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ABSTRACT: Micro RNA (miRNA) is a small non-coding posttranscriptional RNA regulator that is involved in a variety of biological events. In order to specify the role of miRNAs in cartilage metabolism, we comparatively analyzed the expression profile of known miRNAs in chicken sternum chondrocytes representing early and late differentiation stages. Interestingly, none of the miRNAs displaying strong expression levels showed remarkable changes along with differentiation, suggesting their roles in maintaining the homeostasis rather than cytodifferentiation of chondrocytes. Among these miRNAs, miR-181a, which is known to play critical roles in a number of tissues, was selected and was further characterized. Human microarray analysis revealed remarkably stronger expression of miR-181a in human HCS-2/8 cells, which strongly maintained a chondrocytic phenotype, than in HeLa cells, indicating its significant role in chondrocytes. Indeed, subsequent investigation indicated that miR-181a repressed the expression of 2 genes involved in cartilage development. One was CCN family member 1 (CCN1), which promotes chondrogenesis; and the other, the gene encoding the core protein of aggrecan, a major cartilaginous proteoglycan, aggrecan. Based on these findings, negative feedback system via miR-181a to conserve the integrity of the cartilaginous phenotype may be proposed. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
Journal of Cellular Biochemistry 04/2013; · 2.87 Impact Factor
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ABSTRACT: In this article, we report the successful surgical treatment of a patient, 34 years of age, who had a severe gummy smile and a class II malocclusion. The patient had an 11-mm gingival exposure during full smile and a convex profile. A LeFort I osteotomy combined with a horseshoe osteotomy was used for the superior repositioning of the maxilla;then, an intraoral vertical ramus osteotomy (IVRO) and genioplasty were performed for mandibular advancement. The maxilla was acceptably impacted 8mm at the first incisor and 5mm at the first molar. Both the occlusion and facial appearance were significantly improved by this surgical-orthodontic treatment. Our results suggest that the combination of a horseshoe osteotomy with a LeFort I osteotomy is a useful technique for reliable superior repositioning of the maxilla.
Acta medica Okayama 02/2013; 67(1):55-60. · 0.84 Impact Factor
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ABSTRACT: Background and aim: Heat shock protein 90 (HSP90) and mammalian target of rapamycin (mTOR) are involved in the molecular pathogenesis of advanced oral squamous cell carcinoma. HSP90 inhibitors are capable of effectively interfering with multiple signaling pathways, including the mTOR signaling pathway. However, the combined effects of HSP90 and mTOR inhibitors on oral squamous cell carcinoma are still unknown. In this study, we investigated the dual treatment of the novel HSP90 inhibitor NVP-AUY922 and temsirolimus against oral squamous cell carcinoma. Materials and Methods: The effect of the combination of NVP-AUY922 and temsirolimus on oral squamous cell carcinoma in vitro and in vivo was determined by MTS assay and mouse xenograft models. The effect of the combination on angiogenesis was determined by tube formation assay and angioreactor. Results: The combination treatment of NVP-AUY922 and temsirolimus significantly inhibited the proliferation of SAS oral squamous cell carcinoma cells in vitro and suppressed the growth of oral squamous cell carcinoma xenografts in vivo. We have clearly shown that the combination treatment of NVP-AUY922 and temsirolimus inhibited vascular formation both in vitro and in vivo. Moreover, the combination treatment of NVP-AUY922 and temsirolimus prolonged the survival rate in mice xenografted with oral squamous cell carcinoma. Conclusions: Here, we showed the activity of a combination of mTOR and HSP90 inhibitors for the treatment of advanced oral squamous carcinoma.
