Role of alphavbeta3 integrin receptor in the invasive potential of human cervical cancer (SiHa) cells.

One of the most important cell surface receptors in tumor development is alphavbeta3. To study the role of the alphavbeta3 integrin receptor in the invasive properties of tumor cells, we used human cervical tumor cells SiHa (cell surface alphavbeta3 integrin receptor-positive) and HeLa cells (cell surface alphavbeta3 integrin receptor-negative). Cell adhesion assay showed that SiHa and HeLa cells can bind very efficiently to extracellular matrix proteins fibronectin, laminin, and collagen IV, but the binding of HeLa cells to vitronectin is very poor compared to that of SiHa cells. Comparative invasion assay demonstrated a much lower invasive potential of HeLa cells than SiHa cells. Cell surface alphav and beta3 integrin receptor subunit assay showed the expression of alphavbeta3 integrin receptor on the SiHa cell surface, whereas the HeLa cell surface lacks functional alphavbeta3 heterodimer. The zymogram demonstrated a higher gelatinase/MMP-2 activity in culture medium, whole cell, and membrane extract of SiHa cells than that in HeLa cells. The alphavbeta3 integrin receptor-associated MMP-2 activity of SiHa and HeLa cells was tested in a comparative zymography that clearly showed very high gelatinase/MMP-2 activity in alphav mAb-immunoprecipitated fraction of SiHa cell (containing alphavbeta3 heterodimer) but not in the alphav mAb-immunoprecipitated fraction of HeLa cell membrane extract (containing only the beta3 subunit). Immunoblot assay of alphav monoclonal antibody-immunoprecipitated alphavbeta3 integrin receptor from SiHa cell membrane extract with MMP-2 monoclonal antibody demonstrated the association of MMP-2 protein with alphavbeta3 integrin receptor. We concluded that alphavbeta3 integrin receptor is one of the most important cell surface molecules regulating the invasive property of cervical tumor cells because of its associated gelatinase/MMP-2 activity. Our findings will contribute to a better understanding of the role of integrin receptors, especially of the alphavbeta3 integrin receptor, in the invasive property of cancer cells and possibly affect future therapeutic approaches to cancer invasion and metastasis.