ATG5 regulates mesenchymal stem cells differentiation and mediates chemosensitivity in acute myeloid leukemia.

Autophagy is related to the development of several tumors including acute myeloid leukemia (AML). Inhibition of autophagy in AML cells can make them more susceptible to chemotherapy. However, the influence of autophagy in mesenchymal stem cells (MSCs) remains inconclusive. In the present study, we demonstrated that the expression of ATG5 and autophagy were elevated in MSCs derived from AML patients (AML-MSCs) compared to healthy donors (HD-MSCs). After inhibiting autophagy by 3-Methyladenine (3 MA) or silencing ATG5, the differentiation potential of AML-MSCs was decreased, the fraction of G0/G1 phase was increased while that of G2 phase was reduced, and the expression of CXCL12 was reduced in AML-MSCs. After co-culture of NB4 and THP1 with MSCs pretreated with 3 MA or ATG5 knockdown respectively, the sensitivity of AML cell lines to daunorubicin and doxorubicin was improved in a dose- and time-dependent manner compared to controls. The increased sensitivity of AML cells to genotoxic agents was related to ERK1/2 and AKT pathway. These results suggested ATG5 mediated potential differentiation capacities and cell cycle distribution of AML-MSCs, and targeting autophagy, especially ATG5 in AML-MSCs could improve the chemosensitivity of AML.

Interleukin-1ß inhibits normal hematopoietic expansion and promotes acute myeloid leukemia progression via the bone marrow niche.

Enhanced interleukin-1ß (IL-1ß) signaling is a common event in patients with acute myeloid leukemia (AML). It was previously demonstrated that chronic IL-1ß exposure severely impaired hematopoietic stem cell (HSC) self-renewal capability in mice and promoted leukemia cell growth in primary AML cells. However, the role of IL-1ß in the murine bone marrow (BM) niche remains unclear. Here, we explored the role of IL-1ß in the BM niche in Il-1r1-/- mice, chronic IL-1ß exposure mice and mixed lineage leukemia-AF9 fusion gene (MLL-AF9)-induced AML mice models. We demonstrated that IL-1R1 deficiency did not affect the function of HSCs or niche cells under steady-state conditions or during transplantation. Chronic exposure to IL-1ß decreased the expansion of Il-1r1-/- hematopoietic cells in Il-1r1+/+ recipient mice. These results indicated that IL-1ß exposure impaired the ability of niche cells to support hematopoietic cells. Furthermore, we revealed that IL-1R1 deficiency in niche cells prolonged the survival of MLL-AF9-induced AML mice. The results of our study suggest that inhibition of the IL-1ß/IL-1R1 signaling pathway in the niche might be a non-cell-autonomous therapy strategy for AML.

Upregulation of AKR1C1 in mesenchymal stromal cells promotes the survival of acute myeloid leukaemia cells.

The leukaemic bone marrow microenvironment, comprising abnormal mesenchymal stromal cells (MSCs), is responsible for the poor prognosis of acute myeloid leukaemia (AML). Therefore, it is essential to determine the mechanisms underlying the supportive role of MSCs in the survival of leukaemia cells. Through in silico analyses, we identified a total of 271 aberrantly expressed genes in the MSCs derived from acute myeloid leukemia (AML) patients that were associated with adipogenic differentiation, of which aldo-keto reductase 1C1 (AKR1C1) was significantly upregulated in the AML-MSCs. Knockdown of AKR1C1 in the MSCs suppressed adipogenesis and promoted osteogenesis, and inhibited the growth of co-cultured AML cell lines compared to the situation in wild- type AML-derived MSCs. Introduction of recombinant human AKR1C1 in the MSCs partially alleviated the effects of AKR1C1 knockdown. In addition, the absence of AKR1C1 reduced secretion of cytokines such as MCP-1, IL-6 and G-CSF from the MSCs, along with inactivation of STAT3 and ERK1/2 in the co-cultured AML cells. AKR1C1 is an essential factor driving the adipogenic differentiation of leukaemic MSCs and mediates its pro-survival effects on AML cells by promoting cytokine secretion and activating the downstream pathways in the AML cells.