Current cancer drug targets 09/2012; · 5.13 Impact Factor
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Naito Kurio, Tsuyoshi Shimo,
Takuya Fukazawa,
Tatsuo Okui,
Nur Mohammad Monsur Hassan,
Tatsuki Honami,
Yuu Horikiri,
Shinji Hatakeyama,
Munenori Takaoka,
Yoshio Naomoto,
Akira Sasaki
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ABSTRACT: Focal adhesion kinase (FAK) overexpression is frequently found in invasive and metastatic cancers, but its role in oral squamous cell carcinoma is not yet well understood. In order to seek therapies targeting oral squamous cell carcinoma, we developed the novel FAK Tyr(397) inhibitor TAE226 and investigated its anti-tumor effects and mechanisms.
Expression of phosphorylated FAK Tyr(397) was examined by immunohistochemical and immunoblot analysis. The effect of TAE226 on in vitro and in vivo studies were confirmed by proliferation, cell cycle, apoptosis and angiogenesis analysis.
We found that phosphorylated FAK was highly expressed in human tongue oral squamous cell carcinoma in patients. Importantly, TAE226 greatly suppressed the proliferation, migration and invasion of human oral squamous cell carcinoma SAS cells with an apparent structural change of actin fiber and a loss of cell adhesion. In addition, TAE226 inhibited the expression of phospho-FAK Tyr(397) and phospho AKT Ser(473), resulting in caspase-mediated apoptosis. Furthermore, oral administration of TAE226 in mice suppressed the growth and angiogenesis of oral squamous cell carcinoma xenografts in vivo.
Our results provide compelling evidence that FAK is critically involved in oral squamous cell carcinoma and that the FAK inhibitor TAE226 can potentially be effectively used for the treatment of oral squamous cell carcinoma.
Oral Oncology 07/2012; 48(11):1159-70. · 2.86 Impact Factor
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02/2012; , ISBN: 978-953-51-0024-9
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ABSTRACT: Sonic hedgehog (Shh) and its signaling have been identified in several human cancers, and increased levels of its expression appear to correlate with disease progression and metastasis. However, the role of Shh in bone destruction associated with oral squamous cell carcinomas, which frequently invade the maxilla or the mandible, is still unclear. In this study we show that the use of siRNA for Shh to block SHH secreted by SAS oral squamous cell carcinoma cells suppressed the tumor growth and tumor angiogenesis of subcutaneous SAS xenografts in vivo. Moreover, blockade of Shh in SAS cells decreased tumor growth and osteoclast number in a tibial metaphysis mouse model. Significantly, we clearly show that SHH stimulated osteoclast formation in a co-culture system consisting of murine bone stromal ST2 cells and murine CD11b(+) bone marrow cells. These findings suggest that Shh signaling is a potential target for the treatment of oral squamous cell carcinoma associated with bone destruction.
Oral Oncology 09/2011; 48(1):49-55. · 2.86 Impact Factor
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Toshihiro Ohgawara,
Satoshi Kubota,
Harumi Kawaki,
Naito Kurio,
Tarek Abd El Kader,
Mitsuhiro Hoshijima,
Danilo Janune, Tsuyoshi Shimo,
Bernard Perbal,
Akira Sasaki,
Masaharu Takigawa
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ABSTRACT: The CCN family of proteins consists of six members with conserved structural features. These proteins play several roles in the physiology and pathology of cells. Among the pathological roles of the CCN family, one of the most important and controversial ones is their role in the expansion and metastasis of cancer. Up to now a number of reports have described the possible role of each CCN family member independently. In this study, we comprehensively analyzed the roles of all six CCN family members in cell growth, migration and invasion of breast cancer cells in vitro and in vivo. As a result, we found the CCN2/CCN3 ratio to be a parameter that is associated with the metastatic phenotype of breast cancer cells that are highly metastatic to the bone. The same analysis with cell lines from oral squamous carcinomas that are not metastatic to the bone further supported our notion. These results suggest the functional significance of the interplay between CCN family members in regulating the phenotype of cancer cells.
Journal of Cell Communication and Signaling 04/2011; 5(4):291-9.
