Immunohistochemical expression of P53 tumor suppressor gene protein in adult germ cell testis tumors: clinical correlation in stage I disease

p53 and MDM2 expression in primary and metastatic testicular germ cell tumors: Association with clinical outcome

BACKGROUND

Testicular germ cell tumors (TGCTs) are highly sensitive to platinum-based chemotherapy, and wild-type p53 seems to play a pivotal role in this susceptibility. On the other hand, overexpression of MDM2 seems to entail treatment resistance and unfavorable prognosis.

OBJECTIVES

We aimed to describe p53 and MDM2 immunoexpression in a well-characterized cohort of primary and metastatic TGCTs and evaluate associations with clinicopathological and prognostic variables, including survival.

MATERIALS AND METHODS

237 primary tumor samples and 12 metastases were evaluated for p53 and MDM2 immunoexpression using digital image analysis. Clinical records of all patients were reviewed for baseline clinical/pathologic characteristics and follow-up.

RESULTS

A significant positive correlation between p53 and MDM2 H-scores was found (r_s  = 0.590, P < .0001). Non-seminomas showed significantly higher expression levels of both p53 and MDM2 (P = .0002, P < .0001), which peaked in embryonal carcinomas and choriocarcinomas. Percentage of immunoexpressing cells and H-score were significantly higher in chemo-treated metastases compared with chemo-naïve primary tumors for MDM2 (P ≤ .0001 for both), but not for p53 (P = .919 and P = .703, respectively). Cases with higher MDM2 immunoexpression showed a statistically significant trend for association with poorer prognosis (P = .043). Relapse/progression-free survival at 12 months post-diagnosis was lower in the "MDM2-high" (≥P50) vs. the "MDM2-low" (<P50) expression groups.

DISCUSSION AND CONCLUSION

In TGCTs, MDM2 overexpression may indicate a more aggressive tumor phenotype, with propensity for therapy resistance and recurrence. If validated in larger multi-institutional studies with precise quantification, it may be envisioned as a useful predictive biomarker of poor response to cisplatin.

Testicular cancer from diagnosis to epigenetic factors

Testicular cancer (TC) is one of the most common neoplasms that occurs in male and includes germ cell tumors (GCT), sex cord-gonadal stromal tumors and secondary testicular tumors. Diagnosis of TC involves the evaluation of serum tumor markers alpha-fetoprotein, human chorionic gonadotropin and lactate dehydrogenase, but clinically several types of immunohistochemical markers are more useful and more sensitive in GCT, but not in teratoma. These new biomarkers are genes expressed in primordial germ cells/gonocytes and embryonic pluripotency-related cells but not in normal adult germ cells and they include PLAP, OCT3/4 (POU5F1), NANOG, SOX2, REX1, AP-2γ (TFAP2C) and LIN28. Gene expression in GCT is regulated, at least in part, by DNA and histone modifications, and the epigenetic profile of these tumours is characterised by genome-wide demethylation. There are different epigenetic modifications in TG-subtypes that reflect the normal developmental switch in primordial germ cells from an under- to normally methylated genome. The main purpose of this review is to illustrate the findings of recent investigations in the classification of male genital organs, the discoveries in the use of prognostic and diagnostic markers and the epigenetic aberrations mainly affecting the patterns of DNA methylation/histone modifications of genes (especially tumor suppressors) and microRNAs (miRNAs).

A knowledge-based approach for predicting gene-disease associations

MOTIVATION

Recent advances of next-generation sequence technologies have made it possible to rapidly and inexpensively identify gene variations. Knowing the disease association of these gene variations is important for early intervention to treat deadly diseases and provide possible targets to cure these diseases. Genome-wide association studies (GWAS) have identified many individual genes associated with common diseases. To exploit the large amount of data obtained from GWAS studies and leverage our understanding of common as well as rare diseases, we have developed a knowledge-based approach to predict gene-disease associations. We first derive gene-gene mutual information by utilizing the cooccurrence of genes in known gene-disease association data. Subsequently, the mutual information is combined with known protein-protein interaction networks by a boosted tree regression method.

RESULTS

The method called Know-GENE is compared with the method of random walking on the heterogeneous network using the same input data. For a set of 960 diseases, using the same training data in testing in 3-fold cross-validation, the average recall rate within the top ranked 100 genes by Know-GENE is 65.0% compared with 37.9% by the state of the art random walking on heterogeneous network. This significant improvement is mostly due to the inclusion of knowledge-based mutual information.

AVAILABILITY AND IMPLEMENTATION

Predictions for genes associated with the 960 diseases are available at http://cssb2.biology.gatech.edu/knowgene

CONTACT

: skolnick@gatech.edu.

Primary mediastinal "thymic" seminomas

Over the last half century, our knowledge on germ cell tumors (GCT) has increased dramatically. Tumors that at one time were supposed to originate exclusively from certain anatomic areas are now thought to occur in ubiquitous distribution. Nevertheless, because of their similar histopathologic features, the conventional classic evaluation of these patients will require careful clinical history as well as complete physical and radiologic evaluation. The emphasis in this manuscript will be to highlight the occurrence and overall characteristics of one of the most common GCTs in the mediastinal region-seminoma. A more detailed discussion of mediastinal GCTs is well beyond the scope of this review.

