ROBO1 deficiency impairs HSPC homeostasis and erythropoiesis via CDC42 and predicts poor prognosis in MDS.

Myelodysplastic syndrome (MDS) is a group of clonal hematopoietic neoplasms originating from hematopoietic stem progenitor cells (HSPCs). We previously identified frequent roundabout guidance receptor 1 (ROBO1) mutations in patients with MDS, while the exact role of ROBO1 in hematopoiesis remains poorly delineated. Here, we report that ROBO1 deficiency confers MDS-like disease with anemia and multilineage dysplasia in mice and predicts poor prognosis in patients with MDS. More specifically, Robo1 deficiency impairs HSPC homeostasis and disrupts HSPC pool, especially the reduction of megakaryocyte erythroid progenitors, which causes a blockage in the early stages of erythropoiesis in mice. Mechanistically, transcriptional profiling indicates that Cdc42, a member of the Rho-guanosine triphosphatase family, acts as a downstream target gene for Robo1 in HSPCs. Overexpression of Cdc42 partially restores the self-renewal and erythropoiesis of HSPCs in Robo1-deficient mice. Collectively, our result implicates the essential role of ROBO1 in maintaining HSPC homeostasis and erythropoiesis via CDC42.

Dynamics of epigenetic regulator gene BCOR mutation and response predictive value for hypomethylating agents in patients with myelodysplastic syndrome.

BACKGROUND: BCOR (BCL6 corepressor) is an epigenetic regulator gene involved in the specification of cell differentiation and body structure development. Recurrent somatic BCOR mutations have been identified in myelodysplastic syndrome (MDS). However, the clinical impact of BCOR mutations on MDS prognosis is controversial and the response of hypomethylating agents in MDS with BCOR mutations (BCORMUT) remains unknown. RESULTS: Among 676 MDS patients, 43 patients (6.4%) harbored BCOR mutations. A higher frequency of BCOR mutations (8.7%) was investigated in patients with normal chromosome, compared to 4.2% in patients with abnormal karyotype (p = 0.040). Compared to the BCORWT patients, the BCORMUT patients showed a higher ratio of refractory anemia with excess blasts subset (p = 0.008). The most common comutations with BCOR genes were ASXL1 (p = 0.002), DNMT3A (p = 0.114) and TET2 (p = 0.148). When the hierarchy of somatic mutations was analyzed, BCOR mutations were below the known initial mutations (ASXL1 or TET2) but were above U2AF1 mutations. Transformation-free survival was significantly shorter in BCORMUT patients than that in BCORWT patients (16 vs. 35 months; p = 0.035). RNA-sequencing was performed in bone marrow mononuclear cells from BCORMUT and BCORWT patients and revealed 2030 upregulated and 772 downregulated genes. Importantly, HOXA6, HOXB7, and HOXB9 were significantly over-expressed in BCORMUT patients, compared to BCORWT patients. Eight of 14 BCORMUT patients (57.1%) achieved complete remission (CR) with decitabine treatment, which was much higher than that in BCORWT patients (28.7%, p = 0.036). Paired sequencing results (before and after decitabine) showed three of 6 CR patients lost the mutated BCOR. The median survival of CR patients with a BCORMUT was 40 months, which was significantly longer than that in patients with BCORWT (20 months, p = 0.036). Notably, prolonged survival was observed in three BCORMUT CR patients even without any subsequent therapies. CONCLUSIONS: BCOR mutations occur more frequently in CN MDS patients, predicting higher risk of leukemia transformation. BCORMUT patients showed a better response to decitabine and achieved longer post-CR survival.

Decitabine treatment sensitizes tumor cells to T-cell-mediated cytotoxicity in patients with myelodysplastic syndromes.

