 6 cycles of R-CHOP. None of these three patients was found to have evidence of CNS involvement at diagnosis or in followup with only the second patient receiving intrathecal prophylaxis. Conclusions: Mantle Cell Lymphoma may present with unusual extranodal involvement at diagnosis including sites and symptoms related to the genitourinary tract and testes. Diagnostic lumbar puncture and intrathecal prophylaxis should be considered in these patients.

Identification of a risk dependent microRNA expression signature in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) display both haematological and biological heterogeneity with variable leukaemia potential. MicroRNAs play an important role in tumour suppression and the regulation of self-renewal and differentiation of haematopoietic progenitors. Using a microarray platform, we evaluated microRNA expression from 44 patients with MDS and 17 normal controls. We identified a thirteen microRNA signature with statistically significant differential expression between normal and MDS specimens (P < 0·01), including down-regulation of members of the leukaemia-associated MIRLET7 family. A unique signature consisting of 10 microRNAs was closely associated with International Prognostic Scoring System (IPSS) risk category permitting discrimination between lower (Low/Intermediate-1) and higher risk (Intermediate-2/High) disease (P < 0·01). Selective overexpression of MIR181 family members was detected in higher risk MDS, indicating pathogenetic overlap with acute myeloid leukaemia. Survival analysis of an independent cohort of 22 IPSS lower risk MDS patients revealed a median survival of 3·5 years in patients with high expression of MIR181 family compared to 9·3 years in patients with low MIR181 expression (P = 0·002). Our pilot study suggested that analysis of microRNA expression profile offers diagnostic utility, and provide pathogenetic and prognostic discrimination in MDS.

A molecular and functional analysis of large granular lymphocyte expansions in patients with chronic myelogenous leukemia treated with tyrosine kinase inhibitors

Tyrosine kinase inhibitor (TKI) therapy has become the standard treatment for chronic myelogenous leukemia (CML). Off-target kinase inhibition has been implicated in the appearance of unique adverse effects, such as colitis and pleural effusions. In addition, some patients present oligoclonal expansions of large granular lymphocytes (LGLs). We sought to further investigate this phenomenon in 64 patients treated with five different TKIs. Clonal expansions of cytotoxic T lymphocytes (CTLs) were identified in all TKI-treated patient groups, but only in dasatinib-treated patients were these expansions characterized as LGLs. Survival factors known to be important in LGL leukemia (interleukin-15 [IL-15] transpresentation, plasma platelet-derived growth factor [PDGF]-BB levels, nuclear factor-κB [NF-κB] and T-bet activation) were found to be associated with TKI-induced LGL expansions. Interestingly, patients with LGL expansions had increased cytotoxicity against non-transformed endothelial cells, which may play a role in observed autoimmune-like side effects. Our results indicate that patients with CML treated with TKIs can develop T cell expansions, which can in certain cases be related to some adverse effects.

Mixed phenotype acute leukemia with t(11;19)(q23;p13.3)/ MLL-MLLT1(ENL), B/T-lymphoid type: A first case report

The majority of cases of acute leukemia belong to a specific lineage origin, either lymphoid or myeloid, and therefore are classified as acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML), based on morphologic features and cytochemical and immunophenotypic profile of the blast cells. A minority of acute leukemias however, show no clear evidence of differentiation along a single lineage. These are now classified under acute leukemias of ambiguous lineage by the most recent WHO classification and account for <4% of all cases of acute leukemia [1]. They include leukemias with no lineage specific antigens (acute undifferentiated leukemias) and those with blasts that express antigens of more than one lineage to such degree that it is not possible to assign the leukemia to any one particular lineage with certainty (mixed phenotype acute leukemias). The latter can either be leukemias with two distinct populations of blasts, each expressing antigens of a different lineage (historically referred to as "bilineal" leukemias) or a single blast population expressing antigens of multiple lineages (historically referred to as "biphenotypic" acute leukemias) [2]. Acute leukemias of ambiguous lineage may harbor a variety of genetic lesions. Those with t(9;22)(q34;q11) or translocations associated with mixed lineage leukemias (MLL) gene, i.e., t(11;V)(q23;V), occur frequently enough and are associated with distinct features, that are considered as separate entities according to the recent WHO classification. Co-expression of myeloid and B-lymphoid antigens is most common in mixed phenotype acute leukemia (MPAL), followed by co-expression of myeloid and T-lymphoid antigens, accounting for 66-70% and 23-24% of MLLs, respectively. Coexpression of B- and T-lineage associated antigens or antigens of all three lineages is exceedingly rare, accounting for <5% of MLLs [3,4]. The requirements for assigning more than one lineage to a single blast population has been established by current WHO classification [1].

