Is early detection of ovarian cancer possible?

Relative Ratios Enhance the Diagnostic Power of Phospholipids in Distinguishing Benign and Cancerous Ovarian Masses

Ovarian cancer remains a highly lethal disease due to its late clinical presentation and lack of reliable early biomarkers. Protein-based diagnostic markers have presented limitations in identifying ovarian cancer. We tested the potential of phospholipids as markers of ovarian cancer by utilizing inter-related regulation of phospholipids, a unique property that allows the use of ratios between phospholipid species for quantitation. High-performance liquid chromatography mass spectrometry was used to measure phospholipid, lysophospholipid, and sphingophospholipid content in plasma from patients with benign ovarian masses, patients with ovarian cancer, and controls. We applied both absolute and relative phospholipid ratios for quantitation. Receiver operating characteristic analysis was performed to test the sensitivity and specificity. We found that utilization of ratios between phospholipid species greatly outperformed absolute quantitation in the identification of ovarian cancer. Of the phospholipids analyzed, species in phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and sphingomyelin (SM) were found to have great biomarker potential. LPC(20:4)/LPC(18:0) carried the greatest capacity to differentiate cancer from control, SM(d18:1/24:1)/SM(d18:1/22:0) to differentiate benign from cancer, and PC(18:0/20:4)/PC(18:0/18:1) to differentiate benign from control. These results demonstrate the potential of plasma phospholipids as a novel marker of ovarian cancer by utilizing the unique characteristics of phospholipids to further enhance the diagnostic power.

Challenges and Inconsistencies in Using Lysophosphatidic Acid as a Biomarker for Ovarian Cancer

Increased detection of plasma lysophosphatidic acid (LPA) has been proposed as a potential diagnostic biomarker in ovarian cancer, but inconsistency exists in these reports. It has been shown that LPA can undergo an artificial increase during sample processing and analysis, which has not been accounted for in ovarian cancer research. The aim of this study is to provide a potential explanation about how the artificial increase in LPA may have interfered with previous LPA analysis in ovarian cancer research. Using an established LC-MS method, we measured LPA and other lysophospholipid levels in plasma obtained from three cohorts of patients: non-cancer controls, patients with benign ovarian tumors, and those with ovarian cancer. We did not find the LPA level to be higher in cancer samples. To understand this inconsistency, we observed that LPA content changed more significantly than other lysophospholipids as a function of plasma storage time while frozen. Additionally, only LPA was found to be adversely impacted by incubation time depending on the Ethylenediaminetetraacetic acid (EDTA) concentration used during blood drawing. We also show that the inhibition of autotaxin effectively prevented artificial LPA generation during incubation at room temperature. Our data suggests that the artificial changes in LPA content may contribute to the discrepancies reported in literature. Any future studies planning to measure plasma LPA should carefully design the study protocol to consider these confounding factors.

A study of ovarian cancer biomarker amplification using ultrasound for early stage detection

The application of serum biomarker to ovarian tumors for early stage detection and clinical diagnosis is a rapidly expanding research area. The problem with conventional markers is that they are often released too late or at too low a level to be detected in time to trigger effective treatment. Ultrasound has been used to influence bio-effects in living cells, but there is only one reported case of the use of ultrasound to enhance the release of a biomarker (Carcinoembryonic antigen CEA). In this study we report the use of ultrasound to enhance the release of a combination of ovarian cancer biomarkers (CA125 and CA19-9) to help in the diagnosis of ovarian cancer at an early stage. The results indicated that after 5 min sonication at a frequency of 1 MHz and intensity of 0.3 W cm(-2), the CA125 and CA19-9 levels were increased by 2.02 and 4.21-fold respectively. These findings suggest that ultrasonic treatment can be used to enhance the release of serum biomarkers from ovarian tumors.

Identification of five serum protein markers for detection of ovarian cancer by antibody arrays

BACKGROUND

Protein and antibody arrays have emerged as a promising technology to study protein expression and protein function in a high-throughput manner. These arrays also represent a new opportunity to profile protein expression levels in cancer patients' samples and to identify useful biosignatures for clinical diagnosis, disease classification, prediction, drug development and patient care. We applied antibody arrays to discover a panel of proteins which may serve as biomarkers to distinguish between patients with ovarian cancer and normal controls.

