Effects of exogenous transglutaminase on spreading of human colorectal carcinoma cells

Using pre-confluent cultures of a human colon tumor cell line deficient in transglutaminase (LS174T cells), we have investigated the effect of adding exogenous transglutaminase (TGA) on cell spreading. The cells were plated at either 4.5 x 10(5) cells per well (low-seeded cultures) or 9 x 10(5) cells per well (high-seeded cultures) in 24-well dishes and treated for either 1 or 4 days (low- and high-seeded cultures respectively) under following conditions: Chee's Essential Medium (CEM) + 10% fetal calf serum (FCS); CEM + 10% FCS + TGA; CEM + 10% FCS + dithiothreitol (DTT) + CaCl2; CEM + 10% FCS + DTT + CaCl2 + TGA. Photomicrography of the cells after these treatments revealed that in both low- and high-seeded cultures, TGA inhibited the spreading of the cells both in the presence and absence of DTT and calcium. Individual colony sizes were significantly smaller in the presence of TGA. This phenomenon may be related to the ability of TGA to promote cell interactions with the underlying tissue matrices and metastasis.