p53 gene mutations in oropharyngeal carcinomas: a comparison of solitary and multiple primary tumours and lymph-node metastases

Clinical and pathological correlation of P53 expression in oral cancers

In our study, we aimed to evaluate the overexpression of P53 in 155 oral squamous cell carcinomas and to correlate with various clinicopathological features like depth of invasion, lymph nodal involvement, and margin status, which affect the local recurrence and prognosis. This cross-sectional study included 155 oral squamous cell carcinoma patients who underwent surgical resection of primary and nodal disease. The histopathological and clinical features were noted. Immunohistochemical expression was reported, and other clinicopathological features were correlated. Statistical analysis was performed using SPSS software. In the present study, out of 155 patients, 127(81.9%) are males, and the majority are more than 50 years (55%). The most common site of oral carcinoma is the tongue, followed by buccal mucosa. An aberrant or mutational type of P53 was seen in 90 cases (58%), while the wild type was observed in 65 patients (42%). Expression of P53 is not similar in different sites of the oral cavity but is more frequently seen in the Gingiva, followed by retromolar trigone, lip, buccal mucosa, and tongue. There is a significant association between P53 expression and degree of tumor differentiation, T staging, and depth of invasion, involved margin, node positivity, and extranodal extension.

Role of E2F transcription factor in Oral cancer: Recent Insight and Advancements

The family of mammalian E2F transcription factors (E2Fs) comprise of 8 members (E2F1-E2F8) classified as activators (E2F1-E2F3) and repressors (E2F4-E2F8) primarily regulating the expression of several genes related to cell proliferation, apoptosis and differentiation, mainly in a cell cycle-dependent manner. E2F activity is frequently controlled via the retinoblastoma protein (pRb), cyclins, p53 and the ubiquitin-proteasome pathway. Additionally, genetic or epigenetic changes result in the deregulation of E2F family genes expression altering S phase entry and apoptosis, an important hallmark for the onset and development of cancer. Although studies reveal E2Fs to be involved in several human malignancies, the mechanisms underlying the role of E2Fs in oral cancer lies nascent and needs further investigations. This review focuses on the role of E2Fs in oral cancer and the etiological factors regulating E2Fs activity, which in turn transcriptionally control the expression of their target genes, thus contributing to cell proliferation, metastasis, and drug/therapy resistance. Further, we will discuss therapeutic strategies for E2Fs, which may prevent oral tumor growth, metastasis, and drug resistance.

Detection of p53 mutations in proliferating vascular cells in glioblastoma multiforme

OBJECT

Glioblastoma multiforme (GBM), one of the most aggressive tumors in humans, is highly angiogenic. However, treatment with the angiogenesis inhibitor bevacizumab has not significantly prolonged overall patient survival times. GBM resistance to angiogenesis inhibitors is attributed to multiple interacting mechanisms. Although mesenchymal transition via glioma stem-like cells has attracted attention, it is considered a poor biomarker. There is no simple method for differentiating tumor-derived and reactive vascular cells from normal cells. The authors attempted to detect the mesenchymal transition of tumor cells by means of p53 and isocitrate dehydrogenase 1 (IDH1) immunohistochemistry.

METHODS

Using antibody against p53 and IDH1 R132H, the authors immunohistochemically analyzed GBM tissue from patients who had undergone surgery at the University of Miyazaki Hospital during August 2005–December 2011. They focused on microvascular proliferation with a p53-positive ratio exceeding 50%. They compared TP53 mutations in original tumor tissues and in p53-positive and p53-negative microvascular proliferation cells collected by laser microdissection.

RESULTS

Among 61 enrolled GBM patients, the first screening step (immunostaining) identified 46 GBMs as p53 positive, 3 of which manifested areas of prominent p53-positive microvascular proliferation (> 50%). Histologically, areas of p53-positive microvascular proliferation tended to be clustered, and they coexisted with areas of p53-negative microvascular proliferation. Both types of microvascular proliferation cells were clearly separated from original tumor cells by glial fibrillary acidic protein, epidermal growth factor receptor, and low-/high-molecular-weight cytokeratin. DNA sequencing analysis disclosed that p53-positive microvascular proliferation cells exhibited TP53 mutations identical to those observed in the original tumor; p53-negative microvascular proliferation cells contained a normal allele. Although immunostaining indicated that 3 (2 primary and 1 secondary) of the 61 GBMs were positive for IDH1, no tumors contained microvascular proliferation cells positive for IDH1 R132H.

CONCLUSIONS

Some microvascular proliferation clusters in GBM result from mesenchymal transition. The identification of useful markers might reveal this phenomenon as an infrequent event in GBMs.

Clonality analysis in primary oral squamous cell carcinoma and related lymph-node metastasis revealed by TP53 and mitochondrial DNA next generation sequencing analysis

The chance of developing a neck nodal metastasis after initial treatment of oral squamous cell carcinoma varies from 12.4% to 62%. Despite being the main reason for cancer-related mortality, nodal metastases are still rarely subjected to molecular analyses, and our knowledge of the clonal heterogeneity of multiple lesions within the same patient is limited. The aim of the present study was to evaluate the relationship between primary oral cancer and lymph node metastasis in a series of patients with synchronous and metachronous metastases by 2 clonality tests: mt-DNA and TP53 sequence analysis. The study population consisted of 10 consecutive patients. Data identified in this study demonstrate that our assay based on next-generation analysis of TP53 and mt-DNA is simple, is reliable, allows high throughput, and may be applied to retrospective cases. The combination of mt-DNA and TP53 data analysis helped us to evaluate more precisely and consistently the genetic relationship among different tumor clones.

