Are we on the brink of nonsurgical treatment for ameloblastoma?

Objective: Recent identification of altered molecular signaling pathways in neoplasia has begun to elucidate mechanisms of oncogenesis, differentiation, and tumor progression, and to suggest plausible nonsurgical considerations for treatment. Here we review the sonic hedgehog (SHH) and PI3K/Akt/mTOR signaling pathways, their role in ameloblastoma, a locally aggressive odontogenic tumor, and evidence for consideration of therapeutic approaches that target these molecular pathways. In so doing, some of the gaps will be revealed that may impel investigations and translate to patient care, helping to minimize or eliminate the need for extensive surgery. Study design: This is a comprehensive review of the literature regarding alterations in signaling mechanisms associated with ameloblastomas. In addition, this review attempts to explore and discuss possible inhibitors to these pathways that may have utility in treating ameloblastoma. Results: The expression of SHH signaling molecules in ameloblastomas at the mRNA and protein levels has intimated that these molecules may play a role in cell proliferation of these tumors. Immunohistochemical analysis has revealed aberrant signaling in the PI3K/Akt/mTOR pathway in ameloblastomas and appears to be a valuable tool for elucidating pathogenesis and aggressiveness, and selecting optimal therapeutics. Conclusion: The understanding of altered pathways in ameloblastoma may soon provide nonsurgical options for the treatment of this condition. The demonstration of cross talk in SHH signal transduction with PI3K signaling through Akt has shown that these pathways converge to control the Gli transcription factors. Thus, tumors that entirely depend on active SHH signaling for survival/growth and maintenance may well be susceptible targets for combined chemotherapy with SHH-specific inhibitors together with PI3K, Akt, or mTOR blocking agents. Some of these inhibitors could be used locally, thereby minimizing major systemic effects. © 2010 Mosby, Inc. All rights reserved

Survivin is a downstream target and effector of sulindac-sensitive oncogenic Stat3 signalling in head and neck cancer

Sulindac exerts its antitumourigenic effects in oral squamous cell carcinoma (SCC) cells by modulating survivin in a Stat3-dependent manner. Immunohistochemistry was used to detect the protein levels of phosphorylated-tyrosine Stat3 (p-tyr Stat3) and survivin in SCC tissues. Western blot, reverse transcriptase polymerase chain reaction, Annexin-V and cell proliferation assays were used to determine p-tyr Stat3 and survivin protein and mRNA expression, and cell viability following treatment with cyclooxygenase (COX) inhibitors, Stat3 siRNA, or the forced expression of Stat3 or survivin. Immunohistochemical analysis revealed an overexpression of p-tyr Stat3 in T1 SCCs. The importance of constitutive Stat3 activation in tumourigenesis was confirmed by siRNA inhibition of Stat3, resulting in cell growth inhibition and apoptosis, via a downregulation of survivin mRNA and protein expression. The forced expression of survivin partially reversed these effects of Stat3 inhibition. Sulindac, but not other COX inhibitors, downregulated Stat3, which correlated to an inhibition of cell proliferation, survival and survivin expression. Transfection of constitutively active Stat3 restored survivin expression and partially rescued SCC cells from sulindac-induced antitumourigenic effects. These data indicate that survivin is a downstream target and effector of oncogenic Stat3 signalling in SCC, which is targeted by sulindac in a COX-2-independent manner. © 2007 International Association of Oral and Maxillofacial Surgeons

The role of apoptosis in oral disease: Mechanisms; aberrations in neoplastic, autoimmune, infectious, hematologic, and developmental diseases; And therapeutic opportunities

Apoptosis is a genetically programmed form of cell death, which primarily functions to eliminate senescent or altered cells that are useless or harmful for the multicellular organism. Contrary to necrosis, apoptosis represents a physiologic cellular mechanism, normal function and control of which are critical for the development and homeostasis of multicellular organisms. In contrast, aberrations of the apoptotic mechanisms that cause excessive or deficient programmed cell death have been linked to a wide array of pathologic conditions. This review briefly summarizes the major apoptotic pathways and molecules and presents the most important oral diseases that are related to dysregulation of apoptosis. Knowledge of the association between aberrations in apoptotic mechanisms and human pathology hopefully will be implemented for the design of improved diagnostic and prognostic assays and the development of novel, more efficient, therapeutic strategies

