KRAS (but not BRAF) mutations in ovarian serous borderline tumour are associated with recurrent low-grade serous carcinoma

The oncogene KRAS promotes cancer cell dissemination by stabilizing spheroid formation via the MEK pathway

Background

Peritoneal dissemination is a critical prognostic factor in ovarian cancer. Although stabilized spheroid formation promotes cancer cell peritoneal dissemination in ovarian cancer, the associated oncogenes are unknown. In this study, we assessed the role of the KRAS oncogene in ovarian cancer cell dissemination, focusing on the stability of cells in spheroid condition, as well as the modulation of intracellular signaling following spheroid transformation.

Methods

We used ID8, a murine ovarian cancer cell line, and ID8-KRAS, an oncogenic KRAS (G12 V)-transduced ID8 cell line in this study. Spheroid-forming (3D) culture and cell proliferation assays were performed to evaluate the growth characteristics of these cells. cDNA microarray analysis was performed to identify genes involved in KRAS-associated signal transduction in floating condition. A MEK inhibitor was used to evaluate the effect on cancer peritoneal dissemination.

Results

Cell viability and proliferation in monolayer (2D) cultures did not differ between ID8 and ID8-KRAS cells. However, the proportions of viable and proliferating ID8-KRAS cells in 3D culture were approximately 2-fold and 5-fold higher than that of ID8, respectively. Spheroid-formation was increased in ID8-KRAS cells. Analysis of peritoneal floating cells obtained from mice intra-peritoneally injected with cancer cells revealed that the proportion of proliferating cancer cells was approximately 2-fold higher with ID8-KRAS than with ID8 cells. Comprehensive cDNA microarray analysis revealed that pathways related to cell proliferation, and cell cycle checkpoint and regulation were upregulated specifically in ID8-KRAS cells in 3D culture, and that some genes partially regulated by the MEK-ERK pathway were upregulated only in ID8-KRAS cells in 3D culture. Furthermore, a MEK inhibitor, trametinib, suppressed spheroid formation in 3D culture of ID8-KRAS cells, although trametinib did not affect 2D-culture cell proliferation. Finally, we demonstrated that trametinib dramatically improved the prognosis for mice with ID8-KRAS tumors in an in vivo mouse model.

Conclusions

Our data indicated that KRAS promoted ovarian cancer dissemination by stabilizing spheroid formation and that the MEK pathway is important for stabilized spheroid formation. Disruption of spheroid formation by a MEK inhibitor could be a therapeutic target for cancer peritoneal dissemination.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4922-4) contains supplementary material, which is available to authorized users.

Triptolide as a novel agent in pancreatic cancer: the validation using patient derived pancreatic tumor cell line

Background

Triptolide induces apoptosis and DNA damage followed by inhibition of DNA repair associated gene expression. However, there is the limited data for biomarker to predict the benefit to triptolide in various cancers including pancreatic cancer.

Methods

We investigated the anti tumor efficacy of triptolide in various pancreatic cancer cell lines (Capan-1, Capan-2, SNU-213, SNU-410, HPAFII, and Hs766T) and patient derived cells (PDCs) from metastatic pancreatic cancer patients.

Results

In vitro cell viability assay for triptolide in 6 PC cell lines, the IC₅₀ was 0.01 uM, 0.02 uM, 0.0096 uM for triptolide in Capan-1, Capan-2 and SNU-213. However, the growth of tumor cells was not significantly reduced by triptolide in Hs766T, SNU-410 and HPAFII. The distinct difference of gene expression was also observed between Capan-1, Capan-2 and SNU-213 and Hs766T, SNU-410 and HPAFII. In analysis of pathway using gene expression profiles, the integrin mediated RAS signaling pathway was associated with the sensitivity of the triptolide in PC cell lines. Immunoblot assay showed that Chk2 phosphorylation after triptolide was distinctively observed in SNU-213 sensitive to triptolide but, not in SNU-410 insensitive to triptolide. This finding in immunoblot assay was also reproduced in PDCs originated from pancreatic cancer patients.

Conclusions

Our findings might be helpful to completely capture the subset of patients who may benefit to tripolide (minnelide). More robust biomarkers such as KRAS mutation and Chk2 phosphorylation and careful clinical trial design using triptolide (minnelide) are warranted.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4995-0) contains supplementary material, which is available to authorized users.

Missing information in statewide and national cancer databases: Correlation with health risk factors, geographic disparities, and outcomes

OBJECTIVE

The objectives of this study were to analyze factors associated with outcomes and missing data in women with epithelial ovarian cancer using institutional, state and national databases.

METHODS

Data were abstracted from the University of Virginia cancer registry, Virginia Department of Health (VDH) database, and Surveillance, Epidemiology, and End Results (SEER) Program and analyzed for correlations with demographics, cancer characteristics, and outcomes. Statewide spatial associations between health risk factors such as smoking, obesity, and missing grade/stage were evaluated using bivariate LiSA in Geoda.

RESULTS

There were 524 institutional, 3544 VDH, and 44,464 SEER cases of epithelial ovarian cancer. Institutional cases were younger, most often of white race, had increased grade 1, and decreased unknown grade and stage (all p < 0.001). Significant predictors of unknown grade were non-white race, older age, no surgery, unknown stage/stage IV, and unknown histology/adenocarcinoma. Unknown grade correlated with a significant survival disadvantage. Missing stage and grade correlated with county-level obesity and smoking, as rural regions in Southwest and Southside Virginia had high rates of health risk factors and missing stage/grade compared to urban, affluent regions in Northern Virginia.

CONCLUSIONS

Over a third of nationally reported cases have an unknown grade and 10-20% have an unknown stage which correlates with the worst survival. Predictors of unknown grade include insurance, age, race, smoking status, obesity, and rural setting. Missing data may represent geographical differences or disparities in cancer care available as significantly fewer cases had an unknown grade/stage at a tertiary academic medical center compared to VDH and SEER.

A Cell Line-based Immunohistochemical p53 Expression Pattern Control Panel

TP53 gene mutations are known to manifest in distinct p53 immunohistochemical staining patterns; overexpression, wild-type, and null. These stratified staining patterns are routinely utilized in subtyping ovarian cancer subtypes. Three ovarian cancer cell lines were used in the construction of an immunohistochemical p53 expression pattern control panel that highlight respective TP53 mutation status. The cell line control panel sections demonstrated consistent clean and easily interpretable p53 immunohistochemical staining. Procured resection, biopsy, and cytologic specimens were submitted along with either standard control tissue or a p53 cell line control panel to pathologists of varying experience for interrater reliability analysis. Individual interrater reliability was near-perfect and was improved with the p53 cell line control panel when compared with the tissue control. The cell line control panel demonstrated decreased misinterpretation of null expression pattern as wild-type. Next-generation sequencing analysis was performed on the cell lines and select cases, in which there was discordance in p53 expression pattern interpretation. Next-generation sequencing analysis demonstrated low-frequency variant mutations in some cases in which there was reviewer discordance. This study suggests the addition of a p53 cell line expression pattern control panel could potentially increase p53 interpretation accuracy for ovarian cancer subtypes. We developed a cell line-based p53 control panel that has the potential to increase individual interrater reliability for p53 immunohistochemical expression pattern determination, support immunohistochemical optimization, and direct submission of difficult to interpret p53 staining cases to next-generation sequencing.

