K-ras Gene Mutations in Liver Carcinomas from a Mediterranean Area of Spain

The prevalence of human liver cancer shows a broad spectrum of variation in distinct geographical regions, depending on different risk factors, and their pathogenesis is poorly understood. We study the significance of molecular alterations of K-ras gene in human liver carcinomas in a low-incidence region such as a Mediterranean area of Spain (Valencia and Gerona). Our results reveal a low incidence of K-ras codon 12 mutations in hepatocellular carcinomas (HCC) and a higher incidence in cholangiocarcinomas (CCC). Similar results have been obtained in high-risk areas. We conclude that K-ras gene mutations are not a major event in the malignant transformation of hepatic cells in this region of the Mediterranean but that molecular implications of hepatocellular and cholangiocarcinomas appear to be different. Int J Surg Pathol 8(4):267-270, 2000     

p53 Alterations in thymic epithelial tumours

 The prognosis of thymic epithelial tumours depends on malignant behaviour that cannot always be predicted on histological grounds. This study aimed at identifying a molecular marker that would be useful in overcoming the drawbacks of histopathology. Forty-four thymic epithelial tumours were analysed for alterations of the tumour suppressor gene p53 using immunohistochemistry (antibodies D0-1 and CM-1) and PCR-based single-strand conformation polymorphism and DNA sequencing. Histological and clinical evaluation and also p53 analysis revealed three major tumour groups: non-organotypic thymic carcinomas with frequent p53 alterations (7/9) and occurrence of p53 gene mutations (2/9); malignant thymomas with frequent p53 alterations but without p53 gene mutations (11/18); and benign thymomas with rare p53 alterations and without p53 gene mutations (2/17). In non-organotypic thymic carcinomas p53 was detected with both antibodies. In contrast, thymomas lacked immunoreaction with D0-1 suggesting alteration of the antibody-binding site. Overall immunohistochemical results correlated with clinical stages (P < 0.01), pathohistology (P < 0.01), and survival times (P < 0.05). We consider immunohistochemical p53 detection to be a useful new prognostic factor for the evaluation of thymic epithelial tumours. Received: 5 September 1996 / Accepted: 17 February 1997     

Prognostic significance of p53 gene mutations and p53 protein expression in synovial sarcomas

Alterations to p53 seem to be of prognostic significance in soft tissue sarcomas, but their significance for synovial sarcomas has not been studied. We analysed 34 synovial sarcomas in 19 patients for p53 alterations (p53 gene mutations + p53 immunopositivity) and examined this factor for its prognostic value in a group of 15 primary tumours. DNA was prepared from paraffin-embedded tumour material by a modified proteinase K/phenol/chloroform extraction. p53 gene mutations of exons 5–8 were analysed by the PCR-SSCP-sequencing method. p53 protein expression was evaluated by immunohistochemistry using the murine monoclonal antibody DO1. We found two missense mutations (5.9%) and ten p53 immunopositive cases (29.4%). Both tumours with p53 mutations showed p53 protein expression. There was no significant correlation between p53 alteration and histological subtype, age, sex, or tumour size. The 5-year survival rate was 24.1%. Overall survival was significantly reduced in patients having synovial sarcomas with p53 alterations (P<0.001). In the multivariate Cox’s analysis, only p53 alterations (P=0.032) and tumour size (P=0.023) emerged as independent prognostic factors. We suggest that p53 alterations may be a useful prognostic indicator in synovial sarcomas, allowing rational clinical treatment and follow-up. Received: 13 April 1999 / Accepted:18 May 1999     

Absence of p53 Alterations in Nasopharyngeal Carcinoma Spanish Patients with Epstein–Barr Virus Infection

The objective of this study was to analyse the relationships between the Epstein–Barr virus (EBV) infection and the molecular abnormalities of the p53 oncoprotein in the nasopharyngeal carcinoma (NPC). Fifty-five NPC paraffin samples from a group of Spanish patients with EBV demonstrated presence by nested-PCR and non-isotopic in situ hybridisation, were analysed for p53 expression using immunohistochemistry. The positive samples by immunohistochemistry were studied for p53 gene alterations in the exon 5 by single strand conformation polymorphism (SSCP). Among the 55 specimens, 14 (25.5%) showed expression of p53 protein. All these positive samples corresponded to the late stage of the tumour. Of the 14 samples, p53 gene alterations were found only in three cases using SSCP. These results indicate that the p53 mutations are an infrequent event in NPC in Spanish patients needing exogenous factors as the EBV infection for the development of this malignancy.     

