Application of colony lift assay in the medullary thyroid carcinoma screening of single-chain variable fragment antibody phage library

The aim of the present study was to establish a colony lift assay for medullary thyroid carcinoma (MTC) cells and use it to screen a single-chain variable fragment antibody phage library targeted against MTC. This library was enriched with adsorption-elution-amplification' in several selection rounds (SRs) and was then tested by a colony lift assay and random selection in each SR. The positive clones were scored among assay clones and the proportions that were obtained by each approach were compared. The results showed that positive clones for MTC antigen across one to several SRs accounted, respectively, for 0% (0/96), 3.13% (3/96), 10.42% (10/96) and 58.33% (56/96) in the random pick/selection approach, and 0.63% (2/318), 6.06% (12/198), 12.35% (20/162) and 63.51% (94/148) in the colony lift assay (SR1, (2) = 0.607, P = 0.436; SR2, (2) = 1.151, P = 0.283; SR3, (2) = 0.218, P = 0.640; SR4, (2) = 0.660, P = 0.417). There was no significant difference between the two methods, which suggested that the rates of positive clone selection by colony lift assay were consistent with those of random pick. However, the former method can test many more positive clones simultaneously. Thus, the established new colony lift assay method for panning MTC single-chain variable fragment (scFv) library could be considered effective, simple to manipulate and design, robust and convenient in screening a scFv antibody phage library.