Late recurrence of pStage 1 low-grade serous ovarian tumor presenting as a symptomatic bone metastasis: a case report

BACKGROUND

Ovarian serous borderline tumor/atypical proliferative serous tumor (SBT/APST) is characterized by presenting at an early stage and much longer survival than high-grade serous carcinoma. Given that the prognosis of ovarian SBT/APST with no invasive features is excellent, remote relapse after surgery can pose a diagnostic pitfall. Bone metastasis as transformed low-grade carcinoma is an extremely rare initial presentation of recurrence in patients whose primary tumor was confined to the ovaries.

CASE PRESENTATION

A 55-year-old Japanese woman who had undergone surgery for a right ovarian tumor 13 years previously presented with right-lateral chest pain and neurologic abnormalities in the lower limbs. Computed tomography (CT) scan and magnetic resonance imaging revealed an irregular mass in the right arch of the 12th thoracic vertebra, extending through the intervertebral foramen and into surrounding soft tissue, the maximum diameter of the whole mass being 78 mm. Pathological examination of a CT-guided needle biopsy of the paraspinal lesion demonstrated papillary cell clusters with blunt nuclear atypia and psammomatous calcification that were positive for PAX8, estrogen receptor, and WT1, but negative for thyroglobulin on immunohistochemical testing, and of a P53 non-mutational pattern. On clinicopathologic review, the previous 13- × 11- × 9-cm ovarian tumor was an intracystic and exophytic papillary growth without surface involvement; it had ruptured intraoperatively. Microscopically there was serous epithelium with minimal cytologic atypia proliferating in hierarchical branches with no invasive foci or micropapillary components. The tumor was confined to the right ovary with no peritoneal implants. Neither primary nor metastatic tumor harbored KRAS/BRAF mutations according to polymerase chain reaction using formalin-fixed paraffin-embedded tissues. We concluded that, after a 13-year disease-free interval, the paraspinal lesion was bone metastasis of low-grade carcinoma originating from the ovarian SBT/APST. The patient received radiotherapy for the paraspinal lesion followed by administration of paclitaxel and carboplatin plus bevacizumab and remains alive 168 months after the initial surgery.

CONCLUSIONS

Pathologists and radiologists should not exclude late recurrence of ovarian SBT/APST when bone metastases are suspected, even when neither peritoneal nor lymph node involvement are detected. Long-term surveillance of women with ovarian serous tumors with no invasive features is recommended.

Extracellular-Regulated Kinases: Signaling From Ras to ERK Substrates to Control Biological Outcomes

The extracellular-regulated kinases ERK1 and ERK2 are evolutionarily conserved, ubiquitous serine-threonine kinases that are involved in regulating cellular signaling in both normal and pathological conditions. Their expression is critical for development and their hyperactivation is a major factor in cancer development and progression. Since their discovery as one of the major signaling mediators activated by mitogens and Ras mutation, we have learned much about their regulation, including their activation, binding partners and substrates. In this review I will discuss some of what has been discovered about the members of the Ras to ERK pathway, including regulation of their activation by growth factors and cell adhesion pathways. Looking downstream of ERK activation I will also highlight some of the many ERK substrates that have been discovered, including those involved in feedback regulation, cell migration and cell cycle progression through the control of transcription, pre-mRNA splicing and protein synthesis.

KRAS mutation of extraovarian implants of serous borderline tumor: prognostic indicator for adverse clinical outcome

In contrast to non-invasive extraovarian implants, invasive implants of ovarian serous borderline tumor/atypical proliferative serous tumor are associated with adverse outcome and have been reclassified as low-grade serous carcinoma. Mutations of KRAS and/or BRAF have been reported in up to 50% of serous borderline tumor/atypical proliferative serous tumor. We investigated KRAS and BRAF mutation frequencies in the two types of implants of serous borderline tumor/atypical proliferative serous tumor in correlation with clinical outcome. Forty-two implants of serous borderline tumor from 39 patients were included (invasive implants/low-grade serous carcinoma, n=20; non-invasive implants, n=22). KRAS mutation was found in 12 of 20 invasive implants (60%) and 3 of 22 non-invasive implants (14%). BRAF V600E mutation was found in 1 of 22 non-invasive implants (5%) and none in invasive implants (0%). Invasive implants were more frequently associated with higher stage disease. Nine of 14 patients (64%) with KRAS mutation were found to have stage IIIC disease, while 5 of 24 patients (20%) without the mutation had stage IIIC disease. Patients with invasive implants had higher recurrence rate compared to those with non-invasive implants (60 vs 14 %, P=0.0003, log-rank test) and worse disease-specific survival (P=0.0008, log-rank test). Regardless of the histological subtypes, patients with KRAS mutation positive implants had significantly higher recurrence rate than those without the mutation (71 vs 21%, P=0.0021, log-rank test) and an unfavorable disease-specific survival (P=0.0104, log-rank test). In conclusion, compared to those with non-invasive implants, patients with invasive implants present with higher stage of the disease, higher recurrence rate and worse survival. KRAS mutation, but not BRAF V600E mutation, is significantly associated with invasive implants of serous borderline tumor. Regardless of the histological subtypes of the implants, KRAS mutation is a significant prognostic indicator for high risk of tumor recurrence and worse disease-specific survival.

Low-grade serous carcinoma of the ovary or peritoneum

Over the past decade, the strategy for clinical trial design in making progress against epithelial cancers of the ovary/peritoneum/fallopian tube has changed dramatically. The NRG (GOG) Rare Tumor Committee has been a leader in this transformation. No longer does 'one size fit all'. Rather, separate clinical trials for rare subtypes have been developed and, in some cases, completed. An enhanced understanding of their pathologic diagnosis, molecular biology, and clinical behavior has galvanized this change. Low-grade serous carcinoma may occur de novo or following an initial diagnosis of serous tumor of low malignant potential. It is characterized by young age at diagnosis, relative chemoresistance, and prolonged survival compared with high-grade serous carcinoma. Historically, conventional chemotherapy has demonstrated very limited activity in this subtype. Hormonal therapy may provide benefit in this subtype. Preclinical studies have identified and elucidated genes and pathways-MAP kinase pathway, IGF1-R, the angiogenesis pathway, and possibly, the PI3K/AKT/mTOR pathway in low-grade serous carcinoma. To date, clinical evidence supports the activity of MEK and BRAF inhibitors and bevacizumab. Further pursuit of targeted therapy trials is clearly warranted.

Low frequency of BRAF and KRAS mutations in Chinese patients with low-grade serous carcinoma of the ovary

BACKGROUND

Mounting evidence has shown that KRAS and BRAF are somatic mutations associated with low grade serous carcinoma (LGSC) of the ovary. However, the frequency of KRAS or BRAF mutation was variable in literatures, with a frequency of 16-54% for KRAS mutation and 2-33% for BRAF mutation. Meanwhile, the prognostic significance of KRAS or BRAF mutation remains controversial.

METHODS

Codons 12 and 13 of exon 2 of KRAS gene and exon 15 of BRAF gene were analyzed using direct Sanger sequencing in 32 cases of LGSC of the ovary. The associations between KRAS or BRAF mutation and clinicopathological characteristics, overall survival (OS) and disease-free survival (DFS) were statistically analyzed.

RESULTS

KRAS mutation was observed in nine cases (9/32, 28%) and BRAF mutation in two cases (2/32, 6%). KRAS and BRAF mutations were mutually exclusive. Neither KRAS nor BRAF mutation was statistically associated with OS or DFS in our cohort, although there was a favorable prognostic trend in patients with KRAS G12D mutation than those with KRAS G12 V mutation or wild-type KRAS for OS.

CONCLUSIONS

The present study indicated a low frequency of BRAF or KRAS mutation in Chinese patients with LGSC of the ovary, and neither KRAS nor BRAF mutation is a prognostic factor.

