Progress and challenges in screening for early detection of ovarian cancer

Serum protein markers for early detection of ovarian cancer

Early diagnosis of epithelial ovarian cancer (EOC) would significantly decrease the morbidity and mortality from this disease but is difficult in the absence of physical symptoms. Here, we report a blood test, based on the simultaneous quantization of four analytes (leptin, prolactin, osteopontin, and insulin-like growth factor-II), that can discriminate between disease-free and EOC patients, including patients diagnosed with stage I and II disease, with high efficiency (95%). Microarray analysis was used initially to determine the levels of 169 proteins in serum from 28 healthy women, 18 women newly diagnosed with EOC, and 40 women with recurrent disease. Evaluation of proteins that showed significant differences in expression between controls and cancer patients by ELISA assays yielded the four analytes. These four proteins then were evaluated in a blind cross-validation study by using an additional 106 healthy females and 100 patients with EOC (24 stage I/II and 76 stage III/IV). Upon sample decoding, the results were analyzed by using three different classification algorithms and a binary code methodology. The four-analyte test was further validated in a blind binary code study by using 40 additional serum samples from normal and EOC cancer patients. No single protein could completely distinguish the cancer group from the healthy controls. However, the combination of the four analytes exhibited the following: sensitivity 95%, positive predictive value (PPV) 95%, specificity 95%, and negative predictive value (NPV) 94%, a considerable improvement on current methodology.

Enhanced expression of peroxisome proliferator-activated receptor gamma in epithelial ovarian carcinoma

The peroxisome proliferator-activated receptors (PPARs) belong to a subclass of nuclear hormone receptor that executes important cellular transcriptional functions. Previous studies have demonstrated the expression of PPARγ in several tumours including colon, breast, bladder, prostate, lung and stomach. This study demonstrates the relative expression of PPARγ in normal ovaries and different pathological grades of ovarian tumours of serous, mucinous, endometrioid, clear cell and mixed subtypes. A total of 56 ovarian specimens including 10 normal, eight benign, 10 borderline, seven grade 1, nine grade 2 and 12 grade 3 were analysed using immunohistochemistry. Immunoreactive PPARγ was not expressed in normal ovaries. Out of eight benign and 10 borderline tumours, only one tumour in each group showed weak cytoplasmic PPARγ expression. In contrast, 26 out of 28 carcinomas studied were positive for PPARγ expression with staining confined to cytoplasmic and nuclear regions. An altered staining pattern of PPARγ was observed in high-grade ovarian tumours with PPARγ being mostly localized in the nuclei with little cytoplasmic immunoreactivity. On the other hand, predominant cytoplasmic staining was observed in lower-grade tumours. Significantly increased PPARγ immunoreactivity was observed in malignant ovarian tumours (grade 1, 2 and 3) compared to benign and borderline tumours (χ²=48.80, P<0.001). Western blot analyses showed significant elevation in the expression of immunoreactive PPARγ in grade 3 ovarian tumours compared with that of normal ovaries and benign ovarian tumours (P<0.01). These findings suggest an involvement of PPARγ in the onset and development of ovarian carcinoma and provide an insight into the regulation of this molecule in the progression of the disease.

Applying Proteomics in Clinical Trials

Ovarian cancer is the leading cause of death from gynecologic malignancies among American women and the fourth most frequent cause of death from cancer in women in Europe and the US. Despite appropriate surgical and chemotherapeutic intervention, the 5-year survival in patients with metastatic cancer remains poor. Currently available screening methods, including CA125, additional biomarkers, and transvaginal ultrasound lack the necessary sensitivity and specificity to provide accurate and cost-efficient screening for the general population or the ability to assess who will benefit most from each treatment. These limitations have prompted the study of proteomic technology and its application in ovarian cancer diagnostics. Proteomics is the study of molecules in the functional protein pathways of normal or diseased states. Clinical trials are currently being conducted to assess the sensitivity and specificity of serum proteomic patterns and additional clinical trials are designed to evaluate the effects of molecularly targeted agents on protein signaling pathways in human subjects. Overcoming both scientific and practical limitations will lead to increased knowledge of deranged protein networks in cancer cells. Clinical trials in proteomics may result in improved early detection, better monitoring, new drugs and molecularly targeted therapeutics, and individualized therapies.

Proteomics and ovarian cancer: implications for diagnosis and treatment: a critical review of the recent literature

PURPOSE OF REVIEW

Epithelial ovarian cancer is the leading cause of death from gynecologic malignancies amongst American women. Emerging proteomic technologies have promise for early diagnosis and in advancing treatment directions. Application of these technologies has produced new biomarkers, diagnostic approaches, and understanding of disease biology.

RECENT FINDINGS

Mass spectral blood and tissue analysis has yielded new putative biomarkers that require further validation and assessment of diagnostic specificity and sensitivity. Protein signature patterns derived from mass spectrometry datastreams have been modeled and are moving into validation. Tissue-based protein analysis has led to identification of tumor and stromal protein and signal activation events in ovarian cancer. Clinical trials are now ascertaining tissue samples prior to and during therapy with molecularly targeted agents to evaluate modulation of targeted signaling pathways. Finally, proteomic analysis of tissues and metastases will outline biochemical events underlying the metastatic phenotype of ovarian cancer.

SUMMARY

Proteomic approaches are experimental technologies applied to ovarian and other cancers. Proper validation and use of findings may advance our understanding of biochemical events that have complicated successful detection and intervention. This knowledge is the first step in fulfilling the promise of personalized molecular medicine.