Cell cycle dysregulation in oral cancer

The dysregulation of the molecular events governing cell cycle control is emerging as a central theme of oral carcinogenesis. Regulatory pathways responding to extracellular signaling or intracellular stress and DNA damage converge on the cell cycle apparatus. Abrogation of mitogenic and anti-mitogenic response regulatory proteins, such as the retinoblastoma tumor suppressor protein (pRB), cyclin D1, cyclin-dependent kinase (CDK) 6, and CDK inhibitors (p21(WAF1/CIP1), p27(KIP1), and p16(INK4a)), occur frequently in human oral cancers. Cellular responses to metabolic stress or genomic damage through p53 and related pathways that block cell cycle progression are also altered during oral carcinogenesis. In addition, new pathways and cell cycle regulatory proteins, such as p12(DOC-1), are being discovered. The multistep process of oral carcinogenesis likely involves functional alteration of cell cycle regulatory members combined with escape from cellular senescence and apoptotic signaling pathways. Detailing the molecular alterations and understanding the functional consequences of the dysregulation of the cell cycle apparatus in the malignant oral keratinocyte will uncover novel diagnostic and therapeutic approaches.

HPV subtypes in cervical cancer biopsies between 1930 and 2004: detection using general primer pair PCR and sequencing

Our objective was to investigate the practicability of sequencing DNA from formalin fixed, paraffin embedded tissue stored for up to 75 years and to study human papillomavirus subtype distribution in cervical neoplasias between 1931 and 2004. Three protocols for DNA retrieval were tested, and magnetic bead DNA extraction proved advantageous, as it gave superior specimen purity and effortless sequencing. Successful sequencing was achieved in more than 70% of the specimens from 1931 to 1960. This technique was utilized in the study of papillomavirus subtypes using general primer pair PCR with sequencing of the products in a series of 97 cases of neoplastic and non-neoplastic cervical specimens from 1931 to 1960 and 73 similar cases from 1992 to 2004. HPV was detected in 61% of neoplastic specimens from 1931 to 1960, and in 89% of those from 1992 to 2004. In specimens from 1931 to 1934, only HPV type 16 was detected, whereas in the specimens from 1940 and up, other HPV subtypes were identified in one-third of the cases. The difference was significant and suggests an increase in papillomavirus subtype heterogeneity in Western Norway during 1930-2000. The results strongly support the feasibility of using DNA from paraffin-embedded specimens for studying cancer etiology and genotypes over extended time periods.

Comparison of HPV infection, p53 mutation and allelic losses in post-transplant and non-posttransplant oral squamous cell carcinomas

BACKGROUND

Oral squamous cell carcinoma (SCC) is increasingly found in transplant recipients, although little is known of the natural history of the disease or the mechanism underlying this increase.

METHODS

In this article we describe the history of development of 5 oral post-transplant SCCs (PSCCs) and compare their genetic profiles to 34 non-posttransplant SCCs (NPSCCs).

RESULTS

Of the five patients with PSCCs, 3 had bone marrow transplants and two, kidney. All three PSCCs from bone marrow recipients were preceded locally by graft-vs.-host disease (GVHD). Two of the GVHD were biopsied and demonstrated dysplasia. Similar frequencies of loss of heterozygosity (LOH) occurred in PSCCs and NPSCCs at 3p, 9p, 17p and 8p, with lower frequencies in PSCCs at 4q (39% vs. 0%), 11q (53% vs. 20%) and 13q (45% vs. 20%), although the latter were not significantly different. Only 1 PSCC had a p53 mutation, compared to historical values of 40-60% for NPSCC. Interestingly, human papillomavirus (HPV) DNA was detected in 3 (60%) PSCCs, in comparison to only 4 (12%) of the 34 NPSCCs (P = 0.0346).

CONCLUSIONS

Dysplasia in oral GVHD may be a strong indicator of cancer risk and should not be regarded as reactive changes to lichenoid mucosites. The low level of p53 mutation and increased HPV infection support the involvement of HPV in the development of PSCC, while the similarity in LOH patterns suggests that other aspects of carcinogenesis may be comparable in these two types of SCCs.

Neurofibromatosis type 1-associated unusual pleomorphic astrocytoma displaying continual malignant progression

Patients with neurofibromatosis type 1 (NF1) often have gliomas as a complication, most of which are benign pilocytic astrocytomas which have arisen in optic pathways. In the present case, a 17-year-old girl (at death) with stigmata of NF1, initially had a bulky tumor mass in the left thalamus, developing into the lateral ventricle, at 13 years of age. Partially resected tissue samples showed pleomorphic astrocytoma with abundant xanthoma cells and degenerative structures such as Rosenthal fibers (RF) and eosinophilic granular bodies. Fine eosinophilic granules identical to RF, both immunophenotypically and ultrastructurally, were also seen. The residual tumor was subtotally resected 6 months later, and the tumor histology was essentially similar as before, accompanying the regenerative structures; this was believed to be a good prognostic indicator. However, several anaplastic features such as mitosis, necrosis and vascular proliferation appeared even in areas rich in the regenerative structures. After a 2-year, disease-free interval, multiple tumor relapse occurred in June 1997. Partially resected tumor tissues were composed of monotonous small anaplastic cells with prominent proliferative activity. Surprisingly, the tumor cells had retained eosinophilic granules within the cell bodies. Postoperative chemotherapy with procarbazine, MCNU and vincristine (PCV) suppressed the residual tumor dramatically, but the regrowing tumor finally became uncontrollable, leading to the patient's death. TP53 mutation was not detected, while p27 immunopositivity was constantly high during malignant progression, suggesting acquisition of proliferative activity to overcome p53 and p27 inhibitory functions. A review of previously published reports failed to reveal any cases of this type.

