Epstein-barr virus infections induce aberrant osteoclastogenesis in immune system-humanized NOD/Shi-scid/IL-2RγCnull mice.

Epstein-Barr virus (EBV) and other viral infections are possible triggers of autoimmune diseases, such as rheumatoid arthritis (RA). To analyze the causative relationship between EBV infections and RA development, we performed experiment on humanized NOD/Shi-scid/IL-2RγCnull (hu-NOG) mice reconstituted human immune system components and infected with EBV. In EBV-infected hu-NOG mice, breakdown of knee joint bones was found to be accompanied by the accumulation of receptor activator of nuclear factor-κB (NF-κB) (RANK) ligand (RANKL), a key factor in osteoclastogenesis, human CD19 and EBV-encoded small RNA (EBER)-bearing cells. Accumulation of these cells expanded in the bone marrow adjacent to the bone breakage, showing a histological feature like to that in bone marrow edema. On the other hand, human RANK/human matrix metalloprotease-9 (MMP-9) positive, osteoclast-like cells were found at broken bone portion of EBV-infected mouse knee joint. In addition, human macrophage-colony stimulating factor (M-CSF), an essential factor in development of osteoclasts, evidently expressed in spleen and bone marrow of EBV-infected humanized mice. Furthermore, RANKL and M-CSF were identified at certain period of EBV-transformed B lymphoblastoid cells (BLBCs) derived from umbilical cord blood lymphocytes. Co-culturing bone marrow cells of hu-NOG mice with EBV-transformed BLBCs resulted in the induction of a multinucleated cell population positive for tartrate-resistant acid phosphatase and human MMP-9 which indicating human osteoclast-like cells. These findings suggest that EBV-infected BLBCs induce human aberrant osteoclastogenesis, which cause erosive arthritis in the joints.

Influence of doctor-patient relationships and health-related factors on the medical satisfaction of patients with Sjögren's disease.

OBJECTIVES: Patients with chronic, incurable conditions rely on their providers to help relieve their symptoms. Dissatisfaction with their care can erode the doctor-patient relationship and reduce the effectiveness of treatment. We investigated the relationships between satisfaction and symptoms, the doctor-patient relationship, and health-related factors in patients with Sjögren's disease (SjD) in Japan. METHODS: Using a questionnaire survey, we evaluated via multinomial logistic regression associations between satisfaction [satisfied, neither (neither satisfied nor dissatisfied), dissatisfied] and symptoms, prescribed medications, anxiety, distress, expectations from treatments, and doctor-patient relationships. RESULTS: Of 259 patients, 101 (39%) were satisfied, 111 (42.9%) were neither, and 47 (18.2%) were dissatisfied. Patients who were neither or dissatisfied with their current treatment wanted their systemic pain to disappear (adjusted relative risk ratio [aRRR] 3.38, 95% CI 1.66-6.91; aRRR 3.04, 95% CI 1.30-7.15, respectively). Patients who used artificial saliva only were significantly more dissatisfied (aRRR 3.52, 95% CI 1.03-2.04). Both the neither and dissatisfied patients dissatisfied with their doctor's limited understanding of SiD (aRRR 12.69, 95% CI 4.21-38.24; aRRR 32.76, 95% CI 10.09-106.34, respectively) and with the limited opportunities to ask their doctor about their disease (aRRR 0.19, 95% CI 0.06-0.59; aRRR 0.08, 95% CI 0.02-0.24, respectively). CONCLUSIONS: Pain and the use of artificial saliva alone markedly affected medical satisfaction and we expected the future advance in these two areas, pain and dryness, will improve satisfaction. It is most important for doctors to better understand SjD.

Abatacept ameliorates both glandular and extraglandular involvements in patients with Sjögren's syndrome associated with rheumatoid arthritis: Findings from an open-label, multicentre, 1-year, prospective study: The ROSE (Rheumatoid Arthritis with Orencia Trial Toward Sjögren's Syndrome Endocrinopathy) and ROSE II trials.

