AHI-1 interacts with BCR-ABL and modulates BCR-ABL transforming activity and imatinib response of CML stem/progenitor cells

Association of genetic risk and lifestyle with incident adult-onset asthma in the UK Biobank cohort

Background

Both genetic and lifestyle factors contribute to the development of asthma, but whether unfavourable lifestyle is associated with similar increases in risk of developing asthma among individuals with varying genetic risk levels remains unknown.

Methods

A healthy lifestyle score was constructed using body mass index, smoking status, physical activities and dietary pattern to further categorise into ideal, intermediate and poor groups. Genetic risk of asthma was also categorised as three groups based on the tertiles of polygenic risk score established using 212 reported and verified single-nucleotide polymorphisms of European ancestry in the UK Biobank study. We examined the risk of incident asthma related with each lifestyle level in each genetic risk group by Cox regression models.

Results

Finally, 327 124 participants without baseline asthma were included, and 157 320 (48.1%) were male. During follow-up, 6238 participants (1.9%) developed asthma. Compared to ideal lifestyle in a low genetic risk group, poor lifestyle was associated with a hazard ratio of up to 3.87 (95% CI, 2.98-5.02) for developing asthma in a high genetic risk group. There was interaction between genetic risk and lifestyle, and the population-attributable fraction of lifestyle and genetic risk were 30.2% and 30.0% respectively.

Conclusion

In this large contemporary population, lifestyle and genetic factors jointly play critical roles in the development of asthma, and the effect values of lifestyle on incident adult-onset asthma were greater than that of genetic risk. Our findings highlighted the necessity of a comprehensive intervention for the prevention of asthma despite the genetic risk.

GFI-1 overexpression promotes cell proliferation and apoptosis resistance in mycosis fungoides by repressing Bax and P21

Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma. The majority of patients with advanced stage MF are resistant to conventional chemotherapy and thus have a poor prognosis. The transcriptional repressor growth factor independence-1 (GFI-1) serves an important role in the development of T-cells. The results of the present study demonstrated that the expression of GFI-1 at different clinical stages of MF was significantly higher compared with benign inflammatory dermatoses, and there was a significant association with disease progression. Gene knockdown of GFI-1 results in the inhibition of Hut-78 cell proliferation and clone formation in vitro, cell cycle arrest and spontaneous apoptosis, upregulation of cell cycle-related P21, as well as the apoptosis-related proteins Bax and Caspase-3, and downregulation of CDK2. Using luciferase assays, and mutational analysis, it was demonstrated that GFI-1 directly regulated the transcription of P21. The results of the present study highlighted a potential molecular therapeutic approach for the treatment of advanced MF.

Identification of Tumor Microenvironment-Related Alternative Splicing Events to Predict the Prognosis of Endometrial Cancer

Background

Endometrial cancer (EC) is one of the most common female malignant tumors. The immunity is believed to be associated with EC patients’ survival, and growing studies have shown that aberrant alternative splicing (AS) might contribute to the progression of cancers.

Methods

We downloaded the clinical information and mRNA expression profiles of 542 tumor tissues and 23 normal tissues from The Cancer Genome Atlas (TCGA) database. ESTIMATE algorithm was carried out on each EC sample, and the OS-related different expressed AS (DEAS) events were identified by comparing the high and low stromal/immune scores groups. Next, we constructed a risk score model to predict the prognosis of EC patients. Finally, we used unsupervised cluster analysis to compare the relationship between prognosis and tumor immune microenvironment.

Results

The prognostic risk score model was constructed based on 16 OS-related DEAS events finally identified, and then we found that compared with high-risk group the OS in the low-risk group was notably better. Furthermore, according to the results of unsupervised cluster analysis, we found that the better the prognosis, the higher the patient’s ESTIMATE score and the higher the infiltration of immune cells.

Conclusions

We used bioinformatics to construct a gene signature to predict the prognosis of patients with EC. The gene signature was combined with tumor microenvironment (TME) and AS events, which allowed a deeper understanding of the immune status of EC patients, and also provided new insights for clinical patients with EC.

Computational and Biological Investigations on Abl1 Tyrosine Kinase: A Review

Abl1 tyrosine kinase is a validated target for the treatment of chronic myeloid leukemia. It is a form of cancer that is difficult to treat and much research is being done to identify new molecular entities and to tackle drug resistance issues. In recent years, drug resistance of Abl1 tyrosine kinase has become a major healthcare concern. Second and third-generation TKI reported better responses against the resistant forms; still they had no impact on long-term survival prolongation. New compounds derived from natural products and organic small molecule inhibitors can lay the foundation for better clinical therapies in the future. Computational methods, experimental and biological studies can help us understand the mechanism of drug resistance and identify novel molecule inhibitors. ADMET parameters analysis of reported drugs and novel small molecule inhibitors can also provide valuable insights. In this review, available therapies, point mutations, structure-activity relationship and ADMET parameters of reported series of Abl1 tyrosine kinase inhibitors and drugs are summarised. We summarise in detail recent computational and molecular biology studies that focus on designing drug molecules, investigation of natural product compounds and organic new chemical entities. Current ongoing research suggests that selective targeting of Abl1 tyrosine kinase at the molecular level to combat drug resistance in chronic myeloid leukemia is promising.

Differential SATB1 Expression Reveals Heterogeneity of Cutaneous T-Cell Lymphoma

SATB1 is an important T-cell specific chromatin organizer in cutaneous T-cell lymphoma, whereas its expression and function in mycosis fungoides (MF) remain ambiguous. Our study aimed to investigate the clinicopathological significance of SATB1 in a cohort of 170 patients with MF. SATB1 expression was heterogeneous among the patients with MF in each clinical stage. High SATB1 expression was associated with epidermal hyperplasia, eosinophil infiltration, less large-cell transformation, and favorable prognosis in MF cases. SATB1 and CD30 coexpression distinguished cutaneous CD30⁺ lymphoproliferative disorders from MF large-cell transformation. SATB1 silencing in MF lines showed that SATB1 upregulated the genes involved in eosinophil recruitment, including signal transducer and activator of transcription 3 and IL13, and downregulated the genes in cell-cycle progression, which may explain the inferior prognosis for low SATB1-expressing cases. Moreover, SATB1 was inversely correlated with PD-1 expression, indicating an exhausted status of SATB1-negative malignant T cells. SATB1 was positively correlated with toll-like receptors expression, suggesting innate immune activation in high SATB1-expressing MF cases. Therefore, variable SATB1 expression promotes heterogeneity in pathology and clinical outcome of patients with MF.