Abstract 2097: microRNA profile and identification of miR-29 as a prognostic marker and pathogenetic factor by targeting CDK6 in mantle cell lymphoma

ABSTRACT: Mantle cell lymphoma (MCL) is one of the most aggressive B-cell lymphomas. While a number of protein-coding genes are altered, expression signature and importance of microRNA (miRNA) have not been well documented in this malignancy. Here, we performed miRNA expression profile in 30 patients with MCL using a platform containing 515 human miRNAs. Eighteen miRNAs were downregulated and 21 were upregulated in MCL when compared with normal B lymphocytes. The most frequently altered miRNAs are decrease of miR-29a/b/c, miR-142-3p/5p and miR-150 and increase of miR-124a and miR-155. Notably, expression levels of miR-29 family are associated with prognosis. The patients with significant downregulated miR-29 had short survival as compared to those who express relative high level of miR-29. Prognostic value of miR-29 is comparable with MIPI (MCL International Prognostic Index). Furthermore, we demonstrate miR-29 inhibition of CDK6 protein and mRNA levels by direct binding to 3′UTR. Inverse correlation between miR-29 and CDK6 was observed in MCL. Since cyclin D1 overexpression is a primary event and exerts its function through activation of CDK4/6, our results in primary MCL cells indicates that downregulation of miR-29 could cooperate with cyclin D1 in MCL pathogenesis. Thus, our findings provide not only miRNA expression signature but also a novel prognostic marker and pathogenetic factor for this malignancy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2097.

Reduced natural killer (NK) function associated with high-risk myelodysplastic syndrome (MDS) and reduced expression of activating NK receptors

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis with potential for progression to acute myeloid leukemia (AML). We compared natural killer (NK) cytolytic function in 48 MDS patients with 37 healthy donors and found reduced activity in the patient population (K562 cytolysis, 19% +/- 21% SD versus 40% +/- 17%) (P < .001). NK cytotoxicity in MDS patients was reduced against 3 disparate tumor targets with differential activating receptor requirement, suggesting global defects in NK function. Reduced NK function in MDS was significantly associated with higher International Prognostic Score (P = .01), abnormal karyotype (P = .05), the presence of excess blasts (P = .01), and age-adjusted bone marrow hypercellularity (P = .04). MDS patients had a display of the activating receptor NKp30, and NKG2D down-regulation closely correlated with impaired NK function (P = .001). NKG2D ligands (MICA and MICB) were expressed on CD34(+) cells from bone marrow of 30% of MDS patients and a leukemic cell line derived from an MDS patient (MDS1). Collectively, these findings suggest that impairment of NK cytolytic function derives in part from reduced activating NK receptors such as NKG2D in association with disease progression. Evasion of NK immunosurveillance may have importance for MDS disease progression.

“Virtual flow cytometry” of immunostained lymphocytes on microscopic tissue slides:iHCFlow™ tissue cytometry

BACKGROUND

A method and approach is developed for fully automated measurements of immunostained lymphocytes in tissue sections by means of digital color microscopy and patent pending advanced cell analysis. The validation data for population statistic measurements of immunostained lymphocytes in tissue sections using tissue cytometry (TC) is presented. The report is the first to describe the conversion of immunohistochemistry (IHC) data to a flow cytometry-like two parameter dot-plot display, hence the technique is also a virtual flow cytometry. We believe this approach is a paradigm shift, as well as novel, and called the system iHCFlow TC. Seven issues related to technical obstacles to virtual flow cytometry (FC) are identified.

DESIGN

Segmentation of a 512 x 474 RGB image and tabular display of statistical results table took 12-15 s using proprietary developed algorithms. We used a panel of seven antibodies for validation on 14 cases of mantle cell lymphoma giving percentage positive, total lymphocytes, and staining density. A total of 2,027 image frames with 810,800 cell objects (COBs) were evaluated. Antibodies to CD3, CD4, CD8, Bcl-1, Ki-67, CD20, CD5 were subjected to virtual FC on tissue. The results of TC were compared with manual counts of expert observers and with the results of flow cytometric immunophenotyping of the same specimen.