The molecular pathology of ovarian serous borderline tumors

Molecular studies in ovarian serous borderline tumors (OSBTs) have been used to understand different aspects of this neoplasm. (i) Pathogenesis, Kras and Braf mutations represent very early events in the tumorigenesis of OSBT as both are detected in serous cystadenomas associated with OSBTs. In contrast, serous cystadenomas without OSBTs do not show Kras or Braf mutations. In OSBTs, Kras mutations range from 17% to 39.5%, while Braf mutations range from 23% to 48%. The former is comparable with the range of Kras mutations in ovarian low-grade serous carcinomas (OLGSCa), 19%-54.5%. In contrast, Braf mutations in OLGSCa range from 0% to 33%. Serous cystadenomas appear to progress to OSBT due to a Braf mutation, but this mutation is rarely involved in the progression to OLGSCa. OSBTs with Braf mutation are associated with cellular senescence and up-regulation of tumor suppressor genes. In contrast, OSBTs without a Braf mutation may progress to OLGSCa due to Kras mutation or some other genetic alterations. (ii) The relationship between OSBTs and the extraovarian disease, a monoclonal versus mutifocal origin? This is still matter of debate as studies using different techniques have failed to settle this controversy. (iii) Biological behavior, Braf mutations appear to have a protective role against the progression of OSBT to OLGSCa, while Kras mutations are commonly seen in cases of OSBT that recurred as LGSCa. Nevertheless, LGSCa as a recurrence of an OSBT can originate from OSBTs with or without detectable Kras mutations. Also, it appears to be an association between Kras G12v mutation and a more aggressive phenotype of OSBT that recurred as LGSCa. (iv) Actionable targets, currently there are limited data. It has been reported that cancer cell lines with Kras G12v mutation are more sensitive to selumetinib than cell lines with wild-type Kras.

Mutation of NRAS is a rare genetic event in ovarian low-grade serous carcinoma

Activating mutations involving the members of the RAS signaling pathway, including KRAS, NRAS, and BRAF, have been reported in ovarian low-grade serous carcinoma and its precursor lesion, serous borderline tumor (SBT). Whether additional genetic alterations in the RAS oncogene family accumulate during the progression of SBT to invasive low-grade serous carcinoma (LGSC) remains largely unknown. Although mutations of KRAS and BRAF occur at a very early stage of progression, even preceding the development of SBT, additional driving events, such as NRAS mutations, have been postulated to facilitate progression. In this study, we analyzed NRAS exon 3 mutational status in 98 cases that were diagnosed with SBT/atypical proliferative serous tumor, noninvasive LGSC, or invasive LGSC. Of the latter, NRAS Q61R (CAA to CGA) mutations were detected in only 2 of 56 (3.6%) cases. The same mutation was not detected in any of the SBTs (atypical proliferative serous tumors) or noninvasive LGSCs. Mutational analysis for hotspots in KRAS and BRAF demonstrated a wild-type pattern of KRAS and BRAF in one of the NRAS-mutated cases. Interestingly, another LGSC case with NRAS mutation harbored a concurrent BRAF V600L mutation. These findings indicate that, although recurrent NRAS mutations are present, their low prevalence indicates that NRAS plays a limited role in the development of LGSC. Further studies to identify other oncogenic events that drive LGSC progression are warranted.

Impact of lympho-vascular space invasion on tumor characteristics and survival outcome of women with low-grade serous ovarian carcinoma

BACKGROUND AND OBJECTIVES

To examine association of lympho-vascular space invasion (LVSI) with clinico-pathological factors and to evaluate survival of women with low-grade serous ovarian carcinoma containing areas of LVSI.

METHODS

This is a multicenter retrospective study examining consecutive cases of surgically treated stage I-IV low-grade serous ovarian carcinoma (n = 178). Archived histopathology slides for the ovarian tumors were reviewed, and LVSI was scored as present or absent. LVSI status was correlated to clinico-pathological findings and survival outcome.

RESULTS

LVSI was seen in 79 cases (44.4%, 95% confidence interval [CI] 37.1-51.7). LVSI was associated with increased risk of omental metastasis (87.0% vs 64.9%, odds ratio [OR] 3.62, P = 0.001), high pelvic lymph node ratio (median 12.9% vs 0%, P = 0.012), and malignant ascites (49.3% vs 32.6%, OR 2.01, P = 0.035). On multivariable analysis, controlling for age, stage, and cytoreductive status, presence of LVSI in the ovarian tumor remained an independent predictor for decreased progression-free survival (5-year rates 21.0% vs 35.7%, adjusted-hazard ratio 1.57, 95%CI 1.06-2.34, P = 0.026). LVSI was significantly associated with increased risk of recurrence in lymph nodes (OR 2.62, 95%CI 1.08-6.35, P = 0.047).

CONCLUSION

LVSI in the ovarian tumor is associated with adverse clinico-pathological characteristics and decreased progression-free survival in women with low-grade serous ovarian carcinoma.

Pathology of borderline and invasive cancers

Epithelial ovarian tumors are heterogeneous neoplasms primarily classified according to cell type. They are further subdivided into benign, borderline, and malignant (carcinomas), and this subdivision is very important as it correlates with behavior. Borderline ovarian tumors show epithelial proliferation higher than that seen in their benign counterparts and variable nuclear atypia; however, in contrast to carcinomas, there is no destructive stromal invasion, and their prognosis is much better. Ovarian carcinomas are the most common ovarian cancers and the most lethal gynecological malignancies. On the basis of histopathology and molecular genetics, they are divided into five types (high-grade serous (70%), endometrioid (10%), clear cell (10%), mucinous (3%), and low-grade serous carcinomas (<5%)), which are morphologically diverse and account for over 95% of cases. These tumors are essentially distinct diseases, as indicated by differences in epidemiological and genetic risk factors, precursor lesions, patterns of spread, molecular alterations, response to chemotherapy, and prognosis. For a successful specific treatment, reproducible histopathological diagnosis of the tumor cell type is critical.

Differences in MEK inhibitor efficacy in molecularly characterized low-grade serous ovarian cancer cell lines

Advanced or recurrent low-grade serous ovarian cancers (LGSC) are resistant to conventional systemic treatments. LGSC carry mutations in RAS or RAF, leading to several clinical trials evaluating MEK inhibitors (MEKi). As LGSC cell lines and xenografts have been difficult to establish, little is known about the efficacy and on-target activity of MEKi treatment in this disease. We compared four different MEKi (trametinib, selumetinib, binimetinib and refametinib) in novel LGSC patient-derived cell lines. Molecular characterization of these cells included copy-number variation and hotspot mutational analysis. Proliferation, apoptosis and cell viability assays were used to study drug efficacy. MEKi on-target efficacy was measured using western blotting and isoelectric point focusing for ERK1/2 phosphorylation. Ten LGSC cell lines were derived from 7 patients with advanced/recurrent disease. Copy number variation showed significant heterogeneity among cell lines, however all samples showed deletions in chromosome 9p21.3, and frequent copy number gains in chromosomes 12 and 20. Mutations in KRAS/NRAS were identified in 4 patients (57%) and RAS mutation status was not associated with higher baseline levels of ERK phosphorylation. Different degrees of MEKi sensitivity were observed in the LGSC cell lines. Two cell lines, both with KRAS mutations, were highly sensitive to MEKi. Drug anti-proliferative efficacy correlated with the degree of inhibition of ERK phosphorylation, with trametinib being the most potent agent. Differences in MEKi efficacy were observed in LGSC cell lines. Trametinib showed the greatest anti-proliferative effects. This study serves as a basis for much needed future research on MEKi drug efficacy in LGSC.