Genome-wide analysis highlights contribution of immune system pathways to the genetic architecture of asthma

Asthma is a chronic and genetically complex respiratory disease that affects over 300 million people worldwide. Here, we report a genome-wide analysis for asthma using data from the UK Biobank and the Trans-National Asthma Genetic Consortium. We identify 66 previously unknown asthma loci and demonstrate that the susceptibility alleles in these regions are, either individually or as a function of cumulative genetic burden, associated with risk to a greater extent in men than women. Bioinformatics analyses prioritize candidate causal genes at 52 loci, including CD52, and demonstrate that asthma-associated variants are enriched in regions of open chromatin in immune cells. Lastly, we show that a murine anti-CD52 antibody mimics the immune cell-depleting effects of a clinically used human anti-CD52 antibody and reduces allergen-induced airway hyperreactivity in mice. These results further elucidate the genetic architecture of asthma and provide important insight into the immunological and sex-specific relevance of asthma-associated risk variants.

Asthma is a common disease of the airways for which numerous genetic loci have been identified. Here, Han et al. carry out a genome-wide analysis for asthma to identify additional loci, report sex-stratified and genetic risk score analyses, and functionally follow-up one locus using a murine model of airway hyperreactivity.

Response and Resistance to BCR-ABL1-Targeted Therapies

Chronic myeloid leukemia (CML), caused by constitutively active BCR-ABL1 fusion tyrosine kinase, has served as a paradigm for successful application of molecularly targeted cancer therapy. The development of the tyrosine kinase inhibitor (TKI) imatinib allows patients with CML to experience near-normal life expectancy. Specific point mutations that decrease drug binding affinity can produce TKI resistance, and second- and third-generation TKIs largely mitigate this problem. Some patients develop TKI resistance without known resistance mutations, with significant heterogeneity in the underlying mechanism, but this is relatively uncommon, with the majority of patients with chronic phase CML achieving long-term disease control. In contrast, responses to TKI treatment are short lived in advanced phases of the disease or in BCR-ABL1-positive acute lymphoblastic leukemia, with relapse driven by both BCR-ABL1 kinase-dependent and -independent mechanisms. Additionally, the frontline CML treatment with second-generation TKIs produces deeper molecular responses, driving disease burden below the detection limit for a greater number of patients. For patients with deep molecular responses, up to half have been able to discontinue therapy. Current efforts are focused on identifying therapeutic strategies to drive deeper molecular responses, enabling more patients to attempt TKI discontinuation.

Comment on "PP2A inhibition sensitizes cancer stem cells to ABL tyrosine kinase inhibitors in BCR-ABL human leukemia"

LB100 does not sensitize CML stem cells to tyrosine kinase inhibitor-induced apoptosis.

Reduction of AHI1 in the serum of Taiwanese with probable Alzheimer's disease

OBJECTIVE

The development of blood-based biomarkers for early diagnosis and treatment of Alzheimer's disease (AD) is desirable. In AD model mouse brain and neuronal cells, Abelson helper integration site-1 (AHI1) protein is reduced. AHI1 facilitates intracellular amyloid precursor protein (APP) translocation to inhibit amyloidogenic pathology of AD, and thus may be an AD biomarker.

METHODS

This study was conducted among 32 AD patients and 54 healthy control (HC) subjects. AHI1-related protein levels from initially collected serum samples in each group were screened using Western blotting. The protein concentrations of AHI1 and amyloid-β (Aβ), peptide(s) derived from APP, from all serum samples were analyzed using ELISA.

RESULTS

In AD serum, AHI1 and a large truncated C-terminal APP fragment were significantly reduced. The average concentrations of serum AHI1 and Aβ in AD were significantly lower than those in HC. Notably, AHI1 concentration in HC serum was decreased in an age-dependent manner, while it was consistently low in AD serum and had no correlation with Aβ or mini-mental state examination score. The receiver operating characteristic analysis on all subjects demonstrated an area under curve (AUC) value of 0.7 for AHI1 on AD diagnosis, while the AUC increased to 0.82 on the subjects younger than 77 years old, suggesting a good diagnostic performance of serum AHI1 for AD especially at relatively young age.

CONCLUSION

An early event of AHI1 reduction in the body of AD patients was observed. Serum AHI1 may be valuable for early diagnosis of AD.

Cholesterol grafted cationic lipopolymers: Potential siRNA carriers for selective chronic myeloid leukemia therapy

Synthetic siRNA technology has emerged as a promising approach for molecular therapy of cancer but, despite its potential for post-transcriptional gene silencing, there is an urgent need to develop efficient delivery systems particularly for difficult-to-transfect, anchorage-independent cells. In this study, we designed highly hydrophobic cationic lipopolymers by grafting cholesterol (Chol) onto low-molecular weight (0.6, 1.2, and 2.0 kDa) polyethylenimines (PEIs) to enable specific siRNA therapy to chronic myeloid leukemia (CML) cells. The siRNA binding by PEI-Chol led to nano-sized (100-200 nm diameter) polyplexes with enhanced ζ-potential (+20 to +35 mV) and ability to protect the loaded siRNA completely in fresh serum. The siRNA delivery to CML (K562) cells was proportional to degree of substitution and, unexpectedly, inversely proportional to molecular size of the polymeric backbone. Chol grafting with as little as ~1.0 Chol/PEI on 0.6 and 1.2 kDa PEIs enabled silencing of the reporter Green Fluorescent Protein gene as well as the endogenous BCR-Abl oncogene in K562 cells. The PEI-Chol mediated delivery of siRNAs specific for BCR-Abl and KSP genes significantly arrested the growth the cells which was significantly reflected in colony formation potency of K562 cells. BCR-Able siRNA mediated therapeutic efficacy was also observed in significantly increased caspase activity and apoptosis of K562 cells. Thus, Chol-grafted low-molecular weight PEIs appear to be unique siRNA carriers to realize the molecular therapy in CML cells.

siRNA-mediated BCR-ABL silencing in primary chronic myeloid leukemia cells using lipopolymers