The management of stage I nonseminomatous testicular germ cell tumors

Testicular germ cell tumors represent the most common malignancies in young males; 70% of patients with seminomas and 50% of those with nonseminomatous germ cell tumors (NSGCT) have clinical stage I at diagnosis. Lymphovascular invasion, embryonal-cell carcinoma component, absence of yolk sac histology and MIB1 proliferation rate represent predictors of micrometastatic diseasein stage I NSGCT. Therapeutic options following orchiectomy in patients with stage I NSGCT comprise nerve-sparing retroperitoneal lymph node dissection, surveillance or adjuvant cisplatin-based chemotherapy. All available treatment modalities produce excellent results, with a long-term survival of almost 100%. Consequently, therapy-induced toxicity is an important concern in the management of these patients. An individually tailored approach that takes into account the prognostic factor profile as well as the patient's preferences and their ability to comply with each one of the modalities is the key to the management of stage I testicular cancer.

Chromosomes, genes, and development of testicular germ cell tumors

A literature review found 265 articles on testicular germ cell tumors (TGCTs) detailing the copy number of chromosomal regions and expression of 245 genes. An initial precursor stage, intratubular germ cell neoplasia (IGCN), is characterized by triploidization and an upregulation of KIT, ALPP, CCDN2, and ZNF354A, and a downregulation of CDKN2D. TGCT regularly have a series of chromosomal aberrations: a decrease in copy number at 4q21 approximately qter and 5q14 approximately qter; an increase at 7p21 approximately pter, 7q21 approximately q33, and 8q12 approximately q23 (especially high increase in seminoma); a decrease at 11p11 approximately p15 and 11q14 approximately q24; an increase at 12p11 approximately pter; a decrease at 13q14 approximately q31; an increase of 17q11 approximately q21 (only for nonseminoma); a decrease of 18q12 approximately qter; and an increase at 21q21 approximately qter, 22q11 approximately qter (only for seminoma), and Xq. Macroscopically overt TGCT is associated with a characteristic series of abnormalities in the retinoblastoma pathway including upregulation of cyclin D2 and p27 and downregulation of RB1 and the cyclin-dependent kinase inhibitors p16, p18, p19, and p21. TGCT thus has a synergistic pattern in gene expressions of the retinoblastoma pathway that is rare in other malignancies.

Significance of p53 expression in immature teratomas

Twenty-nine pediatric immature teratomas were reviewed to determine the frequency and clinical significance of p53 expression. Tumors were stained for p53 expression by immunohistochemistry and results were correlated with the presence of other germ cell tumor elements and with outcome. Sequencing of p53 for mutations was performed on positive cases. Eighteen cases showed widespread positive p53 staining of the immature teratoma elements, 9 showed staining only in very occasional cells, and 2 cases showed no staining. Of the 18 positive cases, 5 recurred. All five were pure immature teratomas at diagnosis. Four recurred as immature or mature teratoma and one as a sarcoma; all except one showed frequent cells positive for p53 in the recurrent tumor. Another 5 of the 18 diffusely positive cases contained immature teratoma as well as other malignant germ cell elements at diagnosis; none of these recurred. None of the remaining eight cases with frequent positive cells, the nine cases with occasionally positive p53 staining, or the two cases with no staining recurred or demonstrated other germ cell tumor elements. We conclude that p53 expression is not unusual in immature teratoma and diffuse p53 immunopositivity is associated with recurrence or the presence of malignant elements in approximately 50% of cases. In only 1 of 29 cases tested was p53 immunopositivity associated with mutations in the p53 gene; hence, overexpression in the majority of cases is presumed to reflect increased half-life of the protein from undetermined stabilizing factors. Expression of p21, a p53 target gene, was only focal, suggesting impaired transcriptional activation by p53. The finding of frequent p53-positive cells in immature teratoma should prompt a search for malignant elements within the tumor and affected patients should be followed closely for evidence of recurrence.

Role of P53 and MDM2 in treatment response of human germ cell tumors

PURPOSE

Testicular germ cell tumors (TGCTs) of adolescents and adults are very sensitive to systemic treatment. The exquisite chemosensitivity of these cancers has been attributed to a high level of wild-type P53.

MATERIALS AND METHODS

To clarify the role of P53 in treatment sensitivity and resistance of TGCTs, we performed immunohistochemistry and Western blotting analysis on a series of 39 fresh-frozen primary TGCTs before therapy (unselected series). In a series of formalin-fixed paraffin-embedded TGCTs of patients with fully documented clinical course, including treatment-sensitive (n = 17) and -resistant (n = 18) tumors, P53 status was assessed by immunohistochemistry and mutation analysis. In addition, the involvement of MDM2, a P53 antagonist, was investigated by immunohistochemistry, reverse transcriptase polymerase chain reaction, and in situ hybridization.

RESULTS

Immunohistochemistry demonstrated absence of staining for P53 in 36%, 41%, and 17% of the unselected, responding, and nonresponding TGCTs, respectively. Of the positive TGCTs, most tumors, ie, 49%, 41%, and 33%, showed 1% to 10% positive nuclei. This overall low level of P53 was confirmed by Western blotting. Mutation analysis revealed only one silent P53 mutation in one of the responding patients. All embryonal carcinomas were homogeneously positive for MDM2, encoded by the full length mRNA, while a heterogeneous pattern was found for the other histologic components. Amplification of MDM2 was detected in one out of 12 embryonal carcinomas.

