Immunohistochemical detection of insulin-like growth factors, platelet-derived growth factor, and their receptors in ameloblastic tumors

BACKGROUND: To evaluate the roles of growth factors in oncogenesis and cytodifferentiation of odontogenic tumors, expression of insulin-like growth factors (IGFs), platelet-derived growth factor (PDGF), and their receptors was analyzed in ameloblastic tumors as well as in tooth germs. METHODS: Tissue specimens of 10 tooth germs, 47 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against IGF-I, IGF-II, IGF-I receptor (IGF-IR), PDGF A-chain, PDGF B-chain, PDGF alpha-receptor, and PDGF beta-receptor. RESULTS: Immunohistochemical reactivity for IGFs, PDGF chains, and their receptors was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and in benign and malignant ameloblastic tumors. The expression levels of IGF-II and PDGF chains were significantly higher in ameloblastic tumors than in tooth germs. Malignant ameloblastic tumors showed higher reactivity for PDGF chains than benign ameloblastomas and higher reactivity for platelet-derived growth factor receptors than tooth germs. The expression levels of PDGF chains were significantly higher in follicular ameloblastomas than in plexiform ameloblastomas. Desmoplastic ameloblastomas showed higher expression of IGFs and IGF-IR when compared with other ameloblastoma subtypes. CONCLUSION: Expression of IGFs, PDGF, and their receptors in tooth germs and ameloblastic tumors suggests that these growth factor signals contribute to cell proliferation or survival in both normal and neoplastic odontogenic tissues. Expression of these molecules in odontogenic tissues possibly affects interactions with the bone microenvironment during tooth development and intraosseous progression of ameloblastic tumors. Altered expression of the ligands and receptors in ameloblastic tumors may be involved in oncogenesis, malignant potential, and tumor cell differentiation.     

Immunohistochemical detection of platelet-derived endothelial cell growth factor/thymidine phosphorylase and angiopoietins in ameloblastic tumors

BACKGROUND: To evaluate the roles of angiogenic factors in the development and progression of odontogenic tumors, expression of platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) and of angiopoietins in ameloblastic tumors as well as in tooth germs. METHODS: Tissue specimens of 11 tooth germs, 44 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against PD-ECGF/TP and angiopoietin-1 and -2. RESULTS: Immunohistochemical reactivity for PD-ECGF/TP was detected in mesenchymal cells in tooth germs and stromal cells in ameloblastic tumors, and the level of immunoreactivity for PD-ECGF/TP was significantly higher in ameloblastomas than in tooth germs. Granular cell ameloblastomas showed PD-ECGF/TP reactivity in granular neoplastic cells as well as in stromal cells. Immunoreactivity for angiopoietin-1 and -2 was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and in benign and malignant ameloblastic tumors. Malignant ameloblastic tumors had decreased angiopoietin-1 reactivity and ameloblastic carcinomas had increased angiopoietin-2 reactivity as compared with the respective levels in tooth germs and ameloblastomas. Immunohistochemical reactivity for angiopoietin-2 was slightly higher in follicular ameloblastomas than in plexiform ameloblastomas. CONCLUSION: Expression of PD-ECGF/TP and angiopoietin-1 and -2 in tooth germs and ameloblastic tumors suggests that these angiogenic factors participate in tooth development and odontogenic tumor progression by regulating angiogenesis. Altered expression of PD-ECGF/TP and angiopoietins in ameloblastic tumors may be involved in oncogenesis, malignant potential, and tumor cell differentiation.     

