MOB1-YAP1/TAZ-NKX2.1 axis controls bronchioalveolar cell differentiation, adhesion and tumour formation.

Mps One Binder Kinase Activator (MOB)1A/1B are core components of the Hippo pathway. These proteins, which coactivate LArge Tumour Suppressor homologue kinases, are also tumour suppressors. To investigate MOB1A/B's roles in normal physiology and lung cancer, we generated doxycycline (Dox)-inducible, bronchioalveolar epithelium-specific, null mutations of MOB1A/B in mice (SPC-rtTA/(tetO)7-Cre/Mob1aflox/flox/Mob1b-/-; termed luMob1DKO mice). Most mutants (70%) receiving Dox in utero (luMob1DKO (E6.5-18.5) mice) died of hypoxia within 1 h post-birth. Their alveolar epithelial cells showed increased proliferation, impaired YAP1/TAZ-dependent differentiation and decreased surfactant protein production, all features characteristic of human respiratory distress syndrome. Intriguingly, mutant mice that received Dox postnatally (luMob1DKO (P21-41) mice) did not develop spontaneous lung adenocarcinomas, and urethane treatment-induced lung tumour formation was decreased (rather than increased). Lungs of luMob1DKO (P21-41) mice exhibited increased detachment of bronchiolar epithelial cells and decreased numbers of the bronchioalveolar stem cells thought to initiate lung adenocarcinomas. YAP1/TAZ-NKX2.1-dependent expression of collagen XVII, a key hemidesmosome component, was also reduced. Thus, a MOB1-YAP1/TAZ-NKX2.1 axis is essential for normal lung homeostasis and expression of the collagen XVII protein necessary for alveolar stem cell maintenance in the lung niche.

Intestinal epithelial culture under an air-liquid interface: a tool for studying human and mouse esophagi.

This study investigated whether an intestinal epithelial culture method can be applied to mouse and human esophageal cultures. The esophagi harvested from 1-day-old mice and adult humans were maintained in collagen gels. A commercially available culture medium for human embryonic stem cells was used for the human esophageal culture. We discovered that the intestinal epithelial culture method can be successfully applied to both mouse and human esophageal cultures. The long-term cultured esophageal organoids were rod-like luminal structures lined with myofibroblasts. We discovered that regeneration of the esophageal mucosal surface can be almost completely achieved in vitro, and the advantage of this method is that organoid cultures may be generated using host-derived fibroblasts as a niche. This method is a promising tool for mouse and human research in intestinal biology, carcinogenesis, and regenerative medicine.

Exosomal microRNA in serum is a novel biomarker of recurrence in human colorectal cancer.

BACKGROUND: Functional microRNAs (miRNAs) in exosomes have been recognised as potential stable biomarkers in cancers. The aim of this study is to identify specific miRNAs in exosome as serum biomarkers for the early detection of recurrence in human colorectal cancer (CRC). METHODS: Serum samples were sequentially obtained from six patients with and without recurrent CRC. The miRNAs were purified from exosomes, and miRNA microarray analysis was performed. The miRNA expression profiles and copy number aberrations were explored using microarray and array CGH analyses in 124 CRC tissues. Then, we validated exosomal miRNAs in 2 serum sample sets (90 and 209 CRC patients) by quantitative real-time RT-PCR. RESULTS: Exosomal miR-17-92a cluster expression level in serum was correlated with the recurrence of CRC. Exosomal miR-19a expression levels in serum were significantly increased in patients with CRC as compared with healthy individuals with gene amplification. The CRC patients with high exosomal miR-19a expression showed poorer prognoses than the low expression group (P<0.001). CONCLUSIONS: Abundant expression of exosomal miR-19a in serum was identified as a prognostic biomarker for recurrence in CRC patients.

Circulating tumour cell-derived plastin3 is a novel marker for predicting long-term prognosis in patients with breast cancer.

