Alteration of the p53 tumor suppressor gene occurs independently of K-ras activation and more frequently in serous adenocarcinomas than in other common epithelial tumors of the human ovary

Refined criteria for p53 expression in ovarian mucinous tumours are highly concordant with TP53 mutation status, but p53 expression/TP53 status lack prognostic significance

In gynecological neoplasms, immunohistochemical (IHC) expression of p53 is generally an accurate predictor of TP53 mutation status if correctly interpreted by the pathologist. However, the literature concerning cut-offs, frequency and prognostic significance of p53 staining in ovarian mucinous tumours is limited and heterogeneous. We performed an analysis of 123 primary ovarian mucinous tumours including mucinous borderline tumours (MBT), mucinous carcinomas (MC), and tumours with equivocal features between MBT and MC. We assessed p53 expression for the three recognised patterns of aberrant staining in ovarian carcinoma [overexpression ('all'), null and cytoplasmic] but using a recently suggested cut-off for aberrant overexpression in ovarian mucinous tumours (strong nuclear p53 staining in ≥12 consecutive tumour cells) and correlated the results with next generation sequencing (NGS) in all qualitatively sufficient cases (92/123). Aberrant p53 expression was present in 25/75 (33.3%) MBT, 23/33 (69.7%) MC (75% of MC with expansile invasion and 61.5% with infiltrative invasion), and 10/15 (66.7%) tumours equivocal between MBT and MC. Regarding the 92 tumours with paired IHC and mutation results, 86 showed concordant results and six cases were discordant. Three discordant MBT cases showed aberrant expression but were TP53 wild-type on sequencing. Three cases had normal p53 expression but contained a TP53 mutation. Overall, IHC predicted the TP53 mutation status with high sensitivity (94.1%) and specificity (92.7%). The accuracy of IHC was 93.5% with a positive predictive value of 94.1% and a negative predictive value of 92.7%. When comparing MC cases with wild-type TP53 versus those with TP53 mutation, there were no significant differences concerning disease-free survival, local recurrence-free survival, or metastases-free survival (p>0.05). In the MBT subgroup, there were no events for survival analyses. In conclusion, using an independent large sample set of ovarian mucinous tumours, the results of our study confirm that the suggested refined cut-off of strong nuclear p53 staining in ≥12 consecutive tumour cells reflect high accuracy, sensitivity and specificity for an underlying TP53 mutation but the TP53 mutation status has no prognostic significance in either MC or MBT.

Chronic Exposure to Nitric Oxide Induces P53 Mutations and Malignant-like Features in Human Breast Epithelial Cells

The small endogenous signaling molecule nitric oxide (NO) has been linked with chronic inflammation and cancer. The effects of NO are both concentration and temporally dependent; under some conditions, NO protects against damage caused by reactive oxygen species and activates P53 signaling. During chronic inflammation, NO causes DNA damage and inhibits repair proteins. To extend our understanding of the roles of NO during carcinogenesis, we investigated the possible effects of chronic NO exposure on MCF10A breast epithelial cells, as defined by changes in cellular morphology, chromosome/genomic stability, RNA, and protein expression, and altered cell phenotypes. Human MCF10A cells were maintained in varying doses of the NO donor DETANO for three weeks. Distinct patterns of genomic modifications in TP53 and KRAS target genes were detected in NO-treated cells when compared to background mutations. In addition, quantitative real-time PCR demonstrated an increase in the expression of cancer stem cell (CSC) marker CD44 after prolonged exposure to 300 μM DETANO. While similar changes in cell morphology were found in cells exposed to 300-500 μM DETANO, cells cultured in 100 μM DETANO exhibited enhanced motility. In addition, 100 μM NO-treated cells proliferated in serum-free media and selected clonal populations and pooled cells formed colonies in soft agar that were clustered and disorganized. These findings show that chronic exposure to NO generates altered breast epithelial cell phenotypes with malignant characteristics.

Primary Mucinous Tumors of the Ovary: An Interobserver Reproducibility and Detailed Molecular Study Reveals Significant Overlap Between Diagnostic Categories

Primary ovarian mucinous tumors represent a heterogeneous group of neoplasms, and their diagnosis may be challenging. We analyzed 124 primary ovarian mucinous tumors originally diagnosed as mucinous borderline tumors (MBTs) or mucinous carcinomas (MCs), with an emphasis on interobserver diagnostic agreement and the potential for diagnostic support by molecular profiling using a next-generation sequencing targeted panel of 727 DNA and 147 RNA genes. Fourteen experienced pathologists independently assigned a diagnosis from preset options, based on a review of a single digitized slide from each tumor. After excluding 1 outlier participant, there was a moderate agreement in diagnosing the 124 cases when divided into 3 categories (κ = 0.524, for mucinous cystadenoma vs MBT vs MC). A perfect agreement for the distinction between mucinous cystadenoma/MBT as a combined category and MC was found in only 36.3% of the cases. Differentiating between MBTs and MCs with expansile invasion was particularly problematic. After a reclassification of the tumors into near-consensus diagnostic categories on the basis of the initial participant results, a comparison of molecular findings between the MBT and MC groups did not show major and unequivocal differences between MBTs and MCs or between MCs with expansile vs infiltrative pattern of invasion. In contrast, HER2 overexpression or amplification was found only in 5.3% of MBTs and in 35.3% of all MCs and in 45% of MCs with expansile invasion. Overall, HER2 alterations, including mutations, were found in 42.2% of MCs. KRAS mutations were found in 65.5% and PIK3CA mutations in 6% of MCs. In summary, although the diagnostic criteria are well-described, diagnostic agreement among our large group of experienced gynecologic pathologists was only moderate. Diagnostic categories showed a molecular overlap. Nonetheless, molecular profiling may prove to be therapeutically beneficial in advanced-stage, recurrent, or metastatic MCs.

Somatic mutations in breast and serous ovarian cancer young patients: a systematic review and meta-analysis

OBJECTIVE

our aim was to evaluate whether somatic mutations in five genes were associated with an early age at presentation of breast cancer (BC) or serous ovarian cancer (SOC).

METHODS

COSMIC database was searched for the five most frequent somatic mutations in BC and SOC. A systematic review of PubMed was performed. Young age for BC and SOC patients was set at ≤ 35 and ≤ 40 years, respectively. Age groups were also classified in < 30 years and every 10 years thereafter.

RESULTS

twenty six (1,980 patients, 111 younger) and 16 studies (598, 41 younger), were analyzed for BC and SOC, respectively. In BC, PIK3CA wild type tumor was associated with early onset, not confirmed in binary regression with estrogen receptor (ER) status. In HER2-negative tumors, there was increased frequency of PIK3CA somatic mutation in older age groups; in ER-positive tumors, there was a trend towards an increased frequency of PIK3CA somatic mutation in older age groups. TP53 somatic mutation was described in 20% of tumors from both younger and older patients; PTEN, CDH1 and GATA3 somatic mutation was investigated only in 16 patients and PTEN mutation was detected in one of them. In SOC, TP53 somatic mutation was rather common, detected in more than 50% of tumors, however, more frequently in older patients.