Immunohistochemical detection of BH3-only proteins in ameloblastic tumors

Objective:  To evaluate expression of BH3-only proteins in odontogenic tumors, expression of Bid, Bim, Bad, Noxa, and Puma was analyzed in ameloblastic tumors as well as in tooth germs.
Methods:  Nine tooth germs, 37 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with antibodies against Bid, Bim, Bad, Noxa, and Puma.
Results:  Immunohistochemical reactivity for Bid, Bim, Bad, Noxa, and Puma was detected in the cytoplasm of cellular components in normal and neoplastic odontogenic tissues. Expression of these BH3-only proteins was evident in odontogenic epithelial cells near the basement membrane in tooth germs and ameloblastic tumors. Acanthomatous ameloblastomas showed no reactivity for Bid, Bim, Bad, Noxa, or Puma in keratinizing cells, whereas granular cells in granular cell ameloblastomas reacted with these BH3-only proteins. Basal and desmoplastic ameloblastomas and ameloblastic carcinomas showed immunoreactivity for the BH3-only proteins in most neoplastic cells.
Conclusion:  Expression of Bid, Bim, Bad, Noxa, and Puma in tooth germs and ameloblastic tumors suggests that the BH3-only proteins have a role in apoptotic cell death of normal and neoplastic odontogenic epithelium. Distinctive expression patterns of these BH3-only proteins in ameloblastoma variants suggest that the BH3-only proteins might be involved in tumor cell differentiation of ameloblastomas.     

The immunoprofile of odontogenic keratocyst (keratocystic odontogenic tumor) that includes expression of PTCH, SMO, GLI-1 and bcl-2 is similar to ameloblastoma but different from odontogenic cysts

Background:  The aggressive biological behavior of odontogenic keratocysts (OKCs), unlike that of other odontogenic cysts, has argued for its recent re-classification as a neoplasm, 'keratocystic odontogenic tumor'. Identification of mutations in the PTCH gene in some of the OKCs that were expected to produce truncated proteins, resulting in loss of control of the cell cycle, provided additional support for OKCs having a neoplastic nature.
Methods:  We investigated the immunohistochemical expression of the sonic hedgehog (SHH) signaling pathway-related proteins, PTCH, smoothened (SMO) and GLI-1, and of the SHH–induced bcl-2 oncoprotein in a series of primary OKC (pOKC), recurrent OKC (rOKC) and nevoid basal cell carcinoma syndrome-associated OKCs (NBCCS-OKCs), and compared them to solid ameloblastomas (SAMs), unicystic ameloblastomas (UAMs), 'orthokeratinized' OKCs (oOKCs), dentigerous cysts (DCs) and radicular cysts (RCs).
Results:  All studied lesions expressed the SHH pathway-related proteins in a similar pattern. The expression of bcl-2 in OKCs (pOKCs and NBCCS-OKCs) and SAMs was significantly higher than in oOKCs, DCs and RCs ( P  <   0.001).
Conclusions:  The present results of the immunoprofile of OKCs (that includes the expression of the SHH-related proteins and the SHH-induced bcl-2 oncoprotein) further support the notion of OKC having a neoplastic nature. As OKCs vary considerably in their biologic behavior, it is suggested that the quality and quantity of interactions between the SHH and other cell cycle regulatory pathways are likely to work synergistically to define the individual phenotype and corresponding biological behavior of this lesion.     

The association of platelet-derived growth factor (PDGF) receptor tyrosine phosphorylation to mitogenic response of human osteoblastic cells in vitro

OBJECTIVES: The purpose of this study was to make clear the relationship of human osteoblastic ceil growth, induced by platelet-derived growth factor (PDGF), to PDGF receptor tyrosine phosphorylation.
MATERIALS AND METHODS: Osteoblastic cells derived from human maxilla were cultured with human PDGF. The cell growth was evaluated by cell number and DNA synthesiS. PDGF receptor tyrosine phosphorylation was detected by immunoblot analysis using anti-PDGF receptor α, β subunits and anti-phosphotyrosine antibodieS. Genistein, a tyrosine kinase inhibitor, was added to the culture to investigate the effect on osteoblastic cell growth and PDGF receptor tyrosine phosphorylation induced by PDGF.
RESULTS AND CONCLUSIONS: PDGF stimulated the proliferation of human osteoblastic cells and this effect was synergetic with serum stimulation. DNA synthesis of osteoblastic cells was elevated by PDGF in a dose dependent manner at the minimum concentration of I ng ml^-1.PDGF also induced PDGF receptor tyrosine phosphorylation within 1 min on osteoblastic cells, and tyrosine phosphorylation occurred on PDGF receptor subunits α and β.Genistein inhibited cell growth and receptor tyrosine phosphorylation, which was induced by PDGF on these cellS. In conclusion, human osteoblastic cell growth induced by PDGF is shown to relate to tyrosine kinase of PDGF receptors.     

