Lymphoid Leukemia Cells Research Articles

Effect of Notch ligands on in vitro sensitivity to chemo-therapeutic drugs in leukemia and lymphoma cells

The effect of the recombinant Notch ligand proteins Jagged1 and Delta1 on drug-sensitivity of leukemia and lymphoma cells was examined. Four acute myeloid leukemia (AML) cell lines were cultured in ligand-coated wells and control wells, with cytosine arabinoside (Ara-C), doxorubicin, or mitoxantrone, and nine lymphoid leukemia or lymphoma cell lines were cultured with dexamethasone. The growth was evaluated with a colorimetric assay. The drug-induced growth suppression was slightly reduced by the ligand stimulation in 4 out of 17 combinations of cells versus drugs, such as NB4 cells versus Ara-C. In the remainder, the ligands did not significantly affect the drug-sensitivity. To investigate the possible molecular mechanism of the protective effect, the influence of Jagged1 on Ara-C-induced activation of caspase-3 and PARP, and dephosphorylation of NF-kappaB was examined in NB4 cells. However, Jagged1 did not obviously affect the activation and dephosphorylation. It is known that stromal cells reduce drug-induced cytotoxicity of leukemia cells. According to our results, the role of Notch ligands in the stroma-mediated resistance seems to be minor and occurs only in a limited context. However, the ligand-coated culture-plates are more similar to the microenvironment in human bone marrow than ordinary plates. We will further examine the clinical usefulness of the drug-sensitivity test using the ligand-coated plates.

Preclinical evaluation of apoptosis induction by the novel small molecule BCL-2 inhibitor, GX015–070, in ex vivo chronic lymphoid leukemia (CLL) cells

3149 Background: CLL is associated with loss of normal cellular apoptotic function. Apoptosis in cell lines has been identified with GX015–070 (GX), a small molecule antagonist of the BH3-binding groove of the BCL-2 family of proteins which is frequently overexpressed in cancers including CLL. This study evaluated GX induced apoptosis in CLL cells ex vivo correlating it with prognostic factors. Methods: Circulating lymphocytes were collected from patients (pts) with ≥ 20x109/L lymphocytes with no CLL treatment or red cell transfusions within 4 wks. Medical history was recorded. The diagnosis was confirmed with immunophenotyping by flow cytometry. CD38 was assessed in this analysis. The cytogenetic abnormalities del(11q), +12, del(13)(q14.3), del(13)(q34) & del(17p) were established by fluorescent in situ hybridization. Apoptosis was assessed with surface annexin V immunophenotyping in B cell enriched samples with positive glucocorticoid and negative DMSO controls. Results: 30 pts were recruited including 67% men with median age of 65 yrs (range 43–83). Rai stages were 6 stage 0; 8 stage 1; 6 stage 2; 4 stage 3; and 6 stage 4. Median lymphocyte count was 37.6x109/L (19.4–204.5). Prior treatment included 0–4 regiments (median 0). Previous treatments were alkylating agents (13%), purine analogues (13%), both (13%) and campath after both (3%). 33% of pts (n=10) expressed CD38. Cytogenetic analysis showed no abnormalities in 20%, del(11q) in 17%, +12 in 10%, -12 in 3%, del(13)(q14.3) in 53%, del(13)(q34) in 3% and no del(17p). ≥ 1 abnormality was seen in 4 pts. Apoptosis testing was performed and controls appropriate in 28 samples. All (100%) had significant early apoptosis with GX. A dose response to GX was found in all pts. The greatest % of annexin positive cells was observed at 6 hrs with 5 uM. In the last 12 pts, rescue from early apoptosis induction with IL-4 was observed in all glucocorticoid treated but in none of the GX treated cells. Conclusions: GX results in early and vigorous induction in vitro apoptosis of CLL cells. This population had both good & poor prognostic clinical factors. GX is one of the few agents where IL-4 co-treatment does not inhibit the induction of apoptosis. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration GeminX, GeminX Biotech

Enhancement of antineoplastic action of 5-aza-2???-deoxycytidine by zebularine on L1210 leukemia

Tumor suppressor genes that have been silenced by aberrant DNA methylation are potential targets for reactivation by novel chemotherapeutic agents. The potent inhibitor of DNA methylation and antileukemic agent, 5-aza-2'-deoxycytidine (5-AZA-CdR, Decitabine), can reactivate silent tumor suppressor genes. One hindrance to the curative potential of 5-AZA-CdR is its rapid in vivo inactivation by cytidine deaminase (CD). An approach to overcome this obstacle is to use 5-AZA-CdR in combination with zebularine (Zeb), a potent inhibitor of CD. Zeb also possesses independent antineoplastic activity due to its inhibition of DNA methylation. We tested the capacity of 5-AZA-CdR and Zeb alone and in combination to inhibit growth and colony formation of different leukemic cell lines. 5-AZA-CdR and Zeb in combination produced a greater inhibition of growth against murine L1210 lymphoid leukemic cells, and a greater reduction in colony formation by L1210 and human HL-60 myeloid leukemic cells, than either agent alone. The ability of these agents to reactivate the tumor suppressor gene, p57KIP2, was also tested using RT-PCR. The combination produced a synergistic reactivation of p57KIP2 in HL-60 leukemic cells. A methylation-specific PCR assay showed that this combination also induced a significantly greater demethylation level of the p57KIP2 promoter than either drug alone. The in vivo antineoplastic activity of the agents was evaluated in mice with L1210 leukemia. A greater increase in survival time of mice with L1210 leukemia was observed with the combination than with either agent alone using three different dose schedules. The enhanced activity observed with 5-AZA-CdR plus Zeb in both murine and human leukemic cells lines provides a rationale for the clinical investigation of these drugs in patients with advanced leukemia. The probable mechanism of this drug interaction involves inhibition of CD by Zeb and the complementary inhibition of DNA methylation by both agents.

