Nitrocellulose spot assay of duplicate bacteriophage clones expressing 44 different serologically-defined breast cancer antigens. Following incubation in a 1:200 dilution of serum from a colon cancer patient, the membrane was exposed to alkaline phosphatase-conjugated, Fc fragment-specific, goat anti-human IgG. A positive color reaction with 4-nitro blue tetrazolium chloride/5-bromo-4-chloro-3-indolyl-phosphate indicates seroreactivity with nucleosome assembly protein-1/NY-BR-55, NY-BR-87 and p53/BR-94, as well with the positive control antigen PINCH (PCH)/NY-CO-22.