Lowp53 protein expression in salivary gland tumours compared with lung carcinomas

Summary Fifty-one salivary gland tumours (23 pleomorphic adenomas, 5 Warthin's tumours, 12 mucoepidermoid carcinomas, 7 adenoid cystic carcinomas, 3 undifferentiated carcinomas and 1 acinic cell tumour) and 27 lung carcinomas (18 squamous cell carcinomas, 6 adenocarcinomas and 3 small cell carcinomas) were analysed immunohistochemically for the expression ofp53 nuclear phosphoprotein. Eight out of 51 (16%) salivary gland tumours werep53 positive. Three of these were benign and 5 malignant. All 3 benign salivary gland tumours were pleomorphic adenomas and expressed only occasional nuclear positivity with less than 1% of tumour cells positive. Of the 5p53-positive malignant tumours, 3 were mucoepidermoid carcinomas and 2 undifferentiated carcinomas. The malignant salivary gland tumours expressed more than 1% of positive nuclei in every case. Seventeen lung carcinomas werep53 positive (63%). Thirteen of these were squamous cell carcinomas, 3 were adenocarcinomas and 1 small cell lung carcinoma. The results show that mutations of thep53 gene may be infrequent in salivary gland tumours when compared with lung carcinomas. The relatively indolent course of some histological types of malignant salivary gland tumours could be associated with the preservation of the non-mutatedp53 gene in most of these tumours. The presence ofp53 positivity in some pleomorphic adenomas might, on one hand, suggest thatp53 gene alterations are also present in these tumours; on the other hand, the accumulation of thep53 protein in these tumours might also be due to some unknown mechanism, not necessarily related top53 gene mutation.     

Comparative analysis ofp53 protein immunoreactivity in prostatic,lung and breast carcinomas

Summary In this study we analysed the expression ofp53 protein in a total of 143 carcinomas immunohistochemically. These consisted of 34 prostatic adenocarcinomas, 59 lung and 50 breast carcinomas. In 28 cases, an average of 2–3 additional sections from different tumour areas were analysed. Forty-nine of the 143 carcinomas (34%) showed typical nuclear immunoreactivity by immunohistochemical staining with thep53 antibody CM-1. Two of the 34 prostatic carcinomas (6%) werep53 positive while 25 of the 59 lung carcinomas (43%) and 22 of the 50 breast carcinomas (44%) showed positivity forp53. By grade: 49% of grade III tumours, 36% of grade II and 5% of grade I tumours werep53 positive. There were significantly morep53-positive cases in grade II–III tumours than in grade I tumours (P= 0.001) when all tumours were taken into account. Further, there were significantly morep53-positive cases in grade III than in grade I–II tumours (P=0.001). In lung tumours there were significantly morep53-positive cases in grade II–III tumours than in grade I tumours (P=0.018). Similarly, there were significantly morep53-positive tumours in grade III breast tumours than in grade I–II tumours (P=0.003). The low incidence ofp53 positivity in prostate carcinomas suggests that mutations of thep53 gene are not as frequent in the neoplastic transformation of these tumours as in lung or breast carcinomas. The association ofp53 positivity with tumours of higher grade suggests thatp53 mutations lead to tumours of a more aggressive type. The analysis of tumours by multiple sections indicates thatp53 positivity is not evenly distributed in tumour tissue. Therefore, analysis of additional tumour areas may reveal positivity some cases, which is not evident if only one section is studied.     

