AcHZP45 is a repressor of chlorophyll biosynthesis and activator of chlorophyll degradation in kiwifruit.

The degradation of chlorophyll during fruit development is essential to reveal a more 'ripe' color that signals readiness to wild dispersers of seeds and the human consumer. Here, comparative biochemical analysis of developing fruit of Actinidia deliciosa cv. Xuxiang ('XX', green-fleshed) and Actinidia chinensis cv. Jinshi No.1 ('JS', yellow-fleshed) indicated that variation in chlorophyll content is the major contributor to differences in flesh color. Four differentially expressed candidate genes were identified: the down-regulated genes AcCRD1 and AcPOR1 involved in chlorophyll biosynthesis, and the up-regulated genes AcSGR1 and AcSGR2 driving chlorophyll degradation. Prochlorophyllide and chlorophyllide, the metabolites produced by AcCRD1 and AcPOR1, progressively reduced in 'JS', but not in 'XX', indicating that chlorophyll biosynthesis was less active in yellow-fleshed fruit. AcSGR1 and AcSGR2 were verified to be involved in chlorophyll degradation, using both transient expression in tobacco and stable overexpression in kiwifruit. Furthermore, a homeobox-leucine zipper (HD-Zip II), AcHZP45, showed significantly increased expression during 'JS' fruit ripening, which led to both repressed expression of AcCRD1 and AcPOR1 and activated expression of AcSGR1 and AcSGR2. Collectively, the present study indicated that different dynamics of chlorophyll biosynthesis and degradation coordinate the changes in chlorophyll content in kiwifruit flesh, which are orchestrated by the key transcription factor AcHZP45.

Nore1 inhibits age-associated myeloid lineage skewing and clonal hematopoiesis but facilitates termination of emergency (stress) granulopoiesis.

Age-associated bone marrow changes include myeloid skewing and mutations that lead to clonal hematopoiesis. Molecular mechanisms for these events are ill defined, but decreased expression of Irf8/Icsbp (interferon regulatory factor 8/interferon consensus sequence binding protein) in aging hematopoietic stem cells may contribute. Irf8 functions as a leukemia suppressor for chronic myeloid leukemia, and young Irf8-/- mice have neutrophilia with progression to acute myeloid leukemia (AML) with aging. Irf8 is also required to terminate emergency granulopoiesis during the innate immune response, suggesting this may be the physiologic counterpart to leukemia suppression by this transcription factor. Identifying Irf8 effectors may define mediators of both events and thus contributors to age-related bone marrow disorders. In this study, we identified RASSF5 (encoding Nore1) as an Irf8 target gene and investigated the role of Nore1 in hematopoiesis. We found Irf8 activates RASSF5 transcription and increases Nore1a expression during emergency granulopoiesis. Similar to Irf8-/- mice, we found that young Rassf5-/- mice had increased neutrophils and progressed to AML with aging. We identified enhanced DNA damage, excess clonal hematopoiesis, and a distinct mutation profile in hematopoietic stem cells from aging Rassf5-/- mice compared with wildtype. We found sustained emergency granulopoiesis in Rassf5-/- mice, with repeated episodes accelerating AML, also similar to Irf8-/- mice. Identifying Nore1a downstream from Irf8 defines a pathway involved in leukemia suppression and the innate immune response and suggests a novel molecular mechanism contributing to age-related clonal myeloid disorders.

Prevalence and clinical characteristics of autoimmune liver disease in hospitalized patients with cirrhosis and acute decompensation in China.