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ABSTRACT: Heat-shock protein 90 (HSP90) is a major cellular chaperone protein. HSP90 supports the correct conformation, stabilization, activation, and localization of 'client' oncoproteins, many of which are involved in tumor progression. Therefore, the use of HSP90 inhibitors has become a new strategy in antitumor therapy. However, the effects of an HSP90 inhibitor on oral squamous cell carcinoma are still unclear. NVP-AUY922 (Novartis) is a novel 4,5-diaryloxazole adenosine triphosphate-binding site HSP90 inhibitor. In this study, we investigated the antitumor effect of novel HSP90 inhibitor NVP-AUY922 against oral squamous cell carcinoma. NVP-AUY922 inhibited the proliferation of oral squamous cell carcinoma cells in vitro. NVP-AUY922 caused degradation of client protein inducing ErbB2, p-Akt, p-S6, hypoxia-inducible factor 1-α (HIF1-α) and vascular endothelial growth factor (VEGF) and up-regulation of HSP70 in HSC-2 oral squamous cell carcinoma. NVP-AUY922 increased the expression of cleaved caspase-3 and induced apoptosis in HSC-2 cells. Treatment of NVP-AUY922 induced a robust antitumor response and suppressed p-Akt and VEGF expression in an HSC-2 xenograft model. In summary, NVP-AUY922 exhibits in vitro and in vivo efficiency against oral squamous cell carcinoma, representing a promising therapeutic approach for oral squamous cell carcinoma.
Anticancer research 04/2011; 31(4):1197-204. · 1.73 Impact Factor
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ABSTRACT: Breast cancer cells frequently metastasize to the skeleton and produce and secrete proteinases, such as matrix metalloproteinase-13 (MMP-13), which promote destruction of the bone matrix. However, the mechanism of MMP-13 expression induced in areas of bone metastasis is unknown. Here, the interaction between tumors and type I collagen in bone metastasis was investigated.
A mouse model of bone metastasis was prepared by inoculating mice with suspensions of cells of the human metastatic breast cancer cell line MDA-MB-231 via the left cardiac ventricle. MMP-13 expression was examined by immunohistochemical, Western blot, and real-time RT-PCR analyses.
MMP-13 expression was highly up-regulated in MDA-MB-231 cells, and attachment of these cells to type I collagen and the induction of MMP-13 were down-regulated by treatment with integrin α1, α2 or β1 neutralizing antibodies. The attachment of MDA-MB-231 cells to type I collagen induced the activation of focal adhesion kinase (FAK) and p38 mitogen-activated protein kinase (MAPK). Inhibition of FAK and p38 MAPK down-regulated type I collagen-induced MMP-13 expression.
Our study indicates that metastatic breast cancer cells in the bone microenvironment attached to type I collagen, which stimulated integrins α1β1 and α2β1, via FAK and p38 MAPK pathways, to induce MMP13 expression and further osteolysis.
Anticancer research 04/2011; 31(4):1307-13. · 1.73 Impact Factor
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Naito Kurio, Tsuyoshi Shimo,
Takuya Fukazawa,
Munenori Takaoka,
Tatsuo Okui,
Nur Mohammad Monsur Hassan,
Tatsuki Honami,
Shinji Hatakeyama,
Masahiko Ikeda,
Yoshio Naomoto,
Akira Sasaki
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ABSTRACT: Focal adhesion kinase (FAK) is a 125-kDa non-receptor type tyrosine kinase that localizes to focal adhesions. FAK overexpression is frequently found in invasive and metastatic cancers of the breast, colon, thyroid, and prostate, but its role in osteolytic metastasis is not well understood. In this study, we have analyzed anti-tumor effects of the novel FAK Tyr(397) inhibitor TAE226 against bone metastasis in breast cancer by using TAE226. Oral administration of TAE226 in mice significantly decreased bone metastasis and osteoclasts involved which were induced by MDA-MB-231 breast cancer cells and increased the survival rate of the mouse models of bone metastasis. TAE226 also suppressed the growth of subcutaneous tumors in vivo and the proliferation and migration of MDA-MB-231 cells in vitro. Significantly, TAE226 inhibited the osteoclast formation in murine pre-osteoclastic RAW264.7 cells, and actin ring and pit formation in mature osteoclasts. Moreover, TAE226 inhibited the receptor activator for nuclear factor κ B Ligand (RANKL) gene expression induced by parathyroid hormone-related protein (PTHrP) in bone stromal ST2 cells and blood free calcium concentration induced by PTHrP administration in vivo. These findings suggest that FAK was critically involved in osteolytic metastasis and activated in tumors, pre-osteoclasts, mature osteoclasts, and bone stromal cells and TAE226 can be effectively used for the treatment of cancer induced bone metastasis and other bone diseases.
