p53 mutation in epithelial ovarian carcinoma and borderline ovarian tumor

Role of Retinoblastoma Protein Family (Rb/p105 and Rb2/p130) Expression in the Histopathological Classification of Borderline Ovarian Tumors

Borderline ovarian tumors (BOT) are uncommon but not rare epithelial ovarian neoplasms, intermediate between benign and malignant categories. Emerging knowledge supports the notion that subtypes of borderline ovarian tumors comprise distinct biologic, pathogenetic, and molecular entities, precluding a single unifying concept for BOT. The identification of valuable markers for the diagnosis and classification of these tumors is in need. Among the molecular candidates, the Retinoblastoma (Rb) family members Rb/p105 and Rb2/p130 seem to play a pivotal role in ovarian cancer. In particular, Rb/p105, when in the unphosphorylated form, acts as a growth suppressor controlling cell cycle and tumor progression; whereas, the phosphorylated form activates gene transcription and cellular proliferation. While Rb/p105 is ubiquitously confined to the nuclei of cycling and quiescent cells, Rb2/p130 activity is also regulated by intracellular localization. According to this, Rb family members could represent a novel marker in diagnosis and classification risk for patients with BOT. In this study, we evaluated the expression and subcellular localization of proteins of the retinoblastoma (Rb) gene family in 65 ovarian borderline tumors. Statistically significant differences were found in nuclear and cytoplasmic expressions of Rb/p105 and Rb2/p130 according to different examined histotypes. In detail, the nuclear expression of Rb/p105 and Rb2/p130 was more frequently detected in serous (84.6%) than sero-mucinous (42.1%) and mucinous (50%) types. Conversely, the cytoplasmic expression of Rb2/p130 was not detected in serous tumors and frequently observed in mucinous subtypes (80%). Our findings suggest that Rb proteins do not play a key role in the tumor progression of serous borderline tumors since any cases showed cytoplasmic localization. By contrast, the observed higher cytoplasmic expression of Rb2/p130 in intestinal mucinous BOTs is indicative of Rb protein family involvement in the cancerogenesis pathway of mucinous ovarian tumors. Also, mucinous BOTs of intestinal-type, exhibiting low nuclear and high cytoplasmic levels of Rb2/p130 might potentially be considered a high-risk category of malignant evolution. Further studies on larger series are needed to clarify how BOTs could be stratified in different prognostic groups according to their Rb proteins immunohistochemical profile.

The Putative Role of TP53 Alterations and p53 Expression in Borderline Ovarian Tumors - Correlation with Clinicopathological Features and Prognosis: A Mini-Review

Borderline ovarian tumors (BOTs) represent an independent group among ovarian malignancies, being diagnosed at clinical stage earlier than invasive ovarian carcinomas (OCs) and characterized by a rather favorable outcome after careful surgical management. Data published worldwide showed a substantial discordance of p53 expression in BOTs. The purpose of this work was to present the current status of knowledge on the significance of TP53 gene and p53 protein product alterations in BOTs. In general, higher p53 expression patterns were reported for ovarian malignancies compared to BOTs. Serous, mucinous, and endometrioid BOTs differ substantially in relation to p53 immunostaining, but data concerning the relationship between the protein's immunoreactivity and other clinico-pathological variables are scarce. Finally, reports published to date support the view that TP53 alterations may not be commonly associated with the borderline phenotype of ovarian tumors but they probably occur during the development of invasive OCs. In light of these uncertainties, the impact of TP53 alterations and p53 expression on overall survival in women affected by BOTs requires further multi-institutional studies in large cohorts of patients.

Is it possible to diagnose malignancy from fluid in cystic ovarian tumors?

OBJECTIVE

p53 gene mutations are frequently identified in ovarian cancer tissue. The aim of this study was to investigate whether wild type or mutated genomic DNA can be identified in ovarian cystic fluid specimens.

