Review article: The role of oncogenes, tumour suppressor genes and growth factors in oral squamous cell carcinoma: a case of apoptosis versus proliferation

Antiproliferative efficacy of the antioxidant bioactive compounds of defatted seeds of Azadirachta indica and Momordica charantia against the regulatory function of tumor suppressor gene inducing oral carcinoma

The present study focuses on the antiproliferative activity of polyphenolic flavonoids found in defatted seeds of Azadirachta indica and Momordica charantia with the regulatory function of tumor suppressor genes inducing Oral Squamous Cell Carcinoma. Polyphenolic flavonoid in extracts was characterized using chromatographic analysis and has confirmed the presence of quercetin, rutin and tannic acid in the extracts of A. indica and M. charantia. According to DPPH assay and reducing power assays, free radical scavenging was found to be high in ethanolic extract of defatted seeds. Antiproliferative efficacies of defatted seed extracts against KB cell line (mouth) were studied by MTT assay and revealed that aqueous extract of defatted seeds of M. charantia has exhibited maximum antiproliferative activity against KB cells. Antioxidant activity of defatted seed extracts were observed on treated KB cells by determining enzymatic activity (SOD, Cat, and GST) and nonenzyme content (GSH and MDA Content). Using the AutoDock tool, quercetin, rutin and tannin acid revealed that mutant p53, TWIST related protein, TGF-β and Snail I have the best binging energy results. MD simulation was observed on best docking results between the molecule and identified flavonoid by Desmond V 5.9 package . This leads to the conclusion that bioactive extracts with antiproliferative activity, antioxidant capacity and polyphenols with binding efficacy against tumor suppressor gene regulatory function could be used as a herbal remedy.Communicated by Ramaswamy H. Sarma.

Immunoexpression of Apoptosis and Cell-cycle Arrest Markers in Oral Lichen Planus

The expression pattern of a panel of 5 molecular markers (p53, cyclin D1, Ki-67, BCL-2, and BAX) was studied in samples from patients with oral lichen planus (OLP) and normal oral mucosa (NOM) of healthy controls to investigate the implications of cell cycle and apoptosis in OLP. The 59 OLP and 16 NOM biopsies were stained by an inmunoperoxidase technique for p53, cyclin D1, Ki-67, BCL-2, and BAX and assessed microscopically for semiquantitative analysis. Positivity for BCL-2 and Ki-67 was significantly more frequent in NOM than in OLP (P<0.05). p53 levels were upregulated in atrophic/erosive clinical presentations when compared with reticular presentations and in cases with discontinued inflammatory infiltrate. Multivariate analysis through logistic regression showed that BCL-2 in OLP versus NOM was the only significantly altered marker in the present cohort (adjusted odds ratio=12.42; 95% confidence interval: 2.5-61.65; P=0.002). The cell patterns in OLP and NOM are distinct according to the present molecular markers panel. The presence of BCL-2 altered expression may be related to various molecular pathways that connect/link this condition to other autoimmune disorders and also may be involved in complex roles that evoke malignant transformation of OLP.

Etiologic Role of Kinases in the Progression of Human Cancers and Its Targeting Strategies

Cancer is one of the dominant causes of death worldwide while lifelong prognosis is still inauspicious. The maturation of the cancer is seen as a process of transformation of a healthy cell into a tumor-sensitive cell, which is held entirely at the cellular, molecular, and genetic levels of the organism. Tyrosine kinases can play a major, etiologic role in the inception of malignancy and devote to the uncontrolled proliferation of cancerous cells and the progression of a tumor as well as the development of metastatic disease. Angiogenesis and oncogene activation are the major event in cell proliferation. The growth of a tumor and metastasis are fully depending on angiogenesis and lymphangiogenesis triggered by chemical signals from tumor cells in a phase of rapid growth. Tyrosine kinase inhibitors are compounds that inhibit tyrosine kinases and effective in targeting angiogenesis and blocking the signaling pathways of oncogenes. Small molecule tyrosine kinase inhibitors like afatinib, erlotinib, crizotinib, gefitinib, and cetuximab are shown to a selective cut off tactic toward the constitutive activation of an oncogene in tumor cells, and thus contemplated as promising therapeutic approaches for the diagnosis of cancer and malignancies.

Medicinal Plants, Effective Plant Compounds (Compositions) and their Effects on Stomach Cancer

Medicinal plants have special importance around the world. Further, they have been noticed for nutrition and illness treatment such as preparation of anticancer new drugs. Therefore, a wide range of studies have been done on different plants, and their anticancer effects have been investigated. Nowadays, cancer is the most important factor of death rate in the developed and developing countries. Among them, stomach cancer is one of the most common malignancies around the world. At present, it is recognized as the fourth common cancer and the second factor of death rate due to cancer. So far, there has been wide range of effort for cancer treatment; however, in most cases, the response to the treatment has been very weak and often accompanied improper subsidiary effects. The present problems as a consequence of chemical treatment and radiotherapy and many subsidiary problems created due to their use for patients, and also, the resistance to the current treatment has motivated researchers to apply new medicines with more effect and less toxicity. The secondary metabolisms existent in the plants have an important role in the treatment of several diseases such as cancer. This study was conducted to investigate and collect scientific results for stomach cancer and to clarify the role of medicinal plants and secondary plant compounds on its treatment.

Two different protein expression profiles of oral squamous cell carcinoma analyzed by immunoprecipitation high-performance liquid chromatography

Background

Oral squamous cell carcinoma (OSCC) is one of the most dangerous cancers in the body, producing serious complications with individual behaviors. Many different pathogenetic factors are involved in the carcinogenesis of OSCC. Cancer cells derived from oral keratinocytes can produce different carcinogenic signaling pathways through differences in protein expression, but their protein expression profiles cannot be easily explored with ordinary detection methods.