BACKGROUND: Identification of promising biomarkers that predict the prognosis of patients with breast cancer is needed. In this study, we hypothesised that the expression of the epithelial-mesenchymal transition-related biomarker plastin3 (PLS3) in peripheral blood could be a prognostic factor in breast cancer. METHODS: We examined PLS3 expression in breast cancer cell lines with epithelial and mesenchymal traits and in circulating tumour cells (CTCs) obtained from the peripheral blood of breast cancer patients. We investigated PLS3 expression in the peripheral blood of 594 patients with breast cancer to evaluate the clinical significance of PLS3 expression. RESULTS: Robust PLS3 expression was observed in different breast cancer cell lines (Hs578t, MCF-7, MDA-MB-468, and MDA-MB-231) as well as in a bone marrow derived cancer cell line (BC-M1). In both the training (n=298) and validation (n=296) sets, PLS3 expression was observed in CTCs of patients with breast cancer. PLS3-positive patients showed significantly poorer overall and disease-free survival than PLS3-negative patients (P=0.0001 and 0.003, respectively). Subset analysis revealed that this prognostic biomarker was relevant in patients with stage I-III cancer, particularly in patients with luminal-type and triple-negative-type tumours. CONCLUSIONS: These data demonstrated that PLS3 was expressed in CTCs undergoing the epithelial-mesenchymal transition in patients with breast cancer. Furthermore, PLS3 may be an excellent biomarker for identifying groups at risk of recurrence or with a poor prognosis.

Identification of a bona fide microRNA biomarker in serum exosomes that predicts hepatocellular carcinoma recurrence after liver transplantation.

BACKGROUND: Predictive biomarkers for the recurrence of hepatocellular carcinoma (HCC) have great benefit in the selection of treatment options, including liver transplantation (LT), for HCC. The purpose of this study was to identify specific microRNAs (miRs) in exosomes from the serum of patients with recurrent HCC and to validate these molecules as novel biomarkers for HCC recurrence. METHODS: We employed microarray-based expression profiling of miRs derived from exosomes in the serum of HCC patients to identify a biomarker that distinguishes between patients with and without HCC recurrence after LT. This was followed by the validation in a separate cohort of 59 HCC patients who underwent living related LT. The functions and potential gene targets of the recurrence-specific miRs were analysed using a database, clinical samples and HCC cell lines. RESULTS: We found that miR-718 showed significantly different expression in the serum exosomes of HCC cases with recurrence after LT compared with those without recurrence. Decreased expression of miR-718 was associated with HCC tumour aggressiveness in the validated cohort series. We identified HOXB8 as a potential target gene of miR-718, and its upregulation was associated with poor prognosis. CONCLUSION: Circulating miRs in serum exosomes have potential as novel biomarkers for predicting HCC recurrence.

The AURKA/TPX2 axis drives colon tumorigenesis cooperatively with MYC.

BACKGROUND: The MYC oncogene has long been established as a central driver in many types of human cancers including colorectal cancer. However, the realization of MYC-targeting therapies remains elusive; as a result, synthetic lethal therapeutic approaches are alternatively being explored. A synthetic lethal therapeutic approach aims to kill MYC-driven tumors by targeting a certain co-regulator on the MYC pathway. PATIENTS AND METHODS: We analyzed copy number and expression profiles from 130 colorectal cancer tumors together with publicly available datasets to identify co-regulators on the MYC pathway. Candidates were functionally tested by in vitro assays using colorectal cancer and normal fibroblast cell lines. Additionally, survival analyses were carried out on another 159 colorectal cancer patients and public datasets. RESULTS: Our in silico screening identified two MYC co-regulator candidates, AURKA and TPX2, which are interacting mitotic regulators located on chromosome 20q. We found the two candidates showed frequent co-amplification with the MYC locus while expression levels of MYC and the two genes were positively correlated with those of MYC downstream target genes across multiple cancer types. In vitro, the aberrant expression of MYC, AURKA and TPX2 resulted in more aggressive anchorage-independent growth in normal fibroblast cells. Furthermore, knockdown of AURKA or TPX2, or treatment with an AURKA-specific inhibitor effectively suppressed the proliferation of MYC-expressing colorectal cancer cells. Additionally, combined high expression of MYC, AURKA and TPX2 proved to be a poor prognostic indicator of colorectal cancer patient survival. CONCLUSIONS: Through bioinformatic analyses and experiments, we proposed TPX2 and AURKA as novel co-regulators on the MYC pathway. Inhibiting the AURKA/TPX2 axis would be a novel synthetic lethal therapeutic approach for MYC-driven cancers.

Amplification of PVT-1 is involved in poor prognosis via apoptosis inhibition in colorectal cancers.