Platelet-derived growth factor-B gene delivery sustains gingival fibroblast signal transduction

Background and Objective: Platelet‐derived growth factor‐BB is a potent mediator of tooth‐supporting periodontal tissue repair and regeneration. A limitation of the effects of topical platelet‐derived growth factor‐BB application is its short half‐life in vivo. Gene therapy has shown strong promise for the long‐term delivery of platelet‐derived growth factor in both skin ulcer healing and periodontal tissue engineering. However, little is known regarding the extended effects of platelet‐derived growth factor‐B on cell signaling via gene delivery, especially at the level of phosphorylation of intracellular kinases. This study sought to evaluate the effect of gene transfer by Ad‐PDGF‐B on human gingival fibroblasts (HGFs) and the subsequent regulation of genes and cell‐surface proteins associated with cellular signaling. Material and Methods: HGFs from human subjects were treated by adenoviral PDGF‐B, PDGF‐1308 (a dominant negative mutant of PDGF) and recombinant human platelet‐derived growth factor‐BB, and then incubated in serum‐free conditions for various time points and harvested at 1, 6, 12, 24, 48, 72 and 96 h. Exogenous PDGF‐B was measured by RT‐PCR and Western blot. Cell proliferation was evaluated by [methyl‐³H]thymidine incorporation assay. We used proteomic arrays to explore phosphorylation patterns of 23 different intracellular kinases after PDGF‐B gene transfer. The expression of α and β PDGFR and Akt were measured by Western blot analysis. Results: Sustained in vitro expression of PDGF‐B in HGFs by Ad‐PDGF‐B transduction was seen at both the mRNA and protein levels. Compared to rhPDGF‐BB and Ad‐PDGF‐1308, Ad‐PDGF‐B maintained cell growth in serum‐free conditions, with robust increases in DNA synthesis. Gene delivery of PDGF‐B also prolonged downregulation of the growth arrest specific gene (gas) PDGFαR. Of the 23 intracellular kinases that we tested in proteomic arrays, Akt revealed the most notable long‐term cell signaling effect as a result of the over‐expression of Ad‐PDGF‐B, compared with pulse recombinant human platelet‐derived growth factor BB. Prolonged Akt phosphorylation was induced by treatment with Ad‐PDGF‐B, for at least up to 96 h. Conclusion: These findings further demonstrate that gene delivery of PDGF‐B displays sustained signal transduction effects in human gingival fibroblasts that are higher than those conveyed by treatment with recombinant human platelet‐derived growth factor‐BB protein. These data on platelet‐derived growth factor gene delivery contribute to an improved understanding of these pathways that are likely to play a role in the control of clinical outcomes of periodontal regenerative therapy.     

Clonal nature of odontogenic tumours

Background:  Although clonal origin is an essential step in the comprehension of neoplasias, there have been no studies to examine whether odontogenic tumours are derived from a single somatic progenitor cell. The purpose of this study was to investigate the clonal origin of odontogenic tumours.
Methods:  Fresh samples of seven ameloblastomas, two odontogenic mixomas, two adenomatoid odontogenic tumour, one calcifying odontogenic cyst, one calcifying epithelial odontogenic tumour (CEOT) and six odontogenic keratocyst (OKC) of female patients were included in this study. After DNA extraction, the HUMARA gene polymorphism assay was performed.
Results:  Most of the informative odontogenic lesions studied (12 out of 16) showed a monoclonal pattern. Among the polyclonal cases, two were OKC, one CEOT and one odontogenic mixoma.
Conclusions:  Our results suggest that most odontogenic tumours are monoclonal.     