Decitabine treatment improves immunological recognition that increases expression of cancer-testis antigens (CTAs) against solid tumors. The mechanisms of decitabine enhancement of immunogenicity when used for patients with myelodysplastic syndromes (MDS) remain unclear. In the present study, we found relatively low baseline expression of MAGE-A1, MAGE-A3, and SP17 in MDS-derived cell lines. Decitabine treatment significantly improved MAGE-A1, MAGE-A3, and SP17 expression in these cell lines and in MDS patients. Decitabine-treated K562 and SKM-1 target cells with incrementally induced MAGE-A1, MAGE-A3, or SP17 levels up-regulated T lymphocyte function. Decitabine treatment improved CTA-specific cytotoxic T lymphocyte (CTL) recognition of MDS cells via the up-regulation of CTAs. This response was accompanied by enhanced T lymphocyte function and HLA class antigen expression, and increased ICAM-1. These findings suggested that decitabine may have a broad range of therapeutic applications when it is used in association with active adaptive immunity responses against up-regulated CTAs.

Exploration of the role of gene mutations in myelodysplastic syndromes through a sequencing design involving a small number of target genes.

Novel sequencing designs are necessary to supplement the recognized knowledge of myelodysplastic syndrome (MDS)-related genomic alterations. In this study, we sequenced 28 target genes in 320 Chinese MDS patients but obtained 77.2% of recall factors and 82.8% of genetic abnormalities (including karyotype abnormalities). In addition to known relationships among mutations, some specific chromosomal abnormalities were found to link to specific gene mutations. Trisomy 8 tended to be linked to U2AF1 and ZRSR2 mutations, and 20q- exhibited higher SRSF2/WT1 and U2AF1 mutation frequency. Chromosome 7 involvement accounted for up to 50% of RUNX1 mutations and 37.5% of SETBP1 mutations. Patients carrying a complex karyotype were prone to present TP53 mutations (36.1%). However, individuals with normal karyotypes rarely possessed mutations in the TP53, RUNX1 and U2AF1. Moreover, DNMT3A, TP53, SRSF2, STAG2, ROBO1/2 and WT1 predicted poor survival and high AML transformation. By integrating these predictors into international prognostic scoring system (IPSS) or revised IPSS, we built a set of mutation-based prognostic risk models. These models could layer different degrees of risk in patients more satisfactorily. In summary, this sequencing design was able to detect a number of gene mutations and could be used to stratify patients with varied prognostic risk.

TP53 mutations predict decitabine-induced complete responses in patients with myelodysplastic syndromes.

To identify the molecular signatures that predict responses to decitabine (DAC), we examined baseline gene mutations (28 target genes) in 109 myelodysplastic syndrome (MDS) patients at diagnosis. We determined that TP53 mutations predicted complete response (CR), as 10 of 15 patients (66·7%) who possessed TP53 mutations achieved a CR. Univariate and multivariate analyses showed that TP53 mutations are the only molecular signatures predictive of a CR to DAC in MDS. Among the ten patients with TP53 mutations who achieved a CR, nine presented with complex karyotypes due to abnormalities involving chromosome 5 and/or chromosome 7, and eight possessed monosomies. Although TP53 mutations were associated with a higher frequency of CRs, they were not associated with improved survival. Poor outcomes were attributed to early relapses and transformation to acute myeloid leukaemia after CR. Post-DAC therapy patient gene mutation profiles showed that most CR patients exhibited fewer gene mutations after achieving a CR. It seems that suppression of these gene mutations was facilitated by DAC, resulting in a CR. In summary, TP53 mutations might predict decitabine-induced complete responses in patients with MDS. DAC-induced responses may result from partial suppression of malignant clones containing mutated TP53 genes.

Increased PD-1/STAT1 ratio may account for the survival benefit in decitabine therapy for lower risk myelodysplastic syndrome.