[Bioinformatics Analysis and Verification of Aging-Related Genes of Bone Marrow Mesenchymal Stem Cells in Patients with Acute Myeloid Leukemia].

OBJECTIVE: To screen and verify the differentially expressed genes related with aging of bone marrow mesenchymal stem cells (BM-MSCs) in acute myeloid leukemia (AML) patients by bioinformatics, so as to provide new molecular markers for the research and clinical treatment of AML. METHODS: The gene expression profiling chip related with BM-MSCs in AML patients in our hospital and the gene chip GSE84881 selected from NCBI database GEO were used for data analysis and exploration. The DAVID analysis software was used to perform gene ontology (GO) enrichment analysis and KEGG pathway enrichment analysis. Furthermore, the differentially expressed genes related with aging of BM-MSCs in AML patients were identified. Bone marrow samples were collected and MSCs were amplified in vitro, and RT-PCR was used to verify the differentially expressed genes, which should be further identified with senescence-associated ß-galactosidase staining and MTT cell proliferation assays. RESULTS: A total of 247 differentially expressed genes were screened out by bioinformatics methods, including genes of 132 up-regulated expression and 115 down-regulated expression. Six differentially expressed genes related with aging of BM-MSCs in AML patients were screened out, including the genes of up-regulated expression, COL3A1 (P<0.05), CRYAB (P<0.01), DCN (P<0.05), and the genes of down-regulated expression, including CCL2 (P<0.05), CTSC (P<0.01) and IL6 (P<0.05). These 6 differentially expressed genes were consistent with data from chip assays, and which was significantly correlated with aging of BM-MSCs in AML patients. Meanwhile, the positive rate of senescence-associated ß-galactosidase staining in BM-MSCs of AML patients was significantly different from that of healthy donors (P<0.01). MTT cell proliferation assay showed that BM-MSCs in AML patients had proliferative ability lower than the healthy donors' BM-MSCs. CONCLUSION: The data here suggest novel clues for the clinical research and treatment of BM-MSCs aging in AML patients.

CXCL8 derived from mesenchymal stromal cells supports survival and proliferation of acute myeloid leukemia cells through the PI3K/AKT pathway.

The role of proinflammatory cytokines secreted by the bone marrow mesenchymal stromal cells (BM-MSCs) in the progression of acute myeloid leukemia (AML) is poorly understood. We compared C-X-C motif chemokine ligand (CXCL)8 expression levels in the BM-MSCs of patients with AML and normal control subjects and detected significantly higher levels in the former. Furthermore, CXCL8 was up-regulated in cocultures of BM-MSCs and leukemic cell lines compared with either monoculture. CXCL8 expression was significantly higher in MSCs compared with mononuclear cells in patients with de novo AML. To elucidate the function of paracrine CXCL8 in AML, we blocked CXCL8 binding to the C-X-C motif chemokine receptor (CXCR)2 in the AML cells using SB225002. Inhibition of CXCL8/CXCR2 binding decreased proliferation in the AML cells by inducing cell cycle arrest at the G0/G1 phase and apoptosis via decreased AKT phosphorylation. Blocking the PI3K/AKT signaling pathway by a specific inhibitor induced similar apoptosis induction and lower proliferation, suggesting that the PI3K/AKT signaling pathway was also involved in CXCL8 action. Taken together, our findings demonstrate that BM-MSCs are the main source of CXCL8 in the AML bone marrow microenvironment and promote leukemogenesis via the PI3K/AKT signaling pathway, indicating a novel therapeutic target.-Cheng, J., Li, Y., Liu, S., Jiang, Y., Ma, J., Wan, L., Li, Q., Pang, T. CXCL8 derived from mesenchymal stromal cells supports survival and proliferation of acute myeloid leukemia cells through the PI3K/AKT pathway.

CXCL8 is associated with the recurrence of patients with acute myeloid leukemia and cell proliferation in leukemia cell lines.

