Growth factor assays

Biotin-hydrazide has been used to biotinylate antibodies at their oxidized carbohydrate residues (O Shanessy et al., 1984, 1987 O Shanessy and Quarles, 1985 Hoffman and O Shannessy, 1988), to modify the low-density lipoprotein (LDL) receptor (Wade et al., 1985), to biotinylate nerve growth factor (NGF) (Rosenberg et al., 1986), and to modify cytosine groups in oligonucleotides to produce probes suitable for hybridization assays (Reisfeld et al., 1987) (Chapter 27, Section 2.3). 

There may be situations which warrant an assessment of carcinogenic potential, but immunogenicity and species specificity may preclude a two-year rodent bioassay. It may be necessary to develop in vitro assays to address a particular concern. For example, growth factors which may have the potential to support or stimulate the growth of transformed cells should be assessed for their ability to promote growth of either malignant or normal cells. 

A competitive assay could also be used for quantitation. In a competitive assay, unlabeled antigen competes for labeled antigen. Examples include ELISAs for vaccine product antigens, such as recombinant proteins from viruses, or nonvaccine antigens such as growth factors or cytokines. 

S. H. Bartelmez and E. R. Stanley, Synergism between hemopoietic growth factors (HGFs) detected by their effects on cells bearing receptors for a lineage specific HGF assay of hemopoietin-1, 7.C eT/./ A/sjo/ 122, 370-378 (1985). 

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