Accumulating evidence suggests that integrins, which participate in many complex cellular processes, are important for tumor progression and metastasis. In order to understand the role of these cell-surface receptors and of their ligands in the biological behavior of ovarian tumor cells, we have examined the expression of integrins in the human ovarian-adenocarcinoma cell line IGROV1. These cells expressed the alpha v sub-unit and used it to attach on vitronectin (Vn). A monoclonal antibody (MAb) (69-6-5) specific to alpha v blocked the attachment of IGROV1 cells on Vn and fibrinogen (Fg), but not on fibronectin (FN) and other adhesive ligands. Immunoprecipitation of surface biotinylated cells followed by Western blotting showed that the alpha v sub-unit was associated with beta 3, but not with beta 1, beta 5 or beta 6. When cells were cultivated on glass coverslips or on Vn sub-stratum in serum-free medium, immunofluorescence staining with MAb 69-6-5 revealed the presence of alpha v at cell-cell contacts and at focal contacts, supporting its active participation in adhesion as part of a functional heterodimer. Furthermore, immunofluorescence data showed the presence of Vn as a fibrillar network in IGROV1 cells cultivated on FN-coated slides. These results suggest that alpha v beta 3 and its Vn ligand may play a important role in the behavior of ovarian epithelial tumors.

RNA-polymerase of Escherichia coli was allowed to bind to DNA of phage lambda in the absence of precursors. The resulting complex was excised by nuclease digestion and the protected DNA was recovered by phenol-extraction and ethanol precipitation. Acrylamide gel electrophoresis of protected DNA fragments reveals the existence of two distinct oligonucleotide peaks corresponding, respectively, to 45-52 and 7-10 nucleotide residues along with species of intermediate sizes. Peak I molecules have two properties: (a) their existence is dependent on the presence of sigma factor during the initial binding step, and (b) they are considerably enriched in A-T (up to 67%). On the contrary, peak II molecules have the same base composition as DNA of phage lambda, whether obtained in the presence or absence of sigma factor. Peak I molecules are thus believed to contain DNA sequences involved in promoter recognition, whether they are the promoters themselves, adjacent, or related sequences.

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