Comparison of benign and malignant endometrial lesions for their p53 state, using immunohistochemistry and temperature-gradient gel electrophoresis

The aim of this study was to evaluate the presence and distribution of p53 alterations in pure endometrioid adenocarcinomas (n=120) of different grades and stages, as opposed to normal endometrium (n=13) and various risk groups of hyperplasia (n=39). All samples were initially analysed by immunohistochemistry with the monoclonal antibody Ab-6. Normal endometria were negative. With increasing degrees of malignancy, the number of cases with p53 accumulation rose and ranged from 9% to 18% in hyperplasia, through 25% in lowgrade carcinomas (G1), to 69% in high-grade carcinomas (G3). This increase was also seen when comparing tumours by stage. Of carcinomas in stage IA, only 17% showed p53 immunostaining, in contrast with 72% in stage IC. Of this material, 34 carcinomas and 8 hyperplasias were analysed for p53 mutations in exons 5–8 by means of polymerase chain reaction and temperature-gradient gel electrophoresis (TGGE). In none of 5 hyperplasia and 6 of 12 carcinomas showing p53 accumulation by immunohistochemistry, p53 mutations were detected by TGGE. In contrast, 4 of 22 carcinomas harboured mutant p53 but were negative by immunohistochemistry. Immunohistochemical and molecular investigations revealed that p53 alterations are related to the standard prognostic markers of endometrial cancer, i.e. grading and staging. TGGE, an indirect screening procedure for p53 mutations, is used to detect the type of p53 alteration and may provide additional insight into the complex figure of p53 abnormalities in the development and progression of malignant endometrial lesions.     

No correlation of c-myc overexpression and p53 mutations in liposarcomas

 Although it is well known that oncogenesis is a multistep process involving the activation of normal cellular genes to become oncogenes and/or the inactivation of tumor suppressor genes, this process has seldom been investigated in soft tissue tumours. We screened a group of 36 liposarcomas for genetic abnormalitis in the p53 tumour suppressor gene and c-myc oncogene. Altered c-myc gene expression was examined by differential RT-PCR assay. p53 Gene mutations in exons 4–8 were analysed by using PCR-SSCP analysis and direct sequencing. Elevated c-myc expression was found in 6 of 31 liposarcomas (19.4%). p53 Gene mutations were observed in 5 of 36 liposarcomas (13.9%). Both genetic alterations were associated with the histological subtype of liposarcomas. Whereas c-myc gene expression was a characteristic of myxoid/round cell liposarcomas, p53 gene mutations were found more frequently in pleomorphic variants. Liposarcomas of the well-differentiated subtype showed neither p53 gene mutations nor altered c-myc gene expression. Our results indicate that the c-myc oncogene and the p53 tumor suppressor gene do not seem to cooperate in the oncogenesis of liposarcomas. Received: 22 April 1998 / Accepted: 11 May 1998     

Coexpression of p53 and c-erbB-2 proteins is associated with histological type, tumour stage, and cell proliferation in malignant salivary gland tumours

The development and progression of cancer are known to be regulated by various oncogenes and tumour suppressor genes. We analysed 63 primary malignant salivary gland tumours for the expression of p53 and c-erbB-2 proteins. Immunohistochemically, 7 of 63 tumours (11%) showed diffuse nuclear staining for p53 protein, and all 7 were also positive for c-erbB-2 protein. The overexpression of p53 protein correlated closely with the overexpression of c-erbB-2 protein (P<0.001). Overexpression of both p53 and c-erbB-2 proteins (coexpression) was found in tumours of certain histological types, such as adenocarcinoma, carcinoma in pleomorphic adenoma, and salivary duct carcinoma. Furthermore, it is noteworthy that coexpression was associated with high-grade carcinoma, advanced tumour stage, and a high Ki-67 labelling index (%) which is a marker of cell proliferation. In adenocarcinoma, we attempted to clarify the relationship between coexpression and histological grade. Coexpression was associated with histological grades showing high mitotic indices and necrotic areas, which reflected high cell-proliferative activity. These results suggest that the accumulation of genetic alterations, such as those involving p53 and c-erbB-2, plays an important part in the progression of malignant salivary gland tumours.     