METHODOLOGY/PRINCIPAL FINDINGS

Using a case-control study design of 34 ovarian cancer patients and 53 age-matched healthy controls, we profiled the expression levels of 174 proteins using antibody array technology and determined the CA125 level using ELISA. The expression levels of those proteins were analyzed using 3 discriminant methods, including artificial neural network, classification tree and split-point score analysis. A panel of 5 serum protein markers (MSP-alpha, TIMP-4, PDGF-R alpha, and OPG and CA125) was identified, which could effectively detect ovarian cancer with high specificity (95%) and high sensitivity (100%), with AUC =0.98, while CA125 alone had an AUC of 0.87.

CONCLUSIONS/SIGNIFICANCE

Our pilot study has shown the promising set of 5 serum markers for ovarian cancer detection.

Lysophosphatidic acid (LPA)—a perspective marker in ovarian cancer

To compare plasma lysophosphatidic acid (LPA) levels in ovarian cancer patients in women with benign ovarian tumors and in women with no ovarian pathology. We correlated clinico-pathological parameters with plasma LPA levels. Capillary electrophoresis with indirect ultraviolet detection was used to analyze the plasma LPA levels of 159 patients (81 patients with ovarian cancer, 27 women without ovarian or uterine pathologies, and 51 patients with benign ovarian tumors) during a 5-year period. Patients with ovarian cancer had a significantly higher plasma LPA level (n=81; median (med), 11.53 μmol/l; range, 1.78-43.21 μmol/l) compared with controls with no ovarian pathology (n=27; med, 1.86 μmol/l; range, 0.94-9.73 μmol/l), and patients with benign ovarian tumor (n=51; med, 6.17 μmol/l; range, 1.12-25.23 μmol/l; P<0.001). We found that plasma LPA levels were associated with the International Federation of Gynecology and Obstetrics stage. The histological subtype and grade of ovarian cancer did not influence the plasma LPA levels in this study. The plasma LPA level can be a useful marker for ovarian cancer, particularly in the early stages of the disease.

Proteomic contributions to personalized cancer care

Cancer impacts each patient and family differently. Our current understanding of the disease is primarily limited to clinical hallmarks of cancer, but many specific molecular mechanisms remain elusive. Genetic markers can be used to determine predisposition to tumor development, but molecularly targeted treatment strategies that improve patient prognosis are not widely available for most cancers. Individualized care plans, also described as personalized medicine, still must be developed by understanding and implementing basic science research into clinical treatment. Proteomics holds great promise in contributing to the prevention and cure of cancer because it provides unique tools for discovery of biomarkers and therapeutic targets. As such, proteomics can help translate basic science discoveries into the clinical practice of personalized medicine. Here we describe how biological mass spectrometry and proteome analysis interact with other major patient care and research initiatives and present vignettes illustrating efforts in discovery of diagnostic biomarkers for ovarian cancer, development of treatment strategies in lung cancer, and monitoring prognosis and relapse in multiple myeloma patients.

Improved survival in BRCA2 carriers with ovarian cancer

OBJECTIVES

The objective of this study was to investigate survival of ovarian cancer patients with BRCA1 and BRCA2 mutations compared to those without mutations in a population-based sample of incident epithelial ovarian cancer cases.

METHODS

Follow-up for vital status was performed on a population-based sample of 232 women with incident epithelial ovarian cancer recruited between December 13, 2000 and September 30, 2003 in the Tampa Bay area. Survival analysis using Cox regression was performed on (1) all 232 cases and (2) the 209 invasive epithelial ovarian cancer cases. Results of the two analyses were similar, thus data involving the 209 invasive epithelial cancer cases are presented, as this was judged to be more clinically relevant.

RESULTS

In the multivariate analysis, BRCA status and stage were statistically significant, and were adjusted for in the survival analysis model. The Kaplan-Meier method estimated expected survival at 4 years of 83% of BRCA2 carriers compared to 37% of BRCA1 carriers and 12% of non-carriers. There was a statistically significant difference between BRCA2 carriers and non-carriers (p = 0.013). No statistically significant survival differences were seen for BRCA1 carriers when compared with either BRCA2 carriers or non-carriers.

