High frequency of p53 mutations in human oral epithelial dysplasia and primary squamous cell carcinoma detected by yeast functional assay

Mutations in p53 Gene Exons in a Sample from the South of Spain in Oral Cancer

Background

Cancer is a genetic disease caused by mutations in DNA and epigenetic alterations that control gene expression. The majority of epidermoid carcinomas develop within the fields of epithelial genetic alterations. The mechanisms underlying tumorigenesis of epidermoid carcinoma are as yet unknown; therefore, precise identification of the risk factors is needed. Aim: The main aim of this study is to analyse and identify the emergence of the mutations described in the literature of the p53 gene with regard to the emergence of cancer in a sample of dysplastic and cancerous lesions in oral cavity mucosa in the population of the south of Spain, in order to determine the presence of said mutations and the percentage of them in our population.

Material and Methods

A cross-sectional study was carried out, with a sample size of 22 patients with potentially malignant oral lesions ancillary to biopsy. All were patients, of both sexes, over 18 years of age from the Virgen del Rocío University Hospital with potentially malignant lesions in oral mucosa ancillary to biopsy (leukoplakias, erythroplasias or leukoerythopkias). An anatomopathological study was performed on all the samples and the lesions were divided into three types: low-grade dysplasia, high-grade dysplasia and squamous cell carcinoma. In respect of the genome study process, a complete search or scan for mutations in exons 5, 6, 8 and 9 of the p 53 gene was carried out, given that in the IARC database we observed that the 5 and 6 as well as the 8 and 9 exon sizes can be scanned completely in this way, since they have amplificon sizes of 476 and 445 base pairs respectively.

Results

In the scan for the complete exons 5, 6, 8 and 9 only a single result of interest was found to be described. In patient NBI 57 a change was observed in the TAT triplet by ATT of EXON 6, the change being of the T nucleotide by the A and in both directions both in Forward and Reverse. The exact location in the NCBI is GR Ch 37 p13 on chromosome 17, EXON 6 of the P53 gene and the change is in the C.613 T>A nucleotide; NM_000546.

Conclusions

On reviewing this genetic variant in different scientific databases, such as ENSEMBL among others, in at least 6 different biocomputing tools it is described as a pathogen, therefore we can conclude that it is a pathogenic mutation for this case in particular. The rest of the mutations described in the literature on exons 5, 6, 8 and 9 of the p53 gene have not been found in our sample.

Key words:Oral cancer, p53, Mutations, Exon.

The Potential of Phytochemicals in Oral Cancer Prevention and Therapy: A Review of the Evidence

The etiological factors of oral cancer are complex including drinking alcohol, smoking tobacco, betel quid chewing, human papillomavirus infection, and nutritional deficiencies. Understanding the molecular mechanism of oral cancer is vital. The traditional treatment for patients with oral squamous cell carcinoma (e.g., surgery, radiotherapy, and chemotherapy) and targeted molecular therapy still have numerous shortcomings. In recent years, the use of phytochemical factors to prevent or treat cancer has received increasing attention. These phytochemicals have little or no toxicity against healthy tissues and are thus ideal chemopreventive agents. However, phytochemicals usually have low water solubility, low bioavailability, and insufficient targeting which limit therapeutic use. Numerous studies have investigated the development of phytochemical delivery systems to address these problems. The present article provides an overview of oral cancer including the etiological factors, diagnosis, and traditional therapy. Furthermore, the classification, dietary sources, anticancer bioactivity, delivery system improvements, and molecular mechanisms against oral cancer of phytochemicals are also discussed in this review.

Long-term follow-up of oral epithelial dysplasia: A hospital based cross-sectional study

Background/purpose

Oral epithelial dysplasia (OED) is characterized histopathologically by cellular and morphological changes that remain the single most important factor predicting risk for subsequent development of invasive neoplasia. Hence the aims of the present study were to determine the rate of malignant change of OED in a group of patients followed-up for a number of years, and hence determine factors likely to influence this malignant change, and to describe the clinical characteristics of patients who developed recurrence of OED and second dysplastic lesions.

Materials and methods

This is hospital based cross-sectional study of all biopsy reports with histologically confirmed OED between 2012 and 2018 were retrospectivelly reviewed.

Results

A total of 359 patients with histologically confirmed OED were reviewed, twenty (5.5%) of the 359 patients developed an invasive squamous cell carcinoma (SCC) of the oral mucosa over a period of 2 to 274 months with mean transformation time of 3.3 years.

Conclusion

The high risk of malignant transformation of OED seems to be related to patients older than 50 years when lesions were on the floor of mouth with severe dysplastic changes.

Dominant-negative p53 mutant R248Q increases the motile and invasive activities of oral squamous cell carcinoma cells

The tumor suppressor gene TP53 (gene) codes for a transcription factor which transactivates its target genes responsible for cell cycle arrest, DNA repair, apoptosis, and senescence. TP53 is well known to be the most frequent target of genetic mutations in nearly half of human cancers including oral squamous cell carcinoma (OSCC). Many p53 mutants including R248Q and R248W not only lose its tumor-suppressor activities, but also interfere with the functions of wild-type p53; this is so-called dominant-negative (DN) mutation. The DN p53 mutation is a predictor of poor outcome in patients with various cancers, and also a risk factor for metastatic recurrence in patients with OSCC. Recently it has been reported that DN p53 mutants acquire new oncogenic activities, which is named gain-of-function (GOF). This study aimed at determining whether R248Q and R248W were involved in OSCC cells' acquiring aggressive phenotypes, using SAS, HSC4 and Ca9-22 cell lines. First, two mutants p53, R248Q and R248W, were respectively transfected into SAS cells harboring recessive-type p53 (E336X). As a result, SAS cells expressing R248Q showed highly spreading, motile and invasive activities compared to parent or mock-transfected cells whereas those expressing R248W did not increase those activities. Secondly, in HSC4 cells harboring R248Q and Ca9-22 cells harboring R248W, expressions of the mutants p53 were inhibited by the transfection with siRNAs targeting p53. The inhibition of the mutants p53 decreased spreading, motile and invasive activities of HSC4 cells whereas it did not affect those activities of Ca9-22 cells. These findings suggest that R248Q p53 mutation, but not R248W p53 mutation, induces more motile and invasive potentials in human OSCC cells.

Detection and Functional Analysis of TP53 Mutations in CLL

Chronic lymphocytic leukemia (CLL) represents a prototype disease in which TP53 gene defects lead to inferior prognosis. Here, we present two distinct methodologies which can be used to identify TP53 mutations in CLL patients; both protocols are primarily intended for research purposes. The functional analysis of separated alleles in yeast (FASAY) can be flexibly adapted to a variable number of samples and provides an immediate functional readout of identified mutations. Amplicon-based next-generation sequencing then allows for a high throughput and accurately detects subclonal TP53 variants (sensitivity <1% of mutated cells).

