Tissue folate binding protein levels in transgenic mice with tumors and in non-transgenic controls

Localized folate deficiency may be a risk factor for cancer. Since, folate binding proteins (FBP) and reduced folate carrier proteins (RFC) mediate cellular transport of folate, we compared FBP concentrations in several organs from tumor-bearing transgenic (TBT) mice and tumor-free non-transgenic controls (NTC) of the same strain, age, and fed identical diets. Liver, spleen, brain, small intestine and kidney were individually homogenized in phosphate-buffered saline (PBS) and separated into membrane, cytoplasmic, mitochondrial/lysomal and nuclear fractions (confirmed with marker enzymes). Homogenates and fractions was analyzed for total protein, and FBP. We used rabbit anti-bovine milk antibody and ELISA to measure FBP. FBP concentrations in kidney, small intestine, and spleen of TBT mice were higher than those of NTC mice; the opposite was true in liver and lung. FBP seemed to be upregulated in kidneys (all fractions), small intestine (all fractions), and spleen (cytoplasmic and nuclear fractions only) of TBT mice compared to NTC mice; the opposite appeared true in liver (all fractions) and lung (all fractions). FBP concentrations in brain, heart, and muscle of TBT mice were not different from those in brain, heart and muscle of NTC mice. A longitudinal study will determine if these changes in FBP concentrations precede tumor onset.