Despite development of effective tyrosine kinase inhibitors for treatment of chronic myeloid leukemia (CML), some patients do not effectively respond to the therapy and can display resistance in response to the drug therapy. To develop an alternative approach to CML therapy, we are exploring siRNA mediated silencing of the primary CML oncogene, BCR-ABL, by using non-viral (polymeric) delivery systems. In this study, a group of lipopolymers derived from low molecular PEIs substituted with linoleic acid (LA), α-linolenic acid (αLA) and cholesterol (Chol) was investigated for the first time for siRNA delivery to CML primary samples. The delivery efficiency in primary cells was equivalent to CML K562 cell line, and the lipopolymers gave effective internalization of siRNA depending on the nature of lipid substituent. The PEI-αLA (2.5 αLA/PEI), PEI-Chol (2.2 Chol/PEI), and PEI-LA (2.6 LA/PEI) lipopolymers used as BCR-ABL siRNA carriers (at 60 nM siRNA) reduced the BCR-ABL mRNA expression by 17% to 45%, and inhibited the formation of colonies by 24% to 41% in comparison with control siRNA in mononuclear cells. BCR-ABL siRNA treatment reduced the BCR-ABL mRNA expression by 50% in one of two CD34+ samples tested, and combination of BCR-ABL siRNA with imatinib (IM) treatment decreased the colony formation by 65% in one of two samples evaluated. The fact that no single polymer was universally effective in all patient samples may suggest patient-to-patient variability in terms of therapeutic responses to siRNA therapy. These results showed that a low dose of BCR-ABL siRNA could be used with lipopolymers to reduce BCR-ABL mRNA expression, CML cell survival and colony formation. This proof of principle study in CML primary cells can be applied to silencing of other therapeutic targets besides BCR-ABL and a study with larger patient samples is warranted for better identification of effective siRNA carriers.

BCR-Abl Silencing by siRNA: A Potent Approach to Sensitize Chronic Myeloid Leukemia Cells to Tyrosine Kinase Inhibitor Therapy

Nonviral gene therapy with specific short interfering RNAs (siRNAs) against BCR-Abl can be an alternative and/or supportive therapy of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKIs), given the often observed resistance to TKIs in clinical setting. In this study, we explored the feasibility of BCR-Abl siRNA therapy in CML K562 cells in vitro by employing a cationic polymer derived from cholesterol (Chol) grafted low-molecular weight polyethyleneimine (PEI). The first generation TKI imatinib upregulated the expression of BCR-Abl in K562 cells as expected. Delivery of BCR-Abl siRNA in both drug-sensitive and drug-resistant K562 cells significantly downregulated the mRNA levels in both cell types. Similarly, the BCR-Abl siRNA treatment arrested the growth of both drug-sensitive and drug-resistant K562 cells with no obvious differences despite a large difference in drug responsiveness. The BCR-Abl gene silencing in combination with TKI treatments exhibited significant synergism in drug-resistant K562 cells in generating substantial antileukemic activity, where the TKIs on their own were not effective. The effect of BCR-Abl siRNA and TKIs on non-CML cells (Jurkat and primary fibroblast) was negligible, indicating the specificity of the proposed therapy. This strategy can significantly overcome TKI resistance in CML cells, suggesting a feasible and effective treatment model for CML patients suffering from clinical resistances.

Primary cilia proteins: ciliary and extraciliary sites and functions

Primary cilia are immotile organelles known for their roles in development and cell signaling. Defects in primary cilia result in a range of disorders named ciliopathies. Because this organelle can be found singularly on almost all cell types, its importance extends to most organ systems. As such, elucidating the importance of the primary cilium has attracted researchers from all biological disciplines. As the primary cilia field expands, caution is warranted in attributing biological defects solely to the function of this organelle, since many of these "ciliary" proteins are found at other sites in cells and likely have non-ciliary functions. Indeed, many, if not all, cilia proteins have locations and functions outside the primary cilium. Extraciliary functions are known to include cell cycle regulation, cytoskeletal regulation, and trafficking. Cilia proteins have been observed in the nucleus, at the Golgi apparatus, and even in immune synapses of T cells (interestingly, a non-ciliated cell). Given the abundance of extraciliary sites and functions, it can be difficult to definitively attribute an observed phenotype solely to defective cilia rather than to some defective extraciliary function or a combination of both. Thus, extraciliary sites and functions of cilia proteins need to be considered, as well as experimentally determined. Through such consideration, we will understand the true role of the primary cilium in disease as compared to other cellular processes' influences in mediating disease (or through a combination of both). Here, we review a compilation of known extraciliary sites and functions of "cilia" proteins as a means to demonstrate the potential non-ciliary roles for these proteins.

PP2A inhibition sensitizes cancer stem cells to ABL tyrosine kinase inhibitors in BCR-ABL + human leukemia

PP2A inhibitors and BCR-ABL inhibitors synergize to kill drug-insensitive leukemia cells.

MS AHI1 genetic risk promotes IFNγ+ CD4+ T cells

Objective

To study the influence of the Abelson helper integration site 1 (AHI1) locus associated with MS susceptibility on CD4⁺ T cell function.

Methods

We characterized the chromatin state of T cells in the MS-associated AHI1 linkage disequilibrium (LD) block. The expression and the role of the AHI1 variant were examined in T cells from genotyped healthy subjects who were recruited from the PhenoGenetic Project, and the function of AHI1 was explored using T cells from Ahi1 knockout mice.

Results

Chromatin state analysis reveals that the LD block containing rs4896153, which is robustly associated with MS susceptibility (odds ratio 1.15, p = 1.65 × 10^-13), overlaps with strong enhancer regions that are present in human naive and memory CD4⁺ T cells. Relative to the rs4896153^A protective allele, the rs4896153^T susceptibility allele is associated with decreased AHI1 mRNA expression, specifically in naive CD4⁺ T cells (p = 1.73 × 10^-74, n = 213), and we replicate this effect in an independent set of subjects (p = 2.5 × 10^-9, n = 32). Functional studies then showed that the rs4896153^T risk variant and the subsequent decreased AHI1 expression were associated with reduced CD4⁺ T cell proliferation and a specific differentiation into interferon gamma (IFNγ)-positive T cells when compared with the protective rs4896153^A allele. This T cell phenotype was also observed in murine CD4⁺ T cells with genetic deletion of Ahi1.

Conclusions

Our findings suggest that the effect of the AHI1 genetic risk for MS is mediated, in part, by enhancing the development of proinflammatory IFNγ⁺ T cells that have previously been implicated in MS and its mouse models.

Cellular and Molecular Networks in Chronic Myeloid Leukemia: The Leukemic Stem, Progenitor and Stromal Cell Interplay

The use of imatinib, second and third generation ABL tyrosine kinase inhibitors (TKI) (i.e. dasatinib, nilotinib, bosutinib and ponatinib) made CML a clinically manageable and, in a small percentage of cases, a cured disease. TKI therapy also turned CML blastic transformation into a rare event; however, disease progression still occurs in those patients who are refractory, not compliant with TKI therapy or develop resistance to multiple TKIs. In the past few years, it became clear that the BCRABL1 oncogene does not operate alone to drive disease emergence, maintenance and progression. Indeed, it seems that bone marrow (BM) microenvironment-generated signals and cell autonomous BCRABL1 kinase-independent genetic and epigenetic alterations all contribute to: i. persistence of a quiescent leukemic stem cell (LSC) reservoir, ii. innate or acquired resistance to TKIs, and iii. progression into the fatal blast crisis stage. Herein, we review the intricate leukemic network in which aberrant, but finely tuned, survival, mitogenic and self-renewal signals are generated by leukemic progenitors, stromal cells, immune cells and metabolic microenvironmental conditions (e.g. hypoxia) to promote LSC maintenance and blastic transformation.

