2015 Folate, Vitamin B12 and Inhibitors

Answer to example question 2

The reduced folate carrier (RFC) is a ubiquitous, low affinity, high capacity transporter that transports leucovorin > folate > MTX (D is incorrect).  Reduced RFC expression (not upregulation) is a major cause of primary resistance to MTX (A is incorrect).  The RFC is high capacity, therefore it can’t use potocytosis (B is incorrect).  The folate receptor (not the RFC) is overexpressed in epithelial cancers (ovarian cancer, mesothelioma, choriocarcinoma), making them more sensitive to MTX (E is incorrect).  The folate receptor is more important at physiological concentrations; the RFC at pharmacological concentrations (C is correct).

Email: Dr. Janet Fitzakerley | ©2015 University of Minnesota Medical School Duluth | Last modified: 4-may-15 9:28 PM