Methods

The present study compared the protein expression profiles between two different types of OSCCs, which were analyzed through immunoprecipitation high-performance liquid chromatography (IP-HPLC).

Results

Two types of squamous cell carcinoma (SCC) occurred in a mandibular (SCC-1) and maxillary gingiva (SCC-2), but their clinical features and progression were quite different from each other. SCC-1 showed a large gingival ulceration with severe halitosis and extensive bony destruction, while SCC-2 showed a relatively small papillary gingival swelling but rapidly grew to form a large submucosal mass, followed by early cervical lymph node metastasis. In the histological observation, SCC-1 was relatively well differentiated with a severe inflammatory reaction, while SCC-2 showed severely infiltrative growth of each cancer islets accompanied with a mild inflammatory reaction. IP-HPLC analysis revealed contrary protein expression profiles analyzed by 72 different oncogenic proteins. SCC-1 showed more cellular apoptosis and invasive growth than SCC-2 through increased expression of caspases, MMPs, p53 signaling, FAS signaling, TGF-β1 signaling, and angiogenesis factors, while SCC-2 showed more cellular growth and survival than SCC-1 through the increased expression of proliferating factors, RAS signaling, eIF5A signaling, WNT signaling, and survivin.

Conclusions

The increased trends of cellular apoptosis and invasiveness in the protein expression profiles of SCC-1 were implicative of its extensive gingival ulceration and bony destruction, while the increased trends of cellular proliferation and survival in the protein profile of SCC-2 were implicative of its rapid growing tumor mass and early lymph node metastasis. These analyses of the essential oncogenic protein expression profiles in OSCC provide important information for genetic counseling or customized gene therapy in cancer treatment. Therefore, protein expression profile analysis through IP-HPLC is helpful not only for the molecular genetic diagnosis of cancer but also in identifying target molecules for customized gene therapy in near future.

Impacts of survivin and caspase-3 on apoptosis and angiogenesis in oral cancer

The present study aimed to investigate the impact of survivin and caspase-3 on apoptosis and angiogenesis in oral cancer. A total of 16 oral leukoplakia cases accompanied by low-moderate epithelial dysplasia, 12 cases of oral leukoplakia accompanied by severe epithelial dysplasia, 17 cases of high-moderate differentiated oral squamous cell carcinoma and 10 cases of normal oral mucosa were selected. Immunohistochemistry was used to detect the expression levels of survivin, caspase-3, and caspase inhibitor factor VIII in lesions from each group. Terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling was performed to detect the apoptotic index of oral leukoplakia and cancer tissue. Immunohistochemistry revealed increased expression levels of survivin in oral cancer tissues, as compared with the normal mucosa, whereas the expression of Caspase-3 was decreased during malignant transformation. Microvascular density (MVD) was increased from 28.49±11.87 strips/mm² (mean ± standard deviation, normal control group) to 91.98±40.20 strips/mm² (oral cancer group). Therefore, survivin may serve an important role in oral cancer, as its expression was increased in association with a downward trend in caspase-3 expression and apoptotic index, whereas MVD was significantly increased.

Potential effects of dietary folate supplementation on oral carcinogenesis, development and progression

Folates are associated with a variety of human health benefits, while folate deficiency has been identified as a potential risk factor for many health problems and cancers, due to its role in dysregulation of DNA synthesis, repair and methylation. The US Food and Drug Administration adopted requirements for folate fortification in some food products, which has resulted in an increase in mean dietary folate intake and a concomitant reduction in the incidence of adverse health effects associated with folate deficiency. This includes a significant reduction in the incidence of folate deficiency-associated birth defects, such as spina bifida.

Effect of Mangrove Tea Extract from Ceriops decandra (Griff.) Ding Hou. on Salivary Bacterial Flora of DMBA Induced Hamster Buccal Pouch Carcinoma

The objective of this study was to investigate the effects of mangrove tea on salivary bacterial flora in DMBA induced hamster buccal pouch carcinoma. Tea from mangrove plant Ceriops decandra was administered against DMBA induced buccal pouch carcinoma in hamster rats. The chemical constitutions and quality of mangrove tea is similar with the commercial tea Camellia sinensis. The Hamster rats were painted thrice a week with DMBA in their right buccal pouch, and also administrated orally with 1.25% of Ceriops tea extract, on alternate days of the DMBA treatment. Appropriate control animals were maintained. After 14 weeks of treatment, bacterial species in saliva were enumerated, tumor incidences were analyzed using histopathological section and tumor volume in the animals was quantified using water-displaced method. The decreased counts of beneficial bacteria and increased counts of harmful bacteria were associated with increased volume of tumors. The present study concluded that the tea extract from C. decandra prevents the oral cancer incidences and maintain the good health conditions of the animals.