CONCLUSION

These data suggest that BRCA2 mutation carriers with ovarian cancer may have better survival than BRCA1 carriers and non-carriers. The etiology of this possible survival advantage is currently unknown. Larger studies are needed to confirm these results and to clarify their etiology and clinical significance.

Current management strategies for ovarian cancer

Epithelial ovarian cancer originates in the layer of cells that covers the surface of the ovaries. The disease spreads readily throughout the peritoneal cavity and to the lymphatics, often before causing symptoms. Of the cancers unique to women, ovarian cancer has the highest mortality rate. Most women are diagnosed as having advanced stage disease, and efforts to develop new screening approaches for ovarian cancer are a high priority. Optimal treatment of ovarian cancer begins with optimal cytoreductive surgery followed by combination chemotherapy. Ovarian cancer, even in advanced stages, is sensitive to a variety of chemotherapeutics. Although improved chemotherapy has increased 5-year survival rates, overall survival gains have been limited because of our inability to eradicate all disease. Technologic advances that allow us to examine the molecular machinery that drives ovarian cancer cells have helped to identify numerous therapeutic targets within these cells. In this review, we provide an overview of ovarian cancer with particular emphasis on recent advances in operative management and systemic therapies.

Preoperative diagnosis of ovarian tumors, focusing on the solid area based on diagnostic imaging

AIM

The objectives were to attempt to differentiate between benignancy and malignancy by focusing not on macroscopic finding of tumor sections, but on the solid areas by diagnostic imaging. To investigate the usefulness of diagnostic imaging for ovarian tumors, we examined the solid areas in the tumor and their shape and analyzed the relationship between these factors and the malignant potential.

METHODS

Subjects were 921 surgical cases (1074 tumors) over a period of 7 years. Diagnostic images (ultrasonography, computed tomography and magnetic resonance imaging) were reread, focusing on the solid area. Tumors were classified into four groups according to the prominence of the solid area, and the findings were compared with the postoperative diagnosis.

RESULTS

Of the cases, 718 indicated benign, borderline malignancy in 29 and malignancy in 174. The malignant potential of tumors with solid areas was significantly higher than those with no solid area. However, upon comparison among the different groups with solid areas, no significant differences were detected in terms of the frequency at which malignancies were detected, despite the differences between the groups with respect to size and shape.

CONCLUSION

It is important for the treatment strategy that solid areas, even if small, should not be neglected, and that malignancies are found at high frequency regardless of shape, size and prominence.

Characterisation of human kallikrein 6/protease M expression in ovarian cancer

Kallikrein 6 (hK6, also known as protease M/zyme/neurosin) is a member of the human kallikrein gene family. We have previously cloned the cDNA for this gene by differential display and shown the overexpression of the mRNA in breast and ovarian primary tumour tissues and cell lines. To thoroughly characterise the expression of this kallikrein in ovarian cancer, we have developed a novel monoclonal antibody specific to hK6 and employed it in immunohistochemistry with a wide range of ovarian tumour samples. The expression was found elevated in 67 of 80 cases of ovarian tumour samples and there was a significant difference in the expression levels between normal and benign ovarian tissues and the borderline and invasive tumours (P<0.001). There was no difference of expression level between different subtypes of tumours. More significantly, high level of kallikrein 6 expression was found in many early-stage and low-grade tumours, and elevated hK6 proteins were found in benign epithelia coexisting with borderline and invasive tissues, suggesting that overexpression of hK6 is an early phenomenon in the development of ovarian cancer. Quantitative real-time reverse transcription–polymerase chain reactions also showed elevated kallikrein 6 mRNA expression in ovarian tumours. Genomic Southern analysis of 19 ovarian tumour samples suggested that gene amplification is one mechanism for the overexpression of hK6 in ovarian cancer.