RESULTS

The correlation coefficient and 95% confidence interval by linear regression analysis yielded a high concordance between manual human results (M), FC results, and TC results per antibody, (r = 0.9365 M vs. TC, r= 0.9537 FC vs. TC). The technical issues were resolved and the solutions and results were evaluated and presented.

CONCLUSION

These results suggest the new technology of TC by iHCFlow could be a clinically valid surrogate for both M and FC analysis when only tissue IHC is available for diagnosis and prognosis. The application for cancer diagnosis, monitoring, and prognosis is for objective, rapid, automated counting of immunostained cells in tissues with percentage results. We report a new paradigm in TC that converts IHC staining of lymphocytes to automated results and a flow cytometry-like report. The dot plot histogram display is familiar, intuitive, informative, and provides the pathologists with an automated tool to rapidly characterize the staining and size distribution of the immunoreactive as well as the negative cell population in the tissue. This systems tool is a major improvement over existing ones and satisfies fully the criteria to perform Cytomics (Ecker and Tarnok, Cytometry A 2005;65:1; Ecker and Steiner, Cytometry A 2004;59:182-190; Ecker et al., Cytometry A 2004;59:172-181).

Superior activity of the combination of histone deacetylase inhibitor LAQ824 and the FLT-3 kinase inhibitor PKC412 against human acute myelogenous leukemia cells with mutant FLT-3

PURPOSE

Mutant FLT-3 receptor tyrosine kinase is a client protein of the molecular chaperone heat shock protein 90 and is commonly present and contributes to the leukemia phenotype in acute myelogenous leukemia (AML). LAQ824, a cinnamyl hydroxamate histone deacetylase inhibitor, is known to induce acetylation and inhibition of heat shock protein 90. Here, we determined the effects of LAQ824 and/or PKC412 (a FLT-3 kinase inhibitor) on the levels of mutant FLT-3 and its downstream signaling, as well as growth arrest and cell-death of cultured and primary human AML cells.

EXPERIMENTAL DESIGN

The effect of LAQ824 and/or PKC412 treatment was determined on the levels of FLT-3 and phosphorylated (p)-FLT-3, on downstream pro-growth and pro-survival effectors, e.g., p-STAT5, p-AKT, and p-extracellular signal-regulated kinase (ERK) 1/2, and on the cell cycle status and apoptosis in the cultured MV4-11 and primary AML cells with mutant FLT-3.

RESULTS

Treatment with LAQ824 promoted proteasomal degradation and attenuation of the levels of FLT-3 and p-FLT-3, associated with cell cycle G(1)-phase accumulation and apoptosis of MV4-11 cells. This was accompanied by attenuation of p-STAT5, p-AKT, and p-ERK1/2 levels. STAT-5 DNA-binding activity and the levels of c-Myc and oncostatin M were also down-regulated. Cotreatment with LAQ824 and PKC412 synergistically induced apoptosis of MV4-11 cells and induced more apoptosis of the primary AML cells expressing mutant FLT-3. This was also associated with more attenuation of p-FLT-3, p-AKT, p-ERK1/2, and p-STAT5.

CONCLUSIONS

The combination of LAQ824 and PKC412 is highly active against human AML cells with mutant FLT-3, which merits in vivo studies of the combination against human AML.

Combination of the histone deacetylase inhibitor LBH589 and the hsp90 inhibitor 17-AAG is highly active against human CML-BC cells and AML cells with activating mutation of FLT-3

Present studies show that LBH589, a novel cinnamic hydroxamic acid analog histone deacetylase inhibitor, induces acetylation of histone H3 and H4 and of heat shock protein 90 (hsp90), increases p21 levels, as well as induces cell-cycle G(1) phase accumulation and apoptosis of the human chronic myeloid leukemia blast crisis (CML-BC) K562 cells and acute leukemia MV4-11 cells with the activating length mutation of FLT-3. In MV4-11 cells, this was associated with marked attenuation of the protein levels of p-FLT-3, FLT-3, p-AKT, and p-ERK1/2. In K562 cells, exposure to LBH589 attenuated Bcr-Abl, p-AKT, and p-ERK1/2. Treatment with LBH589 inhibited the DNA binding activity of signal transducers and activators of transcription 5 (STAT5) in both K562 and MV4-11 cells. The hsp90 inhibitor 17-allyl-amino-demethoxy geldanamycin (17-AAG) also induced polyubiquitylation and proteasomal degradation of FLT-3 and Bcr-Abl by reducing their chaperone association with hsp90. Cotreatment with LBH589 and 17-AAG exerted synergistic apoptosis of MV4-11 and K562 cells. In the imatinib mesylate (IM)-refractory leukemia cells expressing Bcr-Abl with the T315I mutation, treatment with the combination attenuated the levels of the mutant Bcr-Abl and induced apoptosis. Finally, cotreatment with LBH589 and 17-AAG also induced more apoptosis of IM-resistant primary CML-BC and acute myeloid leukemia (AML) cells (with activating mutation of FLT-3) than treatment with either agent alone.

