The expression of low density lipoprotein receptor-related protein in colorectal carcinoma

Low density lipoprotein receptor-related protein (LRP) is a multifunctional cell surface receptor binding many different ligands including proteinases and their inhibitors, some of which are known to be involved in tumor biology. We studied the expression of LRP and its putative role in colorectal carcinoma. Tissue samples were obtained from 50 patients with colorectal carcinoma and fixed in formalin and embedded in paraffin. Immunohistochemical staining was performed using antibodies directed against LRP, cathepsin B and urokinase-type plasminogen activator (u-PA). The expression of LRP was further studied by polymerase chain reaction. The TNM stage was determined according to UICC guide lines and was based upon histological analysis. LRP was primarily expressed in stroma cells [36 patients (72%)] and less frequently in tumor cells [6 patients (12%)]. In 22% of all cases LRP was prominent at the invasion front. Cathepsin B was found both in the tumor stroma [50 (100%)] and in the tumor cells [46 (92%)]. u-PA was present in the tumor stroma [44 (88%)] and in the tumor cells [44 (88%)]. In stromal cells the expression of LRP correlated significantly with the expression of u-PA (p=0.043). Furthermore, the expression of LRP and of u-PA in tumor cells correlated with the tumor stage according to UICC (p=0.038 and 0.018, respectively). We provide evidence that LRP is expressed in colorectal cancer. As LRP forms complexes with u-PA and its inhibitor, we suspect that LRP can influence the known effects of u-PA on tumor biology.