Molecular profiling of low grade serous ovarian tumours identifies novel candidate driver genes

Low grade serous ovarian tumours are a rare and under-characterised histological subtype of epithelial ovarian tumours, with little known of the molecular drivers and facilitators of tumorigenesis beyond classic oncogenic RAS/RAF mutations. With a move towards targeted therapies due to the chemoresistant nature of this subtype, it is pertinent to more fully characterise the genetic events driving this tumour type, some of which may influence response to therapy and/or development of drug resistance. We performed genome-wide high-resolution genomic copy number analysis (Affymetrix SNP6.0) and mutation hotspot screening (KRAS, BRAF, NRAS, HRAS, ERBB2 and TP53) to compare a large cohort of ovarian serous borderline tumours (SBTs, n = 57) with low grade serous carcinomas (LGSCs, n = 19). Whole exome sequencing was performed for 13 SBTs, nine LGSCs and one mixed low/high grade carcinoma. Copy number aberrations were detected in 61% (35/57) of SBTs, compared to 100% (19/19) of LGSCs. Oncogenic RAS/RAF/ERBB2 mutations were detected in 82.5% (47/57) of SBTs compared to 63% (12/19) of LGSCs, with NRAS mutations detected only in LGSC. Some copy number aberrations appeared to be enriched in LGSC, most significantly loss of 9p and homozygous deletions of the CDKN2A/2B locus. Exome sequencing identified BRAF, KRAS, NRAS, USP9X and EIF1AX as the most frequently mutated genes. We have identified markers of progression from borderline to LGSC and novel drivers of LGSC. USP9X and EIF1AX have both been linked to regulation of mTOR, suggesting that mTOR inhibitors may be a key companion treatment for targeted therapy trials of MEK and RAF inhibitors.

The Dualistic Model of Ovarian Carcinogenesis: Revisited, Revised, and Expanded

Since our proposal of a dualistic model of epithelial ovarian carcinogenesis more than a decade ago, a large number of molecular and histopathologic studies were published that have provided important insights into the origin and molecular pathogenesis of this disease. This has required that the original model be revised and expanded to incorporate these findings. The new model divides type I tumors into three groups: i) endometriosis-related tumors that include endometrioid, clear cell, and seromucinous carcinomas; ii) low-grade serous carcinomas; and iii) mucinous carcinomas and malignant Brenner tumors. As in the previous model, type II tumors are composed, for the most part, of high-grade serous carcinomas that can be further subdivided into morphologic and molecular subtypes. Type I tumors develop from benign extraovarian lesions that implant on the ovary and which can subsequently undergo malignant transformation, whereas many type II carcinomas develop from intraepithelial carcinomas in the fallopian tube and, as a result, disseminate as carcinomas that involve the ovary and extraovarian sites, which probably accounts for their clinically aggressive behavior. The new molecular genetic data, especially those derived from next-generation sequencing, further underline the heterogeneity of ovarian cancer and identify actionable mutations. The dualistic model highlights these differences between type I and type II tumors which, it can be argued, describe entirely different groups of diseases.

Low-grade serous ovarian cancer: A review

Epithelial ovarian cancers can be divided into the more common, aggressive type II cancers and the less common, slow-growing type I cancers. Under this model, serous ovarian carcinomas can be subdivided into high-grade (type II) and low-grade (type I) tumours. The two-tier system for grading serous ovarian carcinomas is superior to more detailed grading systems in terms of predicting survival. Low-grade serous carcinomas typically present in young women and have a relatively good prognosis, despite being resistant to chemotherapy. Low-grade serous cancers have a high prevalence of KRAS and BRAF mutations, but a low prevalence of TP53 mutations (which are characteristic of high-grade serous cancers). Among women with low-grade serous ovarian cancer, the presence of a KRAS/BRAF mutation is a favorable prognostic factor. Studies of the mitogen-activated protein kinase (MAPK) inhibitor in low-grade serous ovarian cancer suggest that identifying MAPK mutations might eventually be useful in guiding treatment.

Genetic and molecular changes in ovarian cancer

Epithelial ovarian cancer represents the most lethal gynecological malignancy in the developed world, and can be divided into five main histological subtypes: high grade serous, endometrioid, clear cell, mucinous and low grade serous. These subtypes represent distinct disease entities, both clinically and at the molecular level. Molecular analysis has revealed significant genetic heterogeneity in ovarian cancer, particularly within the high grade serous subtype. As such, this subtype has been the focus of much research effort to date, revealing molecular subgroups at both the genomic and transcriptomic level that have clinical implications. However, stratification of ovarian cancer patients based on the underlying biology of their disease remains in its infancy. Here, we summarize the molecular changes that characterize the five main ovarian cancer subtypes, highlight potential opportunities for targeted therapeutic intervention and outline priorities for future research.

Diagnostic potential of tumor DNA from ovarian cyst fluid

We determined whether the mutations found in ovarian cancers could be identified in the patients' ovarian cyst fluids. Tumor-specific mutations were detectable in the cyst fluids of 19 of 23 (83%) borderline tumors, 10 of 13 (77%) type I cancers, and 18 of 18 (100%) type II cancers. In contrast, no mutations were found in the cyst fluids of 18 patients with benign tumors or non-neoplastic cysts. Though large, prospective studies are needed to demonstrate the safety and clinical utility of this approach, our results suggest that the genetic evaluation of cyst fluids might be able to inform the management of the large number of women with these lesions.

DOI:http://dx.doi.org/10.7554/eLife.15175.001

More than a third of women develop ovarian cysts during their lifetimes. The vast majority of these cysts are harmless, but a small number are caused by ovarian cancers. These cancers often produce no symptoms until the disease has spread throughout the abdomen or to other organs, so many women go undiagnosed until their chances of being successfully treated are low. Currently, there is no reliable way to determine whether an ovarian cyst is cancerous without performing surgery. As a result, many women undergo unnecessary, invasive surgeries for harmless ovarian cysts.

Tumors shed cells and cell fragments into any fluid that surrounds them. Fluids from cysts in the pancreas, kidney, and thyroid are routinely examined to identify whether they contain cancerous cells. Now, Wang, Sundfeldt et al. show that ovarian cancers also shed DNA into the surrounding cyst fluid. Furthermore, mutations found in this DNA can provide valuable information about whether the cysts are cancerous.

The study was performed by extracting DNA from the fluid in ovarian cysts that had been surgically removed from 77 women. Of these cysts, 10 were harmless cysts, 12 were benign tumors, 31 were invasive cancers, and 24 were so-called borderline tumors, which fall somewhere between the benign tumors and invasive cancers. Only cysts associated with the borderline tumors and invasive cancers need to be surgically removed. Here, Wang, Sundfeldt et al. report that DNA mutations that are characteristic of ovarian cancers were found in 87% of the cysts associated with borderline tumors and invasive cancers. In contrast, these mutations were not found in any of the cysts that do not require surgery.

Fluid can be extracted from an ovarian cyst with a needle during an outpatient visit. Therefore, the results presented by Wang, Sundfeldt et al. suggest a relatively straightforward way of testing the DNA from ovarian cysts before deciding whether surgery is really necessary. First, however, larger studies that follow women with cysts over time will be necessary to confirm that this type of testing is effective and safe.