CONCLUSION

frequency of somatic mutations in specific genes was not associated with early-onset breast cancer. Although very common in patients with serous ovarian cancer diagnosed at all ages, TP53 mutation was more frequently detected in older women.

Targeted sequencing reveals clonal genetic changes in the progression of early lung neoplasms and paired circulating DNA

Lungs resected for adenocarcinomas often harbour minute discrete foci of cytologically atypical pneumocyte proliferations designated as atypical adenomatous hyperplasia (AAH). Evidence suggests that AAH represents an initial step in the progression to adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and fully invasive adenocarcinoma. Despite efforts to identify predictive markers of malignant transformation, alterations driving this progression are poorly understood. Here we perform targeted next-generation sequencing on multifocal AAHs and different zones of histologic progression within AISs and MIAs. Multiregion sequencing demonstrated different genetic drivers within the same tumour and reveal that clonal expansion is an early event of tumorigenesis. We find that KRAS, TP53 and EGFR mutations are indicators of malignant transition. Utilizing droplet digital PCR, we find alterations associated with early neoplasms in paired circulating DNA. This study provides insight into the heterogeneity of clonal events in the progression of early lung neoplasia and demonstrates that these events can be detected even before neoplasms have invaded and acquired malignant potential.

Atypical adenomatous hyperplasia is thought to be a precursor lesion for lung adenocarcinoma. Here, using targeted deep sequencing, the authors demonstrate that hyperplastic lesions contain somatic mutations associated with malignant disease and that these can be detected in circulating tumour cells.

Potential markers for detection and monitoring of ovarian cancer

This paper reviews current screening techniques as well as novel biomarkers and their potential role in early detection of ovarian cancer. Ovarian cancer is one of the most common reproductive cancers and has the highest mortality rate amongst gynecologic cancers. Because most ovarian cancer diagnoses occur in the late stages of the disease, five-year survival rates fall below 20%. To improve survival rates and to lower mortality rates for ovarian cancer, improved detection at early stages of the disease is needed. Current screening approaches include tumor markers, ultrasound, or a combination. Efforts are underway to discover new biomarkers of ovarian cancer in order to surmount the obstacles in early-stage diagnosis. Among serum protein markers, HE4 and mesothelin can augment CA125 detection providing higher sensitivity and specificity due to the presence of these proteins in early-stage ovarian cancer. Detection testing that includes methylation of the MCJ gene and increased expression of vascular endothelial growth factor is correlated to poor prognosis and may predict patient survival outcome. Detection testing of biomarkers with long-term stability and combination panels of markers, will likely lead to effective screening strategies with high specificity and sensitivity for early detection of ovarian cancer.

Pathogenesis of ovarian clear cell adenofibroma, atypical proliferative (borderline) tumor, and carcinoma: clinicopathologic features of tumors with endometriosis or adenofibromatous components support two related pathways of tumor development

The clinicopathologic features of 472 ovarian epithelial clear cell neoplasms (4 adenofibromas [AFs], 41 atypical proliferative [borderline] tumors [APTs], and 427 carcinomas [CAs]) were studied in order to elucidate the morphologic steps involved in the pathogenesis of these tumors and determine whether clear cell CA is a type I or type II tumor in the dualistic model of ovarian carcinogenesis. Thirty-three percent of the CAs had an adenofibromatous background [CA(AF+)], and 67% did not [CA(AF-)]. Endometriosis was found in all types of tumors, but tumors arising in endometriotic cysts were more frequent with CA(AF-)s (p<0.0001). The subset of women with CA(AF-)s with endometriosis were younger (p<0.0001), their tumors were more frequently cystic (p<0.0001), they more commonly had a mixed carcinoma component of non-clear cell type (p=0.006), and they were more frequently oxyphilic (p=0.015) compared with CA(AF+)s. The architecture of the former tumors was more commonly papillary compared to tubulocystic in the latter (p=0.0006). Atypical endometriosis was more common in CA(AF-)s than in AFs, APTs, and CC(AF+)s [p=0.004]. The subset of CA(AF-)s without endometriosis presented more frequently in advanced stage (>I) and were higher grade compared to CA(AF+)s or CA(AF-) with endometriosis (p-values, <0.0001 to 0.0071). All AFs and APTs were stage I compared to 79% of CA(AF+)s. An increase in mean tumor size correlated with each respective tumor category from AF (6.8 cm) to CA(AF+) [12.9 cm]. Notable nuclear atypia was absent in all AFs but was focally present in 27% of APTs and in the adenofibromatous background of 24% of the CA(AF+)s. An increase in the proportion of carcinoma in the CA(AF+)s correlated with an increase in grade and advanced stage. In summary, ovarian clear cell CA appears to develop along two pathways, both of which are related to endometriosis. We speculate that, in one, epithelial atypia arises in an endometriotic cyst and then evolves into clear cell CA, and, in the other, non-cystic endometriosis induces a fibromatous reaction resulting in the formation of AF, which then develops into APT and subsequently a clear cell CA. The absence of endometriosis or adenofibromatous components in CC(AF-)s may be due to overgrowth and obliteration by the invasive carcinoma. Finally, the findings in this study support the view that both types of clear cell CA [CC(AF+) and CC(AF-)] are more closely related to type I tumors.

Stanniocalcin 1 and ovarian tumorigenesis

BACKGROUND

Stanniocalcin 1 (STC1) is a secreted glycoprotein hormone. High expression of STC1 has been associated with several cancers including ovarian cancer, but its role in the development of ovarian cancer is not clear.

METHODS

We used five human ovarian epithelial cancer cell lines (OVCA420, OVCA432, OVCA433, SKOV3, and HEY), immortalized human ovarian surface epithelial cells (T29 and T80), ovarian cancer tissues from 342 patients, serum from 73 ovarian cancer patients and from58 control subjects, and 116 mice, with six or eight per group. Protein expression was assessed. Cells overexpressing STC1 protein were generated by ectopic expression of human STC1 cDNA. STC1 expression was silenced by using small interfering RNA against STC1. Cell proliferation, migration, colony formation, and apoptosis were assessed. Xenograft tumor growth in mice was studied. Neutralizing anti-STC1 antibody was used to inhibit STC1 function. All statistical tests were two-sided.

