Osteopontin contributes to hepatocyte growth factor-induced tumor growth and metastasis formation.

The cytokine hepatocyte growth factor (HGF)/scatter factor-1 and its cognate receptor, Met, are involved in the etiology and progression of many types of cancer. Despite recent advances in understanding the signal transduction pathways activated by HGF, the mechanism by which HGF exerts its tumorigenic effect is not well understood. To identify proteins that may be involved in mediating HGF-induced cell motility, invasiveness, and tumorigenesis, we used two separate differential display screening methods to identify changes in gene expression that are initiated by HGF in an epithelial cell culture system. Among several known and unknown genes whose expression was modified, osteopontin (OPN), a protein previously associated with tumorigenesis, was found to be upregulated within 6 h following HGF stimulation. OPN expression was dependent on activation of the PI-3 kinase pathway. Autocrine secretion of HGF resulted in sustained expression of OPN. Downregulation of opn expression by stable antisense transfection attenuated OPN expression and repressed HGF-induced invasiveness in vitro and decreased HGF-mediated tumor growth and metastasis formation in vivo. Constitutive expression of OPN in itself exerted partial invasiveness in vitro, but its expression itself was not sufficient to initiate tumor growth or metastasis formation in vivo. Thus, together with other molecules, OPN activity contributes to HGF-induced tumor growth and invasiveness.

Overexpression of p53 in squamous cell carcinoma of the tongue in young patients with no known risk factors is not associated with mutations in exons 5-9.

BACKGROUND: This study investigated the status of the p53 tumor suppressor gene in patients less than 40 years of age who had squamous cell carcinoma of the tongue develop with no known risk factors. METHODS: Histologic sections from 21 patients were prepared from formalin-fixed, paraffin-embedded tissue and were processed for standard immunohistochemistry for detection of the p53 protein. In addition, tumors were evaluated by single-strand conformation polymorphism and by DNA sequencing to identify potential mutations in the conserved exons (5-9) of the p53 gene. RESULTS: Eighty-one percent (17 of 21) of the patients overexpressed p53 by immunohistochemical analysis. However, none of these patients demonstrated mutations in exons 5-9 of the gene. CONCLUSIONS: These data suggest that the molecular mechanisms by which the young individuals with no risk factors had altered p53 function in oral squamous cell carcinoma may differ from those of the more typical population of individuals who have this malignancy develop.

The angiogenic switch in hamster buccal pouch keratinocytes is dependent on TGFbeta-1 and is unaffected by ras activation.

This study was undertaken to investigate the mechanisms by which Syrian hamster buccal pouch keratinocytes treated in vivo with 7,12-dimethylbenz[a]anthracene (DMBA), switch from an angio-inhibitory to an angiogenic phenotype. Cells were cultured from pouches at various times after exposure to carcinogen and their angiogenic activity assessed. The angio-inhibitory activity present in conditioned media from normal cells was lost as early as 3 weeks after carcinogen treatment, resulting in weak expression of angiogenic activity. By 5 weeks, cells had become strongly angiogenic due to the secretion of high levels of TGFbeta-1, a potent angiogenic factor. Because the switch to high levels of secreted TGFbeta-1 occurred at the same time as the activation of the H-ras oncogene, non-angiogenic cell lines lacking an activated H-ras oncogene were stably transfected with mutant H-ras and their transformed and angiogenic phenotypes were evaluated. Although ras transfection drove two of the three cultured cell lines to anchorage independence and modestly increased their ability to clone in low serum, it had no effect on the angiogenic phenotype or on the level of secreted active TGFbeta-1. These results demonstrate that the angiogenic phenotype in the hamster buccal pouch model of oral carcinogenesis develops in a step-wise fashion with an early decrease in the production of an inhibitor of angiogenesis and a subsequent marked increase in the secretion of the inducer TGFbeta-1. Although the activation of the H-ras oncogene contributed to anchorage independence, it did not affect the expression of the angiogenic phenotype in this model system.

MTS1 gene mutations in archival oral squamous cell carcinomas.

Multiple tumor suppressor gene 1 (MTS1) has been found mutated or deleted in a variety of human cancers. Our purpose was to identify and characterize MTS1 gene mutations in primary oral squamous cell carcinomas (SCCs) in each of the three exons of the MTS1 gene. Seventeen archival samples of oral SCC were evaluated for the presence of MTS1 mutations using single strand conformation polymorphism (SSCP) and DNA sequencing. Three of 17 tumors exhibited MTS1 gene mutations: one tumor exhibited a mutation in exon 2 and two tumors exhibited mutations at the splice site junction of intron 2 and exon 3. Three tumors also exhibited a common base change in the 3' untranslated region of exon 3, which is interpreted as a likely polymorphic variant. An examination of the three tumors exhibiting MTS1 point mutations revealed no unique characteristics relative to p53 immunohistochemical activity, mitotic frequency, or degree of histologic differentiation. This study indicates that MTS1 gene mutations may be involved in at least a minor proportion of oral SCCs.

