Pathogenesis of ovarian cancer: lessons from morphology and molecular biology and their clinical implications

Rapidly increasing incidence of papillary serous carcinoma of the peritoneum in the United States: fact or artifact?

Papillary serous carcinoma of the peritoneum (PSCP) has been recognized for almost 5 decades, but little is known about the etiology or pathogenesis of this uncommon malignancy. The objective of this analysis was to examine trends in the incidence of PSCP in the United States. Invasive PSCP cases (N = 4,389) were identified through 24 population-based registries in the United States during the period 1995-2004. Incidence rates were calculated per million population. PSCP is a disease of older women, with few cases diagnosed before the age of 40 years. The incidence of PSCP was 64% lower among black women and 47% lower among Asian-Pacific Islander women compared with white women. Rates among Hispanic women were 39% lower than among non-Hispanic women. The majority of PSCP (68%) was diagnosed at a distant stage, underscoring the difficulty of diagnosing this malignancy. The incidence of PSCP has increased dramatically during the past decade in the United States with the greatest rise (>13% per year) among non-Hispanic and white women. This trend was more pronounced among older women and women with early stage disease. The incidence of PSCP shows substantial racial and ethnic diversity. The increase in the rate of PSCP among all racial and ethnic groups during the 10-year observation period is cause for some alarm. Although the reason for this temporal trend is unknown, some of the increase may be attributable to reclassification of ovarian carcinoma to the peritoneum.

Mutational analysis of KRAS, BRAF, and TP53 genes of ovarian serous carcinomas in Korean women

PURPOSE

To assess the prevalence of KRAS, BRAF, and TP53 mutations in cases of low-grade and high-grade serous carcinomas and to evaluate the clinical outcomes of these morphologically distinct carcinomas.

MATERIALS AND METHODS

Patients with primary invasive serous carcinomas were classified according to the universal grading system. Grade 2 serous tumors were excluded. A total of 100 patients were included for clinical evaluation. Thirty-seven patients, including 20 with low-grade and 17 with high-grade carcinomas, were selected for mutational analysis.

RESULTS

The low-grade carcinoma group was characterized by young age and premenopausal period compared with the high-grade carcinoma group, but there were no statistically significant differences in stage, metastasis of lymph node and residual disease. There were no statistically significant differences in survival rates, however, the low-grade carcinoma group showed a trend for improved progression-free survival compared with the high-grade carcinoma group of early stage (p = 0.064). Mutations in KRAS and BRAF were found in 6 (30%) and 2 (10%) patients in the low-grade carcinoma group, respectively, however, they were not found in the high-grade carcinoma group. KRAS and BRAF mutations were mutually exclusive, and both mutations were observed in 40% (8/20). The frequency of TP53 mutations in low-grade and high-grade carcinoma groups were found in 20% (4/20) and 70.6% (12/17), respectively (p = 0.009).

CONCLUSION

Low-grade serous carcinoma shows mutation pattern different from that with high-grade carcinoma. As there were no significant differences in stage distribution and survival, especially in advanced stage, we suggest that more studies are needed to segregate these patients into distinct disease entities.

Variant HNF1 modulates epithelial plasticity of normal and transformed ovary cells