OBJECTIVE: To clarify the efficacy and safety of intravenous abatacept for glandular and extraglandular involvements in Sjögren's syndrome (SS) associated with rheumatoid arthritis (RA). MATERIALS AND METHODS: We performed an open-label, prospective, 1-year, observational multicenter study (ROSE and ROSE II trials). The primary endpoint was the remission rate as measured by SDAI at 52 weeks. The secondary endpoints included the changes in the Saxon's test, Schirmer's test, ESSDAI and ESSPRI. Adverse events and adherence rates were also analyzed. RESULTS: 68 patients (36 in ROSE and 32 in ROSE II, all women) were enrolled. SDAI decreased significantly from 23.6 ± 13.2 at baseline to 9.9 ± 9.5 at 52 weeks. Patients with SDAI remission increased from 0 (0 weeks) to 19 patients (27.9%) at 52 weeks. Saliva volume increased significantly at 24 weeks. Tear volume increased significantly at 52 weeks. Both ESSDAI and ESSPRI were significantly decreased at 12 weeks, and these responses were maintained up to 52 weeks. The rate of adherence to abatacept over the 52-week period was 83.8%. Twenty-two adverse events occurred in 15 patients. CONCLUSION: Abatacept ameliorated both glandular and extraglandular involvements, as well as the systemic disease activities and patient-reported outcomes based on composite measures, in SS associated with RA.

No evidence of bovine leukemia virus proviral DNA and antibodies in human specimens from Japan.

BACKGROUND: The potential risk and association of bovine leukemia virus (BLV) with human remains controversial as it has been reported to be both positive and negative in human breast cancer and blood samples. Therefore, establishing the presence of BLV in comprehensive human clinical samples in different geographical locations is essential. RESULT: In this study, we examined the presence of BLV proviral DNA in human blood and breast cancer tissue specimens from Japan. PCR analysis of BLV provirus in 97 Japanese human blood samples and 23 breast cancer tissues showed negative result for all samples tested using long-fragment PCR and highly-sensitive short-fragment PCR amplification. No IgG and IgM antibodies were detected in any of the 97 human serum samples using BLV gp51 and p24 indirect ELISA test. Western blot analysis also showed negative result for IgG and IgM antibodies in all tested human serum samples. CONCLUSION: Our results indicate that Japanese human specimens including 97 human blood, 23 breast cancer tissues, and 97 serum samples were negative for BLV.

von Willebrand factor activity levels are influenced by driver mutation status in polycythemia vera and essential thrombocythemia patients with well-controlled platelet counts.

von Willebrand factor ristocetin cofactor (vWF activity) and platelet count (PLT) are negatively correlated in patients with polycythemia vera (PV) and essential thrombocythemia (ET). However, vWF activity does not always normalize upon controlling PLT in those patients. To address this issue, we investigated the correlation between vWF activity and PLT in PV and ET patients. The negative correlation between vWF activity and PLT was stronger in calreticulin mutation-positive (CALR+) ET than in Janus kinase 2 mutation-positive (JAK2+) PV or ET groups. When PLT were maintained at a certain level (<600 × 109 /L), low vWF activity (<50%) was more frequently observed in JAK2+ PV patients than in JAK2+ ET (p = .013) or CALR+ ET (p = .013) groups, and in PV and ET patients with ≥50% JAK2+ allele burden than in those with allele burden <50% (p = .015). High vWF activity (>150%) was more frequent in the JAK2+ ET group than in the CALR+ ET group (p = .005), and often associated with vasomotor symptoms (p = .002). This study suggests that some patients with JAK2+ PV or ET have vWF activity outside the standard range even with well-controlled PLT, and that the measurement of vWF activity is useful for assessing the risk of thrombosis and hemorrhage.

Involvement of Epstein-Barr virus in the development and spontaneous regression of methotrexate-associated lymphoproliferative disorder in patients with rheumatoid arthritis.