Captopril inhibits angiogenesis and slows the growth of experimental tumors in rats.

Captopril, an inhibitor of angiotensin converting enzyme, is widely used clinically to manage hypertension and congestive heart failure. Here captopril is shown to be an inhibitor of angiogenesis able to block neovascularization induced in the rat cornea. Captopril acted directly and specifically on capillary endothelial cells, inhibiting their chemotaxis with a biphasic dose-response curve showing an initial decrease at clinically achievable doses under 10 microM and a further slow decline in the millimolar range. Captopril inhibition of endothelial cell migration was not mediated by angiotensin converting enzyme inhibition, but was suppressed by zinc. Direct inhibition by captopril of zinc-dependent endothelial cell-derived 72-and 92-kD metalloproteinases known to be essential for angiogenesis was also seen. When used systemically on rats captopril inhibited corneal neovascularization and showed the antitumor activity expected of an inhibitor of angiogenesis, decreasing the number of mitoses present in carcinogen-induced foci of preneoplastic liver cells and slowing the growth rate of an experimental fibrosarcoma whose cells were resistant to captopril in vitro. These data define this widely used drug as a new inhibitor of neovascularization and raise the possibility that patients on long term captopril therapy may derive unexpected benefits from its antiangiogenic activities.

Myofibromas of the oral cavity.

Solitary infantile myofibromatosis or myofibroma of the oral cavity is an uncommon condition with only 32 reported cases in the English-language literature. This article presents four additional cases of these solitary myofibroblastic lesions. In addition, the clinical and histologic features of this uncommon spindle cell neoplasm have been reviewed. The similarity in both the clinical and histopathologic features of the "adult" and "infantile" lesions support the proposal that myofibroma is a more accurate and acceptable term for these solitary myofibroblastic lesions of the oral cavity.

Unusual presentation of a chondromyxoid fibroma of the mandible. Report of a case and review of the literature.

Chondromyxoid fibromas are uncommon central bone tumors that are most often found at the proximal metaphyses of long bones. Chrondromyxoid fibromas of the jaws are very rare with only 18 reported cases in the literature. This article reports on a recurrent chondromyxoid fibromas of the mandible in a 10-year-old boy. In addition, a literature review of the clinical and histologic features, as well as the diagnostic pitfalls and recommended modalities of treatment are presented.

Anticarcinogenic action of diallyl sulfide in hamster buccal pouch and forestomach.

The anticarcinogenic action of the garlic constituent diallyl sulfide (DAS), was examined in the hamster buccal pouch and forestomach. Groups of hamsters were topically treated, for up to 14 weeks, with a 0.5% solution of the buccal pouch and forestomach carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Prior to, during and after DMBA treatment, groups of hamsters were also treated, on alternate days, with a 1% solution of DAS. In addition to tumor formation, the induction of gamma-glutamyl transpeptidase (gamma GT) buccal pouch epithelial lesions served as an additional presumptive index of in vivo carcinogenesis/anticarcinogenesis. DAS resulted in a significant reduction in buccal pouch tumor frequency, buccal pouch tumor burden, buccal pouch gamma GT lesion frequency and forestomach tumor frequency. In a separate experiment, DAS also reduced the level of autoradiographically quantified unscheduled DNA repair synthesis (UDS) in pieces of hamster buccal pouch concurrently exposed in vitro to the potent buccal pouch carcinogen N-methyl-N-benzylnitrosamine (MBN). This study demonstrates that DAS is an effective anticarcinogenic agent in squamous mucosa of the hamster and suggests novel cost-effective strategies for the rapid identification of tissue-specific anticarcinogens and a quantitative assessment of their efficacy.

The pathogenesis, oral manifestations, and implications for dentistry of metabolic bone disease.

Metabolic bone diseases often result in striking oral manifestations that can lead to a diagnosis of the underlying systemic condition. Numerous studies suggest that subclinical derangements in calcium homeostasis and bone metabolism may also contribute to alveolar ridge resorption and periodontal bone loss in predisposed individuals. The significance of this spectrum of diseases and their overall impact on oral health and dental management are likely to increase as the elderly segment of the population increases in the coming decades.