Profiling cancer-related gene mutations in oral squamous cell carcinoma from Japanese patients by targeted amplicon sequencing

Somatic mutation analysis is a standard practice in the study of human cancers to identify mutations that cause therapeutic sensitization and resistance. We performed comprehensive genomic analyses that used PCR target enrichment and next-generation sequencing on Ion Proton semiconductor sequencers. Forty-seven oral squamous cell carcinoma (OSCC) samples and their corresponding noncancerous tissues were used for multiplex PCR amplification to obtain targeted coverage of the entire coding regions of 409 cancer-related genes (covered regions: 95.4% of total, 1.69 megabases of target sequence). The number of somatic mutations in 47 patients with OSCC ranged from 1 to 20 with a mean of 7.60. The most frequent mutations were in TP53 (61.7%), NOTCH1 (25.5%), CDKN2A (19.1%), SYNE1 (14.9%), PIK3CA (10.6%), ROS1 (10.6%), and TAF1L (10.6%). We also detected copy number variations (CNVs) in the segments of the genome that could be duplicated or deleted from deep sequencing data. Pathway assessment showed that the somatic aberrations within OSCC genomes are mainly involved in several important pathways, including cell cycle regulation and RTK–MAPK-PI3K. This study may enable better selection of therapies and deliver improved outcomes for OSCC patients when combined with clinical diagnostics.

Cytogenetic significance of chromosome 17 aberrations and P53 gene mutations as prognostic markers in oral squamous cell carcinoma

BACKGROUND

Cytogenetic analysis has detected an accumulation of genetic lesions in oral cancers. Numerical changes in chromosome 17 might be associated with an up-regulation of p53 gene, and could contribute to critical events in carcinogenesis. The aim of this study was to reveal possible correlations between the numerical aberrations of chromosome 17, deletion or amplification of the P53 gene and histological grading in patients with oral squamous cell carcinoma (OSCC).

METHODS

This study was performed retrospectively on anonymous forty paraffin embedded specimens diagnosed with a primary OSCC. Sections were prepared for p53 immunohistochemical staining and FISH technique evaluation.

RESULTS

All studied cases showed a positive nuclear staining with different indices for the p53 protein. Furthermore, statistical analysis showed a significant difference between all histological types of OSCC. In term of P53 immunoreactivity well differentiated OSCC showed the highest, whereas poorly differentiated showed weakest. Regarding chromosome 17 aberrations and p53 gene mutations, Spearman correlation test revealed a statistical significant positive correlation between chromosome 17 abnormalities and p53 gene mutations as well as with the immunohistochemical expression of p53 proteins. Moreover, the positive association between p53 gene mutations and the expression of p53 protein was statistically significant.

CONCLUSION

In the light of the previous findings, we concluded that numerical aberrations of chromosome 17 and p53 gene mutations as well as expression of p53 protein have enormous influence on various cellular processes including differentiation and carcinogenesis. Such knowledge provides an easy and simplified approach to prognosis predilection for OSCC.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2015_232 .

Methyl methanesulfonate induces apoptosis in p53-deficient H1299 and Hep3B cells through a caspase 2- and mitochondria-associated pathway

Methyl methanesulfonate (MMS) has been shown to induce apoptosis in various cell types through p53-dependent pathways. Nevertheless, pharmacological and genetic blockade of p53 functions results in similar or delayed sensitivity to MMS treatment, suggesting the presence of p53-independent apoptotic mechanisms. To understand the p53-independent mechanisms that are engaged during MMS-induced apoptosis, we established MMS-induced apoptotic cell models using p53-deficient H1299 and Hep3B cells. Our results demonstrated that MMS at concentrations of 50, 100, 200, 400 and 800 μM induced the formation of gammaH2AX foci, and that at higher concentrations, 400 and 800 μM, MMS treatment led to apoptosis in the two cell lines. This apoptotic cell death was concurrent with the loss of mitochondrial membrane potential, nuclear-cytosolic translocation of active caspase 2, release of cytochrome c from mitochondria, and the cleavage of caspase 9, caspase 3 and PARP. However, MMS-induced DNA damage failed to stabilize the p53 family members TAp73 and DNp73. These results demonstrated a p53- and p73-independent mechanism for MMS-induced apoptosis that involves the nuclear-cytosolic translocation of active caspase 2 as well as the mitochondria-mediated pathway.

Significance of Ki-67 and p53 immunoexpression in the differential diagnosis of oral necrotizing sialometaplasia and squamous cell carcinoma

Necrotizing sialometaplasia (NS) is a benign condition that usually involves the hard palate and can be mistaken for invasive squamous cell carcinoma (SCC). In this study, we have demonstrated that p53 and Ki-67 staining may assist in the differential diagnosis of NS from SCC. Thirteen cases of NS and 20 cases of oral cavity SCC were randomly selected from our surgical pathology archive from 1992 to 2009. Each case was additionally stained with Ki-67, p53, BCL-2, p16, and epidermal growth factor receptor (EGFR) antibodies. All 13 cases of NS were negatively stained for BCL-2, EGFR, and Ki-67. Three cases (23%) showed weak and focal positive nuclear staining for p53. Two cases (15%) showed positive staining for p16. In 16 well-differentiated SCC cases, p53 was positive in 12 cases (75%); BCL-2, p16, EGFR were positive in 3 cases (18%); and Ki-67 was positive in all cases (100%). In 4 moderately differentiated SCC cases, p53 expression was positive in all cases. Two tumors (50%) had a positive expression of BCL-2. Three cases (75%) had a positive p16 staining, and 1 (25%) had a positive EGFR staining. All cases were positive with high nuclear staining greater than 35% of cells for Ki-67. Ki-67 and p53 showed more intense staining and increased in moderately differentiated SCC comparing with well-differentiated SCC and NS. BCL-2, EGFR, and p16 had the same pattern of staining with the same extent in NS and SCCs. The diagnosis of NS may be difficult and may be supplemented via immunohistochemistry by demonstrating focal or absent p53, low to absent Ki-67 (<10% of cells). Although Ki-67 and p53 staining are generally more intense and are increased in malignancy, these findings may be helpful adjuncts in the differential diagnosis of NS from SCC in appropriate clinical setting.

The role of p53 as a surrogate marker for chemotherapeutical responsiveness in ovarian cancer

INTRODUCTION

In advanced ovarian cancers (OCs), p53 mutations are frequently observed. The objective of this study was to explore the value of the p53 mutational status, using four different techniques, in advanced OC patients as a predictive marker for responsiveness to platinum-based chemotherapy.

METHODS

One hundred and four, mostly serous papillary OC specimens were analyzed, of which all received a platinum containing chemotherapy after optimal cyto-reductive surgery. To verify the p53 mutational status, immunohistochemical staining with monoclonal antibodies, functional yeast assay (FASAY), single-strand conformation polymorphism analysis (SSCP) and genomic sequencing was performed in parallel.