RESULTS

STC1 protein expression was higher in all human ovarian cancer cell lines examined than in immortalized human ovarian epithelial cell lines, higher in ovarian cancer tissue than in normal ovarian tissue (P < .001), and higher in serum from ovarian cancer patients than from control subjects (P = .021). Ovarian cancer cells with STC1 overexpression, compared with corresponding control cells, had increased cell proliferation, migration, and colony formation in cell culture and increased growth of xenograft tumors in mice. These activities in normal or malignant ovarian cells with STC1 overexpression, compared with control cells, were also accompanied by increased expression of cell cycle regulatory proteins and antiapoptotic proteins but decreased cleavage of several caspases. Within 24 hours of treatment, apoptosis in cultures of HEY ovarian cancer cells treated with neutralizing anti-STC1 monoclonal antibody was higher (17.3% apoptotic cells) than that in cultures treated with mouse IgG control cells (4.4%) (12.9% difference, 95% confidence interval = 11.6% to 14.2%).

CONCLUSIONS

STC1 protein may be involved in ovarian tumorigenesis.

Tubal and ovarian pathways to pelvic epithelial cancer: a pathological perspective

Prolongation of ovarian epithelial cancer survival depends on early detection or improved responses to chemotherapy. Gains in either have been modest at best. Understanding the diverse pathogenesis of this disease is critical to early intervention or prevention. This review addresses six important variables, including (i) cell of origin, (ii) site of origin, (iii) initial genotoxic events, (iv) risks imposed by hereditary and other promoting conditions, (v) subsequent factors that promote different patterns of metastatic spread, and (vi) prospects for intervention. This review proposes two distinct pathways to pelvic epithelial cancer. The first initiates in ovarian surface epithelium (OSE), Mullerian inclusions or endometriosis in the ovary. The second arises from the endosalpinx and encompasses a subset of serous carcinomas. The serous carcinogenic sequence in the distal fallopian tube is described and contrasted with lower grade serous tumors based on tumour location, earliest genetic change and ability (or lack of) to undergo terminal (ciliated) differentiation. Ultimately, a clear understanding of tumour origin and the mechanism(s) leading to the earliest phases of the serous and endometrioid carcinogenic sequences may hold the greatest promise for designing prevention strategies and/or developing new therapies.

Role of p53 and Rb in ovarian cancer

Ovarian cancer remains a major health concern worldwide, primarily in postmenopausal women. Among the most common genetic alterations in human sporadic epithelial ovarian cancer (EOC) are p53 mutations, defective retinoblastoma (RB) pathway (p16^INK4a/RB) and activation of oncogenes such as c-myc, K-ras and Akt. Although these alterations are frequently associated with poor clinical prognosis, their specific contributions to EOC formation remain unclear. In order to gain a better understanding of the roles of these proteins in vivo, a number of mouse models have been generated, largely based upon inducing specific genetic lesions in the ovarian surface epithelium from which the majority of carcinomas are thought to arise in humans. Here, we review the role of tumor suppressor p53 and the Rb pathway in EOC with particular attention to association of p53 to high grade serous carcinomas as opposed to low grade and benign tumors. We also provide an overview of the utility and application of genetically engineered mouse models, in particular towards rational drug design and development of improved imaging techniques in ovarian cancer.

Loss of DNA mismatch repair protein hMSH6 in ovarian cancer is histotype-specific

Microsatellite instability (MSI) due to defects in DNA mismatch repair genes may be involved in the development of a subset of human ovarian carcinomas. The role of one such gene, hMSH6, in ovarian cancer is not well documented. We investigated the expression of hMSH6 protein in different histotypes of ovarian carcinoma and the associations between loss of hMSH6 protein and tumor grade, disease stage, familial history of cancer and patient survival. We stained an ovarian carcinoma tissue microarray consisting of formalin-fixed, paraffin-embedded tissue samples from 322 patients with an anti-hMSH6 antibody and scored the results semiquantitatively as negative or positive. Twelve cases were excluded owing to loss of cores during staining. Absence of hMSH6 protein was noted in 20 of 230 serous carcinomas (8.7%), in 7 of 16 clear cell carcinomas (43.7%), in 4 of 34 endometrioid carcinomas (11.7%), in 1 of 14 malignant mixed Müllerian tumors, 2 of 6 mucinous carcinomas, 0 of 2 transitional cell carcinomas and in 0 of 8 undifferentiated carcinomas. Loss of hMSH6 protein was not associated with survival, patient age, tumor grade, or disease stage but was associated with clear cell, mucinous and endometrioid carcinoma histology (P<0.007). These findings indicate that loss of hMSH6 expression in ovarian carcinoma is more common in certain histologic subtypes, particularly in clear cell, endometrioid, and mucinous carcinoma, suggesting that loss of hMSH6 function may participate in the pathogenesis of these subtypes of cancer. Loss of hMSH6 expression did not predict survival and was not associated with disease stage, tumor grade, patient age or family history of cancer.

High resolution melting for mutation scanning of TP53 exons 5-8

BACKGROUND

p53 is commonly inactivated by mutations in the DNA-binding domain in a wide range of cancers. As mutant p53 often influences response to therapy, effective and rapid methods to scan for mutations in TP53 are likely to be of clinical value. We therefore evaluated the use of high resolution melting (HRM) as a rapid mutation scanning tool for TP53 in tumour samples.

METHODS

We designed PCR amplicons for HRM mutation scanning of TP53 exons 5 to 8 and tested them with DNA from cell lines hemizygous or homozygous for known mutations. We assessed the sensitivity of each PCR amplicon using dilutions of cell line DNA in normal wild-type DNA. We then performed a blinded assessment on ovarian tumour DNA samples that had been previously sequenced for mutations in TP53 to assess the sensitivity and positive predictive value of the HRM technique. We also performed HRM analysis on breast tumour DNA samples with unknown TP53 mutation status.

RESULTS

One cell line mutation was not readily observed when exon 5 was amplified. As exon 5 contained multiple melting domains, we divided the exon into two amplicons for further screening. Sequence changes were also introduced into some of the primers to improve the melting characteristics of the amplicon. Aberrant HRM curves indicative of TP53 mutations were observed for each of the samples in the ovarian tumour DNA panel. Comparison of the HRM results with the sequencing results revealed that each mutation was detected by HRM in the correct exon. For the breast tumour panel, we detected seven aberrant melt profiles by HRM and subsequent sequencing confirmed the presence of these and no other mutations in the predicted exons.

CONCLUSION

HRM is an effective technique for simple and rapid scanning of TP53 mutations that can markedly reduce the amount of sequencing required in mutational studies of TP53.

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.

