Molecular inhibition of cancer cell invasion and metastasis.

in Princess Takamatsu Symposia (1991), 22

A group of coordinated cellular processes, not just one gene product, is responsible for invasion and metastasis, the most life-threatening aspect of cancer. It is now recognized that negative factors may ... [more ▼]

A group of coordinated cellular processes, not just one gene product, is responsible for invasion and metastasis, the most life-threatening aspect of cancer. It is now recognized that negative factors may be just as important as positive elements. Genetic changes causing an imbalance of growth regulation lead to uncontrolled proliferation necessary for both primary tumor and metastasis expansion. However, unrestrained growth does not, by itself, cause invasion and metastasis. This phenotype may require additional genetic changes. Thus, tumorigenicity and metastatic potential have both overlapping and separate features. Invasion and metastasis can be facilitated by proteins which stimulate tumor cell attachment to host cellular or extracellular matrix determinants, tumor cell proteolysis of host barriers, such as the basement membrane, tumor cell locomotion, and tumor cell colony formation in the target organ for metastasis. Facilitory proteins may act at many levels both intracellularly and extracellularly, but are counterbalanced by factors which can block their production, regulation or action. A common theme has emerged: in addition to loss of growth control, an imbalanced regulation of adhesion, proteolysis, and motility appears to be required for invasion and metastasis. Re-equilibrating the expression of the genes involved in these tumor invasion related events could potentially constitute the basis for new anti-cancer therapeutic strategies. [less ▲]

Spatiotemporal segregation of endothelial cell integrin and nonintegrin extracellular matrix-binding proteins during adhesion events.

in Journal of Cell Biology (1990), 110(3), 789-801

Bovine aortic endothelial cell (BAEC) attachments to laminin, fibronectin, and fibrinogen are inhibited by soluble arginine-glycine-aspartate (RGD)-containing peptides, and YGRGDSP activity is responsive ... [more ▼]

Bovine aortic endothelial cell (BAEC) attachments to laminin, fibronectin, and fibrinogen are inhibited by soluble arginine-glycine-aspartate (RGD)-containing peptides, and YGRGDSP activity is responsive to titration of either soluble peptide or matrix protein. To assess the presence of RGD-dependent receptors, immunoprecipitation and immunoblotting studies were conducted and demonstrated integrin beta 1, beta 3, and associated alpha subunits as well as a beta 1 precursor. Immunofluorescence of BAECs plated on laminin, fibronectin, and fibrinogen reveals different matrix-binding specificities of each of these integrin subclasses. By 1 h after plating, organization of beta 1 integrin into fibrillar streaks is influenced by laminin and fibronectin, whereas beta 3 integrin punctate organization is influenced by fibrinogen and the integrin spatial distribution changes with time in culture. In contrast, the nonintegrin laminin-binding protein LB69 only organizes after cell-substrate contact is well established several hours after plating. Migration of BAECs is also mediated by both integrin and nonintegrin matrix-binding proteins. Specifically, BAEC migration on laminin is remarkably sensitive to RGD peptide inhibition, and, in its presence, beta 1 integrin organization dissipates and reorganizes into perinuclear vesicles. However, RGD peptides do not alter LB69 linear organization during migration. Similarly, agents that block LB69--e.g., antibodies to LB69 as well as YIGSR-NH2 peptide--do not inhibit attachment of nonmotile BAECs to laminin. However, both anti-LB69 and YIGSR-NH2 inhibit late adhesive events such as spreading. Accordingly, we propose that integrin and nonintegrin extracellular matrix-binding protein organizations in BAECs are both temporally and spatially segregated during attachment processes. High affinity nonintegrin interaction with matrix may create necessary stable contacts for longterm attachment, while lower affinity integrins may be important for initial cell adhesion as well as for transient contacts of motile BAECs. [less ▲]

Anti-laminin receptor antibody targeting of liposomes with encapsulated doxorubicin to human breast cancer cells in vitro.

