ATF3 and neoplasm: Hai and colleagues have demonstrated overexpression of the ATF3 protein in a majority of human breast cancers [19], and we have found by immunohistochemistry (IHC) that in about 20% of human breast cancers ATF3 is found to be localized to the nuclei of the tumor cells; in the remaining ATF3-positive breast cancers, expression is primarily seen in stromal elements [21].