High avidity cyclin E1-derived peptide-specific CTL kill lymphoid leukemia cells and cross-recognize a homologous cyclin E2-derived peptide

Using a similar strategy that was used to identify PR1 as a leukemia-associated antigen (LAA), we identified two homologous HLA-A2-restricted peptides from cyclin E1 (CCNE1M) and cyclin E2 (CCNE2L) that could be used to elicit peptide-specific CTL from healthy donors. The two peptides differ by a single amino acid at position 7 and have equal binding affinity for HLA-A2, and each elicited peptide-specific CTL with equal efficiency. Because each CCNE1M- and CCNE2L-CTL clone, derived from limiting dilution, cross-recognized the other homologous peptide, we hypothesized that each clone would efficiently kill leukemia that over-expressed either or both CCNE1 and CCNE2 proteins.

Preclinical studies on NSC290205 aza‐steroid alkylator activity in combination with adriamycin against lymphoid leukaemia

Summary NSC290205 (A) is an hybrid synthetic antineoplastic ester that is a combination of a d-lactam derivative of androsterone and an alkylating derivative of N,N-bis(2-chloroethyl)aniline. We tested NSC290205 for synergistic antileukaemic activity with adriamycin (ADR), (i) in vitro against the human lymphoid leukaemia cell lines: CCRF-CEM, MOLT-4, and RPMI-8226, (ii) in vivo against P388 lymphocytic and L1210 lymphoid murine leukaemias (at incipient and advanced phase). Our results indicated significant cytostatic and cytotoxic synergy of NSC290205 and ADR in vitro. We further examined these results in vivo by replacing cyclophosphamide in the standard CHOP (cyclophosphamide, hydroxydaunomycin, Oncovin, prednisone) regimen with NSC290205 (AHOP) and comparing the efficiency of these two regimens in vivo. Although treatment of P388 and L1210 with cyclophosphamide or NSC290205 alone yielded equivalent results, AHOP produced a clear benefit for survival compared with CHOP against advanced leukaemias, confirming the in vitro observations [higher percentage increase in median lifespan of treated animals over the untreated (control): 188% and 239% in L1210, 308% and 353% in P388, P < 0.01, for CHOP and AHOP respectively]. AHOP also proved to be more genotoxic and cytostatic than CHOP, inducing higher sister chromatid exchange levels and cell division delays on P388 cells in vivo. NSC290205 showed superior antineoplastic potential against lymphoid leukaemia and significant synergy with ADR, producing an excellent therapeutic outcome.

Mutations Required for Lymphoid Leukemogenesis Are Not Required for c-Myc to Rapidly Induce Acute Myeloid Leukemia.

Dysregulation of c-Myc is one of the critical oncogenic events required for tumorigenesis in many tissue types. Although c-Myc has been shown to block differentiation of leukemic and normal myeloid cells and is activated by oncogenes commonly found in leukemia, its exact role in myeloid leukmogenesis remains elusive. When c-Myc is over-expressed in the lymphoid compartment, Eμ-Myc transgenic mice develop B-cell lymphomas only after a prolonged latency and require additional mutations to inhibit apoptosis, most commonly by disrupting the Arf-Mdm2-p53 pathway. Although this model has been well used to dissect pathways of Myc-induced lymphomagenesis, there is currently no efficient model with which to study the role of c-Myc in AML. In this study, we utilized a retroviral gene transfer system (MSCV-Myc) to introduce c-Myc into unfractionated murine bone marrow that was subsequently transplanted into syngeneic mice. Surprisingly, 100% of transplanted mice (N=110) from three different strains, developed acute myeloblastic leukemia (AML) characterized by rapid onset, hemiparesis, splenomegaly and infiltration of the marrow and spleen with myeloblasts. c-Myc protein level was comparable to the Eμ-Myc tumors. Disease latency was short (median survival=38 days). MSCV-Myc-induced tumors were oligoclonal, did not display significant cytogenetic abnormalities by SKY analysis, and were exclusively of myeloid origin. These tumors contained germline configuration of the Ink4A locus and wild type coding region of the p53, Arf and Ink4a. Also, the p53 target gene p21 in Myc expressing cells responded normally to gamma irradiation. These data demonstrate that c-Myc induced AML development without disrupting the Arf-p53 pathway and suggest that cooperating mutations were not required for the development of AML. In contrast, using the same retroviral system, lymphoid leukemia developed only if c-Myc and Bcl-2 were co-expressed or if Ink4a was mutated. Tumors from Bcl-2/c-Myc transplanted mice were comprised of a mixture of myeloid and lymphoid leukemic cells. Similarly, mice transplanted with c-Myc transduced Ink4a−/− bone marrow developed leukemia that displayed a mixed phenotype of myeloid and lympoid lineages. Lastly, factor independent methylcellulose colonies induced by Myc were exclusively of myeloid lineage suggesting as intrinsic difference between myeloid and lymphoid cells in response to Myc. Our data imply that dysregulation of c-Myc is sufficient to induce AML and provide direct evidence that Myc is an important downstream target in myeloid leukemogenesis.