New therapeutic strategies for the treatment and prevention of head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is an aggressive epithelial malignancy that is now the sixth most common neoplasm in the world today. Approximately 50,000 cases in the United States and more than 500,000 cases worldwide will be diagnosed in 2000 [1]. Despite numerous advances in treatment utilising the most recent protocols for surgery, radiation and chemotherapy, the long-term survival has remained at less than 50% over the past 40 years [2]. This poor long-term survival is due to a number of variables including delayed diagnosis as well as the frequent development of multiple primary tumours. Therefore, in addition to early detection, continued emphasis must be placed on preventing the development of new primaries as well as establishing more effective treatments for individuals who present with advanced disease. This review will summarise some of the recent advances in the realms of chemotherapy and radiation therapy. In addition, it will discuss the present status of chemoprevention in HNSCC. Finally, we will discuss the rationale for the use of anti-angiogenic agents as one possible means of developing new chemopreventive protocols that result in reduced toxicity while maintaining similar clinical efficacies.

Genetic aberrations in oral or head and neck squamous cell carcinoma 3: clinico-pathological applications

The molecular changes in malignant epithelium in the head and neck offer possibilities for the development of diagnostic, prognostic and other markers. This article reviews recent developments in this field.

Investigation of germline PTEN, p53, p16(INK4A)/p14(ARF), and CDK4 alterations in familial glioma

Epidemiological studies suggest that some familial aggregations of glioma may be due to inherited predisposition. Many genes involved in familial cancers are frequently altered in the corresponding sporadic forms. We have investigated several genes known to be altered in sporadic gliomas for their potential contribution to familial glioma. Fifteen glioma patients with a family history of brain tumors were identified through the Mayo Clinic Department of Neurology (nine diffuse astrocytomas, two oligodendrogliomas, two mixed oligoastrocytomas, one pilocytic astrocytoma, and one pineal glioma). Eleven of the propositi had one or more first degree relative with a glioma. Lymphocyte DNA was derived from each of the patients and analyzed by polymerase chain reaction (PCR) and direct sequencing of the PTEN, p53, p16(INK4A)/p14(ARF), and CDK4 genes. In addition, fluorescence in situ hybridization (FISH) was performed on EBV-transformed lymphocytes from each affected individual to detect germline copy number of the p16(INK4A)/p14(ARF) tumor suppressor region. A p53 germline point mutation was identified in one family with some findings of Li-Fraumeni syndrome, and a hemizygous germline deletion of the p16(INK4A)/p14(ARF) tumor suppressor region was demonstrated by FISH in a family with history of both astrocytoma and melanoma. Thus, whereas germ-line mutations of PTEN, p53, p16(INK4A)/p14(ARF), and CDK4 are not common events in familial glioma, outside of familial cancer syndromes, point mutations of p53 and hemizygous deletions and other rearrangements of the p16(INK4A)/p14(ARF) tumor suppressor region may account for a subset of familial glioma cases. Collectively, these data lend genetic support to the heritable nature of some cases of glioma.

Proliferative and apoptotic responses in cancers with special reference to oral cancer

The study of signal transduction pathways for mechanisms of apoptosis and proliferation has significantly advanced our understanding of human cancer, subsequently leading to more effective treatments. Discoveries of growth factors and oncogenes, especially those that function through phosphorylation on tyrosine residues, have greatly benefited our appreciation of the biology of cancer. The regulation of proliferation and apoptosis through phosphorylation via tyrosine kinases and phosphatases is discussed, as well as the contributions of other systems, such as serine and threonine kinases and phosphatases. Receptors with seven-transmembrane domains, steroid hormones, genes, and "death domains" will also be discussed. This review attempts to compare the regulation of the growth of normal tissues and cancers with an effort to highlight the current knowledge of these factors in the growth regulation of oral/oropharyngeal cancers. Despite the strides made in our understanding of growth regulation in human cancers, the study of oral/oropharyngeal cancer specifically lags behind. More research must be done to further our understanding of oral cancer biology, if we are to develop better, more effective treatment protocols.

p53 tumor suppressor gene as a clonal marker in head and neck squamous cell carcinoma: p53 mutations in primary tumor and matched lymph node metastases