Decitabine is an effective therapy for patients with lower risk myelodysplastic syndrome (MDS). However, the mechanisms of decitabine's therapeutic effect are not well established. Forty-four lower risk MDS patients received decitabine therapy. 59.1% patients achieved treatment response, and 53.8% patients who were RBC/platelet-dependent cast off the transfusion burden. The median overall survival (OS) was 19.0 months after decitabine treatment. Moreover, polarization toward type 1 in the CD8 + subset was enhanced, and a significantly increased expression of the PD-1, PD-L1, and PD-1/STAT1 ratio was observed in these lower risk MDS. The patients with amplification of PD-1/STAT1 ratio (2-4) achieved longer OS. Thus, our results suggest that the effect mechanism of decitabine toward lower risk MDS may be the moderate increase of PD-1/STAT1, which contributes to hematopoietic improvement. These findings suggest that a different PD-1-related strategy from those used to treat higher risk patients could be used for lower risk MDS patients.

Whole-exome and targeted sequencing identify ROBO1 and ROBO2 mutations as progression-related drivers in myelodysplastic syndromes.

The progressive mechanism underlying myelodysplastic syndrome remains unknown. Here we identify ROBO1 and ROBO2 as novel progression-related somatic mutations using whole-exome and targeted sequencing in 6 of 16 (37.5%) paired MDS patients with disease progression. Further deep sequencing detects 20 (10.4%) patients with ROBO mutations in a cohort of 193 MDS patients. In addition, copy number loss and loss of heterogeneity (LOH) of ROBO1 and ROBO2 are frequently observed in patients with progression or carrying ROBO mutations. In in vitro experiments, overexpression of ROBO1 or ROBO2 produces anti-proliferative and pro-apoptotic effects in leukaemia cells. However, this effect was lost in ROBO mutants and ROBO-SLIT2 signalling is impaired. Multivariate analysis shows that ROBO mutations are independent factors for predicting poor survival. These findings demonstrate a novel contribution of ROBO mutations to the pathogenesis of MDS and highlight a key role for ROBO-SLIT2 signalling in MDS disease progression.

[Recent advances on the prognostic value of immunophenotyping in multiple myeloma by flow cytometry].

Clinical application of flow cytometry in multiple myeloma (MM) can be found in various dimensions, such as in differential diagnosis of malignant plasma cell disorder from reactive plasmacytosis, identification of the progression risk in MM, and in the detection of minimal residual disease. Flow cytometry-based clonality assessment with immuno-phenotyping encourages and enables the most stringent method of diagnosis and follow-up. The objective of this review is to summarize the recent information of the malignant plasma cell phenotypic profile of MM. The most comprehensive antigens, such as CD19, CD27, CD28, CD45, CD56 and CD117, play a significant role in the characterization of normal and malignant plasma cells. This review also focuses on the association of malignant phenotypic markers with chromosomal aberrations that identify the specific prognostic factors in MM.

Establishment and validation of an updated diagnostic FCM scoring system based on pooled immunophenotyping in CD34+ blasts and its clinical significance for myelodysplastic syndromes.

Abnormal immunophenotypes of hematopoietic cells can be detected by flow cytometry (FCM) to assist the diagnosis of myelodysplastic syndromes (MDS). We previously established a FCM scoring system for the diagnosis of low-grade MDS. In this study, additional valuable antigens were involved in an updated FCM scoring system (u-FCMSS) for all MDS subtypes. The u-FCMSS showed better sensitivity and specificity (89.4% and 96.5%) in distinguishing MDS from non-clonal cytopenia diseases. Validation analysis of u-FCMSS exhibited comparable sensitivity and specificity (86.7% and 93.3%) and high agreement rate (88.9%) of FCM diagnosis with morphological diagnosis at optimal cut-off (score 3). The distribution of FCM scores in different disease stages was also analyzed. The results suggested that early scoring from abnormal expression of mature myeloid/lymphoid antigens and advanced scoring from abnormal expression of stem/progenitor antigens expression constituted the majority of FCM scores of low-grade and high-grade MDS, respectively. High early scoring was generally accompanied by low IPSS-R score and superior survival, whereas high advanced scoring was accompanied by high IPSS-R score and inferior survival. In addition, the low-risk MDS patients with high early scoring and low advanced scoring were revealed as candidates for immunosuppressive therapy, whereas those with high advanced scoring and low early scoring may be more suitable for decitabine treatment. In conclusion, the u-FCMSS is a useful tool for diagnosis, prognosis and treatment selection in MDS. Differences in classes of antigens expressed and in distribution of FCM scores may reflect distinctive stage characteristics of MDS during disease progression.