Cotreatment with histone deacetylase inhibitor LAQ824 enhances Apo-2L/tumor necrosis factor-related apoptosis inducing ligand-induced death inducing signaling complex activity and apoptosis of human acute leukemia cells

Present studies demonstrate that treatment with the histone deacetylases inhibitor LAQ824, a cinnamic acid hydroxamate, increased the acetylation of histones H3 and H4, as well as induced p21(WAF1) in the human T-cell acute leukemia Jurkat, B lymphoblast SKW 6.4, and acute myelogenous leukemia HL-60 cells. This was associated with increased accumulation of the cells in the G(1) phase of the cell cycle, as well as accompanied by the processing and activity of caspase-9 and -3, and apoptosis. Exposure to LAQ824 increased the mRNA and protein expressions of the death receptors DR5 and/or DR4, but reduced the mRNA and protein levels of cellular FLICE-inhibitory protein (c-FLIP). As compared with treatment with Apo-2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or LAQ824 alone, pretreatment with LAQ824 increased the assembly of Fas-associated death domain and caspase-8, but not of c-FLIP, into the Apo-2L/TRAIL-induced death-inducing signaling complex. This increased the processing of caspase-8 and Bcl-2 interacting domain (BID), augmented cytosolic accumulation of the prodeath molecules cytochrome-c, Smac and Omi, as well as led to increased activity of caspase-3 and apoptosis. Treatment with LAQ824 also down-regulated the levels of Bcl-2, Bcl-x(L), XIAP, and survivin. Partial inhibition of apoptosis due to LAQ824 or Apo-2L/TRAIL exerted by Bcl-2 overexpression was reversed by cotreatment with LAQ824 and Apo-2L/TRAIL. Significantly, cotreatment with LAQ824 increased Apo-2L/TRAIL-induced apoptosis of primary acute myelogenous leukemia blast samples isolated from 10 patients with acute myelogenous leukemia. Taken together, these findings indicate that LAQ824 may have promising activity in augmenting Apo-2L/TRAIL-induced death-inducing signaling complex and apoptosis of human acute leukemia cells.

Cotreatment with 17-Allylamino-Demethoxygeldanamycin and FLT-3 Kinase Inhibitor PKC412 Is Highly Effective against Human Acute Myelogenous Leukemia Cells with Mutant FLT-3

Presence of the activating length mutation (LM) in the juxtamembrane domain or point mutation in the kinase domain of FMS-like tyrosine kinase-3 (FLT-3) mediates ligand-independent progrowth and prosurvival signaling in approximately one-third of acute myelogenous leukemia (AML). PKC412, an inhibitor of FLT-3 kinase activity, is being clinically evaluated in AML. Present studies demonstrate that treatment of human acute leukemia MV4-11 cells (containing a FLT-3 LM) with the heat shock protein 90 inhibitor 17-allylamino-demethoxy geldanamycin (17-AAG) attenuated the levels of FLT-3 by inhibiting its chaperone association with heat shock protein 90, which induced the poly-ubiquitylation and proteasomal degradation of FLT-3. Treatment with 17-AAG induced cell cycle G(1) phase accumulation and apoptosis of MV4-11 cells. 17-AAG-mediated attenuation of FLT-3 and p-FLT-3 in MV4-11 cells was associated with decrease in the levels of p-AKT, p-ERK1/2, and p-STAT5, as well as attenuation of the DNA binding activity of STAT-5. Treatment with 17-AAG, downstream of STAT5, reduced the levels of c-Myc and oncostatin M, which are transactivated by STAT5. Cotreatment with 17-AAG and PKC412 markedly down-regulated the levels of FLT-3, p-FLT-3, p-AKT, p-ERK1/2, and p-STAT5, as well as induced more apoptosis of MV4-11 cells than either agent alone. Furthermore, the combination of 17-AAG and PKC412 exerted synergistic cytotoxic effects against MV4-11 cells. Importantly, 17-AAG and PKC412 induced more loss of cell viability of primary AML blasts containing FLT-3 LM, as compared with those that contained wild-type FLT-3. Collectively, these in vitro findings indicate that the combination of 17-AAG and PKC412 has high level of activity against AML cells with FLT-3 mutations.