BACKGROUND: We previously conducted gene expression microarray analyses to identify novel indicators for colorectal cancer (CRC) metastasis and prognosis from which we identified PVT-1 as a candidate gene. PVT-1, which encodes a long noncoding RNA, mapped to chromosome 8q24 whose copy-number amplification is one of the most frequent events in a wide variety of malignant diseases. However, PVT-1 molecular mechanism of action remains unclear. METHODS: We conducted cell proliferation and invasion assays using colorectal cancer cell lines transfected with PVT-1siRNA or negative control siRNA. Gene expression microarray analyses on these cell lines were also carried out to investigate the molecular function of PVT-1. Further, we investigated the impact of PVT-1 expression on the prognosis of 164 colorectal cancer patients by qRT-PCR. RESULTS: CRC cells transfected with PVT-1 siRNA exhibited significant loss of their proliferation and invasion capabilities. In these cells, the TGF-ß signalling pathway and apoptotic signals were significantly activated. In addition, univariate and multivariate analysis revealed that PVT-1 expression level was an independent risk factor for overall survival of colorectal cancer patients. CONCLUSION: PVT-1, which maps to 8q24, generates antiapoptotic activity in CRC, and abnormal expression of PVT-1 was a prognostic indicator for CRC patients.

PICT1 regulates TP53 via RPL11 and is involved in gastric cancer progression.

BACKGROUND: The TP53 pathway is frequently inactivated in human cancers. PICT1 (also known as GLTSCR2) is a novel regulator of the MDM2-TP53 pathway via its interaction with the ribosomal protein RPL11 in the nucleolus. However, the clinical significance of PICT1 in gastric cancer remains unknown. METHODS: To evaluate PICT1 function, we used shRNA to inhibit PICT1 expression in gastric cancer cells that expressed wild-type TP53. PICT1 expression and TP53 mutation status were quantified in 110 cases of primary gastric cancer to explore the impact of PICT1 expression levels on gastric cancer. RESULTS: Deficiency of PICT1 significantly impaired cell proliferation and colony formation via TP53-mediated cell cycle arrest. Following induction of PICT1 deficiency, RPL11 translocated out of the nucleolus. Of the 110 gastric cancer samples tested, 70 (63.6%) and 40 (36.4%) tumours expressed wild-type and mutant TP53, respectively. In gastric cancer patients with wild-type TP53 tumours, patients with relatively low PICT1 expression levels had a better prognosis compared with high expression level patients (P=0.046). CONCLUSION: The findings suggest that PICT1 has a crucial role in gastric cancer progression by regulating the MDM2-TP53 pathway through RPL11. Clinically, PICT1 expression is a novel prognostic parameter in gastric cancer patients with wild-type TP53 tumours.

Paired related homoeobox 1, a new EMT inducer, is involved in metastasis and poor prognosis in colorectal cancer.

BACKGROUND: Paired related homoeobox 1 (PRRX1) has been identified as a new epithelial-mesenchymal transition (EMT) inducer in breast cancer. However, the function of PRRX1 in colorectal cancer (CRC) has not been elucidated. METHODS: We utilised ectopic PRRX1-expressing cell lines to analyse the function of PRRX1 in CRC. The clinical significance of PRRX1 was also examined on three independent CRC case sets. RESULTS: PRRX1 induced EMT and the stem-like phenotype in CRC cells. In contrast to studies of breast cancer, abundant expression of PRRX1 was significantly associated with metastasis and poor prognosis in CRC. CONCLUSION: PRRX1 is an indicator of metastasis and poor prognosis in CRC cases. Further investigation is required to uncover the signalling network regulating PRRX1.

RPN2 expression predicts response to docetaxel in oesophageal squamous cell carcinoma.

BACKGROUND: Neoadjuvant chemotherapy - often using docetaxel in various combinatorial regimens - is a standard treatment choice for advanced oesophageal squamous cell carcinoma (ESCC) in Japan. However, no useful markers exist that predict docetaxel's effects on ESCC. Ribophorin II (RPN2) silencing, which reduces glycosylation of P-glycoproteins and decreases membrane localisation, promotes docetaxel-dependent apoptosis. We investigated whether RPN2 expression in ESCC biopsy specimens could be a predictive biomarker in docetaxel-based neoadjuvant chemotherapy. METHODS: We evaluated RPN2 expression immunohistochemically in biopsy specimens from 79 patients with node-positive ESCC, who received docetaxel-based adjuvant chemotherapy, and compared clinical and pathological responses between the RPN2-positive and RPN2-negative groups. We also studied susceptibility of RPN2-suppressed ESCC cells to docetaxel. RESULTS: The RPN2-negative group had better clinical and pathological responses to docetaxel than the RPN2-positive group. We also found RPN2 suppression to alter docetaxel susceptibility in vitro. CONCLUSION: Expression of RPN2 in biopsy specimens could be a useful predictive marker for response to docetaxel-based neoadjuvant chemotherapy in ESCC.