A novel AHI-1-BCR-ABL-DNM2 complex regulates leukemic properties of primitive CML cells through enhanced cellular endocytosis and ROS-mediated autophagy

Tyrosine kinase inhibitor (TKI) therapies induce clinical remission with remarkable effects on chronic myeloid leukemia (CML). However, very few TKIs completely eradicate the leukemic clone and persistence of leukemic stem cells (LSCs) remains challenging, warranting new, distinct targets for improved treatments. We demonstrated that the scaffold protein AHI-1 is highly deregulated in LSCs and interacts with multiple proteins, including Dynamin-2 (DNM2), to mediate TKI-resistance of LSCs. We have now demonstrated that the SH3 domain of AHI-1 and the proline rich domain of DNM2 are mainly responsible for this interaction. DNM2 expression was significantly increased in CML stem/progenitor cells; knockdown of DNM2 greatly impaired their survival and sensitized them to TKI treatments. Importantly, a new AHI-1-BCR-ABL-DNM2 protein complex was uncovered, which regulates leukemic properties of these cells through a unique mechanism of cellular endocytosis and ROS-mediated autophagy. Thus, targeting this complex may facilitate eradication of LSCs for curative therapies.

Common variants at PVT1, ATG13-AMBRA1, AHI1 and CLEC16A are associated with selective IgA deficiency

Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Europeans. Our genome-wide association study (GWAS) meta-analysis of 1,635 patients with IgAD and 4,852 controls identified four new significant (P < 5 × 10-8) loci and association with a rare IFIH1 variant (p.Ile923Val). Peak new variants (PVT1, P = 4.3 × 10-11; ATG13-AMBRA1, P = 6.7 × 10-10; AHI1, P = 8.4 × 10-10; CLEC16A, P = 1.4 × 10-9) overlapped with autoimmune markers (3/4) and correlated with 21 putative regulatory variants, including expression quantitative trait loci (eQTLs) for AHI1 and DEXI and DNase hypersensitivity sites in FOXP3+ regulatory T cells. Pathway analysis of the meta-analysis results showed striking association with the KEGG pathway for IgA production (pathway P < 0.0001), with 22 of the 30 annotated pathway genes containing at least one variant with P ≤ 0.05 in the IgAD meta-analysis. These data suggest that a complex network of genetic effects, including genes known to influence the biology of IgA production, contributes to IgAD.

New Mouse Models to Investigate the Efficacy of Drug Combinations in Human Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) comprises a simple and effective paradigm for generating new insights into the cellular origin, pathogenesis, and treatment of many types of human cancer. In particular, mouse models of CML have greatly facilitated the understanding of the underlying molecular mechanisms and pathogenesis of this disease and have led to the identification of new drug targets that in some cases offer the possibility of functional cure. There are currently three established CML mouse models: the BCR-ABL transgenic model, the BCR-ABL retroviral transduction/transplantation model, and the xenotransplant immunodeficient model. Each has its own unique advantages and disadvantages. Depending on the question of interest, some models may be more appropriate than others. In this chapter, we describe a newly developed xenotransplant mouse model to determine the efficacy of novel therapeutic agents, either alone or in combination. The model facilitates the evaluation of the frequency of leukemic stem cells with long-term leukemia-initiating activity, a critical subcellular population that causes disease relapse and progression, through the utilization of primary CD34(+) CML stem/progenitor cells obtained from CML patients at diagnosis and prior to drug treatment. We have also investigated the effectiveness of new combination treatment strategies designed to prevent the development of leukemia in vivo using BCR-ABL (+) blast crisis cells as a model system. These types of in vivo studies are important for the prediction of individual patient responses to drug therapy, and have the potential to facilitate the design of personalized combination therapy strategies.

Cancer stem cells: a challenging paradigm for designing targeted drug therapies

Despite earlier controversies about their role and existence within tumors, cancer stem cells (CSCs) are now emerging as a plausible target for new drug discovery. Research and development (R&D) efforts are being directed against key gene(s) driving initiation, growth, and metastatic pathways in CSCs and the tumor microenvironment (TME). However, the niche signals that enable these pluripotent CSCs to evade radio- and chemotherapy, and to travel to secondary tissues remain enigmatic. Small-molecule drugs, biologics, miRNA, RNA interference (RNAi), and vaccines, among others, are under active investigation. Here, we examine the feasibility of leveraging current knowhow of the molecular biology of CSCs and their cellular milieu to design futuristic, targeted drugs with potentially lower toxicity that can override the multiple drug-resistance issues currently observed with existing therapeutics.

Selective JAK2/ABL dual inhibition therapy effectively eliminates TKI-insensitive CML stem/progenitor cells

Imatinib Mesylate (IM) and other tyrosine kinase inhibitor (TKI) therapies have had a major impact on the treatment of chronic myeloid leukemia (CML). However, TKI monotherapy is not curative, with relapse and persistence of leukemic stem cells (LSCs) remaining a challenge. We have recently identified an AHI-1-BCR-ABL-JAK2 protein complex that contributes to the transforming activity of BCR-ABL and IM-resistance in CML stem/progenitor cells. JAK2 thus emerges as an attractive target for improved therapies, but off-target effects of newly developed JAK2 inhibitors on normal hematopoietic cells remain a concern. We have examined the biological effects of a highly selective, orally bioavailable JAK2 inhibitor, BMS-911543, in combination with TKIs on CD34⁺ treatment-naïve IM-nonresponder cells. Combination therapy reduces JAK2/STAT5 and CRKL activities, induces apoptosis, inhibits proliferation and colony growth, and eliminates CML LSCs in vitro. Importantly, BMS-911543 selectively targets CML stem/progenitor cells while sparing healthy stem/progenitor cells. Oral BMS-911543 combined with the potent TKI dasatinib more effectively eliminates infiltrated leukemic cells in hematopoietic tissues than TKI monotherapy and enhances survival of leukemic mice. Dual targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may consequently lead to more effective disease eradication, especially in patients at high risk of TKI resistance and disease progression.