Genotypic and phenotypic comparisons of de novo and acquired melphalan resistance in an isogenic multiple myeloma cell line model

Cancer cell adhesion confers a transient, de novo drug-resistant phenotype referred to as cell adhesion-mediated drug resistance (CAM-DR). In this report, we extend the CAM-DR phenotype to primary specimens from patients with myeloma, providing further evidence that CAM-DR is a viable clinical form of drug resistance. To examine mechanisms of cellular resistance to melphalan, we compared genotypic and phenotypic profiles of acquired and de novo melphalan resistance in an isogenic human myeloma cell line. Acquired melphalan resistance (8226/LR5) was associated with decreased drug-induced DNA damage and a complex gene expression profile showing that genes involved in the Fanconi anemia DNA repair pathway are increased in the LR5 cells compared with drug-sensitive or adherent cells. In contrast, cells adhered to fibronectin accumulate similar amounts of DNA damage compared with drug-sensitive cells but are protected from melphalan-induced mitochondrial perturbations and caspase activation. Levels of the proapoptotic protein Bim were significantly reduced in adherent cells. Gene expression changes associated with de novo resistance were significantly less complex compared with acquired resistance, but a significant overlap in gene expression was noted involving cholesterol synthesis. We propose that myeloma cell adhesion promotes a form of de novo drug resistance by protecting cells from melphalan-induced cytotoxic damage and that this transient protection allows cells to acquire a more permanent and complex drug resistance phenotype associated with a reduction in drug induced DNA damage.

Histone deacetylase inhibitor LAQ824 both lowers expression and promotes proteasomal degradation of Bcr-Abl and induces apoptosis of imatinib mesylate-sensitive or -refractory chronic myelogenous leukemia-blast crisis cells

Treatment with LAQ824 (Novartis Pharmaceutical, Inc.), a cinnamyl hydroxamic acid analogue inhibitor of histone deacetylases, depleted the mRNA and protein expression of Bcr-Abl in human chronic myeloid leukemia blast crisis (CML-BC) cells. Exposure to LAQ824 induced the expression of the cell cycle-dependent kinase inhibitors p21 and p27 and caused cell cycle G(1)-phase accumulation and apoptosis of CML-BC cells. LAQ824 also induced acetylation of heat shock protein 90. This inhibited the chaperone association of Bcr-Abl with heat shock protein 90, thereby promoting the proteasomal degradation of Bcr-Abl. Cotreatment with LAQ824 increased imatinib mesylate-induced apoptosis of CML-BC cells. Additionally, LAQ824 down-regulated the levels of mutant Bcr-Abl possessing the T315I point mutation, as well as induced apoptosis of imatinib-refractory primary CML-BC cells. Therefore, LAQ824 may be a promising therapeutic agent in the treatment of imatinib-sensitive or -refractory human leukemia.

Inhibition of Bcr-Abl kinase activity by PD180970 blocks constitutive activation of Stat5 and growth of CML cells

Chronic myelogenous leukemia (CML) is a myeloproliferative disease characterized by the BCR-ABL genetic translocation and constitutive activation of the Abl tyrosine kinase. Among members of the Signal Transducers and Activators of Transcription (STAT) family of transcription factors, Stat5 is activated by the Bcr-Abl kinase and is implicated in the pathogenesis of CML. We recently identified PD180970 as a new and highly potent inhibitor of Bcr-Abl kinase. In this study, we show that blocking Bcr-Abl kinase activity using PD180970 in the human K562 CML cell line resulted in inhibition of Stat5 DNA-binding activity with an IC(50) of 5 nM. Furthermore, abrogation of Abl kinase-mediated Stat5 activation suppressed cell proliferation and induced apoptosis in K562 cells, but not in the Bcr-Abl-negative myeloid cell lines, HEL 92.1.7 and HL-60. Dominant-negative Stat5 protein expressed from a vaccinia virus vector also induced apoptosis of K562 cells, consistent with earlier studies that demonstrated an essential role of Stat5 signaling in growth and survival of CML cells. RNA and protein analyses revealed several candidate target genes of Stat5, including Bcl-x, Mcl-1, c-Myc and cyclin D2, which were down-regulated after treatment with PD180970. In addition, PD180970 inhibited Stat5 DNA-binding activity in cultured primary leukemic cells derived from CML patients. To detect activated Stat5 in CML patient specimens, we developed an immunocytochemical assay that can be used as a molecular end-point assay to monitor inhibition of Bcr-Abl signaling. Moreover, PD180970 blocked Stat5 signaling and induced apoptosis of STI-571 (Gleevec, Imatinib)-resistant Bcr-Abl-positive cells. Together, these results suggest that the mechanism of action of PD180970 involves inhibition of Bcr-Abl-mediated Stat5 signaling and provide further evidence that compounds in this structural class may represent potential therapeutic agents for CML.