RESULTS

Out of ten OC patients [2 low malignant potential (LMP)/8 G1] only two had a mutant p53, whereas eight showed a wild-type p53. 40 out of 63 (G2/3) patients with G2/3 OC showed mutant p53 and 23 patients showed a wild-type pattern. p53 status was significantly different between these two groups (LMP/G1 vs. G2/3) (P = 0.015). A progressive disease after chemotherapy completion was noted in 35.6% of the patients (26 out of 73); in 69.2%, a mutated p53 and in 30.8%, a wild-type p53 was found. Nine (12.3%) patients showed a complete response at the end of the first-line chemotherapy. Out of these nine patients five had a mutated and four a wild-type p53. A partial response was observed in nine (12.3%) patients of whom four had a mutated p53. With respect to response to first-line chemotherapy (six cycles of platinum containing regimen), the p53 status was not predictive; no statistical significance regarding the p53 mutational status was observed when the two extreme groups PD versus PR/CR were compared (P > 0.05).

CONCLUSION

In this study, the p53 mutational status was not predictive for responsiveness to platinum-based chemotherapy; but p53 was significantly more frequently mutated in poorly differentiated OCs.

Radiation-induced glioblastoma in a medulloblastoma patient: a case report with molecular features

We report a case of glioblastoma (GBM) occurring 8 years after radiation therapy for a medulloblastoma. A 15-year-old boy underwent surgery and radiotherapy for a medulloblastoma and 8 years later he developed a second tumor at the same site. The second lesion showed different histological and molecular features, was diagnosed as a glioblastoma and fulfilled the criteria of radiation-induced neoplasm. Mutational analysis of the p53 gene showed a C to G transition at codon 176 in tumor DNA. LOH was detected at 17p and 19q. The tumor also showed O6-methylguanine-DNA methyl-transferase (MGMT) promoter methylation and no amplification of EGF receptor. In conclusion, the radiation-induced MGMT hyper-methylation and p53 mutations may have a role in the development of a subgroup of radio-induced glioma (RIG), suggesting that these molecular alterations directly cooperate in the genesis of the post-irradiation GBM. Moreover RIGs seem to be a heterogeneous group of tumors that may resemble either primary or secondary GBM.

Loss of p53 expression correlates with metastatic phenotype and transcriptional profile in a new mouse model of head and neck cancer

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most frequent cancer worldwide. Because HNSCC is largely acquired by environmental carcinogen exposure rather than through germ line mutations, there are no known familial forms of the disease in humans nor are there inbred rodent strains prone to spontaneous head and neck tumors. Transgenic animals with inactivation of tumor suppressor genes commonly mutated in human cases of HNSCC provide attractive models for studying the pathogenesis of head and neck cancer. p53 is the most frequently inactivated tumor suppressor gene in HNSCC. We used a chemical induction protocol in mice heterozygous for the p53 gene to evaluate how p53 inactivation contributed to head and neck carcinogenesis the mouse model. Metastatic squamous cell carcinomas developed in 100% of animals. Histopathologically, the tumors ranged from well to poorly differentiated and showed many molecular features of human HNSCC. Mice carrying only one p53 allele developed tumors with significantly reduced latency compared with wild-type controls (average, 18 versus 22 weeks). Metastatic cancer cells showed complete loss of p53 expression when compared with primary tumors. Transcriptional profiling showed not only distinct genetic differences between primary and metastatic tumors, but also when cancers from heterozygous null and wild-type animals were compared. Our results provide novel insights into the molecular genetics of tumor progression in head and neck cancer.

Is there a role for PCR-SSCP among the methods for missense mutation detection of TP53 gene?

Mutation analysis methods have increased in variety during the past years. High-throughput microarray methods have especially increased in popularity. However, new methods require reference points, and not all of the methods are equal in sensitivity and specificity. Furthermore, the detection of unknown missense mutations, such as unknown TP53 mutations in human tumors, for clinical purposes requires great accuracy, which may be difficult to acquire with the current high-throughput methods. For these reasons, the classical methods, such as PCR-manual sequencing and PCR-SSCP, are still valuable and necessary.

Prevention of head and neck cancer

In the vast majority of cases, head and neck cancer is a preventable disease. The relationship between tobacco and alcohol and these cancers is well established. Despite efforts aimed at reduction of risk factor exposure and early detection methods, head and neck cancer remains one of the more common cancers worldwide. Recent advances in molecular techniques have provided a framework for future targets for early diagnosis and treatment of these malignancies. This review provides a summary of recent developments in primary and secondary prevention of head and neck cancer and innovative strategies aimed at a reduction in incidence and mortality from this disease. The future prevention of head and neck cancer will likely require solutions to the widespread use of tobacco products and innovative diagnostic techniques leading to improvements in overall survival.

p53 apoptotic response to DNA damage dependent on bcl2 but not bax in head and neck squamous cell carcinoma lines

BACKGROUND

In many tumors, the p53 gene has been mutated or deleted. p53 null mutant mice are prone to development of a variety of neoplasms at an early age. In head and neck cancer, p53 mutations are detected in most cases. p53 has been shown to induce growth arrest, differentiation, and death when overexpressed in cancer cell lines. p53 responds to DNA damage by arresting the cell cycle in G1 or G2 phase until repair can be completed. If DNA damage is severe, p53 may trigger programmed cell death by means of proapoptotic genes such as bax. Studies have suggested that p53 target genes must be intact for proper functioning of the tumor suppressor.

METHODS

We stably expressed transcriptionally active p53 in head and neck squamous cell carcinoma (SCC) lines in which the endogenous gene was inactivated by mutation. We performed proliferation, cell death, cell cycle, and gene expression analysis in control clones and those treated with the DNA damaging agent etoposide.

RESULTS

These clones proliferated slowly with accumulation of cells at the G1/S phase boundary but did not undergo growth arrest or apoptosis. Coexpression of the proapoptotic gene bax (a known target of p53) failed to induce apoptosis in these clones. However, p53 expression sensitized these cells to DNA damage-induced apoptosis by means of inhibition of bcl2 protein levels.

CONCLUSION

We concluded that the p53 apoptotic response to DNA damage was dependent on bcl2 but not bax in head and neck SCC lines.

EphB4 provides survival advantage to squamous cell carcinoma of the head and neck

The receptor tyrosine kinase EphB4 and its ligand EphrinB2 play critical roles in blood vessel maturation, and are frequently overexpressed in a wide variety of cancers. We studied the aberrant expression and biological role of EphB4 in head and neck squamous cell carcinoma (HNSCC). We tested the effect of EphB4-specific siRNA and antisense oligonucleotides (AS-ODN) on cell growth, migration and invasion, and the effect of EphB4 AS-ODN on tumor growth in vivo. All HNSCC tumor samples express EphB4 and levels of expression correlate directly with higher stage and lymph node metastasis. Six of 7 (86%) HNSCC cell lines express EphB4, which is induced either by EGFR activation or by EPHB4 gene amplification. EphrinB2 was expressed in 65% tumors and 5 of 7 (71%) cell lines. EphB4 provides survival advantage to tumor cells in that EphB4 siRNA and AS-ODN significantly inhibit tumor cell viability, induce apoptosis, activate caspase-8, and sensitize cells to TRAIL-induced cell death. Furthermore, EphB4-specific AS-ODN significantly inhibits the growth of HNSCC tumor xenografts in vivo. Expression of EphB4 in HNSCC tumor cells confers survival and invasive properties, and thereby provides a strong rationale for targeting EphB4 as novel therapy for HNSCC.

