Do cell adhesion molecules play a role in endometriosis, and can they be used as a biomarker for diagnosing endometriosis?
Altered expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) in the endometrium and peritoneum may play a key role in endometriosis and the soluble VCAM-1/soluble ICAM-1 ratio is a promising biomarker.
Cell adhesion molecules are cell surface proteins that mediate cellular adherence, inflammatory and immune responses, and cancer-related biological processes. Altered expression of VCAM-1 and ICAM-1 in women with endometriosis has been investigated previously; however, gene expression levels in tissues and protein levels in the serum have not been investigated in the same patients.
We performed a prospective, longitudinal study (the Endometriosis Marker Austria) in patients who underwent a laparoscopy for benign gynecological pathology in a university-based tertiary referral center for endometriosis. From a total of 138 women who were included in the study from July 2013 through September 2014, 97 had not received hormonal treatment for at least 3 months prior to recruitment and were included in the analysis; 49 (50.5%) of these women had endometriosis, and the 48 (49.5%) who did not have endometriosis served as a control group.
During laparoscopy, tissue samples were obtained from ectopic and eutopic endometrium, and from normal pelvic peritoneum. In addition, serum samples were collected immediately before and 6-10 weeks after surgery. The mRNA levels of VCAM-1, ICAM-1 and epithelial cell adhesion molecule (EpCAM) were measured using quantitative real-time PCR, and serum protein levels of soluble VCAM-1 (sVCAM-1), ICAM-1 (sICAM-1) and EpCAM (sEpCAM) were measured using ELISA and correlated with endometriosis status.
The mRNA levels of both VCAM-1 and ICAM-1 were higher in ectopic endometriotic lesions than in eutopic endometrium (P < 0.001). Moreover, the mRNA levels of both VCAM-1 and ICAM-1 were higher in normal peritoneum samples obtained from women with endometriosis compared to those from controls (P = 0.038 and P = 0.009). The mRNA levels of VCAM-1 were also higher in the eutopic endometrium samples obtained from women with endometriosis compared to controls (P = 0.018). With respect to serum protein levels, compared to controls, the women with endometriosis had lower serum levels of sICAM-1 (P = 0.042) and higher levels of sVCAM-1 (P < 0.001). Our analysis revealed that the serum levels of sVCAM-1 were not affected by lesion entity, menstrual cycle phase or disease severity. An receiver operating characteristics curve, calculated to determine whether preoperative serum sVCAM-1 concentration can be used to predict endometriosis, found an AUC of 0.868 with 80% specificity and 84% sensitivity at a cutoff value of 370 pg/ml. This predictive performance can be further improved by calculation of the sVCAM-1/sICAM-1 ratio, leading to an AUC of 0.929 with 86.7% specificity and 90.3% sensitivity at a cutoff ratio value of 1.55.
The relatively small sample size in the expression analyses is a possible limitation of this study.
Our findings could contribute to an improved understanding of the pathogenesis of endometriosis and the role of cell adhesion molecules. In addition, the results may lead to the development of new, non-invasive tools for diagnosing endometriosis. The ability to diagnose patients by measuring serum sVCAM-1 levels or the sVCAM-1/sICAM-1 ratio would have considerable clinical value.
The Ingrid Flick Foundation (Grant no. FA751C0801), which played no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. The authors declare no competing interests.