In order to define the diagnostic value of p53 tumor suppressor gene as a clonal marker in head and neck squamous cell carcinoma (HNSCC), we investigated p53 mutations in primary tumors (PT) and matched lymph node metastases (LNM); the underlying question being whether differentiation between metastatic disease of a known PT or (a metastasis of) a synchronous or metachronous second tumor is possible by means of p53 sequencing-based mutation analysis. In 15 PT, the p53 status was analyzed, following RNA isolation, cDNA synthesis and polymerase chain reaction amplification, by direct sequencing full-length mRNA. Mutations thus found were confirmed by DNA sequencing analysis of the corresponding exon in the PT. When RNA isolation was defective, DNA sequencing analysis of exons 1 through 11 was performed. In the matched LNM, DNA analysis of the corresponding exon was performed to prove the presence of the same p53 mutation. In the event of small clones not detectable by direct sequencing, an oligo ligation assay was developed to detect a specific mutation. The presence of germline mutations was excluded by DNA sequencing analysis of the corresponding exon of peripheral blood leucocytes. In 14 PT (94%), a mutation was identified. In one PT, no p53 mutation could be identified either after full-length mRNA sequencing or after sequencing exons 1 through 11. In all cases of PT and matched LNM, the mutations proved to be identical. We conclude that p53 mutations develop in carcinogenesis before metastases occur and are maintained during metastasis. Consequently, p53 may serve as a clonal marker not susceptible to change during tumor metastasis. This merits further exploration of the application of p53 mutation analysis in differentiating between metastatic disease from a known PT versus a metastasis of another second PT.

Expression of p53 protein and Ki-67 antigen in gingival hyperplasia induced by nifedipine and phenytoin

BACKGROUND

Although it has been thought that drug-induced gingival hyperplasia is not related to tumorigenesis, recent case reports have shown that squamous cell carcinomas may arise in gingival hyperplasia induced by cyclosporin and phenytoin. The possible implications between the pathogenesis of this disease and tumorigenesis have not been elucidated and remain to be studied.

METHODS

We immunohistochemically examined the expression of tumor-related markers such as p53 protein and Ki-67 antigen in 11 hyperplastic gingival tissues induced by nifedipine and phenytoin, as well as 5 control tissues using an avidin-biotin-peroxidase complex method.

RESULTS

Two specimens out of 4 nifedipine-induced and 4 out of 7 phenytoin-induced hyperplastic gingival tissues revealed the expression of p53 protein in the nuclei of epithelial cells, while no expression of p53 protein was observed in the epithelia of the 5 non-hyperplastic control tissues. The immunoreactions against p53 protein showed sporadic distribution in the suprabasal layers of hyperplastic epithelia. The mean percentage of epithelial cells expressing Ki-67 antigen in the hyperplastic gingival tissues was more than 10% higher than that in the controls. The expression of Ki-67 antigen was suppressed in the typical rete pegs deeply elongated into lamina propria of hyperplastic gingival tissues. Intense immunostaining of Ki-67 antigen was found in fibroblasts of hyperplastic gingival tissues, while that of the control tissues was negligible.

CONCLUSIONS

The expression of p53 protein in gingival hyperplasia suggests that the pathogenesis of this disease is involved with impaired DNA, while the growth arrest observed in the hyperplastic epithelia with typically elongated rete pegs as expressed with Ki-67 antigen may prevent the invasive expansion of epithelial cells undergoing DNA damage within gingival tissues and may consequently suppress tumorigenic progression.

TP53 genetic alterations in head-and-neck carcinomas from Brazil

In this study we investigated the incidence of mutations and loss of heterozygosity (LOH) of the TP53 gene in DNA samples from paired tumor and adjacent normal tissue from 90 patients with untreated squamous-cell carcinoma of the head and neck. Evidence for TP53 mutations were demonstrated in 53% (48/90) of the cases analyzed. All cases were also examined for loss of heterozygosity, using a PCR-based polymorphic marker at TP53. LOH was found in 36 out of 72 (50%) informative cases. Direct sequencing of PCR products was performed in 45 cases with evidence of mutations. The sequencing results revealed the presence of base-substitutions (67%), deletions (29%) and insertions (4%). Of the base-substitutions, 70% were transitions and 30% were transversions. Demographic variables, tumor site, stage (TNM), family history of cancer, lymph-node involvement and histological grade were not important predictors of TP53 mutations. Nor did TP53 genetic alterations correlate with survival status. In conclusion, we show that TP53 genetic alterations are frequent in head-and-neck tumors, but are not associated with clinicopathological variables or disease progression. Our study provides an evaluation of the spectrum of TP53 mutations in the pathogenesis of head-and-neck carcinoma in Brazil.

Mutated and wild-type p53 expression and HPV integration in proliferative verrucous leukoplakia and oral squamous cell carcinoma

The frequencies of overexpression and mutation in the p53 tumor suppressor gene were examined in proliferative verrucous leukoplakia and oral squamous cell carcinoma with immunohistochemistry and single-strand conformation polymorphism analysis of DNA fragments amplified by polymerase chain reaction. Ten samples each of normal oral mucosa, proliferative verrucous leukoplakia, and squamous cell carcinoma were immunostained with antibodies against p53 protein; 8 of 10 cases of proliferative verrucous leukoplakia cases and 7 of 10 cases of oral squamous cell carcinoma were positive for p53 protein. Minimal staining was observed in normal oral tissues. The quantified labeling indexes demonstrated a range that corresponded to lesion progression. Single-strand conformation polymorphism analysis revealed p53 gene mutations within exons 5 to 8 in 40% (4 of 10) of the squamous cell carcinoma samples. Two of the 4 mutated squamous cell carcinoma samples lacked p53 expression. No p53 mutations were detected in proliferative verrucous leukoplakia tissues. Human papillomavirus 16 was identified in 2 of 7 p53 positive oral squamous cell carcinoma samples. Human papillomavirus 16 and 18 were identified in two of eight p53 positive proliferative verrucous leukoplakia samples. One p53 negative squamous cell carcinoma sample was positive for human papillomavirus 16 and had a mutation in exon 6 of the p53 gene. Human papillomavirus infection along with p53 expression plays a yet to be defined role in the pathogenesis of a limited number of cases of proliferative verrucous leukoplakia and squamous cell carcinoma. p53 immunohistochemistry, p53 gene mutations, and human papillomavirus infection prevalence do not provide a means to differentiate between leukoplakia and carcinoma and do not provide a predictive test for progression of leukoplakia to carcinoma.