The role of bacteria in oral cancer

Despite the widening interest in the possible association between bacteria and different stages of cancer development, our knowledge in its relation to oral cancers remains inadequate. The aim of this review article is to derive a better understanding on the role of various micro-organisms in the etiogenesis of oral cancers through all the available data on the pubmed. Different bacteria have been proposed to induce carcinogenesis either through induction of chronic inflammation or by interference, either directly or indirectly, with eukaryotic cell cycle and signaling pathways, or by metabolism of potentially carcinogenic substances like acetaldehyde causing mutagenesis. Studies have shown diversity of isolated bacterial taxa between the oral cancer tissue specimens and the control, with Exiguobacterium oxidotolerans, Prevotella melaninogenica, Staphylococcus aureus and Veillonella parvula being specific for tumorogenic tissues. Most isolates are saccharolytic and acid tolerant. Streptococcus anginosus, commonly linked with esophageal and pharyngeal cancers, is not of significance in oral cancers. Similarly, significant salivary specificity is noted for three bacteria, namely, Capnocytophaga gingivalis, P. melaninogenica, and Streptococcus mitis in oral cancer patients, making these species salivary markers for the early detection of oral cancers and thus improving the survival rate significantly. Also, such high degree of bacterial specificity in oral cancers has also provoked the designing of new treatment options for cancer prevention by way of vaccine delivery. However, for the success of these steps, a deeper exploration into this subject with a greater understanding is warranted.

Exploring the link between microorganisms and oral cancer: a systematic review of the literature

The majority of cases of oral cancer have been related to tobacco use and heavy alcohol consumption. However, the incidence of oral cavity carcinoma appears to be increasing in many parts of the world in a manner that it is difficult to explain with traditional risk factors alone. Meanwhile, interest in the possible relationships between microorganisms and the different stages of cancer development has been rising and numerous mechanisms by which bacteria and yeast may initiate or promote carcinogenesis are currently under investigation. In particular, a persuasive body of evidence suggests a possible etiological role involving the metabolism and production of carcinogenic products, such as acetaldehyde. Other suggested mechanisms include the induction of chronic inflammation and direct interference with eukaryotic cell cycle and signaling pathways. This review aims to summarize the known associations between microbial infection and cancer and draw attention to how they may relate to oral carcinoma.

A novel immunocompetent murine model for Candida albicans-promoted oral epithelial dysplasia

Candida albicans is a common opportunistic pathogen found in the oral mucosa. Clinical observations indicate a significant positive association between oral Candida carriage or infection and oral epithelial dysplasia/neoplasia. The aim of this study was to test whether C. albicans is able to promote epithelial dysplasia or carcinoma in a mouse model of infection where a carcinogen (4 Nitroquinoline 1-oxide [4NQO]) was used as initiator of neoplasia. Mice were divided into four groups: group 1 received 4NQO alone; group 2 received 4NQO followed by C. albicans (ATCC 90234); group 3 received vehicle dimethyl sulfoxide (DMSO) followed by C. albicans and group 4 was untreated. Although 4NQO treated mice did not develop oral lesions, mice exposed to both 4NQO and C. albicans developed oral dysplastic lesions 19 weeks after exposure to 4NQO. Mice challenged with C. albicans only developed hyperplastic lesions. The expression of Ki-67 and p16, two cell-cycle associated proteins that are frequently deregulated in oral dysplasia/neoplasia, was also tested in these lesions. Ki-67 and p16 expression increased from normal to hyperplastic to dysplastic mucosa and was highest in the group exposed to both 4NQO and C. albicans. In conclusion, we showed that C. albicans plays a role in the promotion of oral dysplasia in a mouse model of infection when 4NQO was used as initiator of oral neoplasia.

Over-expression of c-Myc oncoprotein in oral squamous cell carcinoma in the South Indian population

Oral neoplasm constitutes a predominant class of cancer that is encountered in South India. This is in large part due to the elevated risk of oncogenesis as a result of the habit of chewing of quids containing betel leaves, areca nut and smokeless tobacco. An array of molecular events are induced during the transformation of the buccal epithelium, among them the over-expression of oncogene products plays a key role. The c-Myc protein, a regulator of a number of key cellular signalling pathways, plays a pivotal role in a number of malignancies. The present study was undertaken to evaluate expression of the c-Myc protein in tumours of the oral cavity from the South Indian population, predominantly oral squamous cell carcinoma (OSCC). The c-Myc protein was over-expressed in 80% of the cases studied. Taking into account the pivotal role demonstrated for c-Myc in tumourigenesis, our observations suggest a key role for Myc oncoprotein in the genesis of OSCC as well as its potential as a therapeutic target in this population.

Viable bacteria present within oral squamous cell carcinoma tissue

Despite increasing interest in the possible relationships between bacteria and the different stages of cancer development, the association of bacteria with cancer of the oral cavity has yet to be adequately examined. With that in mind, the primary objective of this study was to identify any bacterial species within oral squamous cell carcinoma tissue using a standard microbiological culture approach. At the time of surgery, a 1-cm3 portion of tissue was harvested from deep within the tumor mass using a fresh blade for each cut. Whenever possible, "superficial" portions from the mucosa overlying the tumor and nontumorous control specimens from at least 5 cm away from the primary tumor site were also obtained. Surface contamination was eliminated by immersion in Betadine and washing with phosphate-buffered saline. Each specimen was aseptically macerated and cultured on nonselective media under both aerobic and anaerobic conditions. Isolates were identified by 16S rRNA gene sequencing. Twenty deep-tissue specimens, 19 with corresponding superficial tissues and 12 with control tissues, were successfully processed. A diversity of bacterial taxa were isolated and identified, including several putatively novel species. Most isolates were found to be saccharolytic and acid-tolerant species. Notably, some species were isolated only from either the tumorous or nontumorous tissue type, indicating a degree of restriction. Successful surface decontamination of the specimens indicates that the bacteria detected were from within the tissue. A diversity of bacterial groups have been isolated from within oral squamous cell carcinoma tissue. The significance of these bacteria within the tumor warrants further study.

p53 Transgenic mice are highly susceptible to 4-nitroquinoline-1-oxide-induced oral cancer