Functional analysis of p53 tumor suppressor in yeast

The p53 tumor suppressor protein is a transcription factor that mediates the cell's response to various kinds of stress by preventing cell division and/or inducing apoptosis. p53 gene mutations have been detected in nearly 50% of human cancers. These gene aberrations are mostly missense point mutations located predominantly in the central DNA-binding domain. In addition to the classical inactivating mutations, there are also dominant-negative, gain-of-function, temperature-sensitive, and cold-sensitive, discriminating, superactive p53 mutations, and some mutations that do not inactivate p53 activity. Several approaches have been developed for detection and analyses of p53 mutations: first, immunochemical methods have been developed to detect p53 protein levels; second, molecular analyses targeting changes in DNA structure are utilized; and third, functional assays are used to explore the biological properties of the p53 protein. Functional analysis of separated alleles in yeast targets the transactivation capability of the p53 protein expressed in yeast cells. This method uses p53 mRNA isolated from cells and tissues to produce a p53 product by RT-PCR. This method has undergone continuous improvement and now serves as a powerful tool for distinguishing various functional types of p53 mutations. Understanding the exact impact of p53 mutation on its function is an important prerequisite for establishment of efficient anti-cancer therapies.

Functional analysis of p53 gene and the prognostic impact of dominant-negative p53 mutation in endometrial cancer

In addition to the loss of function, mutant p53 can possess a dominant-negative effect on wild-type p53 and may also exert gain-of-function activity. It is not clear whether the functional status of p53 mutation contributes to differences in outcome in endometrial cancer. We collected a total of 92 RNA samples of high quality from endometrial cancer tissues, and the samples were subjected to yeast functional assay and sequencing for p53 mutations. The detected mutant p53 genes were further investigated for their dominant-negative activity using a yeast-based transdominance assay. p53 mutation was found in 24 out of 92 (26.1%) tumors, of which 10 exhibited no dominant-negative activity (recessive mutation) and 14 showed dominant-negative activity. Dominant-negative p53 mutation was related to advanced stages (p = 0.01), nonendometrioid type tumors (p = 0.01) and grade 3 tumors (p = 0.04). The patients with dominant-negative mutation had significantly shorter survival than patients with no mutation (p < 0.0001) and those with a recessive mutation (p = 0.01) in the p53 gene. No difference in survival was found between the patients with tumors harboring a recessive p53 mutation and those with tumors harboring a wild-type p53. Multivariate analysis revealed that dominant-negative p53 mutation (p = 0.019), FIGO stage (p = 0.0037) and histologic subtype (p = 0.014) were independently related to patient survival. Dominant-negative p53 mutation was the most important prognostic factor for stage III/IV endometrial cancer (p = 0.0023). In conclusion, dominant-negative p53 mutation is often found in advanced stages and aggressive histologic subtypes of endometrial cancer and it is a strong predictor of survival of patients with advanced endometrial cancer. To elucidate further the role of p53 mutation in endometrial cancer, it is necessary to investigate gain-of-function activity involving dominant-negative p53 mutant proteins.

p21WAF1/CIP1 expression is a marker of poor prognosis in oral squamous cell carcinoma

BACKGROUND

Previous research on the prognostic relevance of p21(WAF1/CIP1) in oral squamous cell carcinomas (OSCC) yielded inconclusive and contradictory data.

OBJECTIVES

To investigate the prognostic significance of p21(WAF1/CIP1) expression, its relationship to p53 accumulation, proliferation-associated proteins Ki-67 and cyclin D1 in relation to survival and clinicopathological features in OSCC.

METHODS

Surgical specimens taken from 106 randomly selected patients were studied by immunohistochemistry. Expression of the protein of interest was correlated with clinical data.

RESULTS

p21(WAF1/CIP1) expression was found in 61.3% of OSCCs. Expression of p21(WAF1/CIP1) significantly correlated with tumor size (P = 0.005), lymph node involvement (P = 0.002), clinical stage (P < 0.001), and tumor site (P = 0.002). Patients with tumors showing p21(WAF1/CIP1) immunopositivity had decreased 2-year survival (P = 0.018). Expression of p21(WAF1/CIP1) was not related to age, gender, risk factors (tobacco, alcohol), dental status, or tumor differentiation grade. The p21(WAF1/CIP1) expression positively correlated with proliferation-related variables Ki-67 (P = 0.010) and cyclin D1 (P < 0.001), but not with p53 expression.

CONCLUSIONS

The expression of p21(WAF1/CIP1) was found to be associated with poorer prognosis and tumor aggressivity in OSCC.

Loss of p53 transcriptional activity in hepatocellular carcinoma evaluated by yeast-based functional assay: comparison with p53 immunohistochemistry

We studied the transcriptional activity of p53 protein in 50 tissues of hepatocellular carcinoma (HCC) using a yeast functional assay. In this assay, red yeast colonies indicate that p53 protein cannot bind to its specific domain and has lost its transcriptional activity. We also clarified whether mutant p53 protein could inactivate wild-type p53 protein in a transdominant manner using a modified yeast assay. In addition, we examined whether immunohistochemically detectable p53 protein was functionally inactive. The incidence of p53 inactivation was significantly higher in tumors with capsular invasion. Out of 21 tumors diagnosed with p53 mutations, 11 exhibited >75% red colonies, and all contained missense mutations. In these tumors, p53 function was lost because there was supposedly no intact p53 gene on either allele. One missense mutant produced <60% red colonies, but it was also considered inactive as a p53 protein heterotetramer because of its transdominant activity. In 7 of the remaining 9 tumors, p53 was considered to be mutated on one allele and intact on the other. All of these 7 tumors contained nonsense or frameshift mutations and had no transdominant activity, which suggested that p53 function remained intact. Alternately, immunohistochemical analysis demonstrated that all of the tumors with missense mutations were positively immunostained, whereas those that contained nonsense or frameshift mutations were negatively stained. Consequently, positively immunostaining tumors mostly coincided with p53-inactive tumors. These yeast-based assays suggested that p53 function was retained in some mutant cases. Immunohistochemistry was helpful in screening functionally inactive p53 protein in HCCs.

