Correlation of mouse S100A7/psoriasin expression using RT-PCR and in situ hydridization in normal mammary gland and DMBA-induced mammary tumors Mouse S100A7/psoriasin mRNA levels were determined in extracts from frozen tissue samples of matched normal mammary gland and DMBA-induced mammary tumors (n = 6) by semi-quantitative RT-PCR as described in Materials and Methods. This evidence concerns the gene S100A7 and breast cancer.