Lysophospholipids Are Potential Biomarkers of Ovarian Cancer

Objective: To determine whether lysophosphatidic acid (LPA) and other lysophospholipids (LPL) are useful markers for diagnosis and/or prognosis of ovarian cancer in a controlled setting. Method: Plasma samples were collected from ovarian cancer patients and healthy control women in Hillsborough and Pinellas counties, Florida, and processed at the University of South Florida H. Lee Moffitt Cancer Center and Research Institute (Moffitt). Case patients with epithelial ovarian cancer (n = 117) and healthy control subjects (n = 27) participated in the study. Blinded LPL analysis, including 23 individual LPL species, was performed at the Cleveland Clinic Foundation using an electrospray ionization mass spectrometry–based method. LPL levels were transmitted to Moffitt, where clinical data were reviewed and statistical analyses were performed. Results: There were statistically significant differences between preoperative case samples (n = 45) and control samples (n = 27) in the mean levels of total LPA, total lysophosphatidylinositol (LPI), sphingosine-1-phosphate (S1P), and individual LPA species as well as the combination of several LPL species. The combination of 16:0-LPA and 20:4-LPA yielded the best discrimination between preoperative case samples and control samples, with 93.1% correct classification, 91.1% sensitivity, and 96.3% specificity. In 22 cases with both preoperative and postoperative samples, the postoperative levels of several LPL, including S1P, total LPA, and lysophosphatidylcholine (LPC) levels and some individual species of LPA and LPC, were significantly different from preoperative levels. Conclusion: LPA, LPI, LPC, and S1P appear useful as diagnostic and prognostic biomarkers of ovarian cancer.

Ovarian cancer: the clinical role of US, CT, and MRI

This article presents an overview of ovarian cancer, which addresses the clinical roles of imaging studies, including US, CT, and MR imaging in the course of diagnosis and treatment of this important disease. US is the modality of choice in the evaluation of patients with suspected adnexal masses. Although its accuracy is not sufficient to avert surgery, morphological analysis of adnexal masses with US helps narrow the differential diagnosis, determining the degree of suspicion for malignancy, usually in concert with a serum CA-125 level. Combined morphological and vascular imaging obtained by US appear to further improve the preoperative assessment of adnexal masses. For uncertain or problematic cases, MR imaging helps to distinguish benign from malignant, with an overall accuracy for the diagnosis of malignancy of 93%. The accuracy of MR imaging in the confident diagnosis of mature cystic teratoma, endometrial cysts, and leiomayomas is very high. CT is not indicated for differential diagnosis of adnexal masses because of poor soft tissue discrimination, except for fatty tissue and for calcification, and the disadvantages of irradiation. In the staging of ovarian cancer, CT, US, and MR imaging all have a similarly high accuracy. Although it is difficult to suggest a simple algorithm for evaluating the state of women with adnexal masses, the correct preoperative diagnosis and staging of ovarian cancer with the use of any of these imaging studies will lead to an appropriate referral to a specialist in gynecologic oncology and offer a significant survival advantage for patients with ovarian cancer.

Quantitative analysis of acyl-lysophosphatidic acid in plasma using negative ionization tandem mass spectrometry

Analysis of acyl-lysophosphatidic acids (LPAs) has clinical importance as a potential biomarker for ovarian and other gynecological cancers or obesity from the point of view of prevention. Here we report a simple sample preparation and analytical method with high sensitivity and specificity for the early detection of gynecological cancers to improve the overall outcome of this disease. We established a novel quantification method for acyl-LPAs in plasma by electrospray negative ionization tandem mass spectrometry (MS-MS) using multiple reaction monitoring mode without conventional TLC step. Protein-bound lipids, acyl-LPAs in plasma were extracted with methanol/chloroform (2:1) containing LPA C(14:0) as internal standard under acidic conditions. Following back-extraction with chloroform and water, the centrifuged lower phase was evaporated and reconstituted in methanol and then analyzed. Using ESI-MS-MS with negative ionization MRM mode, all the species of LPAs were completely separated from plasma matrix without severe interference. For MRM mode, Q1 ions selected were m/z 409, 433, 435, 437 and 457 which corresponds to molecular mass [M-H](-) of C(16:0), C(18:2), C(18:1), C(18:0) and C(20:4) LPA, respectively. Q2 ions selected for MRM was m/z 79, phosphoryl product. Using MS-MS with MRM mode, all the species of LPAs were completely separated from plasma matrix without severe interference. This method allowed simultaneous detection and quantification of different species of LPAs in plasma over a linear dynamic range of 0.01-25 micromol/l. The method detection limit was 0.3 pmol/ml with correlation coefficient of 0.9983 in most LPAs analyzed. When applied to plasma from normal and gynecological cancer patients, this new method differentiated two different groups by way of total LPA level.