Experimental Cell Research 02/2011; 317(8):1134-46. · 3.58 Impact Factor
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ABSTRACT: Breast cancer (BC) cells often metastasize to bone where they express large amounts of parathyroid hormone-related protein (PTHrP). In this study, we investigated the possibility that PTHrP may have roles in breast cancer bone metastasis independently of, or in addition to, its roles in osteoclastic function.
A mouse model of bone metastasis was prepared by inoculating mice with suspensions of the human BC cell line MDA-MB-231 tumor cells via the left cardiac ventricle. Matrix metalloproteinase-13 (MMP-13) expression in the bone microenvironment was examined by Western blot and Real-time RT-PCR (RT-PCR) analysis, as well as by confocal microscopy.
The invading MDA-MB-231 cells contained conspicuous amounts of both PTHrP and MMP-13, an important matrix-degrading enzyme; and treatment of the cells in culture with exogenous PTHrP markedly stimulated MMP13 gene expression. Analysis of signaling mechanisms showed that PTHrP treatment led to rapid increases in the levels of phosphorylated protein kinase C (PKCα) and extracellular signal-regulated kinase (ERK1/2). Pharmacologic inhibition of ERK1/2 and PKC as well as of PKA activities counteracted the PTHrP-dependent stimulation of MMP13 expression. Indeed, pharmacologic activation of PKA or PKC was sufficient for stimulation of MMP13 expression.
Consistent with these findings, the inhibition of PKC prevented PTHrP-induced activation of ERK1/2, whereas 12-O-tetradecanoylphorbol-13-acetate (TPA), a stimulator of PKC, up-regulated the PTHrP-induced activation of ERK1/2. Taken together, our data indicate that the MDA-MB-231 breast cancer cells may carry out bone destruction and favor their own metastatic behavior by producing MMP-13. Given that the cells expressed PTHrP and that this factor stimulated MMP-13 expression, metastatic bone destruction may result from a PTHrP autocrine loop involving a PKC-ERK1/2 signaling pathway.
Anticancer research 12/2010; 30(12):5029-36. · 1.73 Impact Factor
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Soichiro IBARAGI,
Koji KISHIMOTO,
Norie YOSHIOKA,
Shohei DOMAE, Tsuyoshi SHIMO,
Kanako NAKATSUMA,
Sayoko TSUJIMOTO,
Naito KURIO,
Shinichi KODAMA,
Yuichiro TAKEBE,
Yu HORIKIRI,
Akane SHIBATA,
Akiyoshi NISHIYAMA,
Hiroshi MESE,
Akira SASAKI
The Journal of Okayama Dental Society. 12/2010; 29:107-112.