Multiple synchronous primaries of the gastrointestinal tract: a molecular case report

Six synchronous gastrointestinal primaries were identified in a 70 year old male with no known cancer predisposition syndrome or recognized risk factors except alcohol abuse. These specimens appeared to be independent and unrelated by gross and histopathological examination. In order to further evaluate the six tumors, we analyzed selected DNA sequences for alterations in the K-ras oncogene and p53 tumor suppressor gene. In addition, three loci were analyzed to determine microsatellite instability. Using the polymerase chain reaction, single stranded conformational polymorphism, and DNA sequencing, we demonstrated that each primary manifests genetic characteristics typical of the tissue of origin. In addition, one primary, a moderately differentiated colon adenocarcinoma, exhibited mutations not detected in the other specimens. This study suggests that these synchronous primaries arose independently and progressed along different carcinogenic pathways.

Discordance of p53 status in matched primary tumours and metastases in head and neck squamous cell carcinoma patients

To study the use of p53 as a diagnostic tool in head and neck squamous cell carcinoma (HNSCC), we analysed 15 primary tumours (PT) and matched lymph node metastases (LNM) for overexpression and mutations of p53. The primary goal was to study whether differentiation between primary and metastatic disease through their p53 status would be possible. Immunohistochemistry for p53 protein (antibody BP 53-12-1) was performed. Mutations of the p53 gene were detected by exon-specific amplification of DNA (exons 4-9), followed by exon analysis using denaturing gradient gel electrophoresis (DGGE). Mutant exons were sequenced. p53 overexpression was detected in seven (47%) of the PT and in seven (47%) of the LNM. 6 patients (40%) exhibited p53 protein overexpression in both PT and LNM. 2 patients had a different p53 protein expression in each sample. Mutations in the p53 gene were detected in 6 patients (40%) in the PT and in 7 patients (47%) in the LNM. In 2 patients (13%), the same mutation was found in the PT and in the LNM. 9 patients (60%) had a different mutation in each sample. We conclude that a poor correlation exists between p53 protein overexpression and p53 gene mutation in HNSCC. Also, a poor correlation for both detection techniques exists, when PT and LNM are compared. The p53 status may seem to differ between PT and LNM because of polyclonality in the PT. More sensitive detection techniques could be promising.

SSCP pattern indicative for p53 mutation is related to advanced stage and high-grade of tongue cancer

53 and bcl-2 are involved in the control of cell cycling and apoptosis. Environmental factors such as smoking and radiation can disturb p53 function and predispose a cell to malignant transformation. To investigate the role of p53 mutations, as well as p53 and bcl-2 protein expression in squamous cell carcinoma of the tongue, 39 samples were analysed. Since neck metastasis is the most important prognostic factor of this disease, samples from patients both with and without nodal disease were selected to find out whether there was any difference between the groups. Non-radioactive single-stranded conformation polymorphism (SSCP) was used to screen p53 mutations; an altered SSCP pattern indicating p53 mutation was found in 21 samples (54%). A significant correlation between tumour size, histological differentiation and p53 mutations was found (P < 0.01). Immunocytochemically, nuclear expression of p53 was moderate or strong in 18 (46%) samples. No correlation between altered p53 SSCP pattern and p53 immunoreactivity was seen. bcl-2 expression was cytoplasmic; moderate or strong staining was detected in only six of the carcinoma samples (15.5%). Interestingly, there was a significant correlation between smoking and bcl-2 expression (P < 0.01): all six samples with moderate or strong staining were taken from heavy smokers. Furthermore, all those patients died within 32 months.

Overexpression of the EGF receptor and p53 mutations are mutually exclusive in the evolution of primary and secondary glioblastomas

Glioblastoma multiforme, the most malignant human brain tumor, may develop de novo (primary glioblastoma) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). We present further evidence that primary and secondary glioblastomas constitute distinct disease entities which develop through the acquisition of different genetic alterations. We analyzed p53 mutations, p53 protein accumulation and epidermal growth factor receptor (EGFR) overexpression in 49 biopsies classified as primary or secondary glioblastoma according to clinical and histopathologic criteria. Patients with primary glioblastoma were selected on the basis of a clinical history of less than 3 months and histopathologic features of glioblastoma at the first biopsy (19 cases; mean age, 55 years). The diagnosis of secondary glioblastomas required at least two biopsies and clinical as well as histologic evidence of progression from low grade or anaplastic astrocytoma (30 cases; mean age, 39 years). DNA sequence analysis showed that p53 mutations were rare in primary glioblastomas (11%) while secondary glioblastomas had a high incidence of p53 mutations (67%), of which 90% were already present in the first biopsy. The incidence of p53 protein accumulation (nuclear immunoreactivity to PAb 1801) was also lower in primary (37%) than in secondary glioblastomas (97%). In contrast, immunoreactivity for the EGF receptor prevailed in primary glioblastomas (63%) but was rare in secondary glioblastomas (10%). Only one out of 49 glioblastomas showed EGFR overexpression and a p53 mutation. These data indicate that overexpression of the EGF receptor and mutations of the p53 tumor suppressor gene are mutually exclusive events defining two different genetic pathways in the evolution of glioblastoma as the common phenotypic endpoint.