Huntingtin-associated protein 1 interacts with breakpoint cluster region protein to regulate neuronal differentiation

Alterations in microtubule-dependent trafficking and certain signaling pathways in neuronal cells represent critical pathogenesis in neurodegenerative diseases. Huntingtin (Htt)-associated protein-1 (Hap1) is a brain-enriched protein and plays a key role in the trafficking of neuronal surviving and differentiating cargos. Lack of Hap1 reduces signaling through tropomyosin-related kinases including extracellular signal regulated kinase (ERK), resulting in inhibition of neurite outgrowth, hypothalamic dysfunction and postnatal lethality in mice. To examine how Hap1 is involved in microtubule-dependent trafficking and neuronal differentiation, we performed a proteomic analysis using taxol-precipitated microtubules from Hap1-null and wild-type mouse brains. Breakpoint cluster region protein (Bcr), a Rho GTPase regulator, was identified as a Hap1-interacting partner. Bcr was co-immunoprecipitated with Hap1 from transfected neuro-2a cells and co-localized with Hap1A isoform more in the differentiated than in the nondifferentiated cells. The Bcr downstream effectors, namely ERK and p38, were significantly less activated in Hap1-null than in wild-type mouse hypothalamus. In conclusion, Hap1 interacts with Bcr on microtubules to regulate neuronal differentiation.

The cancer stem cell hypothesis: a guide to potential molecular targets

Common cancer theories hold that tumor is an uncontrolled somatic cell proliferation caused by the progressive addition of random mutations in critical genes that control cell growth. Nevertheless, various contradictions related to the mutation theory have been reported previously. These events may be elucidated by the persistence of residual tumor cells, called Cancer Stem Cells (CSCs) responsible for tumorigenesis, tumor maintenance, tumor spread, and tumor relapse. Herein, we summarize the current understanding of CSCs, with a focus on the possibility to identify specific markers of CSCs, and discuss the clinical application of targeting CSCs for cancer treatment.

The core autophagy protein ATG4B is a potential biomarker and therapeutic target in CML stem/progenitor cells

Previous studies demonstrated that imatinib mesylate (IM) induces autophagy in chronic myeloid leukemia (CML) and that this process is critical to cell survival upon therapy. However, it is not known if the autophagic process differs at basal levels between CML patients and healthy individuals and if pretreatment CML cells harbor unique autophagy characteristics that could predict patients' clinical outcomes. We now demonstrate that several key autophagy genes are differentially expressed in CD34(+) hematopoietic stem/progenitor cells, with the highest transcript levels detected for ATG4B, and that the transcript and protein expression levels of ATG4 family members, ATG5 and BECLIN-1 are significantly increased in CD34(+) cells from chronic-phase CML patients (P < .05). Importantly, ATG4B is differentially expressed in pretreatment CML stem/progenitor cells from subsequent IM responders vs IM nonresponders (P < .05). Knockdown of ATG4B suppresses autophagy, impairs the survival of CML stem/progenitor cells and sensitizes them to IM treatment. Moreover, deregulated expression of ATG4B in CD34(+) CML cells inversely correlates with transcript levels of miR-34a, and ATG4B is shown to be a direct target of miR-34a. This study identifies ATG4B as a potential biomarker for predicting therapeutic response in treatment-naïve CML stem/progenitor cells and uncovers ATG4B as a possible drug target in these cells.

SATB1 overexpression promotes malignant T-cell proliferation in cutaneous CD30+ lymphoproliferative disease by repressing p21

Cutaneous CD30(+) lymphoproliferative disease (CD30(+)LPD), characterized by the presence of CD30(+) anaplastic large T cells, comprises the second most common group of cutaneous T-cell lymphoma (CTCL). However, little is known about the pathobiology of the CD30(+) lymphoma cells, as well as the mechanisms of disease progression. Here we report that Special AT-rich region binding protein 1 (SATB1), a thymocyte specific chromatin organizer, is over-expressed in CD30(+) lymphoma cells in most CD30(+)LPDs, and its expression is upregulated during disease progression. Our findings show that SATB1 silencing in CD30(+)LPD cells leads to G1 cell cycle arrest mediated by p21 activation. Using chromatin immunoprecipitation, luciferase assays, and mutational analysis, we demonstrate that SATB1 directly regulates the transcription of p21 in a p53-independent manner. Moreover, DNA demethylation on a specific CpG-rich region of the SATB1 promoter is associated with the upregulation of SATB1 during disease progression. These experiments define a novel SATB1-p21 pathway in malignant CD30(+) T lymphocytes, which provides novel molecular insights into the pathogenesis of CD30(+)LPDs and possibly leads to new therapies.

JAK of all trades: JAK2-STAT5 as novel therapeutic targets in BCR-ABL1+ chronic myeloid leukemia

The transcription factor signal transducers and activators of transcription 5 (STAT5) has an important and unique role in Breakpoint Cluster Region - Abelson 1 (BCR-ABL1)-driven neoplasias. STAT5 is an essential component in the signaling network that maintains the survival and growth of chronic myeloid leukemia (CML) cells. In contrast, the function of the prototypical upstream kinase of STAT5, the Janus kinase JAK2, in CML is still under debate. Although there is widespread agreement that JAK2 is part of the signaling network downstream of BCR-ABL1, it is unclear whether and under what circumstances JAK2 inhibitors may be beneficial for CML patients. Recent studies in murine models have cast doubt on the importance of JAK2 in CML maintenance. Nevertheless, JAK2 has been proposed to have a central role in the cytokine signaling machinery that allows the survival of CML stem cells in the presence of BCR-ABL1 tyrosine kinase inhibitors. In this review, we summarize the current debate and provide an overview of the arguments on both sides of the fence. We present recent evidence showing that CML stem cells do not depend on BCR-ABL1 kinase activity but require the continuous support of the hematopoietic niche and its distinct cytokine environment and suggest that it has the potential to resolve the dispute.

Targeting primitive chronic myeloid leukemia cells by effective inhibition of a new AHI-1-BCR-ABL-JAK2 complex

BACKGROUND

Imatinib mesylate (IM) induces clinical remission of chronic myeloid leukemia (CML). The Abelson helper integration site 1 (AHI-1) oncoprotein interacts with BCR-ABL and Janus kinase 2 (JAK2) to mediate IM response of primitive CML cells, but the effect of the interaction complex on the response to ABL and JAK2 inhibitors is unknown.

METHODS

The AHI-1-BCR-ABL-JAK2 interaction complex was analyzed by mutational analysis and coimmunoprecipitation. Roles of the complex in regulation of response or resistance to ABL and JAK2 inhibitors were investigated in BCR-ABL (+) cells and primary CML stem/progenitor cells and in immunodeficient NSG mice. All statistical tests were two-sided.

