Critical steps in hematogenous metastasis: an overview

Metastasis is responsible for most cancer deaths. A better understanding of the process provides opportunities to develop new treatments to prevent metastasis. This article summarizes findings from experimental in vivo videomicroscopy and quantitative studies on metastatic inefficiency, which indicate that early steps in hematogenous metastasis may be quite efficient, but that regulation of cancer cell growth in secondary sites determines metastatic outcome. The authors have identified three key stages of this growth regulation: survival of a subset of single cells, proliferation of a subset of these cells to form preangiogenic micrometastases, and persistence of growth of a subset of these to form vascularized metastases. Formation of clinically relevant metastases is determined by the proportion of cells that proceeds successfully through each stage, and surviving single cells and preangiogenic micrometastases both represent possible sources of tumor dormancy.

Temporal progression of metastasis in lung: cell survival, dormancy, and location dependence of metastatic inefficiency

Cancer metastasis is an inefficient process. The steps in metastasis responsible for this inefficiency and how metastatic inefficiency can vary in different locations within an organ remain poorly understood. B16F10 cells were injected to target mouse lung, and at sequential times thereafter we quantified in lung the time course of: (a) overall cell survival and metastatic development; and (b) local cell survival and growth with respect to the lung surface and specific interior structures. We found high rates of initial survival of cells trapped in the lung circulation, extravasation into lung tissue, and subsequent survival of extravasated solitary cells (74% at day 3) before metastasis formation. However, at the time of initial replication of metastatic cells a major loss of cells occurred. Although only a small proportion of injected cells started to form metastases, most of these developed into macroscopic tumors. Solitary cells found at later times were dormant. Thus, overall metastatic inefficiency was largely due to postextravasation events affecting solitary cells. Regionally within the lung, cells and metastases were randomly distributed to day 4, but by day 10 preferential tumor growth was found along the lung surface and around arterial and venous vessels. Thus, trapping and early growth of injected cells was unaffected by location within the lung, whereas subsequent metastatic growth was enhanced in specific microenvironments. This study: (a) quantifies early temporal and spatial progression of metastasis in lung; (b) documents persistence of solitary dormant cells; and (c) shows that metastatic inefficiency depends on the initiation of growth in a subset of extravasated cells, whereas continued growth of metastases occurs preferentially in specific tissue environments.

Hemoglobinopathies and glucose-6-phosphate dehydrogenase deficiency in hospital births in Bahrain

In view of the high prevalence of clinical cases of sickle cell anemia, hemoglobin-H-disease and glucose-6-phosphate dehydrogenase deficiency in the archipelago of the State of Bahrain, a cord blood screening study was undertaken over a 15 month period (October 1984 to December 1985) to determine the gene frequency of these diseases. All the state hospitals participated in this study and a total of 10,327 cord blood samples obtained from babies born to Bahraini parents were analyzed. These presented over 80% of all neonates born in the country during the study period. The phenotypes detected included: AF, AF-Barts, SFA and SFA-Barts. Homozygous sickle cell disease was detected in 2.1%, and in 11.2%, the sickle cell trait was present. The incidence of alpha-thalassemia gene based on elevated Bart's hemoglobin was 24.3% in these neonates. The incidence of G6PD-deficiency was as high as 20.9%. Availability of these statistics has enabled the authorities in the Ministry of Health in collaboration with the National Hereditary Anemia Society to plan a comprehensive health care program for patients with hereditary diseases and their families.