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, phosphorylatedser380/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 pS6Kser240/244 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. © 2007 The Authors

The oncogenic effects of constitutive Stat3 signaling in salivary gland cancer cells are mediated by survivin and modulated by the NSAID sulindac

Objective: Constitutive activation of the signal transducer and activator of transcription 3 (Stat3) has been detected in various human cancers and has been linked to tumor development and progression. Oncogenic Stat3 signaling results in induction of specific target genes, among which survivin is implicated in the proliferation and survival of cancer cells. Targeting of Stat3 constitutive expression by the nonsteroidal antiinflammatory drug (NSAID) sulindac has been demonstrated to exert antineoplastic effects in oral squamous cell carcinoma cells in vitro and in vivo. Study design: The expression and functional role of Stat3 and survivin was evaluated in 2 salivary gland adenocarcinoma cell lines (HSY and HSG). In addition, the effects of the NSAID sulindac and other cyclooxygenase (COX) inhibitors on Stat3 and survivin expression and on cell proliferation and apoptosis of HSY and HSG cells were analyzed. Results: Messenger RNA and protein expression of Stat3 and survivin was detected in HSY and HSG cell lines. Treatment of these cells with siRNA against Stat3 or survivin inhibited cell proliferation and induced apoptosis. Moreover, Stat3 siRNA treatment down-regulated the protein and mRNA expression of survivin, and survivin forced expression partially reversed the antineoplastic effects of Stat3 siRNA treatment. Treatment of HSY and HSG cells with the NSAID sulindac, but not other COX inhibitors, induced significant decreases in cell proliferation and increases in apoptosis, accompanied by down-regulation of Stat3 and survivin expression. In contrast, survivin forced expression or transfection with constitutively active Stat3 attenuated the effects of sulindac on cell growth and apoptosis. Conclusions: Taken together, these data support the importance of the constitutive Stat3 signaling for growth and survival of salivary gland cancer cells through the induction of survivin. Inhibition of the oncogenic Stat3-survivin pathway in these cells can be achieved by selective targeting techniques or treatment with the NSAID sulindac and holds promise for the treatment of salivary gland cancer. © 2009 Mosby, Inc. All rights reserved

Immunohistochemical evaluation of cell proliferation antigen Ki-67 and apoptosis-related proteins Bcl-2 and caspase-3 in oral granular cell tumor

Purpose. We sought to evaluate the cell proliferation activity and immunohistochemical expression of proteins that promote or inhibit apoptosis in oral granular cell tumor (GCT). Study design. Immunohistochemistry for Ki-67, a cell proliferation marker; Bcl-2, an anti-apoptotic protein; and caspase-3, a protein implicated in the execution of apoptosis, was performed on tissues from 12 patients with GCT of the tongue. Results. Nuclear immunostaining for Ki-67 was observed only in isolated GCs (less than 2%). All patients exhibited cytoplasmic immunoreactivity for Bcl-2 in the majority of tumor cells. Cytoplasmic staining for caspase-3 was also present in more than 50% of GCs in all tumors. Conclusions. GCT cells display low proliferation activity, a finding possibly related to their benign behavior. Caspase-3 expression suggests activation of the apoptotic cascade in the GCs, but persistence of the cells in the tissues could be attributed to the expression of Bcl-2 protein, a molecule that functions as a survival factor

Sulindac induces apoptosis and inhibits tumor growth in vivo in head and neck squamous cell carcinoma

Sulindac has antineoplastic effects on various cancer cell lines; consequently, we assessed sulindac's effects on laryngeal squamous cell carcinoma (SCC) cells in vitro and in vivo. In vitro, SCC (HEP-2) cells treated with various cyclooxygenase inhibitors or transfected with constitutively active signal transducer and activator of transcription 3 (Stat3) or survivin vectors were analyzed using Western blot analysis, annexin V assay, and cell proliferation assay. In parallel, nude mice injected subcutaneously with HEP-2 cells were either treated intraperitoneally with sulindac or left untreated, and analyzed for tumor weight, survivin expression, and tyrosine-phosphorylated Stat3 expression. In vitro studies confirmed the selective antiproliferative and proapoptotic effects of sulindac, which also downregulated Stat3 and survivin protein expression. Stat3 or survivin forced expression partially rescued the antiproliferative effects of sulindac. In vivo studies showed significant repression of HEP-2 xenograft growth in sulindactreated mice versus controls, with near-complete resolution at 10 days. Additionally, tumor specimens treated with sulindac showed downregulation of phosphorylated tyrosine-705 Stat3 and survivin expression. Taken together, our data suggest, for the first time, a specific inhibitory effect of sulindac on tumor growth and survivin expression in laryngeal cancer, both in vitro and in vivo, in a Stat3-dependent manner, suggesting a novel therapeutic approach to head and neck cancer. Copyright © 2007 Neoplasia Press, Inc. All rights reserved

