p53 binds the mdmx mRNA and controls its translation

MDMX and MDM2 are two nonredundant essential regulators of p53 tumor suppressor activity. MDM2 controls p53 expression levels, whereas MDMX is predominantly a negative regulator of p53 trans-activity. The feedback loops between MDM2 and p53 are well studied and involve both negative and positive regulation on transcriptional, translational and post-translational levels but little is known on the regulatory pathways between p53 and MDMX. Here we show that overexpression of p53 suppresses mdmx mRNA translation in vitro and in cell-based assays. The core domain of p53 binds the 5' untranslated region (UTR) of the mdmx mRNA in a zinc-dependent manner that together with a trans-suppression domain located in p53 N-terminus controls MDMX synthesis. This interaction can be visualized in the nuclear and cytoplasmic compartment. Fusion of the mdmx 5'UTR to the ovalbumin open reading frame leads to suppression of ovalbumin synthesis. Interestingly, the transcription inactive p53 mutant R273H has a different RNA-binding profile compared with the wild-type p53 and differentiates the synthesis of MDMX isoforms. This study describes p53 as a trans-suppressor of the mdmx mRNA and adds a further level to the intricate feedback system that exist between p53 and its key regulatory factors and emphasizes the important role of mRNA translation control in regulating protein expression in the p53 pathway.

Autoantibodies and decreased expression of the transcription factor ELF-3 together with increased chemokine pathways support an autoimmune phenotype and altered differentiation in lichen planus located in oral mucosa

BACKGROUND

The pathogenesis of oral lichen planus (OLP), a chronic inflammatory disease, is not fully understood. It is known that OLP has autoimmune features, and it is suggested to be an autoimmune disease. ELF-3 is involved in differentiation of keratinocytes and deregulated in different tumours and inflammatory diseases. CXCR-3 and its ligands CXCL-10 and CXCL-11 are increased in autoimmune diseases and linked to Th-1 immune response.

OBJECTIVES

To analyse and compare expression of ELF-3, CXCR-3, CXCL-10 and CXCL-11 in OLP lesions and controls in whole and microdissected epithelium.

METHODS

Tissue biopsies from 20 patients clinically and histologically diagnosed with OLP and 20 healthy controls were studied using whole tissues or microdissected epithelium. By the use of qRT-PCR, mRNA levels of ELF-3, CXCR-3, CXCL-10 and CXCL-11 were studied. Western blot was used for analysis of ELF-3 protein expression. Sera from 19 OLP patients and 20 controls were analysed with ELISA in search for autoantibodies. Results  The upregulation of CXCR-3, CXCL-10 and CXCL-11 found in OLP is similar to previous findings showing an autoimmune phenotype in lichen planus (LP) and lichen sclerosus. Decreased expression of the differentiation-related transcription factor ELF-3 was also seen in OLP lesions, and we further demonstrate presence of circulating autoantibodies against the ELF-3 protein in sera from 3 of 19 (16%) LP patients tested.

CONCLUSIONS

On the basis of these findings, we confirm that OLP shows features of an autoimmune disease and suggest deregulated differentiation of keratinocytes to be one of the causes of the disease phenotype.

Scandinavian Fellowship for Oral Pathology and Oral Medicine: guidelines for oral pathology and oral medicine in the dental curriculum

In Scandinavia, as in many European countries, most patients consult their general dentist once a year or more. This gives the dentist a unique opportunity and an obligation to make an early diagnosis of oral diseases, which is beneficial for both the patient and the society. Thus, the dentist must have knowledge of clinical symptoms, local and systemic signs and clinical differential diagnoses to make an accurate diagnosis. The dentist must be competent in selecting appropriate diagnostic tests, for example, tissue biopsy and microbiological samples, and conducting them correctly, as well as in interpreting test results and taking appropriate action accordingly. Furthermore, the dentist must be aware of diseases demanding multidisciplinary cooperation and be able to recognise his/her professional limitation, and to refer to other specialists when required. The dental curriculum changes over time as new approaches, treatments and diagnostic possibilities develop. Likewise, the role of the dentist in the community changes and may vary in different countries. As members of the Scandinavian Fellowship for Oral Pathology and Oral Medicine and subject representatives of oral pathology and oral medicine, we feel obliged to contribute to the discussion of how the guidelines of the dental curriculum support the highest possible standards of dental education. This article is meant to delineate a reasonable standard of oral pathology and oral medicine in the European dental curriculum and to guide subject representatives in curriculum development and planning. We have created an advisory topic list in oral pathology and oral medicine.