Acute myeloid leukemia (AML) blasts release a wide range of chemokines in which CXCL8 has recently been recognized to be important for tumor progression. To find out the function of CXCL8 in AML, we compared blood serum of AML patients and healthy donors and found that the average level of CXCL8 was higher in AML patients. Among patients, higher expression of CXCL8 was also a positive recurrence indicator which illustrated the critical role of CXCL8 in AML. Knocking down of CXCL8 in leukemic cell lines led to significant reduction of proliferation via inducing G0/G1 cell cycle arrest and apoptosis, which was accompanied by the inactivation of ERK1/2. Furthermore, inhibition of ERK1/2 by specific chemical inhibitors reconstructed the CXCL8 knocking down phenomenon. Overall, we demonstrated that expression level of CXCL8 had a positive relationship with recurrence probability in AML. And CXCL8 was strongly implicated in AML cells growth by activating the ERK1/2 signal pathway.

Sam68 affects cell proliferation and apoptosis of human adult T-acute lymphoblastic leukemia cells via AKT/mTOR signal pathway.

Sam68 (Src associated in mitosis, 68kDa) belongs to the signal，transduction and activation of RNA (STAR) family and its function has been linked to the onset and progression of many tumors. However, the role of Sam68 in T-acute lymphoblastic leukemia (T-ALL) remains unclear. This present study aimed to investigate whether and how Sam68 involved in T-ALL. Our results showed high expression of Sam68 in adult T-ALL cases, Jurkat and CCRF-CEM cell lines. Knockdown of Sam68 repressed cell proliferation, increased apoptosis, induced S arrest along with upregulation of p21, Bad, cleaved caspase-9, caspase-3, PARP and downregulation of CDK2 and Bcl-xl. Furthermore, the data indicated that the expression change of Sam68 went with the changes of AKT/mTOR signaling pathway in T-ALL cell lines. Our findings demonstrated that Sam68 possibly participated in the progresses of T-ALL at least partially via AKT/mTOR signaling pathway.

SIRT2 mediates multidrug resistance in acute myelogenous leukemia cells via ERK1/2 signaling pathway.

SIRT2, one of nicotinamide adenine dinucleotide (NAD+)-dependent class Ⅲ histone deacetylase family proteins, has been found to be involved in the proliferation and survival of acute myeloid leukemia (AML) cells. However, its effect on drug resistance on chemoresistant AML cells is unclear. In the present study, we first found that SIRT2 was expressed at higher level in the relapsed AML patients than the newly diagnosed patients. Consistent with this observation, the expression level of SIRT2 was higher in HL60/A cells than that in HL60 cells. Depletion of SIRT2 by shRNAs in HL60/A cells resulted in decreased MRP1 level, enhanced drug accumulation and triggered more apoptosis. By contrast, overexpression of SIRT2 in HL60 cells led to increased MRP1 level, drug efflux and attenuated drug sensitivity. Moreover, the decreased expression of phosphorylated ERK1/2 was detected in SIRT2-depleted HL60/A cells and increased expression of phosphorylated ERK1/2 was observed in SIRT2 overexpressed HL60 cells. Furthermore, blockage of ERK1/2 signaling pathway with the chemical inhibitor PD98059, further induced apoptosis of HL60/A cells conferred by SIRT2 depletion. Importantly, ERK1/2 inhibition was able to reverse the drug resistance of HL60 conferred by SIRT2 overexpression. Thus, our findings collectively suggested that the expression level of SIRT2 has a positive relationship with DNR/Ara-C resistance and activity of ERK1/2 signaling pathway. SIRT2 might regulate DNR/Ara-C sensitivity in AML cells at least partially through the ERK1/2 pathway.

Knock-down of CIAPIN1 sensitizes K562 chronic myeloid leukemia cells to Imatinib by regulation of cell cycle and apoptosis-associated members via NF-κB and ERK5 signaling pathway.

