Expression of leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins in human ependymoma relates to tumor location, WHO grade, and patient age.

Three human leucine-rich repeats and immunoglobulin-like domains (LRIG1-3) genes and proteins have recently been characterized. LRIG1 has been shown to be a suppressor of tumor growth by counteracting the signaling of epidermal growth factor receptor (EGFR) family members, including EGFR (ERBB1). Expression of LRIG proteins seems to be of importance in the pathogenesis of astrocytic tumors. In this study, the expression of LRIG1-3 was evaluated in 51 human ependymomas by immunohistochemistry. LRIG proteins were detected in all ependymomas analyzed, however, with a pronounced heterogeneity in expression and subcellular localization. Higher cytoplasmic immunoreactivity of LRIG1 correlated with older patient age and higher LRIG1 nuclear immunoreactivity with lower WHO Grade. LRIG1 displayed a stronger immunoreactivity in the cytoplasm and nuclei in spinal ependymomas than in the posterior fossa or supratentorial ependymomas, while perinuclear LRIG3 was more highly expressed in supratentorial than in infratentorial ependymomas. The indications that expression and subcellular localization of LRIG proteins could be pathogenetically associated with specific clinicopathological features of ependymoma tumors might be of importance in the carcinogeneses and tumor progression of human ependymomas.