The IgLON group is an immunoglobulin subfamily of cell adhesion molecules. It comprises OPCML, HNT, LSAMP and NEGR1. OPCML and LSAMP, have been recently identified as putative tumor suppressor genes in epithelial ovarian cancer and clear cell renal cell carcinoma, respectively. To determine whether the IgLON family as a whole has a role in ovarian cancer, we examined its expression profile in human sporadic epithelial ovarian cancer and the normal ovary. To this end, we established the expression level of each IgLON in a well-characterized panel of 11 normal human ovaries and 57 tumors from patients with epithelial ovarian cancer by quantitative real-time RT-PCR. The results were statistically tested for associations with clinicopathological variables. Three out of four IgLONs, namely OPCML, LSAMP and NEGR1, exhibited reduced expression in the tumor samples relative to the normal samples, whereas the expression of HNT was elevated. Statistically significant changes were specific to histological type: OPCML expression was decreased in clear cell carcinomas (p = 0.039), LSAMP expression in endometrioid (p = 0.012), NEGR1 expression in serous (p = 0.014), clear cell (p = 0.009), and endometrioid (p = 0.001), whereas HNT expression was increased in serous tumors (p = 0.008). The expression levels of individual IgLONs were correlated, the most significant finding being a positive correlation between LSAMP and NEGR1 (p < 0.001). LSAMP expression was found to be significantly lower in poorly differentiated tumors in comparison with the rest of the panel (p = 0.017). LSAMP expression was also negatively correlated with overall survival and was found to be a negative predictor of outcome. Overall, we have established that the expression of the IgLON family is altered in sporadic epithelial ovarian tumors in comparison to the normal ovary. We have also found significant correlations and associations in expression and clinicopathology that suggest a wider role of the family in ovarian cancer. This is the first study to link the IgLON family in its entirety with a type of human cancer.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]