In this study, we did a bioassay employing mice with a dominant-negative p53 mutation (p53(Val135/WT)) to assess whether a germ-line p53 mutation predisposed mice toward the development of squamous cell carcinomas (SCC) in the oral cavity. Treatment of the mouse oral cavity with 4-nitroquinoline-1-oxide produced a 66%, 91%, and 20% tumor incidence in the oral cavity, esophagus, and forestomach/stomach, respectively, in p53(Val135/WT) mice. In contrast, only a 25%, 58%, and 4% tumor incidence was observed in oral cavity, esophagus, and forestomach/stomach, respectively, in wild-type littermates (p53(WT/WT)). The most striking difference between p53(Val135/WT) and p53(WT/WT) mice following the carcinogen treatment was the higher prevalence and more rapid development of SSC in p53(Val135/WT) mice than in wild-type mice. To identify the precise genes or pathways involved in these differences during tumor development, we examined gene expression profiles of 4-nitroquinoline-1-oxide-treated normal tongues as well as tongue SCC in p53(Val135/WT) and p53(WT/WT) mice. Microarray and GenMAPP analysis revealed that dominant-negative p53 ((135)Valp53) affects several cellular processes involved in SCC development. Affected processes included apoptosis and cell cycle arrest pathways, which were modulated in both tumor and normal epithelium. These results showed that reduction of p53-dependent apoptosis and increases in cell proliferation might contribute to the observed increase in oral cavity and gastroesophageal malignancies in p53(Val135/WT) mice as well as to the more rapid growth and progression of tumors.

Immunohistochemical analysis of apoptosis-related factors in lining epithelium of radicular cysts

BACKGROUND

Some studies suggest that apoptosis-related factors are involved in the inflammatory processes of marginal periodontal lesions. However, the role of apoptosis in periapical inflammatory lesions remains unclear. We investigated the possible role of apoptotic cell death in periapical inflammatory lesions by means of immunohistochemical analysis of apoptosis-related factors and use of a cell proliferation marker.

METHODS

Paraffin-embedded sections of 19 radicular cysts (RCs), and five residual radicular cysts (RRCs) and control specimens of normal gingivae excised from seven cadavers were prepared and examined immunohistochemically with the use of monoclonal antibodies or polyclonal antisera against single-stranded DNA (ssDNA), p53, Bax, Bcl-2, caspase-3, Fas, Fas ligand (Fas-L), and Ki-67 antigen.

RESULTS

Epithelium of gingiva, RCs, and RRCs showed expression of ssDNA in suprabasal and superficial epithelial cells and Ki-67 reactivity in basal and parabasal cells. Expression of Ki-67 and ssDNA in RCs and RRCs was slightly higher than that in gingiva. Both Ki-67 and ssDNA reactivity in RCs with intense inflammatory reactions or with thick lining epithelium were significantly stronger than those in RCs with less inflammatory reactions or with thin lining epithelium. Reactivity for p53 was noted sporadically in epithelium of gingiva, RCs, and RRCs, and p53 expression in RCs was significantly greater than that in gingiva. Ki-67 and ssDNA reactivity in RCs increased parallel to the degree of p53 expression. Bax and Bcl-2 were detected in some basal epithelial cells in RCs and RRCs as well as in gingiva. The ssDNA reactivity significantly increased parallel to Bax expression and slightly decreased parallel to Bcl-2 expression in lining epithelium of RCs. Caspase-3 was detected in superficial epithelial cells of both gingiva and lining epithelium of RCs and RRCs, and the distribution of these cells was compatible with the expression of ssDNA. Expression of Ki-67 and ssDNA in caspase-3-positive fields was significantly higher than that in caspase-3-negative fields in RCs. There was very limited expression of Fas and Fas-L in lining epithelium of RCs and RRCs as well as in gingiva.

CONCLUSIONS

These data suggest that apoptosis-related factors are involved in the pathophysiologic activity of periapical inflammatory lesions. Such factors may be affected by the structure of lining epithelium and the degree of inflammatory change.

Placental maturation and expulsion in Holstein and Nelore cows

Morphological changes in the placenta at periparturition and the involvement of apoptosis controlling cell populations in the placentome were evaluated in Holstein and Nelore cows. Twenty-two Holstein cows at the end of gestation with normal non-induced parturition (group I) and 10 Holstein cows with induced parturition (group II) were used in this study. In addition, groups III and IV were constituted by 10 Nelore cows at the end of gestation with normal non-induced parturition and 21 Nelore cows with induced parturition, respectivelly. Binucleate trophoblastic cells, epithelial caruncular cells and apoptotic bodies were quantified by light microscopy. Apoptosis was further evaluated by transmission electron microscopy, ELISA and DNA electrophoresis in agarose gel. The number of caruncular epithelial cells did not vary between breeds with normal or induced parturition. The number of binucleate cells was significantly different between Holstein and Nelore cows with normal non-induced parturition (groups I vs. III), but their numbers were not significantly different between breeds when parturition was induced. In cows with normal non-induced parturition, the intensity of apoptosis, as assessed by morphometric analysis and ELISA, was significantly higher in group I when compared to group III. However, no difference in the intensity of apoptosis was found between groups II and IV. Characteristic apoptotic ladder pattern of DNA fragmentation was detected by agarose gel electrophoresis. Ultra-structural features of apoptosis in maternal and fetal epithelium as well as capillary vascular endothelium were identified by transmission electron microscopy. In conclusion, in Nelore placental maturation occurs precociously when compared to Holstein. In both breeds, apoptosis is an active physiological event that seems to be required for maturation and normal post-partum release of the placenta.