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ABSTRACT: The mammalian target of rapamycin (mTOR) is engaged in the molecular pathogenesis of oral squamous cell carcinoma, which frequently invades the maxilla or the mandible. However, the effects of a mTOR inhibitor on bone destruction associated with oral squamous cell carcinoma are still unclear. In this study, we investigated the antitumor effect of temsirolimus-mediated mTOR inhibition against advanced oral squamous cell carcinoma. Temsirolimus inhibited the proliferation and migration of HSC-2 oral squamous cell carcinoma cells in vitro and suppressed the growth of oral squamous cell carcinoma xenografts in vivo. Significantly, we clearly show that temsirolimus inhibited osteoclast formation both in vitro and in vivo. Reverse transcriptase-PCR analysis showed that temsirolimus decreased the mRNA expression of receptor activator for nuclear factor-κB ligand, known as an osteoclast differentiation factor in bone stromal ST2 cells. Moreover, temsirolimus normalized blood-free calcium concentration in mouse models for humoral hypercalcemia. These findings suggest that mTOR signaling is a potential target of oral squamous cell carcinoma associated with bone destruction, and hence we describe the efficacy of temsirolimus for the treatment of advanced oral squamous carcinoma.
Molecular Cancer Therapeutics 11/2010; 9(11):2960-9. · 5.23 Impact Factor
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Nur Mohammad Monsur Hassan,
Mitsuhiro Tada,
Masanobu Shindoh,
Jun-Ichi Hamada,
Haruhiko Kashiwazaki, Tsuyoshi Shimo,
Yuichi Ashikaga,
Yutaka Yamazaki,
Akira Sasaki,
Tetsuya Moriuchi,
Nobuo Inoue
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ABSTRACT: Patients with an oral squamous cell carcinoma (OSCC) often develop multiple malignant lesions. This report examined whether individual tumours developed in a patient show the same genetic alteration, such as p53 mutations. This case study describes three SCCs and three leukoplakias which developed simultaneously in a single 67-year-old Japanese man. A p53 mutation was detected in two of the three SCCs and one of the three leukoplakias. One SCC had a missense mutation at codon 285 (GAG>AAG, Glu>Lys) and the other a nonsense mutation at codon 336, and the leukoplakia had a missense mutation at codon 273 (CGT>CAT, Arg>His). This case showed that individual oral tumours may have different genetic changes even when they develop in a single patient. Therefore, this report provided strong evidence that in cases of multiple tumours it is necessary to design tailor-made therapies for each individual tumour rather than a single standardised therapy for all multiple tumours.
Anticancer research 11/2010; 30(11):4773-8. · 1.73 Impact Factor
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ABSTRACT: The process of endochondral ossification is strictly regulated by a variety of extracellular and intracellular factors. Recently, it has become recognized that specific miRNAs are involved in this process by regulating the expression of the relevant genes at the post-transcriptional level. In this present study we obtained the first evidence of the involvement of a specific micro RNA (miRNA) in the regulation of the chondrocyte phenotype during late stages of differentiation. By use of the microarray technique, miR-1 was identified as this miRNA, the expression of which was most repressed upon hypertrophic differentiation. Transfection of human chondrocytic HCS-2/8 cells and chicken normal chondrocytes with miR-1 led to repressed expression of aggrecan, the major cartilaginous proteoglycan gene. Therefore, miR-1 was found to be involved in the regulation of the chondrocytic phenotype and thus to play an important role in chondrocytes during the late stage of the differentiation process, maintaining the integrity of the cartilage tissue.
Biochemical and Biophysical Research Communications 10/2010; 402(2):286-90. · 2.48 Impact Factor
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ABSTRACT: Gingival squamous cell carcinoma (SCC) cells frequently invade mandibular bone, and this destruction is associated with a worse prognosis. However, the relationship between bone destruction and associated factors is unclear. In this study, the role and diagnostic utility of transforming growth factor-beta (TGF-beta) type I receptor (TbetaRI) in bone destruction of the mandible was investigated.
The expression of TbetaRI was explored by using an immunohistochemical method on paraffin-embedded tissues from 21 cases of mandibular SCC. An inhibitor of the kinase activity of the TbetaRI (TbetaRI-I) was used to assess the role of TbetaRI in bone destruction by a human oral SCC cell line (HSC-2) that highly expresses TbetaRI.
