Invasive, metastatic colon cancer arises from pre-existing adenomas in both familial and sporadic cases and is characterized by the presence of multiple chromosomal alterations. In the progression from intramucosal carcinoma to invasive carcinoma, allelic loss on the long arm of chromosome 18 is frequently observed. Recently, a gene on 18q21.3 termed DCC, for deleted in colorectal carcinoma, has been isolated and shown to be deleted or mutated in both sporadic and inherited colon carcinoma whereas normal colonic tissue retained and expressed the gene. Furthermore, loss of DCC expression appears to accompany progression of adenomas to metastatic carcinoma. The inactivation of DCC suggests that it is a tumor suppressor gene. A functional role for DCC as a tumor suppressor gene is indicated by experiments demonstrating that introduction of a normal chromosome 18 into the human colon tumor cell lines COKFu or SW480.7 lacking DCC suppresses tumorigenicity. Analysis of the amino acid sequence deduced from cDNA clones indicates that DCC is a transmembrane glycoprotein consisting of 1447 amino acids with an extracellular domain having extensive similarity to neural cell adhesion molecules (NCAM), a single transmembrane segment, and a unique cytoplasmic domain. The high degree of similarity to NCAMs suggests that DCC is involved in cell-cell interactions essential to the differentiated state of the colonic epithelium. DCC expression has been observed in all tissues examined except liver with the highest level of expression in brain tissue. Alterations in DCC expression have also been observed in pancreatic adenocarcinoma and esophogeal carcinoma. However, DCC mRNA is expressed at very low levels, requiring reverse transcription followed by PCR amplification for unambiguous detection.
DCC; deleted in colorectal carcinoma; netrin receptor DCC; IGDCC1; immunoglobulin superfamily; DCC subclass; member 1; colorectal tumor suppressor; colorectal cancer suppressor; tumor suppressor protein DCC; deleted in colorectal cancer protein; immunoglobulin superfamily DCC subclass member 1; immunoglobulin superfamily, DCC subclass, member 1; CRC18; CRCR1; DCC netrin 1 receptor; zdcc; spo; spaced out; deleted in colorectal cancer