CONCLUSION

Although our results are in line with previous findings of the presence of wild-type P53 in TGCTs, they show that a high level of P53 does not relate directly to treatment sensitivity of these tumors, and inactivation of P53 is not a common event in the development of cisplatin resistance.

Apoptosis and proliferative activity in mature and immature teratomas of the mediastinum

BACKGROUND

Mediastinal teratomas are the most frequent mediastinal germ cell tumor. Whereas mature teratomas are benign tumors, immature teratomas are malignant. The purpose of this study was to find characteristics that could be used to distinguish between the growth and prognosis of the two teratoma types.

METHODS

Twenty-four mediastinal teratomas (18 mature and 6 immature) were examined for apoptosis by 3'-end labeling of DNA and stained immunohistochemically for proliferating cell nuclear antigen, Bcl-2, Bax, p53 protein, and alpha-fetoprotein (AFP) expression in formalin fixed, paraffin embedded specimens.

RESULTS

AFP was expressed in both immature teratomas and mature teratomas. Whereas p53 protein was expressed by most teratomas, p53 gene mutation was observed in only one patient with an immature teratoma in which the same mutation occurred in all tumor tissue components tested. Bax protein expression was relatively diffuse in mature teratomas but was focally expressed in immature teratomas. Bcl-2 protein was expressed focally in both mature and immature teratomas. Although the proliferative index was significantly higher in immature teratomas compared with mature teratomas (P < 0.001), the apoptotic index (AI) was significantly higher in mature teratomas compared with immature teratomas (P < 0.05). All patients except one in this study remain alive and disease free after undergoing tumor resection.

CONCLUSIONS

The relatively high AI in mature teratomas may be due to the overexpression of the p53 protein. In contrast, immature teratomas exhibited higher proliferative activity and lower rates of apoptosis, which may explain the more aggressive behavior of these tumors. However, patients with immature mediastinal teratomas have a good prognosis if the tumor is resected completely after chemotherapy.

p53: a good diagnostic marker for intratubular germ cell neoplasia, unclassified

Intratubular germ cell neoplasia, unclassified (IGCNU) is a precursor of germ cell tumors (GCT) of the testis. In routine histologic sections, neoplastic intratubular germ cells may be very few and easily overlooked. The aim of this study is two-fold: to establish the immunohistochemical pattern of expression of p53 in IGCNU and GCT and to determine whether p53 can be used as a marker for IGCNU. Resection specimens from 14 seminomas, 14 mixed germ cell tumors (MGCT), 3 embryonal carcinomas, 2 mature teratomas, 7 IGCNUs, and 11 normal testes were stained for p53. Normal germ cells and Sertoli cells of the seminiferous tubules in all normal testes were negative for p53. The tumor cells of all IGCNU cases were positive for p53. All invasive components of mixed germ cell tumors, embryonal carcinomas, and seminomas exhibited expression of p53. Mature teratoma components were negative for p53. These findings indicate that p53 is a highly sensitive marker of IGCNU and highly specific in distinguishing lesional tissue from normal seminiferous tubules. The current findings also suggest that p53 may be involved as an early step in the malignant progression of most germ cell neoplasias.

Immunohistochemical detection of p53 and p21 proteins in canine testicular tumours

The objective of this study was to detect by immunohistochemical means nuclear accumulations of p53 and p21 proteins in testicular tumours of dogs. Intense p53 protein nuclear labelling was shown by each of seven seminomas and one intermediate collision tumour. Moderate or intense immunoreactivity was shown by three Sertoli cell tumours. All the tumours also showed p21 nuclear reactivity in parallel with the p53 reactivity. In contrast, four Leydig cell tumours showed no detectable immunoreactivity. The results suggested that high levels of p53 accumulation were associated with the expression of wild-type p53, which was able to activate the transcription of the p21 gene. In addition, weak p53- and p21-nuclear reactivities were detectable in primary spermatocytes within normal seminiferous tubules.

Testis risk and prognostic factors. The pathologist's perspective

Pathologic analysis is invaluable in defining the levels of risk for the development of a testicular tumor or for metastasis in a patient with an established testicular cancer. The identification of IGCNU in testicular biopsies defines a group of patients at high risk for subsequent invasive germ cell tumor unless they are treated by orchiectomy or radiotherapy. This method for defining the risk for the development of a testicular tumor is not effective in prepubertal patients, except for those with intersex syndromes. Pathologic analysis of testicular germ cell tumors in patients with clinical stage I disease may allow their stratification into high- and low-risk groups for occult metastases. This would provide a rational basis for recommending intervention or surveillance, respectively. The precise classification of postchemotherapy lesions permits an assessment of the patient's risk for subsequent recurrence and progressive tumor.

