The RNA-binding protein RBP45D of Arabidopsis promotes transgene silencing and flowering time.

RNA-directed DNA methylation (RdDM) helps to defend plants against invasive nucleic acids. In the canonical form of RdDM, 24-nt small interfering RNAs (siRNAs) are produced by DICER-LIKE 3 (DCL3). The siRNAs are loaded onto ARGONAUTE (AGO) proteins leading ultimately to de novo DNA methylation. Here, we introduce the Arabidopsis thaliana prors1 (LUC) transgenic system, in which 24-nt siRNAs are generated to silence the promoter-LUC construct. A forward genetic screen performed with this system identified, besides known components of RdDM (NRPD2A, RDR2, AGO4 and AGO6), the RNA-binding protein RBP45D. RBP45D is involved in CHH (where H is A, C or T) DNA methylation, and maintains siRNA production originating from the LUC transgene. RBP45D is localized to the nucleus, where it is associated with small nuclear RNAs (snRNAs) and small nucleolar RNAs (snoRNAs). RNA-Seq analysis showed that in CRISPR/Cas-mediated rbp-ko lines FLOWERING LOCUS C (FLC) mRNA levels are upregulated and several loci differentially spliced, among them FLM. In consequence, loss of RBP45D delays flowering, presumably mediated by the release of FLC levels and/or alternative splicing of FLM. Moreover, because levels and processing of transcripts of known RdDM genes are not altered in rbp-ko lines, RBP45D should have a more direct function in transgene silencing, probably independent of the canonical RdDM pathway. We suggest that RBP45D facilitates siRNA production by stabilizing either the precursor RNA or the slicer protein. Alternatively, RBP45D could be involved in chromatin modifications, participate in retention of Pol IV transcripts and/or in Pol V-dependent lncRNA retention in chromatin to enable their scaffold function.

Cellulose defects in the Arabidopsis secondary cell wall promote early chloroplast development.

Lincomycin (LIN)-mediated inhibition of protein synthesis in chloroplasts prevents the greening of seedlings, represses the activity of photosynthesis-related genes in the nucleus, including LHCB1.2, and induces the phenylpropanoid pathway, resulting in the production of anthocyanins. In genomes uncoupled (gun) mutants, LHCB1.2 expression is maintained in the presence of LIN or other inhibitors of early chloroplast development. In a screen using concentrations of LIN lower than those employed to isolate gun mutants, we have identified happy on lincomycin (holi) mutants. Several holi mutants show an increased tolerance to LIN, exhibiting de-repressed LHCB1.2 expression and chlorophyll synthesis in seedlings. The mutations responsible were identified by whole-genome single-nucleotide polymorphism (SNP) mapping, and most were found to affect the phenylpropanoid pathway; however, LHCB1.2 expression does not appear to be directly regulated by phenylpropanoids, as indicated by the metabolic profiling of mutants. The most potent holi mutant is defective in a subunit of cellulose synthase encoded by IRREGULAR XYLEM 3, and comparative analysis of this and other cell-wall mutants establishes a link between secondary cell-wall integrity and early chloroplast development, possibly involving altered ABA metabolism or sensing.

VENOSA4, a Human dNTPase SAMHD1 Homolog, Contributes to Chloroplast Development and Abiotic Stress Tolerance.

Chloroplast biogenesis depends on an extensive interplay between the nucleus, cytosol, and chloroplasts, involving regulatory nucleus-encoded chloroplast proteins, as well as nucleocytosolic photoreceptors such as phytochromes (phys) and other extrachloroplastic factors. However, this whole process is only partially understood. Here, we describe the role of VENOSA4 (VEN4) in chloroplast development and acclimation to adverse growth conditions. A 35S:VEN4-eGFP fusion protein localizes to the nucleus in Arabidopsis (Arabidopsis thaliana) protoplasts, and VEN4 homologs are present in a wide range of eukaryotes including humans, where the corresponding homolog (SAMHD1) cleaves dNTPs. Defective photosynthesis in ven4 seedlings results from reduced accumulation of photosynthetic proteins and appears to be caused by a reduction in the translational capacity of chloroplasts. The negative effect of the ven4 mutation on photosynthesis can be phenotypically suppressed by germinating seeds in the presence of excess dCTP or a pool of dNTPs, implying that VEN4, like human SAMHD1, is involved in dNTP catabolism. Moreover, VEN4 activity is also required for optimal responses to cold and salt stresses. In conclusion, our work emphasizes the importance of the nucleocytosolic compartment and the fine-tuning of dNTP levels for chloroplast translation and development.