Increased levels of COX-2 in oral lichen planus supports an autoimmune cause of the disease

BACKGROUND

Oral lichen planus (OLP) is a chronic inflammatory disease for which the pathogenesis is not fully understood. OLP has autoimmune features and auto immunity has been suggested as a potential cause, whereas WHO has classified OLP as a premalignant condition. Association between chronic inflammation and cancer is known and chronic inflammation is one of the characteristics of OLP. A protein connected to inflammation and suggested to be involved in cancer development is cyclooxygenase-2 (COX-2) which can be inhibited by microRNA-26b (miR-26b).

OBJECTIVE

The aim was to map levels of COX-2 and miR-26b in OLP lesions to see if there was any correlation between expression of COX-2 and its regulator miR-26b in OLP.

METHODS

In biopsies from 20 OLP patients and 20 age and gender-matched controls laser- micro dissection of epithelium was performed. Quantitative RT-PCR, immunohistochemistry and Western blot were used in the analysis.

RESULTS

Levels of COX-2 mRNA were significantly higher while levels of miR-26b were significantly lower in OLP lesions compared to controls. Using immunohistochemistry normal oral mucosa samples did not show any expression of COX-2 while OLP samples expressed the protein. No COX-2 protein was detectable with Western blot.

CONCLUSION

Increased expression of COX-2 and decreased expression of miR-26b in OLP suggests both to play a role in OLP. COX-2 has been connected to both malignant development and autoimmunity but as malignant development of OLP is quite rare we suggest that the increased levels of COX-2 seen here support an autoimmune cause of the disease.

miRNA analysis of formalin-fixed squamous cell carcinomas of the tongue is affected by age of the samples

Global miRNA expression arrays were used for analysis of 836 miRNAs in formalin-fixed paraffin-embedded samples from 21 tongue cancer patients and 8 controls. Samples had been stored for one to eleven years. Results separated tumour samples from controls, however, the largest variation was correlated to sample storage time, detectable already after one year. With the use of a linear regression model we could adjust for the storage-dependent effect, leading to the identification of 54 differentially expressed miRNAs in tongue cancer, compared to 16 when using standard normalization, including up-regulation of a novel miRNA, miR-424.

Scandinavian Fellowship for Oral Pathology and Oral Medicine: statement on oral pathology and oral medicine in the European Dental Curriculum

BACKGROUND

For many years, dentists have migrated between the Scandinavian countries without an intentionally harmonized dental education. The free movement of the workforce in the European Union has clarified that a certain degree of standardization or harmonization of the European higher education acts, including the dental education, is required. As a result of the Bologna process, the Association for Dental Education in Europe and the thematic network DentEd have generated guidelines in the document 'Profile and Competences for the European Dentist' (PCD). This document is meant to act as the leading source in revisions of dental curricula throughout Europe converging towards a European Dental Curriculum. In order to render the best conditions for future curriculum revisions providing the best quality dentist we feel obliged to analyse and comment the outlines of oral pathology and oral medicine in the PCD.

METHODS

The representatives agreed upon definitions of oral pathology and oral medicine, and competences in oral pathology and oral medicine that a contemporary European dentist should master. The competences directly related to oral pathology and oral medicine were identified, within the PCD.

RESULTS

The subject representatives suggested eighteen additions and two rewordings of the PCD, which all were substantiated by thorough argumentation.

PERSPECTIVES

Hopefully, this contribution will find support in future revisions of the PCD in order to secure the best quality dental education.