Clinical significance of miR-144-ZFX axis in disseminated tumour cells in bone marrow in gastric cancer cases.

BACKGROUND: We previously reported that bone marrow (BM) was a homing site for gastric cancer (GC) cells leading to haematogenous metastases. There has been little study that microRNAs regulated pathways in malignant cells or host cells in BM, and thereby regulated the progression of GC. METHODS: Both microRNA microarray and gene expression microarray analyses of total RNA from BM were conducted, comparing five early and five advanced GC patients. We focused on miR-144-ZFX axis as a candidate BM regulator of GC progression and validated the origin of the microRNA expression in diverse cell fractions (EpCAM(+)CD45(-), EpCAM(-)CD45(+), and CD14(+)) by magnetic-activated cell sorting (MACS). RESULTS: Quantitative reverse-transcriptase (RT)-PCR analysis validated diminished miR-144 expression in stage IV GC patients with respect to stage I GC patients (t-test, P=0.02), with an inverse correlation to ZFX (ANOVA, P<0.01). Luciferase reporter assays in five GC cell lines indicated their direct binding and validated by western blotting. Pre-miR144 treatment and the resultant repression of ZFX in GC cell lines moderately upregulated their susceptibility to 5-fluorouracil chemotherapy. In MACS-purified BM fractions, the level of miR-144 expression was significantly diminished in disseminated tumour cell fraction (P=0.0005). Diminished miR-144 expression in 93 cases of primary GC indicated poor prognosis. CONCLUSION: We speculate that disseminated cancer cells could survive in BM when low expression of miR-144 permits upregulation of ZFX. The regulation of the miR-144-ZFX axis in cancer cells has a key role in the indicator of the progression of GC cases.

Overexpression of microRNA-223 regulates the ubiquitin ligase FBXW7 in oesophageal squamous cell carcinoma.

BACKGROUND: F-box and WD repeat domain-containing 7 (FBXW7) is a cell cycle regulatory gene whose protein product ubiquitinates positive cell cycle regulators such as c-Myc, cyclin E, and c-Jun, thereby acting as a tumour-suppressor gene. This study focused on microRNA-223 (miR-223), which is a candidate regulator of FBXW7 mRNA. The aim of this study was to clarify the clinical significance of miR-223 and FBXW7 in oesophageal squamous cell carcinoma (ESCC) patients, and to elucidate the mechanism by which FBXW7 is regulated by miR-223. METHODS: The expression levels of miR-223 and the expression of FBXW7 protein was examined using 109 resected specimens to determine the clinicopathological significance. We also investigated the role of miR-223 in the regulation of FBXW7 expression in ESCC cell lines in an in vitro analysis. RESULTS: We found that miR-223 expression was significantly higher in cancerous tissues than in the corresponding normal tissues. There was a significant inverse relationship between the expression levels of miR-223 and FBXW7 protein. Moreover, patients with high miR-223 expression demonstrated a significantly poorer prognosis than those with low expression. On the basis of a series of gain-of-function and loss-of-function studies in vitro, we identified FBXW7 as a functional downstream target of miR-223. CONCLUSION: Our present study indicates that high expression of miR-223 had a significant adverse impact on the survival of ESCC patients through repression of the function of FBXW7.

The endoscopic diagnosis of nonerosive reflux disease using flexible spectral imaging color enhancement image: a feasibility trial.

Nonerosive reflux disease (NERD) is classified into grade M (minimal change, endoscopically; erythema without sharp demarcation, whitish turbidity, and/or invisibility of vessels due to these findings) and grade N (normal) in the modified Los Angeles classification system in Japan. However, the classification of grades M and N NERD is not included in the original Los Angeles system because interobserver agreement for the conventional endoscopic diagnosis of grades M or N NERD is poor. Flexible spectral imaging color enhancement (FICE) is a virtual chromoendoscopy technique that enhances mucosal and vascular visibility. The aim of this study is to evaluate whether the endoscopic diagnosis of grades M or N NERD using FICE images is feasible. Between April 2006 and May 2008, 26 NERD patients and 31 controls were enrolled in the present study. First, an experienced endoscopist assessed the color pattern of minimal change in FICE images using conventional endoscopic images and FICE images side-by-side and comparing the proportion of minimal change between the two groups. Second, three blinded endoscopists assessed the presence or absence of minimal change in both groups using conventional endoscopic images and FICE images separately. Intraobserver variability was compared using McNemar's test, and interobserver agreement was described using the kappa value. Minimal changes, such as erythema and whitish turbidity, which were detected using conventional endoscopic images, showed up as navy blue and pink-white, respectively, in color using FICE images in the present FICE mode. The NERD group had a higher proportion of minimal change, compared with the control group (77% and 48%, respectively) (P= 0.033). In all three readers, the detection rates of minimal change using FICE images were greater than those using conventional endoscopic images (P= 0.025, <0.0001, and 0.034 for readers A, B, and C, respectively). The kappa values for all pairs of three readers using FICE images were between 0.683 and 0.812, while those using conventional endoscopic images were between 0.364 and 0.624. Thus, the endoscopic diagnosis of grades M or N NERD using FICE images is feasible and may improve interobserver agreement.

