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Stromal-epithelial interactions play a critical role in promoting tumorigenesis and invasion. To obtain detailed information on cancer cell behaviors on the stroma and kinetics of cell migration, which cannot be observed by conventionally-used Boyden chamber assays, this study was aimed at analyzing the cell invasion process in vitro using time-lapse microscopic observation. Serum-free conditions and reconstituted type I collagen gels which provided a basal membrane-stroma-like microenvironment were used to first establish a basal condition. Time-lapse microscopic observation for 30 h of cell invasion into the collagen gel revealed kinetic parameters and individualistic behavior of cancer cells. Of breast cancer MDA-MB-231 or MCF-7 cells and colon cancer LS180 or HT29 cells examined, MDA-MB-231 cells most rapidly disappeared from the collagen gel surface under basal conditions. Estrogen-dependent MCF-7 cells disappeared at a rate approximately two times slower than that of MDA-MB-231 cells under serum- and phenol red-free conditions. By the addition of 10 nM β-estradiol to the basal medium, MCF-7 cell invasion was facilitated to a rate similar to that of MDA-MB-231 cells. Microscopic analyses of collagen gel-sections demonstrated that most of the MDA-MB-231 and MCF-7 cells remained within 60 μm from the gel top under basal conditions, which is consistent with the observation obtained using Boyden chambers that no cells could cross the collagen I gel barrier unless 1% fetal calf serum was added to basal conditions. In summary, this study demonstrated future applicability of this method to understand the initial phase of cancer cell invasion processes.

T-antigen (Galbeta1-3GalNAc-Thr/Ser) also known as Thomsen-Friedenreich (TF) antigen is the core 1 structure of O-linked mucin type glycans. In normal epithelium, the disaccharide structure is masked by terminal carbohydrate moieties, but is uncovered in most primary and metastatic epithelial malignant tumors. For the purpose of establishing cancer diagnosis and therapeutics, anti-T-antigen antibodies were isolated from a phage library displaying human single chain antibodies. A strategy similar to the previously published method (Sakai et al. Biochemistry. 2007; 46:253-262) was used to screen T-antigen specific antibodies, except that a different type of glycolipid was used for panning and screening. Eleven phage clones were isolated and characterized by DNA sequencing and ELISA, which revealed 4 groups of clones with T-antigen binding activity. One single chain antibody (scFv) protein, derived from phage clone 1G11, was expressed in Escherichia coli and purified to near homogeneity by two column chromatographies. ELISA and surface plasmon resonance analyses revealed that the purified 1G11 scFv bound to the T-antigen moiety of the neoglycolipid used. This study not only demonstrated the validity of our previously introduced strategy employing the phage display technology in constructing human scFvs against various carbohydrate antigens, but also provided us with various scFv genes that can lead to future development of antibody-based therapeutics.