Long-Jun Gu

NOTCH1 mutations in T-cell acute lymphoblastic leukemia: prognostic significance and implication in multifactorial leukemogenesis.

Purpose: NOTCH signaling pathway is essential in T-cell development and NOTCH1 mutations are frequently present in T-cell acute lymphoblastic leukemia (T-ALL). To gain insight into its clinical significance, NOTCH1 mutation was investigated in 77 patients with T-ALL. Experimental Design: Detection of NOTCH1 mutation was done using reverse transcription-PCR amplification and direct sequencing, and thereby compared according to the clinical/biological data of the patients. Results: Thirty-two mutations were identified in 29 patients (with dual mutations in 3 cases), involving not only the heterodimerization and proline/glutamic acid/serine/threonine domains as previously reported but also the transcription activation and ankyrin repeat domains revealed for the first time. These mutations were significantly associated with elevated WBC count at diagnosis and independently linked to short survival time. Interestingly, the statistically significant difference of survival according to NOTCH1 mutations was only observed in adult patients (>18 years) but not in pediatric patients (≤18 years), possibly due to the relatively good overall response of childhood T-ALL to the current chemotherapy. NOTCH1 mutations could coexist with HOX11, HOX11L2, or SIL-TAL1 expression. The negative effect of NOTCH1 mutation on prognosis was potentiated by HOX11L2 but was attenuated by HOX11. Conclusion:NOTCH1 mutation is an important prognostic marker in T-ALL and its predictive value could be even further increased if coevaluated with other T-cell-related regulatory genes. NOTCH pathway thus acts combinatorially with oncogenic transcriptional factors on T-ALL pathogenesis.

AML1-ETO9a is correlated with C-KIT overexpression/mutations and indicates poor disease outcome in t(8;21) acute myeloid leukemia-M2.

AML1-ETO fusion gene is generated from chromosomal translocation t(8;21) mainly in acute myeloid leukemia M2 subtype (AML-M2). Its spliced variant transcript, AML1-ETO9a, rapidly induces leukemia in murine model. To evaluate its clinical significance, AML1-ETO9a expression was assessed in 118 patients with t(8;21) AML-M2, using qualitative and nested quantitative reverse transcriptase (RT)–PCR methods. These cases were accordingly divided into the AML1-ETO9a-H group (n=86, positive for qualitative RT–PCR, with higher level of AML1-ETO9a by quantitative RT–PCR) and the AML1-ETO9a-L group (n=32, negative for qualitative RT–PCR, with lower but still detectable level of AML1-ETO9a by quantitative RT–PCR). C-KIT expression was significantly increased in the AML1-ETO9a-H group, as compared with the AML1-ETO9a-L group. Of the 36 patients harboring C-KIT mutations, 32 patients overexpressed AML1-ETO9a (P=0.0209). Clinically, AML1-ETO9a-H patients exhibited significantly elevated white blood cells count, less bone marrow aberrant myelocytes, increased CD56 but decreased CD19 expression (P=0.0451, P=0.0479, P=0.0149 and P=0.0298, respectively). Moreover, AML1-ETO9a overexpression was related to short event-free and overall survival time (P=0.0072 and P=0.0076, respectively). Taken together, these data suggest that AML1-ETO9a is correlated with C-KIT overexpression/mutations and indicates poor disease outcome in t(8;21) AML-M2.

Negative feedback-defective PRPS1 mutants drive thiopurine resistance in relapsed childhood ALL

Relapse is the leading cause of mortality in children with acute lymphoblastic leukemia (ALL). Among chemotherapeutics, thiopurines are key drugs in ALL combination therapy. Using whole-exome sequencing, we identified relapse-specific mutations in the phosphoribosyl pyrophosphate synthetase 1 gene (PRPS1), which encodes a rate-limiting purine biosynthesis enzyme, in 24/358 (6.7%) relapsed childhood B cell ALL (B-ALL) cases. All individuals who harbored PRPS1 mutations relapsed early during treatment, and mutated ALL clones expanded exponentially before clinical relapse. Our functional analyses of PRPS1 mutants uncovered a new chemotherapy-resistance mechanism involving reduced feedback inhibition of de novo purine biosynthesis and competitive inhibition of thiopurine activation. Notably, the de novo purine synthesis inhibitor lometrexol effectively abrogated PRPS1 mutant–driven drug resistance. These results highlight the importance of constitutive activation of the de novo purine synthesis pathway in thiopurine resistance, and they offer therapeutic strategies for the treatment of relapsed and thiopurine-resistant ALL.