STUDY DESIGN

Forty-eight Japanese patients with cystic ovarian tumors (30 benign cysts, 8 borderline malignant tumors, and 10 cancers) were investigated. Cystic fluid and tumor tissue were obtained during surgery. After DNA extraction from the cystic fluid, polymerase chain reaction (PCR) and sequence analysis for exons 4-9 of the p53 gene was performed. In two cases of mucinous cystic tumor of borderline malignancy and endometrioid adenocarcinoma, the p53 gene sequences were determined. Immunohistochemical staining for abnormal p53 gene product was also performed.

RESULTS

DNA was successfully extracted from all cystic fluid specimens. Furthermore, exons 4-9 of the p53 gene could be identified by electrophoresis from all samples. In a mucinous cystic tumor of borderline malignancy, one point mutation was identified at codon 223 in exon 6 (CCT → CTT) of the p53 gene. Aberrant p53 gene product was also observed in the tumor cells by immunohistochemical staining. Moreover, in another case of endometrial adenocarcinoma, a point mutation at codon 245 in exon 7 (GGC → AGC) was detected by the direct sequencing of the amplified Exon. Notably, the mutation was not present in the peripheral blood (PB) sample and tissue specimens from the patient.

CONCLUSION

In cystic ovarian tumors, cystic fluid may provide informative material for molecular studies since it reflects the p53 status of tumor tissue in the cyst wall. This system might help to identify ovarian malignancy without resection of the tumor tissues.

Geographical Variations in TP53 Mutational Spectrum in Ovarian Carcinomas

The TP53 gene mutational spectrum in human tumours shows variations related to tissue of origin, carcinogen exposure or molecular background. We have compared TP53 mutations in ovarian carcinomas from different geographical regions; this study was based on data extracted and verified from the IARC database (R10, 2005), and on our results from 127 carcinomas. In total 873 mutations were evaluated. Tumours from Japan and Korea had a higher frequency of exon 7 mutations (38%vs 25%, p = 0.011) and lower frequency of exon 8 mutations (11%vs 29%, p = 0.0003) than those from Western countries; they were particularly different from Norwegian tumours which showed the lowest proportion of exon 7 (19%, p = 0.001) and highest proportion of exon 8 (37%, p < 0.0001) mutations. There were also differences in the profile of TP53 hotspots. The third hotspot in tumours from Poland was amino acid (AA) 176 (8.2% of substitutions vs 1.7% in other countries, p < 0.001), while in tumours from the UK it was AA 220 (8.9%vs 2.3%, p < 0.001). Codon 273 was the only apparent hotspot in the Norwegian tumours, while it was rarely mutated in Polish and Asian tumours. In contrast to other data tumours from Norway presented with 273(HIS) codon (82% of mutations at AA 273, p = 0.002), while tumours from the UK shared the 273(CYS) codon (80%, p < 0.001). Further analysis of TP53 gene mutations in ovarian cancer by geography could provide greater insights.

Expression of pro-apoptotic (p53, p21, bax, bak and fas) and anti-apoptotic (bcl-2 and bcl-x) proteins in serous versus mucinous borderline ovarian tumours

BACKGROUND

We examined the expression of apoptosis-related proteins in serous versus mucinous borderline ovarian tumours, in comparison with benign and malignant ovarian tumours.

MATERIALS AND METHODS

Immunohistochemical expression of pro-apoptotic (p53, p21, bax, bak, fas) and anti-apoptotic proteins (bcl-2, bcl-x) was determined in 34 borderline (19 mucinous, 15 serous), 20 benign (10 mucinous, 10 serous) and 28 malignant ovarian tumours (9 mucinous, 19 serous).