BACKGROUND: Autoimmune liver disease (AILD) has been considered a relatively uncommon disease in China, epidemiological data for AILD in patients with cirrhosis and acute decompensation (AD) is sparse. AIM: To investigate the prevalence, outcome and risk factors for AILD in cirrhotic patients complicated with AD in China. METHODS: We collected data from patients with cirrhosis and AD from two prospective, multicenter cohorts in hepatitis B virus endemic areas. Patients were regularly followed up at the end of 28-d, 90-d and 365-d, or until death or liver transplantation (LT). The primary outcome in this study was 90-d LT-free mortality. Acute-on-chronic liver failure (ACLF) was assessed on admission and during 28-d hospitalization, according to the diagnostic criteria of the European Association for the Study of the Liver (EASL). Risk factors for death were analyzed with logistic regression model. RESULTS: In patients with cirrhosis and AD, the overall prevalence of AILD was 9.3% (242/2597). Prevalence of ACLF was significantly lower in AILD cases (14%) than those with all etiology groups with cirrhosis and AD (22.8%) (P < 0.001). Among 242 enrolled AILD patients, the prevalence rates of primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH) and PBC-AIH overlap syndrome (PBC/AIH) were 50.8%, 28.5% and 12.0%, respectively. In ACLF patients, the proportions of PBC, AIH and PBC/AIH were 41.2%, 29.4% and 20.6%. 28-d and 90-d mortality were 43.8% and 80.0% in AILD-related ACLF. The etiology of AILD had no significant impact on 28-d, 90-d or 365-d LT-free mortality in patients with cirrhosis and AD in both univariate and multivariate analysis. Total bilirubin (TB), hepatic encephalopathy (HE) and blood urea nitrogen (BUN) were independent risk factors for 90-d LT-free mortality in multivariate analysis. The development of ACLF during hospitalization only independently correlated to TB and international normalized ratio. CONCLUSION: AILD was not rare in hospitalized patients with cirrhosis and AD in China, among which PBC was the most common etiology. 90-d LT-free mortality were independently associated with TB, HE and BUN.

An unusual indole-diterpenoid with C-17 norcassane skeleton from Euphorbia fischeriana induces HEL cell cycle arrest and apoptosis.

Two new polycyclic diterpenoids, euphkanoids H and I (1 and 2), along with 6 known analogues (2-8) were isolated from the roots of Euphorbia fischeriana, a traditional Chinese medicine. Their structures were identified by spectral methods, and the absolute configurations of 1 and 2 were determined by ECD calculation and single crystal X-ray diffraction, respectively. Compound 1 represents the first example of C-17 norcassane indole-diterpenes. All the isolates were screened for antiproliferative activity against a panel of human cancer cell lines using the MTT assay, and 1 showed significant cytotoxicity against HEL cells (IC50 = 3.2 µM). Simple mechanistic study revealed that 1 could induce cell cycle arrest at G0/G1 phase and apoptosis in HEL cells.

[Establishment of primary liver cancer model in mice].

Objective: Three modeling methods were used to establish a mouse primary liver cancer model, and compared them to find a more optimal modeling method. Methods: Forty 15-day-old C3H/HeN male mice were randomly divided into groups I-IV, 10 mice in each group. Group Ⅰ were not treated; Group Ⅱ were intraperitoneally injected with 25 mg/kg diethylnitrosamine (DEN) once; Group Ⅲ were intraperitoneally injected with 100 mg/kg DEN once; Group Ⅳ were intraperitoneally injected with 25 mg/kg DEN once and followed by another intraperitoneal injection of 100 mg/kg DEN at 42 days of age. The mortality of mice in each group was analyzed. At the 18th week of modeling, blood was collected from eyeballs after anesthesia, and liver was taken from abdominal cavity after neck was broken. The appearance of liver, the number of cancer nodules and the incidence of liver tumor were observed. The histopathological changes of liver were observed by HE staining. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected. Results: At the 18th week of modeling, compared with the group I, serum levels of ALT and AST in groups II-IV were increased significantly (P＜0.05); The number of cancer nodules and the incidence of tumors in the surviving mice of groups III and IV were also increased significantly (P＜0.05). At the 18th week of modeling, no mice died in both groups I and II, and the incidence of liver cancer was 0%; The incidence of liver cancer in surviving mice in both groups III and IV was 100%, but the mortality rate of mice in group III was as high as 50%, and that in group IV was only 20%. Conclusion: C3H/HeN male mice can successfully establish a mouse liver cancer model by intraperitoneal injection of 25 mg/kg of DEN once at the age of 15 days and another intraperitoneal injection of 100 mg/kg of DEN once at the age of 42 days with short cycle and low mortality, which is an ideal method to establish a primary liver cancer model.

An ethylene-hypersensitive methionine sulfoxide reductase regulated by NAC transcription factors increases methionine pool size and ethylene production during kiwifruit ripening.