TbetaRI-positive signals were closely associated with destructive invasion of the mandible by oral SCC cells. Consistent with these results, TbetaRI-I greatly reduced HSC-2 cell-induced bone destruction and osteoclast formation in vivo and in vitro. TbetaRI-I treatment reduced the expression of TNF-alpha, RANKL and connective tissue growth factor (CTGF/CCN2), all of which were up-regulated by TGF-beta in HSC-2 cells.
These data demonstrated an important role for TGF-beta signalling in bone invasion by oral SCC cells, and suggest that the bone destruction is mediated by RANKL, TNF-alpha and CCN2.
Anticancer research 07/2010; 30(7):2615-23. · 1.73 Impact Factor
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ABSTRACT: Parathyroid hormone-related protein (PTHrP) is a key regulator of osteolytic metastasis of breast cancer (BC) cells, but its targets and mechanisms of action are not fully understood. This study investigated whether/how PTHrP (1-34) signaling regulates expression of vascular endothelial growth factor (VEGF) produced by BC cells.
A mouse model of bone metastasis was prepared by inoculating mice with tumour cell suspensions of the human BC cell line MDA-MB-231 via the left cardiac ventricle. VEGF expression was examined by Western blot and real-time RT-PCR analysis, as well as by confocal microscopy in the bone microenvironment.
PTHrP was expressed in cancer cells producing PTH/PTHrP receptor and VEGF that had invaded the bone marrow, and PTHrP was up-regulated VEGF in MDA-MB-231 in vitro. The culture medium conditioned by PTHrP-treated MDA-MB-231 cells stimulated angiogenesis and osteoclastogenesis compared with control medium, giving a response that was inhibited by VEGF-neutralizing antibody treatment. Inhibition of protein kinase C (PKC) prevented PTHrP-induced extracellular signal-regulated kinase (ERK1/2) and p38 activation, and PTHrP-induced VEGF expression.
PTHrP plays an important role in modulating the angiogenic and bone osteolytic actions of VEGF through PKC-dependent activation of an ERK1/2 and p38 signaling pathway during bone metastasis by breast cancer cells.
Anticancer research 07/2010; 30(7):2755-67. · 1.73 Impact Factor
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ABSTRACT: CCN2/CTGF is a multifunctional molecule that has been shown to play a central role in chondrocyte differentiation. During
this process, the expression of ccn2 is tightly regulated to confer a maximal level at prehypertrophic – hypertrophic stages, in which the 3'-untranslated region
(UTR) of the mRNA is critically involved in mediating its post-transcriptional regulation. In our previous studies, we found
that a 40-kDa protein binding specifically to an RNA cis-element, 3'-100/50, in the 3'-UTR of the chicken ccn2 mRNA regulated the intracellular stability of the mRNA. The interaction of this 40-kDa protein with 3′-100/50 was enhanced in proliferating chondrocytes, in which ccn2 mRNA is rapidly degraded; whereas a prolonged half life of ccn2 mRNA is observed in hypertrophic chondrocytes, where the interaction of the 40kDa-protein and 3'-100/50 is diminished. Collectively,
the data suggested that this 40-kDa protein acts as a ccn2-specific mRNA destabilizer during chondrocyte differentiation.
In this present study we finally identified this 40-kDa protein as nucleophosmin (NPM)/B23. NPM is a nuclear-cytoplasmic shuttling
protein that is characterized by its multiple functionality. This protein is known to be a histone chaperone, a regulator
of ribosomal RNA transcription, as well as an RNA-binding post-transcriptional regulator of gene expression. In our hands,
direct binding of NPM to 3'-100/50 was confirmed not only by RNA EMSA and UV crosslinking assays, but also by RNA immunoprecipitation
analysis. By using recombinant chicken NPM, we could successfully reconstitute the post-transcriptional regulation of ccn2 by NPM in vitro and found that this regulation was more robust in chondrocytes than in fibroblasts. Furthermore, siRNA-mediated
gene silencing of NPM in vivo clearly showed enhanced ccn2 gene expression and a prolonged half life of the ccn2 mRNA, confirming the functional property of NPM as a specific destabilizer of the ccn2 mRNA in living cells.