RESULTS

A difference in semi-quantitative p53 expression was found between benign and borderline tumours (P = 0.01), but not between borderline and malignant tumours. Increased p21 expression was found in borderline versus benign tumours (P = 0.004). Bcl-2 expression was lower in borderline than in benign (P = 0.01) and malignant tumours (P = 0.02). No difference in bax, bak, fas or bcl-x expression was observed among the three tumour types. Higher percentage of p21 positive cells was found in serous than in mucinous borderline tumours (P < 0.001). Bcl-2 expression was higher in serous than in mucinous forms of benign (P < 0.001), borderline (P < 0.001), and malignant tumours (P < 0.003). No difference in p53, bax, bak, fas or bcl-x expression was observed between serous and mucinous borderline ovarian tumours.

CONCLUSION

Although p53 overexpression was a common feature of both mucinous and serous borderline tumours, p21 and bcl-2 overexpression appeared specific to serous tumours.

Serous and mucinous borderline (low malignant potential) tumors of the ovary

The prognosis for stage I serous borderline ovarian tumors (SBOTs) is thought to be excellent, despite rare, late recurrences. The behavior of advanced-stage SBOTs primarily depends on the invasiveness vs noninvasiveness of associated extraovarian implants. Pelvic and abdominal lymph node involvement and foci of microinvasion do not seem to adversely affect prognosis. Serous tumors with a micropapillary and/or cribriform growth pattern seem to be more frequently bilateral and exophytic and manifest at an advanced stage with a higher incidence of invasive implants than typical SBOTs. Molecular data suggest that such tumors may represent an intermediate stage in the typical SBOT-invasive low-grade serous carcinoma progression. Limited experience with endocervical (müllerian)-type mucinous borderline tumors shows a possible relation to SBOTs in clinicopathologic features and biologic behavior Intestinal-type mucinous borderline ovarian tumors (I-MBOTs) and well-differentiated mucinous carcinomas manifest at stage I in most cases; the prognosis is excellent. Mucinous tumors associated with pseudomyxoma peritonei are almost always secondary to similar tumors of the appendix or other gastrointestinal sites and should not be diagnosed as high-stage I-MBOTs. Rare primary ovarian mucinous tumors associated with pseudomyxoma peritonei are those arising in mature cystic teratomas. Advanced-stage ovarian mucinous carcinomas typically show frank, infiltrative-type invasion; the prognosis is poor.

TP53 and ovarian cancer

Ovarian cancer represents the fourth most frequent type of cancer among females and is the leading cause of death from gynecological cancer in the western world. This review describes gene alterations in ovarian cancer. Specific emphasis is placed on genetic alterations and the prevalence of TP53 (p53) gene alterations in the distinct biological ovarian tumors (benign, borderline, and malignant) and histological subtypes (serous, mucinous, endometrioid, clear cell), as well as in BRCA1-associated hereditary ovarian cancer. Although multi-modality treatment regimens, including cytoreductive surgery and cisplatin-containing combination chemotherapy, have usefully prolonged survival, the overall cure rate of the disease has not changed dramatically. Ovarian cancer is difficult to eradicate completely by surgery and many patients have only a partial response to postoperative chemotherapy and/or many will develop chemotherapy resistance. All these important factors contribute to the poor prognosis of ovarian cancer patients. In this review, the putative prognostic or predictive value of TP53 in ovarian cancer is addressed.

A review of p53 expression and mutation in human benign, low malignant potential, and invasive epithelial ovarian tumors

BACKGROUND

In the current study, the authors present pooled data from studies that investigated p53 protein expression and/or mutation in human epithelial ovarian tumors.

METHODS

The English literature in the MEDLINE, PubMed, and Ingenta databases was searched to the end of the year 2000 to identify relevant studies. Data were pooled across eligible studies, and the prevalence of p53 expression and mutation among benign, low malignant potential (LMP), and invasive tumors was determined. Prevalence estimates by tumor histology, International Federation of Gynecology and Obstetrics (FIGO) stage, and grade also were calculated.