Distinct p53-independent apoptotic cell death signalling pathways in testicular germ cell tumour cell lines

The induction of apoptosis by diverse apoptotic stimuli was studied in a panel of 6 testicular germ cell tumour (TGCT) cell lines with defined p53 status. Although the sensitivity to a particular stimulus varied considerably among the TGCT cell lines, the differences in response were not associated with the presence of functional p53. Mutant (mt) p53-expressing NCCIT and S2 (no p53 protein) were both readily triggered into apoptosis by cisplatin and doxorubicin, while wild-type(wt)-p53-transactivation-competent 2102 EP cells failed to undergo drug-induced apoptosis. Moreover, transactivation-deficient NCCIT cells and wtp53-expressing NT2 cells were equally sensitive to cisplatin, doxorubicin, gamma radiation, and cell-permeable C2-ceramide. Our p53 data suggest that, at least in this panel of non-isogeneic TGCT cell lines, hypersensitivity to therapeutic agents is not associated with p53 status. Next, we examined the impact of p53 inactivation on apoptosis induction in isogeneic NT2 sublines expressing human papillomavirus E6 protein. Evidently, abrogation of p53 function did not affect the hypersensitivity to apoptotic stimuli. We noted that drug-sensitive S2 cells were highly resistant to radiation-induced apoptosis, indicating distinct signalling pathways for chemotherapy and irradiation. The impaired radiation-induced apoptotic pathway in S2 and 2102 EP could not be restored by addition of cell-permeable C2-ceramide, suggesting that the blockade is downstream of ceramide generation. Ligation of Fas/APO-1/CD95 by anti-Fas effectively induced apoptosis in Fas-antigen expressing S2, 2102 EP and 833 KE. The efficient Fas-mediated activation of apoptosis in drug-, radiation-, and ceramide-resistant 2102 EP cells further suggests that diverse apoptosis-inducing factors may use distinct signalling pathways. In summary, we demonstrated the presence of distinct p53-independent apoptotic pathways in TGCT cells.

The management of stage I testis cancer

For clinical stage I seminoma, conventional management consists of adjuvant RT after orchiectomy. Only 5% of patients relapse. The majority can be salvaged by chemotherapy. The overall survival of 98% is excellent. Seminoma is radiosensitive. A lower dose of RT is required than for NSGCT. Standard therapy presently is 30 Gy in 3 weeks, as suggested by the MRC study. RT is generally well tolerated. There have been recent concerns about second malignancies after 10 to 15 years. Surveillance studies have shown that 18% of patients relapse, the majority in para-aortic lymph nodes. About 15% require salvage RT and 5% salvage chemotherapy. Second relapses are seen in patients treated with RT at first relapse, and occur outside of the radiation field. The main advantage of surveillance is that 80% of patients can be spared slightly toxic overtreatment. The main disadvantage is the need for long-term follow-up, which is expensive and stressful to the patient. Good patient compliance, mandatory to an observation policy, is often difficult on a long-term basis. Seminoma is clearly responsive to chemotherapy. Adjuvant carboplatin in clinical stage I has only been evaluated in two studies. Because reliable prognostic factors have not been established, a high-risk group cannot be identified, and chemotherapy must be given to all patients. Whether or not one cycle of chemotherapy is sufficient requires further confirmation, particularly in view of the results with carboplatin as compared with cisplatin in patients with advanced NSGCT. Results of the randomized MRC trial comparing RT with carboplatin are of interest.

A rational approach to managing stage I nonseminomatous germ cell cancer

Regardless of the treatment option selected for management of low-stage germ cell cancer, ultimate survival is nearly identical. Treatment-related morbidity is very low regardless of management modality and the individual patient can expect similar physical limitations owing to therapy. The overall difference in loss of productivity between treatment programs varies by little more than 1 week. The cost of treatment is similar for all methods, although there is a definite financial advantage to surveillance, less so for selective surveillance, when compared with other forms of management. Socioeconomic factors are of importance when managing limited resources for a large population, but are of less concern to an individual, especially when the mean differences in per patient costs vary by only $5000. Because of these close similarities in efficacy, morbidity, and costs treatment decisions should be individualized. A responsible and reliable patient can be managed safely by selective surveillance. Those individuals considered to be less self-motivated to pursue intensive care should be managed by primary therapy. Without more information regarding the long-term outcomes associated with primary adjuvant chemotherapy, primary adjuvant RPLND, where experienced surgical support is available, is the preferred management for low-stage germ cell cancer in patients selected for, or electing, active treatment rather than surveillance. Active investigations examining the role of medical management in this population should be continued. Our preferred choice of initial management is to offer selective surveillance to appropriate patients and modified RPLND to the remainder.

New tumor markers of testis cancer

Potential tumor markers for testis cancer have become numerous with the new molecular techniques available. New protein markers have been evaluated, and histologic factors have shown correlations with stage of disease. Cytogenetic analysis studies have also shown associations with stage progression. Chromosomal markers, oncogenes, and tumor suppressor genes are possible candidates for tumor markers. These new potential tumor markers may become as commonplace as the established markers and may enhance diagnosis, staging, and treatment of testis cancer.

Immunohistochemical and mutational analysis of the p53 tumour suppressor gene and the bcl-2 oncogene in primary testicular germ cell tumours

