Identification and characterization of circulating prostate carcinoma cells

BACKGROUND Analysis of prostate carcinoma cells isolated from the peripheral blood suggested a classification based on three categories. METHODS Centrifugation density gradients and magnetic cell sorting were used to isolate circulating prostate carcinoma cells from peripheral blood. Immunocytochemistry staining and fluorescent in situ hybridization allowed characterization of isolated cancer cells. RESULTS Terminal cells can be divided into 3 classes: 1) large, buoyant, fragile cells with a large nucleus that were captured in a 1.068 g/mL gradient; 2) enucleate cells (4,6‐diamidino‐2‐phenylindole [DAPI] negative) that were positive for cytokeratin and PSMA antibodies; and 3) cellular debris exhibiting cytokeratin and PSMA positive staining as well as nuclear debris identified by DAPI staining, which included cytoplasmic debris. Growing cells also exhibited three morphologic characteristics: those possessing stem cell–like morphology and characteristics such as small size, high density, developed cytokeratin systems, PSMA expression, and aneuploidy; those in M phase; and cell clusters. The majority of isolated cells exhibited intermediate characteristics and thus comprised the third group of circulating cancer cells. CONCLUSIONS Although the significance of the cluster remains undetermined, observation suggests that the cluster has the ability to circulate as a microtumor and subsequently arrest in the small veins and capillaries. It is hypothesized that the clusters could escape certain facets of immune surveillance and possibly gain a selective growth advantage over single cells in a distant site. Further hypothesis proposes that arrested cells recruit growth‐promoting nutrients, which would result in the invasion of local blood vessels and vascularization. Cancer 2000;88:2787–95. © 2000 American Cancer Society.