Shuqing Lü

Point Mutation of the Proteasome β5 Subunit Gene Is an Important Mechanism of Bortezomib Resistance in Bortezomib-Selected Variants of Jurkat T Cell Lymphoblastic Lymphoma/Leukemia Line

To study the mechanism of acquired resistance to bortezomib, a new antitumor drug that is the first therapeutic proteasome inhibitor, we established a series of bortezomib-resistant T lymphoblastic lymphoma/leukemia cell lines, designated the JurkatBs, from the parental Jurkat line via repeated drug selection. There were no significant differences in the growth curves or colony formation between the JurkatB cells and parental Jurkat cells. The effects of bortezomib on cytotoxicity, cell cycle arrest, and induction of apoptosis were decreased in JurkatB cells compared with parental Jurkat cells. A mutation in the proteasome β5 subunit (PSMB5) gene (G322A), which encodes an amino acid change from Ala to Thr at polypeptide position 108, was detected by sequencing full-length cDNA clones and direct polymerase chain reaction products of the PSMB5 gene. Bortezomib caused less inhibition of chymotrypsin-like activity in resistant cells. When the G322A mutant PSMB5 was retrovirally introduced into parental Jurkat cells, it conferred bortezomib resistance to these cells, resulting in decreased cytotoxicity, apoptosis, and inhibition of chymotrypsin-like activity. The predicted structure of A108T-mutated PSMB5 shows a conformational change that suggests decreased affinity to bortezomib. In short, the G322A mutation of the PSMB5 gene is a novel mechanism for bortezomib resistance.

Overexpression of the PSMB5 gene contributes to bortezomib resistance in T-lymphoblastic lymphoma/leukemia cells derived from Jurkat line.

OBJECTIVE To study the mechanism of bortezomib resistance in JurkatB lines derived from T-lymphoblastic lymphoma/leukemia Jurkat line. MATERIALS AND METHODS Cytotoxicities of popular chemotherapeutic drugs to JurkatB cells were analyzed by trypan blue assay. Functional drug efflux in JurkatB cells was determined by flow cytometry utilizing daunorubicin and the expression of P-glycoprotein (P-gp) was detected by Western blot. mRNA expression levels of proteasome beta5 subunit (PSMB5) were measured by quantitation real-time reverse transcription polymerase chain reaction. In situ hybridization was performed to detect the amplification of PSMB5 gene. The chymotrypsin-like activities were assayed by measuring the release of the fluorescent 7-amido-4-methylcoumarin (AMC) from the substrate N-succinyl-Leu-Leu-Val-Tyr-AMC. Cytogenetic studies were performed using R-banded metaphases and fluorescence in situ hybridization (FISH) analysis. IkappaB-alpha levels were detected by Western blot. RESULTS No cross-resistance to daunorubicin, adriamycin, vindesine, and etoposide was found in JurkatB cells. No evidence of drug efflux was found in JurkatB cells and the expression of P-gp was negative. The PSMB5 mRNA was overexpressed in highly resistant JurkatB5 and JurkatB1 lines compared with parental Jurkat, corresponding well with the increase of chymotrypsin-like activity and a karyotype of i(14q). Amplification of PSMB5 gene was demonstrated by in situ hybridization and FISH. The decreased IkappaB-alpha level in JurkatB5 cells after bortezomib treatment indicating an upregulation of nuclear factor-kappaB (NF-kappaB) activity. CONCLUSION The mechanism of bortezomib resistance is different from that of multidrug resistance. Overexpression of PSMB5 is an important mechanism for bortezomib resistance in JurkatB lines. NF-kappaB may play a critical role in evading the apoptotic effects.

