Recombinant Human ST7/LRP12 Protein, CF

ST7 (Suppressor of Tumorigenicity 7), also known as RAY1, TSG7 and FAM4A1, is a type I transmembrane protein belonging to the LDLR superfamily and is designated LRP12 (1 - 3). The human ST7 cDNA encodes 859 amino acids (aa) including a 32 aa signal sequence, a 460 aa extracellular domain (ECD) containing two CUB domains and five LDLR class A domains, a 21 aa transmembrane domain, and a 346 aa cytoplasmic domain containing motifs implicated in endocytosis and signal transduction (1, 2). Human ST7 shares 95% aa sequence homology with mouse and rat, 96% with canine, and 98% with bovine, equine and porcine ST7 within the ECD. Genomic sequencing indicates the possibility of up to 18 splicing isoforms, but expression of these has not been well‑studied (3). ST7 is widely expressed in normal tissues, especially fibroblasts (1, 4). Highest mRNA levels were detected in heart and skeletal muscle (1). ST7 was originally proposed to be a tumor suppressor protein, but it is not consistently downregulated in a variety of cancers, either by mutation or loss of heterozygosity (1, 4 - 7). In certain cancers, expression may even be upregulated (8). Expression may be associated with downregulated expression of extracellular matrix molecules that are involved in remodeling, such as SPARC, IGFBP5 and several matrix metalloproteinases, and modulation of in vivo tumorigenicity (4, 5).