DETECTION OF p53 AND bcl-2 PROTEIN IN CARCINOMA OF THE RENAL PELVIS AND URETER INCLUDING DYSPLASIA

Ninety-four patients with transitional cell carcinoma (TCC) of the renal pelvis and ureter, including dysplastic lesions, were studied for p53 and bcl-2 protein expression by immunohistochemistry. Twenty-one patients were also studied for p53 gene mutations by direct sequencing and for bcl-2 gene rearrangement by Southern blot analysis. Overexpressed p53 protein was detected in 26 cases (27·7 per cent). bcl-2 immunostaining was observed in 21 tumours (22·3 per cent), including four cases with labelling for p53. Furthermore, the dysplastic lesions surrounding 19 p53-positive tumours also stained for p53. bcl-2 expression was also detected frequently in dysplastic lesions adjacent to 14 bcl-2-positive TCCs. Positive reactions of dysplastic lesions were also found adjacent to 37 bcl-2-negative tumours. p53 point mutation was detected in 6 of 21 cases. Five of the six cases were positive for p53 protein. bcl-2 positivity was detected in 3 of 21 tumours, without bcl-2 gene rearrangements in the major breakpoint region. Overexpressed p53 protein was frequently detected in both high-grade ( P <0·05) and invasive tumours ( P <0·05). In three cases of p53-positive non-papillary invasive tumours, bcl-2 was found in non-invasive portions, but was not present in invasive areas. These findings suggest that overexpression (mutation) of p53 and/or bcl-2 protein may be early events in tumourigenesis and that p53 alterations in particular are essential for the maintenance of a malignant phenotype in tumour development.     

p21 Expression in colorectal carcinomas: a study on 103 cases with analysis of p53 gene mutation/expression and clinic-pathological correlations

The WAF1/CIP1 gene product, p21, an inhibitor of cyclin-dependent kinases, is a critical downstream effector in the p53 pathway. The expression of p21 in human neoplasms is heterogeneous, and may be related to p53 functional status. We evaluated p21 immunoreactivity in 103 colorectal carcinomas (CC) in relation to the p53 gene and protein alterations and clinico-pathologic parameters. High p21 expression (more than 10% reactive cells) was seen in 39% of cases. p21 staining was heterogeneous and often detected in clusters of tumour cells; in some tumours p21 staining was more pronounced in superficial areas. No relation was seen between p21 immunoreactivity and site of the tumours (right vs left), TNM stage and grade. p21 expression was related to p53 status as evaluated with IHC or with SSCP analyses, low p21 expression usually being associated with p53 protein overexpression (P=0.048) and p53 gene alteration (P=0.005). The strongest associations were seen when the combined p53/p21 immunophenotype was compared with p53 gene alterations (P=0.0002). These data support the hypothesis that p21 expression in CC is mainly related to p53 functional status, suggesting that p21 expression could be an interesting adjunct in the evaluation of the functional status of the p53 pathway in CC. Received: 22 February 1999 / Accepted: 21 June 1999     

Molecular analysis of p53 gene in laryngeal premalignant and malignant lesions. p53 protein immunohistochemical expression is positively related to proliferating cell nuclear antigen labelling index

This study was undertaken in order to investigate the molecular nature of the p53 gene in 19 laryngeal squamous cell carcinomas and dysplasias. Moreover, we have examined the possible relationship between proliferating cell nuclear antigen (PCNA) expression and p53 protein detection status in 42 laryngeal premalignant and malignant lesions in which 14 of the 19 samples used in the molecular study were included. p53 gene analysis was performed with the single-strand conformation polymorphism technique. PCNA was stained with the peroxidase/antiperoxidase immunohistochemical method using the monoclonal antibody PC-10. Data from previous work concerning p53 expression was used. We found that 9 of 12 of the immunohistochemically p53 positive (+) cases had mutations in exons 5 or 6. In the remaining immunohistochemically p53(+) and p53 negative (–) specimens there was no indication of sequence alterations. Furthermore, we did not observe any deletions in the chromosomal region 17p31.1 which encodes exons 4–8 of the p53 gene. The PCNA labelling index (LI) increased progressively with p53 protein detection status (percentage of cells immunohistochemically positive for p53). The difference between the group with the higher percentage of p53(+) cells and the others was statistically significant. These data show that although there is a discrepancy between immunohistochemical demonstration of p53 and molecular analysis, a large proportion of the former harbours the mutant form of the protein. In addition, p53 overexpression is positively correlated with PCNA LI, a finding which accompanies tumour progression.     

