Laminin M is found in placental basement membranes, but not in basement membranes of neoplastic origin.

Laminin is a high molecular weight glycoprotein found in all basement membranes studied to date. Two subunits of laminin, A and B, have been isolated and characterized from a variety of tumor matrices. Recently we have reported the finding, in human placenta, of a new laminin subunit which we termed M. In the present study we report on the presence of laminin M in placentae of other species such as bovine, rat and mouse. In addition, we have examined laminin extracted from mouse EHS-tumor, rat ED-PYS carcinoma and three human carcinoma cell lines. The laminin subunits were detected by the electroimmunoblot technique using antibodies against mouse, rat and human laminin. Laminin M could not be demonstrated either in the two murine tumors, or in the three different human neoplastic cell lines studied. If the absence of laminin M is the consequence of neoplastic transformation, then studies of the metabolism of this subunit may provide new information on neoplastic transformation and invasion, and a useful marker in tumor diagnosis.