Ethylene plays an important role in regulating fruit ripening by triggering dynamic changes in expression of ripening-associated genes, but the functions of many of these genes are still unknown. Here, a methionine sulfoxide reductase gene (AdMsrB1) was identified by transcriptomics-based analysis as the gene most responsive to ethylene treatment in ripening kiwifruit. The AdMsrB1 protein exhibits a stereospecific activity toward the oxidative stress-induced R enantiomer of methionine sulfoxide (MetSO), reducing it to methionine (Met). Stable overexpression of AdMsrB1 in kiwifruit significantly increased the content of free Met and 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, and increased ethylene production. Dual-luciferase assays indicated that the AdMsrB1 promoter was not directly upregulated by ethylene treatment but was modulated by two ethylene-inducible NAM/ATAF/CUC transcription factors (AdNAC2 and AdNAC72) that bind directly to the AdMsrB1 promoter. Overexpression of AdNAC72 in kiwifruit not only enhanced AdMsrB1 expression, but also increased free Met and ACC content and ethylene production rates. This finding establishes an unexpected regulatory loop that enhances ethylene production and the concentration of its biosynthetic intermediates.

Methyl Jasmonate Enhances Ethylene Synthesis in Kiwifruit by Inducing NAC Genes That Activate ACS1.

Cross-talk between various hormones is important in regulating many aspects of plant growth, development, and senescence, including fruit ripening. Here, exogenous ethylene (ETH, 100 µL/L, 12 h) rapidly accelerated 'Hayward' kiwifruit (Actinidia deliciosa) softening and ethylene production and was enhanced by supplementing with continuous treatment with methyl jasmonate (MeJA, 100 µM/L, 12 h) (ETH+MeJA). ETH+MeJA enhanced ACC synthase (ACS) activities and 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation but not ACC oxidase (ACO) activity. Increased transcripts of ACS genes AdACS1 and AdACS2, ACS activity, and ethylene production were positively correlated. The abundance of AdACS1 was about 6-fold higher than AdACS2. RNA-seq identified 6 transcription factors among the 87 differentially expressed unigenes induced by ETH+MeJA. Dual-luciferase and electrophoretic mobility shift assays (EMSA) indicated that AdNAC2/3 physically interacted with and trans-activated the AdACS1 promoter 2.2- and 3.5-fold, respectively. Collectively, our results indicate that MeJA accelerates ethylene production in kiwifruit induced by exogenous ethylene, via a preferential activation of AdACS1 and AdACS2.

Inhibition of Fas associated phosphatase 1 (Fap1) facilitates apoptosis of colon cancer stem cells and enhances the effects of oxaliplatin.

Fas associated phosphatase 1 (Fap1) is a ubiquitously expressed protein tyrosine phosphatase. Fap1 substrates include Fas and Gsk3ß, suggesting a role in regulating cell survival. Consistent with this, increased Fap1 expression is associated with resistance to Fas or platinum induced apoptosis in some human colon cancer tumors or cell lines. In the current studies, we found that Fap1 expression was significantly greater in CD133+ colon cancer stem cells compared to CD133- tumor cells. PTPN13 promoter activity (encoding Fap1) was repressed by interferon regulatory factor 2 (irf2), and expression of Fap1 and Irf2 were inversely correlated in CD133+ or CD133- colon cancer cells. We determined that CD133+ cells were relatively resistant to Fas or oxaliplatin induced apoptosis, but this was reversed by Fap1-knockdown or a Fap1-blocking tripeptide (SLV). In a murine xenograft model of colon cancer, we found treatment with SLV peptide significantly decreased tumor growth and relative abundance of CD133+CD44+ cells; associated with increased phosphorylation of Fap1 substrates. SLV peptide also enhanced inhibitory effects of oxaliplatin on tumor growth and Fap1 substrate phosphorylation in this model. Our studies suggest that therapeutically targeting Fap1 may decrease persistence of colon cancer stem cells during treatment with platinum chemotherapy by activating Fap1 substrates. In a murine model of chronic myeloid leukemia, we previously determined that inhibition of Fap1 decreased persistence of leukemia stem cells during tyrosine kinase inhibitor treatment. Therefore, Fap1 may be a tissue agnostic target to increase apoptosis in malignant stem cells.

The E3 ubiquitin ligase Triad1 influences development of Mll-Ell-induced acute myeloid leukemia.