Immunohistochemical expression of the oncogenic molecules active Stat3 and survivin in benign and malignant salivary gland tumors

Objective: Signal transducer and activator of transcription 3 (Stat3) and survivin have been shown to exert oncogenic effects in various human neoplasms. The purpose of this study was to evaluate the expression of tyrosine phosphorylated (active) Stat3 and survivin in various benign and malignant salivary gland tumors (SGTs). Study design: Eighty-six SGTs (65 malignant and 21 benign tumors of various histopathologic subtypes) were immunohistochemically stained with antisurvivin or anti-phosphorylated tyrosine-705 (p-tyr) Stat3 antibodies. Immunohistochemical reactivity was graded in a semiquantitative manner; a combined score of immunohistochemical positivity (0-6) was calculated for each tumor by adding the individual scores for percentage of tumor cells (0-3) and intensity of staining (0-3). Results: Survivin was immunohistochemically detected in all studied benign and malignant SGTs; p-tyr Stat3 was also detected in the majority (91%) of SGTs. The average combined scores for survivin and p-tyr Stat3 immunohistochemical expression in the studied malignant SGTs was 4.40 and 3.35, respectively; the corresponding combined scores for survivin and p-tyr Stat3 in the studied benign SGTs were 4.37 and 3.22, respectively. No statistically significant differences (P > .05) in p-tyr Stat3 or survivin expression were detected between the benign and malignant groups, or among the various examined histopathologic subtypes of SGTs. In contrast, normal salivary gland tissues revealed only weak and focal survivin or p-tyr Stat3 immunoreactivity, mainly localized to ductal and mucous cells. Conclusions: Our data indicate an almost universal expression of activated Stat3 and survivin in benign and malignant SGTs. Considering the well established proliferative and antiapoptotic properties of these molecules and their functional interrelationship, selective targeting techniques against Stat3 and/or survivin may represent promising therapeutic strategies against neoplasms of salivary gland origin. © 2009 Mosby, Inc. All rights reserved

Sec61alpha synthesis is enhanced during translocation of nascent chains of collagen type IV in F9 teratocarcinoma cells after retinoic acid treatment

Nascent procollagen peptides and other secretory proteins are transported across the endoplasmic reticulum (ER) membrane through a protein-conducting channel called translocon. Sec61alpha, a multispanning membrane translocon protein, has been implicated as being essential for translocation of polypeptide chains into the cisterns of the ER. Sec61alpha forms a protein complex with collagen and Hsp47, an ER-resident heat shock protein that binds specifically to collagen. However, it is not known whether Sec61alpha is ubiquitously produced in collagen-producing F9 teratocarcinoma cells or under heat shock treatment. Furthermore, the production and utilization of Sec61alpha may depend on the stage of cell differentiation. Cultured F9 teratocarcinoma cells are capable of differentiation in response to low concentrations of retinoic acid. This differentiation results in loss of tumorigenicity. Mouse F9 cells were grown in culture medium at 37ºC and 43ºC (heat shock treatment) treated or not with retinoic acid, and labeled in certain instances with 35S-methionine. Membrane-bound polysomes of procollagen IV were then isolated. Immunoprecipitation and Western blot analysis were performed using polyclonal antibodies against collagen IV, Hsp47 and Sec61alpha. Under retinoic acid-untreated conditions, F9 cells produced undetectable amounts of Sec61alpha. Sec61alpha, Hsp47 and type IV collagen levels were increased after retinoic acid treatment. Heat shock treatment did not alter Sec61alpha levels, suggesting that Sec61alpha production is probably not affected by heat shock. These data indicate that the enhanced production of Sec61alpha in retinoic acid-induced F9 teratocarcinoma cells parallels the increased synthesis of Hsp47 and collagen type IV