Differential c-myc expression profiles in normal human bronchial epithelial cells following treatment with benzo[a]pyrene, benzo[a]pyrene-4,5 epoxide, and benzo[a]pyrene-7,8-9,10 diol epoxide

Bronchial epithelial cells are often exposed to airborne mutagens that have the potential to induce genetic changes involved in the development of lung cancer. Although lung tumors often display alterations in the expression of oncogenes and/or tumor suppressor genes, the role of specific chemicals and/or metabolites in causing these alterations is not well defined. The polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (B[a]P), a by-product of combustion, is a prevalent airborne environmental mutagen and a constituent of cigarette smoke. The primary objective of this study was to compare the effect of B[a]P and two of its reactive metabolites, benzo[a]pyrene diol epoxide (BPDE or bay region epoxide) and benzo[a]pyrene-4,5-dihydroepoxide (BPE or K-region epoxide), on expression of the proto-oncogene c-myc in normal human bronchial epithelial (NHBE) cells using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. Changes in c-myc gene expression were compared with DNA adduct formation, growth inhibition, and cell-cycle progression as determined by (32)P-postlabelling, neutral red (NR), and flow cytometric analyses, respectively. None of the three test compounds altered the levels of 18S ribosomal RNA or beta-actin at the concentrations evaluated for c-myc expression, indicating that nonspecific changes in gene expression induced by cytotoxicity, for example, were not present at the concentrations evaluated. Cells exposed to B[a]P exhibited a dose-dependent increase in c-myc expression; conversely, a dose-dependent decrease in c-myc expression was observed following BPDE exposure. A marginal but concentration-dependent increase in c-myc mRNA levels was observed following exposure to the K-region epoxide. Our results demonstrated that, although B[a]P and its metabolites alter c-myc expression, the parent compound and its metabolites produce unequal and contrasting effects on the expression of this gene.

[Genic alterations in oral and head and neck squamous cell carcinomas: analysis of international literature]

The development of oral and head and neck squamous cell carcinomas occurs in relation with multiple events including mainly: loss of cycle cell control, evasion from apoptosis, telomerase reactivation. Complex interactions between a set of molecules, cell cycle proteins, tumour suppressor genes, oncogenes and the telomerase, occur in the multiple step process of carcinogenesis. The 2 main ways of control of the cell cycle rely on 2 tumour suppressor genes: the P53 gene and the retinoblastoma gene or RB gene. One of the regulation pathways or the 2 regulation pathways are disabled during the development of oral and head and neck squamous cell carcinomas. Most of the time, the inactivation of the P53 pathway results from a loss of function of the p53 protein, secondary to mutation and/or deletion of the P53 gene; It may also result of the amplification of the MDM2 gene and of the inactivation of the arf protein. The RB pathway leads to cell proliferation by loss of the p16 protein, by amplification of the cyclin D1 gene and less frequently by mutation of the RB gene or loss of the retinoblastoma protein. In India and South-East Asia, the activation of RAS and MYC oncogenes appears to be related with the presence of specific carcinogens in snuff and tobacco. By blocking apoptosis, the Bcl2 protein seems to increase the resistance of tumours to radiotherapy and chemotherapy.

Analysis of proliferation, apoptosis and keratin expression in cultured normal and immortalized human buccal keratinocytes

The current study was undertaken to analyse growth and differentiation-related functions of normal keratinocytes (NOK) and an SV40T-immortalized keratinocyte line (SVpgC2a) from buccal mucosa, viewing the latter cell line as a model of a dysplastic epithelium. Morphological and immunohistochemical assessments of organotypic epithelia generated from 10 or 17 d of culture showed three- to five-fold higher apoptotic and proliferative activity in SVpgC2a relative to NOK. Conditions with or without serum (up to 10%) did not significantly influence these parameters in NOK whereas serum supported proliferation of SVpgC2a. Both cell types showed basal expression of collagen IV and laminin 1, indicating basal lamina, as well as vimentin, indicating an activated, proliferative state. Reduced expression of keratin, including the non-keratinizing marker K13, was seen in SVpgC2a. Assessment of proliferative monolayer cultures by microarray showed that NOK transcribed tissue-specific keratins, but also the epidermal keratin K2a, several simple epithelial keratins and low levels of hair keratins. SVpgC2a transcribed keratins seen in epithelial dysplasia, and K2a and hair keratins, albeit at low level. Overall, the results implied aberrant apoptosis, proliferation and keratin expression in the immortalized state of SVpgC2a. Comparison of NOK and SVpgC2a under identical culture conditions may serve to model the progression from a normal to a pre-neoplastic state of buccal epithelium.

Ethanol decreases negative cell-cycle-regulating proteins in a head and neck squamous cell carcinoma cell line

Epidemiologic studies have provided evidence of an alcohol-associated increased risk of upper aerodigestive tract cancers. Recently we reported ethanol-induced proliferation in a squamous cell carcinoma of the head and neck (SCCHN) cell line, but the underlying mechanisms are unknown. In order to further clarify these findings, major G0/G1-regulating proteins were investigated in the present study. Synchronized cells of a SCCHN line (JP-PA) and a human immortalized keratinocyte line (HaCaT)-used as a control-were cultured with or without 10(-3) M ethanol for up to 96 h. At distinct time intervals the expression of cyclin D1 and the inhibitors p16, p18, p19 and p21 were determined by Western blot analyses. In both lines ethanol had no influence on the protein expression of cyclin D1. In contrast, distinct downregulations of p21, p18 and p19 were detectable at the protein level. The p16 protein was not expressed in the SCCHN line and was unchanged in the control line after the addition of ethanol. In these in vitro experiments the marked downregulation of important cell-cycle inhibitors may accelerate progression from the G1 to the S phase of the cell cycle. The relevance of our findings to in vivo conditions remains speculative, but the observed mechanisms of significantly reduced expression of cell-cycle inhibitor proteins may be involved in the carcinogenesis of head and neck malignancies.