Immunolocalization of platelet-derived growth factor A and B chains and PDGF-α and β receptors in human gingival wounds

Platelet-derived growth factor (PDGF) is a polypeptide growth factor which has been implicated as a major mitogen involved in wound healing. The PDGF appears to promote periodontal regeneration; however, its distribution in gingival tissues is not known and how it participates in gingival wound healing is unclear. Using highly specific antibodies we have studied the distribution of PDGF A and B chains and α- and β-PDGF receptors in healing human gingival wounds. Wounds were created by making a 0.75 mm deep incision in the papilla of healthy human gingiva and biopsies were obtained from the same site after 8 h and 1, 3, 7, 14 and 21 d. Frozen sections were immunostained with affinity purified antibodies. The results showed that both epithelium and fibrin clot manifested positive immunostaining for anti-PDGF-A and B-chain antibodies. Staining was present in unwounded and wounded epithelia, and in the fibrin clot it appeared to be more intense for the PDGF-A chain. Blood vessels in connective tissue were also positive while other areas were largely negative. No significant staining was detectable in healthy tissues for anti-PDGF-α or -β receptor antibodies. However, the wound site began to manifest positive immunostaining for anti-β-receptor antibody after 3 d of healing, became maximal at 7d, and then decreased. Our data indicate, but do not prove, that gingival epithelium may be a source of PDGF A and B chains and that the A chain may have a more prominent role to play during early stages of healing. Expression of PDGF β-receptor appears later at the wound site, indicating that the PDGF B isomer may regulate later wound healing events.     

Gene transfer and expression of platelet-derived growth factors modulate periodontal cellular activity

Platelet-derived growth factor (PDGF) is a potent stimulator of wound healing. PDGF gene therapy may promote greater periodontal regeneration than local protein application, due to sustained growth factor delivery to the target tissue. This investigation tested the ability of recombinant adenoviruses (rAds) encoding PDGF-A or PDGF-1308 (a PDGF-A dominant-negative mutant that disrupts endogenous PDGF bioactivity) to affect cells derived from the periodontium. Osteoblasts, periodontal ligament fibroblasts, and gingival fibroblasts were transduced with rAds, and gene expression, DNA synthesis, and cell proliferation were evaluated. The results revealed strong message for the PDGF-A gene for 7 days following gene delivery. Ad2/PDGF-A enhanced the mitogenic and proliferative response in all cell types, while Ad2/PDGF-1308 potently inhibited mitogenesis and proliferation. In conclusion, Ad2/PDGF can effectively transduce cells derived from the periodontium and promote biological activity equivalent to PDGF-AA. These studies support the potential use of gene therapy for sustained PDGF release in periodontal tissues.     

Platelet-derived growth factor (PDGF) isoform and PDGF receptor expression in drug-induced gingival overgrowth and hereditary gingival fibrosis

OBJECTIVE: To investigate possible associations between platelet-derived growth factor (PDGF), PDGF receptor expression and macrophages in drug-induced and hereditary gingival overgrowth. MATERIALS AND METHODS: Tissues from patients with drug-induced gingival overgrowth (DIGO) (n = 10) and hereditary gingival fibrosis (n = 10) were studied and compared with 'control' gingiva (n = 10). Expression of PDGF and its alpha and beta receptors was investigated immunohistochemically and by RT-PCR. Macrophages were identified by immunostaining for CD68. RESULTS: PDGF isoforms and receptors were detected in most cells within all specimens. There were no differences in the numbers of macrophages, or fibroblasts expressing PDGF or receptors, between groups. The level of PDGF expression by fibroblasts, determined by absorbance measurements, was similar between groups for PDGF A. Significantly lower levels of total PDGF and the receptors were detected in drug-induced overgrowth compared to those in hereditary fibrosis (P < 0.004) and control specimens (P < 0.034). All specimens expressed mRNA for PDGF A, PDGF B and alpha and beta receptors. CONCLUSIONS: These data do not support a pivotal role for macrophage-derived PDGF B in the pathogenesis of DIGO. They suggest that fibroblasts in drug-induced lesions have a lowered capacity to produce, and respond to, PDGF, a property not shared by fibroblasts associated with hereditary fibrosis.     