RESULTS

The WD40-repeat domain of AHI-1 interacts with BCR-ABL, whereas the N-terminal region interacts with JAK2; loss of these interactions statistically significantly increased the IM sensitivity of CML cells. Disrupting this complex with a combination of IM and an orally bioavailable selective JAK2 inhibitor (TG101209 [TG]) statistically significantly induced death of AHI-1-overexpressing and IM-resistant cells in vitro and enhanced survival of leukemic mice, compared with single agents (combination vs TG alone: 63 vs 53 days, ratio = 0.84, 95% confidence interval [CI] = 0.6 to 1.1, P = .004; vs IM: 57 days, ratio = 0.9, 95% CI = 0.61 to 1.2, P = .003). Combination treatment also statistically significantly enhanced apoptosis of CD34(+) leukemic stem/progenitor cells and eliminated their long-term leukemia-initiating activity in NSG mice. Importantly, this approach was effective against treatment-naive CML stem cells from patients who subsequently proved to be resistant to IM therapy.

CONCLUSIONS

Simultaneously targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may improve outcomes in patients destined to develop IM resistance.

A novel lentivirus for quantitative assessment of gene knockdown in stem cell differentiation

Loss of gene function is a valuable tool for screening genes in cellular processes including stem cell differentiation differentiation. However, the criteria for evaluating gene knockdown are usually based on end-point analysis and real-time, dynamic information is lacking. To overcome these limitations, we engineered a shRNA encoding LentiViral Dual Promoter vector (shLVDP) that enabled real-time monitoring of mesenchymal stem (MSC) differentiation and simultaneous gene knockdown. In this vector, the activity of the alpha-smooth muscle actin (αSMA) promoter was measured by the expression of a destabilized green fluorescent protein, and was used as an indicator of myogenic differentiation; constitutive expression of discosoma red fluorescent protein was used to measure transduction efficiency and to normalize αSMA promoter activity; and shRNA was encoded by a doxycycline (Dox)-regulatable H1 promoter. Importantly, the normalized promoter activity was independent of lentivirus titer allowing quantitative assessment of gene knockdown. Using this vector, we evaluated 11 genes in the TGF-β1 or Rho signaling pathway on SMC maturation and on MSC differentiation along the myogenic lineage. As expected, knockdown of genes such as Smad2/3 or RhoA inhibited myogenic differentiation, while knocking down the myogenic differentiation inhibitor, Klf4, increased αSMA promoter activity significantly. Notably, some genes for example, Smad7 or KLF4 showed differential regulation of myogenic differentiation in MSC from different anatomic locations such as bone marrow and hair follicles. Finally, Dox-regulatable shRNA expression enabled temporal control of gene knockdown and provided dynamic information on the effect of different genes on myogenic phenotype. Our data suggests that shLVDP may be ideal for development of lentiviral microarrays to decipher gene regulatory networks of complex biological processes such as stem cell differentiation or reprogramming.

Molecular and structural characterization of the SH3 domain of AHI-1 in regulation of cellular resistance of BCR-ABL(+) chronic myeloid leukemia cells to tyrosine kinase inhibitors

ABL tyrosine kinase inhibitor (TKI) therapy induces clinical remission in chronic myeloid leukemia (CML) patients but early relapses and later emergence of TKI-resistant disease remain problematic. We recently demonstrated that the AHI-1 oncogene physically interacts with BCR-ABL and JAK2 and mediates cellular resistance to TKI in CML stem/progenitor cells. We now show that deletion of the SH3 domain of AHI-1 significantly enhances apoptotic response of BCR-ABL(+) cells to TKIs compared to cells expressing full-length AHI-1. We have also discovered a novel interaction between AHI-1 and Dynamin-2, a GTPase, through the AHI-1 SH3 domain. The crystal structure of the AHI-1 SH3 domain at 1.53-Å resolution reveals that it adopts canonical SH3 folding, with the exception of an unusual C-terminal α helix. PD1R peptide, known to interact with the PI3K SH3 domain, was used to model the binding pattern between the AHI-1 SH3 domain and its ligands. These studies showed that an "Arg-Arg-Trp" stack may form within the binding interface, providing a potential target site for designing specific drugs. The crystal structure of the AHI-1 SH3 domain thus provides a valuable tool for identification of key interaction sites in regulation of drug resistance and for the development of small molecule inhibitors for CML.

The Escherichia coli adherence factor plasmid of enteropathogenic Escherichia coli causes a global decrease in ubiquitylated host cell proteins by decreasing ubiquitin E1 enzyme expression through host aspartyl proteases

Ubiquitylation is a widespread post-translational global regulatory system that is essential for the proper functioning of various cellular events. Recent studies have shown that certain types of Escherichia coli can exploit specific aspects of the ubiquitylation system to influence downstream targets. Despite these findings, examination of the effects pathogenic E. coli have on the overall host ubiquitylation system remain unexplored. To study the impact that pathogenic E. coli have on the ubiquitylation levels of host proteins during infections, we analyzed the entire ubiquitylation system during enteropathogenic E. coli infections of cultured cells. We found that these microbes caused a dramatic decrease in ubiquitylated host proteins during these infections. This occurred with a concomitant reduction in the expression of essential E1 activating enzymes in the host, which are integral for the initiation of the ubiquitylation cascade. Control of host E1 enzyme levels was dependent on the E. coli adherence factor plasmid which acted on host aspartyl proteases within enteropathogenic E. coli. Hijacking of the ubiquitylation system did not require the plasmid-encoded regulator or bundle forming pilus expression, as enteropathogenic E. coli mutated in those factors did not revert the ubiquitylation of host proteins or the abundance of E1 enzyme proteins to uninfected levels. Our work shows that E. coli have developed strategies to usurp post-translational systems by targeting crucial enzymes. The ability of enteropathogenic E. coli to inactivate host protein ubiquitylation could enable more efficient effector protein functionality, providing increased bacterial control of host cells during enteropathogenic E. coli pathogenesis.

