Solute carrier family 45 member 3 (SLC45A3), also known as prostate cancer-associated protein 6 or prostein, is a protein that in humans is encoded by theSLC45A3 gene. SLC45A3 is expressed in a prostate-specific manner by normal tissues and at a significantly lower level in prostate tumor cell lines. Treatment prostate cancer cell lines with androgens upregulates the expression of SLC45A3.