[Current understanding of iron overload hazard in patients with myelodysplastic syndrome].

Patients with myelodysplastic syndromes (MDS) become dependent on blood transfusions and develop into transfusional iron overload, which is exacerbated by increased absorption of dietary iron in response to ineffective erythropoiesis. However, it is uncertain whether there is an association among iron accumulation, clinical complications, and decreased likelihood of survival in MDS patients. Thereby our current understanding of the effects of transfusion dependency and iron overload in MDS are discussed. Particular emphasis should be placed on further characterizing the role of redox-active forms of labile iron and oxidative stress in iron overload, decreased life expectancy and increased risk of leukemic transformation in MDS patients with iron overload.

Distinct clinical and experimental characteristics in the patients younger than 60 years old with myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) mainly occur in elderly individuals in Western countries. However, MDS is commonly found in young individuals (<60 years) in Asia. The reason for the high incidence in younger individuals is still unclear, and the differences in disease features between young and elderly patients with MDS have been not well recognized. To explore these issues, in this study, we analyzed the clinical and experimental characteristics of MDS in the patients younger and older than 60 years old and characterized the potential age-associated differences. The results showed that over half of the patients with MDS (61.9%) were younger than 60 years old upon the first diagnosis. The younger patients were more likely to be female, who have lower risk and less advanced MDS. The occurrence of trisomy 8 and bone marrow failure were more frequent in the younger patients than the older ones. The marrow CD34+ cells in the younger patients showed lower proliferation and higher apoptosis in comparison with that in the older ones. Obvious amplification of T cells and low CFU formation could be found in the younger patients. CFU formation was significantly increased in the younger patients after the removal of activated T cells. In addition, the younger patients had a lower frequency of p15(INK4B) methylation, longer survival expectancy and less AML transformation. In summary, the younger patients with MDS in China may show more benign disease features than the older ones. Enhanced immunological response may be involved in the pathogenesis of MDS in the patients younger than 60 years.

[Comparison of bone marrow biopsy and smear efficacy in patients with multiple myeloma].

This study was aimed to explore the significance of the bone marrow biopsy for the diagnosis of multiple myeloma. Bone marrow smears and bone marrow biopsy originated from 279 cases of multiple myeloma were detected and compared in term of bone marrow hyperplasia, bone marrow plasma cell infiltration, proliferation mode, pathological changes in the bone marrow stroma and myelofibrosis. The results indicated that the levels of proliferation in bone marrow biopsy was significantly higher than that in bone marrow smears. Plasma cell proliferation mode in bone marrow biopsy was not completely consistent with the proportion of plasma cells in bone marrow smears. The myelofibrosis level displayed influence on the consistency of the proliferation between bone marrow smears and biopsies. It is concluded that as compared with bone marrow smears the bone marrow biopsy can more accurately reflect the levels of bone marrow hyperplasia and bone marrow plasma cell infiltration, proliferation mode and so on. Bone marrow biopsy is valuable for multiple myeloma diagnosis.

[Clinical therapeutic efficacy of rituximab for relapsed and refractory idiopathic thrombocytopenic purpura].

The aim of this study was to evaluate the effect of rituximab treatments for refractory and relapsed idiopathic thrombocytopenic purpura (ITP). 18 patients with refractory and relapsed ITP who received 22 courses of rituximab treatments from January 2007 to December 2010 were analyzed retrospectively. Rituximab was given at a dose of 375 mg/m(2) intravenously weekly for a continuous 4 weeks. The results indicated that responses were achieved in 15 of 22 (68%) courses, out of which complete responses were achieved in 10 of 22 (45%) courses, partial and minimal responses were achieved in 5 of 22 (23%) courses, and no responses were achieved in 7 of 22 (32%) courses. The median time of response was 3 weeks (1 - 17 weeks) from the start of treatment and median duration of response was 13 weeks (1 week - 42 months). The responses were mostly short-sustained and follow-up median time was 20 months (1 - 52 months). The responses of 8 patients (36%) sustained for over 6 months, 6 patients (27%) sustained for over 1 year, and 4 patients also showed sustained response at last visit of follow-up. Previous splenectomy resulted in a poor response (P = 0.037). Patients who failed in rituximab treatment and prior received multiple treatments including splenectomy, had a poor response to further therapies. It is concluded that rituximab is well tolerated by patients and is useful in some patients with relapsed and refractory ITP, however, only about 20% patients can achieve sustained remissions. The patients who failed in rituximab treatment has a poor response to further treatment.