Extrachloroplastic PP7L Functions in Chloroplast Development and Abiotic Stress Tolerance.

Chloroplast biogenesis is indispensable for proper plant development and environmental acclimation. In a screen for mutants affected in photosynthesis, we identified the protein phosphatase7-like (pp7l) mutant, which displayed delayed chloroplast development in cotyledons and young leaves. PP7L, PP7, and PP7-long constitute a subfamily of phosphoprotein phosphatases. PP7 is thought to transduce a blue-light signal perceived by crys and phy a that induces expression of SIGMA FACTOR5 (SIG5). We observed that, like PP7, PP7L was predominantly localized to the nucleus in Arabidopsis (Arabidopsis thaliana), and the pp7l phenotype was similar to that of the sig6 mutant. However, SIG6 expression was unaltered in pp7l mutants. Instead, loss of PP7L compromised translation and ribosomal RNA (rRNA) maturation in chloroplasts, pointing to a distinct mechanism influencing chloroplast development. Promoters of genes deregulated in pp7l-1 were enriched in PHYTOCHROME-INTERACTING FACTOR (PIF)-binding motifs and the transcriptome of pp7l-1 resembled those of pif and CONSTITUTIVE PHOTOMORPHOGENESIS1 (COP1) signalosome complex (csn) mutants. However, pif and csn mutants, as well as cop1, cryptochromes (cry)1 cry2, and phytochromes (phy)A phyB mutants, do not share the pp7l photosynthesis phenotype. PhyB protein levels were elevated in pp7l mutants, but phyB overexpression plants did not resemble pp7l These results indicate that PP7L operates through a different pathway and that the control of greening and photosystem biogenesis can be separated. The lack of PP7L increased susceptibility to salt and high-light stress, whereas PP7L overexpression conferred resistance to high-light stress. Strikingly, PP7L was specifically recruited to Brassicales for the regulation of chloroplast development. This study adds another player involved in chloroplast biogenesis.

Investigation of the optimal duration of bed rest in the supine position to reduce complications after lumbar puncture combined with intrathecal chemotherapy: a multicenter prospective randomized controlled trial.

PURPOSE: This randomized, open-label trial was conducted to investigate the optimal duration of bed rest after intrathecal chemotherapy to reduce the incidence of complications without increasing patients' tolerance to long-term bed rest. METHODS: A total of 390 patients receiving intrathecal chemotherapy were randomly assigned 1:1:1 to undergo bed rest for 6, 8, or 10 h after intrathecal chemotherapy. The primary outcome was the rate of complications after intrathecal chemotherapy. The analysis was per protocol. RESULTS: A total of 359 patients among the 390 patients in our study completed follow-up with 120 patients in the 6-h group, 120 in the 8-h group, and 119 in the 10-h group. The complications among the three groups differed significantly (P = 0.005). The 6-h group had significantly more complications than the 8- (50, 41.7% vs 29, 24.2%, P = 0.004) and 10-h groups (50, 41.7% vs 31, 26.1%, P = 0.011), whereas the difference between the 8- and 10-h groups was not significant (29, 24.2% vs 31, 26.1%, P = 0.737). CONCLUSIONS: The overall results support that the optimal time interval for bed rest in the supine position after intrathecal chemotherapy is 8 h. This trial is registered with the Chinese Clinical Trial Registry (number ChiCTR-IOR-17011671).

Targeting GLI1 Suppresses Cell Growth and Enhances Chemosensitivity in CD34+ Enriched Acute Myeloid Leukemia Progenitor Cells.