Negative autoregulation of p73 and p53 by DeltaNp73 in regulating differentiation and survival of human neuroblastoma cells

p73, mapped to 1p36.2-3, is a p53-related tumor suppressor but is also induced by the oncogene products such as E2F1, raising a question whether p73 is a tumor suppressor gene or oncogene. p73 has several splicing variants including DeltaNp73 which lacks the NH(2)-terminal transactivation domain. In developing neurons, DeltaNp73 is expressed abundantly and seems to inhibit the pro-apoptotic function of p53. However, the role of TAp73 and DeltaNp73 as well as their regulatory mechanism in cell growth and differentiation of neuroblastoma cells are poorly understood. We have found that TAp73 directly activates the transcription of endogenous DeltaNp73 by binding to the TAp73-specific target element located at position-76 to 57 within the DeltaNp73 promoter region. DeltaNp73 was physically associated with TAp73alpha, TAp73beta and p53, and inhibited their transactivation activities when used reporters of Mdm2, Bax or DeltaNp73 itself in SAOS-2 cells. Overexpression of DeltaNp73 in SH-SY5Y neuroblastoma cells promoted cell survival by competing with p53 and TAp73 itself. Thus, our results suggest that the negative feedback regulation of TAp73 by its target DeltaNp73 is a novel autoregulatory system for modulating cell survival and death, that is also functioning in neuroblastoma cells.

Specific p53 mutations predict poor prognosis in oral squamous cell carcinoma

In this study, we focused on p53 mutations in specific regions, including DNA-binding surface regions, to clarify the correlation between mutations within the specific regions of p53 and clinical outcomes of patients with oral cancers. We analyzed p53 mutations in 121 fresh primary oral squamous cell carcinomas (SCCs) by polymerase chain reaction-single-strand conformation polymorphism or a yeast functional assay. p53 mutations were detected in 51/121 (42%) cases. Mutation of p53 was not associated with any clinicopathological parameters; however, tumors containing specific p53 mutations, e.g. DNA-binding surface regions (L2, L3 and the LSH motif) and conserved regions (II-V), had significantly poorer prognoses than tumors with mutations outside of those regions. Moreover, locoregional failure, lymph node metastasis and the occurrence of subsequent distant metastasis were also significantly associated with mutations within DNA-binding surface regions. These data indicate that specific mutations of p53 could be important prognostic factors in oral SCCs.

Molecular approaches to lung cancer evaluation

The stagnation of therapeutic results in lung cancer over the last decade(s) is a matter of great concern, also due to the constantly increasing incidence of the disease. Among the reasons for this failing therapeutic progress is the lack of understanding of the molecular mechanisms underlying the disease. Presently molecular biology techniques contribute to the deciphering of these mechanisms. This review article gives an overview of the actual situation. The genetic changes leading to malignancy are successively considered at the DNA, RNA and protein levels. Alterations at the DNA level represent the bulk of the available data, being related to p53 mutations, alterations in the beta-tubulin gene, microsatellite alterations, methods for identifying individual and isolated aberrant cells, identification of epigenetic mechanisms such as methylation of the promoter region of tumor suppressor genes; alterations in pre-neoplastic lesions are also evoked. In all cases, the techniques are described and results presented. RNA based methods are critically considered, and the yeast functional assay described. Protein based methods are also considered. The use of cDNA microarrays opens new perspectives and brings the simultaneous identification of numerous DNA alterations at a grip, with hopefully significant improvements in treatment results and increased efficiency for early detection and prevention.

Application of a yeast assay to detect functional p53 mutations in archival prostate cancer tissue

Detection and functional evaluation of mutant p53 alleles using a yeast assay could yield significant information for predicting the prognosis of patients with prostate cancer (CaP). Since the current version of this yeast assay is not applicable to archival tissues, we developed a modified assay for use on formalin-fixed, paraffin-embedded tissue and have applied it to the study of patient samples. Using this modified assay, we examined archival CaP samples from 10 patients for mutations in exons 5-8 of p53 gene. Mutations were detected in four samples: three resulted in the formation of red yeast colonies indicating complete loss of function, while one gave pink yeast colonies, indicating that this mutant retained partial function. In parallel, we analyzed these samples for p53 abnormalities using a single-strand conformational polymorphism (SSCP) approach. Only three of the four yeast-positive samples gave abnormal SSCP bands. In each case where abnormal p53 was found by both methods, DNA sequencing revealed the identical base change. These results suggest that the modified yeast assay may be more sensitive than SSCP for detection of p53 mutations, and demonstrate that the modified method can be used to detect and evaluate the function of p53 mutants present in archival tissue.

Differential mechanisms of constitutive Akt/PKB activation and its influence on gene expression in pancreatic cancer cells

Activated Akt/protein kinase B transmits oncogenic signals leading to inhibition of apoptosis, cellular proliferation, and tolerance to hypoxia. Presently, mutational inactivation of PTEN and activation of Ras are considered to be the major causes of Akt activation. Here we report differential mechanisms of constitutive Akt activation in 4 human pancreatic cancer cell lines (KMP-3, KMP-4, PCI-66, and PCI-68). These 4 cell lines displayed phosphorylation and functional activation of Akt both in the presence and absence of serum, while three control cell lines (PCI-79, KMP-8, and PSN-1) did so only in the presence of serum in culture. All the 7 cell lines harbored K-Ras activated by mutations at codon 12 resulting in MAP kinase kinase (MEK1/2) phosphorylation, and all except one (KMP-8) had p53 mutations, indicating that these mutations are not sufficient for constitutive Akt activation. KMP-3 and KMP-4 had lost PTEN function owing to loss of expression or a mutation, but PCI-66 and PCI-68 retained wild-type PTEN. Phosphorylation of Akt was inhibited by the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 and the tyrosine kinase inhibitor genistein in KMP-3 and KMP-4 cells, indicating that upstream signals are required for Akt activation in these two cell lines. In contrast, neither LY294002 nor genistein inhibited Akt activation in PCI-66 and PCI-68 cells, indicating the involvement of another unknown mechanism of Akt activation independent of PI3K-mediated signaling to Akt. Irrespective of the differential mechanisms, the 4 cell lines showed similar mRNA expression patterns of 49 genes assessed by cDNA array as compared to the 3 cell lines without Akt activation, suggesting that the mechanisms have the same consequences on the downstream signaling of the constitutive Akt activation.

Precancerous foci in pleomorphic adenoma of the salivary gland: recognition of focal carcinoma and atypical tumor cells by P53 immunohistochemistry

BACKGROUND

It is still controversial if atypical tumor cells scattered in salivary pleomorphic adenomas are precancerous and how carcinoma arises in pleomorphic adenomas.

METHODS

We studied clinicopathologically the frequency and variation of cellular atypia among tumor cells and examined the expression status of p53 gene products as well as proliferating cell nuclear antigen (PCNA) in 101 surgical materials of pleomorphic adenomas.

RESULTS

Histopathologically, atypical tumor cells were found in 51% of the cases examined. Their mode of distribution was classified into three groups: focal (six cases, 6%) which could be identified as focal carcinoma, measuring less than 1 mm in diameter; sporadic (15 cases, 15%) and singular (30 cases, 30%). These atypical cells were located mainly within sheet-like nests of tumor cells but not in chondroid or fibro-hyaline foci. Immunohistochemically, most of the atypical cells were positive for p53 gene products and PCNA.