Chromosomal translocations involving the MLL1 gene characterize a poor prognosis subset of acute myeloid leukemia (AML), referred to as 11q23-AML. Transcription of the HOXA9 and HOXA10 genes is enhanced in hematopoietic stem and progenitor cells in these leukemias. We previously found the ARIH2 gene was repressed by HoxA9 in myeloid progenitors, but activated by HoxA10 during granulopoiesis. ARIH2 encodes the Triad1 protein, an anti-proliferative E3 ubiquitin ligase. In the current study, we investigate the role of Triad1 in leukemogenesis induced by an MLL1 fusion protein (Mll-Ell). We found Mll-Ell increased expression of HoxA9, HoxA10, and Triad1 because HoxA9 represses only one of two ARIH2 cis elements that are activated by HoxA10. Although Triad1 antagonized the generally pro-proliferative effects of the Mll-Ell oncoprotein, we found blocking HoxA9 and HoxA10 phosphorylation shifted the balance to ARIH2 repression in Mll-Ell+ cells. We investigated the significance of these in vitro results in a murine bone marrow transplant model. We found Triad1 knockdown significantly shortened the latency to development of AML in mice transplanted with Mll-Ell-transduced bone marrow. And, Triad1 expression fell during the prolonged AML latency period in mice transplanted with bone marrow expressing Mll-Ell alone. Our studies identify Triad1 as a leukemia suppressor in 11q23-AML. This suggests defining relevant Triad1 substrates may indicate novel therapeutic targets in this disease.

TP53 Haploinsufficiency Rescues Emergency Granulopoiesis in FANCC-/- Mice.

Emergency (stress) granulopoiesis is an episodic process for the production of granulocytes in response to infectious challenge. We previously determined that Fanconi C, a component of the Fanconi DNA-repair pathway, is necessary for successful emergency granulopoiesis. Fanconi anemia results from mutation of any gene in this pathway and is characterized by bone marrow failure (BMF) in childhood and clonal progression in adolescence. Although murine Fanconi anemia models exhibit relatively normal steady-state hematopoiesis, FANCC-/- mice are unable to mount an emergency granulopoiesis response. Instead, these mice develop BMF and die during repeated unsuccessful emergency granulopoiesis attempts. In FANCC-/- mice, BMF is associated with extensive apoptosis of hematopoietic stem and progenitor cells through an undefined mechanism. In this study, we find that TP53 haploinsufficiency completely rescues emergency granulopoiesis in FANCC-/- mice and protects them from BMF during repeated emergency granulopoiesis episodes. Instead, such recurrent challenges accelerated clonal progression in FANCC-/-TP53+/- mice. In FANCC-/- mice, BMF during multiple emergency granulopoiesis attempts was associated with increased ataxia telangiectasia and Rad3-related protein (Atr) and p53 activation with each attempt. In contrast, we found progressive attenuation of expression and activity of Atr, and consequent p53 activation and apoptosis, in the bone marrow of FANCC-/-TP53+/- mice during this process. Therefore, activation of Atr-with consequent Fanconi-mediated DNA repair or p53-dependent apoptosis-is an essential component of emergency granulopoiesis and it protects the bone marrow from genotoxic stress during this process.

Decreased calpain activity in chronic myeloid leukemia impairs apoptosis by increasing survivin in myeloid progenitors and xiap1 in differentiating granulocytes.

Chronic Myeloid Leukemia (CML) is characterized by translocations between chromosomes 9 and 22, resulting in expression of Bcr-abl oncogenes. Although the clinical course of CML was revolutionized by development of Bcr-abl-directed tyrosine kinase inhibitors (TKIs), CML is not cured by these agents. Specifically, the majority of subjects relapsed in clinical trials attempting TKI discontinuation, suggesting persistence of leukemia stem cells (LSCs) even in molecular remission. Identifying mechanisms of CML-LSC persistence may suggest rationale therapeutic targets to augment TKI efficacy and lead to cure. Apoptosis resistance is one proposed mechanism. In prior studies, we identified increased expression of Growth Arrest Specific 2 (Gas2; a Calpain inhibitor) in Bcr-abl+ bone marrow progenitor cells. A number of previously described Calpain substrates might influence apoptosis in CML, including ßcatenin and the X-linked Inhibitor of Apoptosis Protein 1 (Xiap1). We previously found Gas2/Calpain dependent stabilization of ßcatenin in CML, and increased expression of ßcatenin target genes, including Survivin (also an IAP). In the current work, we investigate contributions of Survivin and Xiap1 to Fas-resistance in Bcr-abl+ bone marrow cells. Inhibitors of these proteins are currently in clinical trials for other malignancies, but a role for either IAP in CML-LSC persistence is unknown.

Tanshinone IIA decreases the levels of inflammation induced by Aß1-42 in brain tissues of Alzheimer's disease model rats.