Increased expression of Smad proteins, and in particular Smad3, in oral lichen planus compared to normal oral mucosa

BACKGROUND

Oral lichen planus (OLP) is a chronic inflammatory disease of the oral mucosa which the World Health Organisation (WHO) considers a premalignant condition. One step in malignant development is so called epithelial mesenchymal transition (EMT), a process whereby epithelial cells acquire mesenchymal characteristics. EMT occurs during embryogenesis and wound healing but also in some human diseases such as cancer and fibrosis. A factor known to induce EMT is transforming growth factor-β (TGF-β), which uses the Smad proteins as mediators for its signalling. TGF-β is also often over-expressed in squamous cell carcinoma of the head and neck (SCCHN).

METHODS

In the present study we mapped expression of Smad proteins in OLP lesions by immunohistochemistry, and compared to expression in normal and sensitive oral mucosa. The latter group of patients had developed SCCHN after shorter or longer periods of diffuse oral symptoms. The aim was to see if there were any signs of EMT related changes in the OLP lesions, as judged by changes in the TGF-β pathway.

CONCLUSION

Changes in the TGF-β pathway related to EMT are seen in the very earliest stages of oral malignancy and become more severe as lesions progress.

DeltaNp63 isoforms regulate CD44 and keratins 4, 6, 14 and 19 in squamous cell carcinoma of head and neck

The human p63 gene codes for multiple protein isoforms and is commonly over-expressed in squamous cell carcinoma of head and neck (SCCHN). This expression is predominantly of the DeltaN- and beta-isoforms, the former lacking the p53-related transactivation domain. p63 can activate or repress transcription of p53 and p73 target genes, but also has unique transcriptional targets and, unlike other p53 family members, is required for normal development and differentiation of squamous epithelia. We have identified novel targets of p63, using microarray analysis of SCCHN cells that stably over-express individual DeltaNp63 isoforms. All three isoforms induced expression of the cancer stem cell marker, CD44, with the DeltaNp63beta isoform showing strongest induction. Using chromatin immunoprecipitation, we were unable to show direct binding of p63 to the CD44 promoter, but found that p63 specifically increased expression of CD44 lacking variant exon 2. Each of the DeltaNp63 isoforms up-regulated expression of keratins 6A and 14 and down-regulated expression of keratins 4 and 19, in keeping with their expression patterns in SCCHN. The data strengthen the idea that p63 has key roles in regulating normal and abnormal differentiation processes through both induction and repression of genes with opposite functions. The identification of up-regulation and differential splicing of CD44 following p63 over-expression indicates roles in the regulation of adhesion, metastasis and the cancer stem cell phenotype.

Differential Expression of p73?? in Normal Ectocervical Epithelium, Cervical Intraepithelial Neoplasia, and Invasive Squamous Cell Carcinoma

The TP73 gene is a member of the p53 family and through differential promoter usage and alternative splicing can encode a number of different isoforms that have distinct properties. p73 proteins are widely expressed in neural, epithelial, and hemopoietic cells and are proposed to have roles in the development and differentiation of various cell types and in tumorigenesis. The authors have developed a novel monoclonal antibody that is specific for p73alpha to study the expression of this individual isoform in normal and neoplastic cervical epithelium. In normal epithelium, p73alpha is restricted to nonproliferating cells at the base of the epithelium, whereas other p73 isoforms are found in the proliferative zones higher up in the epithelium. In cervical cancers, p73alpha expression is commonly lost, although other p73 isoforms are present at high levels. In particular, the authors found that invasive islands lose p73alpha expression when compared with the overlying intraepithelial lesion. These results show a tight regulation of p73 isoform expression in cervical epithelium and imply that different isoforms of p73 enhance or suppress neoplastic cell growth. These data raise the possibility that reactivation of p73alpha might be beneficial in cervical carcinoma. In addition, the absence of p73alpha in cervical cancer represents a potentially useful tool for the diagnosis of this disease.

