[Procoagulant and aggregating platelet activities of human mammary tumor cells]. / Activités procoagulantes et agrégantes plaquettaires des cellules tumorales mammaires humaines.

The ability of tumor cells to initiate coagulation, platelet aggregation and subsequent thrombotic alterations is believed to facilitate metastatic process. The mechanisms by which tumor cells develop thrombotic events in malignancy are discussed. We have examined the procoagulant activity and the modifications of rheologic platelet functions induced by 3 human mammary tumor cell lines (MCF-7, ZR-75-1, BT-20) using a laser-thromborheometer. According to experimental conditions, these 3 tumor cell lines aggregate platelets via a thrombin-dependent mechanism. Moreover, MCF-7 cells also induce ADP-like platelet aggregation. These data suggest the existence of several mechanisms of mammary tumor cell-induced platelet aggregation.

The collagenase gene family in humans consists of at least four members.

Stromelysin is a collagenase-related connective-tissue-degrading metalloproteinase. We have detected RNAs capable of hybridizing to a rat stromelysin cDNA in 11 of 69 human tumours tested. Molecular cloning of cDNAs to these RNAs has identified them as a mixture of stromelysin RNA and a transcript of a hitherto-undescribed related human gene, the stromelysin-2 gene. We have also isolated cDNAs corresponding to a more distantly related new human gene, the pump-1 gene. A comparison of the cDNA-derived amino acid sequences of stromelysin-2 and pump-1 with the known sequences of stromelysin and collagenase reveals significant similarities, with conservation of sequence motifs believed to have functional importance in metalloproteinase action. We conclude that the collagenase gene family in humans consists of at least four members, and speculate that expression of these genes plays a role in cancer.

Adhesion of human breast cancer cell line MCF-7 to human vascular endothelial cells in culture. Enhancement by activated platelets.

The interactions of MCF-7 tumor cells with human vascular endothelial cells (EC) and subendothelial extracellular matrices (ECM) were morphologically observed by electron microscopy and quantitatively evaluated by labelling tumor cells with 111Indium-oxine. MCF-7 tumor cells adhered more rapidly to ECM than to the apical surface of a confluent monolayer of EC. The affinity of MCF-7 cells for type-IV collagen was greater than for fibronectin, suggesting that type-IV collagen contributes to the higher rate of adhesion of MCF-7 cells to the subendothelial ECM. Otherwise, the attachment of tumor cells to EC was increased in the presence of both washed platelets and 0.1% citrated platelet-poor plasma (cPPP), a condition accelerating platelet aggregation by tumor cells. The enhancement of MCF-7 adhesion to EC in the presence of platelets and cPPP was completely blocked by the addition of prostacyclin, or hirudin, a specific thrombin inhibitor. In ultrastructural studies, MCF-7 initiated EC retraction, and firm attachment and flattening occurred on exposed ECM. When MCF-7 cells were incubated with platelets and cPPP, most of the tumor cells adhering to the EC and inducing disruption of endothelial monolayer were closely packed and associated with platelet aggregates. MCF-7 cells appeared to adhere more efficiently to exposed subendothelial ECM when they were associated into multicellular aggregates containing platelets and trapped in a fibrin thrombus. Thus, this homologous human system of cultured vascular EC and breast carcinoma line MCF-7 cells may be used to assess anti-aggregant compounds for their ability to alter tumor-cell implantation on EC-lined surfaces.

Characterization of cell types in human breast tumor primary cultures.

Primary cultures of cells from breast carcinomas were attempted in 74 cases. Growth was observed in 46 cases. Using immunochemical demonstration of keratin proteins (KER), epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), three morphologically distinct cell populations were characterized and described. Two cell types (E- and E'-cells) were identified as epithelial by their positive staining for KER and EMA. The third type (F cells) displayed a negative staining for these two epithelial markers; they were considered as stromal cells (fibroblasts). More than 50% of the cultures consisted of pure epithelial cells. Positive CEA staining was observed only in KER- and EMA-positive cells. Out of the 30 cultures, 15 displayed positive staining for CEA. In 7 of these, 30-50% of cells displayed positive, diffuse staining for CEA. The other 8 cultures consisted of more than 50% CEA-positive cells. Strong and homogeneous positivity was restricted to the E-cells, while in the same cultures, E'-cells displayed heterogeneous and diffuse staining. Efficiency and value of this cell culture system are discussed, in comparison with other human breast tumor cell (HBTC) culture techniques. Identification of growing cells and cellular composition of primary cultures are emphasized.

A simple in vitro model of mechanical injury of confluent cultured endothelial cells to study quantitatively the repair process.

A model of in vitro mechanical injury of confluent human endothelial cells (EC) in culture was developed. Human EC were obtained from umbilical veins and grown to confluence. Application on the EC monolayer of a calibrated disk of cellulose polyacetate paper resulted in removal of the EC, leaving a continuous subendothelial extracellular matrix (ECM) on the culture dish. The regeneration time depended on the original size of the lesion. Regeneration was similar with EC grown on different substrates such as human fibronectin, human subendothelial ECM, bovine collagen type I or surfaces coated with Transglutine, a surgical glue containing adhesive proteins. A human brain extract containing growth factor activity accelerated significantly the repair of the lesion, especially at low serum concentration. This simple in vitro model of mechanical injury allows the quantitative study of the effects of matrices, growth factors and pharmacological agents on the repair process.