Resistant keratinocytes in 7,12-dimethylbenz[a]anthracene-initiated hamster buccal pouch epithelium.

In order to test the hypothesis that the property of resistance to cytotoxicity is an acquired trait of premalignant oral mucosal epithelium, cell dissociates were prepared from in vivo initiated hamster buccal pouch epithelium (HBPE), non-initiated HBPE and malignant HBPE cell lines. These cell types were evaluated for resistance to the cytotoxic effects of the inducing carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA). A mitoinhibition assay and a clonogenicity assay were used to assess the ability of these cells to replicate or form colonies in the presence of 40 microM DMBA. Replication of primary plated HBPE cells was inhibited by 100% in both assays. PO II, a cell line derived from non-initiated, paraffin-oil-exposed HBPE, was inhibited by 97 and 100% in the mitoinhibition and colony-forming assays respectively. This same cell line, like primary plated HBPE, lacked the transformation-linked traits of angiogenesis and anchorage-independent growth. By contrast, three malignant HBPE cell lines, two derived during long-term culture of DMBA-initiated HBPE, and one from a DMBA-induced HBPE carcinoma, were inhibited by only 34% or less in the assays for resistance to cytotoxicity. Primary cell cultures derived from HBPE initiated in vivo with twice-weekly topical applications of a 0.5% solution of DMBA in paraffin oil, for 3 or 5 weeks, were inhibited to an intermediate degree, indicating the presence of DMBA-resistant cells. In addition, DMBA-resistant cell colonies were observed in cell cultures prepared at 2, 6 and 10 weeks after completing the 5 week initiation regimen. Progenitors of the resistant cells, persisting in vivo for several weeks after initiation, may represent early preneoplastic cell populations in this experimental model.

Acute inhibition of DNA synthesis in hamster buccal pouch epithelium exposed to indirect acting carcinogens.

Inhibition of DNA synthesis was observed and quantitated in hamster buccal pouch epithelium exposed in vivo and in vitro to indirect acting carcinogens. Topical application of a 0.5% solution of the potent hamster buccal pouch carcinogen 7,12-dimethylbenz[a]-anthracene (DMBA) acutely inhibited epithelial DNA synthesis by 40-65%, as indicated by a decrease in [3H]thymidine incorporation over a period of 24 h. When applied twice at a concentration of 2%, N-methyl-N-benzylnitrosamine (MBN), another potent buccal pouch carcinogen, inhibited epithelial DNA synthesis by 76% within a period of 4 h. A similar acute inhibitory effect on DNA synthesis was observed when explants of buccal pouch mucosa, exhibiting continuous cell replication, were exposed in vitro in the presence of MBN or DMBA for periods up to 12 and 24 h, respectively. The inhibitory effect of DMBA was greater than that of other polycyclic aromatic hydrocarbons of lesser carcinogenic potency in this tissue. This study demonstrates that the metabolic activation of indirect acting carcinogens leading to acute cytotoxicity and inhibition of DNA synthesis occurs rapidly in hamster buccal pouch mucosa exposed to these agents in vitro as well as in vivo. The experimental imposition of an acute inhibitory pressure, applied as demonstrated in this report, may enable the detection of precancerous cells which have acquired the property of resistance to this cytotoxic effect in the course of carcinogenesis. In principle, the in vitro approach, coupled with autoradiography, may be useful in identifying microscopic foci of resistant preneoplastic cells in samples of human oral mucosa. 24R01 34160

Sequential loss of suppressor genes for three specific functions during in vivo carcinogenesis.