The role of p53 in testicular germ cell tumours is still contradictory based on the finding of immunohistochemical overexpression at the protein level, but lack of mutations at the DNA level. In addition, p53 wild-type activity has been demonstrated in cell culture experiments. Overexpression of the proto-oncogene bcl-2 might block p53-induced apoptosis and might inhibit p53 functional activity. To clarify the apparent paradox with respect to p53 overexpression and lack of mutations, an immunohistochemical and mutational analysis of p53 and bcl-2 in TGCT was performed. Ten normal testes, 52 CIS and 151 clinical stage I nonseminomatous GCTs were included in our study. A commercially available anti-p53 polyclonal rabbit antibody and an anti-bcl-2-mouse monoclonal antibody were used to stain the 5pm sections. Staining was assessed by counting at least 500 cells from the area of the most intense staining in each tumour cell type, and this was scored semiquantitatively for intensity of staining on a 4 point scale. In addition, 30 primary GCTs were included in the mutational analysis: areas with p53 overexpression were identified and microdissected prior to DNA extraction. p53 exons 5-8 were amplified by polymerase chain reaction (PCR) followed by single strand conformation polymorphism analysis. Templates demonstrating band shifts on SSCP were subjected to direct DNA sequence analysis. None of the normal testes, 32/52 (62%) CIS, and 142/151 (94%) germ cell tumours exhibited p53 overexpression. p53 expression was significantly lower in mature teratomas (0.8 +/- 0.2) than in other germ cell tumour components (2.8 +/- 1.2, p > 0.001). PCR-SSCP did not reveal any missense mutations or deletions for the p53 gene. Bcl-2 protein expression was observed in none of the normal testes, in none of the CIS, and in 14/151 (9.3%) germ cell tumours. 13/14 germ cell tumours demonstrated bcl-2 expression only in the glandular and stromal elements of their teratomatous components whereas all other components were negative for bcl-2. Our results--p53 overexpression, lack of p53 mutations, undetectable bcl-2--are consistent with recent in vitro studies. High susceptibility of testicular cancer to drug-induced apoptosis appears to be the result of wild-type p53 and lack of bcl-2. Radiation and chemotherapeutic insensitivity of mature teratomas might be the result of bcl-2 overexpression and lack of p53 overexpression. Therefore, chemoresistance to DNA damaging agents might be reflected by the expression of p53 and bcl-2 and it might be useful to evaluate p53 and bcl-2 in primary tumours and metastatic lesions in order to identify patients early with primary or secondary chemoresistance.

P53 tumour suppressor gene and germ cell neoplasia

P53 tumour suppressor gene mutations occur in approximately 50% of common solid tumours such as breast, colon and lung. In contrast, p53 gene mutations occur infrequently (< 3%) in germ cell tumours, even though p53 protein is expressed at high levels in the vast majority of tumour samples. P53-regulated genes are not correspondingly over-expressed in germ cell tumour samples and cell lines, indicating that p53 functions poorly as a transcription factor in this tumour type. High levels of wild-type p53 may contribute, in part, to the chemosensitivity of germ cell tumours.

Differential expression of p53, c-kit, and CD34 in prepubertal and postpubertal testicular germ cell tumors

BACKGROUND

The origin of testicular germ cell tumors (TGCTs) in children is poorly understood. There are clear differences between tumors in young children and those in adolescents and adults, which may suggest that they follow different pathways of tumorigenesis.

METHODS

Tissue sections from 25 TGCTs (15 from patients age 4 years or younger and 10 from adolescents or adults) were stained immunohistochemically with anti-p53 (DO-1), CD34, and c-kit proto-oncogene protein product.

RESULTS

CD34 expression was noted only in 5 prepubertal tumors. Expression of c-kit was observed in 9 of the 15 prepubertal tumors versus 2 of the 10 postpubertal cases. The intensity of expression was equal to that of the adjacent normal tubules in the prepubertal tumors, whereas the intensity was less in the postpubertal tumors. Expression of p53 was strong in 8 of the 10 tumors in adolescents or adults, with a 40-70% positivity, whereas only 6 of 15 prepubertal tumors expressed p53, with < 10% positivity.

CONCLUSIONS

CD34 expression in tumors in the group of young children suggests a possible link to teratomas and further provides insight into the fundamental differences between this group and the adolescent/adult group. The expression of c-kit and p53 provides further evidence that c-kit/SCF signaling and p53 play potentially different roles in the initiation and progression of these tumors. Future studies will be required to clarify this issue.

PCNA and p53 in urinary bladder cancer: correlation with histological findings and prognosis

BACKGROUND

This study aimed to immunohistochemically examine the expression of proliferating cell nuclear antigens (PCNA) and p53 protein in transitional cell carcinomas (TCC) of the urinary bladder, and to investigate possible correlations of this expression with the tumor grade or stage, tumor recurrence, and prognosis of the disease.

MATERIALS AND METHODS

The immunohistochemical status of the PCNA and p53 proteins were determined on paraffin-embedded sections from 128 patients with TCC of the urinary bladder, using PC-10 and DO7 as the primary antibodies. Positive stainings were represented by scores (Labeling Index; LI, %) calculated as the percent of positive cells among all neoplastic cells counted. The findings were compared to the patients' histopathological features. Patients who underwent transurethral resection were divided into groups with "low" and "high" scores for PCNA and p53, respectively, and the tumor recurrence rate was compared among the groups. Patients who underwent total cystectomy were similarly divided into "low" and "high" score groups, and survival rates of the groups were compared.

RESULTS

PCNA expression was observed in 66 of 128 patients (51.6%), with a mean labeling index of 26.6%. Overexpression of p53 was observed in 65 of 128 patients (50.8%), with a mean labeling index of 35.3%. There were significant correlations of the PCNA and p53 indices with both histological grade and stage of the tumor. In the TUR group, there were no statistically significant differences in recurrence rate between the groups with high or low scores for either PCNA or p53. In the total cystectomy group, there was a significant correlation between survival rate and positive staining for PCNA, but not for p53. The relationship between 2 parameters, PCNA and p53 scores, was not significant (linear correlation coefficient, r = 0.67).