CIAPIN1 (cytokine-induced apoptosis inhibitor 1) was recently identified as an essential downstream effector of the Ras signaling pathway. However, its potential role in regulating myeloid leukemia cells sensitivity to Imatinib remains unclear. In this study, we found depletion of CIAPIN1 inhibited proliferation and triggered more apoptosis of K562CML (chronic myeloid leukemia) cells with or without Imatinib treatment. Meanwhile, CIAPIN1 depletion decreased ERK5 phosphorylation and NF-κB activity. Importantly, treating CIAPIN1-depleted K562 cells with ERK5 signaling pathway specific inhibitor, XMD8-92, further inhibited proliferation and promoted apoptosis with or without Imatinib treatment. Treatment with the NF-κB specific inhibitor, Bay 11-7082, induced nearly the same inhibition of proliferation and promotion of apoptosis conferred by CIAPIN1 depletion as was observed with XMD8-92 treatment. Further, XMD8-92 and Bay 11-7082 synergistically inhibited proliferation and promoted apoptosis of CIAPIN1-depleted K562 cells with or without Imatinib treatment. The nude mice transplantation model was also performed to confirm the enhanced sensitivity of CIAPIN1-depleted K562 cells to Imatinib. Thus, our results provided a potential management by which CIAPIN1 knock-down might have a crucial impact on enhancing sensitivity of K562 cells to Imatinib in the therapeutic approaches, indicating that CIAPIN1 knock-down might serve as a combination with chemotherapeutical agents in leukemia diseases therapy.

CIAPIN1 targets Na⁺/H⁺ exchanger 1 to mediate MDA-MB-231 cells' metastasis through regulation of MMPs via ERK1/2 signaling pathway.

Cytokine-induced antiapoptotic inhibitor 1 (CIAPIN1) was recently identified as an essential downstream effector of the Ras signaling pathway and has been confirmed to be closely associated with various malignant tumors. However, its potential role in regulating breast cancer metastasis remains unclear. Matrix metalloproteinases (MMPs) are a broad family of zinc-biding endopeptidases that participate in the extracellular matrix (ECM) degradation that accompanies cancer cell invasion, metastasis and angiogenesis. In this study, we found up-regulation of CIAPIN1 by lentiviral expression vector inhibited the migration, invasion and MMPs expression of MDA-MB-231 cells. Further, CIAPIN1 over-expression decreased NHE1 (Na(+)/H(+) exchanger 1) expression and ERK1/2 phosphorylation. Importantly, treating CIAPIN1 over-expressed MDA-MB-231 cells with the NHE1 specific inhibitor, Cariporide, further inhibited the metastatic capacity, MMPs expression and phosphorylated ERK1/2. Treatment with the MEK1 specific inhibitor, PD98059, induced nearly the same suppression of CIAPIN1 over-expression-dependent migration, invasion and MMPs expression as was observed with Cariporide. Further, Cariporide and PD98059 synergistically suppressed migration, invasion and MMPs expression of CIAPIN1 over-expressed MDA-MB-231 cells. Thus, our results revealed the mechanism by which CIAPIN1 targeted NHE1 to mediate migration and invasion of MDA-MB-231 cells through regulation of MMPs via ERK1/2 signaling pathway.

[Analysis of blood cell autophagy distribution in hematologic diseases by transmission electron microscope].

OBJECTIVE: To investigate the distribution characteristics of blood cells autophagy in hematologic diseases, as well as their possible pathomechanism. METHODS: Retrospective analysis of electron microscopy specimens of 3 277 patients with hematological diseases were performed. The blood cells autophagy was observed by transmission electron microscopy, and its distribution characteristics were analyzed. The pathomechanism of blood cell autophagy was explored in combination with clinical examination and diagnosis. RESULTS: There were 15 samples were found to have mature granulocytes or nucleated erythrocytes autophagy. Of them, 6 cases were myelodysplastic syndrome (MDS), 2 acute leukemia, 1 in each of aplastic anemia, pure red cell aplastic anemia, thalassemia, iron deficiency anemia, lymphoma, multiple myeloma and polycythemia vera. Among 15 cases, 11 cases were found to have mature granulocytes autophagy, 4 cases nucleated erythrocytes autophagy. Besides autophagy, apoptosis occurred in 9 cases, cytolysis in 6 cases, megaloblastic change in 5 cases. CONCLUSION: Mature granulocytes or nucleated erythrocytes autophagy occurred more frequently in MDS among hematologic diseases, dyshaematopoiesis including apoptosis, cytolysis and megaloblastic change could induce autophagy function enhancement.