CONCLUSION

The results indicated that atypical cells with p53 protein accumulation in their nuclei could be regarded as cells in a precancerous state not yet forming an apparent carcinomatous nest. Some cell population with these atypical cells are likely to form focal carcinomas and then to an apparent form of carcinoma in pleomorphic adenoma.

p53, mdm2, and p21 expression in oral squamous cell carcinomas: relationship with clinicopathologic factors

OBJECTIVE

The purpose of this study was to clarify the correlation of expression of cell cycle-associated gene proteins with clinicopathologic factors in oral squamous cell carcinoma (SCC).

STUDY DESIGN

Formalin-fixed paraffin-embedded tissues from 69 oral SCC cases and 10 normal mucosa cases were stained by immunohistochemistry (IHC) for p53, mdm 2, and p21 proteins.

RESULTS

We found p53, mdm 2, and p21 expression in 44 of 69 (63.8%), 25 of 69 (36.2%), and 37 of 69 (53.6%) oral SCCs, respectively. Ki-67-labeling index of combined p53(+)/mdm 2(+) expression cases was significantly higher than those that lacked combined expression (P =.004). Combined p53(+)/p21(+) expression showed a significant association with lymph node metastasis (P =.019). In survival analysis, combined p53(+)/p21(+) and p53(+)/mdm 2(+)/p21(+) expression was associated with poor clinical outcome (P =.018 and.012, respectively).

CONCLUSION

Combined p53/mdm 2 expression was associated with tumor proliferation in oral SCC. Combined p53/p21 and p53/mdm 2/p21 expression may be a predictive factor in lymph node metastasis.

Detection of TP53 mutation in ameloblastoma by the use of a yeast functional assay

BACKGROUND

Mutations in TP53 have been observed in a variety of tumors including oral lesions, though there are no reports in ameloblastomas. The purpose of the study was to examine the TP53 status of ameloblastomas using newly developed yeast functional assay whose accuracy and sensitivity has been proven to be higher than those of the previous DNA structure-based methods such as single strand conformation polymorphism (SSCP) analysis.

METHODS

TP53 status was analyzed by yeast functional assay and DNA sequencing in 12 cases of ameloblastoma which were diagnosed histologically and represented the clinical features of a benign tumor. After the extraction of RNA from the frozen tissue samples without microdissection, reverse transcription (RT)-PCR was carried out and these samples were used. The assay can detect mutations of p53 mRNA between codons 67 and 347 by the DNA-binding activity of the protein and reveal them as red colonies.

RESULTS

One case of 47-year-old male gave 17% red colonies of yeast and the other 11 cases gave 5.4% (mean; range, 3-8%). To confirm this result, we obtained other nine samples from the case of 17% red colonies, which contained or did not contain tumor tissues, and analyzed them by the assay. Seven samples that were histologically negative for tumor cells gave 4.7% red colonies (mean; range, 1-7%). Two samples that were histologically positive for tumor cells gave 20 or 46% of red colonies. The p53 plasmids were recovered from the red colonies of these three samples showing high red colony ratios and were subjected to sequencing analysis after purification. In all these samples, the same clonal mutation of TGT (Cys) 238 TAT (Tyr) was demonstrated.

CONCLUSIONS

These results suggest that TP53 mutation may be involved in molecular pathogenesis in a subset of ameloblastomas, though it is infrequent.

Bax, Bcl-2, and p53 expression in endometrial cancer

BACKGROUND

It has not been fully clarified whether alteration of Bax and other apoptosis-relating proteins of Bcl-2 and p53 is involved in endometrial carcinogenesis.

METHODS

A total of 56 frozen tissues, which included 14 normal endometria, 13 endometrial hyperplasias (10 without atypia and 3 with atypia), and 29 endometrial carcinomas, were examined for the expression of Bax, Bcl-2, and p53 using immunohistochemistry. For Bax-negative cases, PCR-direct sequencing was performed for the bax gene. For cases with p53 overexpression, mutational analysis was performed for the p53 gene using a yeast functional assay and sequencing.

RESULTS

Both Bax and Bcl-2 were distinctly expressed in the normal proliferative phase endometrium. A decreased Bcl-2/Bax ratio in the secretory phase endometrial gland cells due to suppressed Bcl-2 expression was observed. Bax expression was positive in all 13 endometrial hyperplasias, while it was absent in 6 of 29 endometrial carcinomas (20.7%). Negative Bax expression in endometrial carcinoma was not related to tumor stage, histologic subtype, or other histopathologic prognostic factors. Bax expression showed no relationship to either p53 overexpression or Bcl-2 expression. In the DNA of 6 Bax-negative cases, we found a frameshift insertion mutation at codon 58 (AAG to CAAG) in the BH3 domain despite the absence of mutation in the (G)8 tract, suggesting that this codon may be another preferred target for bax mutation other than the (G)8 tract. Mutational analysis was available for 7 of 10 cases with p53 overexpression, in which 5 cases were found to have a missense mutation and 2 cases had no mutation of the p53 gene. At least 10 of 29 (34.5%) cases of endometrial carcinoma were associated with sequence-verified mutation in the bax gene and/or p53 gene.

CONCLUSIONS

The bax gene frameshift mutation appears to cause a loss of Bax expression in endometrial carcinoma. Codon 58 may be a preferred target of bax gene mutation in endometrial carcinomas. The bax gene mutation seems to occur in the early stage of the genesis of a subset of endometrial carcinomas.

p53 as a potential predictive factor of response to chemotherapy: feasibility of p53 assessment using a functional test in yeast from trucut biopsies in breast cancer patients

Assessment of the predictive value of p53 requires the testing of large numbers of samples from patients enrolled in prospective phase III clinical trials. The goal of this study was to determine whether p53 status can be determined by p53 yeast functional assay using the limiting amounts of material that can typically be obtained in prospective phase III trials (particularly when chemotherapy is given before surgery). All patients presenting with a clinically palpable tumour which could be considered large enough to perform a trucut biopsy (> or =2 cm breast tumour) were eligible for this study. Two trucut biopsies and one incisional biopsy were performed on the surgical specimens (mastectomy or tumourectomy). Samples were snap frozen and cryostat sections were taken for histology and p53 testing. Thirty patients were included. Three samples out of 90 failed to give any p53 PCR products, probably because these samples contained almost entirely fibrous tissue. Of the 87 samples that could be tested, the incisional and trucut biopsies results were fully concordant in every case. p53 could be defined in 97% of patients by double trucut biopsy. Eight out of 30 tumours tested were mutant for p53 (27%). p53 status can be reliably determined by yeast assay from single frozen sections of trucut biopsies. Histological examination before p53 testing is essential to exclude cases where the p53 result may reflect only the status of the normal cells in the biopsy.

