Lamin A and Emerin Protein Expression Remains Consistently Low and Nuclear Size is Unchanged in Normal Endometrium, Precancerous Lesions, and Endometrioid Carcinoma

Nuclear laminar or inner nuclear membrane proteins, including lamin A, B1, and B2 and emerin, are involved in maintaining nuclear morphology. However, their expression patterns vary among tumors and remain incompletely understood. Endometrioid carcinoma (EC) exhibits mild nuclear atypia, although the underlying reasons have not been thoroughly explored. In this study, we quantitatively analyzed emerin and lamin A, B1, and B2 expression levels in normal endometrium (NE), precancerous lesions, and EC using computer-assisted image analysis to assess the proteins' roles in nuclear morphologic change during tumorigenesis. From NE to EC, nuclear size remained unchanged, and lamin A and emerin were consistently expressed at low levels, whereas lamin B1 and B2 expression gradually decreased. Given the association between lamin A and emerin as well as their roles in nuclear morphology, these results indicate that their consistent low expression may underlie the preservation of nuclear size and shape in EC relative to NE. Conversely, lamin B1 and B2 are implicated in tumor progression rather than nuclear morphology maintenance. As lamin A and emerin are expressed in many organs and tumors, the consistently low expression of these proteins from NE to EC highlights a notable feature of the endometrium and endometrial carcinogenesis.