OBJECTIVES: Conventionally, some patients with methotrexate-associated lymphoproliferative disorder (MTX-LPD) undergo spontaneous tumour regression after cessation of MTX. Although the involvement of Epstein-Barr virus (EBV) in the development and spontaneous regression has been suggested, the underlying mechanism remains unknown. In this study, we analysed patients who had developed MTX-LPD to evaluate the association between the development and spontaneous regression of MTX-LPD with EBV. METHODS: We analysed the age, stage, disease activity, MTX dose, lymphocyte count, EBV real-time polymerase chain reaction (PCR) test value, and EBV-encoded small RNA (EBER) positivity rate in patients with MTX-LPD at our hospital. Moreover, we investigated the factors related to spontaneous regression, which is a characteristic of MTX-LPD. RESULTS: Thirty-four patients were enrolled in this study. The MTX dose at LPD onset was 8.3±2.0 mg/week, and the total dose of MTX was 1,530.3±779.2 mg. The EBV load in the peripheral blood was 270.4±431.8 copy/µL, and the pathological tissues of 17 of 34 (50%) patients tested positive for EBER. Twenty-one patients had spontaneous regression after discontinuation of MTX. The factors related to spontaneous regression were examined using a univariate analysis, and the EBV real-time PCR test value in the peripheral blood, EBER in pathological tissues, and improvement rate of lymphocyte count were considered significant factors. The EBV real-time PCR test value in the peripheral blood was defined as an independent factor of spontaneous regression using a multivariate analysis of related factors. CONCLUSIONS: EBV may be involved in the development of MTX-LPD and its spontaneous regression.

Relationship between Carnitine Deficiency and Tyrosine Kinase Inhibitor Use in Patients with Chronic Myeloid Leukemia.

BACKGROUND: Some chemotherapeutic agents cause carnitine deficiency, which causes general fatigue. However, there is no study on carnitine deficiency in patients with chronic myeloid leukemia (CML) during tyrosine kinase inhibitor (TKI) therapy. OBJECTIVE: In this study, we investigated carnitine concentrations in patients with CML receiving TKI therapy. METHOD: This study included patients with well-controlled CML. Total carnitine and free carnitine concentrations were evaluated using the enzyme cycling method. The brief fatigue inventory (BFI) and cancer fatigue scale (CFS) were used to assess general fatigue developed during TKI therapy. RESULTS: Fifty-five patients on TKI therapy were included. Of these, 12 (21.8%) patients had low free carnitine concentrations. Free carnitine concentrations were higher in men than in women. Younger age was closely associated with lower free carnitine concentrations. TKI type, TKI dose, treatment response, or therapy duration were not associated with free carnitine concentrations. None of the scores (the global fatigue score with the BFI and CFS score) correlated with carnitine concentrations. Concentrations of free carnitine in patients in the treatment-free remission group were slightly higher than those in the TKI group, with only 9.1% having a low concentration of free carnitine. CONCLUSION: Carnitine deficiency is probably not a major cause of general fatigue but may occur in patients with CML receiving TKI therapy.

Factors associated with delayed diagnosis of Sjögren's syndrome among members of the Japanese Sjögren's Association for Patients.