AHI-1: a novel signaling protein and potential therapeutic target in human leukemia and brain disorders

Progress in the understanding of the molecular and cellular mechanisms of human cancer, including human leukemia and lymphomas, has been spurred by cloning of fusion genes created by chromosomal translocations or by retroviral insertional mutagenesis; a number of oncogenes and tumor suppressors involved in development of a number of malignancies have been identified in this manner. The BCR-ABL fusion gene, originating in a multipotent hematopoietic stem cell, is the molecular signature of chronic myeloid leukemia (CML). Discovery of this fusion gene has led to the development of one of the first successful targeted molecular therapies for cancer (Imatinib). It illustrates the advances that can result from an understanding of the molecular basis of disease. However, there still remain many as yet unidentified mutations that may influence the initiation or progression of human diseases. Thus, identification and characterization of the mechanism of action of genes that contribute to human diseases is an important and opportune area of current research. One promising candidate as a potential therapeutic target is Abelson helper integration site-1(Ahi-1/AHI-1) that was identified by retroviral insertional mutagenesis in murine models of leukemia/lymphomas and is highly elevated in certain human lymphoma and leukemia stem/progenitor cells. It encodes a unique protein with a SH3 domain, multiple SH3 binding sites and a WD40-repeat domain, suggesting that the normal protein has novel signaling activities. A new AHI-1-BCR-ABL-JAK2 interaction complex has recently been identified and this complex regulates transforming activities and drug resistance in CML stem/progenitor cells. Importantly, AHI-1 has recently been identified as a susceptibility gene involved in a number of brain disorders, including Joubert syndrome. Therefore, understanding molecular functions of the AHI-1 gene could lead to important and novel insights into disease processes involved in specific types of diseases. Ultimately, this knowledge will set the stage for translation into new and more effective diagnostic and treatment strategies.

An exciting time to launch the World Journal of Hematology

This first issue of the World Journal of Hematology (WJH) marks the birth of a new member of the World Series Journal family and comes at one of the most exciting times in stem cell biology and translational medicine. The pace of discovery in the field of hematology has accelerated signeificantly in recent years, due to important scientific discoveries and new technologies for purification of hematopoietic stem cells and identification of specific stem cell biomarkers; whole genome sequencing using next-generation sequencing technology; and development of molecularly-targeted therapies, leading to the translation of highly promising science into advanced diagnosis and proven targeted therapies for hematopoietic disorders. The WJH is an open-access, peer-reviewed journal, which is officially published on June 6, 2012. The WJH Editorial Board consists of 102 experts in hematology from 26 countries. There is clearly a niche for this new journal, which provides access to all articles without boundaries to all internet users throughout the world. The WJH aims to provide rapid access to high impact publications in fundamental and clinical hematology, with multidisciplinary coverage, through an established system that is targeted at dissemination to the scientific community via online open-access.

Chronic myeloid leukemia stem cells in the era of targeted therapies: resistance, persistence and long-term dormancy

Targeted therapies of chronic myeloid leukemia (CML) using tyrosine kinase inhibitors (TKI) have profoundly changed the natural history of the disease with a major impact on survival. Molecular monitoring with BCR-ABL quantification shows that a status of undetectable molecular residual disease (UMRD) is obtained in a significant minority of patients. However, it remains unclear whether these patients are definitively cured of their leukemia. Imatinib mesylate withdrawal trials have demonstrated the rapid appearance of the malignant clone in the majority of the patients whereas some patients remain in a state of UMRD. It has clearly been demonstrated that the most primitive stem cells are refractory to all TKIs used in clinical practice. In addition, long-term dormancy is one of the most fundamental characteristics of hematopoietic stem cells. In this context, we have recently undertaken a systematic analysis of the bone marrow stem cell compartment in several patients in durable UMRD. We have demonstrated the long-term persistence of a considerable amount of BCR-ABL-expressing stem cells, even in the absence of relapse. The phenomenon of long-term leukemic stem cell dormancy is of major importance in CML and one of the key questions in cancer biology in general. We discuss, here, the potential mechanisms, including intrinsic and microenvironmental factors, that control the response of leukemic stem cells (LSCs) to targeted therapies and potential novel strategies currently in progress with a curative intent. Moreover, we propose a molecular evaluation of the residual LSC compartment in selected patients in order to develop rational TKI-cessation strategies in CML.

Assembling defenses against therapy-resistant leukemic stem cells: Bcl6 joins the ranks

Bcl6 is added to a growing list of signaling pathways and molecules that influence resistance of leukemic stem cells to targeted therapy.

The resistance of leukemic stem cells in response to targeted therapies such as tyrosine kinase inhibitors (TKIs) relies on the cooperative activity of multiple signaling pathways and molecules, including TGFβ, AKT, and FOXO transcription factors (TFs). B cell lymphoma 6 (BCL6) is a transcriptional repressor whose translocation or mutation is associated with diffuse large BCL. New data now show that BCL6 is critical for the maintenance of leukemias driven by the BCR-ABL translocation (Philadelphia chromosome), suggesting that BCL6 is a novel, targetable member of the complex signaling pathways critical for leukemic stem cell survival.

AHI1 gene expression levels and BCR-ABL1 T315I mutations in chronic myeloid leukemia patients

With the availability of molecular monitoring of BCR-ABL1 and the use of tyrosine kinase inhibitors, treatment in chronic myeloid leukemia (CML) is now molecularly focused. Eighty-three samples taken at different time points from 38 CML patients; were subjected to T315I mutation analysis and gene expression analysis of AHI1; a novel gene that is thought to have a role in both BCR-ABL1 mediated leukemic transformation and response to tyrosine kinase inhibitors. Only one patient (2.63%) harboured the T315I mutation. While no significant difference in AHI1 expression was observed between newly diagnosed CML samples and non-CML controls; CML samples under imatinib therapy had levels significantly higher than both newly diagnosed samples and controls. In the first 6 months of imatinib therapy, AHI1 expression was found to increase and then gradually decrease. There was no significant difference between imatinib responders and non-responders, while dasatinib caused significantly lower AHI1 levels. It is proposed that the change in AHI1 expression during CML therapy might be under the control of mechanisms independent from BCR-ABL1. AHI1 mediated signalling could be better understood by analyzing AHI1 gene expression levels in a greater number of patients and concurrently investigating JAK/STAT and Src family kinases pathways.

Genetic profile of adenoid cystic carcinomas (ACC) with high-grade transformation versus solid type

BACKGROUND

ACC can occasionally undergo dedifferentiation also referred to as high-grade transformation (ACC-HGT). However, ACC-HGT can also undergo transformation to adenocarcinomas which are not poorly differentiated. ACC-HGT is generally considered to be an aggressive variant of ACC, even more than solid ACC. This study was aimed to describe the genetic changes of ACC-HGT in relation to clinico-pathological features, and to compare results to solid ACC.

METHODS

Genome wide DNA copy number changes were analyzed by microarray CGH in ACC-HGT, four with transformation into moderately differentiated adenocarcinoma (MDA) and two into poorly differentiated carcinoma (PDC), and five solid ACC. In addition, Ki67 index and p53 immunopositivity was assessed.

RESULTS

ACC-HGT carried fewer copy number changes compared to solid ACC. Two ACC-HGT cases harboured a breakpoint at 6q23, near the cMYB oncogene. The complexity of the genomic profile concurred with the clinical course of the patient. Among the ACC-HGT, p53 positivity significantly increased from the conventional to the transformed (both MDA and PDC) component.