DNA ploidy and MYC DNA amplification in ovarian carcinomas

There is increasing evidence that DNA ploidy is a prognostic factor in ovarian carcinomas, but it is uncertain whether MYC DNA amplification is an epiphenomenon of DNA nondiploidy or a distinct biological change with an impact on the clinical course of the disease. To clarify these issues we analysed DNA ploidy by flow and image cytometry and MYC copy number by polymerase chain reaction in archival material from ovarian carcinomas with known follow up. The results were compared with proliferative activity (Ki67 index) and p53 and bcl-2 expression. DNA cytometry revealed nondiploidy in 84 of 144 cases (58.3%). Nondiploidy was statistically significantly correlated with histological tumour type, histological grade, Ki67 index >10%, FIGO stage, presence of residual tumour after debulking surgery and adverse postoperative outcome. Furthermore, DNA nondiploidy was associated with p53 accumulation. We found that 84.9% of the p53-positive cases were nondiploid. This points to the paramount importance of wild type p53 for the maintenance of genome integrity in this tumour type. MYC DNA amplification was seen in 33.8% (26/77 cases) of ovarian carcinoma. There was no correlation between MYC DNA amplification and histological tumour type, histological grade, FIGO stage, DNA ploidy, proliferative activity or prognosis. However, when p53 and bcl-2 expression was taken into account, a statistically significant correlation between gene alteration or expression patterns and histological tumour type was revealed. The group of mucinous carcinomas demonstrated both MYC DNA amplification and strong bcl-2 expression in 50% and contained the largest fraction of cases without aberration (37.5%). Endometrioid carcinomas were characterized by strong bcl-2 expression in 85%, whereas serous and undifferentiated carcinomas predominantly exhibited p53 alterations, frequently accompanied by bcl-2 overexpression or MYC DNA amplification. Thus, in interaction with other genes MYC DNA amplification may play a role in the determination of the varying differentiation patterns of ovarian carcinomas.     

Molecular and immunohistochemical analysis of p53 mutations in scrapings and tissue from preinvasive and invasive breast cancer

 Mutations of the p53 gene appear to be one of the most common abnormalities in human cancer. Although many studies have been published about p53 alterations in breast cancer, data on molecular biological detection of p53 mutations in in situ lesions are still rare, and the implications for breast cancerogenesis are unclear. Tissue samples from 83 patients with different stages of breast cancer and from 13 patients with benign breast lesions were screened for p53 gene mutations by polymerase chain reaction (PCR) followed by temperature-gradient gel electrophoresis (TGGE). p53 protein accumulation was analysed by immunohistochemistry (IHC). Samples were gained from fresh-frozen tissue, scrapings, or paraffin embedded tissue. Additionally, 23 pairs of primary tumours and corresponding lymph nodes were examined. p53 gene aberrations were found in 55.7% of the infiltrating carcinomas, in 31.5% of the ductal carcinomas in situ (DCIS) and in one atypical ductal hyperplasia. A positive correlation was seen with high-grade tumours and with comedo. There was no statistically significant relationship with respect to age, menopausal status, tumour size, hormone receptor status or lymphatic invasion. Concordance between TGGE and IHC was seen in only 63% of the cases analysed. However, with regard to p53 mutation screening by TGGE, a high significance (P = 0.0008) was seen between standard tissue extraction and our scrape preparation technique. Among 8 pairs of primary tumours and their corresponding lymph node metastases, only 3 harbored identical p53 mutations in the same exon, while in 5 cases with mutant p53 in the primaries, no mutation was seen in the lymph node. Our data indicate that p53 mutations are frequent in breast tumours associated with unfavorable prognosis, including high-grade or the comedo histotype. There is evidence that p53 gene alterations occur early in breast cancerogenesis, as mutations were detected not only in in situ carcinomas but also in atypical ductal hyperplasia. Received: 14 April 1997 / Accepted 20 May 1997     