Therapeutic effects of micheliolide on a murine model of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease and collagen-induced arthritis (CIA) is an animal model for RA. Micheliolide (MCL) is a novel compound with strong anti-inflammatory effects. The present study was conducted to evaluate the therapeutic effects of MCL on RA. Mice were randomly divided into four groups and the CIA model mice were treated with methotrexate (MTX), MCL and dimethyl sulfoxide. A score associated with the severity of arthritis was assigned on alternate days from the 22nd day for 60 days. Histopathological changes and the serum levels of cytokines were measured on day 85. The results demonstrated that the MCL treatment group had arthritis scores lower than the CIA group and higher than the MTX group; compared with the CIA group, MCL and MTX significantly reduced the swelling of the paws and suppressed the degeneration of articular cartilage. Expression levels of macrophage colony-stimulating factor (M-CSF), tissue inhibitors of metalloproteinases-1 (TIMP-1) and complement component 5a (C5/C5a) were lower in the mice with arthritis compared with normal mice, however, following treatment with MCL and MTX, all the mice exhibited significant recovery to differing degrees. Unlike the MTX group, the MCL group failed to recover the level of soluble intercellular adhesion molecule-1. In addition, the cytokine of B-lymphocyte chemoattractant (BLC) solely presented in the MCL group. These results suggest that MCL may be considered for use as a novel therapeutic treatment against RA and that changes in the expression of cytokines C5/C5a, TIMP-1, M-CSF and BLC may underlie the mechanism by which MCL effects changes in this disease.

[Effects of Sam68 gene silence on proliferation of acute T lymphoblastic leukemia cell line Jurkat].

This study was purpose to investigate the effect of Sam68 gene silence on proliferation of human acute T lymphoblastic leukemia cell line Jurkat. The sequence of shRNA targeting the site 531-552 of Sam68 mRNA was designed and chemically synthesized, then a single-vector lentiviral, Tet-inducible shRNA-Sam68 system (pLKO-Tet-On) was constructed; next the Jurkat cells were infected with lentivirus to create stable cell clones with regulatable Sam68 gene expression. The inhibitory efficiency of Sam68 gene was assayed by Real-time PCR and Western blot; the cell activity of Jurkat cells was detected with MTT assay; the change of colony forming potential of Jurkat cells was analyzed by colony forming test; the cell cycle distribution was tested by flow cytometry. The results indicated that the expression of Sam68 in experimental cells was statistically decreased as compared with that of the control cells; the cells activity and colony forming capacity of the Jurkat cells with Sam68 gene silence were significantly inhibited; with Sam68 gene silencing, the percentage of S phase cells was significantly increased, while the percentage of G2 phase cells was significantly decreased. It is concluded that the silencing Sam68 gene using shRNA interference can effectively inhibit the proliferation of human acute T lymphoblastic leukemia cell line Jurkat.

Down-regulation of the P-glycoprotein relevant for multidrug resistance by intracellular acidification through the crosstalk of MAPK signaling pathways.

In our previous study, we have found that the tumor multidrug resistance mediated by P-glycoprotein could be reversed by sustained intracellular acidification through down-regulating the multidrug resistance gene 1 mRNA and P-glycoprotein expression. However, the molecular events linking the intracellular acidification and the regulation of P-glycoprotein remain unclear. In the present study, the molecular pathways involved in the regulation of P-glycoprotein expression by the intracellular acidification were investigated. We found that the P-glycoprotein expression was down-regulated by the intracellular acidification through inhibition of p38 mitogen-activated protein kinase (MAPK) and the activation of c-Jun N-terminal kinase (JNK) in the resisitant K562/DOX cells. In the sensitive K562 and HL60 cell lines, the changes of the p38 MAPK expression after the acidification are not as obvious as that of K562/DOX cells, but the activation of extracellular signal-regulated kinase (ERK) is also observed, which indicates that the down-regulation of p38 MAPK by the intracellular acidification might be the resistant cell line specific. Blockade of ERK and JNK signaling by the inhibitors or RNA interference increased p38MAPK activities suggesting that cross-talk within MAPKs is also important for this response. Our study provides the first direct evidence that the reversal of P-glycoprotein-mediated multidrug resistance by intracellular acidification is mediated by the crosstalk of MAPK signaling pathways.

CIAPIN1 targets Na+/H+ exchanger 1 to mediate K562 chronic myeloid leukemia cells' differentiation via ERK1/2 signaling pathway.