OBJECTIVES: The heterogeneous nature of the signs and symptoms of Sjögren's syndrome (SS) often causes delays in diagnosis. The reasons for these delays have not been investigated in Japan and need to be determined. METHODS: We conducted a questionnaire survey of members of the Japanese Sjögren's Association for Patients (JSAP). Questionnaire items were demographic (sex, age at diagnosis and current age) and factors associated with delayed diagnosis (age at first visit to hospital or clinic, medical department first attended, and initial symptoms). Patients were classified into those diagnosed in <1 year and those diagnosed in ≥1 year. RESULTS: Of the 510 patients questioned, 276 returned the questionnaire, and 255 questionnaires were assessed. The average time to diagnosis was 3.47 years. After adjustment, risk factors for delayed diagnosis were initial visit to an internal medicine department [adjusted odds ratio (aOR) 3.13, 95% confidence interval (CI) 1.42-6.92] or ophthalmology department (aOR, 2.63, 95% CI 1.07-6.50), younger age at initial visit to hospital or clinic (aOR, 0.96, 95% CI 0.94-0.99), and having symptoms of only dry eye (aOR, 2.69, 95% CI 1.09-6.64). Diagnosis was faster when patients had a dry mouth (aOR, 0.55, 95% CI 0.30-1.00) or cutaneous symptoms (aOR, 0.29, 95% CI 0.11-0.82). CONCLUSIONS: Risk factors for delayed SS diagnosis were younger age, initial visit to internal medicine or ophthalmology department, and having only dry eye. We need to raise awareness of SS among doctors and the general public to improve early diagnosis and therapeutic potential.

Increased Arbekacin Clearance in Patients With Febrile Neutropenia.

BACKGROUND: Arbekacin (ABK) is used to treat infections caused by methicillin-resistant Staphylococcus aureus and is used widely for the treatment of febrile neutropenia (FN). As ABK has a narrow therapeutic concentration window, the dosage must be adjusted via therapeutic drug monitoring. However, the influence of the physiology of patients with FN on the pharmacokinetic (PK) parameters of ABK remains unclear. Therefore, we examined this influence on ABK PK parameters. METHOD: We performed a retrospective cohort study using data from patients with a hematologic malignancy who were ≥18 years and had been administered ABK. We excluded patients who did not receive therapeutic drug monitoring and had an estimated glomerular filtration rate (eGFR) of <30 mL/min, because clinically sufficient data would not be available. RESULT: Of the 99 enrolled patients, 25 did not have FN and 74 had FN. Arbekacin clearance (CLabk) was shown to correlate with eGFR in patients with FN (r = 0.32, P = 0.0062) and without FN (r = 0.50, P = 0.01). CLabk was higher in patients with FN than in those without FN. In addition, in the eGFR of <100 mL/min group (normal renal function), CLabk and CLabk/eGFR were also higher in patients with FN than in those without FN. CONCLUSIONS: CLabk was increased in patients with FN and normal renal function; therefore, we propose an increased ABK dose for patients with FN and normal renal function.

Absence of bovine leukemia virus proviral DNA in Japanese human blood cell lines and human cancer cell lines.

Bovine leukemia virus (BLV) infects cattle worldwide and causes B-cell lymphoma in cattle. BLV has been identified in human breast and lung cancer and in blood, but the association of BLV and human cancer is controversial. In this study, we investigated the existence of BLV in 145 Japanese human blood cell lines and 54 human cancer cell lines, using a new highly sensitive PCR assay that can amplify even one copy of BLV using LTR primers different from those in previous studies on BLV provirus in breast cancer. All samples were found negative for BLV provirus, suggesting that BLV is unlikely to infect humans.

Identification of a Novel ACVRL1 Gene Mutation (c.100T>A, p.Cys34Ser) in a Japanese Patient with Possible Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Disease).

Hereditary hemorrhagic telangiectasia (HHT; also known as Osler-Weber-Rendu disease) is an autosomal dominant genetic disorder that causes frequent epistaxis, mucocutaneous telangiectasia, and visceral arteriovenous malformations. Four genes (ENG, ACVRL1, SMAD4, and GDF2) have been identified as pathogenic in HHT. We describe the case of a 50-year-old Japanese man highly suspected of having HHT due to recurrent epistaxis, mucocutaneous telangiectasia, and a family history. Genomic analysis revealed a novel missense mutation of c.100T>A, p.Cys34Ser in the patient's ACVRL1 gene. We used 6 freeware programs to perform an in silico analysis of this mutation. The results demonstrated the mutation's high pathogenicity.