BACKGROUND/AIMS: Resistance of leukemia stem cells (LSCs) to chemotherapy in patients with acute myeloid leukemia (AML) causes relapse of disease. Hedgehog (Hh) signaling plays a critical role in the maintenance and differentiation of cancer stem cells. Yet its role in AML remains controversial. The purpose of the present study is to investigate the role of GLI1, the transcriptional activator of Hh signaling, in AML progenitor cells and to explore the anti-AML effects of GLI small-molecule inhibitor GANT61. METHODS: The expression of GLI1 mRNA and protein were examined in AML progenitor cells and normal cells. The proliferation, colony formation, apoptosis and differentiation of AML progenitor cells were also analyzed in the presence of GANT61. RESULTS: Kasumi-1 and KG1a cells, containing more CD34+ cells, expressed higher level of GLI1 compared to U937 and NB4 cells with fewer CD34+ cells. Consistently, a positive correlation between the protein levels of GLI1 and CD34 was validated in the bone marrow mononuclear cells (BMMC) of AML patients tested. GANT61 inhibited the proliferation and colony formation in AML cell lines. Importantly, GANT61 induced apoptosis in CD34+ enriched Kasumi-1 and KG1a cells, whereas it induced differentiation in U937 and NB4 cells. Furthermore, GANT61 enhanced the cytotoxicity of cytarabine (Ara-c) in primary CD34+ AML cells, indicating that inhibition of GLI1 could be a promising strategy to enhance chemosensitivity. CONCLUSIONS: The present findings suggested that Hh signaling was activated in AML progenitor cells. GLI1 acted as a potential target for AML therapy.

Functional relationship between mTERF4 and GUN1 in retrograde signaling.

Plastid-to-nucleus retrograde signaling plays an important role in regulating the expression of photosynthesis-associated nuclear genes (PhANGs) in accordance with physiological demands on chloroplast biogenesis and function. Despite its fundamental importance, little is known about the molecular nature of the plastid gene expression (PGE)-dependent type of retrograde signaling. PGE is a multifaceted process, and several factors, including pentatricopeptide repeat (PPR) proteins, are involved in its regulation. The PPR protein GUN1 plays a central role in PGE-dependent retrograde signaling. In this study, we isolated a mutant exhibiting up-regulation of CHLOROPHYLL A/B-BINDING PROTEIN (CAB) under normal growth conditions (named coe1 for CAB overexpression 1). The coe1 mutant has a single-base mutation in the gene for mitochondrial transcription termination factor 4 (mTERF4)/BSM/RUG2, which plays a role in regulating the processing of certain plastid transcripts. Defects in GUN1 or mTERF4 de-repressed the expression of specific plastid mRNAs in the presence of lincomycin (LIN). In wild-type plants, treatment with LIN or spectinomycin (SPE) inhibited processing of plastid transcripts. Comparative analysis revealed that in gun1 and coe1/mterf4, but not in wild-type, gun4, or gun5 plants, the processing of plastid transcripts and expression levels of Lhcb1 mRNA were affected in opposite ways when plants were grown in the presence of LIN or SPE. In addition, the coe1 mutation affected the intracellular accumulation and distribution of GUN1, as well as its plastid signaling activity. Taken together, these results suggest that GUN1 and COE1 cooperate in PGE and retrograde signaling.

[Bortezomib-based induction therapy followed by autologous hematopoietic stem cell transplantation in multiple myeloma].

OBJECTIVE: To evaluate the short-term and long-term effect of novel agents followed by autologous hematopoietic stem cell (ASCT) in Chinese multiple myeloma(MM) patients in order to find out the optimal therapeutic regimen for transplant-eligible patients. METHODS: Clinical data of 100 active MM patients receiving bortezomib-based induction regimens followed by high-dose melphalan and ASCT were retrospectively analyzed from June 1, 2006 to January 30, 2014. RESULTS: The overall response rates(ORR) after induction therapy, transplantation and consolidation and maintenance therapy were respectively 90.0%, 97.0%, and 98.9%. The median progress free survival(PFS) was 42.3 months. The median overall survival(OS) was not reached. The cumulative near complete response (nCR)+complete respanse(CR) rate was no longer improved after 4 cycles of induction therapy for non-light chain type MM and two cycles for light-chain type. In newly-diagnosed light-chain type MM patients, the cumulative nCR+CR rate after 4 cycles of bortezomib plus dexamethasone (VD) regimen was similar to that of bortezomib, doxorubicin and dexamethasone (PAD). While for those non-light-chain types, three drug-based regimen was better than two drug-based. PFS of patients receiving early ASCT was longer than that of late ASCT (50.7 months vs 26.6 months, P = 0.023) . PFS in patients receiving autologous bone marrow stem cell transplantation (ABMSCT) was longer than that of autologous peripheral blood stem cell transplantation (APBSCT) (NA vs 36.1 months, P = 0.049) . Maintenance therapy was beneficial regardless of the response rate after ASCT. Patients with CR at any time during the therapy had longer PFS than those with nCR. CONCLUSIONS: Bortezomib-based therapy followed by ASCT is the first line therapy for transplant-eligible MM patients. Patients with different types of M protein require different induction regimens. Maintenance is beneficial to patients after ASCT, no matter whether a CR is reached or not. Patients with CR after induction or ASCT tend to have longer survival.