Expression of p53, PCNA, Ki-67 and bcl-2 in relation to risk factors in oral cancer - a molecular epidemiological study

A group of 133 primary oral squamous cell carcinomas were studied concerning a relationship between exposure factors and tumour biological parameters with a focus on the TP53 gene and p53 protein status. Tumours were evaluated using immunohistochemistry (IHC) for expression of p53, PCNA, Ki-67 and bcl-2 proteins. The TP53 gene was studied for mutations using PCR amplification of exons 5-9 and single strand conformation polymorphism (SSCP) analysis. The collected data were correlated to the exposure factors smoking, oral snuff, liquor, oral infections, dental factors, dental X-ray and iron deficiency. When compared with matched controls only oral infections, and reported HSV-infections in particular, gave statistically significant ORs (odds ratio) for all tumours (OR 8.0) as well as for the group of IHC p53 positive tumours (OR 12). No association between smoking and p53 positivity was found (OR 1.0).

p53 expression in correlation to clinical outcome in patients with renal cell carcinoma

OBJECTIVE

The aim of this study was to evaluate the role of p53 as prognostic factor in renal cell carcinoma (RCC) and its relation to clinicopathological factors.

MATERIAL AND METHODS

The nuclear accumulation of p53 protein was determined by immunohistochemical analysis in RCC specimens from 90 patients and was correlated with clinical stage, grade, DNA ploidy, S-phase fraction and cancer-specific survival.

RESULTS

p53 overexpression was observed in 17 of 90 (19%) tumours. There was a significant correlation to stage (p = 0.016) and grade (p = 0.020) but not to DNA ploidy or S-phase. Patients with high p53 immunoreactivity had shorter cancer-specific survival (p = 0.003) than those with normal p53 protein expression. This difference was found in papillary and chromophobe tumour types (p < 0.0001) but not in conventional RCC.

CONCLUSIONS

In patients with RCC, significant correlations between p53 protein expression and tumour stage, grade and survival time were observed. For patients with chromophobe and papillary tumour types, but not in conventional RCC, p53 immunoreactivity gave prognostic information, suggesting that the prognostic differences in p53 immunoreactivity might be due to disparate genetic abnormalities in the different RCC types.

The p53 molecule and its prognostic role in squamous cell carcinomas of the head and neck

Despite intense research, the 5-year survival rate for patients with squamous cell carcinoma of the head and neck (SCCHN) is still low. Several different factors have been studied in the search for one or more factors that give important prognostic information at the time of diagnosis. Many recent studies have focused on the TP53 tumour suppressor gene, analysing its gene status and protein status. When looking at p53 protein expression, using immunohistochemistry, no correlation to patient outcome has been seen for the whole group of SCCHN. However, a significant association between p53 expression and poor patient outcome was found when looking only at patients with laryngeal squamous cell carcinomas. Also, in oral premalignant lesions, expression of p53-positive cells in the suprabasal layers of the epithelium has been seen as an indication of impending malignant development. Concerning the prognostic significance of mutations in the TP53 gene, results differ. But when restricting analysis to tumours with mutations causing an obvious change in protein, TP53 mutation was found to be a strong and independent variable for prognosticating survival. This review article gives an up-to-date overview of the p53 molecule and evaluates its possible prognostic role in SCCHN. Today it is clear that the p53 pathway is very important in SCCHN biology and potentially in its treatment. The function and importance of a few other cell cycle proteins connected to p53 are also discussed.

Characterization of the expression pattern of p63 alpha and delta Np63 alpha in benign and malignant oral epithelial lesions

The p53 homologue p63 is essential for ectodermal differentiation, such that p63-/- mice lack all squamous epithelia and teeth. The p63 gene expresses at least 6 different transcripts, but information regarding the expression, regulation and function of the different isoforms has remained sparse, due to the lack of adequate reagents directed specifically against the individual proteins. Here we characterize the expression of p63 alpha/delta Np63 alpha in benign and malignant lesions of the oral epithelium, using a specific antibody raised against a peptide derived from the C-terminus of p63 alpha, which does not cross-react with p53 or the other p53 homologue, p73. By immunohistochemical analysis, we show that these p63 isoforms are expressed in the nucleus of many cells. In normal and benign lesions, p63 alpha/delta Np63 alpha-expressing cells are mainly found suprabasally, whereas p53-expressing cells are restricted to the basal-cell layer. By RT-PCR, we show that delta Np63 alpha is the predominant isoform in cell lines from squamous-cell carcinomas of the head and neck, confirming our immunochemical observations. Our data are consistent with studies suggesting a role for p63 in the transit-amplifying population of epidermal cells. Over-expression of p63 alpha, and in particular the delta N form, was frequently seen in carcinomas. Taken together with previous analyses of p63 expression, our data suggest distinct roles for different p63 isoforms in the regulation of growth and/or differentiation of epithelial cells. Moreover, our data are compatible with the notion that p63 can act to promote neoplastic growth in the oral epithelium.