Clinical and biological characteristics of adult biphenotypic acute leukemia in comparison with that of acute myeloid leukemia and acute lymphoblastic leukemia: a case series of a Chinese population

Biphenotypic acute leukemia is rare, necessitating large series to provide information on prognosis. In this paper Xu and colleagues review Chinese experience with this conditions. The findings of this study indicate that the prognosis of biphenotypic acute leukemia patients is poor when compared with de novo acute myeloid leukemia or acute lymphoblastic leukemia. See related perspective article on page 891 and related review article on page 984. Background Biphenotypic acute leukemia is a rare disorder that is difficult to diagnose. It displays features of both myeloid and lymphoid lineage. There is still a lack of studies in biphenotypic acute leukemia in a Chinese population. We present here a comprehensive investigation of the clinical and biological characteristics, and outcome of biphenotypic acute leukemia in our hospital in over a seven year period. Design and Methods We retrospectively analyzed 452 adult acute leukemia patients diagnosed according to French-American-British (FAB) classification and biphenotypic acute leukemia diagnosed according to European Group for the Immunological Characterization of Leukemias (EGIL) classification, respectively. Biological characteristics, response to treatment, and outcome were examined in biphenotypic acute leukemia patients and compared with that in acute myeloid leukemia and acute lymphoblastic leukemia patients with complete follow-up profiles diagnosed in the same period. Results Of 452 acute leukemia patients, 21 cases (4.6%) were diagnosed as biphenotypic acute leukemia. Among them, 14 (66.7%) were B lymphoid and myeloid, 5 (23.8%) were T lymphoid and myeloid, one (4.8%) was T/B lymphoid and one (4.8%) was trilineage differentiation. When compared with acute myeloid leukemia and acute lymphoblastic leukemia, patients with biphenotypic acute leukemia showed significantly higher incidence of CD34 antigen expression, unfavorable karyotypes, and extramedullary infiltration (p<0.05). In this cohort of patients with biphenotypic acute leukemia, t(9;22) was the most common abnormality in chromosome structure. The median disease-free survival and overall survival in biphenotypic acute leukemia patients was five months and ten months, respectively, significantly shorter than those in acute myeloid leukemia and acute lymphoblastic leukemia patients (p<0.05). Conclusions The prognosis of biphenotypic acute leukemia patients is poor when compared with de novo acute myeloid leukemia or acute lymphoblastic leukemia. Biphenotypic acute leukemia patients showed a much higher incidence of CD34 antigen expression, complex abnormal karyotype, extramedullary infiltration, relapse, and resistance to therapy after relapse.

Different mutants of PSMB5 confer varying bortezomib resistance in T lymphoblastic lymphoma/leukemia cells derived from the Jurkat cell line

OBJECTIVE To investigate the relationship between bortezomib resistance and mutations in the proteasome beta5 subunit (PSMB5) gene. MATERIALS AND METHODS Various bortezomib-resistant lymphoblastic lymphoma/leukemia lines were established by repeated cycles of bortezomib selection. Mutations were detected by sequencing the complementary DNA of the PSMB5 gene. Mutated clones were selected by limited dilution and cultured without bortezomib. Messenger RNA expression levels of PSMB5 in these mutated clones were measured by quantitative reverse transcription polymerase chain reaction. The degree of resistance was determined by cytotoxicity at various bortezomib concentrations. The chymotrypsin-like activities were assayed by measuring the release of the fluorescent 7-amido-4-methylcoumarin from the substrate N-succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin. RESULTS In addition to the previously reported PSMB5 G322A mutant (Ala49Thr), a C323T mutant (Ala49Val), and G322A, C326T conjoined mutant (Ala49Thr and Ala50Val) were selected and clones containing these mutations (JurkatB-G322A, JurkatB-C323T, and JurkatB-G322A/C326T) were obtained. After being cultured without bortezomib for >2 months, no significant difference in PSMB5 messenger RNA levels was detected between these JurkatB cells and parental Jurkat cells. JurkatB-G322A, JurkatB-C323T, and JurkatB-G322A/C326T clones displayed 22.0-fold, 39.4-fold, and 66.7-fold resistance, respectively, to bortezomib compared to Jurkat cells. There were no significant differences between the chymotrypsin-like activities of these mutants and Jurkat cells. The inhibitory effect of bortezomib on chymotrypsin-like activity was the weakest in JurkatB-G322A/C326T cells, and the strongest in JurkatB-G322A cells, with JurkatB-C323T cells falling in between. CONCLUSION Mutations of the PSMB5 gene resulting in substitutions of Ala49 and Ala50 of PSMB5 protein can confer varying bortezomib resistance.

