Heterogeneity Of Ovarian Cancer Research Articles

Tumor heterogeneity in ovarian cancer as demonstrated by in vitro chemoresistance assays

Objective Tumor heterogeneity has been demonstrated in solid tumors. In vitro assays were developed in an effort to predict in vivo tumor response to therapy. We compare the in vitro assay results from multiple synchronous tumor samples in primary and recurrent ovarian cancers. Methods 38 patients underwent surgery for primary (18) or recurrent (20) ovarian cancer. Two (22) or three (16) samples were obtained per patient and tested using the EDR assay (Oncotech, Inc.). The percentage of Extreme (E), Intermediate (I) and Low (L) drug resistance for each chemotherapy was compared between synchronous specimens. Results A total of 92 samples were collected and 787 drug assays were performed. Tumor heterogeneity was seen in 22.4% of all cases, including 18.6% primary and 26.1% recurrent diseases ( p = 0.01). Two category differences (L vs. E) were seen in 4.1% primary and 11.3% recurrent cases (7.8% of all cases). Overall, an increased frequency in EDR was seen in recurrent disease as compared to primary for all agents tested (22.9% primary vs. 31.6% recurrent, p = 0.006). Marked heterogeneity of the drug resistance profiles was seen with paclitaxel as compared with cisplatin/gemcitabine ( p = 0.03), taxotere ( p = 0.04) or topotecan ( p = 0.04). No association was demonstrated between assay results and clinicopathologic parameters collected in this cohort. Conclusions Treatment failure is often attributed to the development of chemoresistance. These results suggest that tumor heterogeneity may play an equally important role in treatment failure. Recurrent lesions exhibit greater heterogeneity and more frequent EDR. These data can influence therapeutic strategy i.e., multiple samples, sequential, or consolidation therapy.

Editorial—Dr. James Orsini

To explore and facilitate the multifaceted process of drug development and regulatory approval in ovarian cancer.The Society of Gynecologic Oncology (SGO) recently sought and received input from multiple stakeholders including the National Cancer Institute's (NCI) Clinical Therapy Evaluation Program (CTEP), the Food and Drug Administration (FDA), pharmaceutical industry, and patient advocates. This whitepaper is the work product and opinion solely of the SGO.This document summarizes the SGO's interpretation of these meetings and the current regulatory environment where there has been a paucity of recent approvals in the United States. It provides guidance in clinical trial design with the express purpose of encouraging novel drug development in ovarian cancer. Points of emphasis include: ovarian cancer heterogeneity (histologic subtypes and molecular genetic alterations), clinical trial design elements, surrogate as well as composite endpoints, and the four principles of clinical drug development (unmet medical need, discovery, safety, and efficacy).There has been an evolution in the acceptance of surrogate endpoints depending upon the clinical setting in ovarian cancer. While overall survival (OS) remains the most objective clinical trial endpoint, there is now realization that demanding OS as the primary endpoint has many obstacles. Ovarian cancer is a heterogeneous disease that is now divided by histologic subtypes. Future registration strategies will need to address disease heterogeneity. The exploration of currently acceptable clinical trial endpoints and alternative regulatory strategies will hopefully stimulate interest in novel drug development for patients with ovarian cancer.

Early Detection of Ovarian Cancer

Despite advances in therapy, ovarian cancer remains the most deadly of the gynecological cancers. Less than 30% of women with advanced stage disease survive long-term. When diagnosed in stage I, up to 90% of patients can be cured with conventional surgery and chemotherapy. At present, only 25% of ovarian cancers are detected in stage I due, in part, to the absence of specific symptoms and to lack of an effective screening strategy. Early detection of ovarian cancer might significantly improve the overall survival rate of women with ovarian cancer if 1) most cancers are clonal and unifocal, arising in the ovary rather than in the peritoneum, 2) metastatic disease results from progression of clinically detectable stage I lesions, and 3) cancers remain localized for a sufficient interval to permit cost-effective screening. Given the prevalence of ovarian cancer, strategies for early detection must have high sensitivity for early stage disease (> 75%), but must have extremely high specificity (99.6%) to attain a positive predictive value of at least 10%. Transvaginal sonography (TVS), serum markers and a combination of the two modalities have been evaluated for early detection of ovarian cancer. Among the serum markers, CA125 has received the most attention, but lacks the sensitivity or specificity to function alone as a screening test. Greater specificity can be achieved by combining CA125 and TVS and/or by monitoring CA125 over time. Two stage screening strategies promise to be cost effective, where abnormal serum assays prompt TVS to detect lesions that require laparotomy. Accrual has been completed for a 200,000 woman trial in the United Kingdom that will test the ability of a rising CA125 to trigger TVS and subsequent exploratory surgery. Given the heterogeneity of ovarian cancer, it is unlikely that any single marker will be sufficiently sensitive to provide an effective initial screen. Sensitivity of serum assays might be enhanced by utilizing a panel of biomarkers. Candidate biomarkers have been discovered through empirical development of monoclonal antibodies, studies of gene expression, cloning of gene families and proteomic techniques. The development of technologies that measure multiple serum markers simultaneously, linked to the creation of statistical methods that enhance sensitivity without sacrificing specificity hold great promise.

