FOLH1 and cancer: Examples of ligand tumor-specific molecule binding pairs include small molecules: folic acid (FA) binding to the folic acid receptor overexpressed in breast and many other cancers [17,18], anisamide binding to the sigma receptor overexpressed by tumor-associated fibroblasts [19,20], binding of tetraiodothyroacetic acid to the thyroid hormone receptor in renal cell carcinoma and breast cancer [21,22], and to a ligand of the prostatic specific membrane antigen (PSMA) for prostate cancer [23].