An antibody-drug conjugate for endometrioid carcinoma based on the expression of cell adhesion molecule 1

Cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member, is expressed in endometrial glandular cells highly during the proliferative phase but lowly during the secretory phase. Previously, a CADM1-targeting antibody-drug conjugate (ADC) was generated, in which a humanized anti-CADM1 ectodomain antibody h3E1 was linked with monomethyl auristatin E (h3E1-MMAE ADC). The present study aimed at probing whether this ADC could be useful for the treatment of endometrial neoplasm. Firstly, immunohistochemistry for CADM1 was conducted on proliferative-phase endometrium (n = 13), endometrial hyperplasia (n = 35), and endometrioid carcinoma at various stages (n = 166). CADM1 immunostaining intensity was highest in atypical endometrial hyperplasia and endometrioid carcinoma confined within the endometrium and was decreased stepwise as the carcinoma stage progressed. Next, h3E1-MMAE ADC was examined for its cytotoxicity in vitro using human endometrial adenocarcinoma cell lines expressing CADM1; HEC-1B, HEC-50B, JHUM-3, and OMC-2. The ADC killed these cells in a dose-dependent manner with half maximal inhibitory concentration (IC50) of 12.02 nM for HEC-1B and 2.04 nM for HEC-50B. Collectively, h3E1-MMAE ADC may serve as a noninvasive alternative to simple hysterectomy in the treatment of endometrioid carcinoma confined within the endometrium.