Triptolide-Induced Apoptosis Is Dependent on Caspase Activation and NFκB Signaling and Mediated by XIAP and Survivin Downregulation through the Mitochondrial Pathway in Leukemic Cells.

Triptolide, an immunosuppressor isolated from the Chinese herb, Tripterygium wilfordii Hook. F, has recently shown anti-tumor activities in a broad range of solid tumors. We examined its effects on leukemic cells and investigated mechanisms of apoptosis. Triptolide, at less than 100 nM, arrested cell growth and potently induced cell death in myeloid and lymphoid leukemic cells tested, including OCI-AML3, U937, Jurkat, KBM5, and K562 cells. In OCI-AML3 cells, triptolide induced caspase 3 activation, PARP cleavage and annexin V positivity with an IC50 of about 30 nM, at 24 hrs, all of which were inhibited by a general caspase inhibitor suggesting caspase dependent cell death. However, Triptolide-induced cell growth arrest was not affected by caspase inhibition. Treatment of OCI-AML3 cells with triptolide decreased XIAP and survivin expression, but did not affect Bcl2 and BclXL levels. Forced overexpression of XIAP attenuated Triptolide-induced cell death. Triptolide induced Bid cleavage, but Jurkat cells deficient in caspase 8 were only slightly less sensitive to triptolide than the wild-type counterpart indicating that Triptolide-induced cell death is caspase 8 independent. Jurkat cells deficient in receptor interacting protein (RIP) and therefore deficient in NFκB activation were resistant to Triptolide demonstrating that NFκB signaling is essential for Triptolide-induced cell death. Triptolide treatment induced cytosolic release of cytochrome C and loss of mitochondrial membrane potential, overexpression of Bcl2 effectively suppressed apoptosis induced by Triptolide, and caspase 9 knockout MEF cells were resistant to Triptolide suggesting criticality of the mitochondrial pathway. The antioxidants GSH (5 mM) and vitamin C (150 μM) did not protect from apoptotic cell death induced by Triptolide. In addition, Triptolide-induced apoptosis of blast crisis CML KBM5 cells was independent of their sensitivity or resistance to Imatinib: Triptolide killed Imatinib resistant KBMSTI cells as effectively as Imatinib sensitive KBM5 cells. Ex vivo studies showed that Triptolide also induced cell death in primary AML blasts. Collectively, our studies demonstrate that Triptolide potently induces caspase-dependent apoptosis and arrests cell growth in leukemic cells. Triptolide-induced cell death is dependent on NFκB signaling, and mediated by downregulation of XIAP and survivin through the mitochondrial pathway. The potent anti-leukemic activity of Triptolide in vitro warrants further investigation of this compound for the treatment of leukemia and other malignancies. This drug may also be potentially useful in overcoming Imatinib resistance in CML and Philadelphia chromosome positive ALL.

Preclinical Investigations Demonstrate Effectiveness of Aplidin in Acute Leukemias and Lymphomas and Provide the Basis for Further Clinical Studies.

