MAPK1 and breast carcinoma: Sivaraman et al (1997) reported an increased enzymatic MAPK activity in cytosols from 12 mammary carcinomas as compared to normal tissues or benign lesions, and Salh et al (1999) found increased ERK1 and ERK2 amounts after immunoprecipitation relative to normal tissue samples, although ERK2 staining intensity in immunohistochemistry was actually reduced in tumour cells.