Genomic Profiling of Adult and Pediatric B-cell Acute Lymphoblastic Leukemia.

Genomic landscapes of 92 adult and 111 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) were investigated using next-generation sequencing and copy number alteration analysis. Recurrent gene mutations and fusions were tested in an additional 87 adult and 93 pediatric patients. Among the 29 newly identified in-frame gene fusions, those involving MEF2D and ZNF384 were clinically relevant and were demonstrated to perturb B-cell differentiation, with EP300-ZNF384 inducing leukemia in mice. Eight gene expression subgroups associated with characteristic genetic abnormalities were identified, including leukemia with MEF2D and ZNF384 fusions in two distinct clusters. In subgroup G4 which was characterized by ERG deletion, DUX4-IGH fusion was detected in most cases. This comprehensive dataset allowed us to compare the features of molecular pathogenesis between adult and pediatric B-ALL and to identify signatures possibly related to the inferior outcome of adults to that of children. We found that, besides the known discrepancies in frequencies of prognostic markers, adult patients had more cooperative mutations and greater enrichment for alterations of epigenetic modifiers and genes linked to B-cell development, suggesting difference in the target cells of transformation between adult and pediatric patients and may explain in part the disparity in their responses to treatment.

Newly diagnosed acute lymphoblastic leukemia in China (II): prognosis related to genetic abnormalities in a series of 1091 cases

The molecular characterization of cytogenetic abnormalities has not only provided insights into the mechanisms of leukemogenesis but also led to the establishment of new treatment strategies targeting these abnormalities and thereby further improve the prognosis of patients. We analyzed the prognosis of 1091 Chinese patients with newly diagnosed acute lymphoblastic leukemia (ALL) and explored the prognostic impacts of a large number of cytogenetic/molecular abnormalities. It was demonstrated that, in both B- and T-ALL settings, the prognosis was negatively correlated to the age as reported to date. For childhood T-ALL patients, it was also documented that the HOX11 expression represented a favorable prognostic factor as it was in adult ones. We identified CRLF2 overexpression as an intermediate-risk marker and Ik6 variant of IKZF1 gene as a high-risk one when stratifying pediatric B-ALL cases according to cytogenetic/molecular risks. We also found that Ik6 variant and CRLF2 overexpression had an important role in dictating the prognosis of Ph-negative patients, which may be useful markers in guiding the treatment of ALL in the future, with tyrosine kinase inhibitors on the other hand reversing the fate of Ph-positive ALL patients.

Newly diagnosed acute lymphoblastic leukemia in China (I): abnormal genetic patterns in 1346 childhood and adult cases and their comparison with the reports from Western countries

It has been generally acknowledged that the diagnosis, treatment and prognosis evaluation of leukemia largely rely on an adequate identification of genetic abnormalities. A systemic analysis of genetic aberrations was performed in a cohort of 1346 patients with newly diagnosed acute lymphoblastic leukemia (ALL) in China. The pediatric patients had higher incidence of hyperdiploidy and t(12;21) (p13;q22)/ETV6–RUNX1 than adults (P<0.0001); in contrast, the occurrence of Ph and Ik6 variant of IKZF1 gene was much more frequent in adult patients (all P<0.0001). In B-ALL, the existence of Ik6 and that of BCR–ABL were statistically correlated (P<0.0001). In comparison with Western cohorts, the incidence of t(9;22) (q34;q11)/BCR–ABL (14.60%) in B-ALL and HOX11 expression in T-ALL (25.24%) seemed to be much higher in our group, while the incidence of t(12;21) (p13;q22)/ETV6–RUNX1 (15.34%) seemed to be lower in Chinese pediatric patients. The occurrence of hyperdiploidy was much lower either in pediatric (10.61% vs 20–38%) or adult patients (2.36% vs 6.77–12%) in our study than in Western reports. In addition, the frequencies of HOX11L2 in adult patients were much higher in our cohort than in Western countries (20.69% vs 4–11%). In general, it seems that Chinese ALL patients bear more adverse prognostic factors than their Western counterparts do.