Aplidin (dehydrodidemnin B, C57H89N7O15) (APLD) is a novel antitumor agent isolated from the Mediterranean tunicate (seasquirt) Aplidium albicans. APLD has shown impressive in vitro and in vivo activity against different human cancer cells and has recently entered Phase II clinical trials in a variety of solid tumors following promising toxicity and pharmacological properties seen in Phase I studies. Fatigue and muscular pain were the most prevalent toxicities at 5 mg/m2 iv 3 h every other week or 3.4 mg/m2/wk with little or no bone marrow toxicity. APLD inhibits protein synthesis via GTP-dependent elongation factors 1-alpha and ornithine decarboxylase (ODC) activity, induces rapid p53-independent apoptosis in vitro, cell cycle perturbation and alteration of gene expression at early times after treatment. APLD inhibits vascular endothelial growth factor (VEGF) secretion and vascular endothelial growth factor-receptor 1 (VEGF-R1/flt-1), preventing autocrine stimulation in the human lymphoid leukemic cell line MOLT-4 cells and in AML blasts. APLD is a potent inhibitor of human myeloid leukemia cell lines (K-562, HEL and HL60), as well as fresh blast cells obtained from patients with both ALL and AML and is more potent than Idarubicin. Cytototoxic doses effective against multiple myeloma cells and fresh pediatric and adult ALL/AML blasts are achievable in plasma and are well below the recommended dose, thus a positive therapeutic index is anticipated. Moreover, the lack of cross resistance with conventional agents against fresh pediatric and adult AML/ALL blasts except fludarabine and Gemcitabine makes APLD an attractive therapeutic choice. Characterization of gene expression profile is currently underway in an attempt to generate a molecular fingerprint of sensitivity/resistance to APLD that will be validated in phase II clinical studies. Based on in vitro antileukemic effect of APLD as well as early results of clinical trials, a systematic study of drug combinations with Aplidin (APLD), for use possible in hematologic malignancies was undertaken. Three cell lines viz. K562 (acute myeloid leukemia), CCRF-CEM (acute lymphocytic leukemia), and SKI-DLCL (diffuse large cell lymphoma) were used for combination studies. Cytarabine and mitoxantrone were found to be synergistic in combination with APLD in all 3 cell lines as assessed by the Chou-Talalay combination index analysis. Since cytarabine and APLD produced impressive synergistic cell kill in all three cell culture models, the combination was further tested in the CCRF-CEM ALL xenograft model in SCID mice. APLD (0.7 mg/Kg) potentiated the antitumoral effect of cytarabine (50mg/Kg) in vivo. Addition of APLD to cytarabine treatment in xenograft model resulted in greater than 50% reduction in tumor size as compared to the untreated group. T/C ratios indicated that the effect of the combination was maximal at day 5 but was still maintained on day 8 (T/C on day 3 = 0.614; day 5= 0.403 and day 8= 0.703). The preclinical results with APLD in leukemias and lymphomas, as a single agent and in combination with cytarabine provide the basis for implementation of a phase II program in resistant relapsed leukemias and lymphomas.

Triterpenoid Methyl-CDDO Is a Potent Inducer of Apoptosis in CD34+ AML Progenitor Cells Via Activation of SAPK Pathways and Inhibition of MAPK Cascades.

Outcome results in AML are a continued challenge for the development of novel therapeutic strategies. C-28 methyl ester of 2-cyano-3,12-dioxoolen-1,9-dien-28-oic acid, CDDO-Me, a novel triterpenoid, induces apoptosis in myeloid and lymphoid leukemic cell lines and in primary AML samples in sub-micromolar concentrations. We reported previously that CDDO-Me inhibits the activation of ERK1/2, blocks Bcl-2 phosphorylation, and promoted apoptosis in AML-derived U937 cells (Blood 2002, 99(1):326–35). Here, we examined the effects of CDDO-Me on CD34+ AML progenitor cells in vitro. Exposure to 1μM CDDO-Me induced apoptosis in all but one AML sample (46±4% annexin(+) CD34+ cells, n=20). To assess the anti-leukemia activity of CDDO-Me in vivo, scid mice intravenously injected with U937 cells were treated with liposomally-delivered CDDO-Me (20mg/kg/day IV every other day, starting at day 7, for a total of 9 injections). While CDDO-Me was not toxic to the mice, pathological and flow cytometry analysis revealed reduced (55–86%) leukemia burden in the bone marrow, liver, and spleen of mice. Since we had shown that CDDO-Me inhibits phosphorylation of pERK in U937 cells, a further goal of this study was to assess the role of ERK in CDDO-Me-induced cell death in primary AML samples. ERK was expressed and phosphorylated in all (n=15) patients' samples studied. CDDO-Me inhibited ERK phosphorylation in 9 of 15 patient samples and promoted apoptosis. However, CDDO-Me still induced apoptosis in 5/6 samples that displayed no significant changes in pERK levels in response to the drug. This finding suggests that ERK is not the sole target of the compound. The stress-activated protein kinases JNK and p38 are related to ERK but in general activate pathways that are opposed to ERK. By Western blot analysis, CDDO-Me induced early (30 min) phosphorylation of JNK and p38, which preceded induction of cell death. Pre-treatment of U937 cells with JNK and p38 inhibitors SP600125 and SB203580 partially abrogated induction of apoptosis, while MEK inhibitor PD-98059 significantly enhanced cytotoxicity. CDDO-Me induced p38 phosphorylation in 5 of 6 primary AML samples tested. Collectively, these finding indicate that CDDO-Me markedly shifts signaling toward the JNK and p38 MAPK stress-related pathways and away from the cytoprotective MAPK cascade. In summary, the triterpenoid CDDO-Me is a potent inducer of apoptosis in primary AML including CD34+ AML progenitor cells. Induction of apoptosis is in part mediated via inhibition of ERK signaling combined with JNK/p38 activation. These studies in primary AML samples and the anti-leukemia activity of the compound in vivo suggest potential utility of CDDO-Me for the treatment of AML patients.

High Avidity Cyclin E1-Derived Peptide-Specific CTL Kill Lymphoid Leukemia Cells and Cross-Recognize a Homologous Cyclin E2-Derived Peptide.