CD95 antigen mutations in hematopoietic malignancies

The CD95 receptor, also known as Fas/Apo-1, is a member of the Tumor Necrosis Factor receptor (TNF-R) family of death receptors. Apoptosis mediated by CD95 plays a central role in maintaining homeostasis of the immune system. Dysregulation of the CD95 apoptotic pathway has been proposed as a mechanism of oncogenesis by providing a survival advantage to potentially malignant cells. This extended lifespan could allow the accumulation of further mutations leading to malignant transformation. Several mechanisms of resistance to CD95 mediated apoptosis have been identified, including reduced surface expression of the receptor, overexpression of anti-apoptotic molecules, and loss of function mutations. This review will focus on the potential role of the CD95-CD95 ligand system in the pathogenesis of hematological malignancies, with particular emphasis on recent work from our laboratory examining the expression of CD95 in B cell lymphomas. We demonstrate that CD95 mutations occur at low frequency in NHL tumors, however, surface expression of the CD95 protein varies with the subtype of lymphoma. Loss of surface CD95 is more likely to occur in lymphomas of aggressive histology, and is unrelated to the detection of CD95 mutations.

Constitutive activation of Stat3 signaling confers resistance to apoptosis in human U266 myeloma cells

Interleukin 6 (IL-6) is the major survival factor for myeloma tumor cells and induces signaling through the STAT proteins. We report that one STAT family member, Stat3, is constitutively activated in bone marrow mononuclear cells from patients with multiple myeloma and in the IL-6-dependent human myeloma cell line U266. Moreover, U266 cells are inherently resistant to Fas-mediated apoptosis and express high levels of the antiapoptotic protein Bcl-xL. Blocking IL-6 receptor signaling from Janus kinases to the Stat3 protein inhibits Bcl-xL expression and induces apoptosis, demonstrating that Stat3 signaling is essential for the survival of myeloma tumor cells. These findings provide evidence that constitutively activated Stat3 signaling contributes to the pathogenesis of multiple myeloma by preventing apoptosis.

Non-Hodgkin's lymphoma in the older person: a review

OBJECTIVE

To study the epidemiology of non-Hodgkin's Lymphoma (NHL) in the older person and to explore treatment strategies for older persons with NHL.

DESIGN

Review of the English literature.

MEASUREMENTS

Incidence of NHL in patients of different ages; prevalence of NHL of different grades and stages in persons of different ages; and response to treatment, disease free survival, and survival, for patients of different ages.

RESULTS

The incidence of NHL in the aged has increased approximately 80% since 1970, and approximately one-half of the 40,000 annual new cases occur in persons aged 60 and older in the USA. The 2-4 phenoxy pesticides may be partly responsible for this increment. The treatment of low grade lymphoma is mostly palliative and well tolerated by the aged. Age may have an adverse effect on the prognosis of intermediate grade lymphomas, and the prevalence of poor prognostic factors and comorbidity increases with age. Among persons aged 65-75, the complete response rate (CRR) of intermediate grade NHL to chemotherapy is approximately 50%, and approximately one-third of complete responders remain alive and free of disease 5 years from diagnosis. Among those aged 75 and older, the CRR to chemotherapy is approximately 40%, and the median duration of response is 16 months. Strategies aimed to ameliorate treatment-related toxicity include lower doses of chemotherapy, choice of drugs better tolerated by older individuals, and prevention of chemotherapy-induced toxicity.

CONCLUSIONS

NHL are an increasingly common problem for older persons. Approximately 80% of older patients with low grade lymphomas and 40%-50% of those with intermediate grade lymphomas may benefit from chemotherapy. Individualized treatment, based on life expectancy and comorbidity, is the key to effective management.