Homoharringtonine and omacetaxine for myeloid hematological malignancies

Homoharringtonine (HHT), a plant alkaloid with antitumor properties originally identified nearly 40 years ago, has a unique mechanism of action by preventing the initial elongation step of protein synthesis. HHT has been used widely in China for the treatment of chronic myeloid leukemia (CML), acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Omacetaxine, a semisynthetic form of HHT, with excellent bioavailability by the subcutaneous route, has recently been approved by FDA of the United States for the treatment of CML refractory to tyrosine kinase inhibitors. This review summarized preclinical and clinical development of HHT and omacetaxine for myeloid hematological malignancies.

The effects of proteasome inhibitor bortezomib on a P-gp positive leukemia cell line K562/A02

The aim of this study is to clarify the efficacy of proteasome inhibitor bortezomib to multidrug resistant (MDR) acute leukemia cells. We observed the effects of bortezomib on a P‐glycoprotein (P‐gp) positive leukemia line K562/A02. The results showed that bortezomib has significant effects on P‐gp positive K562/A02 cells including cytotoxicity (48 h IC50: 171.36 nm), induction of apoptosis (31.71 ± 1.07% apoptotic cells after 24 h treatment at 100 nm), and inhibition of proteasome chymotrypsin‐like activity (relative activity to untreated controls: 20.07 ± 0.66% at 24 h with 10 nm bortezomib). These effects were lower than those observed in K562 cells (IC50, percentage of apoptotic cells, relative chymotrypsin‐like activity to untreated controls were 56.28 nm, 77.95 ± 0.35%, 5.35 ± 2.05% after the same treatments, respectively). No synergy between daunorubicin and bortezomib was shown in the killing of K562/A02 cells (synergistic ratios were <1). P‐gp expression levels did not decrease in K562/A02 cells after bortezomib treatment. Pretreatment with bortezomib does not improve the intracellular anthracycline concentration in K562/A02 cells. Bortezomib shows a promising effect for the treatment of refractory/relapsed leukemia, but it does not improve the effect of anthracycline to MDR leukemia cells.

A homoharringtonine-based induction regimen for the treatment of elderly patients with acute myeloid leukemia: a single center experience from China

Background and purposeThe response to remission induction in elderly patients with acute myeloid leukemia (AML) remains poor. The purpose of this paper is to evaluate the efficacy and toxicity of a plant alkaloid, homoharringtonine, in combination with cytarabine as an induction therapy for AML in elderly patients (≥60 years).ResultsTwenty-three patients were treated with the HA regimen consisting of homoharringtonine (2 mg/m2/day for 7 days) and cytarabine (Ara-C, 100 mg/m2/day for 7 days). The overall response rate was 56.5% with complete remission (CR) rate of 39.1% and partial remission of 17.4%. There was no early death in this cohort of patients. The estimated median overall survival (OS) time of all patients was (12.0 ± 3.0) months. The estimated OS time of the CR patients was 15 months. The estimated one-year OS rate of all patients treated with HA protocol was (49.3 ± 13.5) %. The estimated one-year OS rate of the CR patients was (62.5 ± 17.1) %.ConclusionHA is a suitable induction regimen for elderly patients with AML, with relatively low toxicity and reasonable response rate.

FISH+CD34+CD38- cells detected in newly diagnosed acute myeloid leukemia patients can predict the clinical outcome.

BackgroundIn acute myeloid leukemia (AML), the leukemia initiating cells (LICs) or leukemia stem cells (LSCs) is found within the CD34+CD38- cell compartment. The LICs subpopulation survives chemotherapy and is most probable the cause of minimal residual disease (MRD), which in turn is thought to cause relapse. The aim of this study was to determine the prognostic value of the percentage of LICs in blasts at diagnosis.Design and methodsThe percentage of LICs in the blast population was determined at diagnosis using a unique Flow-FISH analysis, which applies fluorescent in situ hybridization (FISH) analysis on flow cytometry sorted cells to distinguish LICs within the CD34+CD38- cell compartment. Fourty-five AML patients with FISH-detectable cytogenetic abnormalities treated with standardized treatment program were retrospectively included in the study. Correlations with overall survival (OS), events-free survival (EFS) and cumulative incidence of relapse (CIR) were evaluated with univariate and multivariate analysis.ResultsThe percentage of LICs is highly variable in patients with acute myeloid leukemia, ranged from 0.01% to 52.8% (median, 2.1%). High LIC load (≥1%) negatively affected overall survival (2-year OS: 72.57% vs. 16.75%; P = 0.0037) and events-free survival (2-year EFS: 67.23% vs. 16.33%; P = 0.0018), which was due to an increased cumulative incidence of relapse (2-year CIR: 56.7% vs. 18.0%; P = 0.021). By multivariate analysis, high LIC load retained prognostic significance for OS and EFS.ConclusionsIn the present study, we established the Flow-FISH protocol as a useful method to distinguish normal and leukemic cells within the CD34+CD38- cell subpopulation. The high percentage of LICs at diagnosis was significantly correlated with increased risk of poor clinical outcome.