Using a similar strategy that successfully identified PR1 as a leukemia-associated antigen (LAA), we identified two homologous HLA-A2-restricted peptides from cyclin E1 (CCNE1) and cyclin E2 (CCNE2) that could be used to elicit peptide-specific CTL from healthy donors in vitro. Two homologous nonameric peptides from CCNE1 (CCNE1144–152) and CCNE2 (CCNE2144–152), which differ by a single amino acid at position 7, have equal binding affinity for HLA-A2 and each elicited peptide-specific CTL with equal efficiency, as measured by specific lysis of T2 cells pulsed with either peptide (CCNE1 59.7% vs CCNE2 72.6% specific lysis, respectively, at E: T 10:1). TCR-Vβ spectratype analysis showed CCNE1-CTL clones to be derived from 3 Vβ families, while CCNE2-CTL clones were derived from a single Vβ family. The CCNE1-CTL and the CCNE2-CTL bound to each of the CCNE1/A2 and CCNE2/A2 tetramers, but staining intensity was greater for the CCNE1-CTL, suggesting greater TCR avidity of the CCNE1-CTL for both peptides. Because each clone cross-recognized the other homologous peptide, we hypothesized that each clone would efficiently kill leukemia that over-expressed either or both CCNE1 and CCNE2 proteins. FACsorted high avidity CTL showed higher specific lysis of peptide-pulsed T2 than did low avidity CTL (38.8% vs 31.9% specific lysis, respectively, at E: T 10:1, p = 0.02). The fluorescence decay of tetramer dissociation (ln (peptide/HLA-A2 tetramer)) over time was linear for each clone, suggesting that avidity was proportional to TCR affinity and tetramer dissociation t1/2 was determined based on first order kinetics. CCNE1-CTL had higher affinity for CCNE1144–152/HLA-A2 (CCNE1/A2, t1/2=84.5min; CCNE2/A2, t1/2=25.3min) and preferentially killed CCNE1144–152-pulsed T2 cells (CCNE1, 56.9% vs CCNE2, 38%, respectively, at E: T 10:1, p = 0.004). Interestingly, CCNE2-CTL also had higher TCR affinity for CCNE1144–152/HLA-A2 (CCNE1/A2, t1/2=29.5min; CCNE2/A2, t1/2=10.7min), but showed only slightly higher specific lysis of CCNE1144–152-pulsed T2 cells (CCNE1 = 49.3% vs CCNE2 = 44.2% specific lysis, respectively, at E: T 10:1, p = 0.33). Each clone specifically lysed HLA-A2+ T-ALL leukemia cells in proportion to both CCNE1 and CCNE2 protein overexpression assessed by Western blot (CCNE1-CTL, R2=0.89; CCNE2-CTL, R2=0.88). In contrast, healthy HLA-A2+ BM cells, which do not overexpress CCNE1 or CCNE2, and control HLA-A2− CML cells that overexpress both proteins, were not lysed. Both the high and low affinity clones showed equal lysis of T-ALL cells that expressed large amounts of each protein (specific lysis = 24.3% by CCNE1-CTL, vs lysis = 23.8% by CCNE2-CTL, at E: T 10:1). However, high affinity CCNE1-CTL killed T-ALL cells significantly better than low affinity CCNE2-CTL (16.8% vs 6.6% lysis, respectively, at E: T 10:1, p =0.02) when the T-ALL expressed a 2.5-fold lower amount of both CCNE1 and CCNE2 proteins. We conclude that the CCNE1 and CCNE2 homologous self-peptides are lymphoid leukemia-associated antigens. Furthermore, while the higher TCR affinity of CCNE1-CTL suggests that the CCNE1 peptide is the more dominant epitope, ultimate target susceptibility is enhanced due to degeneracy of the resulting CTL clones against homologous peptide epitopes.

Transcriptional Activation of the Cardiac Homeobox Gene CSX1/NKX2-5 in a B-Cell Chronic Lymphoproliferative Disorder.

Transcription deregulation resulting from genomic rearrangement is frequently observed in human lymphoid malignancies. For example, chromosomal aberrations, such as translocations or inversions, involving the immunoglobulin (Ig), T cell receptor (TCR) and the BCL11B loci, are expected to juxtapose the strong regulatory elements of these genes to the affected genes on the other chromosomes, resulting in such activation. Recently, ectopic activation of two orphan homeobox genes located ~2Mb apart on chromosome 5q35, HOX11L2/TLX3 and CSX1/NKX2-5 have been described, as a result of their fusion to BCL11B on chromosome 14q32 in acute lymphoblastic leukemia of T-lineage. Fusion of TLX3 to TCRδ has also been reported. We describe a novel translocation t(5;14)(q35;q11) identified in a case of B-cell chronic lymphoproliferative disorder. FISH and molecular studies located the chromosome 14 breakpoint within the TCRδgene, at the Dδ3 segment, and the chromosome 5 breakpoint 2.5kb downstream (telomeric) of the NKX2-5 gene. As a result of this translocation, both NKX2-5 and TLX3 were transcribed, whereas only NKX2-5 was detected at the protein level. To investigate the expression of these two genes in B-cell chronic proliferations, we screened 20 B-cell chronic lymphocytic leukemias (B-CLL) and 21 atypical B-CLL samples by RT-PCR and RQ-PCR. No sample demonstrated NKX2-5 expression and only one patient showed TLX3 expression. This patient had an evolutive B-CLL, with complex chromosomal abnormalities, without involvement of the band 5q35. In conclusion, this study identifies a new translocation involving a NK-like homeobox gene in a mature B lymphoproliferative disorder, underscoring precedent identification of NKX2-5 activation in two human lymphoid leukemia cell lines. It also demonstrates that deregulation of homeobox encoding genes is not a specific feature of acute leukemic proliferations, but is also observed in chronic malignancies.