RESULTS

The pooled prevalence estimate for p53 overexpression among epithelial ovarian carcinomas was 51% (95% confidence intervals [95% CI], 50-53%) compared with 17% (95% CI, 15-20%) among LMP tumors and 7% (95% CI, 5-10%) among benign tumors. p53 mutation prevalence estimates were 45% (95% CI, 42-47%), 5% (95% CI, 2-9%), and 1% (95% CI, 0-5%), respectively, for invasive, LMP, and benign tumors. The prevalence of these p53 abnormalities was found to be associated positively with increasing tumor grade and stage. Differences based on histologic subtype also were found.

CONCLUSIONS

Although these pooled estimates might appear to offer support for various hypotheses regarding the role of p53 in ovarian carcinoma, the limitations inherent in these data hamper the interpretation of the significance of any of the findings. Future studies will require innovative methods to address the limitations of many previous investigations and more comprehensive investigation into defective tumor suppression mechanisms.

Clinical management potential tumours of low malignancy

Approximately 3000 American women are diagnosed with borderline ovarian tumours annually. Common signs and symptoms include abdominal/pelvic pain and a palpable adnexal mass. Pelvic sonography may be helpful, although not specific, in the diagnosis. Serum CA 125 is abnormal in only about 50% of patients. Primary surgery is the principal treatment; it consists of resection of the primary tumour(s) (frequently in the form of fertility-sparing surgery), frozen-section analysis and consideration of comprehensive surgical staging. The role of surgical staging remains unclear; further research is necessary. For patients with stage I disease, surgery alone is the standard. For patients with stage II-IV disease (with non-invasive or invasive peritoneal implants), the role of post-operative therapy remains unclear. Approximately 20-30% of the latter will relapse, frequently after several years. Most so-called recurrences are low-grade carcinomas. Potential predictive or prognostic factors include age, FIGO stage, residual disease and the micropapillary pattern. After fertility-sparing surgery, most patients retain normal reproductive function.

Topoisomerase II alpha: prognostic predictor and cell cycle marker in surface epithelial neoplasms of the ovary and peritoneum

Immunohistochemistry for Topoisomerase II alpha (TopoIIa), a nuclear protein important for the separation of chromosomes and deoxyribonucleic acid replication, provides insight into the molecular events in the cell cycle and the response to chemotherapeutic agents, which target TopoIIa. We test the hypothesis that the percentage of TopoIIa immunoreactive nuclei (TopoIIaI) aids in the treatment and prognostic evaluation of ovarian and primary peritoneal surface epithelial neoplasms (SENs) and correlates with established cell cycle control markers: p53, p21WAF1/CIP1 (p21), and Ki67. Paraffin sections from a retrospective surgical series of 108 SENs were immunostained with anti-TopoIIa, anti-p53, anti-p21, and anti-Ki67. The TopoIIaI, the Ki67 proliferation index (Ki67PI), and the immunoreactivity score for p53 and p21 (IMS: S1, S2, S3 < 10%, 10 to 50%, > 50% of strong staining cells, respectively) were evaluated manually. TopoIIaI and Ki67PI ranged from 5 to 84% and 4 to 88% (mean/median: 31/30 and 44/46%), respectively, and were correlated (coefficient 0.62, p < 10(-11)). IMS of 108 SENs was as follows: p53 50% + (2S1, 52S3) and p21 66% + (38S1, 12S2, 21S3). The TopoIIaI associated directly with p53 (p < 10(-5) and inversely with p21 (p < 0.005) IMS. TopoIIaI correlated with SEN architectural/nuclear grade (p < 10(-5)/10(-7)), but not histologic type. Sixty-seven patients had disease at last follow-up, 55 were dead from disease at 2 to 67 months (mean/median 24/21), and 14 were alive with disease at 31 to 230 months (mean/median 73/59). Forty-one patients were disease free at 5 to 228 months (mean/median 75/54). TopoIIaI correlated with presence of disease (p < 0.01) and poor survival (p < 1 x 10(-9), even when only 93 invasive SEN cases are considered (p < 0.005). TopoIIaI correlates with poor prognosis and other cell cycle control markers. The patients in this retrospective series of SEN were treated primarily with platinum-based chemotherapy. These data may suggest further prospective studies in which patients with SENs exhibiting high TopoIIaI are treated with chemotherapy targeted against TopoIIa (e.g., etoposide). In this retrospective series, high SEN TopoIIaI predicted poor survival when treated with platinum-based chemotherapy, which does not target TopoIIa.