CONCLUSION

ACC-HGT may not necessarily reflect a more advanced stage of tumor progression, but rather a transformation to another histological form in which the poorly differentiated forms (PDC) presents a genetic complexity similar to the solid ACC.

Deficiency of SATB1 expression in Sezary cells causes apoptosis resistance by regulating FasL/CD95L transcription

Sézary syndrome (SS) is an aggressive subtype of cutaneous T-cell lymphoma that is characterized by circulating leukemic Sézary cells. The accumulation of these malignant cells has been shown to be the result of the resistance to apoptosis, in particular, activation-induced cell death. However, the mechanism of apoptosis resistance remains unknown. By characterizing the gene transcription profiles of purified CD4(+)CD7(-) Sézary cells from patients with SS and cultured Sézary cells, it was found that Sézary cells are deficient in the expression of special AT-rich region binding protein 1 (SATB1), a key regulator of T-cell development and maturation. Retrovirus-mediated gene transduction revealed that SATB1 restoration in cultured Sézary cells (Hut78) triggered spontaneous cell death and sensitized Hut78 cells to activation-induced cell death, with associated activation of caspase 8 and caspase 3. Furthermore, endogenous expression of FasL in Sézary cells was increased in transcriptional and translational levels on restoration of SATB1 expression in cultured Sézary cells. These results suggest that deficiency in SATB1 expression in Sézary cells plays an important role in SS pathogenesis by causing apoptosis resistance. Thus, restoration of SATB1 expression may represent a potential molecular targeted therapy for SS, which does not have a cure at present.

Insights into the stem cells of chronic myeloid leukemia

Chronic myeloid leukemia (CML) has long served as a paradigm for generating new insights into the cellular origin, pathogenesis and improved approaches to treating many types of human cancer. Early studies of the cellular phenotypes and genotypes represented in leukemic populations obtained from CML patients established the concept of an evolving clonal disorder originating in and initially sustained by a rare, multipotent, self-maintaining hematopoietic stem cell (HSC). More recent investigations continue to support this model, while also revealing new insights into the cellular and molecular mechanisms that explain how knowledge of CML stem cells and their early differentiating progeny can predict the differing and variable features of chronic phase and blast crisis. In particular, these emphasize the need for new agents that effectively and specifically target CML stem cells to produce non-toxic, but curative therapies that do not require lifelong treatments.

Chronic myelogenous leukemia stem cells: What's new?

Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder that arises in the hematopoietic stem cell compartment. CML is one of the best-understood malignancies, as it results from a single genetic mutation, the fusion oncogene BCR-ABL, which has been widely studied. Specific tyrosine kinase inhibitors have been developed to target BCR-ABL in CML, but these agents fail to eliminate the CML stem cell population and thus are unlikely to cure CML. This article reviews recent developments in the biology and treatment of CML, specifically focusing on CML stem cells. Significant progress continues to be made in our understanding of CML stem cell biology, which has wider implications within the cancer stem cell field. We are also beginning to see the identification of novel therapies that specifically target the CML stem cell. These are exciting times in the quest to cure CML.

Small interfering RNA against BCR-ABL transcripts sensitize mutated T315I cells to nilotinib

BACKGROUND

Selective inhibition of the BCR-ABL tyrosine kinase by RNA interference has been demonstrated in leukemic cells. We, therefore, evaluated specific BCR-ABL small interfering RNA silencing in BCR-ABL-positive cell lines, including those resistant to imatinib and particularly those with the T315I mutation.

DESIGN AND METHODS

The factor-independent 32Dp210 BCR-ABL oligoclonal cell lines and human imatinib-resistant BCR-ABL-positive cells from patients with leukemic disorders were investigated. The effects of BCR-ABL small interfering RNA or the combination of BCR-ABL small interfering RNA with imatinib and nilotinib were compared with those of the ABL inhibitors imatinib and nilotinib.

RESULTS

Co-administration of BCR-ABL small interfering RNA with imatinib or nilotinib dramatically reduced BCR-ABL expression in wild-type and mutated BCR-ABL cells and increased the lethal capacity. BCR-ABL small interfering RNA significantly induced apoptosis and inhibited proliferation in wild-type (P<0.0001) and mutated cells (H396P, T315I, P<0.0001) versus controls. Co-treatment with BCR-ABL small interfering RNA and imatinib or nilotinib resulted in increased inhibition of proliferation and induction of apoptosis in T315I cells as compared to imatinib or nilotinib alone (P<0.0001). Furthermore, the combination of BCR-ABL small interfering RNA with imatinib or nilotinib significantly (P<0.01) reversed multidrug resistance-1 gene-dependent resistance of mutated cells. In T315I cells BCR-ABL small interfering RNA with nilotinib had powerful effects on cell cycle distribution.

CONCLUSIONS

Our data suggest that silencing by BCR-ABL small interfering RNA combined with imatinib or nilotinib may be associated with an additive antileukemic activity against tyrosine kinase inhibitor-sensitive and resistant BCR-ABL cells, and might be an alternative approach to overcome BCR-ABL mutations.

The characterization of Abelson helper integration site-1 in skeletal muscle and its links to the metabolic syndrome

The human Abelson helper integration site-1 (AHI1) gene is associated with both neurologic and hematologic disorders; however, it is also located in a chromosomal region linked to metabolic syndrome phenotypes and was identified as a type 2 diabetes mellitus susceptibility gene from a genomewide association study. To further define a possible role in type 2 diabetes mellitus development, AHI1 messenger RNA expression levels were investigated in a range of tissues and found to be highly expressed in skeletal muscle as well as displaying elevated levels in brain regions and gonad tissues. Further analysis in a rodent polygenic animal model of obesity and type 2 diabetes mellitus identified increased Ahi-1 messenger RNA levels in red gastrocnemius muscle from fasted impaired glucose-tolerant and diabetic rodents compared with healthy animals (P < .002). Moreover, elevated gene expression levels were confirmed in skeletal muscle from fasted obese and type 2 diabetes mellitus human subjects (P < .02). RNAi-mediated suppression of Ahi-1 resulted in increased glucose transport in rat L6 myotubes in both the basal and insulin-stimulated states (P < .01). Finally, single nucleotide polymorphism association studies identified 2 novel AHI1 genetic variants linked with fasting blood glucose levels in Mexican American subjects (P < .037). These findings indicate a novel role for AHI1 in skeletal muscle and identify additional genetic links with metabolic syndrome phenotypes suggesting an involvement of AHI1 in the maintenance of glucose homeostasis and type 2 diabetes mellitus progression.