Induction of Multiple Myeloma-Specific Cytotoxic T Lymphocytes Using HLA-A2.1-Specific CD19 and CD20 Peptides.

We have identified novel CD19 and CD20 antigen-derived HLA-A2.1-specific immunogenic peptides, CD19150–158 (KLMSPKLYV) and CD20188–196 (SLFLGILSV), for generating cytotoxic T lymphocytes (CTLs) against malignant B-cell diseases. Initial testing showed that the CTLs displayed antigen-specific and HLA-A2.1-restriced cytotoxic activity against both Burkitt's lymphoma and chronic lymphoid leukemia cell lines. The observed cytotoxic activity of the CTLs was shown to be specific to the CD19150–158 or the CD20188–196 peptides. Additionally, the CTLs displayed a distinct phenotype (majority CD69+/CD45RO+) along with a significant (p<0.05) increase in cell proliferation and IFN-γ release following re-stimulation with HLA-A2.1+/CD19+/CD20+ tumor cell lines. Based on emerging information that clonogenic myeloma cells express CD19 and/or CD20, we evaluated the activity of the CD19 and CD20 peptide specific-CTLs against several multiple myeloma cell lines. Five of 10 myeloma cell lines evaluated were HLA-A2.1-positive and expressed both CD19 and CD20 antigens. CD19 peptide specific-CTLs generated from normal donors were able to specifically lyse CD19+/HLA-A2.1+ MM cell lines (30% lysis; 10:1 E:T ratio) but did not lyse CD19−/HLA-A2.1+ or CD19+/HLA-A2.1− cell lines. Similarly, the CD20-specific CTLs generated from normal donors lysed CD20+/HLA-A2.1+ MM cell lines (25% lysis; 10:1 E:T ratio), in a manner restricted to HLA-A2.1 and specific to antigens. We next showed IFN-γ production by the CTLs after exposure to CD19+/HLA-A2.1+ or CD20+/HLA-A2.1+ MM cells. Moreover, we have demonstrated the ability to expand CD20-CTLs under serum-free culture conditions while maintaining their cytotoxic activity (28–49%). In ongoing studies, we are evaluating the ability of CD19- and CD20-specific CTLs to eliminate clonogenic myeloma cells in vitro and in vivo in a SCID mouse model of myeloma. These preclinical studies strongly suggest that immunogenic CD19 and CD20 peptide-based vaccines represent a promising immunotherapeutic approach in myeloma.

Identification of genes leading to glucocorticoid‐induced leukemic cell death

Glucocorticoidal steroids (GC) are capable of causing apoptotic death of many varieties of lymphoid cells; consequently, GC are used in therapy for many lymphoid malignancies. Gene transcription in the GC-treated cells is required for subsequent apoptosis, but only a few of the actual genes involved have been identified. We employed gene microarray analysis to find the network of genes involved in GC-evoked cell death, using three clones derived from the CEM lymphoid leukemia cell line. Clone C1-15 was resistant to GC-evoked apoptosis, although not necessarily to GC-induced gene transcription; the other two underwent apoptosis in the presence of GC. Clone C7-14 was subcloned from the apoptosis-sensitive parental C7 clone to establish karyotypic uniformity. The second sensitive clone, C1-6, was a spontaneous revertant from parental resistant clone C1. A period of > or = 24 h in the constant presence of receptor-occupying concentrations of synthetic GC dexamethasone (Dex) was necessary for apoptosis to begin. To identify the steps leading to this dramatic event, we identified the changes in gene expression in the 20-h period preceding the onset of overt apoptosis. Cells in the log phase of growth were treated with 10(-6) M Dex, and 2-20 h later, mRNA was prepared and analyzed using the Affymetrix HG_U95Av2 chip, containing probes for about 12,600 genes. Of these, approximately 6,000 were expressed above background. Comparisons of the basal and expressed genes in the three clones led to several conclusions: The Dex-sensitive clones shared the regulation of a limited set of genes. The apoptosis-resistant clone C1-15 showed Dex effects on a largely different set of genes. Promoter analysis of the regulated genes suggested that primary gene targets for GC often lack a classic GC response element.