Potential molecular prognostic markers in head and neck squamous cell carcinomas

BACKGROUND

Current management strategies for squamous cell carcinoma of the head and neck (HNSCC) rely on an understanding of the natural history of the disease, along with the use of prognostic factors to guide selection of appropriate treatment. However, it is recognized that tumor heterogeneity limits the reliable use of currently available prognostic markers. With the evolving understanding of the genetic and molecular basis of human malignancies, there has been much interest in determining whether specific molecular changes in HNSCC might guide treatment decisions.

METHODS

A literature review of potential molecular markers relevant to HNSCC was undertaken and evaluated. It is evident that the published information is promising but, oftentimes, limited by a scarcity of large, uniformly staged and treated patients, from which the value of novel molecular markers can be assessed.

RESULTS

On the basis of the review of more than 100 articles, some of the emerging molecular markers that might provide independent prognostic information include epidermal growth factor receptor (EGFR), transforming growth factor-alpha (TGF-alpha), cyclin D1, and p53. This review will discuss the current status of these molecular factors and consequent implications for novel therapeutic approaches for patients with HNSCC.

CONCLUSION

With the evolving understanding that human malignancies have developed and progressed on the basis of accumulated molecular abnormalities, there is an existing body of work trying to determine whether such abnormalities can predict clinical behavior of HNSCC. Such studies have to be conducted rigorously to derive useful information. Nevertheless, the role of such molecular markers, and the possibility to exploit them for therapeutic gain, is already at the horizon.

doc-1--mediated apoptosis in malignant hamster oral keratinocytes

PURPOSE

Cell cycle mediators involved in inducing apoptosis are frequently deregulated during carcinogenesis. Deleted in oral cancer-1 (doc-1) is an S-phase regulator that is inactivated during oral carcinogenesis. Transfection of doc-1 into malignant oral keratinocytes leads to increased cell loss. It is hypothesized that ectopic expression of doc-1 in hamster oral cancer cells induces apoptosis.

MATERIALS AND METHODS

Malignant hamster oral keratinocytes (wt-HCPC-1), which lack measurable doc-1 mRNA and protein, were previously transfected with either a CMV-doc-1 expression vector construct (doc-HCPC-1) or the parental control vector pcDNA3 (cv-HCPC-1). A trypan blue exclusion assay was performed to examine cell death in the parental or wild-type HCPC-1 keratinocytes, HCPC-1 transfected with the parental pcDNA3 vector, and the doc-1 transfected HCPC-1 cells. To examine whether ectopic expression of doc-1 mediates gross cellular changes consistent with apoptosis, toluidine blue-safranin differential staining and the quantitative fluorescent microscopy assays were performed. To identify early apoptotic cytochemical changes observed in the cell membrane and nucleus, annexin V/propidium iodide (PI) fluorescence-activated cell sorter (FACS) analysis and the terminal deoxytransferase-mediated dUTP nick-end labeling (TUNEL) assay were performed.

RESULTS

Doc-HCPC-1 showed elevated numbers of dead cells over wt-HCPC-1 and cv-HCPC-1 in the trypan blue exclusion assay. Toluidine blue-safranin staining and quantitative fluorescent microscopy showed significant morphologic changes in the doc-1 transfectants consistent with apoptosis (P < .05). TUNEL assays (P < .05) and annexin V/PI FACS analysis (P < .05) also showed early cytochemical changes in the doc-HCPC-1 transfectants, confirming that ectopic expression of doc-1 induces apoptosis.

CONCLUSIONS

These data suggest that doc-1 induces apoptosis in malignant hamster oral keratinocytes. It is hypothesized that doc-1 is a mediator of apoptosis that is inactivated during hamster oral carcinogenesis.

Smokeless tobacco potentiates VIP-induced DNA synthesis and inactivates NEP 24.11 in oral keratinocytes

The purpose of this study was to determine whether exposure of cultured chemically transformed hamster oral keratinocytes (HCPC-1) to an aqueous extract of smokeless tobacco (STE) potentiates DNA synthesis elicited by vasoactive intestinal peptide (VIP), an autocrine neuropeptide, and, if so, whether this response is associated with inactivation of neutral endopeptidase 24.11 (NEP 24. 11), an ectoenzyme that cleaves and inactivates VIP very effectively, in these cells. I found that STE and VIP each elicited a modest, albeit significant, increase in DNA synthesis in cultured HCPC-1 cells (P < 0.05). However, incubation of HCPC-1 cells with STE together with VIP evoked a significant, concentration- dependent increase in DNA synthesis that was mediated by VIP receptors. The effects of STE and VIP were synergistic. Maximal response was observed after a 48-h incubation. STE significantly attenuated NEP 24.11 activity in HCPC-1 cells at a time when VIP-induced DNA synthesis was maximal. Collectively, these data indicate that STE potentiates VIP-induced DNA synthesis in cultured oral keratinocytes, and that this response is temporally related to STE-induced inactivation of NEP 24.11 in these cells. I suggest that NEP 24.11 modulates the mitogenic effects of smokeless tobacco in the oral epithelium, in part, by inactivating VIP.

Current concepts in oral cancer

Over 750 new intra-oral squamous cell carcinomas are registered in Australia each year. In this article, the authors review the epidemiology, aetiology, genetics and spread of intra-oral squamous cell carcinoma. The mechanisms of field cancerization are discussed. The prevention of intra-oral squamous cell carcinoma is highlighted and future treatments are presented.