The downregulation of asparagine synthetase expression can increase the sensitivity of cells resistant to L -asparaginase

The downregulation of asparagine synthetase expression can increase the sensitivity of cells resistant to L -asparaginase

Asparagine synthetase is partially localized to the plasma membrane and upregulated by L-asparaginase in U937 cells

This study investigated the intracellular localization of asparagine synthetase (ASNS) in the relation with chemoresistance in leukemia. pIRES-GFP-ASNS-Flag/Neo expression vector was transiently tansfected into SK-N-MC cells and 297T cells respectively. Immunofluorescence and Western blot analysis were performed for cellular localization of ASNS respectively. U937 cells were treated with L-asparaginase for 48 h and examined for endogenous ASNS expression on plasma membrane by immunofluorescence staining. Immunofluorescence staining showed that the transiently expressed ASNS was partly localized on transfected-SK-N-MC cell surface. Moreover, Western blotting exhibited that ASNS expressed both in cytosol and on plasma membrane of transfected-293T cells. Immunofluorescence staining with anti-ASNS-specific monoclonal antibody revealed that endogenous ASNS was localized on the plasma membrane of U937 cells, except for its distribution in the cytosol. In addition, ASNS exhibited a higher expression on plasma membrane after treatment with L-asparaginase as compared with the untreated cells. It was concluded that the subcellular translocation of ASNS may play an important role in L-asparaginase resistance in leukemia cells.SummaryThis study investigated the intracellular localization of asparagine synthetase (ASNS) in the relation with chemoresistance in leukemia. pIRES-GFP-ASNS-Flag/Neo expression vector was transiently tansfected into SK-N-MC cells and 297T cells respectively. Immunofluorescence and Western blot analysis were performed for cellular localization of ASNS respectively. U937 cells were treated with L-asparaginase for 48 h and examined for endogenous ASNS expression on plasma membrane by immunofluorescence staining. Immunofluorescence staining showed that the transiently expressed ASNS was partly localized on transfected-SK-N-MC cell surface. Moreover, Western blotting exhibited that ASNS expressed both in cytosol and on plasma membrane of transfected-293T cells. Immunofluorescence staining with anti-ASNS-specific monoclonal antibody revealed that endogenous ASNS was localized on the plasma membrane of U937 cells, except for its distribution in the cytosol. In addition, ASNS exhibited a higher expression on plasma membrane after treatment with L-asparaginase as compared with the untreated cells. It was concluded that the subcellular translocation of ASNS may play an important role in L-asparaginase resistance in leukemia cells.

Homoharringtonine as a backbone drug for the treatment of newly diagnosed pediatric acute myeloid leukemia: a report from a single institution in China

Homoharringtonine (HHT) is one of several cephalotaxine alkaloids that has shown clinical efficacy in the treatment of acute myeloid leukemia (AML). The purpose of this study was to evaluate the efficacy and toxicity of HHT for de novo pediatric AML. Patients entered in this study were treated with a regimen including HHT 3.5 mg/m2 day for 9 days for 6–8 cycles after induction and consolidation with cytarabine plus daunorubicin (DA). One hundred and seventy-one eligible patients, with a median age of 7.58 years, were enrolled. Complete response was obtained in 140/171 (81.9%) cases within 60 days (2 cycles) after DA induction. The 5-year event-free survival was 52.75%. Severe myelosuppression was seen in all patients, with an average minimum WBC count of 686/μl. Following the HHT-including regimen, one patient suffered severe pancreatitis, and a second with a history of congenital hepatitis B suffered liver failure. No significant drug-induced hypotension, fluid retention, hyperglycemia, or cardiac toxicity was detected in this study. Other toxicities, including nausea, vomiting, diarrhea, and mucositis, were mild. HHT-including protocols may emerge as useful therapeutic options in future clinical trials.

Outcome of Chinese children with unrelated donor hematopoietic stem cell transplantation

To evaluate the prognostic factors and outcomes in Chinese children undergoing unrelated donor hematopoietic stem cell transplantation (UDT).