As normal cells undergo neoplastic transformation, multiple suppressor gene functions are lost or inactivated. However, the relative contribution that individual suppressor gene defects play in the sequential evolution of solid tumors has not yet been evaluated in a readily analyzable experimental model of carcinogenesis. The present study was undertaken to: (a) document the loss of suppressor genes implicated in the control of angiogenic activity, anchorage and serum growth requirements, and proliferative life span, in populations of hamster buccal pouch (HBP) keratinocytes (Kr) initiated in vivo with the chemical carcinogen 7,12 dimethylbenz(a)anthracene and (b), to determine what combination of defective suppressor genes are necessary for tumorigenesis. Kr were isolated from HBPs at various times after treating the mucosal surfaces in vivo with 7,12 dimethylbenz(a)anthracene. Cells or their conditioned culture media were evaluated for: (a) angiogenic activity in vivo and in vitro, (b) anchorage independent growth, (c) growth in low serum, (d) immortality, and (e) tumorigenicity. Angiogenic activity and immortality were the first two phenotypes detected with anchorage independence and tumorigenesis emerging late in the carcinogenic process. Hybrids generated between Kr which were angiogenic, but otherwise negative for all other phenotypic traits, and a transformed and tumorigenic HBP carcinoma cell line, E1-1, were suppressed for all phenotypes except angiogenic activity and none of the hybrids were tumorigenic. In contrast, Kr positive for angiogenic activity, anchorage independence, immortality, and tumorigenicity and hybrids generated between these cells and E1-1 carcinoma, were tumorigenic. However, hybrids between a nontumorigenic, anchorage independent, immortal but nonangiogenic Kr, and the E1-1 line were not tumorigenic. These results suggest that (a) angiogenic activity is an early phenotypic trait that emerges as a result of the loss of a suppressor gene function and (b) loss of this function is essential but not sufficient for the development of HBP tumors.

Sequential expression and cooperative interaction of c-Ha-ras and c-erbB genes in in vivo chemical carcinogenesis.

The level of expression of several cellular protooncogenes is examined at different stages of 7,12-dimethylbenzanthracene (DMBA)-induced tumor development in hamster buccal pouch epithelium (HBPE). Results presented demonstrate overexpression of c-Ha-ras gene at a very early stage of tumor development, and this elevated level of expression of the gene persists throughout the tumorigenesis process. The expression of the cellular protooncogene c-erbB, on the other hand, can be detected only after 8-10 weeks of DMBA treatment of the tissue and increases with the progression of the disease. The overexpression of c-erbB gene can be correlated with the stage of extensive proliferation and subsequent invasion of the HBPE cells into the underlying connective tissue. This sequential pattern of stage-specific expression of the two cellular protooncogenes can be observed in (i) treated tissues, (ii) stage-representative cultured cells, and (iii) NIH 3T3 transformants derived with DNA from HBPE cells. The low-level expression of c-myc and c-sis genes detected in control tissues remains unaffected, while c-fos gene activity cannot be detected at any stage of tumor development. The overexpression of c-Ha-ras gene alone in HBPE cells derived from tissues treated for 5 weeks (DM5) is not sufficient to induce tumors in athymic mice, whereas expression of c-Ha-ras and c-erbB genes at later stages of tumor development (DM10 and HCPC cells) induce histopathologically defined epithelial cell carcinoma in athymic mice within 2-3 weeks. The sequential overexpression of c-Ha-ras and c-erbB genes in a stage-specific manner and their cooperative interaction in the DMBA-induced in vivo oral carcinogenesis have been demonstrated.

Early neoplastic commitment of hamster buccal pouch epithelium exposed biweekly to 7,12-dimethylbenz[a]anthracene.

Experiments were performed to determine the rate at which hamster buccal pouch epithelium (HBPE) is committed to neoplastic development during a regimen of biweekly topical applications of 7,12-dimethylbenz[a]anthracene (DMBA) in mineral oil, administered for 1, 2, 3, 5 or 10 weeks. Evaluated indices of neoplastic commitment were: (i) primary tumor formation, (ii) passageability of HBPE cells in surface culture, (iii) anchorage-independent growth in soft agar and (iv) induction of the transformed phenotype in NIH3T3 cells following transfection with HBPE DNA. Groups of 12-15 hamsters, exposed to DMBA for 1, 2 and 3 weeks, developed buccal pouch tumor incidences of 13%, 42% and 71% respectively within 44 weeks. Buccal pouches of ten control hamsters treated for three weeks with mineral oil did not develop buccal pouch neoplasms during an observation period of 44 weeks. Whereas cultured HBPE cells obtained following three weeks of in vivo DMBA exposure were negative in assays for anchorage-independent growth, passageability in surface culture and induction of NIH3T3 transformants following DNA transfection, similarly cultured cells obtained following five and ten weeks of in vivo exposure were positive, or marginally positive, in each of these assays. These results indicate that (i) the regimen of biweekly DMBA applications commits HBPE to neoplastic development within three weeks and that (ii) subsequent cellular or molecular changes occurring during greater than or equal to 2 succeeding weeks of DMBA treatment are necessary to manifest the transformation associated phenotypes of continuous passageability, anchorage-independent growth, and induction of NIH3T3 transformants following DNA transfection.

Control of angiogenic activity in carcinogen-initiated and neoplastic hamster pouch keratinocytes and their hybrid cells.