Identification of a highly drought-resistant pp7l hda6 mutant.

Plants have developed efficient strategies to counteract drought stress, including stomata closure, significant changes in nuclear gene expression, and epigenetic mechanisms. Previously, we identified Arabidopsis thaliana PROTEIN PHOSPHATASE7-LIKE (PP7L) as an extrachloroplastic protein that promotes chloroplast development. In addition, it was shown that PP7L is involved in high light and salt tolerance. Here, we demonstrate that the pp7l mutant can withstand prolonged periods of drought stress. Interestingly, despite impaired growth under standard growth conditions, photosynthetic efficiency recovers in pp7l mutant plants experiencing drought conditions. To assess the (post)transcriptional changes occurring in the pp7l mutant under different durations of drought exposure, we used an RNA-sequencing technique that allows the simultaneous detection of organellar and nuclear transcripts. Compared with the previously reported drought-responsive changes in the wild type, the drought-responsive changes in organellar and nuclear transcripts detected in the pp7l mutant were negligible. Our analysis of the data generated in this study and review and analysis of previous literature motivated us to create a pp7l hda6 (histone deacetylase 6) mutant, which exhibits remarkable drought resistance. Notably, the growth penalty associated with pp7l was alleviated in the double mutant, ruling out a dwarf effect on the drought-tolerant trait of this genotype. Future studies may consider that multiple loci and factors are involved in stress resistance and explore combinations of these factors to create even more resilient plants.

Hepatitis B virus infection status is an independent risk factor for multiple myeloma patients after autologous hematopoietic stem cell transplantation.

The purposes of this study were to evaluate the infection by hepatitis B virus (HBV) and its impact on survival and to provide a clinical reference for monitoring and treating HBV during and after autologous hematopoietic stem cell transplantation (ASCT) in patients with multiple myeloma (MM). A retrospective analysis of HBV infections was performed in 70 MM patients who received a sequential bortezomib-containing induction therapy and ASCT in our department from June 2006 to February 2012. Among the 70 patients in our study, 11 cases (15.7 %) were hepatitis B surface antigen positive (HBsAg+), and 23 cases (33.3 %) were hepatitis B core antibody positive (HBcAb+). Eight cases were HBsAg, hepatitis B e antibody (HBeAb), and HBcAb positive, while one case was HBsAg, hepatitis B e antigen (HBeAg), and HBcAb positive. The median follow-up times for the HBsAg+ group and the HBsAg-negative (HBsAg-) group were 27.0 (7.6-85.2) months and 28.7 (7.1-111.0) months, respectively. The 1-year, 2-year, and 3-year overall survival rates of the HBsAg+ group were 90.9, 80.8, and 34.6 %, respectively, and the median survival time was 31.2 months (95 % CI, 24.8-37.6). The 1-year, 2-year, and 3-year overall survival rates of the HBsAg- group were 98.2, 94, and 84.6 %, respectively, while the median survival time was not yet available. There was a statistically significant difference (p=0.008) in the overall survival rate between the two groups. By Cox regression analysis, we found that the HBsAg+ status was a prognostic factor, which could independently influence the overall survival rate for ASCT. In conclusion, the HBsAg+ status is an independent risk factor for patients with MM receiving ASCT. The application of standard antiviral treatment might help to overcome this risk factor.

Determining the optimal time for bortezomib-based induction chemotherapy followed by autologous hematopoietic stem cell transplant in the treatment of multiple myeloma.