To study the pathogenesis of Alzheimer's disease (AD) and explore the possible anti-inflammatory mechanism of tanshinone IIA (TanIIA), we evaluated the quantity of neurons and the expression levels of interleukin-1ß (IL-1ß), IL-6, glial fibrillary acidic protein, CD11b, C1q, C3c, and C3d in brain tissues of AD rats treated with TanIIA. Thirty male Sprague-Dawley rats were randomized into three groups: sham group, TanIIA treatment group, and Aß1-42 group. Aß1-42 treatment was performed by injecting Aß into the hippocampus of rats and then tagged position. Brain tissue morphological structure has been observed with HE staining and the staining of exogenously injected Aß1-42 was observed by immunohistochemistry, which confirms the success of the Aß1-42 group. After TanIIA treatment, levels of IL-1ß, IL-6, glial fibrillary acidic protein, CD11b, C1q, C3c, and C3d were measured in paraffinized brain tissue sections from all groups by immunohistochemistry staining. The results showed that no 6E10 was detected in the control group, and the difference in the expression levels of 6E10 between the Aß1-42 group and the TanIIA treatment group was not significant (P>0.05), suggesting that both the Aß1-42 group and the TanIIA treatment group received the same amount of Aß. The Aß1-42 group showed a significant increase in the expression levels of inflammatory markers compared with the sham group (P<0.05) and the TanIIA treatment group showed a partial improvement in reducing inflammation. Therefore, Aß triggered brain inflammation and activated the complement system. TanIIA treatment reduced the number of astrocytes and microglial cells, and induced a partial decrease in complement molecules in the brain of AD rats. These findings suggested that TanIIA may represent a potential therapeutic treatment in neurodegenerative diseases such as AD to support the survival of neurons by reducing expression levels of inflammatory factors.

Cooperation between AlphavBeta3 integrin and the fibroblast growth factor receptor enhances proliferation of Hox-overexpressing acute myeloid leukemia cells.

A poor prognosis subtype of acute myeloid leukemia (AML) is characterized by increased expression of a set of homeodomain (HD) transcription factors, including HoxA9, HoxA10 and Cdx4. This encompasses AML with MLL1 gene translocations, because Mll1-fusion proteins aberrantly activate HOX transcription. We previously identified FGF2 (Fibroblast Growth Factor 2) as a target gene for HoxA9 and HoxA10 that was indirectly activated by Mll-Ell (an Mll1-fusion protein). Autocrine stimulation of Mll-Ell+ myeloid progenitor cells by Fgf2 stabilized ßcatenin and increased expression of ßcatenin target genes, including CDX4. Since HOXA9 and HOXA10 are Cdx4 target genes, Fgf2 indirectly augmented direct effects of Mll-Ell on these genes. ITGB3, encoding ß3 integrin, is another HoxA10 target gene. In the current studies, we found activation of ITGB3 transcription in Mll-Ell+ myeloid progenitor cells via HoxA9 and HoxA10. Increased expression of αvß3 integrin increased Syk-activation; contributing to cytokine hypersensitivity. However, inhibiting Fgf-R partly reversed αvß3 activity in Mll-Ell+ progenitor cells by decreasing ITGB3 promoter activity in a ßcatenin- and Cdx4-dependent manner. Inhibitors of Fgf-R or Syk impaired proliferation of CD34+ bone marrow cells from AML subjects with increased Hox-expression; with a greater combined effect. These studies identified a rational therapeutic approach to this AML subtype.

Tanshinone IIA increases levels of NeuN, protein disulfide isomerase, and Na+/K+-ATPase and decreases evidence of microglial activation after cerebral ischemic injury.

This study was designed to clarify the neuroprotective effects of tanshinone IIA (TSA) following cerebral ischemic insult. Adult Sprague-Dawley rats were operated upon to achieve a middle cerebral artery occlusion to cause transient focal cerebral ischemia, which were then randomly divided into the sham-operated control group and cerebral ischemia/reperfusion (I/R) groups receiving a 2 h occlusion. The treatment groups received daily intraperitoneal injections of high or low doses of TSA, for 7 or 15 days. NeuN immunostaining revealed neuronal loss following I/R, which was partially prevented with subsequent TSA dosing. Protein disulfide isomerase and adenosine triphosphatase (Na(+)/K(+)-ATPase) levels were all depressed by means of I/R. TSA treatment markedly reversed the depression of all indices examined. The intensity of microglial activation, as evidenced with CD11b staining, was increased by means of cerebral artery occlusion, but this was partially reversed with subsequent TSA treatment. TSA may affect neuroprotection by way of minimizing deficits in energy metabolism and reduction of the extent of cell death within affected regions.

