Embryology, anatomy, physiology and pathophysiology of the peritoneum and the peritoneal vasculature.

The peritoneum is a large serous membrane with both epithelial and mesenchymal features, and is essential for maintaining an intra-abdominal homeostatic equilibrium. The peritoneum plays a central role in the pathogenesis of a number of disorders. Pathological processes affecting the peritoneum such as inflammation and carcinomatosis can have serious clinical consequences, but the pathophysiology of these conditions is poorly understood. Understanding peritoneal embryology, anatomy and physiology is crucial to comprehend pathophysiological mechanisms and to devise a new focus for research. The vascular response to pathological processes appears to be of considerable importance, since the peritoneal vasculature plays a pivotal role in most associated diseases. Therefore, this review summarizes currently available literature with special emphasis on the development, anatomy and function of the peritoneal vasculature. Pathological processes are described to illustrate physiological and pathophysiological characteristics of the peritoneum.

Homologous Recombination Deficiency and Cyclin E1 Amplification Are Correlated with Immune Cell Infiltration and Survival in High-Grade Serous Ovarian Cancer.

BACKGROUND: How molecular profiles are associated with tumor microenvironment (TME) in high-grade serous ovarian cancer (HGSOC) is incompletely understood. Therefore, we analyzed the TME and molecular profiles of HGSOC and assessed their associations with overall survival (OS). METHODS: Patients with advanced-stage HGSOC treated in three Dutch hospitals between 2008-2015 were included. Patient data were collected from medical records. BRCA1/2 mutation, BRCA1 promotor methylation analyses, and copy number variations were used to define molecular profiles. Immune cells were assessed with immunohistochemical staining. RESULTS: 348 patients were categorized as BRCA mutation (BRCAm) (BRCAm or promotor methylation) (30%), non-BRCA mutated HRD (19%), Cyclin E1 (CCNE1)-amplification (13%), non-BRCAmut HRD and CCNE1-amplification (double classifier) (20%), and no specific molecular profile (NSMP) (18%). BRCAm showed highest immune cell densities and CCNE1-amplification lowest. BRCAm showed the most favorable OS (52.5 months), compared to non-BRCAmut HRD (41.0 months), CCNE1-amplification (28.0 months), double classifier (27.8 months), and NSMP (35.4 months). Higher immune cell densities showed a favorable OS compared to lower, also within the profiles. CD8+, CD20+, and CD103+ cells remained associated with OS in multivariable analysis. CONCLUSIONS: Molecular profiles and TME are associated with OS. TME differs per profile, with higher immune cell densities showing a favorable OS, even within the profiles. HGSOC does not reflect one entity but comprises different entities based on molecular profiles and TME.

Poor perfusion of the microvasculature in peritoneal metastases of ovarian cancer.

Most women with epithelial ovarian cancer (EOC) suffer from peritoneal carcinomatosis upon first clinical presentation. Extensive peritoneal carcinomatosis has a poor prognosis and its pathophysiology is not well understood. Although treatment with systemic intravenous chemotherapy is often initially successful, peritoneal recurrences occur regularly. We hypothesized that insufficient or poorly-perfused microvasculature may impair the therapeutic efficacy of systemic intravenous chemotherapy but may also limit expansive and invasive growth characteristic of peritoneal EOC metastases. In 23 patients with advanced EOC or suspicion thereof, we determined the angioarchitecture and perfusion of the microvasculature in peritoneum and in peritoneal metastases using incident dark field (IDF) imaging. Additionally, we performed immunohistochemical analysis and 3-dimensional (3D) whole tumor imaging using light sheet fluorescence microscopy of IDF-imaged tissue sites. In all metastases, microvasculature was present but the angioarchitecture was chaotic and the vessel density and perfusion of vessels was significantly lower than in unaffected peritoneum. Immunohistochemical analysis showed expression of vascular endothelial growth factor and hypoxia inducible factor 1α, and 3D imaging demonstrated vascular continuity between metastases and the vascular network of the peritoneum beneath the elastic lamina of the peritoneum. We conclude that perfusion of the microvasculature within metastases is limited, which may cause hypoxia, affect the behavior of EOC metastases on the peritoneum and limit the response of EOC metastases to systemic treatment.

Development of Peritoneal Carcinomatosis in Epithelial Ovarian Cancer: A Review.

Epithelial ovarian cancer (EOC) metastasizes intra-abdominally with often numerous, superficial, small-sized lesions. This so-called peritoneal carcinomatosis is difficult to treat, and peritoneal recurrences are frequently observed, leading to a poor prognosis. Underlying mechanisms of interactions between EOC and peritoneal cells are incompletely understood. This review summarizes and discusses the development of peritoneal carcinomatosis from a cell-biological perspective, focusing on characteristics of EOC and peritoneal cells. We aim to provide insight into how peritoneum facilitates tumor adhesion but limits size of lesions and depth of invasion. The development of peritoneal carcinomatosis is a multistep process that requires adaptations of EOC and peritoneal cells. Mechanisms that enable tumor adhesion and growth involve cadherin restructuring on EOC cells, integrin-mediated adhesion, and mesothelial evasion by mechanical forces driven by integrin-ligand interactions. Clinical trials targeting these mechanisms, however, showed only limited effects. Other factors that inhibit tumor growth and deep invasion are virtually unknown. Future studies are needed to elucidate the exact mechanisms that underlie the development and limited growth of peritoneal carcinomatosis. This review on development of peritoneal carcinomatosis of EOC summarizes the current knowledge and its limitations. Clarification of the stepwise process may inspire future research to investigate new treatment approaches of peritoneal carcinomatosis.