Integrin expression in human melanoma cells with differing invasive and metastatic properties

Abstract

During the process of tumor cell invasion and metastasis, tumor cells are known to interact with extracellular matrix proteins, endothelial cells, platelets and other organ-specific structures. Integrins are cell surface molecules which mediate cell-matrix and cell-cell interactions and are likely to be important for tumor cell survival and dissemination. The purpose of this study was to characterize the integrin and proteolytic enzyme repertoire from low (A375P), medium (A375M) and high metastatic (A375SM) human melanoma cell lines. These cell lines are also invasive through human amniotic membranes in vitro and their invasiveness parallels the reported metastatic phenotype. The types and levels of expression of the various integrin receptors were analysed by quantitative immunoprecipitation using a panel of monoclonal antibodies directed to known integrin subunits. In addition, cDNA probes to the integrin subunits were used in quantitative northern blot analysis. These data show that the integrin alpha v beta 3 increases 50- to 100-fold as these cells progress to a more metastatic phenotype. alpha 4 beta 1 levels also appeared to increase several fold, while other beta 1 integrins did not differ in their expression levels. The increased alpha v beta 3 expression in the more metastatic cells resulted in an increased adhesion to vitronectin and fibrinogen substrates in cell attachment assays. However, alpha v- and beta 3-specific antibodies did not inhibit A375 cell invasion through the amnion. Each cell line was found to release similar quantities of a 72-kDa gelatinase/type IV collagenase and tissue type plasminogen activator. These results suggest that during the progression of these tumor cells from a low to high metastatic phenotype, marked changes in integrin expression occurred which may facilitate interactions with platelets, endothelial cells and specific extracellular matrix proteins to promote metastasis.

Retinoblastoma-binding protein 2-homolog 1: a retinoblastoma-binding protein downregulated in malignant melanomas

“…Considering proliferation rates, however, no correlation to the respective RBP2-H1 expression could be seen for Mel-HO, IGR-1 and COLO-849. However A375-SM cells, which are characterized by a strong metastatic potential, 14 exhibited very low protein expression of RBP2-H1. Therefore, A375-SM could serve as a model cell line for studying functional consequences of RBP2-H1 re-expression in the future.…”

“…As an exception, COLO-894 expressed high RBP2-H1 levels in both RT-PCR and Western blotting. Interestingly, A375-SM cells characterized as strongly metastatic 14 revealed an intermediate RNA expression and a low protein expression.…”

Integrins: roles in cancer development and as treatment targets

“…Notably, integrin avb3 is expressed on invasive melanoma but not benign nevi or normal melanocytes (Gehlsen et al, 1992). Additionally, increased avb3 expression levels correlate with increased rates of melanoma metastases (Nip et al, 1992).…”

The interplay between Src and integrins in normal and tumor biology

“…For example, increased integrin avb3 and a6b4 expression has been associated with increased cell invasion and metastasis in melanoma and breast carcinomas, respectively (Gehlsen et al, 1992;Nip et al, 1992;Mercurio et al, 2001;Ramos et al, 2002). Moreover, alterations in integrin activity have been shown to influence the angiogenic potential of endothelial cells.…”