Ovarian carcinoma arises from the ovarian surface epithelium, which undergoes phenotypic changes characteristic of müllerian epithelium during the first stages of tumorigenesis. The variant isoform of the hepatocyte nuclear factor 1 (vHNF1) is a transcription factor involved in the development of tissues derived from the müllerian duct. Here, we show that vHNF1 knockdown in two ovarian carcinoma cell lines, SKOV3 and IGROV1, leads to reduced E-cadherin (E-cadh) expression and decreased proliferation rate. Accordingly, SKOV3 cells ectopically expressing a dominant-negative (DN) vHNF1 mutant undergo an epithelial-mesenchymal-like transition, acquiring a spindle-like morphology, loss of E-cadh, and disrupted cell-cell contacts. Gene expression profiling of DNvHNF1 cells on the basis of a newly compiled list of epithelial-mesenchymal transition-related genes revealed a correlation between vHNF1 loss-of-function and acquisition of the mesenchymal phenotype. Indeed, phenotypic changes were associated with increased Slug transcription and functionality. Accordingly, vHNF1-transfected immortalized ovarian surface epithelial cells showed down-regulation of Snail and Slug transcripts. In DNvHNF1-transfected SKOV3 cells, growth rate decreased, and in vHNF1-transfected immortalized ovarian surface epithelial cells, growth rate increased. By immunohistochemistry, we found a strong association of vHNF1 with E-cadh in clear cell and in a subset of serous carcinomas, data that could potentially contribute in distinguishing different types of ovarian tumors. Our results may help in understanding the biology of ovarian carcinoma, identifying early detection markers, and opening potential avenues for therapeutic intervention.

KRAS mutation analysis in ovarian samples using a high sensitivity biochip assay

Background

Mutations in the KRAS gene are one of the most frequent genetic abnormalities in ovarian carcinoma. They are of renewed interest as new epidermal growth factor receptor (EGFR)-targeted therapies are being investigated for use in ovarian carcinoma. As KRAS mutations are associated with poor response and resistance to EGFR-targeting drugs, this study was conducted to obtain more information on the spectrum of KRAS mutations in ovarian carcinoma.

Methods

The presence of KRAS mutations in codon 12 and 13 was analyzed in frozen and formalin-fixed paraffin-embedded (FFPE) tissue with a low density biochip platform. 381 malignant (29 borderline malignancy, 270 primary carcinomas, and 82 recurrent carcinomas) and 22 benign tissue samples from a total of 394 patients were examined. KRAS mutational status of each sample was correlated with dignity, FIGO stage, grade, histology, and survival.

Results

KRAS mutations were found in 60 (15%) samples with 58 samples deriving from malignant tissue and 2 samples deriving from benign tissue. In 55 (92%) samples codon 12 was found to be mutated. Frozen and FFPE samples concurred with respect to KRAS mutation status.

Conclusion

KRAS mutation is a common event in ovarian cancer primarily in carcinomas of lower grade, lower FIGO stage, and mucinous histotype. The KRAS mutational status is no prognostic factor for patients treated with standard therapy. However, in line with experience from colorectal cancer and non-small-cell-lung cancer (NSCLC), it may be important for prediction of response to EGFR-targeted therapies.

Hereditary ovarian carcinoma: heterogeneity, molecular genetics, pathology, and management

Hereditary ovarian cancer accounts for at least 5% of the estimated 22,000 new cases of this disease during 2009. During this same time, over 15,000 will die from malignancy ascribed to ovarian origin. The bulk of these hereditary cases fits the hereditary breast-ovarian cancer syndrome, while virtually all of the remainder will be consonant with the Lynch syndrome, disorders which are autosomal dominantly inherited. Advances in molecular genetics have led to the identification of BRCA1 and BRCA2 gene mutations which predispose to the hereditary breast-ovarian cancer syndrome, and mutations in mismatch repair genes, the most common of which are MSH2 and MLH1, which predispose to Lynch syndrome. These discoveries enable relatively certain diagnosis, limited only by their variable penetrance, so that identification of mutation carriers through a comprehensive cancer family history might be possible. This paper reviews the subject of hereditary ovarian cancer, with particular attention to its molecular genetic basis, its pathology, and its phenotypic/genotypic heterogeneity.

Incidence of ovarian, peritoneal, and fallopian tube carcinomas in the United States, 1995-2004

OBJECTIVE

The objective of this analysis was to describe the distribution of pelvic carcinomas in the United States by demographic, pathologic, and clinical features.

METHODS

Carcinomas of the ovary (n = 112,541), peritoneum (n = 6,458), and fallopian tube (n = 3,479) were identified through 24 population-based registries in the United States during the period 1995 to 2004. Age-adjusted incidence rates were calculated per million population using counts derived from the 2000 U.S. census.