Expression of the p53 homologue p63alpha and deltaNp63alpha in normal and neoplastic cells

A burgeoning family of p53-related genes have been described recently, including p73 and p63. Both these genes encode proteins with many similarities to p53 but also with the potential for forming a range of related species by alternative promoter usage and alternative splicing. In order to begin the characterization of p63, we generated a polyclonal serum (designated SC1) that recognizes the C-terminus of p63alpha. We have shown that this reagent recognizes p63alpha but not p53 nor p73. By western blot analysis both p63alpha and the N-terminal truncated form of p63alpha (DeltaNp63alpha) were found in a range of cell lines. Similar immunoblot analysis of tissues reveals considerable complexity with at least four SC1-immunoreactive isoforms being identified. In immunohistological studies SC1 immunoreactivity is widely detectable, being predominantly associated with proliferative compartments in epithelia. However, non-proliferative populations can also show SC1 immunostaining. No simple relationship between the isoforms identified by immunoblotting of tissue lysates and the tissue immunostaining characteristics was identified. A previously unrecognized species intermediate in mobility between p63alpha and DeltaNp63alpha was found in several tissues, including nerve and peripheral blood lymphocytes. Interestingly, there is suppression of p63alpha expression in HaCat cells in a time- and concentration-dependent manner after UV and MMS treatment. Our data provide further information about the complexity of p63 and the SC1 serum will prove to be a useful tool in further studies of this p53 homologue.

Transcriptional activation of tyrosinase and TRP-1 by p53 links UV irradiation to the protective tanning response

We are exposed constantly to potentially harmful compounds and radiations. Complex adaptive protective responses have evolved to prevent such agents causing cellular damage, including potentially oncogenic mutation. The p53 tumour suppressor appears to have a role in co-ordinating such responses: it is activated by diverse insults and it acts as a transcriptional regulator of downstream genes that facilitate cellular adaptation. Ultraviolet (UV) light is a particularly potent inducer of p53 expression. In addition, UV light induces the production of melanin as a protection against further irradiation-induced damage. This study shows that the promoters of the genes coding for the enzymes crucial in melanin biosynthesis, namely tyrosinase and tyrosinase-related protein-1 (TRP-1), are activated by wild-type p53. Both promoters have p53-responsive elements and are activated in vivo in a dose-dependent manner by wild-type p53, as well as by the p53 homologues p73alpha and p63alpha.

Temporomandibular joint condyle changes after surgically induced non-reducing disk displacement in rabbits: a macroscopic and microscopic study

Experimentally induced displacement of the temporomandibular joint (TMJ) disk has previously been shown to induce shortening of the mandibular ramus on the ipsilateral side. The aim of this investigation was to reveal whether this shortening develops due to primary influence on condyle growth or by secondary loss of condyle mass due to degenerative tissue breakdown. Disk displacement was created in the right TMJ in seven 3-month-old rabbits, the posterior disk attachment kept intact. Seven rabbits underwent surgical opening of the TMJ without disk intervention. Seven additional animals served as references. After a 3-month experimental period, the animals were sacrificed. Previous analysis revealed shortening of mandibular height and length caused by ipsilateral TMJ disk displacement. The condyles were examined macroscopically and by histologic sectioning or scanning electron microscopy. All condyles were covered with smooth articulating soft tissue and without visible signs of degenerative changes. Four condyles from joints with disk displacement demonstrated substantial regressive remodeling resulting in a change of condyle shape with forward/downward rotation of an enlarged articulating surface. It was concluded that TMJ disk displacement in a growing individual can induce reduction of mandibular height and length before a stage where visible osteoarthrotic changes develop. It implies a primary adverse effect on condyle growth.