Tissue inhibitor of metalloproteinase-2 inhibits ameloblastoma growth in a new mouse xenograft disease model

J Oral Pathol Med (2010) 39 : 94–102
Background:  Ameloblastomas are odontogenic neoplasms characterized by local invasiveness. This study was conducted to develop a new animal model of ameloblastoma and to address the role of tissue inhibitor of metalloproteinase-2 (TIMP-2) and matrix metalloproteinase-2 (MMP-2) in the growth and invasiveness of ameloblastomas.
Method:  Donated fresh human ameloblastoma tissue was finely minced, screened, and subcutaneously implanted in three locations on each of 10 BALB/c-nu/nu nude mice. Newly established tumors on each mouse were injected with: (i) transfection reagent; (ii) liposome and transfection reagent; or (iii) liposome, transfection reagent, and the expression plasmid pcDNA3.1(+)/green fluorescent protein (GFP)-TIMP-2. Tumors were monitored for 5 weeks and excised for histopathology, RNA, and protein analyses.
Results:  The ameloblastoma xenografts were established with high frequency and contained a variety of typical features, validating this new model system. Xenografts injected with the TIMP-2 expression plasmid showed reduced growth, increased TIMP-2 mRNA and protein, and decreased MMP-2 protein compared with the control groups.
Conclusions:  We successfully established a new experimental model of ameloblastoma consisting of subcutaneous human xenografts in nude mice. In addition, we demonstrated the successful introduction of the TIMP-2 gene in tumor xenograft cells in vivo , resulting in xenograft growth inhibition. This growth inhibition may have resulted from TIMP-2 overexpression specifically inhibiting MMP-2 protein expression and activity.     

Immunoexpression of MMPs-1, -2, and -9 in ameloblastoma and odontogenic adenomatoid tumor

Objective:  The aim of this study was to evaluate and compare the expression of metalloproteinases-1, -2, and -9 in solid ameloblastoma and adenomatoid odontogenic tumor.
Methods:  A total of 20 cases of solid ameloblastoma and 10 cases of adenomatoid odontogenic tumors were selected and immunohistochemically assessed. Metalloproteinases-1, -2, and -9 immunoexpression and their distribution pattern were noted and semiquantitatively scored. The scores obtained were statistically analyzed.
Results:  Matrix metalloproteinase (MMP)-1 showed a predominant expression in both tumors and was found in stroma and parenchyma. For MMP-2, there was a varied expression, with 80% and 60% of immunoreactive tumor cells in ameloblastoma and adenomatoid odontogenic tumor respectively. Regarding stromal cells, 65% of ameloblastomas and 80% of adenomatoid odontogenic tumors showed positivity. There was immunoexpression of the MMP-9 in parenchymal and stromal cells in all cases of both tumors analyzed. A statistically significant difference in the expression of MMP-1 in relation to the expression of MMP-2 and -9 in ameloblastomas ( P  < 0.001) was observed.
Conclusion:  The results suggest that these metalloproteinases are related to growth and progression of tumors analyzed, and particularly in ameloblastoma, its highest aggressiveness may be, in part, a result of the active participation of the stromal cells and their products, such as the MMPs studied.     