In our study, we determined the efficacy of bortezomib-based induction therapy followed by autologous stem cell transplant (ASCT) in newly diagnosed and relapsed/refractory (R/R) multiple myeloma (MM) patients and compared the advantages of early versus late transplant. We used a retrospective analysis to examine 62 patients, including 46 cases of newly diagnosed MM (early transplant group) and 16 cases of relapsed/refractory MM (late transplant group). All of these patients received bortezomib-based induction therapy followed by ASCT. The efficacy and side effects of the treatment regimen were analyzed. Patients' overall survival (OS) and progression-free survival (PFS) times were determined. The ratio of complete remission to near-complete remission (CR/nCR) was 69.5% versus 56.2% (P=0.361), respectively, for the early transplant group versus the late transplant group, respectively, after receiving bortezomib-based induction therapy; the overall response rates of the two group were 91.3% and 81.2%, respectively (P=0.369). After receiving ASCT, the CR/nCR of the two groups increased to 84.8% and 81.3%, respectively. The median time required for neutrophil engraftment of the early transplant group and the late transplant group was 11 and 14.5 days, respectively (P=0.003); the median time required for platelet engraftment was 13 and 21.5 days (P=0.031), respectively. There were no significant differences in the toxic side effects observed during induction therapy and ASCT between the two groups. The OS of the two groups was not statistically different (P=0.058). The PFS of the early transplant group and the late transplant group was 41.6 and 26.5 months, respectively (P=0.008). Multivariate analysis demonstrated that the time of receiving ASCT, the types of M protein, and the International Staging System (ISS) stage were all independent factors that influenced PFS. In conclusion, patients in a suitable condition for ASCT should be recommended to have an early ASCT immediately after diagnosis.

The effect of varicella-zoster virus reactivation on the long-term outcomes of patients undergoing allogeneic hematopoietic stem cell transplantation.

BACKGROUND: A virus infection may lead the body to produce more immune cells of particular types or stimulate the production of new ones, both of which may have anti-leukemic effects. There has been no research on whether immune cells stimulated by varicella-zoster virus (VZV) infection have anti-leukemic effects. The objective of this investigation is to assess the impact of VZV infection on patients' long-term survival following allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: This retrospective study investigated the association between varicella-zoster virus (VZV) reactivation and outcomes in 219 individuals who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the Sun Yat-sen University's First Affiliated Hospital. According to being diagnosed with VZV infection or not, these patients were grouped into two groups. The comparison of cumulative incidence of relapse, non-recurrent mortality, and overall survival (OS) was conducted between the two groups. RESULTS: Analyzing multivariate data, VZV reactivation was linked to lower relapse incidence in the group containing all individuals (hazard ratio [HR] = 0.27; 95% confidence interval [CI], 0.12-0.64), patients suffering from acute myeloid leukaemia (HR = 0.10; 95% CI, 0.01-0.83), and patients suffering from acute lymphoblastic leukaemia (HR = 0.25; 95% CI, 0.08-0.77). Moreover, VZV reactivation was linked with decreased non-relapse mortality in all individuals (HR = 0.20; 95% CI, 0.05-0.79), but no statistical significance was found for any disease subgroup. Further, VZV reactivation was an independent predictor for improved OS in the group containing all individuals (HR = 0.10; 95% CI, 0.03-0.29), patients suffering from acute myeloid leukaemia (HR = 0.09; 95% CI, 0.01-0.66), and patients suffering from acute lymphoblastic leukaemia (HR = 0.16; 95% CI, 0.04-0.68). CONCLUSION: This is the first study to show that VZV reactivation following allo-HSCT is an independent predictor for lower relapse rates and improved OS, providing novel therapeutic approaches to improve patients' long-term survival following allo-HSCT.

Response of the organellar and nuclear (post)transcriptomes of Arabidopsis to drought.