The Interferon Consensus Sequence Binding Protein (Icsbp/Irf8) Is Required for Termination of Emergency Granulopoiesis.

Emergency granulopoiesis occurs in response to infectious or inflammatory challenge and is a component of the innate immune response. Some molecular events involved in initiating emergency granulopoiesis are known, but termination of this process is less well defined. In this study, we found that the interferon consensus sequence binding protein (Icsbp/Irf8) was required to terminate emergency granulopoiesis. Icsbp is an interferon regulatory transcription factor with leukemia suppressor activity. Expression of Icsbp is decreased in chronic myeloid leukemia, and Icsbp(-/-) mice exhibit progressive granulocytosis with evolution to blast crisis, similar to the course of human chronic myeloid leukemia. In this study, we found aberrantly sustained granulocyte production in Icsbp(-/-) mice after stimulation of an emergency granulopoiesis response. Icsbp represses transcription of the genes encoding Fas-associated phosphatase 1 (Fap1) and growth arrest-specific 2 (Gas2) and activates genes encoding Fanconi C and F. After stimulation of emergency granulopoiesis, we found increased and sustained expression of Fap1 and Gas2 in bone marrow myeloid progenitor cells from Icsbp(-/-) mice in comparison with the wild type. This was associated with resistance to Fas-induced apoptosis and increased ß-catenin activity in these cells. We also found that repeated episodes of emergency granulopoiesis accelerated progression to acute myeloid leukemia in Icsbp(-/-) mice. This was associated with impaired Fanconi C and F expression and increased sensitivity to DNA damage in bone marrow myeloid progenitors. Our results suggest that impaired Icsbp expression enhances leukemogenesis by deregulating processes that normally limit granulocyte expansion during the innate immune response.

HoxA10 Terminates Emergency Granulopoiesis by Increasing Expression of Triad1.

Expression of the E3 ubiquitin ligase Triad1 is greater in mature granulocytes than in myeloid progenitor cells. HoxA10 actives transcription of the gene encoding Triad1 (ARIH2) during myeloid differentiation, but the contribution of increased Triad1 expression to granulocyte production or function is unknown. Mice with bone marrow-specific disruption of the ARIH2 gene exhibit constitutive inflammation with tissue infiltration by granulocytes and B cells. In contrast, disruption of the HOXA10 gene in mice neither constitutively activates the innate immune response nor significantly alters steady-state granulopoiesis. This study explores the impact of HoxA10-induced Triad1 expression on emergency (stress) granulopoiesis. We found that mice with HOXA10 gene disruption exhibited an overwhelming and fatal emergency granulopoiesis response that was characterized by tissue infiltration with granulocytes, but reversed by re-expression of Triad1 in the bone marrow. We determined that HoxA9 repressed ARIH2 transcription in myeloid progenitor cells, antagonizing the effect of HoxA10 on Triad1 expression. Also, we found that differentiation-stage-specific ARIH2 transcription was regulated by the tyrosine phosphorylation states of HoxA9 and HoxA10. Our studies demonstrate a previously undescribed role for HoxA10 in terminating emergency granulopoiesis, suggesting an important contribution by Hox proteins to the innate immune response.

The leukemia-associated Mll-Ell oncoprotein induces fibroblast growth factor 2 (Fgf2)-dependent cytokine hypersensitivity in myeloid progenitor cells.

The subset of acute myeloid leukemias (AML) with chromosomal translocations involving the MLL gene have a poor prognosis (referred to as 11q23-AML). The MLL fusion proteins that are expressed in 11q23-AML facilitate transcription of a set of HOX genes, including HOXA9 and HOXA10. Because Hox proteins are transcription factors, this suggests the possibility that Hox target genes mediate the adverse effects of MLL fusion proteins in leukemia. Identifying such Hox target genes might provide insights to the pathogenesis and treatment of 11q23-AML. In the current study we found that Mll-Ell (an MLL fusion protein) induced transcriptional activation of the FGF2 gene in a HoxA9- and HoxA10-dependent manner. FGF2 encodes fibroblast growth factor 2 (also referred to as basic fibroblast growth factor). Fgf2 influences proliferation and survival of hematopoietic stem cells and myeloid progenitor cells, and increased Fgf2-expression has been described in AMLs. We determined that expression of Mll-Ell in myeloid progenitor cells resulted in autocrine production of Fgf2 and Fgf2-dependent cytokine hypersensitivity. Therefore, our results implicated increased Fgf2 expression in progenitor proliferation and expansion in 11q23-AML. Because small molecule inhibitors of Fgf-receptors are in human clinical trials, this suggested a potential therapeutic approach to this treatment refractory leukemia.

