Laminin expression in colorectal carcinomas varying in degree of differentiation
G. W. Daneker Jr, A. M. Mercurio, L. Guerra, B. Wolf, R. R. Salem, D. J. Bagli and G. D. Steele Jr
Department of Surgery, New England Deaconess Hospital, Boston, MA 02115.
We are studying the ability of colorectal carcinomas, which vary in degree
of differentiation, to assemble a basement membrane and the relationship
between differences in this ability and perturbations in laminin
expression. For these studies, we are using human colorectal carcinoma
cells grown both in vitro and in nude mice as well as tumors obtained at
surgery. Immunoperoxidase staining of human tumors indicates that laminin
is present in a defined basement membrane in moderately to
well-differentiated tumors. This staining pattern is absent in poorly
differentiated tumors. In these tumors, staining is discontinuous and
sometimes observed intracellularly. The laminin synthesized by in vitro
cells was immunoprecipitated and analyzed by acrylamide electrophoresis.
Neither poorly nor well-differentiated carcinoma cells exhibit marked
differences in the rate of synthesis of laminin. Differences are present in
the rate at which newly synthesized laminin is secreted. These differences
may result from alterations in posttranslational processing. Such
alterations may contribute, along with other factors, to the inability of
poorly differentiated tumors to make a basement membrane.