Ovarian serous borderline tumors: a critical review of the literature with emphasis on prognostic indicators

BACKGROUND

The behavior of ovarian serous borderline tumors (SBTs) and significance of various prognostic factors are unclear and difficult to evaluate because of inconsistencies and confusion in the literature. Recent studies have suggested that the morphological features of the primary tumor (presence or absence of micropapillary features) and the peritoneal "implants" (presence or absence of invasive features) can reliably subclassify SBTs into benign and malignant types. The aim of the current review was to test two hypotheses. First, that the alleged malignant behavior of SBTs is poorly documented, and second, that the morphological features of the primary ovarian tumors and the associated peritoneal implants are sufficient to separate SBTs into benign and malignant types, thereby obviating the need for the category.

METHODS

245 studies reporting approximately 18,000 patients with borderline ovarian tumors were reviewed. After excluding series that lacked clinical follow-up or were not analyzable for other reasons, there remained 97 reports that included 4,129 patients. In addition to recurrences and survival, we evaluated the type of peritoneal implants, microinvasion, lymph node involvement, late recurrences, and progression to carcinoma, as these features have served as the underpinning of the concept of "borderline malignancy" or "low malignant potential."

RESULTS

Among 4,129 patients with SBTs reviewed, the recurrence rate after a mean follow-up of 6.7 years was 0.27% per year for stage I tumors, the disease-free survival was 98.2%, and the overall disease-specific survival rate was 99.5%. For patients with advanced-stage tumors, the recurrence rate was 2.4% per year. However, the majority (69%) of reported recurrences were not pathologically documented, and only 26 cases (8.4% of all recurrences) were documented to have recurred from an adequately sampled ovarian tumor. The most reliable prognostic indicator for advanced stage tumors was the type of peritoneal implant. After 7.4 years of follow-up, the survival of patients with noninvasive peritoneal inplants was 95.3%, as compared with 66% for invasive implants (P < .0001). Microinvasion in the primary ovarian tumor was associated with a 100% survival rate at 6.7 years, and lymph node involvement was associated with a 98% survival rate at 6.5 years. The few reported cases of stage IV disease, progression to invasive carcinoma, and very late (>20 years) recurrences were poorly documented. The survival for all stages among approximately 373 patients in 6 prospective randomized trials followed for a mean of 6.7 years was 100%.

CONCLUSION

Surgical pathological stage and subclassification of extraovarian disease into invasive and noninvasive implants are the most important prognostic indicators for SBTs. Survival for stage I tumors is virtually 100%. Survival for advanced stage tumors with noninvasive implants is 95.3%, whereas survival for tumors with invasive implants is 66%. Invasive implants behave as carcinomas and are most likely metastatic. The precise nature of so-called noninvasive implants is not clear, but they behave in a benign fashion. The presence of a micropapillary architecture in the primary ovarian tumor is a strong predictor of invasive implants. These data support the recommendation that ovarian tumors with a micropapillary architecture be designated "micropapillary serous carcinomas," and those lacking these features, "atypical proliferative serous tumors."

