THE ROLE OF PLATELETS IN OVARIAN CARCINOMA

Platelets represent one of the largest storage pools of angiogenic and oncogenic growth factors in the human body. The observation that thrombocytosis (platelet count >450,000/uL) occurs in patients with solid malignancies was made over 100 years ago. However, the clinical and biological implications as well as the underlying mechanism of paraneoplastic thrombocytosis associated with ovarian carcinoma remains unknown and were the focus of the current study. Following IRB approval, patient data were collected on 619 patients from 4 U.S. centers and used to test associations between platelet count at initial diagnosis, clinicopathologic factors, and outcome. In vitro effects of plasma-purified platelets on ovarian cancer cell proliferation, docetaxel-induced apoptosis, and migration were evaluated using BrdU-PI flow cytometric and two-chamber chemotaxis assays. In vivo effects of platelet depletion on tumor growth, proliferation, apoptosis, and angiogenesis were examined using an anti-platelet antibody (anti-mouse glycoprotein 1ba, Emfret) to reduce platelets by 50%. Complete blood counts and number of mature megakaryocytes in the spleen and bone marrow were compared between control mice and ovarian cancer-bearing mice. Plasma levels of key megakaryo- and thrombopoietic factors including thrombopoietin (TPO), IL-1a, IL-3, IL-4, IL-6, IL-11, G-CSF, GM-CSF, stem cell factor, and FLT-3 ligand were assayed in a subset of 150 patients at the time of initial diagnosis with advanced stage, high grade epithelial ovarian cancer using immunobead-based cytokine profiling coupled with the Luminex® xMAP platform. Plasma cytokines significantly associated with thrombocytosis in ovarian cancer patients were subsequently evaluated in mouse models of ovarian cancer using ELISA immunoassays. The results of human and mouse plasma cytokine profiling were used to inform subsequent in vivo studies evaluating the effect of siRNA-induced silencing of select megakaryo- and thrombopoietic cytokines on paraneoplastic thrombocytosis. Thirty-one percent of patients had thrombocytosis at initial diagnosis. Compared to patients with normal platelet counts, women with thrombocytosis were significantly more likely to have advanced stage disease (p<0.001) and poor median progression-free (0.94 vs 1.35 years, p<0.001) and overall survival (2.62 vs 4.65 years, p<0.001). On multivariate analysis, thrombocytosis remained an independent predictor of decreased overall survival. Our analysis revealed that thrombocytosis significantly increases the risk of VTE in ovarian cancer patients and that thrombocytosis is an independent predictor of increased mortality in women who do develop a blood clot. Platelets increased ovarian cancer cell proliferation and migration by 4.1- and 2.8-fold (p<0.01), respectively. Platelets reduced docetaxel-induced apoptosis in ovarian cancer cells by 2-fold (p<0.001). In vivo, platelet depletion reduced tumor growth by 50%. Staining of in vivo specimens revealed decreased tumor cell proliferation (p<0.001) and increased tumor and endothelial cell apoptosis (p<0.01). Platelet depletion also significantly decreased microvessel density and pericyte coverage (p<0.001). Platelet counts increase by 31-130% in mice with invasive ovarian cancer compared to controls (p<0.01) and strongly correlate with mean megakaryocyte counts in the spleen and bone marrow (r=0.95, p<0.05). Plasma levels of TPO, IL-6, and G-CSF were significantly increased in ovarian cancer patients with thrombocytosis. Plasma levels of the same cytokines were found to be significantly elevated in orthotopic mouse models of ovarian cancer, which consistently develop paraneoplastic thromocytosis. Silencing TPO, IL-6, and G-CSF significantly abrogated paraneoplastic thrombocytosis in vivo. This study provides new understanding of the clinical and biological significance of paraneoplastic thrombocytosis in ovarian cancer and uncovers key humoral factors driving this process. Blocking the development of paraneoplastic thrombocytosis and interfering with platelet-cancer cell interactions could represent novel therapeutic strategies.

The epidemiology of chronic fatigue in San Francisco

Chronic fatigue syndrome (CFS) is a recently defined condition characterized by severe disabling fatigue that persists for a minimum of six months, and a host of somatic and neurocognitive symptoms. Although conditions similar to CFS have been described in the medical literature for over 100 years, little is known about the epidemiology of CFS or of chronic fatigue generally. The San Francisco Fatigue Study was undertaken to describe the prevalence and characteristics of self-reported chronic fatigue and associated conditions in a diverse urban community. The study utilized a cross-sectional telephone survey of a random sample of households in San Francisco, followed by case/control interviews of fatigued and nonfatigued subjects. Respondents were classified as chronically fatigued (CF) if they reported severe fatigue lasting six months or longer, then further classified as having CFS-like illness if, based on self-reported information, their condition appeared to meet CFS case definition criteria. Subjects who reported idiopathic chronic fatigue that did not meet CFS criteria were classified as having ICF-like illness.^ 8004 households were screened, yielding fatigue and demographic information on 16970 residents. CF was reported by 635 persons, 3.7% of the study population. CFS-like illness was identified in 34 subjects (0.2%), and ICF-like illness in 259 subjects (1.6%). Logistic regression analysis indicated that prevalence odds ratios for CFS-like illness were significantly elevated for females compared to males (OR = 2.9), and in Blacks (OR = 2.9) and Native Americans (OR = 13.2) relative to Whites, but significantly lower in Asians (OR = 0.12). Above-average household income was protective for all categories of CF. CFS-like subjects reported more symptoms and were more severely disabled than ICF-like subjects, but the pattern of symptoms experienced by both groups was similar. In conclusion, unexplained chronic fatigue, including CFS-like illness, occurs in all sociodemographic groups, but may be most prevalent among persons with lower incomes and in some racial minorities. Future studies that include clinical evaluation of incident cases of CFS and ICF are required to further clarify the epidemiology of unexplained chronic fatigue in the population. ^