Suprabasal p53 immunoexpression is strongly associated with high grade dysplasia and risk for malignant transformation in potentially malignant oral lesions from Northern Ireland

AIMS

No good predictive marker for the malignant transformation of potentially malignant oral lesions (PMOLs) is currently available. This study re-evaluated the value of p53 immunoexpression to predict malignant transformation of PMOLs after discounting possible confounding factors.

METHODS

PMOLs from 18 patients who showed progression to carcinoma, 16 of the respective carcinomas, and PMOLs from 18 matched controls were evaluated by immunohistochemistry (IHC) for p53 expression. A mouse monoclonal antibody that detects wild-type and mutant forms of human p53 was used. The p53 immunostaining pattern was also correlated with the degree of dysplasia.

RESULTS

Suprabasal p53 staining was significantly associated with high grades of dysplasia (p < 0.01). The specificity and positive predictive value (PPV) for malignant transformation of suprabasal p53 staining were superior to the assessment of dysplasia, but sensitivity was inferior. All carcinomas derived from PMOLs with suprabasal p53 showed strong p53 immunostaining. However, the absence of suprabasal p53 staining and/or dysplastic changes did not preclude malignant transformation in a considerable proportion of PMOLs.

CONCLUSIONS

This study confirms and extends previous findings that suprabasal p53 immunoexpression has a high PPV for malignant transformation of PMOLs and can be used as a specific marker for lesions that are at high risk for malignant transformation. The absence of suprabasal p53 staining (that is, absence of, or basal, p53 staining) is non-informative for prognostic purposes. Because of its limited sensitivity, p53 IHC is not a substitute for the assessment of dysplasia in the evaluation of PMOLs. Instead, p53 IHC emerges as a clinically useful supplement of histopathological assessment in the prognosis of PMOLs.

Karyotypic heterogeneity and clonal evolution in squamous cell carcinomas of the head and neck

Head and neck squamous cell carcinomas (HNSCC) are often characterized by complex karyotypic changes, and a substantial proportion of the reported tumors have shown intratumor heterogeneity in the form of cytogenetically related (40%) or unrelated clones (20%). In order to study intratumor heterogeneity and to distinguish the temporal order of chromosome rearrangements in these tumors, two or more samples from different areas of the same tumor were separately examined in 19 HNSCC, yielding karyotypes from a total of 42 tumor samples. Intrasample heterogeneity was observed in 16 samples. Two samples displayed both related and unrelated multiple clones, four samples showed only multiple unrelated clones, and the remaining 10 samples had only related subclones. Intersample heterogeneity was detected in all but one tumor. Five tumors showed both cytogenetically related and unrelated multiple clones, 11 were found to have only related subclones, and the remaining two tumors showed only unrelated clones. Clonal evolution could be assessed in 13 tumors. A comparison of chromosome imbalances in different subclones from these tumors suggests that partial or entire loss of 3p, 8p, 9p, and 18q and gain of genetic material from 3q and 8q are likely to be early genetic events. In contrast, loss of 1q, 6p, 7q, and chromosome 10, as well as gain of chromosome arms 5p and 7p, are most probably later genetic events. One of the examined tumors contained two highly complex clones that were cytogenetically unrelated, indicating that this tumor had a multicellular origin.

Determination of optimal conditions for analysis of p53 status in leukemic cells using functional analysis of separated alleles in yeast

Tumor suppressor p53 is transcription factor that participates in control of many cellular functions. Somatic mutations of the p53 gene are frequently detected in human cancers. Several methods can be used for identification of p53 mutations, including FASAY - functional analysis of separated alleles in yeast. FASAY distinguishes yeast colonies expressing functional p53 protein from colonies producing a dysfunctional p53 protein simply on the basis of color. The validity of the method depends on a low background level. There are several sources of background as PCR-induced point mutations, low quality of RNA and alternative splicing of intron 9 affecting the p53 carboxy-terminus. In the present work we show that FASAY can be successfully used for analysis of mRNA isolated from blood samples that were collected and stored for 24 hours at 0 degrees C without undesired increase of background. We also measured fidelity of several commonly used DNA polymerases and determined the most suitable kinds of Pfu DNA polymerases for FASAY. Reaction conditions described in this report allow routine analysis of p53 status in leukemic cells using FASAY.

Dominant-negative mutation of p53 tumor suppressor gene in endometrial carcinoma

BACKGROUND

It has been suggested that mutation of the TP53 tumor suppressor gene is involved in endometrial carcinogenesis. However, the status of p53 function in endometrial cancers has not yet been investigated in detail.

METHODS

We surveyed inactivating p53 mutations in endometrial carcinomas using the yeast p53 functional assay, which can evaluate the transcriptional activity of p53 in vivo in yeast. To the detected p53 mutants, we also applied a transdominance assay, which assesses the dominant-negative property of mutants.

RESULTS

Of 23 endometrial carcinomas, 9 tumors (39.1%) were found to harbor p53 mutations. Only 1 of the 6 mutants in 18 endometrioid-type tumors showed dominant-negative capacity. In contrast to the endometrioid-type tumor, all 3 mutations in 5 serous-type tumors (R273H, 9-bp deletion in codons 240-243, and R248W) showed dominant-negative capacity and presented in a homozygous state in the tumors, indicating a complete functional inactivation.

CONCLUSIONS

Although this study included a relatively small number of cases and therefore is a preliminary study, these results suggest that the dominant-negative mutation of the TP53 gene is related to serous adenocarcinoma. The role of the dominant-negative status of p53 mutants in endometrial carcinogenesis and progression of this disease should be further investigated.

Quantitation of epidermal growth factor receptor gene amplification by competitive polymerase chain reaction in pre-malignant and malignant oral epithelial lesions

Abnormal amplification of epidermal growth factor receptor (EGFR) gene has been reported widely in various human tumors. However, the status of amplification of this gene in the process of carcinogenesis is not clearly defined. We used competitive polymerase chain reaction (PCR) to study whether EGFR gene is amplified and the degree of amplification in pre-malignant and malignant oral epithelial lesions, and also examined the relationship between EGFR gene aberration and the development of squamous cell carcinoma (SCC). Genomic DNA was extracted from paraffin sections of 17 cases of oral epithelial dysplasia (ED), four cases of carcinoma in situ (CIS), and 20 cases of untreated primary SCC. The extracted DNA was subjected to competitive PCR to amplify EGFR gene. Amplification of the EGFR gene was observed in three cases (17%) of ED, one case of CIS and four cases (20%) of SCC. In cases showing EGFR gene amplification, the degree of amplification was low in ED and CIS cases, whereas it was extremely high in SCC cases. These results suggest that amplification of EGFR gene occurs in the relatively early stage of the development of oral SCC. However, a high level of EGFR gene accumulation probably plays an important role in the progression to invasive cancer.

