A receptor-binding-based bioassay to determine the potency of a plasmid biopharmaceutical encoding VEGF-C.

Over the last decade biological assays (bioassays) have gained much importance for quality control in biopharmaceutical development and manufacturing. Here we describe the development and validation of a bioassay to determine the biological activity (potency) of the plasmid biopharmaceutical pVGI.1 which encodes the VEGF-C (VEGF-2) protein. This assay was developed to test drug substance and drug product for release and stability testing for phase I and II clinical trials. The main focus was on fast assay development and easy handling of the assay, combined with valid results representing the specific therapeutic mechanism. The method includes the expression of the VEGF-C protein in mammalian cells and its binding to the cell surface receptor VEGFR-3. The binding activity of VEGF-C to its immobilized receptor is quantified in a colorimetric assay. IC50 values of VEGF-C expressed after transfection with sample plasmid and an in-house standard plasmid are determined. The ratio of the IC50 value of the test article to that of the reference standard reflects the potency of the sample. The potency assay meets the criteria generally requested by authorities for precision, linearity, accuracy, and range. Therefore the assay can be used in pharmaceutical quality control and is a suitable basis for development of related bioassays.

Differentiation-dependent expression and mitogenic action of interleukin-6 in human colon carcinoma cells: relevance for tumour progression.

Interleukin (IL)-6 mRNA expression in general is low in normal, adenomatous and cancerous human colon mucosa, except in rather undifferentiated lesions, in which IL-6 is overexpressed. Cytokeratin (CK) 8-positive carcinoma cells were identified by double immunostaining as almost exclusive source of IL-6. Likewise, in five (sub)clones of primary culture COGA-1 and COGA-13 human colon carcinoma cells, and in three established cell lines (Caco-2/AQ, Caco-2/15 and HT-29), efficient translation of IL-6 mRNA into protein was observed only in the least differentiated COGA-13 cells. Notably, IL-1beta (5 ng/ml) enhanced IL-6 release in COGA-13 cultures by three orders of magnitude. Although all cell clones studied expressed the IL-6 receptor (IL-6R), rhIL-6 (1-100 ng/ml) had a significant effect on cellular proliferation only in highly differentiated Caco-2 cells. Our data imply that IL-6, when released from rather undifferentiated carcinoma cells, particularly in response to IL-1beta, can advance tumour progression through paracrine growth stimulation of normal or highly differentiated colon tumour cells with intact STAT-3-mediated IL-6 signalling.