CIAPIN1 (cytokine-induced antiapoptotic inhibitor 1) was recently identified as an essential downstream effector of the Ras signaling pathway. However, its potential role in regulating myeloid differentiation remains unclear. In this study, we found depletion of CIAPIN1 by shRNAs led to granulocytic differentiation of K562 cells. Meanwhile, the decrease of NHE1 and up-regulation of phosphorylated ERK1/2 were observed after CIAPIN1 depletion. Interestingly, targeted inhibition of NHE1 further promoted the differentiation of K562 cells with CIAPIN1 silencing. Accordingly, ectopic expression of NHE1 reversed this phenotype. Furthermore, ERK1/2 inhibition with the chemical inhibitor, PD98059, abolished CIAPIN1 silencing-induced differentiation of K562 cells after NHE1 inhibition. Thus, our results revealed important mechanism that CIAPIN1 targeted NHE1 to mediate differentiation of K562 cells via ERK1/2 pathway. Our findings implied CIAPIN1 and NHE1 could be new targets in developing therapeutic strategies against leukemia.

[Effect of CIAPIN1 gene on proliferation of K562 cells].

The study was aimed to investigate the effect of CIAPIN1 gene on the proliferation of chronic myeloid leukemia (CML) cell line K562. The shRNA eukaryotic expression vector targeting CIAPIN1 gene was constructed and transfected into K562 cells. The inhibitory efficiency on K562 cells was detected by real-time PCR and Western blot; the proliferative activity of K562 cells was detected by MTT assay; the number and size of colonies were assessed by using colony-forming test; the tumorigenic potential was tested in vivo by using nude mice. The results indicated that as compared with control group, the CIAPIN1 gene expression statistically decreased; the proliferative activity of K562 cells in interference group was distinctly weakened; the number and size of colonies were significantly reduced; the tumorigenic potential was also lowered in vivo. It is concluded that inhibition of CIAPIN1 expression can inhibit K562 cell proliferation in vitro and in vivo.

Umbilical cord-derived mesenchymal stem cells regulate thymic epithelial cell development and function in Foxn1(-/-) mice.

Thymic microenvironments are essential for the maturation of thymocytes, which can be anatomically compartmentalized into cortical and medullar regions. The absence of the gene encoding the transcription factor forkhead box n1 (Foxn1) causes epithelial differentiation to stall in the precursor stage, resulting in the formation of an abnormal thymus. In this study, we used human umbilical cord-derived mesenchymal stem cells (UC-MSCs) to treat Foxn1(-/-) mice, and then analyzed the maturation and distribution of thymic epithelial cells in the Foxn1(-/-) thymic rudiment and the thymopoiesis of this newly developed rudiment. Our data showed a well-organized cortex-medulla architecture and an obvious improvement in the maturation of thymic epithelial cells along with the appearance of UEA-1(+)MHCII(hi) thymic epithelial cells in the rudiment. We further demonstrated improved thymopoiesis and the enhanced export of mature T cells with increased numbers of regulatory T cells into the peripheral blood. Furthermore, we observed that MSCs can engraft into thymic tissue and express many cytokines or proteins, particularly keratinocyte growth factor (KGF) and CD248, which are essential for thymic development. Collectively, our data identified a new mechanism for MSCs, which may provide a proper microenvironment for the reconstitution and functional maturation of the thymus in Foxn1(-/-) mice. Additionally, we elicited additional insights into the therapeutic efficacy of MSCs in several autoimmune diseases.

Decreased intracellular pH induced by cariporide differentially contributes to human umbilical cord-derived mesenchymal stem cells differentiation.