Fatty acid composition of lysophosphatidic acid and lysophosphatidylinositol in plasma from patients with ovarian cancer and other gynecological diseases

OBJECTIVE

We previously reported that plasma levels of total lysophosphatidic acid (LPA) represented a potential biomarker for ovarian cancer and other gynecological cancers [1]. However, total LPA is composed of different LPA species with distinct fatty acid chains. The major objective of the current study, therefore, was to determine whether one or more specific fatty acid LPA species was associated with disease or disease staging. If this was determined, these species could be useful in further improving the sensitivity and/or specificity of this biomarker for the diagnosis and/or prognosis of the disease. Because lysophosphatidylinositol (LPI) co-migrates with LPA, this study represents the analysis of combined molecular species from both lysolipid classes.

METHODS

The patient population, sample collection, and analyses have been reported previously [1]. Lipids were hydrolyzed from the LPA band on thin-layer chromatography plates. The following individual fatty acid species were analyzed by gas chromatography: palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), arachidonic acid (20:4), and docosahexaenoic acid (22:6). The LPA/LPI fatty acid composition levels were analyzed and compared with disease status.

RESULTS

Distinct plasma LPA/LPI fatty acid chain species were not associated with ovarian or other gynecological cancers, compared to patients with benign gynecological disease or healthy controls. However, an increased presence of unsaturated fatty acids in plasma LPA/LPI was found in patients with late-stage or recurrent ovarian cancer and possibly with other gynecological cancers.

CONCLUSIONS

Analysis of individual fatty acid species present in plasma LPA/LPI do not appear to enhance the sensitivity or specificity of total LPA/LPI as a marker for gynecological cancer detection. However, our results suggest that increased LPA/LPI species with unsaturated fatty acid chains may be associated with late-stage or recurrent ovarian cancer.

Evaluation of plasma lysophospholipids for diagnostic significance using electrospray ionization mass spectrometry (ESI-MS) analyses

We previously reported that lysophosphatidic acid (LPA) represents a potential biomarker for ovarian and other gynecologic cancers. To further improve the accuracy and potentially increase the sensitivity and specificity of the assay, we developed an electrospray ionization mass spectrometry (ESI-MS)-based method to analyze LPA and related lysophospholipids. LPA, lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS), and lysophosphatidylcholine (LPC) could be detected with high sensitivity (in low pmol range) using this method. Standard curves were established for quantitative analysis. LPA and closely related lysophospholipids isolated from thin-layer chromatography (TLC) plates were analyzed directly by ESI-MS. This ESI-MS-based assay allows simultaneous detection and quantitation of all different species of LPAs and LPIs in a sample over a range of at least 5-300 pmol. Moreover, this test was at least 50 times more sensitive when a multiple reaction monitoring (MRM) mode was used. Using these protocols in a limited set of analysis, we found that both LPA and LPI were elevated in patients with ovarian cancer.

Secretion of activin A in recurrent epithelial ovarian carcinoma

OBJECTIVES

Activin A is a dimeric protein, composed of two beta-A subunits, that belongs to the TGF-beta family of growth factors. Most primary epithelial ovarian tumors (96%) synthesize and secrete activin protein in vitro and preliminary studies show that serum levels of activin are frequently elevated in women with epithelial ovarian cancer. Our objectives were to expand on studies of serum activin A levels in women with epithelial ovarian cancer and to determine whether levels of activin A correlate with the clinical course of disease.

METHOD

Preoperative serum activin A levels were measured in 41 patients with epithelial ovarian cancer. In addition, serum activin A levels were measured in all available postoperative samples from the subset of these patients (n = 26) who had an elevated preoperative serum activin A level. Medical record information was used to compare each patient's serum levels of activin A to the clinical course of disease.

RESULTS

Seventy-two percent of the stage III and IV patients (26/36), and none (0/5) of the stage I patients, had an elevated preoperative serum activin level. In postoperative samples, activin A levels were increased with persistent or recurrent (n = 9) stage III or IV ovarian cancer. Activin A levels dropped postoperatively and remained at or below the control level in patients in remission.

CONCLUSION

Serum activin A levels correlate with recurrent or persistent disease in patients with epithelial ovarian cancer.