[Transformation of CD5-positive nodal marginal zone lymphoma to diffuse large B-cell lymphoma].

Nodal marginal zone lymphoma (NMZL) is a form of nodal B-cell lymphoma exhibiting proliferation of abnormal lymphocytes at the circumference of the mantle zone in the lymph nodes. Although the outcome of patients with this disease is often favorable, we recently encountered a patient with a CD5-positive NMZL who was resistant to chemotherapy. A 67-year-old woman complaining of systemic lymph node swelling was referred to our hospital. After biopsy of the neck lymph node, she was diagnosed with CD5-positive NMZL. Disease progression was revealed after 16 months, and she was initially treated with chemotherapy consisting of rituximab, cyclophosphamide, vincristine, and prednisolone (R-CVP). However, this therapy was ineffective. Subsequent therapy with rituximab and bendamustine also failed to induce remission. A rebiopsy revealed that the NMZL had transformed into a diffuse large B-cell lymphoma. This patient died after 2 years from the initial diagnosis due to lymphoma progression. Cases of CD5-positive NMZL are rare; thus, it is difficult to study the clinical implications of CD5 expression in this disease. Here we describe the current understanding of CD5 expression in NMZL.

Identification of human immunodeficiency virus type-1 Gag-TSG101 interaction inhibitors by high-throughput screening.

The interaction between viral protein Gag and cellular protein tumor susceptibility gene 101 (TSG101) is a crucial step in the HIV-1 replication cycle. This interaction initiates the viral assembly/budding via the cellular endosomal sorting complexes required for transport (ESCRT) pathway, making it a potential target for antiviral therapy. Here we developed a simple, robust, and reliable high-throughput screening (HTS) system based on enzyme-linked immunosorbent assay (ELISA) to identify compounds that inhibit HIV-1 replication by targeting Gag-TSG101 interaction. Through screening of the 9600-compound library using the established HTS system, several hit compounds, which inhibited Gag-TSG101 interaction, were identified. Subsequent assays revealed two hit compounds, HSM-9 and HSM-10, which have antiviral activity against CD4+ T cell-tropic NL4-3 and macrophage-tropic JR-CSF HIV-1 strains. These results suggest that our established HTS system is an indispensable tool for the identification of HIV-1 Gag-TSG101 interaction inhibitors.

Combined treatment with benzo[a]pyrene and 1α,25-dihydroxyvitamin D3 induces expression of plasminogen activator inhibitor 1 in monocyte/macrophage-derived cells.

Benzo[a]pyrene (BaP) is an environmental pollutant found in cigarette smoke and is implicated as a causative agent of tobacco-related diseases, such as arteriosclerosis. In contrast, vitamin D signaling, which is principally mediated by conversion of vitamin D to the active form, 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], decreases cardiovascular disease risk. However, combined treatment with BaP and 1,25(OH)2D3 enhances BaP toxicity, including BaP-DNA adduct formation. We further investigated the cross-talk between BaP and 1,25(OH)2D3 signaling pathways, and found that combined treatment with these compounds induces mRNA and protein expression of plasminogen activator inhibitor 1 (PAI-1) in monocyte/macrophage-derived THP-1 and U937 cells. Protein synthesis inhibitor treatment did not inhibit induction of the PAI-1 gene (SERPINE1) in these cells. BaP plus 1,25(OH)2D3 induced differentiation markers, inhibited cellular proliferation, and induced apoptosis and oxidative stress in these cells. Reactive oxygen species scavenger treatment suppressed apoptosis but not SERPINE1 induction in cells treated with BaP plus 1,25(OH)2D3. Thus, combined treatment with BaP and 1,25(OH)2D3 induced SERPINE1 mRNA expression in these cells through a mechanism that does not require de novo protein synthesis or reactive oxygen species production. These findings suggest that induction of the proinflammatory factor PAI-1 plays a role in BaP toxicity. Interestingly, PAI-1 knockdown decreased expression of the cell surface antigen CD14, a monocytic differentiation marker, in THP-1 cells treated with BaP plus 1,25(OH)2D3. PAI-1 induction may also be related to a function of monocytes/macrophages in response to xenobiotic and vitamin D signaling.