DOI:http://dx.doi.org/10.7554/eLife.15175.002

KRAS/BRAF Analysis in Ovarian Low-Grade Serous Carcinoma Having Synchronous All Pathological Precursor Regions

Ovarian low-grade serous carcinoma is thought to begin as a serous cystadenoma or adenofibroma that progresses in a slow stepwise fashion. Among the low-grade serous carcinomas, there is a high frequency of activating mutations in the KRAS or BRAF genes; however, it remains unclear as to how these mutations contribute to tumor progression. This is the first report to track the histopathological progression of serous adenofibroma to low-grade serous carcinoma. Each stage was individually analyzed by pathological and molecular genetic methods to determine what differences occur between the distinct stages of progression.

Rational selection of biomarker driven therapies for gynecologic cancers: The more we know, the more we know we don't know

Precision medicine is a rapidly evolving area in the treatment of gynecologic malignancies. Advances in sequencing technology have resulted in an increasing wealth of data regarding the genomic characteristics of ovarian, endometrial, and cervical cancers. These vast new datasets of information have led to novel insights into potential vulnerabilities and therapeutic targets for these cancers. However, unraveling the complex molecular changes within cancer cells to determine how best to attack these targets and to identify effective biomarkers of response remains a significant challenge. In this article, we review the current status of biomarker-driven targeted therapy in gynecologic malignancies.

The Dualistic Model of Ovarian Carcinogenesis: Revisited, Revised, and Expanded

Since our proposal of a dualistic model of epithelial ovarian carcinogenesis more than a decade ago, a large number of molecular and histopathologic studies were published that have provided important insights into the origin and molecular pathogenesis of this disease. This has required that the original model be revised and expanded to incorporate these findings. The new model divides type I tumors into three groups: i) endometriosis-related tumors that include endometrioid, clear cell, and seromucinous carcinomas; ii) low-grade serous carcinomas; and iii) mucinous carcinomas and malignant Brenner tumors. As in the previous model, type II tumors are composed, for the most part, of high-grade serous carcinomas that can be further subdivided into morphologic and molecular subtypes. Type I tumors develop from benign extraovarian lesions that implant on the ovary and which can subsequently undergo malignant transformation, whereas many type II carcinomas develop from intraepithelial carcinomas in the fallopian tube and, as a result, disseminate as carcinomas that involve the ovary and extraovarian sites, which probably accounts for their clinically aggressive behavior. The new molecular genetic data, especially those derived from next-generation sequencing, further underline the heterogeneity of ovarian cancer and identify actionable mutations. The dualistic model highlights these differences between type I and type II tumors which, it can be argued, describe entirely different groups of diseases.

The Dualistic Model of Ovarian Carcinogenesis: Revisited, Revised, and Expanded

Since our proposal of a dualistic model of epithelial ovarian carcinogenesis more than a decade ago, a large number of molecular and histopathologic studies were published that have provided important insights into the origin and molecular pathogenesis of this disease. This has required that the original model be revised and expanded to incorporate these findings. The new model divides type I tumors into three groups: i) endometriosis-related tumors that include endometrioid, clear cell, and seromucinous carcinomas; ii) low-grade serous carcinomas; and iii) mucinous carcinomas and malignant Brenner tumors. As in the previous model, type II tumors are composed, for the most part, of high-grade serous carcinomas that can be further subdivided into morphologic and molecular subtypes. Type I tumors develop from benign extraovarian lesions that implant on the ovary and which can subsequently undergo malignant transformation, whereas many type II carcinomas develop from intraepithelial carcinomas in the fallopian tube and, as a result, disseminate as carcinomas that involve the ovary and extraovarian sites, which probably accounts for their clinically aggressive behavior. The new molecular genetic data, especially those derived from next-generation sequencing, further underline the heterogeneity of ovarian cancer and identify actionable mutations. The dualistic model highlights these differences between type I and type II tumors which, it can be argued, describe entirely different groups of diseases.

The status of epidermal growth factor receptor in borderline ovarian tumours

The majority of borderline ovarian tumours (BOTs) behave in a benign fashion, but some may show aggressive behavior. The reason behind this has not been elucidated. The epidermal growth factor receptor (EGFR) is known to contribute to cell survival signals as well as metastatic potential of some tumours. EGFR expression and gene status have not been thoroughly investigated in BOTs as it has in ovarian carcinomas. In this study we explore protein expression as well as gene mutations and amplifications of EGFR in BOTs in comparison to a subset of other epithelial ovarian tumours. We studied 85 tumours, including 61 BOTs, 10 low grade serous carcinomas (LGSCs), 9 high grade serous carcinomas (HGSCs) and 5 benign epithelial tumours. EGFR protein expression was studied using immunohistochemistry. Mutations were investigated by Sanger sequencing exons 18-21 of the tyrosine kinase domain of EGFR. Cases with comparatively higher protein expression were examined for gene amplification by chromogenic in situ hybridization. We also studied the tumours for KRAS and BRAF mutations. Immunohistochemistry results revealed both cytoplasmic and nuclear EGFR expression with variable degrees between tumours. The level of nuclear localization was relatively higher in BOTs and LGSCs as compared to HGSCs or benign tumours. The degree of nuclear expression of BOTs showed no significant difference from that in LGSCs (mean ranks 36.48, 33.05, respectively, p=0.625), but was significantly higher than in HGSCs (mean ranks: 38.88, 12.61 respectively, p< 0.001) and benign tumours (mean ranks: 35.18, 13.00 respectively, p= 0.010). Cytoplasmic expression level was higher in LGSCs. No EGFR gene mutations or amplification were identified, yet different polymorphisms were detected. Five different types of point mutations in the KRAS gene and the V600E BRAF mutation were detected exclusively in BOTs and LGSCs. Our study reports for the first time nuclear localization of EGFR in BOTs. The nuclear localization similarities between BOTs and LGSCs and not HGSCs support the hypothesis suggesting evolution of LGSCs from BOTs. We also confirm that EGFR mutations and amplifications are not molecular events in the pathogenesis of BOTs.

Morphologic and Molecular Characteristics of Mixed Epithelial Ovarian Cancers

Epithelial ovarian cancer (EOC) consists of 5 major histotypes: high-grade serous carcinoma (HGSC), endometrioid carcinoma (EC), clear cell carcinoma (CCC), mucinous carcinoma (MC), and low-grade serous carcinoma (LGSC). Each can have a broad spectrum of morphologic appearances, and 1 histotype can closely mimic histopathologic features more typical of another. Historically, there has been a relatively high frequency of mixed, defined by 2 or more distinct histotypes present on the basis of routine histopathologic assessment, histotype carcinoma diagnoses (3% to 11%); however, recent immunohistochemical (IHC) studies identifying histotype-specific markers and allowing more refined histotype diagnoses suggest a much lower incidence. We reviewed hematoxylin and eosin-stained slides from 871 cases of EOC and found the frequency of mixed carcinomas to be 1.7% when modern diagnostic criteria are applied. Through international collaboration, we established a cohort totaling 22 mixed EOCs, consisting of 9 EC/CCC, 4 EC/LGSC, 3 HGSC/CCC, 2 CCC/MC, and 4 other combinations. We interrogated the molecular differences between the different components of each case using IHC, gene expression, and hotspot sequencing analyses. IHC data alone suggested that 9 of the 22 cases were not mixed tumors, as they presented a uniform immuno-phenotype throughout, and these cases most probably represent morphologic mimicry and variation within tumors of a single histotype. Synthesis of molecular data further reduces the incidence of mixed carcinomas. On the basis of these results, true mixed carcinomas with both morphologic and molecular support for the presence of >1 histotype within a given tumor represent <1% of EOCs.