Dermatofibrosarcoma protuberans with fibrosarcomatous areas

 Fibrosarcomatous (FS) change in a rare, but well-known phenomenon encountered in dermatofibrosarcoma protuberans (DFSP), and an increased chance in an adverse outcome has been suggested in patients with DFSP having FS areas (DFSP-FS). As altered p53 pathway has been suggested as having a potential role in tumour progression, we analysed the p53 gene and p53 protein together with the p53-related protein mdm2 and p21^Wafl in 5 cases of DFSP-FS and 13 of DFSP to ascertain whether the p53 pathway correlates to the fibrosarcomatous transformation of DFSP. Three of the five DFSP-FSs overexpressed p53 protein immunohistochemically, and one of them had a ”missense” mutation of the p53 gene without immunohistochemical overexpression of mdm2 or p21^Wafl. The other two DFSP-FSs with p53 overexpression demonstrated increased labelling indices of both mdm2 and p21^Wafl. The three DFSP-FS patients with overexpression of p53 protein had frequent local recurrences, ranging from 3 to 5 in number with increasingly short intervals (mean 4.5 years), while one of the other two had no recurrences and the other, only one. None of the 13 DFSPs showed any alterations in the p53 gene or overexpressions of p53, mdm2 and p21^Wafl, except for one DFSP having a ”silent” mutation of the p53 gene. Three DFSPs had local recurrences once or twice with longer intervals to recurrence (mean 10.3 years). Although the number of cases examined is limited, the results suggest that alterations in the p53 pathway, such as overexpression of p53 protein by a mutated gene and mdm2 overexpression, are involved in fibrosarcomatous transformation in a subset of fibrohistiocytic tumours and possibly correlated with its more locally aggressive behaviour than that without p53 alterations or ordinary DFSP. Received: 21 January 1998 / Accepted: 25 March 1998     

Frequency and spectrum of p53 mutations in gastric cancer — a molecular genetic and immunohistochemical study

The p53 tumour-suppressor gene plays an important role in gastric carcinogenesis. In an analysis of the spectrum of mutations of the p53 gene seen in 56 primary gastric carcinomas of various types and grades of differentiation, the entire coding sequence (exons 2–11) of the p53 gene was screened by single-strand conformation polymorphism analysis and direct genomic sequencing of polymerase chain reaction products. Intragenic restriction site polymorphisms and the probe YNZ22 were used for the detection of loss of heterozygosity (LOH) of the p53 gene locus on chromosome 17p. p53 overexpression was studied with the anti-p53 antibody CM-1. A total of 21 somatic alterations of the p53 gene were found. Twenty were base-pair substitutions, and one was an eight base-pair deletion. Six tumours with p53 mutations revealed LOH. Abnormalities in p53 expression were found in 17 tumour samples, of which 16 had gene mutations. The spectrum of mutations observed was consistent with the predicted spectrum for dietary mutagens associated with the metabolism of nitrogenous compounds, resulting in deamination of nucleic acids. Our findings suggest that p53 could be a primary target for mutations associated with dietary carcinogens in gastric carcinogenesis.     

Mutation of the transforming growth factor-β type II receptor gene in right-sided colorectal cancer: relationship to clinicopathological features and genetic alterations

The presence of inactivating mutations in the transforming growth factor-β (TGF-β) type II receptor (RII) gene in colon cancer suggests that it may behave like a tumour suppressor gene. RII is mutated in the majority of colon tumours exhibiting widespread microsatellite instability, a characteristic generally referred to as the replication error phenotype (RER+). We investigated the association between RII mutations and various clinicopathological variables and genetic alterations in a large series of sporadic adenocarcinomas arising in the proximal colon. RII mutations were found in 17 per cent (36/210) of right-sided tumours and in 86 per cent (32/37) of those displaying RER+. They were associated with the absence of lymph node invasion (P=0·04), poor histological differentiation (P=0·006), and with a trend for improved patient survival. Tumours with an RII mutation also showed non-significant trends for a lower incidence of p53 protein overexpression and of p53, K-ras, and APC gene mutation compared with tumours with normal RII. These results indicate that right-sided colorectal tumours containing RII mutations resemble those with the RER+ phenotype in terms of their clinicopathological features and genetic alterations. © 1998 John Wiley & Sons, Ltd.     