[Yield of CD34(+) cells in graft can be increased significantly by G-CSF used at appropriate time after chemotherapy for AutoPBSCT].

This study was aimed to investigate the influence of timing using G-CSF after chemotherapy on graft yield of mobilized peripheral blood stem cells for autoPBSCT. 39 patients with lymphoma or multiple myeloma (MM) received the same chemotherapy mobilization regimen, including CTX 400 mg/m² d1; VLB 2 mg/m(2) d1; Ara-C 60 mg/m ²× d1-5; VP-16 60 mg/m² × d1-5; and prednisone 40 mg/m² × d1-5. The historical control group (12 cases) received G-CSF subcutaneously (filgrastim) at the first restoration after the initial nadir of the peripheral WBC count. The experimental group (27 cases) received G-CSF during the steady rise of the WBC count (end of fluctuating after initial nadir). G-CSF was given in a single daily subcutaneous dose of 5 µg/kg until the final PBSC apheresis. When the peripheral WBC and mononuclear cell (MNC) counts reached 10 × 109/L and 1.0 × 109/L respectively, leukapheresis was carried out using the COBE Spectra blood cell separator. The results indicated that despite there was comparable treatment with alkylating agents between 2 groups, a significantly increased yield of CD34 positive cells was observed in the experimental group (26.4 × 106/kg), as compared to the historical control group (3.1 × 106/kg) (p = 0.0031). It is concluded that the appropriate timing for the use G-CSF mobilization after chemotherapy is important to increase the CD34(+) cell yield in auto-graft.

[Maintenance treatment of multiple myeloma-review].

Chemotherapy with traditional standard dose or autologous stem cell transplantation (ASCT) after chemotherapy with high dose have some remission effect for multiple myeloma, but relapse still exists. The maintenance treatment would prolonged the remission stage. These treatments included the use of alkylating agent, interferon, corticosteroids, thalidomide and so on. Every maintenance treatment has some advantages and some side effects. The truly effective maintenance treatment would not only minimize the harm of the disease, but also would prolong the overall survival, progression-free survival and the event-free survival. This article summarizes the current progress in the maintenance treatments for multiple myeloma.

[Efficacy of induction chemotherapy for patients with high-risk myelodysplastic syndrome (MDS) or MDS-transformed acute myeloid leukemia with CHG regimen and its comparison with regimen GAG and HA].