Development of a yeast stop codon assay readily and generally applicable to human genes

We established a yeast-based method to screen chain-terminating mutations that is readily applicable to any gene of interest. Based on the finding that 18- to 24-base-long homologous sequences are sufficient for gap repair in vivo in yeast, we used a strategy to amplify a test-gene fragment with addition of 24-bp sequences homologous to both cut-ends of a yeast expression vector, pMT18. After co-transformation with the amplified fragment and the linearized pMT18, each yeast (Saccharomyces cerevisiae) cell automatically forms a single-copy circular plasmid (because of CEN/ARS), which expresses a test-gene::ADE2 chimera protein. When the reading frame of the test-gene contains a nonsense or frameshift mutation, truncation of the chimera protein results in lack of ADE2 activity, leading to formation of a red colony. By using a nested polymerase chain reaction using proofreading Pfu polymerase to ensure specificity of the product, the assay achieved a low background (false positivity). We applied the assay to BRCA1, APC, hMSH6, and E-cadherin genes, and successfully detected mutations in mRNA and genomic DNA. Because this method--universal stop codon assay--requires only 4 to 5 days to screen a number of samples for any target gene, it may serve as a high-throughput screening system of general utility for chain-terminating mutations that are most prevalent in human genetic diseases.

Induction of apoptosis in melanoma cell lines by p53 and its related proteins

Melanoma cells rarely contain mutant p53 and hardly undergo apoptosis by wild-type p53. By using recombinant adenoviruses that express p53 or p53-related p51A or p73beta, we tested their apoptotic activities in melanoma cells. Yeast functional assay revealed a mutation of p53 at the 258th codon (AAA [K] instead of GAA [E]) in one cell line, 70W, out of six human melanoma cell lines analyzed (SK-mel-23, SK-mel-24, SK-mel-118, TXM18, 70W, and G361). Adenovirus-mediated transfer of p53, p51A, and/or p73beta suppressed growth and induced apoptotic DNA fragmentation of SK-mel-23, SK-mel-118, and 70W cells. Interestingly, p51A induced DNA fragmentation in them more significantly than p53 and p73beta. By Western blotting we analyzed levels of apoptosis-related proteins in cells expressing p53 family members. Apoptotic Bax and antiapoptotic Bcl-2 were not significantly upregulated or downregulated by expression of p53, p51A, or p73beta, except for p53-expressing 70W cells, which contained a larger amount of Bax protein than LacZ-expressing cells. Activation of caspase-3 was demonstrated only in p51A-expressing SK-mel-118 cells. We show here that p51A can mediate apoptosis in both wild-type and mutant p53-expressing melanoma cells more significantly than p53 and p73beta. It is also suggested that in melanoma cells (i) cellular target protein(s) other than Bcl-2 and Bax might be responsible for induction of p51A-mediated apoptosis and (ii) caspase-3 is not always involved in the apoptosis by p53 family members.

Expression of apoptosis-related proteins, p53, and DNA fragmentation in sarcomas of the pulmonary artery

BACKGROUND

Apoptosis is a common feature in a variety of pathologic conditions. Induction of apoptosis through apoptotic stimuli such as, chemotherapy or radiation, presents new insights into tumor biology and therapy. In particular, members of the Bcl-2 family as well as the Fas system are known to be involved in the regulation of apoptosis in different tumor entities.

METHODS

In the current study, the expression of the apoptosis-related molecules p53, Bax, Bcl-2, Fas (CD95), Fas-Ligand and perforin was examined in 7 patients with a sarcoma of the pulmonary artery. Furthermore, the TUNEL-method for the detection of apoptotic cells was applied as well as sequencing of the p53 gene.

RESULTS

In the TUNEL assay, approximately 10% of the sarcoma cells displayed DNA fragmentation. In addition, Bax was expressed in tumor cells. Accumulation of p53 was evident in 4 of 7 patients (pAB 240 antibody), and 2 of them were positive for the pAB 1801 antibody. Only 1 case had a point mutation in Exon 5 of the p53 sequence. A few tumor cells showed a double labeling of Bax and p53. Bcl-2 could be detected only in tumor-associated lymphocytes. Finally, several lymphocytes could be stained with perforin, but none of the specimens showed a reactivity for Fas or Fas-Ligand.

CONCLUSION

The expression of Bax indicated a possible role of this molecule in programmed cell death in pulmonary sarcomas. The limited coexpression of Bax and p53 suggested that induction of Bax can occur independently of p53. The detection of perforin in lymphocytes suggested a possible role for this molecule in apoptosis of the sarcoma cells. In contrast, the Fas system did not seem to play an essential role in sarcomas of the great vessels.

Mutational analysis of the candidate tumor suppressor gene ING1 in Indian oral squamous cell carcinoma

ING1, a recently identified candidate tumor suppressor gene, involved in the p53 signaling pathway is mapped at chromosome 13q34. Since loss of heterozygosity at 13q34 has been reported in squamous cell carcinoma of head and neck, we screened for mutations in ING1 by polymerase chain reaction-single strand conformation polymorphism in 71 oral squamous cell carcinomas (OSCC) from India, 15 of which were known to harbor p53 mutations. A single polymorphism (G to A) was detected in 14 (19.7%) of the tumors analyzed. No mutation was observed in any of the 71 OSCCs analyzed. These results suggest that ING1 is not a target for mutational inactivation in OSCC of Indians.

Genotype-phenotype correlation in gemistocytic astrocytomas

OBJECTIVE

Gemistocytic astrocytomas often behave aggressively and carry the least favorable prognosis among diffuse astrocytomas. The frequency of p53 mutations has been reported to be significantly higher in the gemistocytic variant as compared with other astrocytomas.

METHODS

Between 1985 and 1998, we selected 25 tumor samples from among 201 samples from patients with gemistocytic astrocytomas operated on at the Mayo Clinic. Exons 5 to 8 of the p53 gene were sequenced using an automated deoxyribonucleic acid sequencer. Morphometric characterization of individual gemistocytes was performed using an image analysis program.

RESULTS

Of 25 tissue samples analyzed, 16 were found to carry a p53 missense mutation (three in exon 5, three in exon 6, one in exon 7, and nine in exon 8), and one sequence variant was synonymous. Mutations were clustered at codons 151 (2 of 17 mutations), 193 (3 of 17 mutations), and 273 (5 of 17 mutations) of the p53 gene. Patients whose tumors carried a p53 mutation were significantly younger than other patients, and their tumors tended to accumulate more p53 protein than those of other patients. Phenotype analysis of gemistocytes revealed that the sizes of tumor cell nuclei and of entire tumor cells in the same tissue area were positively correlated. Smaller tumor cell nuclei tended to be less circular or more atypical. In addition, more atypical gemistocytes were found in tumors lacking a wild-type p53 allele as well as in tissue from patients whose postoperative survival was shorter.

CONCLUSION

Our data confirm that the frequency of p53 mutations is significantly higher (approximately twofold) in gemistocytic astrocytomas as compared with other astrocytoma subtypes. Whether the high frequency of p53 mutations contributes to the more aggressive behavior of gemistocytic astrocytomas, however, remains unclear.