Folate receptor beta is also known as Folate receptor 2, FBP, FOLR2, BETA-HFR, FBP/PL-1, FR-BETA, FR-P3, and is a member of the folate receptor (FOLR) family. and mediate delivery of 5-methyltetrahydrofolate to the interior of cells. This protein has a 68% and 79% sequence homology with the FOLR1 and FOLR3 proteins, respectively. The FOLR2 protein was originally thought to exist only in placenta, but is also detected in spleen, bone marrow, and thymus. FOLR2 is predominantly expressed in placenta, cells of the neutrophilic lineage, and some CD34+ hematopoietic progenitor cells. It is upregulated on myeloid leukemias, head and neck squamous cell carcinomas, and several nonepithelial cancers. It is also upregulated on macrophages and monocytes at chronic inflammatory sites including rheumatoid arthritis synovium and glioblastoma. FOLR2 is a marker for macrophages generated in the presence of M-CSF, but not GM-CSF. Its expression correlates with increased folate uptake ability. Folate conjugates of therapeutic drugs are a potential immunotherapy tool to target tumor-associated macrophages.
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