Deregulated expression in Ph+ human leukemias of AHI-1, a gene activated by insertional mutagenesis in mouse models of leukemia

AbstractAhi-1/AHI-1 (Abelson helper integration site-1) encodes a family of protein isoforms containing one Src homology 3 (SH3) domain and multiple tryptophan-aspartic acid 40 (WD40)–repeat domains. The function of these proteins is unknown, but involvement in leukemogenesis has been suggested by the high frequency of Ahi-1 mutations seen in certain virus-induced murine leukemias. Here we show that in both mice and humans, Ahi-1/AHI-1 expression is highest in the most primitive hematopoietic cells with specific patterns of down-regulation in different lineages. Cells from patients with chronic myeloid leukemia (CML; n = 28) show elevated AHI-1 transcripts in all disease phases and, in chronic phase, in the leukemic cells at all stages of differentiation, including quiescent (G0) CD34+ cells as well as terminally differentiating cells. In the most primitive lin–CD34+CD38– CML cells, transcripts for the 2 shorter isoforms of AHI-1 are also increased. Although 15 of 16 human lymphoid and myeloid leukemic cell lines showed aberrant control of AHI-1 expression, this was not seen in blasts obtained directly from patients with acute Philadelphia chromosome–negative (Ph–) leukemia (n = 15). Taken together, our results suggest that down-regulation of AHI-1 expression is an important conserved step in primitive normal hematopoietic cell differentiation and that perturbations in AHI-1 expression may contribute to the development of specific types of human leukemia.

The Histone Deacetylase Inhibitor MS-275 Interacts Synergistically with Fludarabine to Induce Apoptosis in Human Leukemia Cells

Interactions between the novel benzamide histone deacetylase (HDAC) inhibitor MS-275 and fludarabine were examined in lymphoid and myeloid human leukemia cells in relation to mitochondrial injury, signal transduction events, and apoptosis. Prior exposure of Jurkat lymphoblastic leukemia cells to a marginally toxic concentration of MS-275 (e.g., 500 nM) for 24 h sharply increased mitochondrial injury, caspase activation, and apoptosis in response to a minimally toxic concentration of fludarabine (500 nM), resulting in highly synergistic antileukemic interactions and loss of clonogenic survival. Simultaneous exposure to MS-275 and fludarabine also led to synergistic effects, but these were not as pronounced as observed with sequential treatment. Similar interactions were noted in the case of (a) other human leukemia cell lines (e.g., U937, CCRF-CEM); (b) other HDAC inhibitors (e.g., sodium butyrate); and (c) other nucleoside analogues (e.g., 1-beta-D-arabinofuranosylcytosine, gemcitabine). Potentiation of fludarabine lethality by MS-275 was associated with acetylation of histones H3 and H4, down-regulation of the antiapoptotic proteins XIAP and Mcl-1, enhanced cytosolic release of proapoptotic mitochondrial proteins (e.g., cytochrome c, Smac/DIABLO, and apoptosis-inducing factor), and caspase activation. It was also accompanied by the caspase-dependent down-regulation of p27(KIP1), cyclins A, E, and D(1), and cleavage and diminished phosphorylation of retinoblastoma protein. However, increased lethality of the combination was not associated with enhanced fludarabine triphosphate formation or DNA incorporation and occurred despite a slight reduction in the S-phase fraction. Prior exposure to MS-275 attenuated fludarabine-mediated activation of MEK1/2, extracellular signal-regulated kinase, and Akt, and enhanced c-Jun NH(2)-terminal kinase phosphorylation; furthermore, inducible expression of constitutively active MEK1/2 or Akt significantly diminished MS-275/fludarabine-induced lethality. Combined exposure of cells to MS-275 and fludarabine was associated with a significant increase in generation of reactive oxygen species; moreover, both the increase in reactive oxygen species and apoptosis were largely attenuated by coadministration of the free radical scavenger L-N-acetylcysteine. Finally, prior administration of MS-275 markedly potentiated fludarabine-mediated generation of the proapoptotic lipid second messenger ceramide. Taken together, these findings indicate that the HDAC inhibitor MS-275 induces multiple perturbations in signal transduction, survival, and cell cycle regulatory pathways that lower the threshold for fludarabine-mediated mitochondrial injury and apoptosis in human leukemia cells. They also provide insights into possible mechanisms by which novel, clinically relevant HDAC inhibitors might be used to enhance the antileukemic activity of established nucleoside analogues such as fludarabine.

Methylation of the asparagine synthetase promoter in human leukemic cell lines is associated with a specific methyl binding protein.

We have examined the methylation profiles of the asparagine synthetase (ASY) promoter in a number of human leukemic cell lines in relation to their asparagine (ASN) requirements in vitro. Cells in which the promoter is highly methylated are auxotrophs and express ASY at very low levels. Electromobility shift assays (EMSA) of nuclear extracts with oligomers from the promoting region show, in addition to recognized transcription factor binding, a novel methyl binding protein specific for a 12 base consensus sequence, which includes a single methylated CpG. This sequence overlaps that of the amino-acid response unit of the ASY promoter, which is activated byATF4 and C/EBP. Competition by the methyl binding protein could account for the observed failure of the methylated promoter to bind these transcription factors and consequently, although other mechanisms can also be operative, for the specific repression of the gene. The ASY methyl binding protein (ASMB) is present in leukemic lymphoid and myeloid cells irrespective of their methylation status, and in normal lymphocytes after phytohemagglutinin stimulation. It has been purified by affinity chromatography and has a molecular size of 40 kDa in 10% SDS-polyacrylamide gels.