in Journal of the National Cancer Institute (1989), 81(23), 1794-800

The tumor cell laminin receptor is a cell-surface protein that binds laminin with high affinity (Kd = 1.0 nM). The putative ligand-binding domain of the laminin receptor has been molecularly cloned and ... [more ▼]

The tumor cell laminin receptor is a cell-surface protein that binds laminin with high affinity (Kd = 1.0 nM). The putative ligand-binding domain of the laminin receptor has been molecularly cloned and sequenced. In the present study, we used the predicted amino acid sequence of the laminin receptor to generate synthetic peptide antigens and produced immunoglobulin M (IgM) anti-laminin receptor monoclonal antibodies. The disulfide bond group of the IgM molecule was used to couple the antibodies to the surface of liposomes encapsulating doxorubicin. The anti-laminin receptor monoclonal antibodies coupled to the liposomes bound avidly to the surface of MDA-MB-435S (MDA-435) human breast carcinoma cells, which have high numbers of laminin receptors. These antibody-coupled liposomes exhibited a low degree of binding to Hs 578Bst (Hs 578) normal human breast epithelial cells, which express a low number of laminin receptors. Excess liposomes competed for the binding of unbound laminin to the tumor cell surface, and excess laminin competed for binding with the liposomes. Antibody-coupled liposomes encapsulating doxorubicin were specifically more efficient in inhibiting colony formation by MDA-435 cells in vitro than unbound doxorubicin or liposomes without anti-laminin receptor monoclonal antibodies. Unbound doxorubicin inhibited thymidine uptake by 10%-20% in both Hs 578 and MDA-435 cells, whereas the antibody-coupled liposomes encapsulating doxorubicin inhibited thymidine uptake by 90% in MDA-435 cells but only 15% in Hs 578 cells. Thus, use of anti-laminin receptor monoclonal antibodies coupled with liposomes encapsulating doxorubicin represents a new strategy for selective targeting of doxorubicin to carcinoma cells with exposed laminin receptors. [less ▲]

Evidence for a precursor of the high-affinity metastasis-associated murine laminin receptor.

in Biochemistry (1989), 28(18), 7476-86

The high-affinity cellular receptor for the basement membrane component laminin is differentially expressed during tumor invasion and metastasis. A cDNA clone encoding the murine laminin receptor was ... [more ▼]

The high-affinity cellular receptor for the basement membrane component laminin is differentially expressed during tumor invasion and metastasis. A cDNA clone encoding the murine laminin receptor was isolated and identified on the basis of sequence homology to the human laminin receptor [Wewer et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7137-7141]. Primer extension experiments demonstrated that the clone contained the complete 5' sequence of the murine laminin receptor mRNA. RNA blot data demonstrated a single-sized laminin receptor mRNA, approximately 1400 bases long, in human, mouse, and rat. The nascent laminin receptor predicted from the cDNA sequence is 295 amino acids long, with a molecular weight of 33,000, and contains one intradisulfide bridge, a short putative transmembrane domain, and an extracellular carboxy-terminal region which has abundant glutamic acid residues and multiple repeat sequences. The precursor of the laminin receptor is apparently smaller than the 67-kilodalton protein isolated from tissue. The apparent molecular weight on SDS-polyacrylamide gels of the rabbit reticulocyte cell-free translation product of selectively hybridized laminin receptor mRNA is 37,000. Antisera to three different domains of the cDNA-predicted receptor were used to study the relationship between the 37- and 67-kilodalton polypeptides. Antisera to cDNA-deduced synthetic peptides of the receptor immunoprecipitated a 37-kilodalton band both from cell-free translation products and from pulse-labeled cell extracts. On immunoblots of cell extracts, one antisynthetic peptide antiserum recognized only the 67-kilodalton receptor, while another antiserum identified both 37- and 67-kilodalton polypeptides, suggesting a precursor-product relationship between the two polypeptides. [less ▲]