Relationship between expression of transglutaminase and anchorage independent growth in differentiation of human salivary gland ductal cells and adenocarcinoma cells

ABSTRACT

Transglutaminase(TGase) catalyzes the Ca2+ dependent acyl transfer reaction to from r-glutamyl lysine cross-links between substrate proteins. We have examined the expression of TGase 1 and TGase 2 enzyme activity and protien expression in differentiation induced salivary gland cells(HSG), and human salivary adenocarcinoma cell lines(SGT) in relation to anchorage independent growth. The TGase 1 and TGase 2 activity in SGT was higher than in HSG, and there is no significant difference between TGase 2 and TGase 1 in SGT cells. HSG cells showed no increase in TGase 1 and TGase 2 upon reaching post confluence and in 1.8mM Ca2+. Expression of the TGase 1 and TGase 2 was induced by high cell density or by high calcium in SGT. No induction of TGase 1 & 2 protein was observed in postconfluent HSG cells, but there was notable increases in TGase 1 & 2 protein in post confluent SGT cells. This pattern of TGase 1 and 2 protein expression correlates with the pattern of particulate activity. SGT cells showed more colony size and colony forming activity in soft agar rather than HSG cells. The ability of SGT cells, containing high levels of TGase 2 and TGase 1, to form colonies in soft agar suggests a role for this enzyme in anchorage independence.