The correlation between the telomeric parameters and the clinical laboratory data in the patients with brain infarct and metabolic disorders.

OBJECTIVE: To elucidate the correlation between the telomere length and subtelomeric methylated status in peripheral leukocytes and the laboratory data of inpatients with brain infarction and metabolic disorders. This is the first report describing a link between routine clinical laboratory data and genomic aging. DESIGN: Cross-sectional population-based study. SETTING: Chronic disease ward of Kyushu University Hospital at Beppu in Japan. PARTICIPANTS: Inpatients with brain infarction and metabolic disorders. MEASUREMENTS: The laboratory data of male patients were collected and the telomeric parameters in their peripheral leukocytes were determined by a Southern blot analysis with methylation-sensitive and insensitive isoschizomers. Any correlations between the laboratory data and the telomeric parameters were assessed. RESULTS: The patients revealed a significant correlation among the fasting blood sugar, HbA1c, serum creatinine and urea nitrogen levels with the mean telomere length, expression of long telomeres ( > 9.4 kb), or the subtelomeric hypermethylation status of long telomeres. CONCLUSION: Our results suggested that the hyperglycemia and renal function of patients with metabolic disorders correlated positively with the aging-associated telomeric changes.

Abnormal expression of TRIB3 in colorectal cancer: a novel marker for prognosis.

BACKGROUND: TRIB3 is a human homologue of Drosophila tribbles. Previous studies have shown that TRIB3 controls the cell growth through ubiquitination-dependent degradation of other proteins, whereas its significance in the prognosis of colorectal cancer (CRC) is not yet fully understood. MATERIALS: This study comprised 202 patients who underwent surgery for CRC, as well as 22 cell lines derived from human gastrointestinal cancer. The correlation of gene expression with clinical parameters in patients was assessed. The biological significance was evaluated by knockdown experiments in seven colorectal cancer cell lines. RESULTS: A total of 20 cancer cell lines (90.9%) expressed the TRIB3 gene. The assessment in surgical specimens indicated that the gene expression was significantly higher in the cancerous region than in the marginal non-cancerous region. Patients with high TRIB3 expression were statistically susceptible to a recurrence of the disease, and showed poorer overall survival than those with low expression. The assessment of TRIB3 knockdown in five cell lines showed that small interfering RNA (siRNA) inhibition resulted in a statistically significant reduction in cell growth. CONCLUSION: These data strongly suggest the usefulness of TRIB3 as a marker for predicting the prognosis of CRC patients, showing a basis for the development of effective treatments for CRC.

Bone marrow and peripheral blood expression of ID1 in human gastric carcinoma patients is a bona fide indicator of lymph node and peritoneal metastasis.

Recent studies have showed that the bone marrow-derived endothelial progenitor cells play critical roles in metastasis and that ID1 is required in metastasis as regulator of angiogenesis. Therefore, we investigated the clinical significance of ID1 mRNA expression in bone marrow and peripheral samples in patients with gastric cancer. Two hundred and eighty-nine bone marrow and 196 peripheral blood samples from gastric cancer patients were collected and analysed by quantitative RT-PCR for ID1. The ID1 protein expression in one bone marrow, three metastatic lymph nodes and three peritoneal disseminated tumours was examined by immunohistochemical methods. In both bone marrow and peripheral blood samples, ID1 mRNA expression in the metastatic group was significantly higher than in any other group (P=0.003, P=0.0001, respectively) and significantly associated with lymph node metastasis and peritoneal dissemination. The cells in bone marrow with metastatic cancer stained strongly with ID1 compared with those of healthy volunteers. The expression of ID1 mRNA in bone marrow and peripheral blood was significantly associated with lymph node metastasis and peritoneal dissemination, and therefore constitutes a predictable marker for lymph node metastasis and peritoneal dissemination.