This study was aimed to investigate the efficacy of moderate intensity regimen, CHG (homoharringtonine, cytarabine and granulocyte colony-stimulating factor (G-CSF)) on the patients with high-risk MDS or MDS-transformed acute myeloid leukemia. 30 newly diagnosed adult patients with high-risk MDS or MDS-transformed AML were enrolled in this clinical trial to evaluate the efficacy of sequential low-dose homoharringtonine/cytarabine chemotherapy combined with G-CSF priming. Homoharringtonine and Ara-C were injected intravenously at doses of 1 mg and 25 mg daily for 14 consecutive days respectively, G-CSF was injected subcutaneously once daily at a dose of 300 microg on 12 hours prior to chemotherapy and continued given until the end of chemotherapy or when the peripheral WBC count reached > 20 x 10(9)/L. This regimen was given only for one course, and followed by conventional chemotherapy as maintenance or consolidation therapy when CR achieved. 33 patients with high- risk MDS and MDS-transformed AML were injected aclarubicin/Ara-C intravenously at doses of 10 mg and 25 mg for 8 and 14 consecutive days respectively, G-CSF was used at the same dose and the same way as the CHG regimen. 33 patients with high-risk MDS and MDS-transformed AML were treated with HHT/Ara-C intravenously at doses of 2 - 3 mg and 100 - 150 mg daily for 7 consecutive days respectively, G-CSF was injected when WBC count was below 4 x 10(9)/L, and it was stopped to be used when WBC count was > 4 x 10(9)/L. The results showed that (1) 14 patients achieved complete remission (CR) (46.67 %) and 7 patients achieved partial remission (PR) (23.33 %) with one course of CHG regimen, total effective rate was 70%; 14 patient achieved CR (42.4%) and 9 patients achieved PR (27.3%) with one course of CAG regimen, total effective rate was 69.7%; 7 patient achieved CR (33.3%) and 3 patients achieved PR (9.1%) with one course of HA regimen, total effective rate was 42.4%. There was no statistical difference between the effective rate of CHG and CAG, but difference was significant between CHG and HA. (2) Agranulocytosis (neutrophil < 0.5 x 10(9)/L) occurred in 12 cases (40%) of CHG-treated patients with a mean 8 days of agranulocytic period, so the infectious complications were less serious and tolerable without treatment-related death. (3) Among 14 out of 30 patients with CR, 9 relapsed, the mean duration from CR to replace was 8.2 months. All relapsed patients reusing CHG regimen did not achieved CR again. (4) Among 13 cases with CR, 6 patients just received HA or DA regimens as consolidatory and intensive chemotherapy after CR have relapsed, the mean CR time was only 6.1 months. Otherwise, the mean CR time of 7 CR patients received alternative succeeded chemotherapy containing mitoxantrone/idarubicin/THP/homoharringtonine/daunorubicin/aclarubicin after CR was 10.6 months; and among them 4 are still in continuous CR. It is concluded that the CHG chemotherapy regimen has a similar effect with CAG but better than HA, and in a saft chemotherapy regimen with slight myelosuppression in clinical application, strong and alternative succeeded chemotherapy is necessary for CR patients to keep longer CR and survival.

[Cytotoxicity of IFN-gamma-activated dendritic cells to freshly isolated acute myeloid leukemia cells].

To investigate the tumoricidal activity of dendritic cell (DC) stimulated by interferon-gamma (IFN-gamma) against freshly isolated myeloid leukemia cells and its mechanism, the peripheral blood monocytes collected from healthy donors were cocultured with interleukin-4 and granulocyte-macrophage colony-stimulating factor in medium to induce DC for 7 days. After 12 hour culture in the absence or presence of IFN-gamma, the changes of costimulatory molecules were analyzed with flow cytometry. To assay the cytotoxicity of DC against freshly isolated acute myeloid cells, they were cocultured at various effector-to-target ratio for 18 hours, then the percentage of tumoricidal activity was measured with (51)Cr release assay. To explore the mechanism of DC-mediated cytotoxicity, the change of DC surface or intracellular protein expression of Fas ligand (Fas L), TNF-alpha and TNF related apoptosis-inducing ligand (TRAIL) were analyzed with flow cytometry. The results showed that IFN-gamma enhanced cytotoxicity of DC against AML cells was (33.8 +/- 1.6)% at E:T as 20:1, compared with unstimulated DC (P < 0.05); IFN-gamma up-regulated expression of costimulatory molecules of DC surface such as CD86 and CD83; after stimulation with IFN-gamma, expression of intracellular TRAIL of DC was significantly enhanced, but expression of TRAIL on cell surface of DC was low; while the significant changes of Fas L and TNF-alpha expression neither on cell surface or in cells were not observed before or after stimulation with IFN-gamma. It is concluded that DC stimulated by IFN-gamma exhibit tumoricidal activity against AML cells. The cytotoxicity is partially related to maturation of DC and TRAIL inducing apoptosis, but not associated with death domain-independent mechanism of Fas L and TNF-alpha.