Figure 9.

Cell surface receptor binding assays of HOSE cells and ovarian cancer cells. A secreted SPARC-AP fusion protein consists of human SPARC and a thermostable human placental alkaline phosphatase (AP) was used to examine the presence of putative SPARC receptors in ovarian cells. As background control, a secretory AP protein produced by the 293T/pAPtag-4 stable cell line was also used in this assay. Cells incubated with culture medium containing SPARC-AP or AP proteins were washed, lysed, and assayed for AP activities. Increase in ligand binding is indicated by the increase in AP activity, which is quantified by measuring absorbance at 405 nm. HOSE1-15 cells showed high levels of binding, whereas the three ovarian cancer cell lines studied have less binding to the SPARC-AP fusion protein.