Paradigm Shift in the Management Strategy for Epithelial Ovarian Cancer

The hypothesis on the pathogenesis of epithelial ovarian cancer continues to evolve. Although epithelial ovarian cancer had been assumed to arise from the coelomic epithelium of the ovarian surface, it is now becoming clearer that the majority of serous carcinomas arise from epithelium of the distal fallopian tube, whereas clear cell and endometrioid cancers arise from endometriosis. Molecular and genomic characteristics of epithelial ovarian cancer have been extensively investigated. Our understanding of pathogenesis of the various histologic types of ovarian cancer have begun to inform changes to the strategies for management of epithelial ovarian cancer, which represent a paradigm shift not only for treatment but also for prevention, which previously had not been considered achievable. In this article, we will discuss novel attempts at the prevention of high-grade serous ovarian cancer and treatment strategies for two distinct entities in epithelial ovarian cancer: low-grade serous and clear cell ovarian carcinomas, which are relatively rare and resistant to conventional chemotherapy.

Impact of mutational status on survival in low-grade serous carcinoma of the ovary or peritoneum

BACKGROUND

Low-grade serous carcinoma of the ovary or peritoneum is a distinct, well- recognized histologic subtype characterized by young age at diagnosis, relative chemoresistance, and prolonged overall survival. Common mutations reported to be found within this subtype include KRAS and BRAF.

METHODS

Using clinical information of patients from our IRB-approved registry and tissue from a subset of these patients, we performed mutational analysis for KRAS and BRAF using the direct Sanger sequencing technique and correlated findings with the clinical outcome, overall survival (OS).

RESULTS

In 79 cases, patients with KRAS or BRAF mutations (n=21) had a significantly better OS than those with wild-type KRAS or BRAF (n=58) (106.7 months (95% CI, 50.6, 162.9) vs 66.8 months (95% CI, 43.6, 90.0)), respectively (P=0.018).

CONCLUSIONS

Mutational status appears to be a potential prognostic factor in low-grade serous carcinoma of the ovary or peritoneum.

Extreme Outlier Analysis Identifies Occult Mitogen-Activated Protein Kinase Pathway Mutations in Patients With Low-Grade Serous Ovarian Cancer

PURPOSE

No effective systemic therapy exists for patients with metastatic low-grade serous (LGS) ovarian cancers. BRAF and KRAS mutations are common in serous borderline (SB) and LGS ovarian cancers, and MEK inhibition has been shown to induce tumor regression in a minority of patients; however, no correlation has been observed between mutation status and clinical response. With the goal of identifying biomarkers of sensitivity to MEK inhibitor treatment, we performed an outlier analysis of a patient who experienced a complete, durable, and ongoing (> 5 years) response to selumetinib, a non-ATP competitive MEK inhibitor.

PATIENTS AND METHODS

Next-generation sequencing was used to analyze this patient's tumor as well as an additional 28 SB/LGS tumors. Functional characterization of an identified novel alteration of interest was performed.

RESULTS

Analysis of the extraordinary responder's tumor identified a 15-nucleotide deletion in the negative regulatory helix of the MAP2K1 gene encoding for MEK1. Functional characterization demonstrated that this mutant induced extracellular signal-regulated kinase pathway activation, promoted anchorage-independent growth and tumor formation in mice, and retained sensitivity to selumetinib. Analysis of additional LGS/SB tumors identified mutations predicted to induce extracellular signal-regulated kinase pathway activation in 82% (23 of 28), including two patients with BRAF fusions, one of whom achieved an ongoing complete response to MEK inhibitor-based combination therapy.

CONCLUSION

Alterations affecting the mitogen-activated protein kinase pathway are present in the majority of patients with LGS ovarian cancer. Next-generation sequencing analysis revealed deletions and fusions that are not detected by older sequencing approaches. These findings, coupled with the observation that a subset of patients with recurrent LGS ovarian cancer experienced dramatic and durable responses to MEK inhibitor therapy, support additional clinical studies of MEK inhibitors in this disease.

Successful use of next generation genomic sequencing (NGS)-directed therapy of clear cell carcinoma of the ovary (CCCO) with trametinib and metformin in a patient with chemotherapy-refractory disease

Purpose

Compared to other subtypes of epithelial ovarian cancer, clear cell carcinoma of the ovary bears an ominous reputation for chemotherapy resistance, increased relapse rate, and diminished survival. Among patients with distinct histopathologic subtypes, molecular analyses have identified a variety of known drivers of the malignant behavior, and depict a striking heterogeneity.

Methods

A patient with rapidly metastatic CCCO that was refractory to taxane, platinum, pemetrexed, and bevacizumab-based strategies underwent molecular profiling which disclosed dual MAPK and PI3K/AKT/mTOR pathway mutations.

Results

Combined targeted therapy with trametinib and metformin resulted in a dramatic disease regression without toxicity.

Conclusion

The case highlights the utility of precision medicine combining individual molecular diagnosis with rational therapeutic intervention with targeted agents.

Nutlin-3a: A Potential Therapeutic Opportunity for TP53 Wild-Type Ovarian Carcinomas

Epithelial ovarian cancer is a diverse molecular and clinical disease, yet standard treatment is the same for all subtypes. TP53 mutations represent a node of divergence in epithelial ovarian cancer histologic subtypes and may represent a therapeutic opportunity in subtypes expressing wild type, including most low-grade ovarian serous carcinomas, ovarian clear cell carcinomas and ovarian endometrioid carcinomas, which represent approximately 25% of all epithelial ovarian cancer. We therefore sought to investigate Nutlin-3a--a therapeutic which inhibits MDM2, activates wild-type p53, and induces apoptosis--as a therapeutic compound for TP53 wild-type ovarian carcinomas. Fifteen epithelial ovarian cancer cell lines of varying histologic subtypes were treated with Nutlin-3a with determination of IC50 values. Western Blot (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) analyses quantified MDM2, p53, and p21 expression after Nutlin-3a treatment. DNA from 15 cell lines was then sequenced for TP53 mutations in exons 2-11 including intron-exon boundaries. Responses to Nutlin-3a were dependent upon TP53 mutation status. By qRT-PCR and WB, levels of MDM2 and p21 were upregulated in wild-type TP53 sensitive cell lines, and p21 induction was reduced or absent in mutant cell lines. Annexin V assays demonstrated apoptosis in sensitive cell lines treated with Nutlin-3a. Thus, Nutlin-3a could be a potential therapeutic agent for ovarian carcinomas expressing wild-type TP53 and warrants further investigation.

Impact of Age and Primary Disease Site on Outcome in Women With Low-Grade Serous Carcinoma of the Ovary or Peritoneum: Results of a Large Single-Institution Registry of a Rare Tumor

PURPOSE

Low-grade serous carcinoma of the ovary (LGSOC) or peritoneum (LGSPC) is a rare subtype of ovarian or peritoneal cancer characterized by young age at diagnosis and relative resistance to chemotherapy. The purpose of this study is to report our updated experience with women diagnosed with LGSOC or LGSPC to assess the validity of our original observations.

PATIENTS AND METHODS

Eligibility criteria for patients from our database were: stage I to IV LGSOC or LGSPC, original diagnosis before January 2012, and adequate clinical information. All patients were included in progression-free survival, overall survival, and multivariable Cox regression analyses. A subset analysis was performed among patients with stage II to IV low-grade serous carcinoma treated with primary surgery followed by platinum-based chemotherapy.

RESULTS

We identified 350 eligible patients. Median progression-free survival was 28.1 months; median overall survival was 101.7 months. In the multivariable analysis, compared with women age ≤ 35 years, those diagnosed at age > 35 years had a 43% reduction in likelihood of dying (hazard ratio, 0.53; 95% CI, 0.37 to 0.74; P < .001). Having disease present at completion of primary therapy was associated with a 1.78 increased hazard of dying compared with being clinically disease free (P < .001). Similar trends were noted in the smaller patient cohort. In this cohort, women with LGSPC had a 41% decreased chance of dying (hazard ratio, 0.59; 95% CI, 0.36 to 0.98; P = .04) compared with those with LGSOC.