Prognostic significance of p53 mutation in suboptimally resected advanced ovarian carcinoma treated with the combination chemotherapy of paclitaxel and carboplatin

The prognostic significance of p53 mutation, microsattelite instability and DNA mismatch protein hMLH1 expression in suboptimally resected advanced ovarian carcinoma treated with the combination chemotherapy of paclitaxel and carboplatin was evaluated. The overall combination chemotherapy response rate and the complete remission rate were significantly higher among patients with mutant p53 tumors than those with wild-type p53 tumors (35/42 (83%) vs. 32/58 (55%); P=0.003 and 18/42 (43%) vs. 16/58 (28%); P=0.03, respectively). This tendency apparently existed in non-serous carcinoma, but not in serous carcinoma. Univariate analysis showed that the risk of death due to disease and risk of progression was significantly lower among patients with p53 mutation (P=0.0357 and 0.0281, respectively). However, the presence of microsattelite instability or loss of hMLH1 expression was not associated with either the clinical response or prognosis. Determining p53 mutational status can be useful in predicting therapeutic response to drugs in ovarian carcinoma, especially in non-serous tumors.

Microvessel quantification in benign and malignant ovarian tumors

Microvessel density (MVD) in 92 paraffin sections of ovarian samples of different histologic subtypes was correlated with microvessel counts from 58 corresponding frozen sections. Anti-human von Willebrand factor antibody was used as an endothelial marker. MVD was performed in neovascular hotspots using a Quantimet 500+ Image Analyzer. The highest vessel density (HVD) and average vessel density (AVD) of three fields at the x 200 and x 400 magnification were recorded. There was a strong correlation between the HVD and AVD at the x 200 and x 400 magnifications when comparing fixed with frozen sections (correlation coefficients at x 200 for the HVD was 0.37, P = 0.005 and AVD was 0.30, P = 0.02; correlation coefficients at x 400 for the HVD was 0.38, P = 0.003 and AVD was 0.37, P = 0.004). In the fixed tissue, the HVD and AVD at both these magnifications were significantly greater in the group containing functional cysts; this was also the case for the frozen sections. These findings are consistent with the development of a microcirculation necessary for the growth and maturation of such cysts, and this appears to be greater than that in tumors. The good correlation between MVD in fixed and frozen sections suggests that such observations represent a true reflection of ovarian angiogenesis in both physiologic and pathologic states.

Histologic Type, Organ of Origin, and Wnt Pathway Status: Effect on Gene Expression in Ovarian and Uterine Carcinomas

PURPOSE

Ovarian and uterine carcinomas manifest several differentiation patterns resembling those seen in nonneoplastic epithelia of the gynecologic tract. Specific oncogene and tumor suppressor gene defects have been associated with particular differentiation patterns in carcinomas arising in either the uterus or ovary. For instance, ovarian and uterine carcinomas with endometrioid differentiation frequently show beta-catenin mutations. Whereas type of differentiation is considered in the treatment of uterine carcinomas, it does not presently contribute to decisions about treatment of ovarian carcinomas. A widely accepted view is that the accumulation of specific gene defects and gene expression changes underlies phenotypic traits of cancers, including their response to treatment.

EXPERIMENTAL DESIGN

Using oligonucleotide microarrays to assess gene expression in 103 primary ovarian and uterine carcinomas, we sought to address whether organ of origin or type of differentiation (histotype; endometrioid versus serous) had a more substantial effect on gene expression patterns.

RESULTS

We found that effects on gene expression due to organ of origin and histotype are similar in magnitude and are parallel in that organ effects are similar in the two histotypes and histotype effects are similar in the two organs. In addition, ovarian and uterine endometrioid adenocarcinomas with beta-catenin defects show a common gene expression signature largely distinct from that seen in tumors lacking such defects.

CONCLUSIONS

Our results illustrate how organ of origin, type of differentiation, and specific molecular defects all contribute to gene expression in the most common types of ovarian and uterine cancers. The findings also imply gene expression data will be of value for stratifying ovarian cancer patients for new treatment approaches.

A genetically defined model for human ovarian cancer

Disruptions of the p53, retinoblastoma (Rb), and RAS signaling pathways and activation of human telomerase reverse transcriptase (hTERT) are common in human ovarian cancer; however, their precise role in ovarian cancer development is not clear. We thus introduced the catalytic subunit of hTERT, the SV40 early genomic region, and the oncogenic alleles of human HRAS or KRAS into human ovarian surface epithelial cells and examined the phenotype and gene expression profile of those cells. Disruption of p53 and Rb pathway by SV40 early genomic region and hTERT immortalized but did not transform the cells. Introduction of HRAS(V12) or KRAS(V12) into the immortalized cells, however, allowed them to form s.c. tumors after injection into immunocompromised mice. Peritoneal injection of the transformed cells produced undifferentiated carcinoma or malignant mixed Mullerian tumor and developed ascites; the tumor cells are focally positive for CA125 and mesothelin. Gene expression profile analysis of transformed cells revealed elevated expression of several cytokines, including interleukin (IL)-1beta, IL-6, and IL-8, that are up-regulated by the nuclear factor-kappaB pathway, which is known to contribute to the tumor growth of naturally ovarian cancer cells. Incubation with antibodies to IL-1beta or IL-8 led to apoptosis in the ras-transformed cells and ovarian cancer cells but not in immortalized cells that had not been transformed. Thus, the transformed human ovarian surface epithelial cells recapitulated many features of natural ovarian cancer including a subtype of ovarian cancer histology, formation of ascites, CA125 expression, and nuclear factor-kappaB-mediated cytokine activation. These cells provide a novel model system to study human ovarian cancer.

Role of cell-cycle regulatory proteins in gynecological cancer

Human malignant tumors are characterized by abnormal proliferation resulting from alterations in cell-cycle regulatory mechanisms. This review summarizes the current knowledge about these aberrations in malignant tumors of the ovary, endometrium, cervix uteri, and vulva. The data indicate that analysis of single cell cycle stimulating or inhibiting proteins partly produces unexpected, apparently paradoxical results, and cell-cycle regulatory pathways should be regarded as a whole in order to identify the molecular mechanisms leading to abnormal tumor cell proliferation. For the papillomavirus (HPV)- associated cervical and vulvar carcinomas, the manifold effects of the viral oncogenes E6 and E7 on cell-cycle control are described.

Role of KRAS and BRAF gene mutations in mucinous ovarian carcinoma

OBJECTIVES

The goals of this study were to perform a comprehensive assessment of the prevalence of KRAS oncogene mutations in invasive epithelial ovarian carcinomas of various histologic subtypes, and for any subgroup(s) in which KRAS mutation was found to be common, to address the hypothesis that those tumors without KRAS mutation had sustained alternative activation of this signaling pathway through mutation of the BRAF oncogene.

METHODS

A total of 104 primary, invasive epithelial ovarian carcinomas from a 10-year period at this institution were selected for study based on histologic classification. The histologic cell type was serous in 21 cases, endometrioid in 30 cases, clear cell in 31 cases, and mucinous in 22 cases. Additional clinical and pathological information was abstracted from patient records, and pathology review was performed for all cases. Direct sequence analysis of exon 2 of the KRAS gene, containing codon 12, was performed using DNA isolated from all tumor specimens. Sequence analyses of exons 11 and 15 of the BRAF gene were performed for the 22 cases of mucinous ovarian carcinoma.