Immunohistochemical markers of cell cycle control applied to ovarian and primary peritoneal surface epithelial neoplasms: p21(WAF1/CIP1) predicts survival and good response to platinin-based chemotherapy

Immunohistochemistry for p53, p21(WAF1/CIP1), and Ki-67 provides insight into the molecular events controlling the cell cycle. We tested the hypothesis that these cell cycle markers will aid in the clinical evaluation of ovarian and primary peritoneal surface epithelial neoplasms (SENs). Paraffin sections from a retrospective surgical series of 117 SENs were immunostained with anti-p53 (clone DO7, Novacastra Laboratories, UK), anti-p21(WAF1/CIP1) (clone EA10, Oncogene Science, Cambridge, MA), and anti-Ki-67 (clone MIB-1, Immunotech, Westbrook, ME). The Ki-67 proliferation index (Ki-67PI) and immunoreactivity were evaluated. One hundred seventeen SENs reacted as follows: p53 50%+ and p21(WAF1/CIP1) 65%+. Ki-67PI ranged from 4% to 88% (mean/median = 44/46%). p53 reactivity associated with transitional cell histology, decreased p21(WAF1/CIP1) staining, increased Ki-67PI, architectural/nuclear grade, and stage (P < .05, 1 x 10(-7), .01, .05/.0001, .001,). p21(WAF1/CIP1) staining was associated with endometrioid/clear cell histology, decreased Ki-67PI, architectural/nuclear grade, and stage (P < 05/.05, .05, .01/1 x 10(-8), 1 x 10(-5)). Ki-67PI associated with increased architectural/nuclear grade but not mucinous histology (P < 1 x 10(-5)/1 x 10(-6), .01). Sixty-seven patients had disease at last follow-up; 53 were dead of disease at 0 to 67 months (mean/median, 21/18), and 14 were alive with disease at 12 to 224 months (mean/median, 56/40). Fifty patients were disease free at 5 to 214 months (mean/median, 59/41). Predictors of survival include decreased Ki-67PI, stage, architectural/nuclear grade (P < 1 x 10(-6), 1 x 10(-10), 1 x 10(-10)/.005) and p21(WAF1/CIP1) IMS (multivariate P < 1 x 10(-6)). p21(WAF1/CIP1), a potent inhibitor of cyclin-dependent kinases necessary for cell cycle progression, functions as a key checkpoint in cell cycle control. Immunoreactivity for p21(WAF1/CIP1) provides prognostic information independent of other histological and clinical predictors, p53 IMS, and Ki-67PI in this series of 117 PTs with SENs. Our preliminary data suggest an interrelationship between p21(WAF1/CIP1) expression and an effective clinical response to platinin-based chemotherapy, both associated with apoptosis. Further investigation seems warranted.

Comparison of mutations of Ki-RAS and p53 immunoreactivity in borderline and malignant epithelial ovarian tumors

Ovarian tumors of low malignant potential ("borderline tumors") have been proposed variably to represent a distinctive type of malignancy, precursors of frank ovarian malignancy, or a nonmalignant process. We analyzed 81 malignant and 39 borderline ovarian tumors for p53 immunoreactivity and alterations in codon 12 of Ki-RAS in order to correlate these alterations with tumor and cell type. Diffuse p53 immunoreactivity was significantly more prevalent among malignant (36 of 81, 44%) than among borderline (3 of 39, 8%) tumors and was particularly prevalent among serous invasive carcinomas (16 of 26, 62%). Conversely, mutations in codon 12 of Ki-RAS were significantly more prevalent in borderline (16 of 39, 41%) than in malignant (9 of 81, 11%) ovarian tumors and were most prevalent among mucinous tumors. This preliminary molecular analysis suggests that serous borderline tumors have some molecular features usually associated with malignancy but are unlikely to represent a precursor of invasive serous carcinoma. In contrast, mucinous borderline tumors may represent a precursor or variant of mucinous carcinoma of the ovary.

