Cobalamin and folate binding proteins in human tumour tissue.

The serum of an 84 year old man with disseminated carcinoma was found to contain extremely high concentrations of cobalamin and of a cobalamin binding protein with trans-cobalamin I characteristics. Tumour tissue samples obtained at necropsy contained considerably higher concentrations of cobalamin binding protein (R-binder) than normal tissues. Tumour tissues also contained increased concentrations of specific folate binding protein. In all tissues studied a close correlation existed between unsaturated cobalamin and unsaturated folate binding and between total cobalamin and total folate binding. These results suggest related mechanisms for the synthesis of cobalamin binding proteins of the R-binder class and folate binding proteins by tumour tissue.