Decreasing p53 overexpression in sequential, recurrent, oral squamous cell carcinomas

Expression of abnormal p53 protein is a widely recognised marker of malignancy including oral squamous cell carcinoma. This is a longitudinal study of p53 expression in fixed, paraffin-embedded tissue from 3 patients with multiple, recurrent, squamous cell carcinomas of floor of mouth (n = 4, 4, 3). All carcinomas demonstrated increased expression of p53 compared to normal tissues. However, there was reduction in expression from primaries to subsequent recurrent tumours in all 3 patients. The significance of reduction of expression of p53 in sequential recurrences is unclear, but as each of these patients has now survived for at least 5 years this may be a phenomenon indicating a favourable prognosis. As this study relates to only 3 patients, a larger study is needed to confirm this initial observation.

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 gene mutations in oral carcinomas from India

In this study, we analyzed 53 oral squamous-cell carcinomas among Indians for the presence of alterations in the tumor-suppressor gene p53 by PCR-SSCP and sequencing methods. Our results showed that 21% (11/53) of oral carcinomas analyzed carried mutations within the exons 5-8 of the p53 gene. We have identified 11 single-base pair substitutions consisting of 10 mis-sense mutations and one at the splice acceptor site, and one deletion mutation involving 4 consecutive bases. The majority of the base substitutions were transitions (5 TA to CG and 5 GC to AT), while only one transversion (TA to GC) was observed. Probable hot-spots for the mutation induction were identified at codons 149 and 274, which have not been observed before in head-and-neck cancers. The mutational spectrum might have originated from base alkylations at guanine and thymine residues, caused by some alkylating agents. The present results are thus consistent with the involvement of tobacco-related nitrosoamines in the etiology of oral squamous-cell carcinoma.

Molecular changes in oral cancer may reflect aetiology and ethnic origin

Oral cancer, although uncommon in the Western world, accounts for up to 40% of all malignancies in parts of India and South East Asia. Recognised aetiological agents of oral cancer include tobacco and alcohol. This paper reviews the spectrum of molecular changes found in oral squamous cell carcinomas from Western (U.K., U.S.A., Australia) and Eastern (India, S.E. Asia) countries. p53 mutations are common in tumours from the West (47%) but are infrequent in the East (7%). Tumours from India and South East Asia are characterised by the involvement of ras oncogenes, including mutation, loss of heterozygosity (H-ras) and amplification (K- and N-ras), events which are uncommon in the West. The possibility that these genetic differences reflect aetiology and/or ethnic origin is discussed.

p53 overexpression in head and neck squamous cell carcinoma: review of the literature

As a tumour suppressor gene, the inactivation of p53 induces the development of numerous human cancers. Mutations of p53 have been implicated in the pathogenesis of head and neck squamous cell carcinoma (HN-SCC) at a high incidence. In premalignant lesions and in situ carcinomas, p53 overexpression is not exclusively restricted to neoplastic cells, but frequently affects the normal appearing keratinocytes adjacent to p53 positive neoplasms or present in dysplastic areas. These results suggest that as contributors to the early phases of HN-SCC development, p53 alterations may be excellent biomarkers that indicate the predisposition of a particular oral cavity premalignant lesion toward malignancy. In most cases, the p53 overexpression status of a tumour metastasis is identical to that of a primary tumour, indicating that a p53 mutation precedes metastatic spread. In patients with multiple primary tumours, multiple foci of p53 overexpression are observed in epithelia distant from the tumour. So the expression of p53 in normal epithelium would indicate an increased risk for transformation to second or third primary cancers. Distinct p53 mutations in different primary tumours of the same patient indicate that these cancers arise as independent events; these results support the existence of multifocal polyclonal processes. Regardless of the aforementioned results that support p53 as a valid tumour biomarker, most studies have shown no relationship between the expression of p53 and clinical and histopathological parameters. The role played by p53 mutations in the progression and vital prognosis of HN-SCC has not yet been demonstrated.

P53-mediated radioresistance does not correlate with metastatic potential in tumorigenic rat embryo cell lines following oncogene transfection

PURPOSE

Changes in wild-type p53 protein function occur in the majority of human tumors, and may alter genomic stability and the cellular response to ionizing radiation. Whether oncoproteins can render tumor cells both radioresistant and metastatic, may have implications for clinical strategies designed to improve local tumor control. In the studies reported here, we tested the hypothesis that acquired radioresistance correlates with metastatic potential within a large panel of transformed rat embryo cell (REF) lines following transfection with activated H-ras, mutant p53, and HPV16-E7 alleles.

