Compared with the estradiol-injected mice, the plasma PRL levels of peripheral blood (Fig. 2a, P < 0.01) and PRL mRNA expression levels in the pituitary gland (Fig. 2b, P < 0.05) were decreased, and the tumor/body weight ratio (Fig. 2c, P < 0.001) was significantly decreased in the estradiol-injected MAPK14−/− mice. This evidence concerns the gene MAPK14 and neoplasm.