Plants have evolved sophisticated mechanisms to cope with drought, which involve massive changes in nuclear gene expression. However, little is known about the roles of post-transcriptional processing of nuclear or organellar transcripts and how meaningful these changes are. To address these issues, we used RNA-sequencing after ribosomal RNA depletion to monitor (post)transcriptional changes during different times of drought exposure in Arabidopsis Col-0. Concerning the changes detected in the organellar transcriptomes, chloroplast transcript levels were globally reduced, editing efficiency dropped, but splicing was not affected. Mitochondrial transcripts were slightly elevated, while editing and splicing were unchanged. Conversely, alternative splicing (AS) affected nearly 1,500 genes (9% of expressed nuclear genes). Of these, 42% were regulated solely at the level of AS, representing transcripts that would have gone unnoticed in a microarray-based approach. Moreover, we identified 927 isoform switching events. We provide a table of the most interesting candidates, and as proof of principle, increased drought tolerance of the carbonic anhydrase ca1 and ca2 mutants is shown. In addition, altering the relative contributions of the spliced isoforms could increase drought resistance. For example, our data suggest that the accumulation of a nonfunctional FLM (FLOWERING LOCUS M) isoform and not the ratio of FLM-ß and -δ isoforms may be responsible for the phenotype of early flowering under long-day drought conditions. In sum, our data show that AS enhances proteome diversity to counteract drought stress and represent a valuable resource that will facilitate the development of new strategies to improve plant performance under drought.

The epithelial sodium channel is involved in dexamethasone-induced osteoblast differentiation and mineralization.

PURPOSE: Glucocorticoids (GCs) can facilitate bone formation, but prolonged GCs exposure in vivo can lead to osteoporosis. The mechanisms underlying these reciprocal effects have not been elucidated. METHODS: The epithelial sodium channel (ENaC) is a possible regulator of osteoblast proliferation and differentiation, so we examined whether ENaC was involved in mediating the effects of dexamethasone (Dex) on osteoblast. RESULT: Expression of the functional α-ENaC subunit was upregulated by 10(-8)M and 10(-6)M Dex, but decreased by 10(-4)M Dex. Furthermore, Dex had similar dose-dependent effects on the expression of three osteogenic genes, Cbfa1, OPN, and OC, with low concentrations enhancing expression and higher concentrations suppressing expression. The effects of Dex on osteoblast proliferation, differentiation, and mineralization were examined in the presence and absence of the ENaC specific antagonist amiloride. Dex at 10(-8)M and 10(-6)M markedly increased osteoblast proliferation, alkaline phosphatase activity (an index of differentiation), and calcium nodule formation, while 10(-4)M had no effect or suppressed all these responses. Amiloride blocked the Dex-induced, osteoblast differentiation and mineralization but had no effect on osteoblast differentiation and mineralization when applied alone. But such changes did not show in osteoblast proliferation. However, the Dex-induced α-ENaC expression was not blocked by RU486, a GC receptor antagonist. CONCLUSION: These results suggest that changes in ENaC activity may involved in Dex-induced differentiation and mineralization of osteoblast. But the Dex-induced effect on ENaC did not mediated by the GC genomic mechanism in osteoblast at this study.

[The efficacy and safety of bortezomib-based induction regimen before autologous hematopoietic stem cell transplantation in patients with multiple myeloma].

OBJECTIVE: To investigate the efficacy and safety of bortezomib-based induction regimen followed by autologous hematopoietic stem cell transplantation (ASCT) in patients with multiple myeloma (MM). METHODS: A retrospective analysis was performed upon clinical data of 62 MM patients who received bortezomib-based induction regimen followed by ASCT from June 2006 to June 2011. All patients were followed up to September 30, 2011. RESULTS: Overall response rate [complete remission (CR) + near complete remission (nCR) + partial remission (PR)], ≥ nCR rate (CR/nCR) and CR rate of post-induction with bortezomib-based regimen were 88.7%, 66.1% and 24.2%, respectively. After ASCT, CR rate and CR/nCR rate were increased to 50.0% and 82.3%, respectively, with significant differences (P = 0.003 and P = 0.032). The median time of neutrophil and platelet engraftment was 12.0 (9 - 43) days and 13.5 (0 - 120) days, respectively. Significances were found in neutrophil and platelet engraftment between MM patients with and without prior exposure to alkylating agents. Furthermore, engraftment of neutrophil and platelet in patients receiving peripheral blood stem cell transplantation were faster than those receiving bone marrow transplantation. No unexpected side effects occurred. The median time of follow-up was 26.5 (7-61) months. The median overall survival (OS) was not reached and the median progression-free survival (PFS) was 30 months. There were significant differences in OS and PFS between patients obtaining CR/nCR and those with ≤ PR before ASCT. CONCLUSIONS: Bortezomib-based induction regimen can improve the efficacy of ASCT in MM patients. The side effects are tolerant. Higher response quality before ASCT can translate to high rates of OS and PFS following high-dose therapy and stem cell transplantation.