血小板衍生生长因子对大鼠种植体周围神经再生影响的研究

目的 探讨血小板衍生生长因子（PDGF）对大鼠种植体周围神经再生的影响。方法 建立大鼠股骨植入种植体模型,愈合早期连续注射PDGF,采用免疫组化染色的方法分析PDGF对种植体周围神经再生的影响。结果 PDGF增加大鼠股骨种植体周围早期神经纤维数量,对种植体周围后期神经纤维数量无显著影响。同时,这些神经具有周围神经纤维的典型结构。结论 PDGF可以促进种植体周围早期神经再生。本研究为实现PDGF促进种植体周围神经再生,进而改善种植体感觉功能的临床应用,提供一定的实验依据。     

血小板衍生生长因子对大鼠种植体周围神经再生影响的研究

目的 探讨血小板衍生生长因子（PDGF）对大鼠种植体周围神经再生的影响。方法 建立大鼠股骨植入种植体模型,愈合早期连续注射PDGF,采用免疫组化染色的方法分析PDGF对种植体周围神经再生的影响。结果 PDGF增加大鼠股骨种植体周围早期神经纤维数量,对种植体周围后期神经纤维数量无显著影响。同时,这些神经具有周围神经纤维的典型结构。结论 PDGF可以促进种植体周围早期神经再生。本研究为实现PDGF促进种植体周围神经再生,进而改善种植体感觉功能的临床应用,提供一定的实验依据。     

联合VEGF-165和PDGF-BB促进骨髓间充质干细胞血管化的体内研究

目的研究在血管生成早期联合应用血管内皮生长因子-165(VEGF-165)与血小板衍生生长因子-BB(PDGF-BB)对血管新生的影响。方法选取40只雄性成年SD大鼠,随机分为4组,每组10只。实验组将生长因子加入骨髓干细胞膜片,培养24 h后回植入动物体内,包括VEGF-165组(V组)、PDGF-BB组(P组)、VEGF-165+PDGF-BB组(V+P组)。对照组不加生长因子仅回植细胞膜片。分别于植入后2周和4周回收标本,利用RT-PCR法检测成血管相关基因的表达水平及利用Image pro软件对HE染色后的组织切片进行血管的管腔面积及血管数量的计算,以此来评估VEGF-165和PDGF-BB对新血管形成的影响。结果术后2周和4周V组血管的管腔面积明显大于其他3组。P组、V+P组和对照组血管的管腔面积相似。V+P组血管数量明显多于对照组,而V组和P组血管数量仅稍高于对照组。术后2周及4周V+P组基因表达量较V组及P组更加明显地上调,对照组未见明显的表达上调。结论 VEGF-165与PDGF-BB联合作用于骨髓间充质干细胞存在协同作用,有效促进新血管的生成,有助于组织工程骨的血管化。     

Porphyromonas gingivalis lipopolysaccharide modulates the responsiveness of human periodontal ligament fibroblasts to platelet-derived growth factor

Lipopolysaccharides (LPS) prepared from periodontopathic bacteria have been known to induce various biological responses which may lead to periodontal tissue breakdown. The purpose of this study was to determine if Porphyromonas gingivalis LPS could affect cellular functions of human periodontal ligament fibroblasts (HPLF). We showed here the responsiveness of cultured HPLF to platelet-derived growth factor (PDGF)-BB, a growth factor for mesenchymal cells, in the presence of P. gingivalis LPS. DNA synthesis of HPLF was enhanced in a dose-dependent manner when LPS were co-incubated for 48 h; thereafter, it decreased to the baseline level within 24 h incubation. The stimulating effect of PDGF-BB was further enhanced by the pretreatment of HPLF with LPS (10 μg/ml) for 48 h. The binding assay of [¹²⁵I] PDGF-BB and the flow cytometric assay using rabbit antiserum to human PDGF receptor (PDGF-R) β-type indicated that this enhancement was due to the increase of the number of PDGF-R β-type on HPLF. Immunoprecipitation using antiserum to human PDGF-R β-type also showed that the synthesis of PDGF-R β-type was augmented in the LPS-treated HPLF. These results indicate that P. gingivalis LPS stimulate cellular proliferation and responsiveness to PDGF-BB of cultured HPLF. These cellular reactions may be mediated by PDGF-BB binding, followed by increased synthesis of the receptor protein.     