CONCLUSION

Women age < 35 years with low-grade serous carcinoma and those with persistent disease at completion of primary therapy have the worst outcomes. Patients with LGSPC seem to have a better prognosis than those with LGSOC.

RASAL2 down-regulation in ovarian cancer promotes epithelial-mesenchymal transition and metastasis

Ovarian cancer is the most lethal gynecologic malignancy, and transcoelomic metastasis is responsible for the greatest disease mortality. Although intensive efforts have been made, the mechanism behind this process remains unclear. RASAL2 is a GTPase activating proteins (GAPs) which was recently reported as a tumor suppressor in breast cancer. In this study, we identified RASAL2 as a regulator of epithelial-mesenchymal transition (EMT) and metastasis in ovarian cancer. RASAL2 was down-regulated in ovarian cancer samples compared with normal tissue samples, especially in advanced stages and grades. RASAL2 knockdown in ovarian cancer cell lines promoted in vitro anchorage-independent growth, cell migration and invasion and in vivo tumor formation. Moreover, we observed EMT in RASAL2-depleted cells. E-cadherin-mediated cell-cell adhesion was attenuated, and mesenchymal markers were up-regulated. Further investigation revealed that the oncogenic role of RASAL2 down-regulation was mediated by the Ras-ERK pathway. RASAL2 knockdown activated the Ras-ERK pathway, and inhibition of the pathway reversed the functional effects of RASAL2 depletion. Together, our results implicate RASAL2 as an EMT regulator and tumor suppressor in ovarian cancer, and down-regulation of RASAL2 promotes ovarian cancer progression.

Updates and emerging therapies for rare epithelial ovarian cancers: one size no longer fits all

Epithelial ovarian carcinoma consists of not one, but several, entities. A number of subtypes exist, including high-grade and low-grade serous carcinomas, clear cell, endometrioid carcinoma and mucinous carcinoma. Historically, women with epithelial ovarian cancer have been treated similarly and "lumped" in the same cooperative group treatment trials, irrespective of their tumor subtype. Recently, however, differences in epidemiology, tumor biology, tumor marker expression and treatment responses have been elucidated among the histologic subtypes, with a clear distinction emerging between the Type I, lower grade tumors and Type 2, higher grade epithelial malignancies. A mounting body of research demonstrates that a "one-size-fits-all" treatment approach to epithelial ovarian tumors is no longer relevant, especially for the Type I subtypes. Indeed, with the exception of high-grade serous carcinoma, most other epithelial subtypes exhibit some degree of chemotherapy resistance, rendering treatment problematic, especially in the setting of advanced disease. This review summarizes the genetic, molecular, and clinical differences of the more rare, but clinically important, Type I epithelial ovarian tumors. Additionally, a critical appraisal of both historical and contemporary treatment approaches and the rationale for targeted therapies are emphasized.

Ovarian cancer risk after salpingectomy: a nationwide population-based study

BACKGROUND

Recent genetic and morphologic studies have challenged the traditional view on the pathogenesis of ovarian cancer; suggesting that ovarian cancer predominantly arises within the fallopian tubes or the uterus. We hypothesize that surgical removal of the fallopian tubes is associated with a reduced risk for ovarian cancer.

METHODS

In this population-based cohort study, we used data on women with previous surgery on benign indication (sterilization, salpingectomy, hysterectomy, and bilateral salpingo-oophorectomy [BSO], hysterectomy; n = 251465) compared with the unexposed population (n = 5449119) between 1973 and 2009 and analyzed with Cox regression models. The effects of one- and two-sided salpingectomy were considered in a subanalysis. All statistical tests were two-sided.

RESULTS

There was a statistically significantly lower risk for ovarian cancer among women with previous salpingectomy (HR = 0.65, 95% CI = 0.52 to 0.81) when compared with the unexposed population. In addition, statistically significant risk reductions were observed among women with previous hysterectomy (HR = 0.79, 95% CI = 0.70 to 0.88), sterilization (HR = 0.72, 95% CI = 0.64 to 0.81), and hysterectomy with BSO (HR = 0.06, 95% CI = 0.03 to 0.12). Bilateral salpingectomy was associated with a 50% decrease in risk of ovarian cancer compared with the unilateral procedure (HR = 0.35, 95% CI = 0.17 to 0.73, and 0.71, 95% CI = 0.56 to 0.91, respectively).

CONCLUSION

Salpingectomy on benign indication is associated with reduced risk of ovarian cancer. These data support the hypothesis that a substantial fraction of ovarian cancer arises in the fallopian tube. Our results suggest that removal of the fallopian tubes by itself, or concomitantly with other benign surgery, is an effective measure to reduce ovarian cancer risk in the general population.

Low Grade Serous Ovarian Carcinoma: from the molecular characterization to the best therapeutic strategy

Low Grade Serous Ovarian Carcinoma, LGSOC, is certainly a rare disease, accounting for only a small proportion of all ovarian carcinomas, nevertheless in the last decade we have acquired many data about its molecular and clinical features and it has been largely accepted that it has distinct pathogenesis, genetic aberrations and clinical behavior compared to High Grade Serous Ovarian Carcinoma, HGSOC, which is the most common ovarian cancer histotype. A large number of series pointed out the high rate of KRAS and BRAF mutations in LGSOCs and Serous Borderline Tumors, SBLTs, in contrast with their rarity in HGSOC. Such finding, together with the recurrent observation of focus of LGSOC associated with areas of SBLT in the same lesion, led to abandon the traditional histology classification, defining three types of serous carcinomas, in favor of a new dualistic grading system which recognizes only LG and HG carcinomas corresponding to distinct tumorigenesis pathways, the former based on KRAS/BRAF mutations and alteration of the MAP/ERK signaling, the latter characterized by early genetic instability and wild type status of KRAS and BRAF. LGSOC shows favorable overall survival, compared to general ovarian cancer population, but worrying resistance to conventional treatments. MEK inhibitors are emerging as active agents and may well represent an effective therapeutic strategy in the near future.

Intratumoral heterogeneity in a minority of ovarian low-grade serous carcinomas

Background

Ovarian low-grade serous carcinoma (LGSC) has fewer mutations than ovarian high-grade serous carcinoma (HGSC) and a less aggressive clinical course. However, an overwhelming majority of LGSC patients do not respond to conventional chemotherapy resulting in a poor long-term prognosis comparable to women diagnosed with HGSC. KRAS and BRAF mutations are common in LGSC, leading to clinical trials targeting the MAPK pathway. We assessed the stability of targetable somatic mutations over space and/or time in LGSC, with a view to inform stratified treatment strategies and clinical trial design.

Methods

Eleven LGSC cases with primary and recurrent paired samples were identified (stage IIB-IV). Tumor DNA was isolated from 1–4 formalin-fixed paraffin-embedded tumor blocks from both the primary and recurrence (n = 37 tumor and n = 7 normal samples). Mutational analysis was performed using the Ion Torrent AmpliSeq^TM Cancer Panel, with targeted validation using Fluidigm-MiSeq, Sanger sequencing and/or Raindance Raindrop digital PCR.