One percent chlorhexidine-alcohol for preventing central venous catheter-related infection during intensive chemotherapy for patients with haematologic malignancies.

A central venous catheter (CVC) is a catheter placed into a large vein, and is used for chemotherapy administration. However, there is little confirmatory data on which antiseptic-such as chlorhexidine or povidone-iodine (PI) -is more protective against CVC-related infectious complications in patients receiving intensive chemotherapy. We aimed to compare the effectiveness of 1% chlorhexidine gluconate in 70% alcohol (CH) vs. PI for skin disinfection before CVC insertion in patients receiving intensive chemotherapy. Methods We used either CH or 10% PI as skin antiseptics before CVC insertion, and assessed which agent was more protective against CVC-related infection. The participants were 112 patients with haematologic malignancies who underwent chemotherapy; a total of 292 CVCs were inserted over this period. Blood cultures were obtained when febrile neutropenia occurred. The CVC was removed and the catheter-tip qualitatively cultured when catheter-related infection was suspected. The cumulative incidence of febrile neutropenia, microbial growth from blood or catheter-tip culture, and catheter-related blood stream infection (CRBSI) was evaluated retrospectively. A univariate Cox proportional hazards model showed that CH significantly alleviated infectious complications. Notably, no case of CRBSI occurred in the CH group. Multivariate analysis, adjusted for prolonged neutropenia (>15 days) and older age (>52 years), also showed significant reduction in the cumulative incidence of microbial growth from catheter-tips in the CH group (hazard ratio = 0.146, 95% confidence interval: 0.023-0.502, p = 0.0008). Disinfection using CH, compared with PI, can potentially decrease catheter-related infection without causing adverse skin reactions in patients with haematologic malignancies.

Lyn, a tyrosine kinase closely linked to the differentiation status of primary acute myeloid leukemia blasts, associates with negative regulation of all-trans retinoic acid (ATRA) and dihydroxyvitamin D3 (VD3)-induced HL-60 cells differentiation.

BACKGROUND: Lyn, an import member of Src family kinases (SFKs), is supposed to be implicated in acute myeloid leukemia (AML) pathogenesis and development by participation in AML differentiation, yet the details still remain incompletely understood. The expression status of Lyn and its correlation with multiple clinical parameters including cell differentiation degree, different cytogenetic risk classification, and the activity of myeloperoxidase (MPO) were thus investigated. To address the mechanisms underlying the involvement of Lyn in differentiation induction, the effects of dasatinib, an inhibitor for SFKs including Lyn, on the alterations of all-trans retinoic acid (ATRA)- or dihydroxyvitamin D3 (VD3)-induced differentiation, and c-Myc protein expression were investigated. METHODS: Primary AML blasts were obtained from 31 newly diagnosed AML patients with different French-American-British (FAB) subtypes. The expression of phosphorylated and total Lyn, c-Myc, and CD11b, CD11c and CD15 was analyzed by flow cytometry. The activation of Akt and Erk known to be involved in the regulation of c-Myc expression was investigated using western blotting. RESULTS: Significant higher expression levels of total Lyn were observed in AML patients with favorable cytogenetics, higher MPO activity and FAB M2 subtype. A clear positive correlation between the expression levels of Lyn and differentiation status of primary AML blasts was observed. Dasatinib inhibited the expression of phosphorylated Lyn, and further enhanced the differentiation-inducing activity of ATRA and VD3 in HL-60 cells. Augmented downregulation of c-Myc protein expression was observed in the combination treatment with ATRA, VD3 and dasatinib compared to treatment with each reagent alone in HL-60 cells. The suppression of the activation of Akt and Erk was also observed concomitantly. CONCLUSIONS: The expression level of total Lyn is closely linked to the differentiation status of AML blasts. The enhancement of differentiation-inducing activity of ATRA/VD3 by dasatinib suggested that Lyn was associated in the negative regulation of ATRA/VD3-induced HL-60 cells differentiation. The enhancement probably was attributed to the downregulation of c-Myc implicated with the suppression of the activation of Akt and Erk. These results provide novel insights into a possible combinational therapeutic approach by targeting Lyn for AML patients, and offer new possibilities for the combination therapy with VD3 and dasatinib.