RESULTS

Activating KRAS mutations were more common in mucinous tumors (50%) than in all other histologic types combined (5%; P < 10(-7)). Mutation of KRAS was more common in stage I tumors than in advanced stage tumors (P = 0.0004). Of the 11 mucinous tumors with KRAS mutations, 6 were of Mullerian (endocervical) type and 5 were of gastrointestinal type. No mucinous tumor was found to harbor a BRAF mutation.

CONCLUSIONS

These data indicate that KRAS oncogene mutations exist in several histologic types of invasive epithelial ovarian carcinoma, especially stage I tumors, but are common only in tumors of mucinous histology. Mutations are equally prevalent in mucinous ovarian cancers of Müllerian and gastrointestinal types. In contrast to other solid tumor types frequently affected by KRAS mutation, mucinous ovarian cancers without a KRAS mutation have not sustained alternative activation of this signaling pathway through mutation of the BRAF oncogene.

Genetic analysis of benign ovarian tumors

Ovarian cancer represents a major cause of cancer death among women and yet remarkably little is known about its etiology. The paradigm established by the colorectal carcinogenesis model would suggest that ovarian cancers are likely to arise through malignant transformation of benign ovarian tumors. However, molecular genetic data that could answer this important question is lacking. In our study, we analyzed 80 benign ovarian tumors for TP53 and K-ras mutations and for LOH on chromosomes 6, 7, 9, 11 and 17 using 56 microsatellite markers. Twenty-five percent (5/20) of non-epithelial tumors and 73% (44/60) of epithelial tumors exhibited LOH on at least 1 chromosome arm. A particularly high frequency of LOH was detected among the epithelial tumors on chromosome arms 6q (17%), 7p (17%), 7q (27%) and 11p (18%), which are also regions of frequent LOH among ovarian carcinomas. No K-ras mutations were detected in any tumor but somatic TP53 mutations were detected in 2/34 (6%) serous and 1/26 (4%) mucinous epithelial tumors. In contrast to most previous studies our data is derived from a relatively large number of microdissected tumors and is likely to represent a more accurate picture of the frequency of alterations in these tumors. We conclude that LOH is common in benign ovarian tumors, suggesting that inactivation of tumor suppressor genes are pivotal in their development. The high frequency of alterations is consistent with their being precursors to malignant disease but does not unequivocally prove this continuum. It does however provide a framework for future analysis of the molecular genetic etiology of ovarian tumorigenesis.

Genetic alterations in ovarian carcinoma: with specific reference to histological subtypes

Multiple genetic changes including activation of proto-oncogenes and inactivation of tumor suppressor gene are involved in the development of human ovarian cancer. We describe such genetic alterations with specific reference to histological subtypes. K-ras activation is specific for mucinous tumors including adenomas. Borderline tumors and carcinomas, suggesting that K-ras activation may be associated with the mucinous differentiation rather than malignant transformation. Inactivation of p53 is detected in 30-40% of ovarian carcinoma. Mutations are more frequently observed in serous carcinomas, but not found in adenomas or rarely found in borderline tumors, suggesting that p53 mutations may be directly involved in malignant transformation. TGFbeta-2 mutations are found in 50% of endometrioid carcinoma, but rarely in other type. Loss of DCC mRNA expression is found in 50% of serous carcinomas but less frequently in other type. Loss of DCC expression is rare in borderline tumors and adenomas, suggesting that inactivation of DCC may be directly involved in malignant transformation. Microsatellite instability (MI) is found in 17% of ovarian carcinomas, and is frequently found in endometrioid carcinomas. Although inactivation of p16 by point mutation or deletion is rare, p16 inactivation by loss of expression is relatively common.

K-ras alterations in Danish ovarian tumour patients. From the Danish "Malova" Ovarian Cancer study

OBJECTIVE

Activation of ras oncogenes has been demonstrated in ovarian tumours. All the reported studies are based on a relatively small number of patients and the results therefore remain a subject of debate.

METHODS

In this study, we analyzed the presence of mutations at codons 12 and 13 of the K-ras gene in 165 Danish women with ovarian tumours, including 138 invasive ovarian cancers and 27 borderline ovarian tumours, using a restriction fragment length polymorphism-polymerase chain reaction technique and evaluated whether such alterations were associated with the clinicopathological parameters of the patients and survival.

RESULTS

K-ras codon 12 gene mutations were found in 8.7% of ovarian cancer patients and in 14.8% of the borderline ovarian tumour patients. A K-ras codon 13 gene mutation was found in 1.5% of ovarian cancer patients. K-ras mutations were found with a significantly higher frequency in mucinous tumours compared to serous tumours (P = 0.011).

CONCLUSIONS

Mutation frequency was correlated with the histological type of tumour, but not with stage, radicality of operation, and age. Furthermore, no significant difference in survival was demonstrated between patients with or without K-ras mutation, neither in the univariate nor in the multivariate survival analyses.

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.

Establishment and characterization of a cell-line originated from human mucinous cystadenocarcinoma of the ovary

We recently established a cell line (designated 371M) derived from an ovarian mucinous cystadenocarcinoma. The tumor cells were obtained from the ascitic fluid of a 54-year-old Japanese woman while she was undergoing surgery. Adjuvant chemotherapy (combined paclitaxel and carboplatin) was administered, but was ineffective, and she died about 4 months after surgery. The 371M cells continuously propagated in vitro over a period of about 50 months and, to date, have undergone over 100 passages. They proliferated in a monolayered sheet with doubling times of 84 h and 37 h in the 10th and 34th passages, respectively. When transplanted into nude mice, the tumor histopathologically resembled the structure of the original tumor. The 371M cells secreted high levels of CA125 and CA19-9 into the culture medium. There were several abnormal chromosomes in all karyotypes selected at random. Sensitivity of 371M cells to a variety of anti-cancer drugs was examined by in vitro MTT assay, and the results suggested that CPT-11 and CDDP were more effective against 371M cells than other anti-cancer agents.

Possible associations among expression of p14(ARF), p16(INK4a), p21(WAF1/CIP1), p27(KIP1), and p53 accumulation and the balance of apoptosis and cell proliferation in ovarian carcinomas

BACKGROUND

Although there are several reports of changes in expression of cyclin-dependent kinase inhibitors in ovarian carcinomas, little is known about their associations with tissue kinetics in the various histologic subtypes.

METHODS

In total, 131 carcinomas were immunohistochemically investigated for expression of p14(ARF) (p14), p16(INK4a) (p16), p21(WAF1/Cip1) (p21), and p27(Kip1) (p27). The results also were compared with data for apoptosis, cell proliferation, p53 status, and survival. Western blot and mRNA analyses were conducted on 35 malignant ovarian tumor samples.