Pancreatic endocrine tumours: evidence for a tumour suppressor pathogenesis and for a tumour suppressor gene on chromosome 17p

Two molecular pathways leading to cancer are known. Common-type cancers arise from the ‘tumour suppressor’ pathway, characterized by gross chromosomal changes and allelic losses (LOH) in an average of 25 per cent or more of randomly chosen chromosomal loci. The ‘mutator pathway’ has been recognized in a subset of cancers, characterized by widespread microsatellite DNA instability and rarity of chromosomal losses. The present study has investigated 20 pancreatic endocrine tumours (PETs) for loss of heterozygosity (LOH) at seven chromosomal loci (3p14, 7q31–32, 11q13, 13q14, 18q21, 17p13, and 17q21); microsatellite instability; and Ki-ras, N-ras, and p53 gene mutations. LOH was found in an average of 24 per cent of the chromosomal loci analysed. No tumour showed microsatellite instability. Ki-ras and p53 mutations were each found in one case. The frequency of losses was higher in malignant (40 per cent) than in benign (17 per cent) tumours (p=0·009), and the specific chromosome 17p13 LOH was associated with extrapancreatic extension of disease (p=0·007), high proliferative activity (p=0·001), and absence of progesterone receptors (p=0·01). A common deleted region on chromosome 17p13 and the rarity of p53 gene mutations suggest the existence of a novel tumour suppressor gene involved in the pathogenesis of PETs in this chromosomal area. © 1998 John Wiley & Sons, Ltd.     

Genetic alterations associated with the evolution and progression of astrocytic brain tumours

Diffusely infiltrating low-grade astrocytomas (WHO grade II) have an intrinsic tendency for progression to anaplastic astrocytoma (WHO grade III) and glioblastoma (WHO grade IV). This change is due to the sequential acquisition of genetic alterations, several of which have recently been identified. In low-grade astrocytomas, p53 mutations with or without loss of heterozygosity on chromosome 17p are the principal detectable change. Anaplastic astrocytomas contain p53 mutations at an overall incidence of 34% and, in addition, loss of heterozygosity on chromosome 19q and frequent homozygous deletion of the p16 tumor suppressor (MTS-1) gene. The most malignant astrocytic neoplasms, the glioblastoma, further shows loss of chromosome 10 and amplification of the epidermal growth factor receptor (EGF-R) gene at overall incidences of 66% and 34%, respectively. The type and distribution of p53 mutations in astrocytic brain tumours are not suggestive of specific environmental carcinogens operative in their aetiology. Analysis of 91 families with p53 germline mutations reported to date show that tumours of the nervous system account to 12% of all neoplasms. Of a total of 57 brain tumours reported, 30 were classified histologically and of these, 73% were of astrocytic origin. The observation that somatic p53 mutations in sporadic brain tumours are largely restricted to those of astrocytic origin and that astrocytomas also prevail among CNS neoplasms associated with p53 germline mutation strongly suggests, that p53 mutations are capable of initiating neoplastic transformation in astrocytes of the human nervous system.     

TP53 alterations in relation to the cell cycle-associated proteins p21, cyclin D1, CDK4, RB,MDM2, and EGFR in cancers of the uterine corpus

In the present study, TP53 alterations have been analysed and compared with the expression of the proteins p21, cyclin D1, cdk4, RB, EGFR, and MDM2 in 53 cancers of the uterine corpus. TP53 gene mutations analysed by CDGE/DGGE and direct sequencing showed a TP53 gene mutation in 18 per cent of the cases. TP53 gene mutations were not significantly related to overexpression or down-regulation of any of the proteins. Immunohistochemically, there was an increased protein level of TP53 in 77 per cent, p21 in 36 per cent, cyclin D1 in 45 per cent, cdk4 in 77 per cent, EGFR in 8 per cent, and MDM2 in 32 per cent of the cases. Expression of RB protein was normal in all cancers. Significant association of protein expression was seen between TP53 and MDM2 (p = 0·005) and p21 and MDM2 (p = 0·001). Furthermore, there may be an association between TP53 and p21 (p = 0·038) and cyclin D1 and cdk4 (p = 0·045). The results revealed increased levels of TP53 protein in all MDM2-positive cases that did not show TP53 mutations, indicating TP53 protein stabilization and inactivation by complex formation with MDM2. In summary, the high number of cases showing an increased level of TP53 and cdk4 proteins suggests that these proteins play an important role in the neoplastic process in cancers of the uterine corpus. Copyright © 1999 John Wiley & Sons, Ltd.