Hormonal etiology of epithelial ovarian cancer, with a hypothesis concerning the role of androgens and progesterone

In the United States, ovarian cancer is the fourth most frequent cause of cancer death among women, following lung, breast, and colorectal cancers. Each year, approximately 26,000 women are diagnosed with ovarian cancer and 14,000 die of it. Germline mutations in BRCA1, BRCA2, or other genes have been implicated in a small fraction of cases. However, it has been suggested that, for the great majority of patients, the risk of epithelial ovarian cancer could be related to "incessant ovulation" (i.e., to the chronically repeated formation of stromal epithelial clefts and inclusion cysts following ovulation) or to some type of hormonal stimulation of ovarian epithelial cells, either on the surface of the ovary or within ovarian inclusion cysts, possibly mediated through excessive gonadotropin secretion. From the evidence to date, the relative importance of these two hypotheses--incessant ovulation and gonadotropin stimulation--cannot be distinguished. While either or both may play a role in the development of ovarian cancer, it appears that an additional major factor must also be involved. The purpose of this review is to evaluate evidence for and against the incessant ovulation and gonadotropin hypotheses, as well as to consider the possibility that risk of ovarian cancer may be increased by factors associated with excess androgenic stimulation of ovarian epithelial cells and may be decreased by factors related to greater progesterone stimulation. Many features of the evidence bearing on the pathophysiology of ovarian cancer appear to support a connection with androgens and progesterone.

Borderline tumors of the ovary: a clinico-pathologic and immunohistochemical study of 54 cases

OBJECTIVE

To study EGF-R, HER-2/neu (p185), p53, Mib-1 (Ki-67), Bax, Bcl-2, ras expression and ploidy in borderline tumors of the ovary by assessing their frequency, and relationship to histologic type, tumor recurrence and survival.

METHODS

Fifty-four patients with borderline tumors were followed 3-140 months (median: 38 months). Paraffin-embedded sections were stained using monoclonal antibodies against EGF-R, HER-2/neu (p185), p53, Mib-1 (Ki-67), Bax, Bcl-2, and ras. The immunohistochemical findings were correlated to histologic subtype, tumor recurrence, and survival.

RESULTS

Positivity for EGF-R was found in 24% (13/54), in 22% (12/54) p185 was positive, 9% (5/54) of tumors were p53-positive, Mib-1 (Ki-67)-positivity was demonstrable in 46% (25/54). Expression of Bax, Bcl-2, and ras was found in 37% (20/54), 28% (15/54) and in 7% (4/54) of the cases, respectively.

CONCLUSION

The data demonstrate expression of EGF-R, p185/HER-2/neu, p53, Mib-1 (Ki-67), Bax, Bcl-2, and ras in a subgroup of patients with ovarian borderline tumors. Further studies to evaluate their prognostic value are warranted.

Correlation of TP53 mutations and p53 expression in ovarian tumors

To characterize the involvement of the TP53 tumor suppressor gene in ovarian cancer, mutation analysis of exons 2-11 of TP53 and immunodetection of its protein product, p53, were done in 48 ovarian tumors. Normally, p53 is not immunodetectable. Missense TP53 mutations have been reported to result in p53 accumulation and detection, but mutations generating premature stop codons have not. Mutations were identified in 19 of 41 malignant tumors but not in 5 benign tumors and 2 tumors of low malignant potential. Fifteen of the 19 tumors with mutations also stained positively by immunohistochemistry or Western blot or both. They included 11 missense mutations, 1 in-frame duplication (474ins6), and 3 frameshift mutations generating premature stop codons. The three tumors with frameshifts also had a wild-type TP53 allele and displayed normal size but not truncated p53 by Western blot. This indicates that these tumors express wild-type p53. The significance of TP53 mutations in the development of the three tumors is questionable unless there is a mechanism for inactivating wild-type p53. Nine of the 19 mutations found here, including the 3 frameshifts, were previously not reported in ovarian cancer. Thirteen of the 19 mutations were single nucleotide substitutions with 6 transitions and 7 transversions. The ratio of transversions to transitions (1.2) was different from literature reports (0.5) (P < 0.01). Thus, the spectrum of TP53 mutations in our study differed from other ovarian tumor reports. This difference may be due to population-based differences in the molecular epidemiology of TP53 mutations.

