Immunohistochemical Localization of the Mouse Stage - specific Embryonic

Normal human tissues and various human tumors were surveyed by immunohistochemical techniques for expression of the stage-specif ic embryonic antigen 1 (SSEA-1). The ant ibody reacted with many normal and neoplastic human tissues. In most instances, equivalent human and mouse tissues expressed SSEA-1 ; however, dif ferent t issue localization patterns were sometimes seen between these two species. Most SSEA1-positive tumors originate from tissues that normal ly expressed this ant igen; however, some breast and ovarian tumors are SSEA-1 positive, and these organs are SSEA-1 negative. SSEAl -pos i t i ve tumors were composed of both immunoreactive and nonreact ive tumor cells. These data show that SSEA1, initially def ined as a mouse embryonic antigen, represents a heterogenet ic antigen present in many normal human tissues. It is retained on many but not all neoplast ic cells originating in these normal t issues and also appears on the surface of some tumor cells developing in SSEAl -nega t i ve tissues.