Self-assembly formed by a short DNA probe pair: Application for highly sensitive mRNA species detection without reverse transcription.

We describe a novel technology for detecting nucleic acids: Probe Alteration Link Self-Assembly Reactions (PALSAR). PALSAR comprises DNA self-assembly of pairs of short DNA probes formed by alternate hybridization of three complementary regions in a pair of honeycomb probes (HCPs). Self-assembly occurs at designated salt concentrations and reaction temperatures and requires no enzymes. We prepared pairs of HCPs to detect mRNAs encoded by the GAPDH gene ß-actin (BA) gene, CD3D gene, CD4 gene, major vault protein (MV) gene and the signalling lymphocytic activation molecule-associated protein (SAP) gene, and succeeded in quantitatively detecting these mRNAs. PALSAR could detect mRNA directly without synthesizing cDNA. Moreover, multiple mRNAs could be detected simultaneously in a single reaction tube and there was a good correlation between the results obtained PALSAR and those by real-time PCR.

Granulocyte colony-stimulating factor potentiates all-trans retinoic acid-induced granulocytic differentiation in acute promyelocytic leukemia cell line HT93A.

BACKGROUND: Granulocyte colony-stimulating factor (G-CSF) promotes proliferation, survival, and differentiation of myeloid-linage leukemic cells, as well as normal hematopoietic cells. Terminal granulocytic differentiation can be induced in acute promyelocytic (APL) cell line HT93A by G-CSF and all-trans retinoic acid (ATRA). Because the detailed mechanism has never been shown, we investigated the signal transduction pathway in granulocytic differentiation by G-CSF, alone or in combination with ATRA. METHODS: HT93A cell viability and growth were investigated by trypan blue exclusion assay. Cell differentiation was assessed by CD11b and CD34 expressions. Intracellular protein expressions were also evaluated by flow cytometry after fixation and permeabilization. RESULTS: ATRA (100 nM) induced granulocytic differentiation (upregulation of CD11b and downregulation of CD34) and the effect was potentiated by addition of G-CSF, while G-CSF alone had no effect on HT93A cells. The addition of G-CSF to ATRA had little or no effect on NB4 and THP-1 cells in comparison to ATRA alone. G-CSF receptor expression was reduced by ATRA treatment in a time-dependent manner. After 5 days' incubation with ATRA, the expression levels of signal transducer and activator of transcription (STAT) 3, and phosphorylated STAT3 and STAT5, were significantly reduced. STAT5 was strongly activated by G-CSF stimulation in ATRA-pretreated cells in comparison to untreated cells. In contrast, STAT3 showed no response to G-CSF. Janus kinase (JAK) inhibitor ruxolitinib (320 nM) had little or no effect on ATRA-induced differentiation, but eliminated the enhancing effect of G-CSF, as evidenced by the levels of CD11b and CD34 expression. These results suggest G-CSF activates STAT5 through the JAK pathway in combination with ATRA, resulting in myeloid differentiation in HT93A cells. CONCLUSIONS: In conclusion, activation of the JAK-STAT pathway is likely essential for inducting differentiation in the APL cell line HT93A; thus, monitoring its expression and activation is important for predicting clinical efficacy and understanding the mechanisms of cytokine-dependent myelopoiesis, proliferation, and differentiation of acute myeloid leukemia.