The 5'-100/50 element, a target of NPM, is evolutionally conserved among vertebrate species. Therefore, we consider NPM to
be a critical post-transcriptional regulator of ccn2 acting via 3'-UTR during endochondral ossification and possibly, in other physiological and pathological states as well.
KeywordsCCN2-Nucleophosmin-B23-Post-transcriptional regulation-Chondrocytes
04/2010: pages 41-55;
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ABSTRACT: The low-density lipoprotein receptor-related protein 1 (LRP1) is known as an endocytic and signal transmission receptor. We formerly reported the gene expression and the localization of LRP1 in cartilage tissue and chondrocytes, but its roles in the differentiation of chondrocytes remained to be investigated. Here, in order to address this issue, we employed RNAi strategy to knockdown lrp1 in chondrocytic cells and obtained findings indicating a critical role therein. As a result of lrp1 knockdown, aggrecan and col2a1 mRNA levels were decreased. However, that of col10a1 or mmp13 mRNA was rather increased. Under this condition, we performed a promoter assay for Axin2, which is known to be induced by activation of the WNT/beta-catenin (betacat) signaling pathway. Thereby, we found that Axin2 promoter activity was enhanced in the lrp1 knockdown cells. Furthermore, when the WNT/beta-catenin pathway was activated in chondrocytic cells by WNT3a or SB216763, which inhibits the phosphorylation of GSK3beta, the mRNA levels of aggrecan and col2a1 were decreased, whereas that of mmp13 was increased. Additionally, the level of phosphorylated protein kinase C (PKC) zeta was also decreased in the lrp1 knockdown cells. When the phosphorylation of PKCzeta was selectively inhibited, aggrecan and col2a1 mRNA levels decreased, whereas the mmp13 mRNA level increased. These data demonstrate that LRP1 exerts remarkable effects to retain the mature phenotype of chondrocytes as a critical mediator of cell signaling. Our findings also indicate that the onset of hypertrophy during endochondral ossification appears to be particularly dependent on the WNT and PKC signaling initiated by LRP1.
Journal of Cellular Physiology 09/2009; 222(1):138-48. · 3.87 Impact Factor
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ABSTRACT: CCN2/CTGF is a multifunctional factor that plays a crucial role in the growth and differentiation of chondrocytes. The chicken ccn2 gene is regulated not only at the transcriptional level but also by the interaction between a posttranscriptional element in the 3' untranslated region (3'-UTR) and a cofactor. In the present study, we identified a nucleophosmin (NPM) (also called B23) as this cofactor. Binding of NPM to the element was confirmed, and subsequent analysis revealed a significant correlation between the decrease in cytosolic NPM and the increased stability of the ccn2 mRNA during chondrocyte differentiation in vivo. Furthermore, recombinant chicken NPM enhanced the degradation of chimeric RNAs containing the posttranscriptional cis elements in a chicken embryonic fibroblast extract in vitro. It is noteworthy that the RNA destabilization effect by NPM was far more prominent in the cytosolic extract of chondrocytes than in that of fibroblasts, representing a chondrocyte-specific action of NPM. Stimulation by growth factors to promote differentiation changed the subcellular distribution of NPM in chondrocytes, which followed the expected patterns from the resultant change in the ccn2 mRNA stability. Therefore, the present study reveals a novel aspect of NPM as a key player in the posttranscriptional regulation of ccn2 mRNA during the differentiation of chondrocytes.
Molecular and cellular biology 09/2008; 28(19):6134-47. · 6.06 Impact Factor