RESULTS

Significant differences in tissue kinetics determined by ratios of apoptotic relative to mitotic indices were observed among histologic subtypes of ovarian carcinomas, showing a shift toward predominance of cell proliferation in serous and cell deletion in clear cell types. The expression of p16, p21, p27, and p53 was associated closely with changes in cell proliferation rather than apoptosis and survival, dependent on the subtype. Positivity for p16 and p21 in the Western blot assay was significantly related to the results for immunohistochemical but not mRNA analyses, indicating possible posttranscriptional regulation of these genes.

CONCLUSIONS

The findings indicate that the several cyclin-dependent kinase inhibitors investigated are expressed differently among histologic subtypes of ovarian carcinomas, associated with differences in tissue kinetics and the balance of apoptosis and cell proliferation.

Impaired FHIT expression characterizes serous ovarian carcinoma

The FHIT (fragile histidine triad) gene on chromosome 3p14.2 is a candidate tumour suppressor gene. To define the role of the FHIT gene in the development of ovarian cancer, we have examined 33 ovarian carcinomas, 2 borderline tumours and 10 benign adenomas for the presence of FHIT gene alterations. FHIT transcripts were analysed by RT-PCR and sequencing. Aberrant FHIT transcripts were observed in 5/33 carcinomas (15%) and in 1 of 2 borderline tumours. Loss of normal FHIT transcript was observed in 5/33 carcinomas (15%) but not in 2 borderline tumours or 10 benign adenomas. Allelic losses at D3S1300 and D3S4103, both located within intron 5 of FHIT, were detected in 5/24 (21%) and 5/25 (20%) informative ovarian carcinomas, respectively. Expression of Fhit protein was analysed by immunohistochemistry in 44 carcinomas, 19 borderline tumours and 16 benign adenomas. Loss or significantly reduced expression of Fhit protein was observed in 6/44 (14%) ovarian carcinomas but not in any of 19 borderline tumours or 16 benign adenomas. The impaired Fhit protein expression was significantly correlated with the loss of normal FHIT transcription. Most notably, loss of normal FHIT transcript and impaired expression of Fhit protein occurred only in serous adenocarcinomas of grade 2 and 3 (5/15; 33% and 6/19; 32%, respectively). The present data suggest that inactivation of the FHIT gene by loss of expression is one of the important molecular events associated with the genesis of ovarian carcinoma, especially of high-grade serous carcinoma.

Mutation of K-RAS protooncogene and loss of heterozygosity on 6q27 in serous and mucinous ovarian carcinomas

The genetic etiology of serous and mucinous ovarian carcinomas was investigated in 76 affected patients, focusing on the possible loss of heterozygosity (LOH) involving chromosome band 6q27 and K-RAS mutations at codon 12. The incidence of LOH in 6q27 (6q27 LOH) was 41% in 64 informative cases; 53% (20/38) and 23% (6/26) in cases of serous ovarian carcinoma and in those of mucinous ovarian carcinoma, respectively, indicating that the incidence of 6q27 LOH was significantly higher in cases of serous ovarian carcinoma (P < 0.05). The incidence of K-RAS mutations at codon 12 was 23% (15/64); 5% (2/38) and 50% (13/26) in cases of serous ovarian carcinoma and in those of mucinous ovarian carcinoma, respectively, indicating that the incidence of the K-RAS mutations was significantly higher in cases of mucinous ovarian carcinoma (P < 0.0001). Thus, K-RAS mutations at codon 12 and 6q27 LOH were suggested to be involved in the development and/or progression of mucinous ovarian carcinoma and serous ovarian carcinoma, respectively.

Incidence of P53 and K-ras alterations in ovarian mucinous and serous tumors

Clarification of the pathogenic relationships existing among ovarian cystadenomas, tumors of low malignant potential (LMP) and various adenocarcinoma types, a series of 29 mucinous and 19 serous ovarian tumors including adenomas, LMP tumors and adenocarcinomas were examined. P53 protein was detected by the streptavidin-biotin method and point mutation of K-ras codon 12 was detected by polymerase chain reaction-restriction fragment length polymorphism analysis. P53 overexpression was observed more frequently in serous adenocarcinomas (5/8, 63%) than in mucinous adenocarcinomas (2/9, 22%) and was correlated with the malignant potential of serous tumors. Furthermore, the proportion of P53-positive cells was significantly higher in serous adenocarcinomas than in mucinous adenocarcinomas. P53 overexpression may therefore be closely related to the early events of carcinogenesis in serous tumors. Although mutation of the K-ras oncogene appears to be an important event in the early tumorigenesis of mucinous tumors, mutation of the K-ras oncogene in serous tumors may be dependent on morphology. Different complex pathways of oncogene and/or tumor suppressor gene abnormalities may be involved in the development of mucinous and serous adenocarcinomas.

DNA replication errors are frequent in mucinous cystadenocarcinoma of the ovary

To elucidate the genetic etiology of sporadic epithelial ovarian carcinoma, we examined replication errors (RER) in its two common types, serous cystadenocarcinoma (SAC) and mucinous cystadenocarcinoma (MAC). The subjects were 63 patients with sporadic epithelial ovarian carcinoma, consisting of 34 patients with SAC and 29 with MAC. The specimens were formalin-fixed and paraffin-embedded tissues from the ovary. The presence of RER was examined by polymerase chain reaction using 5 microsatellite markers. Of the 61 informative patients with ovarian carcinoma, RERs were observed at greater than or equal to 1 locus in 15 patients (25%). Four of the 32 SAC patients (13%) were RER-positive, and 11 of the 29 MAC patients (38%) were RER-positive, the incidence being significantly higher in the latter than in the former (P < 0.05). The incidence of RER was not related to the patients' age, stage, histologic grade, or prognosis. The MAC patients in stages I and II showed a relatively high incidence of RER (30%). These results suggest that RER are involved in the development and/or progression of MAC among sporadic epithelial ovarian carcinoma in its relatively early stage.

Somatic mutations of the PPP2R1B candidate tumor suppressor gene at chromosome 11q23 are infrequent in ovarian carcinomas

Previous studies have demonstrated frequent allelic losses of distal chromosome 11q in ovarian carcinomas. The tumor suppressor gene(s) presumably targeted by these losses have not yet been identified. PPP2R1B is a candidate tumor suppressor gene at 11q23 that has recently been shown to be mutated in a subset of colorectal and lung cancers. We evaluated 5 ovarian carcinoma cell lines and 27 primary ovarian carcinomas for allelic losses of 11q23 and for mutations in the open reading frame of PPP2R1B. We also evaluated the primary tumors for allelic losses at 17p13, another chromosomal region frequently affected by losses of heterozygosity (LOH) in ovarian cancers. 11q23 and 17p13 allelic losses were identified in 25% and 74% of the carcinomas, respectively. No mutations within PPP2R1B coding sequences were found. These findings indicate that mutations of the PPP2R1B gene are infrequent in ovarian cancer and that deletions affecting the distal portion of chromosome 11q in ovarian cancer likely target inactivation of other genes.