Identification of allelic losses in benign, borderline, and invasive epithelial ovarian tumors and correlation with clinical outcome

BACKGROUND

The somatogenetic alterations that lead to the development of benign adenomas, borderline tumors, and invasive ovarian carcinomas are not well understood. This study investigated allelic losses in these three types of ovarian tumors.

METHODS

Twelve genetic regions on chromosomes 2q, 5q, 6p, 6q, 9p, 11q, 17p, 17q, 18q, and 22q were analyzed by polymerase chain reaction for loss of heterozygosity (LOH). The study was performed on formalin fixed, paraffin embedded tissue samples from 72 invasive ovarian carcinomas, 35 ovarian tumors of borderline malignancy, and 25 benign ovarian adenomas.

RESULTS

LOH was found in only 8% of the analyzed adenomas (at 2q21 and 17p13) and 11% of the borderline tumors (at 2q21, 5q21, 6p21, 17p13, and 17q21). Allelic losses were noted for 77.7% of all of the invasive carcinomas analyzed. The frequency of LOH was 56% at a locus near 17p13 (TP53) and 40.5% at 17q21 (BRCA1). LOH was observed in 30.4% of informative cases at 5q21 and in 21.4% at chromosome 18q21. The chromosomal regions 2q21-22 and 9p21 had deletions at frequencies of 32.4% and 25%, respectively. International Federation of Gynecology and Obstetrics stage and the presence of LOH correlated significantly with survival but were not independent predictors of survival. Serous subtypes of invasive carcinoma were significantly more prone to deletions than nonserous tumors.

CONCLUSIONS

The results of this study suggest that LOH occurs only occasionally in adenomas and borderline tumors, whereas it is frequently observed in invasive ovarian carcinomas. Therefore, other genetic events seem to be involved in early ovarian tumor development. However, the presence of multiple allelic losses is an indicator of higher stages of invasive carcinoma.

p53 and HER-2/neu overexpression in ovarian borderline tumors

OBJECTIVE

To study p53 and HER-2/neu expression in borderline ovarian tumors (BLOT) by assessing their frequency, coexpression, and relationship to histologic type, FIGO stage, tumor recurrence, and survival.

METHODS

Forty-two patients with confirmed BLOT (25 serous, 13 mucinous, and 4 seromucinous) were followed for 1.5 to 14 years (mean, 6.3). Thirty (71%) patients had FIGO stage I and 12 (29%) had FIGO stage III disease. Paraffin-embedded sections from the 42 BLOT, 5 normal ovaries, and 10 benign ovarian cystadenomas were stained using monoclonal antibodies against human p53 (DAKO-p53, DAKO, Denmark) and HER-2/neu (C-erB-2, Triton, Parkway, CA). Positive staining was semiquantitated depending on the number of positively stained tumor cells. p53 and HER-2/neu overexpressions were correlated to each other, to histologic subtype, stage, tumor recurrence, and survival.

RESULTS

None of the patients had tumor recurrence. The 5- and 10-year disease-free survival was 100%. None of the normal ovaries or ovarian cystadenomas demonstrated overexpression of p53 or HER-2/neu. Ten (24%) BLOT demonstrated overexpression of p53 and 9 (21%) demonstrated overexpression of HER-2/neu. HER-2/neu overexpression was significantly greater in stage III than in stage I tumors (P = 0.0157). Seromucinous BLOT demonstrated significantly greater p53 overexpression compared with other histologic subtypes (P = 0.030). Coexpression of p53 and HER-2/neu occurred in 4 patients (9.5%). There was no significant correlation between the overexpression of p53 and HER-2/neu (P = 0.180) and no significant relationship between p53 and HER-2/neu overexpression and the presence of microinvasion, ability to perform optimal cytoreductive surgery, tumor recurrence, or survival.

CONCLUSIONS

p53 and HER-2/neu overexpression occurred in about 20-25% of BLOT overall and more commonly in seromucinous and advanced stage tumors. Coexpression occurred in 9.5% of the cases with no significant correlation between the expression of p53 and HER-2/neu.