Why is p53 protein stabilized in neoplasia? Some answers but many more questions?

The p53 pathway provides a physiological system for integrating signals from diverse insults and eliciting adaptive cellular responses that include (but importantly are not restricted to) growth arrest and apoptosis. Defects in the pathway are prevalent in cancer, most notably being associated with mis-sense mutations in p53 itself. This leads to the inability of p53 to act as a transcription factor and thus to the non-occurrence of downstream events. Recent data indicate that the stability (and hence level) of p53 protein in cells is regulated by its interaction with mdm2: this results in enhanced p53 degradation by ubiquitin-mediated events. Since mdm2 is itself regulated by p53, loss of function of p53 leads to lack of mdm2 and thus to p53 protein accumulation. This provides a mechanistic explanation for the observation that p53 accumulation is associated with neoplasia. It may be that accumulation of p53 in the absence of p53 mutation can occur as a consequence of mdm2 defects, as well as being a physiological response in many situations. Another recent development is the recognition of p53 homologues (p73 alpha, p73 beta, and KET) which have many sequence and probable structural features in common with p53. It seems likely that this will reveal another layer of complexity in the control and regulation of p53 and its role in physiology and pathology.

PCNA, Ki-67, p53, bcl-2 and prognosis in intraoral squamous cell carcinoma of the head and neck

Eighty patients with primary intraoral squamous cell carcinomas of the head and neck, with a follow-up of 4-14 years were analysed for clinical outcome in relation to immunohistochemical expression of PCNA, Ki-67, p53, bcl-2 and presence of mutations in the p53 gene. The tumor site was not associated with the different parameters calculated. PCNA and Ki-67 labelling showed median values of 56% and 32%, respectively, and neither antigen was of predictive value. Fifty-five percent of the tumours expressed p53, and 38 (48%) had mutations in the p53 gene. No association between the presence of p53 protein or mutations in the p53 gene and clinical outcome was found. Bcl-2 positivity was detected in a minor fraction (10%) of the tumours.

A non-random deletion in the p53 gene in oral squamous cell carcinoma

In a retrospective study of the mutational spectrum of the p53 gene in oral squamous cell carcinoma, 80 primary tumours diagnosed in 1980-90 were included. Using polymerase chain reaction/single strand conformation polymorphism (PCR/SSCP) analysis 47 mutations were found distributed in 39 of the tumours (49%). Unexpectedly, the majority of the mutations (29/47; 62%) were found in exon 8, and at sequencing 17 of them showed a 14 bp deletion in codons 287-292, causing formation of a stop codon and accordingly a truncated protein lacking the C-terminal. The majority of the patients with the 14 bp deletion were women (13/17), and it seemed as though certain potential risk factors for carcinoma of the head and neck were less common in this group.

p53 mutations, protein expression and cell proliferation in squamous cell carcinomas of the head and neck

Thirty-three patients with squamous cell carcinoma of the head and neck region were studied concerning p53 protein expression and mutations in exons 4-9 of the p53 gene using immunohistochemistry, polymerase chain reaction (PCR)-single strand conformation polymorphism analysis and DNA sequencing. Immunoreactivity was found in 64% and p53 gene mutations in 39% of the tumours. Thirty-three per cent of the immunopositive and 50% of the immunonegative tumours were mutated within exons 5-8. In one immunopositive tumour three variants of deletions were observed. Sequencing of the p53 mutated, immunonegative tumours revealed four cases with deletions, one case with a transversion resulting in a stop codon and one case with a splice site mutation which could result in omission of the following exon at splicing. All mutations in the immunonegative tumours resulted in a truncated p53 protein. No association between p53 gene status and expression of proliferating cell nuclear antigen (PCNA) or cell proliferation as judged by in vivo incorporation of the thymidine analogue iododeoxyuridine (IdUrd) was found.