血小板衍化牛长因子对人牙髓成纤维细胞DNA和胶原蛋白合成的影响

目的：观察血小板衍化生长因子（platelet-derived growth factor,PDGF）对人牙髓成纤维细胞（human dental pulp fibroblast,HDPF）DNA合成和胶原蛋白合成的影响。方法：应用^3H-TdR和^3H-脯氨酸掺入方法，观察PDGF对体外培养的HDPF DNA合成和胶原蛋白合成的情况。结果：20-60ng/mL PDGF可明显促进HDPF DNA的合成，40ng/mL浓度使细胞DNA合成在36h达最大值；对细胞的胶原蛋白合成无明显促进作用。结论：PDGF明显促进HDPF DNA的合成，可能在治疗牙髓病中起重要作用。     

Expression and alterations of the PTEN / AKT / mTOR pathway in ameloblastomas

Objectives:  Recently, an allelic loss of phosphatase and tensin homologue (PTEN) was shown to occur in ameloblastomas. In carcinogenesis, loss of PTEN allows for overactivity of the phosphatidylinositol-3-kinase/protein kinase B (PI3K / AKT) pathway inducing an upregulation of mammalian-target of rapamycin (mTOR) and its downstream effector ribosomal-subunit-6 kinase (S6K); allowing for uncontrolled cell proliferation, apoptosis inhibition and cell cycle deregulation.
Methods:  Thirty ameloblastomas and five dental follicles were studied, looking at the immunohistochemical expression of total PTEN and AKT, as well as their phosphorylated (p) active forms, and the downstream effector and indicator of mTOR activity p70 ribosomal-subunit-6 kinase (pS6K). Also assessed was the expression of extracellular-signal-regulated kinase (ERK), which cross talks with AKT.
Results:  Total PTEN was absent in 33.3% of ameloblastomas, while its stabilized, phosphorylated^{ser380 / thr382 / thr383} form was absent in 83.3% of tumors. In contrast, AKT was expressed in 83.3% of ameloblastomas, showing high expression of the p-thr³⁰⁸AKT and p-ser⁴⁷³ AKT forms in 93.3% and 56.6% of cases, respectively. Further, the mTOR activated pS6K^{ser240 / 244} was detected in 86.7% of ameloblastomas, while ERK was overexpressed in 70.0% of the cases.
Conclusion:  Immunohistochemical analysis of aberrant signaling in the PI3K/AKT/mTOR pathway in ameloblastomas may represent a valuable tool for elucidating pathogenesis, aggressiveness and selecting optimal therapeutics.     

Expression of keratinocyte growth factor and its receptor in odontogenic keratocysts

Background:  The mitotic activity of the epithelial cells of odontogenic keratocysts (OKCs) is greater than that of other odontogenic jaw cysts, and the mitotic activity of the epithelial cells decreases after marsupialization. Keratinocyte growth factor (KGF) interacts with its specific receptor (KGFR), and elicits the proliferation and/or differentiation of the various types of epithelial cells. The aim of this study was to investigate the expression of KGF/KGFR in OKCs before and after marsupialization.
Methods:  The expression of KGF was immunohistochemically detected in the specimens of 16 OKCs and 11 dentigerous cysts before and after marsupialization. The expression of KGF mRNA was measured in the fibroblasts isolated from OKCs by real-time PCR.
Results:  KGF was expressed in the epithelial cells and fibroblasts of 12 and seven of 16 OKC specimens, respectively. The intensity of the KGF expression in both the epithelial cells and the fibroblasts significantly decreased after marsupialization. KGFR was expressed throughout the epithelium in 15 of 16 OKC specimens, but the intensity of the KGFR expression did not change after marsupialization. The expression of KGF was detected in the epithelium of two of 11 dentigerous cyst specimens, but not in the fibroblasts before marsupialization. Real-time PCR revealed that recombinant human interleukin (IL)-1α increased the expression of KGF mRNA in the fibroblasts isolated from OKCs.
Conclusion:  KGF/KGFR signaling may play a crucial role in the epithelial cells of OKCs. Furthermore, the expression of KGF in the fibroblasts of OKCs is regulated by IL-1α.