Results

KRAS (3/11), BRAF (2/11) and/or NRAS (1/11) mutations were identified in five unique cases. A novel, non-synonymous mutation in SMAD4 was observed in one case. No somatic mutations were detected in the remaining six cases. In two cases with a single matched primary and recurrent sample, two KRAS hotspot mutations (G12V, G12R) were both stable over time. In three cases with multiple samplings from both the primary and recurrent surgery some mutations (NRAS Q61R, BRAF V600E, SMAD4 R361G) were stable across all samples, while others (KRAS G12V, BRAF G469V) were unstable.

Conclusions

Overall, the majority of cases with detectable somatic mutations showed mutational stability over space and time while one of five cases showed both temporal and spatial mutational instability in presumed drivers of disease. Investigation of additional cases is required to confirm whether mutational heterogeneity in a minority of LGSC is a general phenomenon that should be factored into the design of clinical trials and stratified treatment for this patient population.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-982) contains supplementary material, which is available to authorized users.

A peculiar mutation spectrum emerging from young peruvian patients with hepatocellular carcinoma

Hepatocellular carcinoma usually afflicts individuals in their later years following longstanding liver disease. In Peru, hepatocellular carcinoma exists in a unique clinical presentation, which affects patients around age 25 with a normal, healthy liver. In order to deepen our understanding of the molecular processes ongoing in Peruvian liver tumors, mutation spectrum analysis was carried out on hepatocellular carcinomas from 80 Peruvian patients. Sequencing analysis focused on nine genes typically altered during liver carcinogenesis, i.e. ARID2, AXIN1, BRAF, CTNNB1, NFE2L2, H/K/N-RAS, and TP53. We also assessed the transcription level of factors involved in the control of the alpha-fetoprotein expression and the Hippo signaling pathway that controls contact inhibition in metazoans. The mutation spectrum of Peruvian patients was unique with a major class of alterations represented by Insertions/Deletions. There were no changes at hepatocellular carcinoma-associated mutation hotspots in more than half of the specimens analyzed. Furthermore, our findings support the theory of a consistent collapse in the Hippo axis, as well as an expression of the stemness factor NANOG in high alpha-fetoprotein-expressing hepatocellular carcinomas. These results confirm the specificity of Peruvian hepatocellular carcinoma at the molecular genetic level. The present study emphasizes the necessity to widen cancer research to include historically neglected patients from South America, and more broadly the Global South, where cancer genetics and tumor presentation are divergent from canonical neoplasms.

Molecular characterization of serous ovarian carcinoma using a multigene next generation sequencing cancer panel approach

BACKGROUND

High grade serous ovarian cancer is one of the poorly characterized malignancies. This study aimed to elucidate the mutational events in Malaysian patients with high grade serous ovarian cancer by performing targeted sequencing on 50 cancer hotspot genes.

RESULTS

Nine high grade serous ovarian carcinoma samples and ten normal ovarian tissues were obtained from Universiti Kebangsaan Malaysia Medical Center (UKMMC) and the Kajang Hospital. The Ion AmpliSeq™ Cancer Hotspot Panel v2 targeting "mutation-hotspot region" in 50 most common cancer-associated genes was utilized. A total of 20 variants were identified in 12 genes. Eleven (55%) were silent alterations and nine (45%) were missense mutations. Six of the nine missense mutations were predicted to be deleterious while the other three have low or neutral protein impact. Eight genes were altered in both the tumor and normal groups (APC, EGFR, FGFR3, KDR, MET, PDGFRA, RET and SMO) while four genes (TP53, PIK3CA, STK11 and KIT) were exclusively altered in the tumor group. TP53 alterations were present in all the tumors but not in the normal group. Six deleterious mutations in TP53 (p.R175H, p.H193R, p.Y220C, p.Y163C, p.R282G and p.Y234H) were identified in eight serous ovarian carcinoma samples and none in the normal group.

CONCLUSION

TP53 remains as the most frequently altered gene in high grade serous ovarian cancer and Ion Torrent Personal Genome Machine (PGM) in combination with Ion Ampliseq™ Cancer Hotspot Panel v2 were proven to be instrumental in identifying a wide range of genetic alterations simultaneously from a minute amount of DNA. However, larger series of validation targeting more genes are necessary in order to shed a light on the molecular events underlying pathogenesis of this cancer.

Mutational status of KRAS, NRAS, and BRAF in primary clear cell ovarian carcinoma

Ovarian clear cell carcinoma (OCCC) is a subtype of epithelial ovarian cancer with characteristic biological features and aggressive clinical behavior. OCCCs show a pattern of gene mutations different from other type I ovarian malignancies, notably a higher frequency of PIK3CA mutations. In low grade serous ovarian cancer, KRAS and BRAF mutations are frequent, but little data are available on the mutational status of these genes in OCCCs. To clarify this issue, we designed a clinicopathological study with the aim to establish the incidence of KRAS, NRAS, and BRAF hot spot mutations in OCCC. Between December 2006 and June 2012, 22 patients with a proven diagnosis of OCCC were admitted to our Institutions. In all cases, final diagnosis was established according to FIGO and WHO criteria. All women received complete surgical staging. The PyroMark Q24 system (Qiagen GmbH, Hilden, Germany) was used for pyrosequencing analysis of KRAS, NRAS, and BRAF hot spot regions on 2.5-μm sections of formalin-fixed paraffin-embedded tissue from primary OCCC. Pyrosequencing analysis of KRAS, NRAS, and BRAF hot spot regions revealed the presence of mutations only at codon 12 in exon 2 of KRAS in 3 of 22 (14 %) cases. We found no mutations in the hot spot regions of NRAF (exons 2, 3, 4) or BRAF (exon 15). The median age of women with a KRAS mutated OCCC was 74 years. These OCCC were unilateral FIGO stage IA lesions in two cases associated with foci of endometriosis. We conclude that in 14 % of OCCCs, a KRAS mutation occurs in codon 2 exon 2. NRAS and BRAF mutations were not found.

Genomic profile of ovarian carcinomas

Background

It is known that all tumors studied in sufficient number to draw conclusions show characteristic/specific chromosomal rearrangements, and the identification of these chromosomes and the genes rearranged behind the aberrations may ultimately lead to a tailor-made therapy for each cancer patient. Knowledge about the acquired genomic aberrations of ovarian carcinomas is still unsatisfactory.

Methods

We cytogenetically analyzed 110 new cases of ovarian carcinoma of different histological subtypes using karyotyping of G-banded chromosomes and high-resolution comparative genomic hybridization. We first compared the aberration patterns identified by the two genomic screening techniques using the so-called “classical” pathological classification in which the carcinomas are grouped as tumors of types I and II. We also broke down our findings according to the more “modern” classification which groups the carcinomas in five different categories.

Results

The chromosomal breakpoints identified by karyotyping tended to cluster to 19p/q and to 11q, but no unquestionably recurrent rearrangement could be seen. Common imbalances were scored as gains from 1q, 3q, 7q, and 8q and losses from 17p, 19q, and 22q. Gain of material from 8q23 and losses from 19q and 22q have previously been described at high frequencies in bilateral and borderline ovarian carcinomas. The fact that they were present both in “precursor” lesions, i.e., borderline tumors, as well as in tumors of more advanced stages, i.e., carcinomas, highlights the possibility of an adenoma-carcinoma sequence in ovarian carcinogenesis.

Conclusion

Based on the relatively simple genomic changes we identified in the low-grade serous carcinomas examined (n = 7) and which largely corresponded to the aberration pattern formerly identified in borderline tumors, one can interpret the cytogenetic data as supporting the view that the low-grade carcinomas represent a phenotypically more advanced stage of borderline tumors. Whether transition from low-grade to high-grade carcinoma also occurs, is a question about which the genomic data is still inconclusive.