Immunohistochemical detection of oncoprotein 18 (Op18) in malignant lymphomas

Expression of oncoprotein 18 (Op18), an intracellular phosphoprotein up-regulated in many malignant cell types, was evaluated in a series of normal lymphoid tissue and malignant lymphomas. In normal tonsils and reactive lymph nodes, the majority of Op18-positive cells were present in the germinal centres, whereas cells in the mantle zone were essentially negative and the interfollicular areas showed occasional positive cells. Double staining for PCNA and Op18 revealed that Op18 expression only to some extent was correlated with cell proliferation, as determined by PCNA expression. Non-Hodgkin's lymphomas exhibited a variable Op18 expression, and in Hodgkin's disease, Reed-Sternberg and Hodgkin cells frequently expressed Op18 with a strong staining intensity. Using Op18-PCNA double staining in malignant lymphomas, Op18 expression could also be partially dissociated from cell proliferation. By using confocal microscopy, the intracellular localization of Op18 was studied, demonstrating diffuse reactivity in the cytoplasm in interphase cells and during mitosis, whereas nuclei and condensed chromosomes were negative. In conclusion, Op18 was expressed at variable levels in most, perhaps all, proliferating lymphocytes in benign lymphoid tissue as well as in malignant lymphomas. However, the Op18 protein was also detected in a significant fraction of apparently non-cycling normal and neoplastic lymphocytes.

p53 expression and cell proliferation in squamous cell carcinomas of the head and neck

BACKGROUND

In squamous cell carcinoma of the head and neck (SCCHN), overexpression of the p53 protein has been found in 34-80% of the tumors studied. No data are available regarding p53 expression versus tumor cell proliferation and prognosis for this tumor type.

METHODS

p53 protein levels were studied by immunohistochemical staining of 33 primary SCCHN using 3 antibodies (DO7, PAb 1801, and CM1) that react with different epitopes of the p53 protein. The cellular expression of p53 was compared with in vivo incorporation of the thymidine analog iododeoxyuridine (IdUrd) and expression of proliferating cell nuclear antigen (PCNA).

RESULTS

Twenty-one tumors (64%) had a positive nuclear staining for p53 with the monoclonal antibody DO7, which reacts with a denaturation-resistant epitope in wild-type and mutant p53. PAb 1801 and CM1 reacted with 19 and 20 tumors, respectively, all of which were DO7-positive. No correlation was found between incorporation of IdUrd and p53 expression or between PCNA and p53 expression. The data indicate that intracellular accumulation of the p53 protein was related to tumor stage and localization of the tumor. No indication of a clinical or prognostic significance of p53 expression in SCCHN was found.

CONCLUSIONS

No association between p53 deregulation and tumor cell proliferation was found.

Application of dual parameter analysis in flow cytometric DNA measurements of paraffin-embedded samples

In a comparison of flow cytometric DNA measurements on fresh and paraffin-embedded material from primary squamous cell carcinomas of the head and neck region, we discovered that previously undetected aneuploid clones could be detected by dual parameter analysis of cytokeratin and DNA applied to disintegrated cells from paraffin sections. Using this new approach the correlation coefficient between DNA-indices from fresh and paraffin-embedded material increased from 0.423 to 0.904.