Heterogeneity of Ovarian Cancer: Relationships Among Histological Group, Stage of Disease, Tumor Markers, Patient Characteristics, and Survival

Epidemiological studies have established associations between various reproductive factors and risk of ovarian cancer; it has also been observed that some of these risk factors are only associated with specific histological subgroups. To investigate the correlation of genetic alterations with these risk factors, we examined a consecutive series of 158 ovarian cancer cases treated at the University of Kentucky (1990–96). Common molecular genetic alterations (LOH on chromosome 17, P53 alterations, K-RAS mutations), histological and clinical characteristics of the disease, demographic patient information and survival were evaluated. These latter data were from the Kentucky Cancer Registry. Univariate analysis showed higher frequencies of chromosome 17 loss and P53 mutations in tumors of advanced stage and grade, and in older and post-menopausal women. Non-mucinous tumors were more likely to be classified as late stage, high-grade cancers, and to have chromosome 17 loss and P53 mutations. Survival analysis indicated that stage was the only independent significant variable. When stage was the outcome variable in multiple logistic regression analysis, histology and chromosome 17 loss were significantly associated with poor survival. This case-case study provides evidence that ovarian cancers of mucinous and non-mucinous histology are significantly different with respect to clinical characteristics, survival and molecular alterations. It also lends support to the hypothesis that ovarian cancer is a heterogeneous disease with distinct etiological factors and clinical outcomes, which may require different approaches to treatment.

HLA-A2 presents shared tumor-associated antigens derived from endogenous proteins in ovarian cancer.

Tumor-associated lymphocytes (TAL) from the malignant ascites and tumor-infiltrating lymphocytes (TIL) from the solid tumor were isolated from six consecutive untreated ovarian cancer patients. Tumor-specific CTL were generated from both TAL and TIL using solid phase anti-CD3, low dose IL-2 (50 IU/ml), and repeated tumor stimulation. The specificity of TAL and TIL was tested in standard cytotoxicity assays using autologous tumor, several allogeneic ovarian tumors, and the NK-sensitive cell line, K562. Anti-HLA-A-B-C mAb, W6/32, was used to demonstrate that these tumor-specific TAL and TIL were HLA class I-restricted. The ability of the ascitic and solid tumor to present Ag by HLA class I was assessed using Brefeldin A, a fungal metabolite that blocks the endogenous Ag-processing pathway in the viral model. Brefeldin A significantly inhibited tumor-specific cytotoxicity as well as HLA class I expression on the cell surface, suggesting an endogenous source of tumor-associated Ag. Despite previous reports of antigenic heterogeneity in ovarian cancer, shared tumor-associated Ag were shown to exist in this disease as demonstrated by significant allogeneic recognition of HLA-A2-matched patients as opposed to unmatched controls. Specifically, CTL from HLA-A2+ patients lysed HLA-A2+ allogeneic targets significantly better than HLA-A2- allogeneic or HLA-A2+ melanoma targets. There was no such difference with HLA-A2- effectors. Furthermore, HLA-A2 was confirmed to be a major restriction element in ovarian cancer by the blocking of HLA-A2+ effectors against both autologous and allogeneic HLA-A2+ targets with the anti-HLA-A2 mAb, BB7.2. These findings verify a similar lymphocyte/tumor interaction as has been documented in melanoma, suggesting a common mechanism of recognition of these human tumors by lymphocytes.