Receptor activator of NF-{kappa}B (RANK) cytoplasmic IVVY535-538 motif plays an essential role in tumor necrosis factor-{alpha} (TNF)-mediated osteoclastogenesis.

Tumor necrosis factor-α (TNF) enhances osteoclast formation and activity leading to bone loss in various pathological conditions, but its precise role in osteoclastogenesis remains controversial. Although several groups showed that TNF can promote osteoclastogenesis independently of the receptor activator of NF-κB (RANK) ligand (RANKL), others demonstrated that TNF-mediated osteoclastogenesis needs permissive levels of RANKL. Here, we independently reveal that although TNF cannot stimulate osteoclastogenesis on bone slices, it can induce the formation of functional osteoclasts on bone slices in the presence of permissive levels of RANKL or from bone marrow macrophages (BMMs) pretreated by RANKL. TNF can still promote the formation of functional osteoclasts 2 days after transient RANKL pretreatment. These data have confirmed that TNF-mediated osteoclastogenesis requires priming of BMMs by RANKL. Moreover, we investigated the molecular mechanism underlying the dependence of TNF-mediated osteoclastogenesis on RANKL. RANK, the receptor for RANKL, contains an IVVY(535-538) motif that has been shown to play a vital role in osteoclastogenesis by committing BMMs to the osteoclast lineage. We show that TNF-induced osteoclastogenesis depends on RANKL to commit BMMs to the osteoclast lineage and RANKL regulates the lineage commitment through the IVVY motif. Mechanistically, the IVVY motif controls the lineage commitment by reprogramming osteoclast genes into an inducible state in which they can be activated by TNF. Our findings not only provide important mechanistic insights into the action of RANKL in TNF-mediated osteoclastogenesis but also establish that the IVVY motif may serve as an attractive therapeutic target for bone loss in various bone disorders.

Interleukin-4 inhibits RANKL-induced NFATc1 expression via STAT6: a novel mechanism mediating its blockade of osteoclastogenesis.

Interleukin-4 (IL-4) is an important immune regulatory protein that possesses potent anti-osteoclastogenic properties, and does so via the transcription factor STAT6. Previous studies have shown that IL-4 selectively blocks RANKL-induced activation of NF-κB and mitogen-activated protein kinase (MAPK) pathway molecules, suggesting that the cytokine arrests osteoclastogenesis by blockade of these signaling cascades. However, the fact that the inhibitory effect on these pathways requires prolonged IL-4 pretreatment, and that the cytokine fails to exert an anti-osteoclastogenic effect after short-term pre-exposure of RANKL to osteoclast precursors, suggests that an additional, more immediate mechanism may also be involved. In this study, we found that simultaneous exposure of IL-4 did not alter RANKL-dependent activation of NF-κB or MAPKs, whereas the cytokine did block RANKL-induced nuclear factor activated T cells c1 (NFATc1), a master osteoclastogenic transcription factor. This inhibitory effect of IL-4 required STAT6, consistent with its functional role in osteoclastogenesis. In addition, the cytokine also partially impaired RANKL-stimulated bone resorption. Furthermore, IL-4 suppressed expression of RANKL-induced osteoclast specific genes in a STAT6-dependent manner, but failed to do so when osteoclast precursors were pre-exposed to RANKL. Thus, we provide the first evidence that IL-4 inhibits osteoclast formation by inhibiting RANKL induction of NFATc1 via STAT6 as an early event, in addition to its suppression of other signaling pathways. The inhibitory effect is ultimately regulated at the gene expression transcriptional level.

Inhibition of mitotic kinase Aurora suppresses Akt-1 activation and induces apoptotic cell death in all-trans retinoid acid-resistant acute promyelocytic leukemia cells.

