Expression of hyaluronic acid and its receptors, CD44s and CD44v6, in normal, hyperplastic, and neoplastic endometrium

The interaction between epithelial tumor cells and their surrounding stroma is important in tumor progression and metastasis. This is accomplished through a number of transmembrane receptors that interact with stromal extracellular matrix molecules. One of these receptors, CD44, binds to extracellular matrix component hyaluronic acid (HA). The purpose of this study was to evaluate the significance of HA, CD44s, and CD44v6 in benign, hyperplastic, atypical, and malignant endometrial epithelia. Archival paraffin-embedded cell blocks from proliferative endometrium (n = 11), secretory endometrium (n = 12), simple hyperplasia (n = 13), complex hyperplasia without atypia (n = 9), complex hyperplasia with atypia (n = 17), and adenocarcinoma (n = 21) were stained for HA, CD44s, and CD44v6. HA was detected throughout the normal menstrual cycle but was more intense during the secretory phase. Only during the secretory phase was CD44s expressed in the stromal cells in 11 cases (92%), whereas CD44v6 was detected in glandular epithelium in 9 (75%). CD44s was expressed in the glandular epithelium in 2 (15%) cases of simple hyperplasia, 4 (44%) of complex hyperplasia without atypia, 14 (82%) of complex hyperplasia with atypia, and in 16 (76%) of adenocarcinoma. CD44v6 was expressed in the glandular epithelium in 1 (11%) case of complex hyperplasia without atypia, 17 (100%) cases of complex hyperplasia with atypia, and in 18 (86%) cases of adenocarcinoma, but in none of the cases of simple hyperplasia. The endometrial stromal cells expressed CD44v6 in 1 (8%) case of simple hyperplasia, 6 (67%) of complex hyperplasia without atypia, 8 (47%) of complex hyperplasia with atypia, and in 3 (14%) of adenocarcinoma. We concluded that in the normal menstrual cycle, the timing of peak staining of HA and CD44s in the stroma and the up-regulation of CD44v6 in secretory glands are coincident with the period in which the endometrium is most receptive to embryo implantation. HA is more abundant in the stroma adjacent to the tumor, suggesting that interactions between tumor cells and stromal HA promote tumorigenesis. With progression from hyperplasia and with increasing atypia to adenocarcinoma, levels of stromal HA, glandular CD44v6, and glandular and stromal CD44s all increase. Thus, HA and CD44 are both involved in the development and progression of endometrial cancer.