Reconsideration of the laminin receptor 67LR in colorectal cancer cells

Abstract

The 67 kDa laminin receptor (67LR) was identified as the first laminin receptor shown to be involved in the carcinogenesis of various cancers, including colorectal cancer. While the exact composition of this 67 kDa receptor remains unknown, it has been reported to be formed by the 37 kDa ribosomal protein SA (RPSA) covalently attached to another unidentified protein. Our analysis of 67LR in colorectal cancer cell extracts showed the 67 kDa immunoreactive protein corresponding to 67LR in the soluble protein fraction, while some 37 kDa RPSA exhibited plasma membrane-like properties. Proteomic analysis of the 67 kDa fraction revealed the absence of RPSA, however, the β-galactosidase-related 67 kDa elastin-binding protein, another laminin binding receptor, was identified. The downregulation of β-galactosidase through short hairpin RNA (shRNA) led to a reduction in both 67LR and 67EBP immunoreactive proteins, indicating a possible misidentification of 67LR and 67EBP in colorectal cancer cells.