The inability to target MDA-MB-468 tumours is consistent with the results of Adams et al (1998), which demonstrated that effective targeting and retention of anti-ErbB2 scFv antibodies to SK-OV-3 tumours, a tumour line that expresses 1 × 106 copies of ErbB2 per cell, require a threshold affinity of 1 × 10−8 M. This evidence concerns the gene ERBB2 and neoplasm.