METHODS AND MATERIALS

Rat embryo cells (REF cells) were transfected using the calcium-phosphate technique with an activated H-ras gene alone, or in combination with human papillomavirus HPV16-E7 and/or human or murine mutant p53 sequences. Other rat embryo cell clones expressing transfected HPV-E7 and activated ras sequences subsequently acquired endogenous p53 gene mutations during culture in vitro. The relative expression of p21ras and p53 protein for each REF transformant was determined by Western blot analysis following transfection. REF clones were phenotypically characterized at early passage (i.e., passages 5-7) and late passage (i.e., passages 10-20) for their: (a) relative tumor growth rate, and (b) their ability to undergo spontaneous metastasis following intramuscular injection into the hind legs of SCID mice. In vivo phenotypic end points were then compared to previously measured parameters of in vitro radiosensitivity for each cell line. Additionally, the expression of the cellular protease, plasminogen activator, was determined for a number of metastatic and nonmetastatic cell lines.

RESULTS

We found no evidence that selected oncogene-transfected REF transformants that were radioresistant in culture had a greater spontaneous metastatic potential than nonradioresistant REF transformants. Neither the level of expression of the p21ras protein nor that of the p53 protein was correlated with the spontaneous metastatic phenotype when tested at early passage. The metastatic phenotype appeared to be independent of p53 genotype. The majority of metastatic REF clones tested (7 out of 9 clones) expressed plasminogen activator following oncogene transfection, in contrast to nonmetastatic REF transformed cell lines.

CONCLUSIONS

Our results suggest that (a) intrinsic radioresistance does not correlate with spontaneous metastatic potential in oncogene-expressing REF transformant cell lines, and (b), novel clinical strategies designed to overcome oncogene-mediated radioresistance could potentially impact on overall survival, as gains in local tumor control may not be offset by a greater risk of distant metastasis.

Value of p53 expression in oral cancer and adjacent normal mucosa in relation to the occurrence of multiple primary carcinomas

Paraffin embedded, formalin fixed tissue sections from patients suffering from a primary oral squamous cell carcinoma were immunohistochemically investigated for the presence of p53 expression using the Bp53-11 antibody. The aim of this study was to determine the predictive value of p53 expression as a biomarker for the development of a second primary tumour (SPT) in the respiratory and upper digestive tract. In a nested case control study, neoplastic and normal tissue sections of 44 patients who had a previous history of cancer were used. 15 of the 44 had developed a SPT, while the other 29 were minimally 7 years free of disease. Additionally, nine SPTs were included in this study to establish whether concordance exists in tumours that develop in the same field. 10 of the 29 patients (34%) free of tumour during follow-up had p53 positive tumours. 8 of 15 patients (53%) who developed a SPT had a p53 positive primary tumour. This difference is not statistically different (chi 2-test). Forty percent of the total group of primary oral cavity tumours showed p53 positivity. When comparing the first and the second tumours, discordance in p53 expression between the first and second tumours was seen in 4 out of 9 cases. None of the cases showed p53 positivity in adjacent normal mucosa. In conclusion, p53 immunoreactivity in neoplasia, dysplasia and normal tissue does not predict the development of a SPT. In addition, multiple primary tumours do not have identical p53 expression.

TP53 mutations in upper aerodigestive squamous cell carcinomas from a group of Brazilian patients

BACKGROUND

Loss of function of the tumor suppressor gene TP53 contributes to the development of several tumors.

PATIENTS AND METHODS

We screened DNA samples from 47 patients with upper respiratory system squamous cell carcinomas for the presence of TP53 mutations. Exons 4 to 8 of the TP53 gene were amplified by the polymerase chain reaction, and mutations were identified by single-strand conformation polymorphism analysis.

RESULTS

The TP53 mutations were demonstrated in 23 cases (49%). Mutations were distributed as follows: exon 4, 5 cases; exon 5, 4 cases; exon 6, 6 cases; exon 7, 4 cases; and exon 8, 4 cases. Demographic variables, tumor site, stage, family history of cancer, and tobacco smoking were not predictors of TP53 mutations. There was an increasing number of mutations in the more undifferentiated tumors (P = 0.0594).

CONCLUSIONS

These findings suggest that TP53 mutations are associated with tumor differentiation, but not with the risk of lymph node metastasis in the group of patients analyzed.

Recurrences and second primary tumours in the head and neck region: differentiation by p53 mutation analysis

BACKGROUND

Patients with head and neck cancer are at high risk of developing additional primary tumours in the aerodigestive tract as a result of field cancerization phenomena. In this context, the appearance of a new neoplasm often poses a problem of differential diagnosis between recurrence and new primary tumour. The differentiation between the two entities in essentially clinical and conventionally based on the histological and spatio-temporal relations between the two lesions; however, the validity of these criteria has still to be assessed.

DESIGN

To evaluate whether field cancerization phenomena may affect the clinical diagnosis of relapse/metastasis in the head and neck region, p53 mutation pattern was analysed in a series of primary tumours and corresponding recurrences/metastases. The rationale was that, since p53 mutations are a very early and polymorphic phenomenon, a recurrence/metastasis must retain the same mutation as the the primary tumour, whereas independent tumours are likely to display a different p53 gene status.

RESULTS

Molecular analysis provided conclusive results in 9 of 12 cases analysed. The clinical diagnosis of recurrence was confirmed by molecular analysis in 4 of these cases. In contrast, a differential p53 mutation pattern supported an independent origin for 3 presumed local recurrences and 2 lung lesions.

CONCLUSIONS

The use of p53 mutation analysis as a clonality marker allowed us to ascertain the inadequacy of the current diagnostic criteria for the differentiation between a new independent tumour and recurrence/metastasis. These findings substantiate the relevance of field cancerization phenomena in the head and neck region and prompt the use of p53 mutation analysis as a fundamental tool to improve the diagnosis and management of head and neck cancers.