CONCLUSIONS

PCNA and p53 status in transitional cell carcinomas of the urinary bladder is related to the histopathological findings. We also suggest that immunohistochemical staining for PCNA provides significant clinical information which may be useful in the initial selection of therapy. However, overexpression of p53 does not appear to represent an independent prognostic marker in bladder tumors.

Alterations of the p53 tumor suppressor gene in carcinoma in situ of the testis

BACKGROUND

Carcinoma in situ (CIS) is regarded as the precursor of all histologic variants of testicular germ cell tumors except spermatocytic seminoma. For a variety of human malignancies, alterations of the p53 tumor suppressor gene have been identified as prognostic factors for a poor clinical course. Discussions of the occurrence of p53 gene alterations in testicular carcinoma have been controversial. Immunohistochemical detection of the p53 oncoprotein has been reported in four of eight CIS cell areas adjacent to mature teratoma. The majority of investigations have failed to demonstrate p53 gene alterations on the DNA level in testicular carcinoma specimens. However, the genetic analysis of testicular carcinoma is complicated by the histologic variety of tumors, resulting in a mixture of subtypes undergoing moleculargenetic analysis. In the present study, CIS cells identified in normal testicular tissue adjacent to different testicular tumors were examined for alterations of the p53 tumor suppressor gene. The authors believed that the detection of p53 alterations in CIS of the testis would not only support the idea of malignant potential in CIS but might also demonstrate the involvement of the p53 tumor suppressor gene in the development of germ cell cancers.

METHODS

CIS cells were identified in the normal testicular tissue adjacent to 18 seminomatous and nonseminomatous germ cell tumors by histopathologic criteria and the immunohistochemical staining reaction for placental-like alkaline phos phase, a highly specific marker for testicular CIS. About 20-50 CIS cells per tumor were collected by a microdissection technique and were subjected to RNA. SSCP analysis and additional DNA-sequence analysis.

RESULTS

In 12 of 18 cases (66%), RNA-SSCP analysis of the microdissected CIS cells revealed mutational band shifting at the p53 gene locus. In 7 of 18 cases (39%). the results of SSCP analysis were confirmed by DNA sequencing. DNA-sequence analysis revealed missense point mutations in the p53 gene in four cases (exon 5, codons 158, 170, and 176; exon 6, codon 213) and silent mutations in two cases (exon 5, codon 178; exon 6, codon 213). In one case, the identical missense point mutation (exon 5, codon 176) was detected in the CIS cells and also in the associated germ cell tumor. In two of six cases, different mutations were found in the CIS cells and the testicular tumor. In three cases in which DNA sequencing revealed point mutations in CIS cells, alterations of the p53 gene could not be detected in the examination of the associated tumor specimen.

CONCLUSIONS

These findings appear to support the concept that malignant biologic characteristics are present in the in situ stage of testicular germ cell tumors. This is the first report demonstrating monoclonal development of a manifested testicular carcinoma from associated CIS cells on the basis of a certain mutational event in the p53 gene sequence. The involvement of p53 gene alterations in precursor cells of testicular carcinoma appears likely.

Extent of apoptosis in relation to p53 and bcl-2 expression in germ cell tumors

This study investigates the extent of apoptosis in 53 testicular and ovarian germ cell tumors by using the in situ 3'-end DNA labeling technique on tumor sections. The tumors were also immunostained with antibodies to the p53 and bcl-2 proteins. The extent of apoptosis was highest in embryonal carcinoma (mean, 2.9%) followed by seminoma (mean, 1.1%), choriocarcinoma (mean, 0.7%) and immature teratoma (mean, 0.7%). In individual components of the mixed germ cell tumors the apoptotic index was in the same range as in the corresponding pure germ cell tumors. Mature teratomas rarely contained any apoptotic cells. Sixty-two percent of all the tumors expressed p53 protein. p53 expression was quantitatively strongest in embryonal carcinomas which also showed the highest level of apoptosis. Bcl-2 positivity could only be detected in some mesenchymal and epithelial components of the immature and mature teratomas; embryonal carcinomas, seminomas, or choriocarcinomas did not express bcl-2 at all. Our results show that the level of apoptosis in germ cell tumors associates with the histological type of the neoplastic component independent of whether it is singly present or a component of a mixed germ cell tumor. The results suggest that the quantity of p53 expression may contribute to the level of apoptosis in different tumor groups.

Treatment of clinical stage I testicular cancer and a possible role for new biological prognostic parameters

Three different treatment strategies for patients with stage I non-seminomatous testicular cancer are available that will all result in long-term survival in more than 98% of the patients: a "wait and see" strategy with follow-up and chemotherapy in cases of tumour progression, retroperitoneal lymphadenectomy, with or without application of systemic chemotherapy, in cases of retroperitoneal metastases (pathological stage II disease) or primary adjuvant chemotherapy following inguinal orchiectomy. Each treatment strategy is associated with specific side-effects. In several studies histological characteristics of the primary tumour, particularly the presence of vascular invasion and of embryonal carcinoma cells, have been demonstrated to be significant prognostic factors for the risk of occult retroperitoneal metastases in patients with stage I disease. In addition, new biological prognostic factors determined by flow cytometry, cytogenetic analysis or molecular-biological DNA or RNA analysis have been investigated, among which alterations of the p53 tumour-suppressor gene may represent a promising new prognostic factor. Although alterations of p53 gene expression seem to be associated with advanced tumour stage and may predict retroperitoneal metastatic disease, the independent role of these molecular genetic alterations needs to be prospectively studied. Currently a risk-adapted treatment strategy based on the histological criteria of vascular invasion and the presence of embryonal carcinoma can be used to stratify patients into a "high-" and "low-risk" group with respect to tumour progression. While primary-nerve-sparing retroperitoneal lymphadenectomy or adjuvant chemotherapy with two cycles of platinum, etoposide and bleomycin may be appropriate for patients with a high risk (above 40%) for tumour progression, a "wait-and-see" strategy can be used for "low-risk" (less than 15% risk of progression) patients. Molecular investigations of prognostic factors may be able to improve further the stratification of patients into these different risk categories.