Characteristics of acute myeloid leukemia with myelodysplasia-related changes: A retrospective analysis in a cohort of Chinese patients.

We retrospectively analyzed 449 patients with AML under the WHO classification of AML 2008 and probed implications of this classification in diagnosis and treatment of acute myeloid leukemia with myelodysplasia‐related changes (AML‐MRC) among them. The clinical presentations, biological features, treatments, and prognosis of patients diagnosed with AML‐MRC were analyzed and compared with those of AML not otherwise specified (AML‐NOS). In all patients, 115 (25.6%) were diagnosed as AML‐MRC including 64 males and 51 females with median onset age of 48 years (range from 17 to 78). Their complete remission (CR) rate was 60.9% and relapse rate was 57.1%. The observed median overall survival (OS) and disease‐free survival (DFS) were 10 and 5 months, respectively, which was significantly shorter than those of AML‐NOS patients (P < 0.05). The prognosis of AML‐MRC patients with myelodysplastic syndrome (MDS)‐related cytogenetics sole was similar to those with history of MDS or myelodysplastic/myeloproliferative neoplasm (MDS/MPN). Patients with MDS‐related cytogenetic abnormalities and/or history of MDS or MDS/MPN predisposed significantly shortened CR, OS, and DFS than AML‐MRC patients with only multilineage dysplasia (MLD) and AML‐NOS patients (P < 0.05). Multivariate analysis showed that age, cytogenetics, and history of MDS or MDS/MPN were independent prognostic factors. Patient diagnosed as AML‐MRC presented distinctive clinical and biological features. Presence of MLD does not change the prognosis. Am. J. Hematol. 89:874–881, 2014.

Bortezomib in combination with epirubicin, dexamethasone and thalidomide is a highly effective regimen in the treatment of multiple myeloma: a single-center experience

The aim of the present study was to evaluate the effectiveness of bortezomib combined with epirubicin, dexamethasone, and thalidomide (BADT) for the treatment of multiple myeloma (MM). The BADT regimen consisted of a maximum of eight 4-week cycles of: intravenous bortezomib (1.0 mg/m2) and intravenous epirubicin (12 mg/m2) on days 1, 4, 8, and 11; dexamethasone (20 mg) on days 1, 2, 4, 5, 8, 9, 11, and 12; and oral thalidomide (100 mg/m2) on days 1–28. Twelve patients with MM were included in the study, of whom four had not been previously treated and eight had been previously treated with at least one cycle of a systemic combined regimen. All the patients completed at least two cycles of treatment, with an average of five cycles; the complete response (CR) rate was 83.3% (10/12) and stabilization of disease was 16.7% (2/12). The average number of cycles required to achieve CR was 1.9 (range 1–6). In three patients, mobilization of peripheral blood stem cells allowed a sufficient quantity of CD34+ cells to be harvested for future autotransplantation. The main adverse reactions included peripheral neuropathy (4/12), thrombocytopenia (3/12), electrocardiographic abnormalities (4/12), neutropenia (5/12), and liver function impairment (4/12), primarily grade I–II. Infection occurred in four patients with neutropenia, including one patient who developed sepsis. The estimated 1-year overall survival rate was 91.7 ± 8.0%, and the estimated 1-year disease-free survival was 75.0 ± 12.5%. BADT is a highly effective combined regimen, with acceptable toxicity, for the treatment of multiple myeloma.