Cell-cycle-regulated phosphorylation of oncoprotein 18 on Ser16, Ser25 and Ser38

Oncoprotein 18 (Op18) has been independently identified due to its increased phosphorylation in response to external signals and its up-regulated expression in acute leukemia. We have identified two serine residues of Op18 that are phosphorylated after triggering by the T cell antigen receptor. One of these residues, Ser25, was shown to be a likely substrate for the mitogen-activated protein (MAP) kinase, while the other residue, Ser16, was shown to be phosphorylated in response to increased intracellular calcium. Our previous site-mapping studies of Op18 also revealed that basal phosphorylation of Op18 is mainly located on Ser38, which was found to be the primary in vitro phosphorylation site of p13suc1-precipitated cdc2 kinase activities. These findings raised the possibility that Op18 may be a substrate for both receptor-regulated calcium-induced protein kinases and the MAP kinase family, as well as being a substrate for the cell-cycle-regulated cdc2 kinase family. In the present report we have performed site-mapping studies of cell-cycle-regulated fluctuations of Op18 phosphorylation. The results reveal that S-phase progression of a synchronised leukemic T cell line is associated with increased phosphorylation of both the Ser25 and Ser38 residues. Moreover, during mitosis, a burst of phosphorylation was observed and at this stage of the cell cycle a major fraction of Op18 was phosphorylated at multiple sites. Phosphorylation of Op18 during mitosis was located primarily on Ser38 and to lesser extent on Ser25, Ser16 and at an unidentified C-terminal residue. In vitro phosphorylation experiments, employing two distinct members of the cdc2 kinase family, were consistent with involvement of both p34-cdc2 and p33-cdk2 in cell-cycle-regulated phosphorylation of Ser25 and Ser38 of Op18. Most importantly, the ratio of Ser25/Ser38 phosphorylation observed in vitro, using either p34-cdc2 or p33-cdk2, was found to be the same as the ratio observed in intact cells during all phases of the cell cycle. These findings suggest that Op18 may be a physiological substrate for several members of the cdc2 kinase family during both the S-phase and the mitotic phase of the cell cycle.

Cell kinetics of head and neck squamous cell carcinomas. Prognostic implications

Forty-three squamous cell carcinomas of the head and neck region were in vivo labelled with the thymidine analogue iododeoxyuridine. Combined flow cytometric (FCM) and immunohistochemical (IHC) analysis was performed, and the following parameters calculated: labelling index (LI), S-phase time (TS) and potential tumor doubling time (Tpot). Complete FCM and IHC analyses could successfully be performed in 31 cases, showing a median LI of 13.6% with FCM and 9.1% with IHC. A correlation achieved between LI/FCM and LI/IHC was due to the aneuploid cases, whereas the diploid cases showed no such correlation. Data indicated that Tpot calculated with LI from IHC (Tpot/IHC) might be a prognostic factor, in contrast to Tpot determined using LI/FCM.

Expression of the endothelial leukocyte adhesion molecule-1 (ELAM-1) on endothelial cells in experimental gingivitis in humans

In inflammatory conditions, mediators such as interleukin-1 (IL-1) are released by resident tissue cells as well as by infiltrating inflammatory cells. IL-1 activates endothelial cells causing them to express an adhesion molecule called endothelial leukocyte adhesion molecule-1 (ELAM-1). IL-1 is produced by macrophages, but can also be produced by activated keratinocytes. Here we present data from a study of experimentally induced gingivitis, showing the expression of ELAM-1 on endothelial cells even in tissue with little or only minor signs of clinical or histological inflammation. These results indicate that ELAM-1 is found on endothelial cells of the gingiva early in the course of experimental gingivitis, before overt clinical or histological evidence of inflammation is apparent.

The ELAM-1 ligand sialosyl-Le(X) is present on Langerhans cells isolated from stratified epithelium

In this study we show the expression of the newly identified carbohydrate ligand, sialosyl-Le(X) on Langerhans cells. The receptor for sialosyl-Le(X) is the endothelial leukocyte adhesion molecule-1 (ELAM-1) present on activated endothelial cells. Using flow cytometry, Langerhans cells were selected due to positivity for an antibody against CD1a and low orthogonal light scatter. The CD1a antigen stained by the OKT6 antibody is considered a maturational marker of Langerhans cells in agreement with the specific labeling of dendritic cells in the epithelium only. Double immunostaining (OKT6/anti-sialosyl-Le(X)) using flow cytometry and immunohistochemistry demonstrated that almost all OKT6-positive cells in normal stratified epithelium expressed sialosyl-Le(X). Conversely, by immunohistochemistry of oral epithelium with acute inflammation, additional dendritic cells negative for OKT6 were found to express sialosyl-Le(X). In addition, sialosyl-Le(X)-positive but not OKT6-positive dendritic cells were found in the submucosa. These findings indicate that the carbohydrate antigen sialosyl-Le(X) is expressed earlier than the CD1a antigen in the maturation of the Langerhans cell lineage. Future studies should aim at investigating the importance of adhesion between sialosyl Le(X) and ELAM-1 in epithelial recruitment of Langerhans cells.