BACKGROUND: Aurora kinase ensures accurate chromosome segregation during cell cycle, maintaining genetic integrity in cell division. VX-680, a small-molecule Aurora kinase inhibitor, interferes with mitotic entry and formation of bipolar spindles. Here, we evaluated VX-680 as a potential agent for treatment of all-trans retinoid acid (ATRA)-resistant acute promyelocytic leukemia (APL) in vitro. METHODS: CD11b expression was utilized to assess cell differentiation by flow cytometry. Immunofluorescence staining was conducted to analyze formation of cell monopolar spindle. Cell proliferation was evaluated by MTT assay. Sub-G1 population and Annexin V/PI staining were used to measure cell apoptosis. Hoechst 33342 staining was applied for identifying morphological changes in nucleus of apoptotic cell. Aurora-A (Aur-A) activation and the signaling pathways involved in apoptosis were detected by Western blot. JC-1 probe was employed to measure mitochondrial depolarization. RESULTS: VX-680 inhibited Aur-A by reducing autophosphorylation at the activation site, Thr288, accompanied by producing monopolar mitotic spindles in APL cell line NB4-R2 that was resistant to ATRA. In addition, we found that VX-680 inhibited cell proliferation as assessed by MTT assay. Flow cytometry showed that VX-680 led to apoptotic cell death in both dose- and time-dependent manners by either Sub-G1 or Annexin V/PI analysis. Hoechst 33342 staining represented typical apoptotic cells with nuclear fragmentation in VX-680 treated cells. Importantly, VX-680 inhibition of Aurora kinase suppressed Akt-1 activation and induced mitochondrial depolarization, which eventually resulted in apoptosis by activation of caspase pathway, as indicated by increasing proteolytic cleavage of procaspase-3 and poly ADP ribose polymerase (PARP) in NB4-R2 cells. CONCLUSIONS: Our study suggested potential clinical use of mitotic Aurora kinase inhibitor in targeting ATRA-resistant leukemic cells.

Curcumin reduces expression of Bcl-2, leading to apoptosis in daunorubicin-insensitive CD34+ acute myeloid leukemia cell lines and primary sorted CD34+ acute myeloid leukemia cells.

BACKGROUND: Acute myeloid leukemia (AML) is an immunophenotypically heterogeneous malignant disease, in which CD34 positivity is associated with poor prognosis. CD34+ AML cells are 10-15-fold more resistant to daunorubicin (DNR) than CD34- AML cells. Curcumin is a major component of turmeric that has shown cytotoxic activity in multiple cancers; however, its anti-cancer activity has not been well studied in DNR-insensitive CD34+ AML cells. The aim of this study was to therefore to explore curcumin-induced cytotoxicity in DNR-insensitive CD34+ AML cell lines (KG1a, Kasumi-1), DNR-sensitive U937 AML cells, and primary CD34+ AML bone-marrow-derived cells. METHODS: Primary human CD34+ cells were isolated from peripheral blood mononuclear cells or bone marrow mononuclear cells using a CD34 MicroBead kit. The growth inhibitory effects of curcumin were evaluated by MTT and colony-formation assays. Cell cycle distribution was examined by propidium iodide (PI) assay. Apoptosis was analyzed by Wright-Giemsa, Hoechst 33342 and Annexin-V/PI staining assays. The change in mitochondrial membrane potential (MMP) was examined by JC-1 staining and flow cytometry. Expression of apoptosis-related proteins was determined by reverse transcription-polymerase chain reaction and Western blotting. Short interfering RNA (siRNA) against Bcl-2 was used in CD34+ KG1a and Kasumi-1 cells incubated with/without DNR. RESULTS: Curcumin inhibited proliferation and induced apoptosis and G1/S arrest in both DNR-insensitive KG1a, Kasumi-1 and DNR-sensitive U937 cells. Curcumin-induced apoptosis was associated with reduced expression of both Bcl-2 mRNA and protein, subsequent loss of MMP, and activation of caspase-3 followed by PARP degradation. Curcumin synergistically enhanced the cytotoxic effect of DNR in DNR-insensitive KG1a and Kasumi-1 cells, consistent with decreased Bcl-2 expression. Accordingly, siRNA against Bcl-2 increased the susceptibility of KG1a and Kasumi-1 cells to DNR-induced apoptosis. More importantly, curcumin suppressed Bcl-2 expression, selectively inhibited proliferation and synergistically enhanced the cytotoxicity of DNR in primary CD34+ AML cells, while showing limited lethality in normal CD34+ hematopoietic progenitors. CONCLUSION: Curcumin down-regulates Bcl-2 and induces apoptosis in DNR-insensitive CD34+ AML cell lines and primary CD34+ AML cells.