Mutation analysis of BRCA1, TP53, and KRAS2 in ovarian and related pelvic tumors

Cancer may be viewed as a genetic disease resulting from critical mutations that disrupt normal cell growth. To characterize the involvement of the BRCA1 and TP53 tumor suppressor genes and of the KRAS2 protooncogene in gynecologic cancer, mutation analysis of these genes was conducted in pelvic tumors of 85 patients that included 49 epithelial ovarian carcinoma cases. The 85 pelvic tumors contained 5 tumors with BRCA1 mutations, 33 with TP53 mutations, and 1 with a KRAS2 mutation. Each of the BRCA1 and KRAS2 mutations, and 25 of the TP53 mutations, were in ovarian carcinomas. Four of the BRCA1 mutations were germline and 1 was somatic. The 4 patients with germline BRCA1 mutations had an early age of disease onset (33-48 years) relative to the mean age of onset (58 years) of all 49 ovarian carcinoma patients, and 3 of these 4 patients had a family history of ovarian or breast cancer. None of the 4 tumors with germline BRCA1 mutations had a KRAS2 mutation or a TP53 mutation, despite a 51% frequency of TP53 mutations in the 49 ovarian carcinomas. Three of the 4 tumors with germline BRCA1 mutations retained a wild-type BRCA1 allele. The tumor with the somatic BRCA1 mutation contained a TP53 mutation and had no evidence for wild-type BRCA1 and TP53 alleles. These data suggest that both BRCA1 and TP53 were inactivated in 1 of 49 ovarian carcinomas. Moreover, mutational inactivation of both BRCA1 and TP53 did not occur in 4 tumors with a germline BRCA1 mutation. It has been proposed that tumorigenesis in cells with a heterozygous BRCA1 mutation requires inactivation of the wild-type BRCA1 and TP53 alleles, which results in genomic instability and acquisition of mutations in protooncogenes. Clearly, mutational inactivation of TP53 and the wild-type BRCA1 allele in ovarian tumors with a heterozygous, germline BRCA1 mutation is not an absolute requirement for tumor formation. It is possible that these alleles may be inactivated by nonmutational mechanisms or that other tumor formation pathways exist.

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.

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.

Loss of heterozygosity on chromosome 6q27 and p53 mutations in epithelial ovarian cancer

Loss of heterozygosity (LOH) in chromosome region 6q27 and p53 mutations were studied to attempt to clarify the genetic etiology of ovarian cancer, with particular reference to clear cell adenocarcinoma (CCC), which has a poor prognosis. 6q27 LOH in 70 epithelial ovarian cancer patients was examined using four restriction fragment length polymorphism markers located at 6q27; p53 mutations in tumor DNA were detected using polymerase chain reaction single-strand conformation polymorphism and sequencing. 6q27 LOH was confirmed in 26 of 48 informative cases (54.2%). No differences in the incidence of 6q27 LOH were seen by histologic type; 6q27 LOH was observed in 45% (5/11) of CCCs. p53 mutations were detected in 19 of the 48 tumors (39.6%), but in only one (9%) CCC. These results suggest that a putative tumor suppressor gene involved in the onset of epithelial ovarian cancer is located at 6q27. This gene is one of the keys to clarifying the genetic etiology of epithelial ovarian cancer and particularly CCC, given the low incidence of p53 mutations in this tumor type.

Increased microvessel density in mucinous compared with malignant serous and benign tumours of the ovary

Microvessel density of benign, borderline and malignant ovarian tumours was studied immunohistochemically using antibodies to the endothelial cell markers CD31, CD34 and factor VIII-related antigen. Microvessel density was compared in tumours of different histological subtype, stage and patient outcome. CD31-immunostained sections were examined and regions of high and average microvessel density were selected. Identical regions were located on CD34- and factor VIII-related antigen-immunostained serial sections and microvessel counts obtained and converted to vessels mm(-2). CD31 and CD34 immunostaining revealed increased microvessel density in both the high and average vessel density regions of mucinous (222.4 +/- 24.8; 79.9 +/- 8.5) compared with serous (105.4 +/- 20.7; 33.3 +/- 6.8) and benign (84.4 +/- 19.4; 20.4 +/- 4.4) tumours (P < 0.001). CD31 and CD34 immunostaining also revealed increased microvessel density in early-stage mucinous tumours (234.6 +/- 28.2; 87.8 +/- 9.2) compared with that observed in both early- (72.8 +/- 15; 12.9 +/- 2.4) and late- (115.6 +/- 26.5; 29.8 +/- 8.5) stage serous tumours (P < 0.001). No differences in microvessel density in samples from patients with differing outcomes were observed (P > 0.05). Reduced factor VIII-related antigen compared with CD31 and CD34 immunostaining was observed in both borderline and malignant mucinous and serous tumours (P < 0.02) but not in benign tumours (P > 0.05). Our results contradict the putative association between increased microvessel density and poor prognosis and suggest that the level and control of angiogenesis may differ between ovarian tumour types.

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.

Alteration of p16 and p15 genes in common epithelial ovarian tumors

We have examined the roles of 2 putative tumor-suppressor genes, the p16 and p15 inhibitor-of-cyclin-dependent-kinase genes, in the most commonly occurring epithelial tumors of the human ovary. Expression of p16 mRNA, examined by RT-PCR, was significantly reduced in 15 of the 48 tumors. Aberrant expression of p16 protein, detected by immunohistochemistry, occurred in 22 of 60 tumors, more frequently in low-grade tumors, and had significant correlation with low p16 mRNA expression. Hypermethylation of a site within the 5'-CpG island of the p16 gene was significantly associated with loss of p16 mRNA and protein expression. Homozygous gene deletion, evaluated by differential PCR analysis, was found in 2 tumors for the p16 gene and in 1 tumor for the p15 gene among 70 ovarian tumors examined. PCR-SSCP analysis detected point mutations in p16 in 4 tumors and in p15 in 1 tumor. One was a 38-bp deletion, from codons 48 to 60, in a mucinous tumor of low malignant potential; another was a non-sense mutation in codon 60 in a mucinous adenocarcinoma. The remaining 2 mutations were mis-sense mutations, one in codon 58 and the other in codon 60, in 2 endometrioid adenocarcinomas. We conclude that inactivation of p16, by loss of p16 mRNA and protein expression as a consequence of hypermethylation of the 5'-CpG island, rather than by gene deletion or point mutation, may play an important role in the genesis of human ovarian epithelial tumors.