BACKGROUND/AIMS: Na+/H+ exchanger 1 (NHE1) is an important regulator of intracellular pH (pHi). High pHi is required for cell proliferation and differentiation. Our previous study has proven that the pHi of mesenchymal stem cells is higher than that of normal differentiated cells and similar to tumor cells. NHE1 is highly expressed in both mesenchymal stem cells and tumor cells. Targeted inhibition of NHE1 could induce differentiation of K562 leukemia cells. In the present paper we explored whether inhibition of NHE1 could induce differentiation of mesenchymal stem cells. METHODS: MSCs were obtained from human umbilical cord and both the surface phenotype and functional characteristics were analyzed. Selective NHE1 inhibitor cariporide was used to treat human umbilical cord-derived mesenchymal stem cells (hUC-MSCs). The pHi and the differentiation of hUC-MSCs were compared upon cariporide treatment. The putative signaling pathway involved was also explored. RESULTS: The pHi of hUC-MSCs was decreased upon cariporide treatment. Cariporide up-regulated the osteogenic differentiation of hUC-MSCs while the adipogenic differentiation was not affected. For osteogenic differentiation, ß-catenin expression was up-regulated upon cariporide treatment. CONCLUSION: Decreased pHi induced by cariporide differentially contributes to hUC-MSCs differentiation.

Cariporide sensitizes leukemic cells to tumor necrosis factor related apoptosis-inducing ligand by up-regulation of death receptor 5 via endoplasmic reticulum stress-CCAAT/enhancer binding protein homologous protein dependent mechanism.

CCAAT/enhancer binding protein homologous protein (CHOP) expression increases when Na(+)-H(+) exchanger 1 (NHE1) is inhibited. Endoplasmic reticulum (ER) stress has been shown to trigger tumor cell death through CHOP. We therefore hypothesized that NHE1 activity correlates with ER stress and confers pharmaceutical potential to NHE1 inhibitor as an anti-tumor agent. The present study showed that treatment with the NHE1 inhibitor cariporide led to ER stress-induced up-regulation of the death receptor 5 (DR5) which is mediated by CHOP at the transcriptional level. We also determined that ER stress-induced Janus kinase (JNK) activation was responsible for the modulation of CHOP. Combining cariporide with tumor necrosis factor related apoptosis-inducing ligand (TRAIL) led to a significantly enhanced level of apoptosis that was abrogated by siRNA silencing of CHOP. This study provides a potential mechanistic rationale for the use of NHE1 inhibitor in combination with DR5 agonists to induce apoptosis in leukemia.

CD44 targets Wnt/ß-catenin pathway to mediate the proliferation of K562 cells.

BACKGROUND: Chronic myeloid leukemia is a clonal myeloproliferative disorder disease in which BCR/ABL plays an important role as an oncoprotein and molecular target. Despite the success of targeted therapy using tyrosine kinase inhibitors, CML remains largely incurable, most likely due to the treatment resistance after firstly chemical therapy. So know well the unique molecular pathway of CML is very important. METHODS: The expressions of CD44 in different leukemia patients and cell lines were detected by real-time PCR and western blotting. The effects of CD44 on proliferation of K562 cells were determined using the MTT and colony formation assays, and even in a nude mouse transplantation model. Then, the cell cycle changes were detected by flow cytometric analysis and the early apoptosis of cells was detected by the annexin V/propidium iodide double-staining assay. The expressions of the cycles and apoptosis-related proteins p21, Cyclin D1 and Bcl-2 were analyzed by western blot and real-time PCR assay. Finally, the decreased nuclear accumulation of ß-catenin was detected by western blotting and immunefluorescence. RESULTS: Firstly, we showed that CD44 expression was increased in several kinds of leukemia patients and K562 cells. By contrast, the down-regulation of CD44 resulted in decreased proliferation with a G0/G1 arrest of cell cycle in K562 cells according to the MTT assay and the flow cytometric analysis. And no significant induction of both the early and late phases of apoptosis was shown by the annexin V-FITC and PI staining. During this process, p21 and cyclin D1 are the major causes for cell cycle arrest. In addition, we found CD44 down-regulation decreased the expression of ß-catenin and increased the expression of phosphorylated ß-catenin. The instability of Wnt/ß-catenin pathway induced by increased expression of p-ß-catenin resulted in a decreased nuclear accumulation in CD44 silenced K562 cells. In the nude mouse transplantation model, we also found the same results. CONCLUSIONS: These results show that K562 cells depend to a greater extent on CD44 for proliferation, and CD44 down-regulation may induce a cell cycle arrest through Wnt/ß-catenin pathway. CD44 blockade may be beneficial in therapy of CML.