This study was undertaken to test the hypothesis that deregulated expression of the angiogenic phenotype by tumor cells is due to loss or inactivation of an angiogenesis suppressor gene(s). We used the technique of somatic cell hybridization to test the ability of untreated or chemical carcinogen-initiated hamster pouch keratinocytes, when fused to squamous epithelial neoplasms, to suppress tumor angiogenic activity by assaying hybrid-conditioned media (CM) in the avascular cornea of rat eyes. A non-angiogenic keratinocyte line, CL-2, derived from cultures of untreated epithelium and 3 lines of carcinogen-initiated keratinocytes, PN3, 5, and 7, of varying angiogenic potential were fused, using polyethylene glycol, to 3 tumorigenic, potently angiogenic, drug-resistant, hamster pouch carcinomas cell lines: HCPC-1, AW16E1-1, and AW16 E1-2. Serum-free 48-h CM from hybrid clones was prepared and assayed for angiogenic activity in rat corneas. CM from 5 hybrid clones derived from normal x neoplastic keratinocytes failed to induce an angiogenic response in 28 of 29 (97%) corneas tested. In contrast, CM from 4 hybrid clones derived from fusions between carcinogen-initiated and tumor cells were potently angiogenic in 24 of 25 (96%) corneas tested. Two angiogenesis suppressed hybrids clones were propagated in culture for an extended period of time, to permit chromosome segregation, and were found to re-express the angiogenic phenotype. These result indicate that angiogenesis is a recessive trait in normal hamster keratinocytes which is regulated in trans in these hybrid cells. It would also appear that loss or inactivation of angiogenesis suppressor function occurs early in the neoplastic process.

Expression of the angiogenic phenotype by a subpopulation of keratinocytes derived from 7,12-dimethylbenz[a]anthracene-initiated hamster buccal pouch epithelium.

The evolution of squamous epithelial neoplasms induced by 7,12-dimethylbenz[a]anthracene (DMBA) in Syrian hamster buccal pouch epithelium (HBPE) and the angiogenic potential of a subpopulation of presumptive preneoplastic keratinocytes was evaluated by examining the ability of whole cell dissociates of HBPE and subpopulations of keratinocytes, or their 72-h serum-free conditioned media (CM), to induce neovascularization in rat corneas and directional migration of bovine adrenal gland capillary endothelial cells (BCE) in culture. Buccal pouches were treated in vivo twice weekly for 5 weeks with either DMBA, paraffin oil (PO) or received no treatment. Hamsters were killed at various times after the last application of carcinogen and single-cell suspensions were prepared by enzymatic dissociation. Angiogenesis was assayed by injecting HBPE cells, or by implanting Hydron pellets containing CM in corneas and observing directional ingrowth of capillary blood vessels. Directional migration of BCE under agarose was tested with CM. Angiogenic activity of DMBA-initiated HBPE dissociates was detected initially at 4 and 5 weeks after treatment, was markedly depressed between weeks 8 and 16 and re-emerged in squamous papillomas at week 25. The pattern of expression of angiogenic activity was observed to parallel the frequency of development of a morphologically unique population of keratinocytes that was detected exclusively in cultures of DMBA-exposed HBPE. These unique cells, designated type II keratinocytes, potently stimulated neovascularization in vivo and directional migration of BCE in culture. These results demonstrate that angiogenic activity is an early manifestation of hamster pouch carcinogenesis and suggests that type II keratinocytes, presumptive preneoplastic cells in this model, are the principal source of this activity.

Carcinogenic response of hamster buccal pouch epithelium to 4 polycyclic aromatic hydrocarbons.

In order to assess the relative carcinogenic potency of polycyclic aromatic hydrocarbons in hamster buccal pouch, groups of male Syrian golden hamsters were treated by painting the buccal pouch surfaces for up to 20 weeks with equimolar concentrations of 7, 12-dimethylbenzanthracene; benzanthracene, 3,4-benzpyrene; or 20-methylcholanthrene dissolved in paraffin oil. Control hamsters were simarily treated with paraffin oil. Whereas 100% of the 7, 12-dimethylbenzanthracene treated hamsters developed buccal pouch carcinomas within the 20-week treatment period, no cancers were observed in the control hamsters or in those treated with the other polycyclic aromatic hydrocarbons. Simarily, of the various treatment groups, only 7,12-dimethylbenzanthracene treated hamsters displayed the efficient induction of foci of intense gamma glutamyltranspeptidase (GGT) histochemical activity within the buccal pouch epithelium. These results support the working hypothesis that induction of GGT foci is an early indicator of developing carcinoma in this experimental model.