Figure 1. Histo-RECAF on breast tumors. Fibroadenoma (negative), 100¥, (a); Ductal carcinoma, 200¥ (b); Lobular carcinoma, 100¥ (c); Axillary lymph node metastasized by a breast carcinoma, 100¥ (d) (click to enlarge). Figure 2. Frozen sections of two different breast ductal carcinomas stained with IVD Technology Magazine IVDT Article Index Originally Published IVD Technology June 2005 Detection Technologies A new broad-spectrum cancer marker A novel receptor protein shows promise for detecting a wide range of malignancies. Ricardo Moro, Janneta Tcherkassova, Elizabeth Song, George Shen, Rafael Moro, Ralph Schmid, Xiaolong Hu, Angela Kummer, and Chen Chen The statistics for cancer survival are sobering: One out of four people will ultimately die from some form of the disease, and of those who contract it, approximately 50% will not recover. In the United States, which represents just 5% of the world’s population, this amounts to half a million deaths every year. The magnitude of this problem makes it easy to understand why so much money and effort is spent on developing new methods to detect cancer at earlier stages, when therapy results in a much higher percentage of cures. Among the diagnostic tools developed during the past few decades, tumor markers provide a combination of low cost and accuracy that makes them suitable for diagnosis, monitoring, and screening. Despite a great deal of research in the area, only a handful of markers have found their way to clinical use. The most notable ones are alpha-fetoprotein (AFP), which appears in primary liver cancer and some rare forms of testicular cancer; carcinoembryonic antigen (CEA), which can help detect colorectal cancer; CA125, for ovarian cancer; and prostate-specific antigen (PSA), which appears in both prostate cancers and benign lesions. This article presents data related to a new cancer marker, named RECAF, which exhibits high sensitivity and specificity on tissue sections and serum of patients with diverse types of malignancies. Background RECAF is a receptor protein that binds and takes up AFP, a circulating fetal protein. RECAF and AFP should not be confused; the latter is a liver and testicular cancer marker known since 1963 whereas RECAF is an emerging broad-spectrum cancer marker. 1 AFP works in the fetus as albumin does in the adult: Both bind and carry other, smaller molecules, including fatty acids. 2 In vitro experiments have shown that after binding to RECAF, AFP penetrates the cell via coated pits, releases its load of fatty acids, and then leaves immunologically intact, likely ready to fetch another fatty acid molecule. 3-5 The uptake of AFP, and hence the expression of RECAF, is related to the degree of cell differentiation: When a given fetal organ or tissue has reached a certain maturity, AFP is no longer taken up even if it is present in high concentrations in the extracellular fluid. 6-8 Since cancer cells are poorly differentiated, it was first postulated and then demonstrated that they reexpress RECAF; hence, RECAF behaves as an oncofetal antigen. 9,10 The AFP uptake by fetal cells occurs in most organs and tissues; therefore,