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

Mutation, deactivation and disregulated expression of oncogenes and tumour-suppressor genes may be involved in the pathogenesis of oral squamous cell carcinoma (SCC). Deactivation of the p53 tumour-suppressor gene allows cell proliferation and blocks apoptosis of malignant oral keratinocytes. Mutation in the ras oncogene results in persistent mitogenic signalling. Upregulatioed c-Myc expression, in the presence of growth factors, provides an additional proliferative signal. Loss of retinoblastoma tumour-suppressor gene (Rb) function may contribute to oral keratinocyte hyperproliferation and recent evidence suggests that simultaneous deactivation of both p53 and Rb is required for tumourigenesis. Enhanced Bcl-2 and reduced Fas expression inhibit tumour cell apoptosis and may convey resistance to cytotoxic drugs and T cell-mediated cytotoxicity, respectively. Exogenous mutagens such as tobacco, alcohol and viral oncogenes may cause altered expression of oncogenes and tumour-suppressor genes in some cases of oral SCC. The impact of these mechanisms on future therapies for oral SCC is highlighted.

Lack of concordant p53 mutations in some paired primary and metastatic mouse squamous cell carcinomas induced by chemical carcinogenesis

We studied the frequency and pattern of p53 mutations in 16 mouse skin primary squamous carcinomas induced by chemical carcinogens and their 19 matched metastases. The molecular changes were analyzed by polymerase chain reaction-single-strand conformation polymorphism and subsequent direct sequencing analysis. Eleven mutations of the p53 gene were detected in a total of eight primary tumors, and 10 mutations were detected in nine metastases. Only four pairs had identical mutations in primary and paired metastatic tumors. Eight mutations in six pairs were detected in primary tumors but not in their metastases, and four mutations from three matched pairs were detected in metastases but not in primary tumors. The four pairs that contained the same mutations in both the primary and secondary tumors had lymph-node metastases, and all mutations occurred in exon 8. Conversely, five of six pairs with p53 mutations only in primary tumors had lung metastases, and only one of the mutations occurred in exon 8. None of the mutations found only in metastases were located in exon 8. These data indicate that p53 mutations are prevalent in lymph-node metastases and infrequent in lung metastases of mouse skin tumors and that primary tumors with exon 8 mutations may be more likely to metastasize to the lymph nodes.

Heat shock protein expression in oral epithelial dysplasia and squamous cell carcinoma

Heat shock protein (HSP) expression is upregulated in tumour cells and, therefore, HSP expression is a likely marker of the malignant potential of oral epithelial lesions. Furthermore, the 70-kDa HSP (HSP 70) is implicated in the degree of tumour differentiation, the rate of tumour proliferation and the magnitude of the anti-tumour immune response. Accordingly, the distribution and intensity of HSP 70 expression was assessed in the epithelial compartment of oral squamous cell carcinoma (SCC, n = 29), dysplastic oral epithelium (n = 18) and benign oral mucosal lesions (n = 22) using avidin-biotin complex immunohistochemistry and microdensitometry under standardised conditions. Staining intensity was recorded in kilo-ohms (k omega). Normal oral mucosa (n = 15) was used for comparison, and results were analysed using Kruskall-Wallis and Fisher's exact tests. The distribution of HSP 70 expression in well differentiated SCC was significantly different from that in poorly differentiated SCC (P < 0.05), the latter demonstrating a more focal staining pattern. Median staining intensity in SCC (6.22 k omega), epithelial dysplasia (9.61 k omega) and the benign oral mucosal lesions (8.28 k omega) was significantly greater than that in normal oral mucosa (5.64 k omega; P < 0.05). Staining intensity in poorly differentiated SCC (7.66 k omega) was greater than that in moderately differentiated SCC (4.77 k omega), although this result just failed to reach statistical significance (P = 0.06). These results suggest that, as employed currently, HSP 70 expression is not a definitive marker of oral malignancy or malignant potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor angiogenesis as a prognostic factor in oral cavity tumors

BACKGROUND

Lymph-node metastasis is the single greatest predictor of survival in patients with oral cavity cancers. Tumor angiogenesis has been correlated with metastasis in breast cancer and may have prognostic value in other tumors.

PATIENTS AND METHODS

Sixty-six patients with clinically node-negative oral cavity squamous cell cancers were reviewed. Samples were cut and stained for factor VIII. The percentage of area of tissue stained for factor VIII was quantitated by a computerized image analyzer. Tumor depth was measured with an ocular micrometer to the nearest 0.1 mm. Variables were statistically examined against regional recurrence.

RESULTS

The probability of metastasis (%) was 2 for tumor staining of < or = 10% and 93 for tumor staining > 10% (P < 0.0001). The tumor depth was < or = 4 mm in 10 and > 4 mm in 83 (P < 0.0001). Patients with < or = 4 mm and < or = 10% staining had a 2% rate of recurrence, and patients with > 4 mm and > 10% staining had a 100% rate of recurrence (P < 0.0001).

CONCLUSION

Although tumor thickness was suggestive of predictability, only angiogenesis was a statistically significant predictor of recurrence in a multivariate analysis (P < 0.0001). Angiogenesis showed a strong correlation with regional recurrence and may be used as an independent prognostic indicator.