Primary mediastinal and testicular seminomas: a comparison of K-ras-2 gene sequence and p53 immunoperoxidase analysis of 26 cases

Primary mediastinal seminomas (MS) are rare tumors. Histologically, they are similar to their counterpart in the gonads. The survival rate has varied from 50% to 85% in different series. However, large series of these tumors primarily in the mediastinum are lacking. At the molecular level, a few reports document K-ras mutations in up to 40% of testicular seminomas (TS), localized predominantly to codon 12. Reports on TS p53 immunohistochemistry (IHC) range from negative to overexpression approaching 90% of cases, and by sequence analysis one small series showed a 23% mutation rate. To date, no analyses have been performed for either K-ras mutations or p53 immunohistochemical expression in primary MS. The authors studied 13 cases each of primary MS and TS from archival formalin-fixed, paraffin-embedded sections in which adequate tumor sampling and clinical history, including serological studies, and histological, histochemical, and IHC staining, were performed to confirm the diagnosis. p53 immunoperoxidase staining using citrate buffer/microwave antigen retrieval was performed. Topographic genotyping was performed on 5-microns-thick tissue sections up to 17 years old, in which the neoplastic cell population was sampled. Additionally, multiple sites within a given cases were sampled to determine clonality of the tumor cell population. Polymerase chain reaction and subsequent sequence analysis of the K-ras-2 exon-1 gene was used for mutation analysis. Focal weak staining with p53 IHC was observed in 4 of 13 (31%) MS and 10 of 13 (77%) TS cases, with all remaining cases being negative (P < .05). Only one MS case (8%) showed K-ras mutation (codon 13 GGC > GAC; glycine > aspartate), which is in contrast to 2 of the TS cases (15%), showing codon 12 mutations. All the remaining cases were wild type. Therefore, primary mediastinal seminomas appear to be different in their K-ras sequence and p53 immunostain profile from TS. Codon mutation type may be useful in determining primary versus metastatic origin of a mediastinal seminoma.

A functionally inactive p53 protein in teratocarcinoma cells is activated by either DNA damage or cellular differentiation

Testicular teratocarcinomas never contain p53 gene mutations even though these tumors express high levels of nuclear p53 protein. We have characterized two murine teratocarcinoma cell lines and find no evidence that endogenous p53-regulated genes are correspondingly upregulated. Differentiation of these teratocarcinoma cells with retinoic acid results in a marked decrease in p53 protein levels but is accompanied by a marked increase in p53-mediated transcriptional activity. Together these results support the hypothesis that the p53 protein in undifferentiated teratocarcinoma cells is transcriptionally inactive and accounts for the lack of selection for p53 gene mutations in this tumor type. These teratocarcinoma cells undergo p53-mediated apoptosis in response to DNA damage, which may explain the routine cures of human testicular tumors with combination chemotherapy.

Evaluation of overexpression of p53 tumor suppressor protein in superficial and invasive transitional cell bladder cancer: comparison with DNA ploidy

OBJECTIVES

p53 tumor suppressor gene is considered to play a significant role in carcinogenesis. Mutations in the p53 are the most frequent genetic abnormalities encountered in human malignancies. Our aim was to investigate the expression of p53 oncoprotein in superficial and invasive transitional cell bladder cancer (TCC) as well as its correlation with established prognostic factors, such as histologic grade, tumor stage, DNA content, and survival.

METHODS

Forty-five patients with superficial TCC (Ta-T1) and 42 with invasive TCC (T2-T4) were included in our study. Material from transurethral biopsy was examined using an immunohistochemical method and the monoclonal antibody Pab 1801.

RESULTS

p53 tumor suppressor protein was overexpressed in 48.3% of TCC cases and more frequently in invasive than superficial TCCs (P = 0.03) and undetectable in the tumor adjacent to normal tissue. p53 positivity was related to the degree of differentiation and with the stage of the disease of invasive TCCs (P = 0.03 and P = 0.004, respectively), whereas no statistical significance was documented for superficial TCCs. Moreover, p53 overexpression demonstrated a statistical significance with DNA ploidy in superficial Ta-T1 tumors (P = 0.04) and was suggestive in invasive T2-T4 tumors (P = 0.08). There was no correlation of recurrence related to p53-positive superficial tumors (P = 0.29). Patients with p53-positive invasive TCCs showed statistically significant worse survival (P = 0.007), but in multivariate analysis, p53 positivity is not independently related to poor overall survival (P = 0.30). When we combined ploidy and p53 status, we realized that the subset of patients with aneuploidy and p53 positivity had the worst prognosis (P = 0.008).

