Therapeutic antibodies are the fastest growing class of drugs in the treatment of cancer, and autoimmune and inflammatory diseases that require the concomitant development of assays to monitor therapeutic antibody levels. Here, we demonstrate that the use of Affimer nonantibody binding proteins provides an advantage over current antibody-based detection systems. For four therapeutic antibodies, we used phage display to isolate highly specific anti-idiotypic Affimer reagents, which selectively bind to the therapeutic antibody idiotype. For each antibody target the calibration curves met US Food and Drug Administration criteria and the dynamic range compared favorably with commercially available reagents. Affimer proteins therefore represent promising anti-idiotypic reagents that are simple to select and manufacture, and that offer the sensitivity, specificity and consistency required for pharmacokinetic assays.

This study investigates the mechanisms involved in the regulatory volume decrease (RVD) in ZR-75-1 epithelial-derived human breast cancer cells. Cell volume changes were measured during osmotic shock using video imaging. In HEPES-buffered hypotonic solutions no RVD was observed; however, RVD was observed in HCO(3)(-)-buffered hypotonic solutions. Inhibition of RVD by 10 microM tamoxifen and 100 microM DIDS (inhibitors of volume-regulated anion channels; VRAC) and 2 mM TEA(+) (inhibitor of K(+) channels) indicates a role for these channels. In HCO(3)(-)-buffered Cl(-)-free solutions RVD was partially abolished indicating that HCO(3)(-) efflux can support RVD but also may have another role. Further experiments investigated whether HCO(3)(-) assists in the accumulation of Cl(-) via Cl(-)-HCO(3)(-) exchange. Regulatory volume increase (RVI) was also HCO(3)(-)-dependent and was inhibited by 500 microM DIDS and 10 microM 5-( N, N-dimethyl)-amiloride (DMA) indicating a role for coupled Cl(-)-HCO(3)(-) and Na(+)-H(+) exchange. Finally, in the presence of 10 microM DMA, RVD was partially inhibited providing further evidence for a role of Cl(-)-HCO(3)(-) exchange. Thus RVD in ZR-75-1 cells involves the activation of VRAC and K(+) channels. RVD is HCO(3)(-)-dependent and HCO(3)(-) efflux through VRAC appears to contribute directly to RVD. HCO(3)(-), however, also has another role in facilitating Cl(-) accumulation via Cl(-)-HCO(3)(-) exchange.

No abstract

No abstract

No abstract