The KLK5 expression of the benign tissue specimens ranged between 0.035-1380.4×103 KLK5 mRNA copies/103 HPRT1 mRNA copies (c/Kc), while the expression in the tissue specimens obtained by the breast cancer patients varied between 0.035-19.6x103 c/Kc. This evidence concerns the gene HPRT1 and breast cancer.