CONCLUSIONS

The results suggest the involvement of p53 protein as a late event in bladder carcinogenesis. p53 does not seem to be a prognostic marker for recurrences of superficial tumors and is not independently related to survival. The aneuploidy of tumors correlates with the p53 positivity in bladder cancer. The combined expression of aneuploidy and p53 positivity in invasive tumors has strong association with the survival of patients.

Increased p53 protein does not correlate to p53 gene mutations in microdissected human testicular germ cell tumors

PURPOSE

To determine if primary testicular germ cell tumors that overexpress p53 tumor suppressor gene protein have p53 gene mutations.

MATERIALS AND METHODS

We examined 30 primary testicular tissues from 26 patients representing two groups. Group one consisted of eleven cases (6 nonseminomatous germ cell tumors and 5 seminomas) in which tissue samples for DNA analysis were microdissected from paraffin block regions with elevated immunohistochemical staining for p53 protein. Group two consisted of 19 testis tumor tissues which had been fresh frozen and were chosen to correspond to archival tissue specimens exhibiting elevated levels of p53 protein. The DNA was extracted from these tissues and subjected to exon specific amplification by polymerase chain reaction (PCR) and cold single-strand conformation polymorphism (Cold SSCP) analysis.

RESULTS

In these cases with elevated p53 protein, no p53 gene exon 5-8 mutations were detected except 1 seminoma with a codon 140 silent mutation (no protein alteration).

CONCLUSIONS

Testicular tumors appear to exhibit elevated levels of wild-type p53 protein, the significance of which is yet to be elucidated.

Overexpression or mutation of the p53 tumor suppressor gene does not occur in malignant ovarian germ cell tumors

BACKGROUND

The p53 tumor suppressor gene has been well studied in epithelial ovarian cancers. However, little is known of the expression of this gene in ovarian germ cell tumors. The authors attempted to investigate whether p53 alterations occurred in this group of tumors.

METHODS

Twenty-two patients with malignant ovarian germ cell tumors were included in this study. Immunohistochemical staining for p53 was performed on paraffin embedded tissue of each case. Single-strand conformation polymorphism analysis of exons 4-9 of the p53 gene was performed on 9 of the 22 tumors where genomic DNAs were obtained from the frozen tissue samples. Three tumors that revealed focal p53 positivity by immunostaining were studied further with direct DNA sequencing.

RESULTS

Overexpression of p53 was not observed in all of the 22 ovarian germ cell tumors; only 3 were found to have nuclear staining in a small fraction of the malignant cells (< 5% in 1 immature teratoma, 5-10% in 2 yolk-sac tumors). Among the nine frozen tumors subjected to single-strand conformation polymorphism analysis, none revealed p53 mutation in exons 4-9. There was no p53 mutation detected by DNA sequencing of the three tumors with focal immunoreactivity.

CONCLUSIONS

Alterations of the p53 tumor suppressor gene may not be associated with the pathogenesis of ovarian germ cell tumors. Instead, genetic changes such as inactivation of other tumor suppressor genes and/or activation of some protooncogenes need to be studied to determine the genetic mechanisms of the tumor development.

Testicular neoplasms and tumoral markers

The use of tumoral markers and especially of BHCG and AFP in the diagnosis, staging and follow-up of patients affected by testicle germinai neoplasms is now widespread. Nevertheless, controversies stili exist in each one of these fields. Especially for clinical staging, high percentages of understaging of stage I tumours are reported in literature with considerable effects on therapeutical indications and prognosis. The Authors attempt a criticai review on the use of markers for diagnosis and staging of testicular neoplasms based upon their own experience of 79 cases over a 14-year period.

Proliferating cell nuclear antigen expression to predict occult disease in clinical stage I nonseminomatous testicular germ cell tumors

We analyzed primary tumor tissue from 89 clinical stage I nonseminomatous germ cell testicular tumor patients for proliferating cell nuclear antigen expression and histological features to determine if these elements could distinguish pathological stage I (52 patients) from pathological stage II disease or patients who later had relapse (37). Using a monoclonal antibody (PC10) developed for use in archival tissue, nuclear proliferating cell nuclear antigen expression was immunohistochemically measured for the overall tumor (total proliferating cell nuclear antigen) and for each neoplastic cell type present. In addition, the primary tumor was examined for the presence of vascular invasion and determination of the percentage of tumor composed of embryonal carcinoma. Univariate logistic regression analysis revealed higher total (p = 0.0001) and higher embryonal carcinoma proliferating cell nuclear antigen expression (p = 0.0437) to be statistically significant risk factors for occult disease, correctly predicting its presence 73% and 61.5% of the time, respectively. More importantly, the presence of vascular invasion and a higher percentage embryonal carcinoma were highly significant risk factors for occult disease and were truly predictive in 80.4% and 77.2% of the cases, respectively. Multivariate logistic regression analysis revealed a combination of vascular invasion and percentage embryonal carcinoma to be the best model to predict occult disease correctly (85.9%). The addition of total or embryonal carcinoma proliferating cell nuclear antigen expression did not improve the clinical use of the model containing vascular invasion and percentage embryonal carcinoma. Although proliferating cell nuclear antigen expression mirrors the biological behavior of clinical stage I nonseminomatous germ cell testicular tumor to some degree, assessment of vascular invasion and percentage embryonal carcinoma has greater clinical use.