Fas-associated phosphatase 1 (Fap1) influences ßcatenin activity in myeloid progenitor cells expressing the Bcr-abl oncogene.

Increased ßcatenin activity correlates with leukemia stem cell expansion and disease progression in chronic myeloid leukemia (CML). We found previously that expression of the CML-related Bcr-abl oncoprotein in myeloid progenitor cells increases expression of Fas-associated phosphatase 1 (Fap1). This resulted in Fap1-dependent resistance to Fas-induced apoptosis in these cells. Fap1 also interacts with the adenomatous polyposis coli (Apc) protein, but the functional significance of this interaction is unknown. Apc participates in a complex that includes glycogen synthase kinase ß (Gsk3ß) and ßcatenin. Assembly of this complex results in phosphorylation of ßcatenin by Gsk3ß, which facilitates ßcatenin ubiquitination and degradation by the proteasome. In this study, we found increased association of Fap1 with the Apc complex in Bcr-abl(+) myeloid progenitor cells. We also found Fap1-dependent inactivation of Gsk3ß and consequent stabilization of ßcatenin in these cells. Consistent with this, Bcr-abl(+) cells exhibited a Fap1-dependent increase in ßcatenin activity. Our studies identified Fap1-dependent Gsk3ß inactivation as a molecular mechanism for increased ßcatenin activity in CML.

Fas-associated phosphatase 1 mediates Fas resistance in myeloid progenitor cells expressing the Bcr-abl oncogene.

The interferon consensus sequence binding protein (Icsbp) is a transcription factor that influences multiple aspects of myelopoiesis. Expression of Icsbp is decreased in the bone marrow of human subjects with chronic myeloid leukemia (CML), and studies in murine models suggest that Icsbp functions as an anti-oncogene for CML. We previously identified a set of Icsbp target genes that may contribute to this anti-oncogene effect. The set includes PTPN13, the gene encoding Fas-associated phosphatase 1 (Fap1, a Fas antagonist). We previously demonstrated that myeloid progenitor cells from Icsbp-knockout mice exhibit Fap1-dependent Fas resistance. In the present study, we determined that the Fas resistance of Bcr-abl+cells is Icsbp- and Fap1-dependent. We also found that treatment of Bcr-abl bone marrow cells with a Fap1-blocking peptide prevents in vitro selection of a tyrosine kinase inhibitor (TKI)-resistant population. Therefore, these results have implications for therapeutic targeting of the Fas-resistant leukemia stem cell population and addressing TKI resistance in CML.

ß-Catenin activates the HOXA10 and CDX4 genes in myeloid progenitor cells.

HoxA10 is a homeodomain transcription factor that is involved in maintenance of the myeloid progenitor population and implicated in myeloid leukemogenesis. Previously, we found that FGF2 and CDX4 are direct target genes of HoxA10 and that HOXA10 is a Cdx4 target gene. We also found that increased production of fibroblast growth factor 2 (Fgf2) by HoxA10-overexpressing myeloid progenitor cells results in activation of ß-catenin in an autocrine manner. In this study, we identify novel cis elements in the CDX4 and HOXA10 genes that are activated by ß-catenin in myeloid progenitor cells. We determine that ß-catenin interacts with these cis elements, identifying both CDX4 and HOXA10 as ß-catenin target genes in this context. We demonstrate that HoxA10-induced CDX4 transcription is influenced by Fgf2-dependent ß-catenin activation. Similarly, Cdx4-induced HOXA10 transcription is influenced by ß-catenin in an Fgf2-dependent manner. Increased expression of a set of Hox proteins, including HoxA10, is associated with poor prognosis in acute myeloid leukemia. Cdx4 contributes to leukemogenesis in Hox-overexpressing acute myeloid leukemia, and increased ß-catenin activity is also associated with poor prognosis. The current studies identify a molecular mechanisms through which increased expression of HoxA10 increases Cdx4 expression by direct CDX4 activation and by Fgf2-induced ß-catenin activity. This results in Cdx4-induced HoxA10-expression, creating a positive feedback mechanism.