Regulation of Lymphoid and Myeloid Leukemic Cell Survival: Role of Stromal Cell Adhesion Molecules

Several laboratories have documented the necessity for direct contact of lymphoid and myeloid leukemic cells with bone marrow stromal cells for optimal survival. Subsequent studies have identified various stromal cell adhesion molecules and soluble factors that facilitate survival through leukemic cell anti-apoptotic signal transduction pathways. This report provides an overview of enhanced leukemic cell survival through adhesive interactions with bone marrow expressed molecules. In addition, we describe the establishment of cloned murine stromal cell lines engineered to constitutively express human VCAM-1 protein on their surface. These stromal cell lines will be useful in studies aimed at better understanding the specific contribution of VCAM-1 : VLA-4 signaling in maintenance of residual leukemic disease.

Enhancement of Antineoplastic Action of 5-Aza-2′-deoxycytidine by Phenylbutyrate on L1210 Leukemic Cells

Epigenetic changes, such as aberrant DNA methylation that silences tumor suppressor genes (TSGs), can play an important role in the development of leukemia. The DNA methylation inhibitor, 5-aza-2′-deoxycytidine (5-AZA-CdR), can reactivate these silent TSGs and is an interesting agent to investigate for therapy of leukemia. It has been reported that the effectiveness of 5-AZA-CdR to reactivate TSG can be enhanced by inhibitors of histone deacetylase (HDIs). HDIs can convert a compact chromatin structure to an open configuration that facilitates gene expression. An interesting HDI is phenylbutyrate (PB), which has shown some clinical activity for the therapy of leukemia. In this report we have investigated the antineoplastic activity of 5-AZA-CdR and PB alone and in combination on murine L1210 lymphoid leukemic cells. The in vitro treatment of 5-AZA-CdR and PB in combination produced a greater inhibition of growth, DNA synthesis, and also a greater reduction on colony formation on both L1210 and human HL-60 leukemic cells as compared to either drug alone. The combination also produced a synergistic activation of the TSG, p15CDN2B, in the L1210 cells. In mice with L1210 leukemia the combination showed enhanced antineoplastic activity. We also observed an enhancement of the antineoplastic activity of this combination in mice with L1210 leukemia. These data provide a rationale to investigate 5-AZA-CdR and PB in patients with advanced leukemia.

Involvement of reactive oxygen species in adaphostin-induced cytotoxicity in human leukemia cells

AbstractAdaphostin (NSC 680410), an analog of the tyrphostin AG957, was previously shown to induce Bcr/abl down-regulation followed by loss of clonogenic survival in chronic myelogenous leukemia (CML) cell lines and clinical samples. Adaphostin demonstrated selectivity for CML myeloid progenitors in vitro and remained active in K562 cells selected for imatinib mesylate resistance. In the present study, the mechanism of action of adaphostin was investigated in greater detail in vitro. Initial studies demonstrated that adaphostin induced apoptosis in a variety of Bcr/abl-cells, including acute myelogenous leukemia (AML) blasts and cell lines as well as chronic lymphocytic leukemia (CLL) samples. Further study demonstrated that adaphostin caused intracellular peroxide production followed by DNA strand breaks and, in cells containing wild-type p53, a typical DNA damage response consisting of p53 phosphorylation and up-regulation. Importantly, the antioxidantN-acetylcysteine (NAC) blunted these events, whereas glutathione depletion with buthionine sulfoximine (BSO) augmented them. Collectively, these results not only outline a mechanism by which adaphostin can damage both myeloid and lymphoid leukemia cells, but also indicate that this novel agent might have a broader spectrum of activity than originally envisioned. (Blood. 2003;102:4512-4519)

Requirement for SAPK-JNK signaling in the induction of apoptosis by ribosomal stress in REH lymphoid leukemia cells.

The present studies examined performance of SAPK cascades and apoptotic commitment following ribosomal trauma in REH lymphoid leukemia cells. Ribostatic insults included disruption of ribosomal activity by mechanistically dissimilar agents such as blasticidin-S (BCS) (which binds 28S-rRNA to block peptidyl bond formation), kasugamycin (KSM) (which binds 18S-rRNA to prevent translational initiation), and cycloheximide (CHX) (which blocks A-site to P-site translocation of peptidyl-tRNA). Exposure of REH cells to BCS elicited DNA degradation and apoptotic cytolysis. BCS stimulated JNK1/JNK2 and p38, and their shared targets c-Jun and ATF2. Inhibition of JNK1/JNK2 (but not of p38) antagonized blasticidin-induced apoptosis, whereas targeting alternative ribosomal sites with KSM or CHX limited translation, but failed to activate the SAPK cascade or initiate apoptosis. Our findings indicate that interference with 28S-rRNA by BCS initiates apoptosis in REH cells through recruitment of SAPK-JNK signaling. Disparities between the lethal actions of BCS, KSM, and CHX appear to reflect established differences in the subribosomal targets of these agents. We propose that the SAPK cascade comprises an essential mechanism for the transduction of specific lethal stress signals emanating from active ribosomes, and that interference with the 28S-rRNA, rather than the peptidyl transfer center of the large subunit, is critical to apoptotic commitment.