Expression of uPAR mRNA in peripheral blood is a favourite marker for metastasis in gastric cancer cases.

Urokinase-type plasminogen activator receptor (uPAR) plays a central role in the plasminogen activation cascade and participates in extracellular matrix degradation, cell migration and invasion. We evaluated the expression level of uPAR mRNA and the presence of isolated tumour cells (ITCs) in bone marrow (BM) and peripheral blood (PB) in gastric cancer patients and clarified its clinical significance. We assessed specific uPAR mRNA expression by quantitative real-time reverse transcriptase- polymerase chain reaction (RT-PCR) in BM and PB in 846 gastric cancer patients as well as three epithelial cell markers, carcinoembryonic antigen (CEA), cytokeratin (CK)-19 and CK-7. The uPAR mRNA expression in bone marrow and peripheral blood expressed significantly higher than normal controls (P<0.0001). The uPAR mRNA in BM showed concordant expression with the depth of tumour invasion, distant metastasis, and the postoperative recurrence (P=0.015, 0.044 and 0.010, respectively); whereas in PB, we observed more intimate significant association between uPAR expression and clinicopathologic variables, such as depth of tumour invasion, the distant metastasis, the venous invasion and the clinical stage (P=0.009, 0.002, 0.039 and 0.008, respectively). In addition, the uPAR mRNA expression in PB was an independent prognostic factor for distant metastasis by multivariate analysis. We disclosed that it was possible to identify high-risk patients for distant metastasis by measuring uPAR mRNA especially in peripheral blood at the timing of operation in gastric cancer patients.

Clinical significance of LAMB3 and COL7A1 mRNA in esophageal squamous cell carcinoma.

AIMS: LAMB3 and COL7A1 genes code for the laminin-5beta3 chain and type VII collagen, respectively. They constitute the major components of the basement membrane zone. The aim of the current study was to clarify the clinical significance of LAMB3 and COL7A1 mRNA expression in esophageal squamous cell carcinoma (ESC). METHODS: We quantitated the expression of LAMB3 mRNA and COL7A1 mRNA in malignant esophageal tissues (T) and corresponding normal tissues (N) by real-time quantitative reverse transcription-polymerase chain reaction assays. The clinicopathologic significance of LAMB3 and COL7A1 expression was also determined. Paired T and N tissues were obtained from 66 patients who underwent curative esophagectomy. RESULTS: The expression levels of LAMB3 and COL7A1 mRNAs were higher in malignant tissues than in the corresponding normal tissues. The level of LAMB3 expression was significantly correlated with the depth of invasion and venous invasion (p=0.007 and 0.001, respectively). COL7A1 expression was significantly correlated with depth of tumor invasion and lymphatic invasion (p=0.046, 0.013, respectively). The five-year survival rate was better in the 22 patients with relatively low expression of both LAMB3 and COL7A1 in comparison with the other 44 cases (p<0.05). CONCLUSION: The evaluation of LAMB3 and COL7A1 mRNA expression is useful for predicting the malignant properties of ESC and may prove valuable in predicting the future course of the disease.

IL-6 induces osteoblastic differentiation of periodontal ligament cells.

Interleukin (IL)-6 has been considered as an osteolytic factor involved in periodontal disease. However, the function of IL-6 in osteoblastic differentiation of periodontal ligament cells is not clear. We examined the effects of IL-6 and its soluble receptor (sIL-6R) on osteoblastic differentiation of periodontal ligament cells. Osteoblastic differentiation was induced by ascorbic acid. Osteoblast markers, including alkaline phosphatase activity and Runx2 gene expression, were examined. The mechanism of action of IL-6 on osteoblastic differentiation was evaluated by insulin-like growth factor (IGF)-I production and specific inhibitors for the IL-6-signaling molecule. IL-6/sIL-6R enhanced alkaline phosphatase activity and Runx2. Alkaline phosphatase activity was reduced by anti-IGF-I antibody. Mitogen-activated protein kinase and Janus protein tyrosine kinase inhibitors diminished alkaline phosphatase induced by IL-6/sIL-6R. We conclude that IL-6/sIL-6R increases ascorbic-acid-induced alkaline phosphatase activity through IGF-I production, implying that IL-6 acts not only as an osteolytic factor, but also as a mediator of osteoblastic differentiation in periodontal ligament cells.