Analysis of loss of heterozygosity and KRAS2 mutations in ovarian neoplasms: clinicopathological correlations

The molecular events that give rise to ovarian epithelial neoplasms are not well understood. In particular, it is not known whether adenocarcinomas arise from benign or low malignant potential (LMP) precursors. We have examined a large series of benign (25) and LMP (31) ovarian tumors for loss of heterozygosity (LOH) at multiple loci on 17 chromosomes. LOH was observed in benign tumors on chromosomes 6 (14%) and 9 (5%) and on the X chromosome (33%) only. LOH on these chromosomes was also detected in a small number of LMP neoplasms, suggesting that these may derive sometimes from benign precursors. In addition, we examined LOH in 93 adenocarcinomas. Analysis of associations between LOH events showed that LOH on chromosomes 5 and 17 (P = 0.0002) and on chromosomes 17 and 18 (P = 0.00007) were associated significantly with each other, which suggests that these may represent cooperative, progressive events. No novel significant associations were identified between LOH events and stage, grade, or histology, which would indicate the existence of genetic heterogeneity in ovarian neoplasms. KRAS2 mutations were detected more often in LMP neoplasms than in malignant tumors (P = 0.004) and were detected more often in Stage I/II malignant tumors than in Stage III/IV malignant tumors (P = 0.033), suggesting that LMP tumors with KRAS2 mutations are unlikely to progress to frank malignancy. Univariate (but not multivariate) survival analysis showed that LOH of chromosomes 11 (P = 0.039) and 17 (P = 0.04) was associated with a significantly worse prognosis. Replication of these novel findings is necessary, and the identification, isolation, and characterization of the critical genes affected by LOH will determine their importance in the pathogenesis of ovarian malignancies.

Inactivation of p16/CDKN2 and p15/MTS2 genes in different histological types and clinical stages of primary ovarian tumors

To define the involvement of p16/CDKN2 and p15/MTS2 inactivation in ovarian tumorigenesis and the association of these inactivation events with histological types and clinical stages of ovarian tumors, we analyzed homozygous deletion and somatic mutation of p16/CDKN2 and p15/MTS2 genes, as well as hypermethylation of the 5'-CpG island of the p16/CDKN2 gene, in 49 primary ovarian tumors and 6 ovarian carcinoma cell lines. We found homozygous deletions of p16/CDKN2 and p15/MTS2 in 6 (12%) and 5 (10%) primary tumors, respectively. Somatic mutation of p16/CDKN2 was found in only 1 primary tumor, but mutation of p15/MTS2 was not detected in any sample. None of the 28 primary tumors or 6 cell lines was hypermethylated at the 5'-CpG island of p16/CDKN2. The incidence of inactivation of p16/CDKN2 in primary tumors was significantly higher in the advanced stages (7 of 29) than in the early stages (0 of 14). Seven of 9 alterations in p16/CDKN2 and p15/MTS2 were observed in serous (3 of 12), endometrioid (3 of 9) and clear-cell (1 of 4) carcinomas. However, only normal sequences of these genes were detected in mucinous carcinomas. Loss of heterozygosity (LOH) at the IFNA locus was detected in 1 of 19 (5%) tumors, but no change at the D9S171 locus was observed in 17 tumors. These results suggest that: (i) homozygous deletion is the main mechanism of inactivation of p16/CDKN2 and p15/MTS2 in ovarian tumorigenesis; (ii) inactivation of p16/CDKN2 and p15/MTS2 may be the histological type-specific events involved in ovarian tumorigenesis; and (iii) inactivation of p16/CDKN2 is potentially involved in the progression of ovarian tumors in advanced stages.

Simultaneous expression of the ras p21 and p53 proteins in human endometrial carcinomas

The expression of ras-encoded p21 and p53 proteins was analyzed by immunohistochemical staining with monoclonal antibodies in 26 paraffin-embedded specimens (25 endometrial carcinomas and 1 uterine carcinosarcoma) taken from Polish women. The biotin-streptavidin-peroxidase detection system was employed. ras p21 protein was expressed in 68% of the specimens and p53 positive staining was noted in 36% of the carcinomas. Simultaneous expression of the ras p21 and p53 proteins was demonstrated in 8 (32%) out of the 25 specimens. Except one case, where the p53 protein was expressed, ras p21 protein was also detected. Both proteins were demonstrated in the sole case of carcinosarcoma. A difference between the detection of simultaneous expression of the ras p21 and p53 proteins in correlation with FIGO stages I to II-IV has been reported (22% v. 57% respectively). These data indicate, that ras p21 correlated with p53 positive staining in one-third of the endometrial cancers analyzed. The simultaneous detection of both proteins correlated with the advanced clinical stage of human endometrial carcinomas.

Microsatellite instability and alterations in the hMSH2 gene in human ovarian cancer

The role of the replication error-positive (RER+) phenotype in the development of specific subtypes of sporadic ovarian carcinomas was examined by screening for the presence of microsatellite instability (MI) in 47 tumors. The overall frequency of ovarian MI was 17% only. However, MI occurred in 50% of the ovarian endometrioid-type tumors, which was significantly more often than in all the other histological subtypes combined (8%). Five of the 8 RER+ tumors exhibited most marked type I instability, possibly representing a different mechanism than for the remaining type 2 tumors. The cDNA of the mutation suppression gene hMSH2, the gene most often associated with MI, was screened for alterations in 8 MI-positive and 5 MI-negative ovarian tumors. Only 3 changes were found. Complete loss of hMSH2 mRNA expression was detected in I tumor, while another expressed only an abnormal transcript containing a deletion of exon 3. One additional RER+ serous adenocarcinoma contained a rare polymorphism with a non-conservative amino acid change. One of 8 RER+ tumors showed loss of heterozygosity at the hMSH2 loci. Genetic instability, caused in part by alterations in the hMSH2 gene, may play an important role in the sporadic endometrioid subtype of ovarian tumors. Other mutator-phenotype genes may be responsible for the remaining cases of RER+ ovarian tumors.

p53 mutation in carcinomas arising in ovarian cystic teratomas

Carcinomas arising in mature cystic teratomas of the ovaries from nine women were examined for the presence of p53 mutations. The nine tumors comprised six squamous cell carcinomas, one squamous cell carcinoma in situ, one undifferentiated small cell carcinoma, and one mucoepidermoid carcinoma. Abnormal nuclear accumulation of the p53 protein was observed in four of the tumors. Genomic DNA was extracted from formalin-fixed, paraffin-embedded tissue blocks and subjected to polymerase chain reaction (PCR) for specific amplification of the p53 gene exons 5-8, followed by direct chemiluminescence sequencing analysis. A frameshift mutation in exon 8 (codon 278, CCT > del T; stop at codon 344) was detected in one poorly differentiated squamous cell carcinoma. The samples were also evaluated for the possible association of 'benign' and 'malignant' types of human papillomavirus (HPV) by PCR using universal primer sets. None of the samples contained detectable HPV genome. These data suggest that p53 mutations are relatively uncommon in secondary carcinomas developing in ovarian dermoid cysts, although the number of samples studied was admittedly small.