RESULTS

The age-adjusted incidence rate for ovarian carcinoma (119.9 per million) was substantially higher than for peritoneal (6.78 per million) or fallopian tube (3.72 per million) carcinomas. White women had the highest rates for all three malignancies. Rates for peritoneal carcinoma were lowest among Black women (2.88 per million) and rates for fallopian tube carcinoma were lowest among Hispanic women (2.45 per million). Serous carcinomas were the most commonly diagnosed histologic type for all anatomic sites. Peritoneal carcinomas were diagnosed at later ages (mean, 67 years) and more advanced stages (85% regional/distant) compared with fallopian tube carcinomas (mean, 64 years; 62% regional/distant) and ovarian carcinomas (mean, 63 years; 76% regional/distant). Incidence for all three pelvic carcinomas was lowest in the South. Time trend analyses between 1973 and 2005 exhibited a significant decline in ovarian carcinoma incidence and rises in the rates of peritoneal and fallopian tube cancers.

CONCLUSIONS

Similarities in the incidence patterns for ovarian, peritoneal, and fallopian tube carcinomas support the likelihood of a common molecular pathogenesis.

Ovarian cancer: a clinical challenge that needs some basic answers

Kate Lawrenson and Simon Gayther discuss two studies of ovarian cancer inPLoS Medicine, one on clinico-pathological heterogeneity and one on gene expression profiling.

Validation of tissue microarray technology in ovarian cancer: results from the Nurses' Health Study

BACKGROUND

Tissue microarrays (TMAs) allow high-throughput evaluation of protein expression from archived tissue samples. We identified characteristics specific to ovarian cancer that may influence TMA interpretation.

METHODS

TMAs were constructed using triplicate core samples from 174 epithelial ovarian cancers. Stains for p53, Ki-67, estrogen receptor-alpha, progesterone receptor, Her-2, WT-1, cytokeratin 7, and cytokeratin 20 were evaluated by intraclass correlation coefficients, Spearman correlation coefficients, the effect of sample age, and tumor histology on the ability to score the cores, and inter-rater reliability.

RESULTS

The interclass correlation coefficient and the mean Spearman correlation coefficients among 3 cores were > or = 0.91 and 0.87, respectively. Tissue age and tumor histology were not predictive of an inability to evaluate stains, but borderline tumors had a 2 to 4-fold increase in the risk of having uninterpretable cores over invasive tumors. There was moderate to substantial concordance between the two pathologists for estrogen receptor-alpha [Cohen's Kappa (kappa), 0.79] and Ki-67 (kappa, 0.52). The prevalence of positive staining cells by histologic type was comparable with previous studies.

CONCLUSION

TMA is a valid method for evaluating antigen expression in invasive ovarian cancer but should be used with caution for borderline tumors. We suggest several methods of quality control based on intercore comparisons and show that some antigens may be affected by age of the samples.

The fiber arrangement of the pathological human tympanic membrane

Aerobic glycolysis is an important metabolic adaptation of cancer cells. There is growing evidence that oxidative phosphorylation is also an active metabolic pathway in many tumors, including in high grade serous ovarian cancer. Metastasized ovarian tumors use fatty acids for their energy needs. There is also evidence of ovarian cancer stem cells privileging oxidative phosphorylation (OXPHOS) for their metabolic needs. Metformin and thiazolidinediones such as rosiglitazone restrict tumor growth by inhibiting specific steps in the mitochondrial electron transport chain. These observations suggest that strategies to interfere with oxidative phosphorylation should be considered for the treatment of ovarian tumors. Here, we review the literature that supports this hypothesis and describe potential agents and critical control points in the oxidative phosphorylation pathway that can be targeted using small molecule agents. In this review, we also discuss potential barriers that can reduce the efficacy of the inhibitors of oxidative phosphorylation.