Expression of biomarkers (p53, transforming growth factor alpha, epidermal growth factor receptor, c-erbB-2/neu and the proliferative cell nuclear antigen) in oropharyngeal squamous cell carcinomas

Using immunohistochemistry, expression of p53, transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), c-erbB-2/neu and proliferating cell nuclear antigen (PCNA) was examined in 26 fresh frozen tissue specimens of oropharyngeal squamous cell carcinomas (SCCs). p53 gene mutations were examined by polymerase chain reaction (PCR)/DNA sequencing methods in 22 carcinomas. The findings were examined for correlations with patients' clinicopathological parameters. Expressions of p53 and PCNA were also examined in 21 formalin-fixed corresponding tissues. Of the fresh frozen tissue specimens, 77% (20/26) showed expression and 68% (15/22) showed mutations (substitutions) of the p53, with significant clustering of the mutations in exons 5 (8/22; 36%), 7 (4/22; 18%) and 8 (5/22; 23%). No mutations were found in exon 6. There was a discordance between expression of p53 protein and mutations of the gene. Parallel to expression and mutations of the p53 found in most of the specimens, expression of TGF-alpha, EGFR, c-erbB-2/neu and PCNA was found in 88% (22/25), 92% (23/25), 58% (14/24) and 91% (21/23) of the specimens, respectively. For the formalin-fixed tissue specimens, 62% (13/21) and 90% (19/21) expressed p53 and PCNA, respectively. Examining for correlations with patients' clinicopathological parameters, expression of p53, TGF-alpha, EGFR and c-erB-2/neu seemed to negatively correlate with the increase of the tumour grade. The present work suggests that: (1) lack of negative growth regulation due to inactivation of the p53 gene together with activation of other proto-oncogenes are necessary genetic events in the carcinogenesis of oropharyngeal SCCs; (2) in oropharyngeal SCCs, p53 gene mutations were clustered in exons 5 (codons 130-186), 7 (codons 230-248) and 8 (codons 271-282) which perhaps suggests that tobacco carcinogens probably affect the mutational hot spots of the p53 gene at codons 157, 175, 186, 248, 273 and 282; and (3) fresh frozen and formalin-fixed tissue specimens give similar results when an immunohistochemical method is applied. The importance of p53, TGF-alpha, EGFR, c-erbB-2/neu and PCNA as biomarkers in oropharyngeal SCCs deserves particular attention because it might offer further understanding of the development of these carcinomas.

Expression of p16 and CDK4 in oral premalignant lesions and oral squamous cell carcinomas: a semi-quantitative immunohistochemical study

The protein, p16, the product of cyclin-dependent kinase number 2 (CDKN2) gene, is one of the negative regulators of the cell cycle. CDK4, encoded by CDK4 gene, is the substrate of p16. We investigated the expression of p16 and CDK4 and their role in the progression of oral premalignant lesions (OPLs) and oral squamous cell carcinomas (OSCCs) in a Chinese cohort. A total of 74 samples were obtained from patients with hyperkeratosis (10), OPLs [30; mild (10), moderate (10) and severe (10) dysplastic lesions], OSCCs (15; 8 non-metastatic, 7 metastatic), and normal oral tissues (10), together with local lymph nodes (9) of patients with metastatic OSCCs. A labelled streptavidin biotin (LSAB) immunohistochemistry assay was performed and a semi-quantitative method was used to evaluate the staining intensity. The staining patterns of p16 and CDK4 were similar in all tissues and were located in both the nuclei and the cytoplasm. However, the antigen distribution characteristics and the degree of expression of both p16 and CDK4 varied at different developmental stages of the lesions. Hyperkeratotic and dysplastic lesions tended to display a progressively increasing degree of p16- and CDK4-positive nuclei as compared with normal tissues. Also, positive staining cytoplasm was highly evident in OSCCs with a very low nuclear staining (P<0.05). Forty-six of 56-, p16-positive cases were CDK4-positive, while only 6 were CDK4-positive but p16-negative, implying a high correlation between these parameters (r=0.813, P<0.001). This study indicates that the expression of p16 and CDK4 is intimately involved in the development of OPLs and OSCCs and the likely existence of a positive feedback loop between p16 and CDK4.

An immunohistochemical study of p53 and PCNA in inflammatory papillary hyperplasia of the palate: a dilemma of interpretation

OBJECTIVE

Inflammatory papillary hyperplasia of the palate (IPHP) or the granular type of denture stomatitis, is a non-neoplastic lesion characterized histologically by a significant epithelial hyperplasia and inflammatory infiltrate usually caused by trauma and Candida infection. p53 and proliferative cell nuclear antigen (PCNA) are cell-cycle regulators, that when overexpressed, are considered by many investigators as markers of malignant transformation. The objective of this study was to investigate the immunodetection of p53 and PCNA in IPHP, and to correlate these results with the degree of epithelial hyperplasia and inflammatory infiltrate.

MATERIALS AND METHODS

In 12 cases diagnosed clinically as IPHP, Candida was cultured from the denture base and the palatal mucosa. Lesions were biopsied and stained with H&E for histomorphometric analysis of the epithelial width and inflammatory infiltrate. PAS and Gram stains were used for screening of Candida. Sections were immunostained with DO-7 for p53 and PC-10 for PCNA. Fifteen palatal biopsies obtained from autopsies of edentulous subjects with normal palatal mucosa served as controls.

RESULTS

All cultures of swabs from both the palatal mucosa and denture base were positive for Candida. Candidal hyphae could not be identified in PAS stained sections. Small foci of Gram-positive organisms were found in two cases of IPHP. Epithelial width and inflammation were significantly higher in IPHP than in controls (P < 0.001). A three-fold increase in positively stained cells for p53 and a two-fold increase in positively stained cells for PCNA were seen in IPHP compared with controls (P < 0.001).

CONCLUSIONS

Although a significant increase in the immunodetection of p53 and PCNA may indicate a malignant potential, IPHP has never been reported to undergo malignant transformation nor is it associated with cytologic signs of dysplasia. The increase in the epithelial width and inflammation degree is probably associated with the colonization of the denture bases with Candida organisms. The increased detection of p53 and PCNA can be a secondary effect of cytokines originating from both the inflammatory cells and the keratinocytes. Thus, immunodetection of p53 and PCNA by current immunohistochemical methods on archival tissues is neither specific nor sensitive enough to be used as indicators for malignant potential in the absence of cytological dysplastic changes or genetic proof of mutated cell cycle genes.

Apoptosis: clinical relevance and pharmacological manipulation

Apoptosis, often synonymously used with the term 'programmed cell death', is an active, genetically controlled process that removes unwanted or damaged cells. Suppression, overexpression or mutation of a number of genes which orchestrate the apoptotic process are associated with disease. The diseases in which apoptosis has been implicated can be grouped into 2 broad groups: those in which there is increased cell survival (i.e. associated with inhibition of apoptosis) and those in which there is excess cell death (where apoptosis is overactive). Diseases in which there is an excessive accumulation of cells include cancer, autoimmune disorders and viral infections. Deprivation of trophic factors is known to induce apoptosis in cells dependent on them for survival. This fact has been exploited in the use of antiandrogens or antiestrogens in the management of prostate or breast cancer. Haemopoietic growth factors like granulocyte-macrophage colony stimulating factor (GM-CSF) or interleukin-3 prevent apoptosis in target cells and modulation of levels of these factors has been tried in the prevention of chemotherapy-induced myelosuppression. Until recently, it was thought that cytotoxic drugs killed target cells directly by interfering with some life-maintaining function. However, of late, it has been shown that exposure to several cytotoxic drugs with disparate mechanisms of action induces apoptosis in both malignant and normal cells. Physiological regulation of cell death is essential for the removal of potentially autoreactive lymphocytes during development and the removal of excess cells after the completion of an immune response. Recent work has clearly demonstrated that dysregulation of apoptosis may underlie the pathogenesis of autoimmune diseases by allowing abnormal autoreactive lymphocytes to survive. AIDS and neurodegenerative disorders like Alzheimer's or Parkinson's disease represent the most widely studied group of disorders where an excess of apoptosis has been implicated. Amyotrophic lateral sclerosis, retinitis pigmentosa, epilepsy and alcoholic brain damage are other neurological disorders in which apoptosis has been implicated. Apoptosis has been reported to occur in conditions characterised by ischaemia, e.g. myocardial infarction and stroke. The liver is a site where apoptosis occurs normally. This process has also been implicated in a number of liver disorders including obstructive jaundice. Hepatic damage due to toxins and drugs is also associated with apoptosis in hepatocytes. Apoptosis has also been identified as a key phenomenon in some diseases of the kidney, i.e. polycystic kidney, as well as in disorders of the pancreas like alcohol-induced pancreatitis and diabetes.

Alteration of proto-oncogenes during apoptosis in the oral squamous cell carcinoma cell line, SAS, induced by staurosporine

Staurosporine (ST) has been reported to induce apoptosis in many kinds of cultured cells. The pathway of the apoptosis induced by ST is still not clear. Certain proto-oncogene expressions have been shown to be involved in the apoptotic pathway. The present study characterized apoptosis induced by ST in the oral squamous cell carcinoma cell line, SAS, focusing on the alteration of proto-oncogene expression. SAS showed typical apoptotic features upon exposure to ST. We compared the level of gene expression in apoptosis induced by ST with that by withdrawal of serum, which is a common system to induce apoptosis. By RT-PCR analysis, ST-induced apoptosis showed c-fos and c-jun up-regulation, whereas serum withdrawal-induced apoptosis showed c-jun up-regulation and the same levels of p21/waf-1 and c-myc. These results indicate that ST can rapidly induce apoptosis in SAS, possibly via a c-fos and c-jun pathway.

The high risk human papillomaviruses and oral cancer: evidence for and against a causal relationship

Oncogenic human papillomaviruses (HPVs) have been detected in oral squamous cell carcinoma (SCC). HPV16 is the most frequently detected HPV type in oral SCC and is present in up to 22% of cases, either alone or in combination with other HPV types. HPV18 is present in up to 14% of cases. HPV16 and HPV18 are present together in approximately 6% of cases. However, HPV16 and 18 are also detected in normal oral mucosae (10% and 11% of subjects, respectively). These data suggest that high risk HPV infection may be a co-factor in oral carcinogenesis and that latent HPV infection of the oral mucosa is common. A role for HPV infection in oral carcinogenesis is supported by the ability of high risk HPVs to immortalize oral keratinocytes in vitro. Immortalization may involve (i) deactivation of pre-formed tumor-suppressor proteins by viral oncoproteins, (ii) blocking of tumor-suppressor gene transcription as a result of HPV oncogene insertion or (iii) stimulation of cellular oncogene transcription by the upstream insertion of HPV-derived transcription activating sequences. Hence, infection of oral keratinocytes with high risk HPV may be involved in the pathogenesis of some oral SCCs although the evidence implicating HPV in oral carcinogenesis is, at present, mainly circumstantial.